Solid Rocket Thrust Vector Contro Nasa Lsp8114
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FOREWORD
NASA experience has indicated a need Accordingly, criteria are being developed
for uniform criteria for the design of space in the following areas of technology:
vehicles.
Environment Structures
Individual components are completed. This
of this document,
Guidance
and Control
Chemical
Propulsion
work will be issued as separate monographs as soon as they part of the series on Chemical Propulsion, is one such
monograph. A list of all monographs of this document. These except
monographs as may be
these
documents,
unifqrm This
design
of Howard management
are to be regarded specified in formal revised
practices
monograph,
issued
"Solid
Rocket
W. Douglass, Chief, was by M. Murray
to this one
can be found
on the
as guides to design and not as NASA project specifications. It is expected,
as experience for NASA
prior
may
space
indicate
to be desirable,
final
pages
requirements, however, that
eventually
will provide
vehicles.
Thrust
Vector
Design Bailey.
Control,"
Criteria Office, The monograph
was prepared Lewis was
under
the direction
Research Center; written by Robert
project F. H.
Woodberry and Richard J. Zeamer of Hercules, Inc., and was edited by Russell B. Keller, Jr. of Lewis. To assure technical accuracy of this document, scientists and engineers throughout the technical community participated in interviews, consultations, and critical review of the text.
In
particular,
Thomas
S. Clark
Aircraft Corporation; Lionel H. Erickson of Aerojet Solid Propulsion Company; Center reviewed the monograph in detail. Comments National Office), December
concerning Aeronautics Cleveland, 1974
Ohio
the and
of
United
of Thiokol and James
Technology Chemical J. Pelouch,
Center,
Corporation;Myron Jr. of the Lewis
technical content of this monograph Space Administration, Lewis Research
44135.
Division
will be welcomed Center (Design
of United Morgan Research
by the Criteria
For sale by the National Technical Springfield, Virginia 22161 Price - $7.00
Information
Service
GUIDE
The
purpose
significant programs
of this
is to organize
and
present,
accumulated current design
for effective
that
The
the
of which
are
Art,
design
preceded
by
section
2,
elements
a brief
reviews
introduction
and
are involved
discusses
in successful
use
in design,
the
in development and operational practices, and from them establishes
for achieving greater consistency in design, increased greater efficiency in the design effort. The monograph
major sections references. State
monograph
experience and knowledge to date. It reviews and assesses
firm guidance product, and
identifies
TO THE USE OF THIS MONOGRAPH
reliability is organized
and
complemented
the
total
design.
current technology pertaining to these elements. When detailed best available references are cited. This section serves as a survey background material and prepares a proper technological base Recommended Practices.
design
It describes
in the end into two by
a set
of
problem,
and
succinctly
the
information is required, the of the subject that provides for the Design Criteria and
The Design Criteria, shown in italics in section 3, state clearly and briefly wha.._.__t rule, guide, limitation, or standard must be imposed on each essential_ design element to assure successful design. The Design Criteria can serve effectively as a checklist of rules for the project manager to use in guiding a design or in assessing its adequacy. The
Recommended
Whenever appropriate
Practices,
also
in section
3, state
Design Criteria, successful design.
provide
positive
guidance
to
Both sections have been organized into decimally within similarly numbered subsections correspond the Contents displays design can be followed The design specifications,
how
to satisfy
each
of the
possible, the best procedure is described; when this cannot be done references are provided. The Recommended Practices, in conjunction
this continuity through both
criteria monograph or a design manual.
loosely organized its merit should to the designer.
body of existing be judged on how
the
practicing
designer
on
how
that
a particular
is not intended to be a design handbook, It is a summary and a systematic ordering of the
nl
to achieve
numbered subsections so that the subjects from section to section. The format for
of subject in such a way sections as a discrete subject.
successful effectively
criteria.
concisely, with the
design techniques and it makes that material
practices. available
aspect
of
a set of large and
Its value and to and useful
CONTENTS
Page
.
INTRODUCTION
2.
STATE
3.
DESIGN
1
............................
OF THE
ART
CRITERIA
and Recommended
Practices
Units to SI Units
APPENDIX
A - Conversion
of U. S. Customary
APPENDIX
B - Glossary
............................
REFERENCES NASA
3
........................ ................
161
............
163 173
................................
Space Vehicle
Design
Criteria
Monographs
Issued
to Date
STATE
SUBJECT
185
.............
OF THE
ART
DESIGN
CRITERIA
2.1
18
3.1
117
Configuration Design Optimization Envelope Limitations
2.1.1 2.1.1.1 2.1.1.2
18 21 22
3.1.1 3.1.1.1 3.1.1.2
117 117 118
Design Requirements Actuation Torque
2.1.2 2.1.2.1
22 23
3.1.2 _1.2.1
119
2.1.2.1.1 2.1.2.1.2 2.1.2.1.3
24 26 27
_1.2.1.1 3.1.2.1.2 3.1.2.1.3
2.1.2.1.4 2.1.2.1.5
29 29
3.1.2.1.4 3.1.2.1.5
120 120 121
2.1.2.1.6 2.1.2.1.7
29 30
3.1.2.1.6 3.1.2.1.7
121 121
2.1.2.1.8 2.1.2.2
30 31
3.1.2.1.8 _1.2.2
122 122
2.1.2.3 2.1.2.3.1
33 35
_1.2.3 3.1.2.._1
123 123
2.1.2.4 2.1.2.5 2.1.2.5.1
36 37 37
3.1.2.4 _1.2.5 _1.2.5.1
124 125 125
2.1.2.5.2 2.1.2.6
39 40
_1.2.5.2 3.1.2.6
125
FLEXIBLE
JOINT
Joint Spring Torque Friction Torque Offset Torque Inertial Torque Gravitational Torque Insulating-Boot Torque Internal Aerodynamic Torque External Aerodynamic Torque Nozzle Vector Angle Axial Deflection Nozzle
and Pivot
Misalignment
Frequency Response Environmental Protection Thermal Protection Aging Pressure
Protection Sealing
Point
119 119 120
126
SUBJECT
Material
STATE OF THE ART
Selection
Elastomers Reinforcements Adhesive Bond System Joint Thermal Protection Mechanical General
Design Considerations
Design Definitions Design Safety Factor Flexible-Joint Loads Structural Analysis Elastomer Thickness Reinforcement Thickness Advanced
Analysis
Manufacture Reinforcements Joint Adhesive Flexible Joint
System
Testing Subscale Test Program Bench Test Program Static-Firing Destructive Aging
Program
Inspection Inspection Inspection LIQUID
Plan Processes
INJECTION
CONTROL
Program Testing
THRUST
CRITERIA
2.1.3
40
3.1.3
126
2.1.3.1
41
3.1.3.1
126
2.1.3.2 2.1.3.3 2.1.3.4
42 44 44
3.1.3.2 3.1,3.3 3.1.3.4
129 129 130
2.1.4
45
3.1.4
130
2.1.4.1 2.1.4.1.1 2.1.4.2
45 46 47
3.1.4.1
130
3.1.4.2
131
2.1.4.3
47
3.1.4.3
131
2.1.5
48
3.1.5
132
2.1.5.1 2.1.5.2 2.1.5.3
48 51 54
3.1.5.1 3.1.5.2 3.1.5.3
132 133 133
2.1.6
55
3.1.6
134
2.1.6.1 2.1.6.2 2.1.6.3
55 58 59
3.1.6.1 3.1.6.2 3.1.6.3
134 135 135
2.1.7
62
2.1.7.1 2.1.7.2 2.1.7.3
62 64 67
3.1.7 3.1.7.1
136 136
3.1.7.2 3.1.7.3
137 139
2.1.7.4 2.1.7.5
68 68
3.1.7.4 3.1.7.5
139 140
2.1.8
68
3.1.8
140
2.1.8.1
69
3.1.8.1
140
2.1.8.2
69
3.1.8.2
141
2.2
70
3.2
t42
2.2.1
74
3.2.1
142
2.2.1.1 2.2.1.2
78 79
3.2.1.1 3.2.1.2
142 144
3.2.1.3
146
3.2.1.4 3.2.1.5 3.2.1.6
147 148 150
VECTOR
(LITVC)
System
DESIGN
Design
System Optimization Selection of Injectant Injection Pressures and Injection Orifices Injector Amount
Location and Discharge Angle of Liquid Injectant Required
2.2.1.3 2.2.1.4 2.2.1.5
81 86 87
Amount
of Pressurization
2.2.1.6
89
Gas Required
vi
SUBJECT
STATE
Component Design Injectors Storage Tank and Bladder
OF THE ART
DESIGN
CRITERIA
2.2.2 2.2.2.1
89 90
3.2.2 3.2.2.1
151 152
2.2.2.2 2.2.2.3 2.2.2.4
95 97 99
3.2.2.2 3.2.2.3 3.2.2.4
153 154 155
2.2.2.5
99
3.2.2.5
155
2.2.2.6
99
3.2.2.6
157
Performance Evaluation and Testing Performance Data for Design Small-Scale Tests
2.2.3 2.2.3.1 2.2.3.2
103 104 115
3.2.3 3.2.3.1
158 158
Full-Scale Development Tests Operating-Capability Tests
2.2.3.3 2.2.3.4
115 115
3.2.3.2 3.2.3.3
159 160
3.2.3.4
160
Pressurization System Liquid Storage Equalization Disposal of Surplus Injectant Adaptation of the Motor for LITVC
vii
LIST OF FIGURES
Title
Figure 1
Classification
2
Gimbal/swivel
3
Gimbal/integral
4
Supersonic-splitline
5
Ball-and-socket
6
Rotatable
7
Flexible-joint
8
Fluid-bearing/roiling-seal
9
Liquid
10
Hot-gas
11
Jet tab TVC systems
12
Flexible
of thrust
control
subsonic-splitline
nozzle
nozzle nozzle
canted
injection
joint
...................
14
Graphical
15
Effect
16
Movement
17
Effect
18
Shear-stress
19
Buckling stress and dimensions
joint
12
......................
14
.......................
15
.....................
15
...........................
16
position
......................
position
location point
related
for metal reinforcements of the reinforcement test specimen
in a flexible-joint
envelope
different
(due to motor factors
20
of friction
on required
for three
19
.....................
of the effects
of axial deflection
shear
11 12
leg mounted
presentation
correction
11
13
nozzle
in vectored
of pivot
.................
...........................
TVC system
of pivot-point
nozzle
11
.........................
in neutral
Flexible
4
........................
nozzle
TVC system,
.................
..........................
nozzle
Quadruple-lap
systems
low-subsonic-splitline
13
20
vector
Page
as a function ....................
ix
28 31
nozzles
on nozzle
to cone angle
.....................
......
...............
flexible-joint
pressure)
nozzle
alignment
...............
.........
34 .......
36 49
of the properties 53 63
Figure
Title
Page
21
Specialfixturefor testingjoint axialdeflection ................
65
22
Fixturefor testingjoint actuationunderpressure................
66
23
Schematic of typicalliquidinjectionTVCsystemandsideforcephenomena .....
71
24
Nozzlepressure distributiondueto injectionof inertinjectant
72
25
Nozzlepressure distributiondueto injectionof reactive injectant
73
26
Basicdesignfeatures in a LITVCsystem ...................
75
27
Schematic of TitanIII ullageblowdownLITVCsystem .............
76
28
LITVCsystem for PolarisA3 secondstage
77
29
Crosssectiondrawingof typicalsingle-orifice injector mountedonnozzlewall .........................
84
..........
3O
Crosssectiondrawingof three-orifice injectormountedonnozzlewall
31
CrosssectiondrawingOfanelectromechanical injectantvalve ............
85
32
Injectorvalveassembly withhydraulic-powered actuator
91
33
Servo-controlled hydraulicpowersystems forvariable-orifice injectors .......
92
34
Erosionaroundinjectorportsin theTitanIII nozzle ..............
101
35
Comparison of small-scale andfull-scale dataoninjectantspecific impulsevsdeflectionangleandsideforce ...................
105
.......
84
36
Comparison of performance of inertandreactive injectants ............
106
37
Effectsofinjectionlocationandangleoninjectantspecificimpulse .......
107
38
Effectof injectantflowrateandinjectionpressure onsideforce ..........
39
Effectof injectionlocationandorientationonsideforcefor differentinjectantflowrates ........................
109
40
Transformation of dataoninjectionpressure vsinjectantspecificimpulse ......
110
41
Effectofnumberof annularorificesonsideforceasa functionof injectantflowrate
111
x
108
Figure
Title
42
Transformation of performance
data
43
Correlation
impulse
44
TWo examples
of acceptable
45
Two
of unacceptable
46
of injectant
examples
Sketch illustrating of effective pivot
47
Recommended
48
Values
49
Relation
50
Typical
for strontium
perchlorate
with key nozzle
unbonded-elastomer unbonded-elastomer
sequence
of thrust
of steps impulse
deflection
port
for determining
for reactive angle
configuration
showing
xi
112
........
114 127
..........
128
determination 138 the optimum liquid
location erosion
.......
...........
conditions
and inert
to injector
injectant
parameters
conditions
factors involved in experimental point ..........................
of side specific
LITVC
specific
Page
LITVC
injectants
system ........
.............
and char patterns
design
143 145 149
........
158
LIST OF TABLES
Table
Title
Page
I
Advantages,
Disadvantages,
and Current Status of Movable Nozzle Systems
II
Advantages,
Disadvantages,
and Current Status of Secondary
III
Advantages,
Disadvantages,
and Current Status of Mechanical
IV
Advantages,
Disadvantages,
and Current Status of Special Systems
V VI VII
VIII IX X
XI XlI XIII
Integral Values 103) for/3 = 15 ° to 13= 60 ° Comparative
Effects of Forward
Details of Reinforcements and Development Motors Advantages
Compatibility and Aqueous
........
of Joint Fabrication
Pivot Point
Processes
of Main Operational
Chief Design Features of Variable-Orifice
°°°
9
32
56 ..........
Liquid Injectants
60 .....
80
114-B2 82
of Liquid Storage Systems on Operational
Xlll
8
10
.........
Injectors on Operational
for Inert and Reactive Injectants
6
25
of Selected Metals and Nonmetals with Freon Strontium Perchlorate ....................
Side Force Composition
Systems
..................
and Aft Geometric
and Characteristics
Chief Design Features
Deflector
Systems
Used in Flexible Joints on Operational ........................
and Disadvantages
Basic Properties
Injection
.....
LITVC Systems LITVC Systems
............
93 96 103
ROCKET
SOLID THRUST
VECTOR
CONTROL
1. INTRODUCTION Most the
vehicles required
used flight
for launching trajectory
spacecraft
require
will be achieved.
for flight disturbances (e.g., thrust and center of gravity).
winds) and To provide
equipped with a thrust vector control have been used to redirect the motor
some
guidance
In addition,
or steering
steering
to ensure
is needed
that
to compensate
for vehicle imperfections (e.g., misalignment this steering, solid propellant rocket vehicles
system. thrust
Both mechanical and provide the
and aerodynamic required steering
of are
techniques forces. This
monograph is limited to treatment of thrust vector control systems that superimpose a side force on the motor thrust, steering being achieved by the side force causing a moment about the vehicle center of gravity. A brief review of thrust vector control systems is presented, and two systems, flexible joint and liquid injection, are treated were selected because they are in use on a number of operational likely to be used in future depends upon the particular reliability, development system different from within the restrictions presented
to allow
Treatment
of the
flexible
joint
and
These two systems and they are most
vehicles. The choice between these two systems performance requirements, system weights, cost,
risk, and envelope constraints. However, it i_ possible that a control the selected systems could result in an optimum vehicle performance imposed for particular types of missions. Sufficient references are
investigation flexible-joint its
aerospace vehicle
in detail. vehicles
in detail thrust
insulation
of control vector
against
hot
systems
control motor
other
system gases;
no
than
the
is limited
two
to the
evaluation
the injectant distribution The
design
and within
erosion at the the nozzle.
technology
for
the
injection
two
selected
port
injectant, of the and
systems
design
is presented
movable nozzle, the actuation system, or the means for attachment of the the movable nozzle and the fixed structure. Treatment of the liquid-injection control system is limited to discussion of the pressurization system; no evaluation is presented
selected. of the of the
flexible joint to thrust vector
valves, piping, storage tanks, and nozzle except for (1) the effect of
(2)
the
effect
has
progressed
of injection
to the
point
on
pressure
where
the
basic problems have been overcome and efficient and reliable systems can be designed for any required use. Design problems with flexible joints have been associated with difficulty in establishing the envelope for the movable nozzle; definition of the actuator power
requirements to vector the movable nozzle; definition of allowable properties for the elastomerand the reinforcement; adhesivebonding of the elastomerto the reinforcements; test methodsthat adequatelysimulate the motor operating conditions; and quality control inspection of the molded joint. Design problems in liquid injection systemshave been associatedwith definition of the maximum steering-forceduty cycle; determination of the optimum location and geometry of the injector Valves;andincompatibility of the injectant with many of the materials used for the nozzle walls, seals,and injectant pressurization system. Emphasis in the monograph is placed on those areaswhere specific technical approacheshavesolveddesignanddevelopmentproblems. The material herein is organized around the major tasks in thrust vector control: configuration as related to motor requirements;designparameterscontrolling the response of the mechanism; material selection; system design; structural and thermal analysis; manufacturing; testing, both nondestructiveanddestructive;and inspection.Thesetasksare consideredin the order and manner in which the designermust handle them. Within these task areas, the critical aspects of the performance, structural, thermal, and physical boundary requirementsthat the thrust vector control systemmust satisfy arepresented.
2. STATE OF THE ART
The
vehicle
flight-control
system
must
perform
two
functions:
fly
the
vehicle
along
a
commanded trajectory, and maintain vehicle flight stability in the atmosphere. Vehicles without aerodynamic stabilizing fins normally are unstable, and those with fins may be only marginally stable. Disturbances that effect vehicle attitude and stability include atmospheric winds; motor thrust misalignments due to fabrication tolerances and thrust-vectorcontrol-system offsets such of gravity; and unbalanced disturbances requirements,
be
corrected structural
as those forces with loads,
that occur with flexible joints; during launch and staging. It proper and
timing and aerodynamic
requirements are a function of interrrelated and the vehicle aerodynamic and structural requirements and the design of the control the development of a space vehicle system.
amplitude heating
shifts of vehicle center is desirable that these
so are
that control minimized.
energy Control
effects of disturbances, the trajectory required, dynamics. The determination of flight-control system are two of the most complex problems in
The control system causes a side force to be applied to the vehicle at some distance from the vehicle center of gravity, resulting in a control moment and a change in the vehicle attiude. A number
of force-producing
mechanisms
have
been
employed
or considered
as means
provide attitude and trajectory control of aerospace vehicles. The available considered in this monograph are divided into two main groups: movable-nozzle and fixed-nozzle systems. A classification of the different force-producing associated used, and
with movable and fixed nozzles is shown still others have been evaluated to determine
used include aerodynamic movable 15), and
jet reaction fins (refs.
pintles electric
(refs. 1 to 6), movable external rocket 10 and 1 1). Preliminary evaluations
(refs. 1, 12, 13, and 14), movable arc discharge (ref. 16).
The correct definition and design of the requiring tradeoff analyses between control system as they relate to vehicle performance. vector
control
response, and the systems;
system
are
the
control
plug
(ref.
systems systems, systems have have
motors (refs. 7 to 9), have been conducted 2),
electro
gas dynamic
been been and on (ref.
flight-control system is a complex problem requirements and the penalties of the control Factors affecting the selection of a thrust
moment
required,
the
characteristics
of
vehicle
the stability requirements during flight, reliability requirements, cost restrictions, behavior of the candidate systems. Movable-nozzle systems are linear response i.e., the turning moment is almost directly proportional to the amount of nozzle
vectoring, although directly proportional. rate
in figure 1. Other sytems feasibility. Systems that
to
of injectant
the power required to cause that amount of nozzle vectoring may not be Fixed-nozzle systems generally are nonlinear systems; i.e., twice the
flow
in a liquid
injection
system
does
not
cause
twice
the turning
moment.
TVC
Fixed
J
' Liquid
i
Mechanical
Special systems
deflectors
__J
I
Gas injection
--Jet
I Movable
I
injection l
injection
I
I nozzle i
I Secondary
systems
nozzle
!
I
Low subsonic
High subsonic
_A
I Supersonic
--_Flexible
vane
_____J
-_mbal
joint i
--Flexible --Rotatable
Movable
-Jetevator
L--Hinged
joint --Fluid
bearing/
rolling _Inert liquid
i
I
Warm
gas
--Jet
Pintle --Gimbal
L--Movable
tab
--Fluid
bearing/
plug rolling _Reactive liquid
.-Hot
"Jet
seal
probe --Hinged
--Gimbal
gas _Segmented nozzle
--Ball
&
socket
--Hinged
Figure
1. - Classification
of
thrust
vector
control
systems.
seal
Thrust in the
vector control mechanisms past have been outmoded
have been undergoinging continual by increased severity of operational
development of lighter, more reliable status of the systems listed in figure features of major systems are shown
systems. The general characteristics and technology 1 are presented in tables I through IV; basic design in figures 2 through 11. The systems summarized in
tables I to IV can be divided into three categories: (1) systems systems that have been tested in static firings, and (3) experimental been abandoned or require significant development. Movable rotatable
nozzles.The movable-nozzle systems nozzle and flexible joint) or have been
splitline,
gimbal/integral
change. Concepts used requirements and by
low-subsonic
splitline,
that are systems
(table I) either static fired (e.g.,
supersonic
splitline,
would cause of the vehicle
(2) have
are operational (e.g., gimbal/swivel subsonic and
ball and
of the systems have demonstrated problems or limitations. All movable require that the actuation hardware for the staging maneuvers be carried remainder of the flight. The rotatable nozzle is limited to multinozzle movement of only one nozzle vehicle; effective maneuvering
operational, that either
socket).
All
nozzle systems throughout the motors because
pitch, yaw, and roll forces to be applied to the requires movement of at least two nozzles. The
supersonic splitline and ball-and-socket type are not developed systems, and it is unlikely that further development will be conducted since the other movable nozzle systems have demonstrated all the advantages of these nozzles but with fewer operational and design problems. The
fluid
fluid-filled deflection
bearing/rolling
seal
bearing configured of the rocket motor
deflected as both
(designated
as
TECHROLL
®)
is
a
constant-volume,
with a pair of rolling convolutes that permit omniaxis nozzle. The bearing is shown in figure 8 in the neutral and
positions. The fluid-filled bearing is pressurized by nozzle ejection loads the movable nozzle bearing and nozzle seal. The seal is fabricated
fabric-reinforced
elastomeric
composite
manufacturing processes or tight tolerances. that the actuation torques are lower than
material The those
that
does
not
and serves from a
require
complex
most significant advantage of this bearing is of any other thrust vector control system.
The most significant disadvantages of the bearing are that it has a low rotational stiffness about the nozzle axis in the unpressurized condition, the pivot-point location is limited, and the low lateral stiffness results in larger offset torques than those occurring with a flexible joint.
The
rotational
stiffness
is important
for upper
stages
only
when
vibrational
problems
could occur during lower-stage motor operation. To overcome the limits on pivot-point location, it has been proposed that the rolling convolutes be oriented on a cone; however, this design will increase the actuation torque. The larger offset torque must be allowed for when defining nozzle vectoring angle has been bench tested and static fired joint (ref. 35), thus allowing a direct ®Trademark
of United
* Parenthetical conversion monograph.
units
factors
Technologies
here
and elsewhere
appears
in Appendix
(formerly in the A.
For
requirements. A 24-in. (60.96 cm)*-diameter bearing in a large rocket motor that normally uses a flexible performance comparison of the two systems. The
United
Aircraft
monograph simplicity
Corporation).
are in the International and
brevity,
SI units
System are
not
of Units presented
(SI units). in the
A table
tables
of
in the
TABLE I. - Advantages, Disndvantal|es, and Current Status of Movable Nozzle System
System
Advantages
Flexible joint (refs. 17-30)
State of the art Flexible duty cycle
(fig. 7)
No splitlines Large deflection capability Flexible pivot point location Negligible thrust loss Minimum seal problem Can be used for deeply submerged nozzle Fast response capability Lightweight
Status of Technology
Disadvantages
Operational system for Poseidon C3 first and second stage.
Joint requires thermal protection Joint requires vrotection
of
elastomer during storage Only small tension loads can be applied to joint Joint pivot point is floating, dependent on motor pressure and vector angle Nozzle aligned only at one design pressure and misaligned at all other
(refs. 31 and 32) (fig. 6)
System static fired to 15° vector angle at 355 deg/sec and 300 psi. One static firing, 13-in. and 34-in. throat, submerged nozzles. Three static firings, 2.3-in., 2.6-in., and 8 in. throat. angle at 428 deg/sec and 300 psi.
State of the art
Limited to multiport
Flexible duty cycle Low bearing loadings
Large bearing required Movement of a nozzle results
motors
Operational system for Polaris A2 second stage and Polaris A3 first stage.
in pitch, yaw, and roll forces Nozzle rotation angle much larger than jet deflection
Fluid bearing/
State of the art
Bearing requires thermal
rolling seal
Flexible duty cycle
(refs. 33-36)
No splitlines Large deflection capability
protection Low rotational
(fig.8)
Army Re-entry Measurements Program Phase B; throat diameter approximately 2.8 in., + 8 ° deflection.
System bench tested to 15° vector
pressures
Rotatable nozzle
Twelve successful flight tests on
Negligible thrust loss Minimum seal problem Can be used for deeply submerged or supersonic splitline nozzles Fast response capability Lightweight Minimum envelope required
angle
stiffness about
nozzle axis in unpressurized condition Bearing pivot point is floating, dependent on motor pressure and vector angle
Flightweight systems for Trident 1 (C4) first-, second-, and third-stage motors demonstrated in static firings. Static firings, 4-in. and 10-in. throat, submerged nozzles. Two static firings, 2.44n. and 8.5-in. throat.
Nozzle aligned only at one design pressure and misaligned at all other pressures
Low spring torque (continUed)
/
TABLE I. - Advantages, Dissdvantalles , sad Currant Status of Menmble Noz_
System
Gimbal/swivel subsonic splitline (refs. 37 and 38) (fig. 2)
Advantages
Disadvantages
State of the art Flexible duty cycle Negligible thrust loss Large deflection capability Low-to-medium blowout load Low entry erosion
Excessive envelope required for submerged nozzle High erosion and heat flux in splitline Limited operation time Inflexible pivot-point locations
Systems (oaududed)
Status of Tedmology
Operational system for Minuteman i and 1I first and third stages and Minuteman 111 tint stage. One fullscale firing, 38-in. throat, single external-gimbal nozzle. Two subsonic firings, 15-in. throat, single external-glmbal nozzle. One firing, 4.71 -in. throat, single externalglmbal nozzle.
Gimbal/integral low subsonic splitline (refs. 37-40)
(t_g.3)
State of the art
High blowout
Minimum splitline erosion and heat flux
High actuation torque Large volume required within chamber
Minimum seal problem Continuity of entry, throat, and exit cone Flexible duty cycle Negligible thrust loss Large deflection capability Long burn time durability
load
Medium entry erosion Inflexible pivot-point location Potentially large vectoring envelopes
One firing, 24-in. throat, single submerged nozzle. Two firings, i 5-in. throat, nozzle.
single submerged
One firing, 9.2-in. throat, single submerged nozzle. One firing, 3.9-in. throat, single submerged nozzle. Two f'uings, 1.75-in. throat, single submerged nozzle" +-14 °, 235 sec operation, 163 sec actual firing, 20 pulses, 72 sec coast time.
Supersonic splitline (refs. 41-44) (fig. 4)
Attractive for submerged nozzle
Sealing and erosion problems at splitline
Low entry erosion Lightweight potential Fast response capability Low blowout load
High actuation torque Limited to small vector angles
size: one successful, one failure, single nozzle one-plane motion. Several firings, 4.9-in. throat
High coulomb torque Unpredictable friction torque
One firing, 9.6-in. throat, single submerged nozzle.
Sealing problem Antirotation device required High axial thrust loss
Development
Small deflection Ball and socket (ref. 45)
(fig.5)
envelope
Potentially lightweight Small envelope requirement Large deflection capability Flexible pivot-point location Deflection
Two firings of Minuteman motor, first-stage
of the seal region
is minimized and seal gap is maintained by uniformly distributed load
Notes: Throat dimension in column 4 is throat diamct_. Factors for converting U_. customary units to SI ualts are presented h_ Append_ A.
flexible joint.
discontinued
in favor of
TABLE I1. - Advantages, Disadvantages, and Current Status of Seeondmy In_
Liquid injection (refs. 46-51) (fig. 9)
Disadvantages
Advantages
System
Systems
Status ofTechnology
State of the art
Limited thrust deflection
Operational system for Polaris A3 second
Liquid injection thrust adds to motor thrust
System weight is high Careful attention must be given
little
to selection of liquid and bladder
stage;Minuteman III second and third stages; 120-in. motor for Titan IIIC and IIID; Sprint first- and second-stage motors; Hibex motor; and Lance motor.
prelaunch
checkout
required Fast response capability
material for long-term storage A long hold period after the system is energized requires replenishment of the liquid and pressurization devices Lack of flexibility for accommodation
Development static firings on 120-in. Titan IIIM motor, 156-in. motor, and 260-in. motor.
of changes in control
requirements Must be designed for worst-onworst requirements
oo
Gaseous injection (refs. 52-62)
(fig. lO)
Little prelaunch
check out
required Fast response capability Lighter in weight than liquid injection
systems
Should be linfited to applications
Demonstration
static firing on 156-in. motor.
with required thrust deflection
Demonstration Demonstration
static firing on 1204n. motor. static firings of Minuteman
angles less than 7° Cannot be used where precise velocity control is required Hot-gas valve is subjected to severe thermal environment Warm-gas valve requires large and heavy gas generators Additional propellant necessary to recover thrust losses
Note: Dimensiongiven in column 4 is motor diameter.
motor, first-stage size. Problems concerning durability
of materials
for valves and pintles need to be solved.
•
TABLE !II. - Advantages, Disadvantages, and Current Status ofMechanical Deflector Systems
System Jetvane (refs. 10,63, and 64)
Advantages Actuation torques are low Small installation envelope around nozzle Power requirements are low, and thus actuator weights are low Fast response capability
Jetevator
Side force is linear with
(refs. 65-69)
jetevator deflection angle
Disadvantages
Status of Technology
High thrust losses Restricted to motors with lowtemperature propellant short burn time
or
Operational system for Sergeant, Talos, and Pershing and for Algo !I and 111 motors. No current development.
Large vane rotation angle required for small jet thrust deflection Jetevator envelopes nozzle exit, restricting maximum available nozzle exit diameter
Operational system for Polaris AI first and second stages and Polaris A2 first stage.
Restricted to motors with low-
Operational system for BOMARC and SUBROC.
temperature propellant short burn time
or
No current development.
Heat shields required to protect afterdome, nozzle exterior, and actuation system significantly increase total system envelope
',D
Large thrust loss (half of generated side force) Torque varies with time System is relatively heavy Limited to multiport systems for omniaxis vectoring. Jet tab
Side force is directly
Restricted to motors with low-
(refs. 70-74) (fig, 11)
proportional to ratio of tab area to nozzle area
temperature propellant burn time.
or short
Caused significant local erosion in the nozzle
Limited to development static firings. Test results indicate significant design and material problems. No current development.
Large thrust loss (equal to generated side force) Jet tabs at the exit plane increase envelope requirements Segmented
nozzle
(refs. 12 and 58)
Major portion of nozzle is fixed to motor Thrust losses at small deflection negligible.
angles are
(Testing to date insufficient to determine disadvantages of system)
Limited to experimental static firings. No current development.
Table IV. - Advantages, Disadvantages, and Current Status of Special Systems
i
System Movable pintle (refs. 1 and 12-14)
Advantages Can be used as a throttling device
Side forceis nonlinear
Omniaxial movement is
Plug subjected to severe thermal environment
C_
Movable plug (ref. 2)
Status of Technology
Disadvantages
possible
with
pintle cant angle Small pintle cant angles produce negative side forces Pintle subjected to severe thermal environment
Analytical and experimental development only. No current development.
Limited to cold-flow air tests. No current development.
Fixed
structure Subsonic
splitline
\
Figure
Low
Fixed
_
structure
Figure
2. - Gimbal/swivel
subsonic
subsonic-splitline
Movable
nozzle
Movable
nozzle
nozzle.
splitline
_ Gimbal 3. - Gimbal/integral
Iow-subsonic-splitline
nozzle.
I Fixed
structure Supersonic
splitline Movable
Gimbal
Figure
4. - Supersonic-splitline
]1
nozzle.
nozzle
ovab le nozzle
Ba 1 i/socket
Antirotation
Figure
5. - Ball-and-socket
Rolling
bellows
nozzle.
bearing Bolted
joint
table nozzle
Seal
Figure
6. - Rotatable
12
canted
nozzle.
Bellows
insulating
boot
_eomet_ic
£orward
pivot
poi
_ctuator
Flexible joint Radiation
/
shield
X
/
I
] Elas
Reinforcement
boot
I
ttOmer
_, ,,
_
_
insulating
bracket
\
nozzle
Wrap-around
_
]
Fixed
_y_
_"
Aft
/
geometric
_pivot
point
I
I (a)
Flexible
joints
with
insulating
boot
Reinforcement
E la s tome
/
r
Ablative
protection
Fixed
Movable
'_Aft
attach
r±ng_
\_
attach
structure
nozzle
ring
i Aft
geometric
pivot
J (b)
Flexible
joint
with
sacrificial
Figure 7. - Flexible-joint
13
ablative
nozzle.
t
protector.
point
_---
1
'_
_l_u_: one
Falbric_reinforced
neoprene
bladder
Pivot
-
point (a)
Neutral
position
Extended
side
.Vector
angle
,ressed ide_
(b)
Figure
Vectored
position
8. - Fluid-bearing/rolling-seal
14
nozzle.
Act
us for
bracket
Actuator
Exit
_lild
cone
tank_ valve (a)
External
(b)
Submerged
Figure
9. - Liquid
nozzle
nozzle
injection
Gas
TVC
system.
injectant
I
Hot-gas
valve
Motor
Figure
10. - Hot-gas
TVC
]5
system,
leg mounted.
_
._ XIE cone
xit
Exit
(b)
Submerged
Figure
11.
cone
cone
nozzle
- Jet
tab
16
TVC
systems.
comparison showed that the actuation percent of the actuation torque for the (60.96 cm) diameter have been tested vectoring 35
rates
and
36).
vector
up to 40 An
angles
demonstrated
The
(20.32
and
2) of for for
or
flexible
pressures
rates
bearing up
up has
to 1000 been
to 140 deg/sec
tested
and
for
an
operational
flight
motor
MN/m 2) (refs.
in static
motor
and
firings
pressures
up to
up to 2700
therefore
will
not
be
in this monograph.
joint
has
demonstrated
the
capabilities
of the
gimbal
development problems, has been demonstrated in a number operational in the first- and second-stage motors for Poseidon treated in detail in this monograph (secs. 2.1 and 3.1).
Liquid (table
psig (6.89
for firing times of 20 seconds (ref. 35). This bearing has also been tested + 15 °, vectoring rate of 762 deg/sec, and motor pressure of 2100 psia a firing time of 5.5 seconds (ref. 35). The fluid bearing/rolling seal has use in a large high-performance motor, but as yet has not been
accepted
further
motor
cm)-diameter
of + 12 ° at vectoring
psia (18.6 MN/m at vector angles (14.5 MN/m 2) been selected evaluated
8-in.
deg/sec,
torque for the fluid bearing/rolling seal was 30 flexible joint. Fluid bearing/rolling seals up to 24-in. in static firings up to vector angles of -+ 6.5 °, at
injection.II) has been
A large amount accumulated. The
of experience liquid-injection
splitline
but
with
fewer
of flight motors, and C3; therefore, this joint
on secondary-injection system is a state-of-the-art
is is
TVC systems system that
is operational on several vehicles. This system has the advantage over the movable-nozzle system in that most of the excess liquid can be dumped after staging and recovery of flight attitude, the vehicle thereby having less inert weight during the remainder of the flight than the vehicle that must continue to carry nozzle actuation hardware. Hot-gas injection systems are promising, but valve and piping problems due to the severe thermal be solved. Warm-gas injection systems reduce the thermal environment large
and
heavy
this monograph
Mechanical
gas generators. (secs,
systems.-
The
2.2 and
The
liquid-injection
system
therefore
is treated
in detail
listed
table
either
mechanical
are no longer being considered weights and material problems now
plug under
(table
IV) have
not
in
3.2).
deflector
systems
on
operational (e.g., jet vane and jetevator) but have now been replaced were limited to development static firings (e.g., jet tab and segmented
and
environment need to problem but require
in the industry. These techniques due to exposure to hot exhaust advanced
beyond
development.
17
limited
experimental
III
were
by other systems, or nozzle) and in general
generally suffer from high gases. The movable pintle evaluation
and
are not
2.1
The
FLEXIBLE
flexible
movable
joint
nozzle
JOINT
is a nonrigid that
direction*. The deflection moment about the vehicle Two
kinds
of flexible
position in figure descriptive terms definitions appears
2.1.1
pressure-tight
allows
the
nozzle
joints
are
shown
of the
a movable any
in figure
by
the
rocket
as much
as
motor 15 ° in
and
a
a given
the motor thrust vector and generates altering the course of the vehicle. 7. The
flexible
joint
13. These complete
is shown
a
in a neutral
figures also show list of symbols
the and
Configuration rings of an elastomeric These rings are usually
flexible
nozzle. direction.
elastomeric part of the
Since When
components total vector
material spherical
alternating with rings of sections with a common
to as the geometric pivot point. A joint wherein the rings were sections has been designed and successfully tested (ref. 22). This of requiring a single set of tooling for all the rings rather than
tooling for each ring as is necessary the joint was limited to a cylindrical
in
between
deflected
12 and in a vectored position in figure used throughout this monograph. A in Appendix B.
center of radius referred identically shaped conical design had the advantage
end
connection be
of the nozzle deflects center of gravity, thereby
The flexible joint consists of metallic or composite material.
One
to
joint the the
with spherical envelope.
is connected joint
rings.
to a fixed
is symmetrical
nozzle
are strained angle, and
is acted
Since
each
ring had
and
the other
structure,
about upon
its centerline, by
an
the
same
is connected
the nozzle
external
shape,
actuator
to
can vector force,
the
in shear, each reinforcement ring rotates a proportional the nozzle rotates about the effective pivot point (fig.
13). Usually the effective pivot point does not coincide with because of different amounts of distortion in each reinforcement.
the
geometric Omniaxis
pivot point movement of
the nozzle is obtained by using two actuators 90 ° apart. In addition to providing a means for thrust vectoring, the joint also acts as a pressure seal. Flexible joints are designed so that the axial compressive pressure imposed on the elastomer is higher than the chamber pressure. An important property of the elastomer in the operation compressive modulus is approximately 15 000 times the shear
* This
amount
of
motion
has
been
demonstrated,
but
an upper
limit
to deflection
of a joint is that the bulk modulus. This relation means
angle
has
not
been
established.
18 '\
Ro + Pivot
radius
Geometric
pivot
point,common center for Joint
joint angle
_1
Outer
joint
as tomer Reinforc
Figure
12. - Flexible
joint
]9
all
angle "oint
Inner
Ri
Rp =
in neutral
position.
ement
angle
radii
Deflected
joint
Original
joint
Geometric
Vector
angle
@
envelope
pivot
point
point Effective
I,
/----
Joint
0
U
Deflected
joint
0
0
__.._ .-
Rotation \
jl
Figure
about
13. - Flexible
joint
20
effective
in vectored
occurs pivot
position.
point
pivot
that a joint but permits
can transmit high axial compressive high shear deflections at low applied
The reinforcements to motor pressure
cylinder
The
nozzle
with
section,
the
movable
flexible joint. fixed structure
DESIGN
Flexible-joint reinforcement materials
when
an actuator a
actuation is discussed
design
protection.
These
motor
requirements
design
previous
;_,applied ai>plied geometry apart each
of
structure,
four the
main
subsystems:
actuation
system,
pressure,
(ref.
is dependent
incremental analysis increment
when
the
joint to the in reference
joint
and
actuator
not
in the plane cross section
be
must
be selected
the number layers, and
of the
combined
to
and
angle,
and
envelope
constraints
must be determined in studies joint design requirements and
are specified. to define the stage
the and
77).
on many
geometric
variables,
and
no general
solution
for joint
is based on empirical relationships (refs. 17, 23, 78, and by finite-element techniques (refs. 80, 81, and 82), and to the analytical results. Analysis of a flexible joint is of and joint
procedure is conducted, and
elements
vector
material properties, large deflections and strains, nonsymmetric geometries during vectoring. However, test results and calculated results has been obtained by (ref. 80). The using material
a geometry
determined
load is axisymmetric, the deflected load is asymmetric (e.g., an actuation will
joint
the and the
performance, and reliability at minimum weight and Joint design is affected also by the attachment to the nozzle. In some programs, the basic joint design
these design requirements relationship between the
complicated by nonlinearity nonsymmetric loading systems, reasonable correlation between
the
consists fixed
system on the flexible in this monograph.
design exists. Preliminary design 79). A selected design is analyzed the design is modified according
use of an finite-element
and axial loads due sideways as would
consists of the determination of the joint configuration, the material for the reinforcement rings and elastomeric
including programs, tradeoff
joint
deflections,
OPTIMIZATION
design rings,
requirements
The
axial
was applied.
joint to the
provide the required spring stiffness, within cost and envelope limitations. fixed structure and the movable
vehicle
load
flexible
attachment
for environmental
In other optimum
resulting
The movable-nozzle section and the attachment of the flexible are treated in reference 75, and actuation systems are treated
76. The effect of the characteristics interact
2.1.1.1
low
provide rigidity to the joint against motor pressure and constrain the joint to vector instead of deflecting
an all-elastomer
movable-nozzle
loads with torques.
axisymmetric.
of actuation have is axisymmetric
from
the
previous
increment.
geometry will be axisymmetric. load applied by one actuator),
The
deflected
been (refs.
analyzed 22 and
21
load is applied incrementally, properties associated with the
geometries
at two
cross
and a stress at When
the
the •
When the deflected
sections
180 °
by finite-element methods that assume 78). Methods of mathematical analyses
other
than
the
finite
material
anisotropy
2.1.1.2
ENVELOPE
The
joint
element (refs.
envelope
have
been
employed
to consider
(fig.
angle/32 /32-55 The
12) nor
difference
minimum
value
deformations
and
LIMITATIONS is defined
by the
less than
pivot
0 °. It has
up to 70 ° are feasible; °- may
joint
83 and 84).
radius
Rp,
the inner
/32, and the cone angle _b (fig. 12). The pivot radius is throat diameter, but the inner and outer joint angles designer. All joints that have been successfully tested to 40 ° to 45 °, angle t32 ranging from 45 ° to 55 °, and angle angle/3
finite
not be the
limit.
between
the
possible
without
these
inner
been
and
suggest
outer
exceeding
joint
the
outer
joint
angles
131 and
determined primarily by the nozzle and cone angle are selected by the date have had angle/31 ranging from ¢ that was not greater than the joint
demonstrated
results
and
by
that
analysis
the largest
angles
allowable
that
joints
demonstrated
with value
for
at
the
(/32 -/31 ) is maintained
elastomer
stresses,
so that
an
the joint
spring torque is kept to a minimum. It has been shown analytically (ref. 17) that the cone angle significantly affects the joint axial deflection and the elastomer and reinforcement stresses. As the cone angle increases, these values increase, and the effective pivot point moves farther from the geometric pivot point (fig. 13). However, decreasing the cone angle has resulted in nozzles with large section of the nozzle and require the
amount
Cost
also
with
has been
cylindrical
2.1.2
that increase the weight of the movable envelopes in the motor, thereby reducing
of propellant.
conical-shaped
section,
re-entry sections larger clearance
envelope thus
reducing
a factor
in determining
reinforcements
was
(_b =/3 as shown tooling
and
the joint
The must
A large The
on fig. 13), and each
fabrication
joint
flexible was
reinforcement
joint
designed had
the
(ref.
22)
with same
a
cross
costs.
Design Requirements
The requirements affecting the design of a flexible angle, axial deflection, frequency response, motor sealing,
envelope.
manufactured.
cost,
actuation
joint are nozzle actuation torque, vector pressure, environmental effects, pressure
and weight. torque
be estimated
(sec. for
2.1.2.1),
preliminary
is made design
up of many and
subsequently
vector angle (sec. 2.1.2.2) required to produce sufficient dependent on the position of the pivot point (fig. requirements.
Axial
deflection
(sec.
2.1.2.3)
affects
22
contributing
the
torques,
checked
in static
each
of which
firings.
The
maneuvering force on the vehicle 13) and the vehicle performance clearance
envelope
required
between
is
the fixed and movable portions of the nozzle; in addition, the axial deflection controls the axial spring stiffness of the flexible joint between the fixed and movable nozzle sections. The natural frequency and frequency responseof the movablesection(sec.2.1.2.4) depend upon the axial stiffness and the massproperties of the movable section. The frequency responseaffects designof the actuator andguidancecontrol system;sufficient stiffnessmust be designedinto the movablenozzleto avoid dynamic coupling of variousforcing functions. The motor pressure influences the selection of the joint materials and dimensions and affects the joint responseto all of the aforementioneddesignrequirements.The joint needs to be protected against a high-temperature environment on the motor side and the atmospheric environment on the outside (sec. 2.1.2.5). In addition, the joint must be a pressuresealbetweenthe motor andthe atmosphere(sec.2.1.2.6). Flexible joints with elastomericringsformulated from natural rubber havebeen operatedat elastomer temperatures ranging from 65° F (291 K) to 85 ° F (302 K), and have been vectored
in motors
operating
up to 600
not less than 65 ° F (291 acceptable results in bench (ref. 85).
2.1.2.1
ACTUATION
In order accordance
(182
required. The actuation torque total torque is the summation
including torques due to internal the following component torques: •
Joint
•
Frictional
•
Offset
•
Inertial
•
are
spring
and
external
torque torque
torque torque
Gravitational
identified
900
m) altitude
with
the
elastomer
at
has demonstrated K) to 165 ° F (347 K)
TORQUE
to define the requirements of the control with the motor or vehicle requirements,
actuation torque pivot point. The
Materials
000 feet
K). A joint with neoprene*/polybutadiene tests at temperatures from -40 ° F (233
torque
in Appendix
B.
23
system and to actuate the the designer must know usually is defined of a number of
aerodynamics.
The
total
about the contributing torque
nozzle in the total geometric torques,
is made
up of
• Insulating boot torque • Internal aerodynamictorque o The
External
total
aerodynamic
actuation
torque
torque
varies
from
motor
to motor
and
from
cycle
to cycle
continuous sinusoidal cycling on the been determined to be -+ 20% (refs.
nozzle. The total variability 86 and 87). The variability
including of a new
determined,
be
not_ identical
since
prior
results
may
based
on joints
that
are
during
both items has design must be to
the
new
design. 2.1.2.1.1 The
Joint Spring Torque
flexible-joint
spring
torque
(resistance
of
maximum torque contributing to the actuation factors: total thickness of elastomer, pivot radius, affected '2.1.2.5.2).
by
environmental The resistance
• convenience
of analysis,
geometric
pivot
point
the
joint
necessary
torque
to the line of action
The spring torque is dependent on the combined on the thickness of each ring (ref. 17). The spring of the pivot radius (i.e., Tq _ Rp 3 are a minimum, the joint diameter
mechanical is overcome
is calculated
of the
movement)
torque. It is dependent joint angles, and motor
effects on the elastomer of the joint to movement the
to
as the
usually
on a number of pressure; it is also
characteristics by the actuator; moment
arm
(sec. for
from
the
actuator. thickness of all the elastomer torque is roughly proportional
rings and not to the cube
Therefore, to ensure that the spring torque is minimized by placing the joint as close
).
is the
and envelope to the throat
plane as possible; the pivot radius is then made as small as possible, but not so small as to increase the stresses in the joint above the allowable values. The inner and outer joint angles /31 and/32 (fig. 12) control the joint thickness. is kept to a minimum consistent with the
As noted, elastomer
the difference between allowable stresses. The
these joint
angles spring
torque reduces attributed to
as the motor pressure increases the effect of compression on
(refs. 13, 22, 86, and 87). This phenomenon the elastomer shear modulus properties,
configuration
of
in shape
the
joint,
and
the
change
of
the
joint
(refs.
83
and
is the
84).
If
sufficient pressure is applied, the spring torque can become zero. Little data are available on the variation in spring torque. Tests conducted on joints for two different motors that used a natural-rubber formulation show a variation of + 20% at zero pressure. This torque variation in absolute units remained approximately constant and independent of motor pressure modulus For
rapid
(refs. 86 and 87). The variation of the elastomer (sec. 2.1.3.1 ). calculation
number of equations correlation with test
of the have results
Spring
was correlated
torque
for joints
with
with
lot-to-lot
spherical
variation
reinforcement
in the shear
rings,
a
been developed (refs. 17, 21, 23, and 78). Of these, the best for many different joints is the expression (adptd. from ref. 78)
24
_
Tq 0
12Goroari ro 3_
ri 3
(1)
3 [I(fl2)-I(fl,)]
where = joint
Tq
spring
0 = vector Go
torque,
angle,
= elastomer
in. - lbf (m-N)
radians
secant
shear
modulus
at 50 psi (0.345
MN/m 2)
shear
stress (sec. 2.1.7.1), with no externally imposed pressure, at the elastomer temperatures expected in operation, psi (N/m 2) ro
= Rp
+ nte/2,
in. (cm)
q
= Rp
-
in. (cm)
Rp t_ n
_, _
nte/2,
= pivot
radius
= thickness
of individual
= number = inner
of elastomer and
I(f3) = integral
in. (cm)
outer
values
TABLE
V.
elastomer
in. (cm)
rings
joint
angles,
listed
in table
-
layer,
deg V (ref.
78)
Integral Values 103) for/3 = 15 ° to/3 = 60 ° (ref. 78)
fl, deg
10)
/3, deg
15
0.0518
27
16
.0588
28
.1713
40
.3249
52
.4999
17
.0661
29
.1828
41
.3389
53
.5148
18
.0739
30
.1946
42
.3531
54
.5298
43
.3674
55
.5448
/3, deg 39
0.1601
t_) 0.3110
/3, deg 51
I Wig) 0.4849
19
.0820
31
.2067
20
.0906
32
.2189
44
.3818
56
.5599
21
.0995
33
.2315
45
.3963
57
.5749
22
.1088
34
.2442
46
.4109
58
.5899
23
.1184
35
.2572
47
.4256
59
.6048
24
.1283
36
.2704
48
A403
60
.6198
25
.1386
37
.2838
49
.4551
26
.1492
38
.2973
50
.4700
25
From
test
data,
the
following
pressure has been natural-rubber-formulation
empirical
developed elastomers
Tq
relationship
for (adptd.
0.156Gro
0
--
calculating
joints with from ref. 78):
3 ri 3 (/32 -
ro 3
for
steel
the
spring
torque
reinforcements
/31)
at and
(2)
ri 3
where G
= effective
elastomer
pressure, = Go A
shear
modulus
when
subjected
to external
psi (N/m 2 )
+ Ao 2
= constant
(3)
depending
= - 0.2595
upon
reinforcement
material
x 10 -6 for steel Pc sin2/32
O2
(sin2/32
Pc
from
joints
with
equation
cone
Friction bearings friction
torque in and O-rings. theoretically major
cos 2 q_
psi (N/m 2)
deg
angles
(2) have
Friction
three
pressure, angle,
2.1.2.1.2
from
- sin2/31)
= motor
q_ = cone
For
(4)
=
agreed
varying within
from
15 ° to 50 ° , at high
+ 8% with
torques
measured
pressure, in bench
torques
calculated
tests.
Torque a conventional movable nozzle arises from sliding surfaces Since there are no sliding surfaces in a flexible-joint nozzle, does not exist. Elimination of the joint friction eliminates
sources:
26
such as coulomb problems
(1) Friction varies significantly from unit to unit and cannot be predicted with accuracy. (2) Friction is the major sourceof steady-stateerror in the servoactuator system. (3) The changefrom static to sliding friction causesa breakawaypeakin actuation. Although there is no sliding friction in a flexible joint, the joint doesrespondto actuation in a manner similar to that of a spring-masssystemwith both viscousfriction and coulomb friction. The viscousfriction probably is associatedwith the viscoelasticbehavior of soft elastomeric materials. Viscous damping is an important consideration in determining the stability characteristicsof the thrust vector control system. No methods are availableto calculate either coulomb friction or viscous friction. Attempts to calculate the damping coefficient from the decaying actuator force transient occurring at the end of a step vector-angle function applied to a nozzle have been unsuccessfulbecauseno correlation could be obtained with the friction coefficient calculated from actuation data. For sinusoidal actuation of the nozzle, the viscoustorque component doesnot contribute to the maximum actuation torque, sincethe viscousfriction torque is a maximum when the nozzle is at zero position andzero when the nozzle is fully vectored. The coulomb friction and viscous friction are determined experimentally. A nozzle is vectored at different frequencies but constant amplitude, and the actuator force is measured.A typical actuator force responseis shown on figure 14(a); the actuator force at zero vector angle is the total friction. When the variation in total friction force with vectoring rate is plotted as shown in figure 14(b), the two friction components can be determined. Experimental data have shown that for joints fabricated by the samemanufacturer the variation in viscous friction is -+30% and for coulomb friction is -+15%(ref. 88). Joints fabricated by different manufacturers to the same specifications have demonstrated significantly different friction torque results,although the variability wasapproximately the same. Test results have indicated that the viscous friction is dependent on vectoring amplitude in addition to vectoring rate. The coulomb friction has been shown to be dependent on vectoring amplitude and pressure.The phenomenon of friction is little understood, and the elastomerproperties anddimensionsinfluencing friction havenot been identified. 2.1.2.1.3
Offset Torque
Offset torque manufacturing during additive
is the torque tolerances.
resulting from Consequently,
motor firings. The offset torque to that due to nozzle vectoring°
asymmetry in the nozzle offset torque can occur
due to misalignment and in bench tests as well as
during a motor firing is an aerodynamic torque The amount of alignment offset is dependent on
27
t Total
frequency
friction
+ Vector
Total
--
Response
friction
to
slnusoldal
different Highest
(a)
angle
actuation
at
frequencies
frequency
Variation
in
vector
angle
with
sinusoidal
actuation
force
O 4J U v_4
Rate-dependent
component
(viscous
friction)
! 4J O
Rate-independent
Maximum
(b)
Figure
14.
Variation vectoring
- Graphical
vectoring
in total rate
presentation
component
friction
of
the
28
effects
(Coulomb
friction)
rate
with
of
maximum
friction
sinusoldal
in a flexible-joint
nozzle.
axial deflection characteristics be at zero vector angle (sec. diameter has been small determining the actuation torque
could
2.1.2.1.4
of the joint 2.1.2.3). The
contribution
to the
actuation
torque is determined the movable section
by assuming of the nozzle
of the vector
the
actuation
it is ignored in joints the offset
torque.
joint acts with the angles at zero motor
spring
torque
cycles,
and
even
produced The inertial
less
to a fixed structure, and in the determination movable nozzle it is usually assumed that half
movable pressure,
at high
is much
point resulting from accelerations on the vectoring acceleration.
that the mass of the nozzle acts at the center of gravity of and that the movable section vectors about the geometric
pivot point. One end of the joint is connected of section mass and center of gravity of the
with
at which the nozzle must up to 22-in. (55.88 cm)
Torque
The inertial torque is the torque about the pivot on the nozzle by the actuator and is dependent
the mass maximum
pressure for joints
in comparison with the spring torque, and torque. However, it is possible that for larger
be a significant
Inertial
and the motor offset torque
section. For joints the inertial torque
vectoring
than
the
rates
up
variability
to
designed to demonstrate usually is small compared
500
in actuation
deg/sec
for
torque
from
sinusoidal motor
to
motor. 2.1.2.1.5
Gravitational
The gravitational movable nozzle maneuvers,
Torque
torque is the torque produced mass as a result of accelerations
pitch,
yaw,
and
axial
gravity, causing axial and lateral As before in the determination assumed usually
to act with is small
with
2.1.2.1.6
Insulating-Boot
A flexible
joint
7).
Either
separates The
this
often
wrap-around
a wrap-around a 13-in. (33
and boot
section. the
accelerations
booster
is protected boot
against
hot
is wrapped
motor
1255
center
vehicles,
of
nozzle. mass is
the gravitational
directly
gases by use of an insulating
torque
around
the
joint,
or
boot
a dead
air
(fig. space
the boot. adds
significantly
to the
nozzle
boot fabricated of silica-filled butadiene cm)-diameter joint increased the actuation
DC
vehicle
torque.
m-N/deg) to 2100 in.-lbf/deg (237 m-N/deg) changed to a bellows type (fig. 7), the actuation 1600 in.-lbf/deg (180 m-N/deg) (ref. 14). incorporating
at the
at the center of gravity of the movable and center of gravity, half of the joint
For large
spring
occur
by the vehicle
Torque
insulating
the joint
lateral
accelerations of net mass
the movable
compared
and
about the geometric pivot point imposed by the vehicle. As the
silicone
rubber
resulted
29
vectoring
torque.
For
acrylonitrile rubber torque from 1000
example,
use of
(GTR V-45) on in.-lbf/deg (113
(ref. 13). When the design of the boot was torque increased from 1000 in.-lbf/deg to A wrap-around boot design (fig. 7(a)) in a 20%
increase
in actuation
torque
for a
joint 22 in. (55.88 cm) in diameter. This was
found
to be
i_ct_ase 'was ratio of joint
dependent
on
increase was not uniform from joint to joint the boot was bonded to the reinforcements:
whether
greater when the boot was diameter to insulating boot
bonded thickness
to the reinforcements. In general, as the increases, the proportionate increase in
actuation attributable percent.
torque due to the boot will be less. to the insulating boot for a joint 112
2.1.2.1.7
Internal
.... _ '"_Th_ :internal
Aerodynamic
aerodynamic
For example, the increase in torque in. (2.84 m) in diameter was 11 to 15
Torque
torque
acting
on a submerged
nozzle
is the
result
of unsymmetric
flow between the around the vectored
propellant grain and the movable nozzle. Pressure nozzle cause side forces and a resultant torque.
variations
If the
pivot
is forward
torque
torque
and
point hence
and the
of the
is an increment
nozzle
to the
throat,
actuation
the
aerodyl_amic
torque
and
needs
that
occur
is a restoring
to be calculated.
If the
pivot point is aft of the nozzle throat, the aerodynamic torque is sustaining and reduces the actuation torque (ref. 23). For an aft pivot point, the aerodynamic torque usually is ignored in calculating the actuation torque, thus ensuring a conservative estimate for actuation torque.
However,
if a system
were
designed
to be vectored
only
at pressures
that
result
in a
low spring torque, the aerodynamic spring torque and produce a negative tolerated in a closed-loop system.
torque with an aft pivot point could actuation torque. A negative actuation
The aerodynamic torque is calculated point produced by the pressure forces knowledge of the wall static pressure
by summing the moments about the geometric pivot acting on the nozzle wall. This procedure requires a and the pressure differentials existing in the nozzle.
Two procedures are available airflow simulation tests (ref.
for developing the internal 89), and a two-dimensional
overcome the torque can be
wall pressure in a vectored method-of-characteristics
nozzle: solution
(ref. 90). When the aerodynamic torque is calculated from the results of a_rflow simulation tests, the calculated value generally is within + 20% of the measured value. When the aerodynamic torque is calculated from the results of a two-dimensional method-of-characteristics analysis, the result generally is within + 50% of measured value. As the grain burns and the clearances between the nozzle and the distribution becomes more symmetrical, so that the aerodynamic significance near the end of propellant burn. 2.1.2.1.8
External
Aerodynamic
In
specific
cases,
pressure of little
Torque
During flight, the external air stream impinges on the component, especially in the high dynamic pressure required.
grain increase, the torque becomes
this
effect
perhaps
30
nozzle region could
exit cone and creates a torque when large vector angles are be
utilized
to
increase
the
maneuverability of the vehicle in this flight region or to provide vehicle control after motor burnout. The external aerodynamictorque could be calculated from the pressureacting on the nozzle exterior surface in the same manner as the internal aerodynamic torque is calculated(sec.2.1.2.1.2). However, in most boosterapplications, the exit coneis shrouded by a motor caseskirt that preventssignificant air impingementthat would causean external aerodynamictorque. 2.1.2.2 The
NOZZLE
amount
the
nozzle
The
pivot
VECTOR
of nozzle
vector
is vectored, point
Vectored
can
nozzle,
Vectored
nozzle,
ANGLE
the be
pivot
PIVOT
side or aft
force of the
by the vehicle acts
aft
control
approximately
nozzle
throat
(fig.
requirements.
through
the pivot
15).The
position
/
pivot
Envelope
for
forward
pivot
point
point
for
forward
pivot
point
Envelope
1
,._
_SS
_ aft point _
| _J
Nozzle
in
neutral
position Forward
pivot
point Aft
Figure
point. of the
pivot
for
Envelope
When
point
/ Envelope
POINT
is determined
resultant
forward
forward
aft
angle
AND
15. - Effect
of pivot-point
pivot
position
31
point
on required
envelope.
pivot
for
geometric
pivot
point
is selected
from
a tradeoff
on the exterior clearance envelope between the and stroke to fulfill vehicle guidance requirements, movable
nozzle
presented
in table
A summary
of the
comparative
study
that
considers
the
effect
of position
fixed and movable parts, the actuator force and the spatial envelope available for the effects
of a forward
or aft pivot
point
is
VI.
TABLE VI. - Comparative Effects of Forward and Aft Geometric Pivot Point Comlmmtive effect Item
Reduced
Increased
Clearance envelope for exit cone
Increased
Reduced
Actuator stroke to produce a particular vector angle
Increased
Reduced
Actuator force to produce a particular vector angle
Reduced
Increased
Vector angle to produce a particular vehicle movement
Increased
Reduced
pivot point less envelope
will reduce the moment arm to the vehicle center angle to generate the necessary turning moment.
will reduce the required vectoring angle. A forward for movement of the nozzle nose cap region but more
exit cone (fig. 15). The moment arm from the forward pivot point, and therefore less actuator cone movement is increased, the actuator stroke Because
of the
recluced
nose-cap
movement,
(fig. 15). Regardless of whether tested to date has been between
pivot
points
generally
is greater with a because the exit
are
used
for
the motor chamber. Aft pivot points generally because the envelope for exit cone movement movement reduces the envelope available for
a forward or aft pivot 45 ° and 50 °.
32
of gravity Similarly,
pivot point will envelope for the
pivot point to the actuator force is required; however, is increased. forward
nozzles having little or no submergence into are used for nozzles having deep submergence, is critical. However, the increased nose-cap propellant t3 on joints
Aft pivot
Clearance envelope in nose cone region
As shown, a forward pivot point and thus require a large vectoring an aft require
Forward pivot
is selected,
the joint
angle
The position of the effective pivot point is dependent upon the applied loads and joint configuration. The actuator force, in addition to vectoring the joint, causes a movement of the joint in the radial and axial direction, so that the effective pivot point is offset from the geometric differently,
pivot point (fig. 13). Vectoring of the joint causes strongly influencing the position of the effective
each reinforcement to deflect pivot point. At zero motor
pressure, only the actuator force causes pivot point movement. At motor pressure, compressive load is applied to the joint and causes additional pivot point movement. 16 shows the measured pivot point movement for three different joints varying inches (53.3 cm) and at maximum by decreasing reinforcement reinforcement
diameter expected
to 112 inches (2.84 operating pressure.
an axial Figure from 21
m) diameter, vectored at zero motor pressure The pivot point movement can be decreased
the cone angle. Analytical studies (ref. 17) have indicated that the stresses decrease as the cone angle decreases (sec. 2.1.5.3), because the deflection decreases. Reduced reinforcement deflection results in reduced
pivot point movement. As shown in figure 16, pressure lateral movement of the pivot point due to vectoring. A knowledge
of the
effective-pivot-point
location
acting
on the joint
is important
also reduces
in establishing
the
the
clearance
envelope between the fixed and movable nozzle components. In one flexible-joint program, the effective pivot point was assumed to have moved an amount equal to the axial deflection, and a clearance envelope was set up accordingly. It was subsequently determined that the effective pivot point had moved approximately 1.5 in. (3.81 cm) while joint axial deflection was 0.4 in. (1.02 cm). The allowed clearance envelope was too small and had to be increased
by removing
predicts the lateral pivot-point position
2.1.2.3
AXIAL
Although
the
joint.
No
method
has
been
An approximate in the following
developed method section.
that
accurately
to determine
flexible
joint
stiff
in compression
in comparison
amount of axial compression occurs when the axial compression to determine nozzle
spring
acts to increases
is relatively
stiffness,
reduce some the vectoring
and
the
nozzle
clearances clearance
misalignment
between around
with
its vectoring
the motor is pressurized. envelope requirements, requirements.
axial the
properties envelope,
compression cone angle. in and
is dependent The axial
on the elastomer stiffness, the reinforcement compression involves an interaction among
compression, deformation the ratio of the dimensions
of the of the
33
The
It the axial
the fixed and movable nozzle the exit cone, and influences the
position of the pivot point. The spring stiffness is required in the design of the control system. The fixed-length actuator causes vectoring of the nozzle by motor and the nozzle is misaligned at zero pressure so that it is aligned at some required The and
the
DEFLECTION
compressive
compression components,
of the
movement of the pivot point. due to axial load is presented
stiffness, a measurable is necessary to know axial
part
elastomer, elastomer
guidance pressure, pressure. stiffness, elastomer
reinforcement stiffness, rings to the reinforcement
joint rings.
Force Joint
description
system
geometric
st
pivot
eosition
of
with
respect
point
effective to
pivot
(a) Mean
Joint
diameter
m
112
53
radius angle
m 73 50 °
-
in.
motor
pressure
Geometric
(1.85
000
lbf(2.358
x
105
pivot
point
N)
m) Aft
Vector
angle
point
in.
(2.84 m) Pivot Cone
Zero
pivot
geometric
6
ffi 2 °
in.
(£5.24
cm)
+ .I x (5.76
106 x
--_
in.-Ibf 105 m-N)
_Axial position is reference
Effective pivot point
plane
5-1/2 (b)
At
motor
pressure 3.97
49
000
Ibf
(2.180
1.15
x
x
105
10 6
(5.115
x
+---_
Ibf
10 8
cm)
N) Geometric N)
pivot
I-I/2 point Effective--
4.8 _*_----_/(5.42
x
1061n.-Ibf x 105 m-N) Joint
cm)
1
pivot
point
axial
deflectiou
pressure
in.
_---T(3,8i
Aft----Im_
ffi0.24
st
in.
(6.10
mm)
Geometric Mean
Joint
(53.3 Pivot Cone Vector
diameter
=
21
(a)
ih.
Zero
cm) radius angle angle
motor
1770 ffi 13.90
in.
(35.3
pressure
15f(7873
N)
I
in.
point
___/plvot
ca> $/__/
Aft
cm)
0.5
ffi 50 ° = 5°
1480
Ibf_(6583
+----.. 6327
At
(b)
:(1.27
iolhf
m-N)
t^ft...
Effective
pivot
210 000 ibf (9.341
x
105
N)_
835
N)
Aft_
ibf(3714
32 000 m_...._/(3615
point
2-1/4 _---
Ibfi(4448
om)
_
pressure
motor
I000
in.
N)
_
Aft
(5.71in. cm)
N)
.
0.02
Geometric pivot _Int
in.
(0.5
*mu)
ff tlve pivotS--- t
in.-ibf m-N)
point
Joint
axial
at
ffi0.4 pivot
Effective Zero
motor
1130
Ibf
(a) Mean
Joint
(53.7 Pivot Cone Vector
diameter
-
21.14
angle
_ 13.70 50.5 ° -
in.
(I.02
pressure
In.(34.80
(5026
N)
_
I
3100
ibf(13789
Aft
T
cm) 0.14
N)
5°
in.
(3.6
ram)
,%___t 000 (5197
in.-ibf m-N)
pivot
Geometric
Effective (b)
At
motor 785
Ii0
000
lbf
point
pivot
pressure
Ibf(3491
N)
(5.08
cm)
_ [
point
0.02 2160
lbf
(9608
in.
N)
I
(0.5 (4.893
x
i0
N)_
32
000
in.-ibf
(3615
m-N)
of pivot
point
for
34
three
point
mm)
| Aft-Jm_
at
16. - Movement
pivot
Geometric
Joint
Figure
ca)
point
in.
cm)
radius angle =
deflection
pressure
different
axial
pressure
flexible-joint
deflection -
O.3
in.
(7.6
nozzles.
_n)
Test
results
have
shown
compressive
loads
The
conditions
loading
compression
load
that
(refs.
these
22, 86, and for
due
interactions
in a nonlinear
response
to applied
axial
87).
a flexible
to the
result
joint
motor
consist
pressure
of an external
acting
on
the
radial
movable
The axial compression load due to motor pressure is calculated acting on the movable section. Solutions in the form of
pressure section
and
an axial
of the
by integrating equations to
nozzle.
the pressures predict axial
compression have not been satisfactory. Measured deflections have been as much as four times the calculated deflection. Most success in predicting axial compression has been obtained with computerized finite-element methods of analysis (refs. 78, 81, and 82). Reasonable correlations between calculated and measured axial deflections have been made with
the
use
of a sequential-loading
finite-element
method.
The
geometry
of the
joint
for
each loading increment is changed to the deflected geometry due to previous loading increments. For each loading increment, the elastomer shear modulus is assumed constant at the secant shear modulus at 50 psi (0.345 MN/m 2 ) shear stress (sec. 2. i .7.1), and all other elastomer ratio
properties
are
determined
assuming
isotropy
and incompressibility
(i.e., Poisson's
= 0.5).
An approximate estimate loaded by motor pressure point for each reinforcement.
of the position of the effective pivot point when the joint is is made by considering the movement of the geometric pivot When loaded by motor pressure, each reinforcement rotates
but undergoes negligible change point for each reinforcement amount, and the effective pivot
in cross-sectional shape. Consequently, the geometric pivot can be defined. Each reinforcement rotates a different point is approximately at a mean of all the geometric pivot
points.
2.1.2.3.1 Axial
Nozzle
deflection
attachment
points
Misalignment causes are
a
vectoring
a fixed
the guidance system begins the motor pressure increases.
misalignment
distance
apart,
of
as in the
the
nozzle.
case just
after
When booster
the
actuator
launch
to control the vehicle, the nozzle is not free to translate An actuator length that holds the movable components would be too short at operating the actuators were retracted (fig.
before aft as aligned
to the fixed components The nozzle at pressure
at zero motor pressure would vector as though
alignment condition
of the exit than in the
cone to the fixed components is less important in an unpressurized pressurized condition, the actuator length at zero pressure is set
minimize pressurized
the angle condition.
between the movable and the At zero pressure, this actuator
vectored as though the misalignment decreases.
actuators
were
extended.
35
pressure. 17). Since to
fixed components at some nominally length is too great, and the nozzle is As
the
motor
pressure
increases,
the
._Fixed-length
Nozzle position pressure
at
zero _/-
! ..__..I"
_41_
actuator
[ !_
i _ !. _
Axial displacement actuator brac_t
/__'--Misallgnment
!
of
an, le
, l-i'll
duetoaxi°l
...... Effective
pivot
point
"'-.
Nozzle after
position axial
"''--.
deflection"'--...j
Figure 17. - Effect of axial deflection (due to motor pressure)on nozzle alignment.
The actuator bracket (fig. 7(a)) usually is connected to the motor case; hence the actuator bracket deflects as the motor is pressurized. The effect of actuator-bracket deflection has to be
included
in determining
misalignment.
If the
actuator
bracket
is connected
to the
aft
adapter of a glass-filament-wound motor case, the misalignment due to act,6-ator bracket deflection is much larger than that due to axial deflection of the joint. This difference arises because the rotation of the aft adapter can be as much as 3 ° at maximum expected operating
2.1.2A
pressure
MEOP.
FREQUENCY
The_ movable nozzle -_ructure forms an
RESPONSE section additional
and the spring
frequency of the control system natural mode of nozzle oscillation, occurred
where
the
hydraulic
flexible in the
system. The fixed If a strong natural
applied through the actuators is near the frequency the nozzle oscillations will be reinforced. An instance
actuator
stiffness
36
/
joint form a spring-mass guidance control system.
was
low
enough
to be the primary
of a has
stiffness
determining
the
nozzle
natural
frequency.
All of the nozzle
subsystems
are designed
to have
enough stiffness so that their individual natural frequencies are high when compared with the driving frequencies transmitted through the control system. Preliminary estimates of the stiffness of each subsystem can be made, but mathematical models of the nozzle and actuation frequency
system are difficult to build without response, closed-loop damping, and
development
2.1.2.5
test data. open-loop
Consequently, damping are
tests to determine conducted early in a
program.
ENVIRONMENTAL
PROTECTION
Flexible joints are protected against exposure to hot motor atmospheres that could cause rapid aging of the elastomer. been demonstrated on a natural-rubber formulation (ref.
gases, warm atmospheres, The effect of temperature 91), the results showing
and has that
increasing temperature decreases the shear modulus, the allowable stresses and strains, and the strength of the bonds to the reinforcement. Atmospheric aging of specimens of natural-rubber formulations show increased shear modulus and reduced allowable stresses and
strains
aging
(ref,
(refs.
Limited
92).
93 and
studies
Other
studies
have
shown
that
silicone
rubber
is much
less sensitive
to
94).
(ref.
85)
with
laboratory
specimens
have
been
conducted
(1) neoprene, (2) neoprene/polybutadiene, (3) ethylene propylene butyl, and (5) silicone, for use in joints over a temperature range 165 ° F (347 K). The results showed that for all formulations (1) affected from -40 ° F (233 K) to 70 ° F (294 K) and decreases up to tensile elongation is neoprene/polybutadiene increases with decreasing
a maximum and silicone temperature,
K). The secant neoprene/polybutadiene
modulus at is little affected
shear
at 70 ° F (294 formulations showed and (2) shear elongation 50 from
psi (0.345 70 ° F (294
on formulations
of
terpolymer (EPDM), (4) from -40 ° F (233 K) to tensile strength is little 165 ° F (347 K), and (2)
K). Shear studies of the that (1) the shear strength is a maximum at 70 ° F (294 MN/m 2) shear stress K) to 165 ° F (347 K)
for but
increases significantly at -40 ° F (233 K), whereas the silicone formulation is little affected from -40 ° F (233 K) to 165 ° F (347 K). The neoprene/polybutadiene formulation was bench tested in a joint at -40 ° F (233 K), 70 ° F (294 K), and 165 ° F (347 K); the results showed torque
that (1) axial did not change
compression increased with increasing temperature, (2)the actuation from 20 ° F (266 K) to 120 ° F (322 K), and (3) with the value at 70 °
F (294 K) as a reference, the actuation torque decreased 18 percent at 165 ° F (347 K). 2.1.2.5.1 In most
Thermal cases,
the
increased
18 percent '_
at -40 ° F (233 K) and _ _ _ .... _
Protection flexible
joint
is protected
by controlling the atmosphere surrounding conducted with the joint at temperatures
against
exposure
the joint prior from 65 ° F (291
37
to warm
or cold
atmospheres
to firing. Most joint testing is K) to 85 ° F (302 K). Limited
bench testing has been conducted on joints at conditions from -40° (347 The
K) (ref. joint
F (233
K) to 165 ° F
85).
is protected
from
hot motor
gases either
by use of an insulating
boot
(fig. 7(a)),
by use of sacrificial ablative protectors (fig. 7(b)). As noted earlier, either the boot has been wrapped directly around the joint or a dead air space has separated and the boot. The wrap-around boot provides less heat-transfer barrier for thickness, boot and
because the joint.
there For
is no dead air space to act as an additional insulation the bellows-type designs, pressure relief holes through
required to balance the pressure across the boot. The vent holes allow the gas pressure to equalize during high rates of change ignition, the
so that
tearing
wrap-around
Both been
boot
is prevented.
the insulating and whether
boot requires decisions to expose the boot to the
from the high-temperature a radiation shield mounted
the exposed used. Motor
boot,
the
torque is greater more envelope.
requires
more
envelope
than
whether chamber
to use a wrap-around environment of radiant
required than
that
heating between
or a heat
char and erosion temperature, and
behavior velocity.
rubber. The boot and fixed sections
95 and 96) have material for the
as a function of strain in When a radiation shield is
and radiation shield are designed (fig. 7(a)) occurs in a stagnant around the such design,
and using a silicone rubber boot, showed only slight charring the boot needed to be thick enough to withstand only the gap between the boot and the protection shield. For the insulating of the
The sacrificial ablative protectors sufficient to provide a heat-transfer To minimize that the gap
to at
when the joint is actuated and the shape of the annular cavity is altered, there is little circumferential flow in the annulus. One
22 in. (55.88 cm) in diameter with no erosion. Consequently, radiant heating through the exposed
need to be sufficient of pressure occurring
boot (refs. 13, 14, and 23) and the protected boot (refs. designs using an exposed boot require an ablative plastic
the boot material is a silicone the gap between the movable
region. Even circumference
design
the are
motor gas stream or to minimize this heating by on either the fixed or movable nozzle components.
boot,making it necessary to know the addition to gas composition, pressure, provided, so that
This
between the boot
design.
The design of bellows design, transfer providing
of the
or
insulating the joint the same
material protected
extend barrier
is stiffer, boot.
outboard between
and
However,
thus the
the
increase
protected
in actuation boot
requires
of the elastomer rings a distance the hot motor gases and the elastomer.
in the cavity between protectors, the protectors is less than the elastomer
protectors thickness
are cross sectioned (fig. 7(b)). The
so gap
between protectors must be wide enough to prevent contact during vectoring or motor pressurization. Because there is a possible path from the hot motor gases to the elastomer, it is necessary environment
to determine the environment to the char and erosion
accumulation in the gaps anomalies in the vectoring
in the region characteristics
of the protectors of the protector
and
to relate material.
this Slag
after static firing has been noted, but this buildup did not cause response of the nozzle during firing. This result was attributed to
38
the lack of adherencebetween the slagandthe carbon-fiber/phenolic--resincompositeused for the protectors. The sacrificial ablative protector doesnot causean increasein actuation torque and requireslessenvelopethan the insulating boot with a radiation shield. All thermal protection designshave been tested successfully:the exposedinsulating boot with and without bellows (refs. 13 and 14), the protected insulating boot with and without bellows (refs. 23, 95, and 96), andthe sacrificial ablativeprotectors (ref. 25). Selectionof a design is made from a study evaluating such factors as gas characteristics(temperature, composition), gas flow (velocity, stagnation regions, pressure), envelope requirements, actuation power source, and overall system weight (actuation system, joint, insulating system)in relation to performancefactors (e.g.,range,payload, and reliability) and cost. 2.1.2.5.2 Tests
of
Aging Protection flexible
joints
using
a natural-rubber
surfaces protected from the environment changes, axial compression is reduced, change has been attributed to continued
formulation
(GTR
44125)
with
the
rubber
have demonstrated that, with aging, performance and spring torque is increased. The performance reaction of the components of the elastomer. The
spring torque increased by approximately remained constant thereafter (ref. 26).
six percent The joints
per year for 31/2 years in this program were
(ref. 97) and stored in an
atmosphere at 80 ° F (300 K) and where joints have been stored for data to be available. Similar results
approximately 50% humidity. This is the only program a sufficiently long period and in sufficient quantity for have been obtained in quadruple-lap shear and uniaxial
tensile testing 110 ° F (317
same rubber formulation; humidity for 9 months
modulus
from
of specimens K) and 90% 24 psi (0.165
The decrease in affects the nozzle nominally
of the relative
MN/m 2 ) to 30 psi (0.207
axial deflection misalignment
selected
operating
pressure
changes in joint performance made. The future performance probable
joint
life (ref.
that accompanies (sec. 2.1.2.3), since are
to
some
monitored, is compared
however, accelerated resulted in an increase
MN/m 2 ) (ref.
22).
increased spring it will change the
misalignment and projections with the motor
aging at in shear
at that
torque due to aging zero alignment at the pressure.
Currently,
of future performance are requirements to evaluate
26).
Elastomers less susceptible shear modulus and shear
to aging strength
are under development, make it difficult to
but the rigorous requirements of develop a satisfactory elastomer.
Further, the long time periods necessary to evaluate an elastomer make it difficult to assess property degradation with age for a new elastomer formulation. Accelerated aging tests at high relative humidity have indicated possible degrees of aging that have subsequently been found to be Silicone-rubber
more severe formulations
than are
aging under less susceptible
normal service to aging but
conditions (ref. 22). have a shear modulus
approximately 50% greater than that of natural-rubber formulations and a shear stress at failure approximately 50% less than natural-rubber formulations; in addition, silicones are more difficult to bond to metals.
39
A possibleadditional problem that hasbeen consideredis surface
by
either
ozone
possible exposed chlorobutyl rubber The
elastomer
showed
Such
elastomer or Hypalon
surfaces rubber.
uncured
condition
in the
a decrease
or oxygen.
in the
shear
oxidation are
coated
with
is susceptible
modulus
of
oxidation of the elastomer at its been prevented by ensuring that all
has
an
impervious
to aging.
Cured
rubber
material
A natural-rubber
of
1 psi (6895
such
as
formulation N/m 2) for
each
month of age of the uncured rubber stored at 40 ° F (278 K). The elastomer in this formulation was manufactured to as high a shear modulus as the specification allows so that if the shear modulus of the cured rubber decreased because of aging of the stored uncured rubber the formulation would for six months at 40 ° F (278
remain K) and
within if after
was
rubber
was
within
rubber
specification
the
specification. The" uncured storage the shear modulus
used,
but
if outside
rubber was stored of the cured rubber
of specification
limits
the
was rejected.
2.1.2.6 If the
PRESSURE axial
flexible
SEALING
compressive
joint
assures
that
force
due
the
joint
to motor
pressure
will seal against
is sufficiently leakage
without
high,
the geometry
the need
for any
of a special
precautions. The dimensions of the movable nozzle and joint are such that a compressive axial load is applied to the joint, the result being a compressive stress in the flexible joint that is greater than the motor pressure. Consequently, small unbonded spots and voids are tolerated. When joints are manufactured by injection molding or compression molding (sec. 2.1.6.3), unbonding cannot be detected. each
bond
line
assembled. the amount
2.1.3
can be controlled only on a sample basis, because unbonded areas For joints that are manufactured by secondary bonding (sec. 2.1.6.3),
can be inspected
for unbonding
Material
elastomer, insulating material for a given
boot, and use depends
that
seeks
techniques
as the joint
is no quantitative
to optimize
its environmental bonding system
protection, between
is being
definition
materials need the reinforcement
protection from the external atmosphere. on the motor operating requirements (e.g.,
vector angle), the environmental propellant gas velocity, atmospheric these variables in turn is evaluated cost
there
of
Selection
For fabrication of a flexible joint and selected for the elastomer, reinforcement,
and
by ultrasonic
Regardless of the manufacturing method, of unbonding that will result in a leak.
operating conditions ozone content), in a tradeoff study
vehicle
and motor
4O
The motor
to be and
choice of pressure,
(e.g., propellant gas temperature, and the envelope available. Each of involving range, payload, reliability,
performance.
2.1.3.1 The
ELASTOMERS
important
reproducibility the selected
properties
in the
elastomer
selection
are
the
shear
modulus,
shear
stress,
of these properties from lot to lot, and the ease of bonding the elastomer to reinforcement material. Since it has been demonstrated that the joint spring
torque could become zero because of axial compression, efforts determine shear properties with superimposed compression (ref. 78).
are
being
made
to
The joint spring torque is directly proportional to the elastomer shear modulus (sec. 2.1.2.1.1). In the selection of an elastomeric material, the aim is to use an elastomer with as low a shear modulus as possible and with a minimum of continued feaction of the components have been
(sec. 2.1.2.5.2), developed with
which secant
will increase shear moduli
shear modulus. (sec. 2.1.7.1)
Natural-rubber ranging from
formulations 20 psi (0.138
MN/m 2) to 35 psi (0.241 MN/m 2) at 50 psi (0.345 MN/m 2) shear stress. The low required shear modulus has presented difficulties to the elastomer formulators in preparing formulations that fulfilled the chemical stability requirement. The
shear
pressure specified
stress
in the
elastomer
is caused
by vectoring
and
usually is the more significant. Successful joints quadruple-lap shear stress (sec. 2.1.7.1) of
the requirements of shear modulus and shear stress, most joints have been of natural rubber or polyisoprene formulations. The joints of both stages of the motors are natural-rubber formulations, either GTR 44125 or TR 3005 (refs. 98
and
The
the 260-in.
all failures
(6.604
were
motor
To meet fabricated Poseidon
for
and
Of these,
having a minimum MN/m 2) have been
manufactured,
joint
tested,
pressure.
designed,
99).
and
motor
using elastomers 500 psi (3.45
m) motor
cohesive.
(ref.
22)
and
a joint
designedto
operate
at 3000 psi (20.7 MN/m 2) to + 15 ° at 300 deg/sec (ref. 14) used GTR 44125 elastomer. Required properties for these elastomers are minimum shear stress of 500 psi (3.45 MN/m 2) and secant shear modulus (at 50 psi (0.345 MN/m 2) shear stress) of 22 psi (0.152 MN/m 2) to
26
psi
(0.179
MN/m 2)
for
GTR
44125
and
18.5
psi (0.128
MN/m 2) to 24
psi (0.166
MN/m 2) for TR 3005. Actual shear strengths for these elastomers are greater than 1000 psi (6.9 MN/m 2 ) (ref. 100) for GTR 44125 and 660 psi (4.55 MN/m 2 ) for TR 3005, all failures being cohesive. m) motor (ref. motor (ref. 18). those of the
Polyisoprene elastomers have been used for the joints of the 156-in. (3.962 23), the 100-in. (2.54 m) motor (ref. 19), and an advanced dual-chamber The polyisoprene elastomers demonstrate shear properties that are equal to natural-rubber formulations but the shear modulus is greater, being
approximately used for joints
27 psi (0.186 MN/m 2) minimum. Natural-rubber when the minimum expected operating temperature
(283 process than
K). Because controls 10 psi (0.070
of the
difficulty
are maintained MN/m
A neoprene/polybutadiene between -40 ° F (233
in making to ensure
an elastomer
a lot-to-lot
with
variation
formulations have been was not less than 50 ° F a low shear
in shear
modulus,
modulus
close
not greater
2 ).
formulation has been bench tested K) and 165 ° F (347 K) at an equivalent
41
jJ
in a joint designed to operate motor pressure of 2550 psi
(17.6 MN/m 2) to + 17.5 ° at 360 deg/sec (ref. 85). Required secant shear modulus (at 50 psi (0.345 MN/m z) shear stress)
properties of the rubber were a of not more than 50 psi (0.345
MN/m 2 ) when the shear strength was greater than 600 psi (4.14 MN/m 2 ), and a secant shear modulus that could decrease linearly to 25 psi (0.172 MN/m 2) at 300 psi (2.07 MN/m 2) shear were
stress; these values achieved over most
secant
shear
Silicone
modulus
elastomer
apply over the required temperature range. The required values of the temperature range except at -40 ° F (233 K), where the
was 72 psi (0.496 formulations
MN/m 2).
that
are
satisfactory
for use in flexible
joints
from
-40 ° F
(233 K) to 165 ° F (347 K) have been developed (ref. 85), but these elastomers are difficult to bond to metals. The best bonds have been achieved with steel, but even these bonds demonstrated adhesive failures. The failure adhesive shear strength for silicone elastomers varied
from
250 psi (1.72
MN/m 2 ) to 560 psi (3.86
25 psi (0.172 MN/m 2) to 40 psi (0.276 associated with the higher strength. These applications (dimethyl silicone formulations (208 stress
allowable shear require thinner
joint
an envelope
to have
2.1.3.2
strengths elastomer
with
a cone
modulus
at -160 ° F (166 K). The induced upon elastomer ring thickness,
are less for silicone formulations, layers. The shear stress is minimized angle
yield with
of approximately
zero
have
been
fabricated
with
steel
reinforcements
important stress, which
properties
in the
selection
of
ultimate and yield tensile stress, elastomers can be bonded to
degrees
(ref.
17).
and
with
composite
the
reinforcement
as ease
material
epoxy
are
resin
compressive
modulus of elasticity, ease of fabrication, the material, and cost' of the material.
of fabrication
stresses
in
a
and
cost became
reinforcement
are
a
the dominant factor stresses are relatively
ease For
with
unbonding
between
the
in selecting materials. For low (ref. 17), and factors
important. tensile
hoop
stress
compressive hoop stress on the inner radius (sec. 2.1.5.2) vectoring. Failures in the reinforcements have always occurred stress is compressive. For joints with steel reinforcements, wrinkling
reinforcements. and 25).
reinforcements, the interlaminar shear stress is also an important property. In the selection of material depends on the joint envelope. For joints with a large cone
angle, the mechanical properties have been conical envelope joints, the reinforcement
The
shear and
REINFORCEMENTS
composite addition
such
from
joints using these by designing the
The composite reinforcements have been formed with S-glass filaments (refs. 27, 28, and 29) and S-glass filaments and phenolic resin (refs. 24 and The
varied
MN/m2), the higher modulus generally being elastomers have been used for low-temperature have a glass transition temperature at -85 ° F
K), and methyl-phenol silicone formulations, due to motor pressure is directly dependent
because the formulations
Joints
MN/m 2 ); the shear
elastomer
42
and the
on
the
outer
radius
and
a
due to motor pressure and at the inner radius, where the the failure appears as a local
reinforcement,
so that
the joint
is
no longer a pressure seal. The wrinkling proceeds circumferentially around the reinforcement in a high-frequency wavepattern. For joints with compositereinforcements, the failure has appearedas rupture acrossa reinforcement thickness(ref. 27), interlaminar shear failure between different types of lamina in the laminate (ref. 28), or compressive failure (ref. 25). Correlation of test data for metal reinforcementswith calculatedresults(ref. 17, pp. 14-48, and sec.2.1.5.2) indicates that the stressat failure is the compressiveyield stress.However, buckling as a possible failure mode cannot be discounted. The failure buckling stressis dependent on the reinforcement dimensions,compressiveyield stress,and the modulus of elasticity (sec.2.1.5.2). The reinforcement material selectedaffectsthe bond to the elastomer.Elastomersthat have failed cohesivelywhen bonded to steelhavefailed adhesivelyat lower stresseswhen bonded to aluminum. Although it has been shown analytically that aluminum could be usedas a reinforcement material, it has not been usedin any joints. Joints that were fabricated with natural-robber elastomersand either epoxy-resin composites or phenolic-resin composites have never shown failure at the bond between the reinforcement and elastomer during bench testing. The joints of the motors on both stagesof Poseidoncontain 4130 steel heat treated to 180000 psi (1241 MN/m2) ultimate tensile stress,and the 260-in. motor (6.6 m) (ref. 22) incorporates4130 normalized steel. The joints of the 100-in. (2.54 m) motor (ref. 19) and 156-in. (3.96 m) motor (ref. 23) used304 Condition-A stainlesssteel,and the joint for the advanceddual-chambermotor (ref. 18) used 17-7PHannealedstainlesssteel. All of these joints have been bench tested successfully to pressuresin excess of ultimate design requirements. The first joints with composite reinforcements used continuous hoop-wound S-glass filaments with ERL 2256/Tonox 6040 epoxy resin to provide hoop strength and stiffness (ref. 27). During bench testing, these reinforcementsfailed transverseto the windings, thus showing a need for transversestrength. The transversestrength was provided by S-glass filament mats laid up between the continuouslywound S-glassfilaments (ref. 34), the mat filaments being oriented at an angle acrossthe hoop windings (refs. 27, 28, and 29). Joints with these configurations exhibited a changein the reinforcement failure mode and an improvement in joint strength when bench tested. To reduce the fabrication costs of composite reinforcements and to improve processcontrol, joints were fabricated with closed-die compression-molded reinforcements consisting of FM 4030-190 (phenolic-preimpregnatedS-glassroving) chopped into one-inch lengths (ref. 24). These joints were bench tested and static fired. Early joints for all three stagesof the Trident I (C4) engineeringdevelopmentmotors were fabricated with reinforcements of S-glasscloth preimpregnatedwith phenolic resin (ref. 25). Thesejoints were successfullybench tested, and static firings with vectored nozzles were conducted successfully on second-and
43
third-stage motors. However, in the motor development program structural problems occurred in the reinforcements in flightweight joints. The resin systemwas changed from phenolic stiffness
to an epoxy resin, data have not been
2.1.3.3 For
ADHESIVE
test
joints
BOND with
formulation by injection
intended molding
205
and
primer
specimens overcome
The
steel
for operation or compression
even though by ensuring
adhesive
SYSTEM
either
Chemlok
layer thickness reinforcements
and no further problems occurred. Fundamental strength and generated for the composite materials used in reinforcements.
220
the that
for
composite
between molding,
adhesive.
The
reinforcement
bond
failed
at low
(sec. 2.1.6.2). Applying in which failures always
the joint
with
and
65 ° F (291 K) and the adhesive system
surfaces of the steel were carefully the material lots were of sufficient
was controlled resulted in joints system
or
secondary
a
natural-rubber
85 ° F (303 K), fabricated has consisted of Chemlok strength
levels
in steel
test
prepared. This problem was quality and that the adhesive
the same controls to composite occurred in the reinforcement.
bonding
consisted
of a primer
system
for
the reinforcements, FMC 47 epoxy resin, and Chemlok system is a high-temperature system. After the primer
305 adhesive (ref. 22). The primer was applied to the reinforcements,
the reinforcements was cured during
adhesive,
The
adhesive
formulation compression
were cured joint molding.
systefh
for operation molding, was
with this system silicone rubber dissolved cohesive
2.1.3.4 The
joint
for test
specimens between Chemlok
with
K).
The
steel plates
Shear failures with K) and -40 ° F (233
THERMAL
thermal
protection
and
an ambient-cure
this system K).
system was were
fabricated by Shear failures
for test specimens with a 75 percent Chemlok 608
adhesive
at 165 ° F (347
K) and
PROTECTION has
been
effected
either
by insulating
boots
or by
thermal protectors (sec. 2.1.2.5.1). The important properties for thermal-protection materials are a low thermal diffusivity, high heat of ablation levels anticipated in temperatures expected
adhesive,
neoprene/polybutadiene-rubber
-40 ° F (233 K) and 165 ° F (347 K), 205 primer and Chemlok 231 adhesive.
were cohesive (ref. 85). The adhesive formulation for the same environment
in methanol. at 70 ° F (294
JOINT
at 300 ° F (422
service, and in service.
mechanical
flexibility
with
minimum
char
sacrificial
the under fracture
joint strain at
The choice of insulating boot material depends on whether the boot is protected by a radiation shield (fig. 7(a)). For insulating boots protected by a radiation shield, K1255 silicone rubber has been used. For joints with exposed insulating boots, materials have been
44
DC 1255 reinforced with chopped asbestosfiller to reinforce the char layer (reL 18) and silica-filled butadiene acrylonitrile rubber (refs. 13, 14, 19, and20). All of thesematerials have performed successfully,but they haveincreasedthe joint spring torque (sec.2.1.2.5.1). The sacrificial thermal protector materials have been either S-glass/phenolic-resinor carbon-cloth/phenolic-resin composites. The molded S-glass/phenolic-or epoxy-resin reinforcements (sec. 2.1.3.2) included the protectors in the molding (ref. 24). The carbon-cloth/phenolic-resin protectors were fabricated as an integral part of S-glass/phenolic-or epoxy-resincomposite reinforcements(ref. 25). Both of thesematerials have performed successfullyin static firings (refs. 24 and 25) without causingan increasein joint spring torque.
2.1.4
Mechanical
2.1.4.1
GENERAL
A flexible-joint dozen other
CONSIDERATIONS
configuration has been flown joint configurations have been
firings (refs. mathematical
The derived
performance.
These
Torsional Effect
design from
of pressure
Reinforcement
at zero
modified
To
establish
because the
joint
the
expected
pressure stiffness
- Section
2.1.2.1.1
- Section
2.1.2.1.1
- Section
2.1.5.1
Section
2.1.5.2
thickness steel
reinforcements,
according is analyzed
a joint properties joint
the
initial
component
relationships. An improved of analyses (refs. 17, 79 through
design
to
the
results
of the
96). However, no with test results
developed preliminary
in this monograph
thickness
the preliminary-analysis finite-element methods modified
flexible joint is data, to establish
are presented
on torsional
layer
with
of a limited
relationships
stiffness
Elastomer
design
on an operational vehicle, and approximately a either bench tested or demonstrated in static
13, 14, 17 through 20, 22 through 29, 95, and equations have been developed that correlate
configurations. relationships,
For joints
Design
from simple dimensions
general for all
empirical and joint
as follows:
dimensions
are established
from
analysis is then conducted with 82, and sec. 2.1.5.3), and the joint
finite-element
analysis.
If necessary,
the
again. with
composite
of the composite dimensions.
The
reinforcements, were
elastomer
45
unknown. layer
a different A joint thickness
method
is designed and
and
number
has been
used
fabricated of
elastomer
at
layers are calculated according to proceduresin section 2.1.5.1. The reinforcements are designed according to procedures in section 2.1.5.2, maximum strength at failure being assumedto be 60 000 psi (414 MN/m 2). To establish the allowable composite strength, the joint
is pressure
tested
to
failure
without
vectoring
preliminary analysis of section 2.1.5.2 and The allowable composite strength is defined regardless allowable methods.
of the joint mode composite strength
2.1.4.1.1
Design Definitions
and
the
results
correlated
with
the
a detailed finite-element analysis of the joint. as the calculated reinforcement stress at failure
of failure. The joint design is modified in accordance with this at ultimate load conditions and analyzed by finite-element
The design of a flexible joint usually is established and then defined on the basis of the relationship between the loading conditions that will be imposed on the joint and the capacity of the joint to withstand these loads. Limit load, design factor of safety, design load, allowable load, and margin of safety to this relationship between joint loading are used Limit or
in this monograph,
load. service
-
The
limit
pressure
3-standard-deviation physical variables motor or combination Design applied
pressure)
load that
is the can
in the
specified
expected
vehicle, or (3) the maximum of 3-standard-deviation limits
quality,
and
load
load (or pressure). and the
following
maximum be
design terms that loading capacity.
to
design
or calculated occur
value
under
load
(or
-
and of the
design safety factor is an arbitrary multiplier greater thart for design contingencies (e.g., variations in material properties,
1
design
motor or vehicle operating limits and specified operating limits.
load
maximum
a
- The
stress).
the
all environmental operating limits
within load
the
defined
structure).
(or pressure)
is the product
of the limit
load
(or
of safety.
Design stress. - The design stress is the stress, in any structural element, application of the design load or combination of design loads, whichever the highest stress. Allowable
of a service
(1)
by
distributions
factor
are used with respect These terms, as they
paragraphs.
operating limits of the motor or vehicle including that influence loads, (2) the specified maximum
safety factor. -The in design to account
fabrication Design
are defined
are joint and joint
The
allowable
load
the slightest, produces joint failure. Joint failure failure, whichever condition prevents the joint Allowable load is sometimes referred to as criterion
46
(or stress) may from load
is the
be defined performing or stress.
load
resulting condition
that,
from the results in
if exceeded
as yielding its intended
or ultimate function.
in
Margin of safety. - The margin of safety (MS) is the fraction stress exceeds the design load or stress. The margin of safety MS
where
R is the ratio
2.1.4.2
DESIGN
Ideally,
the design
of the design
SAFETY safety
overall
factor
factor
All flexible-joint loads as defined
The
•
Motor
•
Vectoring
•
Vehicle
•
Handling
motor
joint. rings.
loads above.
tensile
would
be calculated
stresses
motor
modulus
load
or stress.
from
a knowledge
of the
randomness
is designed
to a safety
factor
of
there to the
sufficiently engineering requires an
of 1.5.
LOADS used in the flexible-joint The loads on the flexible
and
storage
acts
during
structural analysis (sec. 2.1.5) joint are those that result from
are
design
flight
conditions
as a crushing
pressure
tensile and compressive the compressive hoop
and
also
causes
an axial
compression
on the
hoop stresses are developed in the reinforcement stress in the reinforcements is more critical than the
....
pressure.
is dependent
As a result
of vehicle
section
the
of
the joint
accelerations
Vectoring of the joint reduces these stresses with
to the allowable
pressure
pressure
Significant In general,
or
(5)
required reliability and confidence levels. Unfortunately, of the relationship of the assumed failure criteria
of 1.25,
FLEXIBLE-JOINT
load
1
stress distributions in a joint, and the methods of analysis are not At present, a safety factor is established largely on the basis of combined with experience. As an example, if the motor specification safety
2.1.4.3
or stress
the allowable as
FACTOR
the design variables and the is insufficient understanding complex accurate. judgement
load
1 R
by which is defined
nozzle
increases the reinforcement hoop stresses on one side of the joint and on the other. Shear stresses induced in the elastomer rings increase Vectoring on strain accelerations imposes
rate
affects
the
elastomer
shear
stresses
since
the
shear
rate. during loads
on
launch, the
47
joint.
flight, These
or staging,the loads
can
mass cause
of the movable all the
stresses
induced by motor pressureor vectoring and, in addition, can causean axial tensileload on the joint. Usually the stressesdue to vehicle accelerationsare not critical conditions. Handling
and
storage
During handling joint, since such
2.1.5
conditions
and loads
Structural
The structural reinforcement
The
analysis thickness,
ELASTOMER
stresses
in the
all the
stresses
induced
by the
tensile from
previous
conditions.
loads are imposed the reinforcement.
consists and the
of the determination finite-element analysis.
to determine stresses.
internal
of the elastomer thickness, the All structural analyses consist of
stresses,
and
a strength
analysis
comparing
THICKNESS elastomer
are
caused
due to vectoring is approximately thickness of elastomer (i.e., number
by vectoring
and
constant in the of elastomer rings
motor
elastomer x thickness
pressure.
rv
=
0.01745Go
The
shear
on the joint spring due to vectoring is
Rp 0
(6)
_nte
where rv = shear
stress
due
to vectoring,
psi (N/m 2)
(eq.(1)),
Go
= secant shear modulus at 50 psi (0.345MN/m psi (N/m 2 ), at the elastomer temperatures
Rp
= pivot
radius,
0 = vector
angle,
n = number te
= thickness
Angle 0 is expressed
numerically
2 ) shear stress (sec. expected in operation.
in. (cm) deg*
of elastomer
layers
of individual in degrees,
elastomer
not radians,
layer,
in this empirical
48
stress
and depends on the total of each layer) and not the
thickness of each ring.: The induced stress due to vectoring is dependent torque, decreasing as the joint spring torque is reduced. The shear stress given by the expression (ref. 23)
and, as before
on the
Analysis
two parts: a stress analysis internal stresses to allowable
2;1.5.1
cause
storage care is taken that no axial can cause debonding of the elastomer
in. (cm) expression.
2.1.7.1),
The shearstressdue to pressureis dependentupon the thicknessof eachelastomerlayer and is givenby the expression(ref. 79)
re =
te Pc Ke Rp 2
(7)
17.5
where rp = shear
stress
Pc
= motor
Ke
= correction
Calculated
results
17). The
correction
in figure
18.
due
pressure,
have
factor
shown
factor
1°0
to pressure,
psi (N/m 2)
psi (N/m 2 ) for elastomer
that
stress,
the shear
Ke has been
derived
stress
depending
increases
from
the
upon
cone
as the cone
results
angle.
angle
of reference
n
O l.I
0.6
O 4-1 4.1
0.4 0
0.2
0
I
I
I
I
I
I0
20
30
40
50
Cone
angle
_ , deg
Figure 18. - Shear-stress correction factors related to cone angle (ref. 17).
49
(ref.
17 and is shown
_d
t_ q4
increases
The resultant pressure, i.e.,
shear
stress
Zr in the
elastomer
is the
sum of the stresses
due to vectoring
r_ = r_ + rp The
resultant
stress
is compared
shear
stress
the
been
considered
(8)
allowable
shear
The
allowable
from have
a quadruple-lap shear specimen (sec. 2.1.7.1). ignored the increase in failure shear stress due
stress in an elastomer criterion is not known. the The
increase
is a complex Until the failure
in failure
following
shear
procedure
Calculate the shear stress due to the maximum various elastomer layer thicknesses.
(4)
Calculate
the
net
(5)
Determine
the
design
(6)
Plot
axial mode
design
loading
stress
ultimate
ultimate
is
of
shear
a design using the
stress to date state of
associated whether
failure ignoring
thickness:
elastomer
due to vectoring
shear
shear
required
expected
elastomer
shear
stress:
stress
as a function
ru_t
stress
parameter, calculated
spring
torque
(sec.
rv.
rr at various
shear
for
=
operating
layer
of elastomer
the axial thickness,
rp for
thicknesses.
rr X design
to determine
pressure
safety
layer
the
factor
thickness
maximum
and
allowable
deflection is calculated and compared with
by the
The elastomer thickness may be reduced if the axial compression exceeds but the net radial thickness is maintained in order to satisfy spring torque The effect of reducing the thickness is to reduce the net shear stress and the
REINFORCEMENT
stresses
stress
it with the allowable layer thickness.
deflection, increase of the reinforcements.
2.1.5.2
shear
thickness
field, and the it is not known
elastomer
(3)
requirements. requirements, requirements.
radial
the
Calculate
the
net
to determine
measured
joints designed pressure. The
is conservative.
(2)
If axial compression finite-element methods,
these
is used
three-dimensional criterion is known,
due to pressure
minimum
All successful to superimposed
Calculate 2.1.2.1.1).
the
the
stress
stress.
to be the
(1)
compare elastomer
The
has
with
and
in the
the
number
layers,
and
affect
the
compressive
failure
THICKNESS
reinforcements
conditions,
of elastomer
each
are
caused
reinforcement
by cross
50
motor section
pressure rotates
and vectoring. but
does
not
For
both
significantly
of
\, ",\
change shape. reinforcement
Such rotation causes a bending stress distribution with tension at the outer radius and comPression on
compressive stress on outer surface, so that
the 'inner it is 0nly
radius has always been necessary to determine
13, 14, 24, 27 to 29, 101, and 102). fatigue charactei_istics and fracture stresses of equal concern.
For motors mechanics
radially the inner
greater than the tensile the compressive stress
across radius. stress (refs.
the The
on the 17, 22,
that will be operated a number of times, are considerations that make the tensile
\
The compressive reinforcements
hoop, stress (ref. 79):
due
to pressure
depends
on the
number
and
dimensions
of the
"\
ap
4087
-
Pc
Kr _2
n-1
(9)
where ap
= compressive
Kr
= correction
hoop factor
stress
due
to pressure,
for reinforcement
psi (N/m 2)
stress,
the
value
depending
cone angle (ref. 1'7). The correction factor Kr has been the results of reference 17 and is shown in figure 18. n = number
of elastomer
layers Rp
3283tr
/3,/31,/32 The
= joint
compressive
2-4
cos
of reinforcement
angles
hoop
stress
(fig.
as described
in section
from
2.1.5.1.
/3
3 + tr COS2 /3 {Rp 2 (/32 -
-- thickness
tr
determined
on the
derived
in joint,
/31 )2
_3283tr
2}
in. (cm)
12), deg*
due
to vectoring
Ov -
av is given
43950
0
by (ref.
79)
K_ £Z
(10)
n-1 Equations (9) and varied in diameter
(10) are empirical relationships from 8 in. (20.3 cm) to
relationships
not
/3,/31,
and
_2
have are
expressed
been numerically
developed in degrees,
for tensile not
radians,
51
derived from results of tests of joints that 22 in. (55.9 cm). Corresponding empirical stresses. in equation
When (9)
and
(10).
the
cone
angle
is large,
the
tensile stressesare only slightly less than the compressivestresses,but as the cone angle becomes smaller, the tensile stressdiminishes until the reinforcement is in a completely compressivestate (ref. 17). The resultant hoop compressivestressor stresses
due to vectoring
and pressure, Or
The net
stress
Failure
modes
and
bulk
or is compared for
compression.
windings only reinforcements compression.
The
allowable
(buckling material
=
the
The
failure
reinforcement
av
O'p
-k
allowable
reinforcements
is rupture fabricated
bulk
layers.
steel
with
in the
compressive
are buckling mode
stress
The
buckling
stress
in high-frequency
for composite
for metal
for
metal
on specimens slightly curved
that edge effects were negligible. thickness was varied, and different stainless 6061-T6
steel, 304 aluminum,
reinforcement
CRES and
material
reinforcements
The ratio reinforcement
of
depends
has
been
with
the
hoop
modes shear
failure
for and
mode
are
established
from
a test
surface of a joint. The column was long enough so
reinforcement materials were
dimensions
upon
waves
a function of the reinforcement and the thickness of the elastomer
stainless steel, 17-7PH aluminum. Results and
fabricated
thickness. The failure windings are interlaminar
reinforcements
1)
circumferential
reinforcements
representing the inside across the width, and the
annealed 7075-T6
properties
compressive
stress.
or bulk compression) and consequently is modulus of elasticity, reinforcement dimensions,
program conducted reinforcements were
sum of the
(1
across the reinforcement with mats and continuous
compressive
is the
i.e.,
thickness used: 301
CRES annealed of the tests shown
in
to elastomer CRES half-hard stainless correlated
figure
19.
The
steel, with bulk
compression stress has been established as the compressive yield stress (ref. 17). Tests were conducted on two joints with stainless steel reinforcements; the joints were identical except that the steel was heat treated to different yield compression stress levels. The failure pressures for the joints were different, and joint, calculated by finite-element methods, yield
stresses
The
allowable
test joints The
for the reinforcement
with
following
compressive composite procedure
the
stress
number
failed reinforcement of each equal to the compressive
materials. for
composite
reinforcements is used
the stress in the was approximately
that
to determine
reinforcements approximate
the reinforcement
(1)
Determine
of elastomer
(2)
Calculate the compressive hoop reinforcement thicknesses (eq. (9)).
52
layers stress
(sec. due
is often
the desired
established
joint
from
design.
thickness:
2.1.5.1). to
pressure
(Or)
for
various
l_/m
2
ksi
828
120
690
i00
552
80--
414
60
4.1
=
0
,-4
__
TEST
L_ GO
• 276
20
oV in.-ibf N-m
304
CRES
0 17-7 17 3ol c_s
40
138
DATA
units
units
0
7075
T6
A
6061
T6
I
I
I
I
I
2
3
4
3.32
6.63
9.95 E 1/2
t
5 x
13.26
16.58
3/4 r
1/2
t e
Figure
19. - Buckling
stress for
metal
reinforcements
as a function
of the
properties
and dimensions
of the reinforcement.
103 x
104
(3)
Calculate the compressive hoop reinforcement thicknesses (eq. (10)).
(4)
Calculate
(5)
the
thicknesses
(eq.
Determine
the
thicknesses: (6)
net
compressive
hoop
ultimate
compressive
design
the
=
or X design
buckling
Plot the function minimum
material
ADVANCED
Analysis
by
assembly, structural
The
with
test
limitations
theory
of
modified
properties, properties;
methods
hoop
the
technique
(refs.
the
finite-element
pressure
(ref.
been 80).
various
reinforcement
for various
reinforcement
for various yield
reinforcement
thicknesses
stress.
stress and intersection
the buckling stress as a of these plots is the
enough probably
to ensure that the failure results in over-strength
allows
in sections Results from
structures
to be analyzed
as an
2.1.5.1 and 2.1.5.2 analyzes the the finite-element method present a in an assembly. have shown good
results.
to account
has
stress
80 to 82)
method
load
that effects;
(1)
it is basically
(2) material
have been introduced (ref. structures such as a flexible
condition, obtained A
are
for large-deformation
during loading. Each of these in the elastomer are large strains;
motor
strains
stress
of the stress, strain, and deformation distribution of the assumptions in the method, calculated results
but depend upon the local stresses an axisymmetric loading condition, For
hoop
compressive
employed assembly.
although refinements and (3) for continuum
axisymmetric The strains
various
for
factor
the reinforcements thick However, this approach
the method forming the
complete description Within the limitations agreement
for
(Ov)
ANALYSIS
finite-element
whereas elements
vectoring
(or)
design ultimate compressive hoop of reinforcement thickness. The allowable reinforcement thickness.
It has been the practice to make mode will be bulk compression. reinforcements. 2.1.5.3
to
stress
safety
compressive
up to the reinforcement
(7)
due
(11)).
oult
Determine
stress
103) joint,
good
limitations affect the analysis of a flexible the elastomer material properties are not
correlation the
is applied
are elastic
to include nonlinear the structure must be
in the elastomer; and, although motor vectoring is an asymmetric condition.
with
small-deflection
properties
use to
54
with
axial
deflection
of an incremental the
initial
geometry;
pressure
and
loading the
joint. elastic imposes
reinforcement
and stress
deformation and
strain
distribution for that load are determined, and the shape for the next increment is established by algebraically adding the deflections to. the initial geometry. The final deflected shape is determined when the last load increment is applied; the final stressand strain distributions are obtained by summing the stressesand strains for each load increment. In generalin this analysisfour load incrementsgivea reasonablecorrelation with test results. Although the shear modulus of the elastomer is dependent upon the local stresses,a constant secantshearmodulus at 50 psi (0.345 MN/m2) shearstress(sec.2.1.7.1) is used for all loading increments. Other required properties are calculated on the assumptionthat the material is isotropic and hasa value for Poisson'sratio as closeto 0.5 as the computer can accept. Efforts to usean effective shearmodulus (sec.2.1.5.1)have been unsuccessful. For the vectoring condition, the joint cross section changes,extending on one side and compressingon the other. An analysistechnique similar to that for the motor pressureis used.Componentsof the actuator load are applied to the moving surfaceof the joint as a uniformly distributed axial loading, sinusoidally distributed shearloading, and a linearly varying bending distribution acrossthe joint diameter.An increment of loading is applied as before to determine the geometry for the next increment. The stresseson one sidewill add to the stressesdue to motor pressureand subtract on the other. Only the geometry for that sidewhere the vectoring stressesadd is usedin the next increment. The geometry for that sideis assumedto be axisymmetric, andthe loadsare applied incrementally. Final geometry and stress distribution are determined as described in the preceding paragraph;material properties aspreviouslydescribedare used. Net stressesdue to motor pressureand vectoring are obtained by algebraically adding the stressesdue to eachload condition. The strength analysisfor the elastomeris conductedby comparing the maximum principal shear stress to the minimum measuredshear stress measuredfrom a quadruple-lap shear(QLS) specimen(sec.2.1.7.1). The strength analysis for the reinforcementscomparesthe maximum compressivehoop stresson the inner radius to the allowable compressivestress(sec.2.1.5.2). 2.1.6
The
Manufacture
sequence
reinforcements, elastomer, and
2.1.6.1
of
steps
for
fabrication
development of the molding of the joint.
of adhesive
a flexible system
joint between
involves the
manufacture
of
the
reinforcement_and_.the
REINFORCEMENTS
The joint reinforcements reinforcement material,
have been fabricated by a number of methods; and fabrication method are summarized in table
55
dimensional VII.
details,
TABLE VII. - Details of Reinforcements
Average spherical Motor
radius
Rp, in.
100-1nch
14.6
156-Inch
36.8
260-Inch
Conical:
Used in Flexible
Joints on Operational
Thickness tr, in.
and Development
Material
Motors
Fabrication
method
Ref.
304
Hydroformed
19
0.040
304
Spun
23
0.700
4130
0.038
normalized
Machined
from roll ring 22
forging
58 outer radius, 54 inner radius
Poseidon
C3 first stage
13.85
0.183
4130,
180 ksi
Stamped
and machined
95
Poseidon
C3 Second stage
13.69
0.108
4130,
180 ksi
Stamped
and machined
96
Dual chamber
5.75
0.060
17-7PH
NAVORD
7.18
0.110
4130,
13.69
0.108
Hoop-wound S-glass core overlaid with S-glass cloth
Poseidon
TMC/TVC C3 modified
second-stage
annealed 180 ksi
Explosive
formed
18
Machined
from plate
14
Compression
molded
27
and epoxy resin Trident I (C4) second-stage
10.34
0.050
S-glass and carbon cloth pre-impregnated
NAVORD
IRR
3.69
Notes: 1 in. = 2.54 cm TMC/TVC = thrust magnitude control/thrust vector control IRR = integral rocket ramjet
0.140
with
phenolic
resin
Chopped resin
S-glass/phenolic
Matched-metal molded
Closed-die molded
compression
compression
25
24
Steel
reinforcements.
been formed pressure was
-Hydroformed
reinforcements
by mounting an annealed circular applied to the plate, it expanded
for the
plate into
100-in.
(2.54
m) motor
in a pressurizing fixture (ref. 17). When an ellipsoidal shape. The reinforcement
was then machined from the expanded plate and heat treated to the required The spherical radius for each reinforcement in a joint was controlled by varying to which the plate was expanded. The reinforcements for the 156-in, reduce costs, all the reinforcements
have
(3.96 m) motor (ref. 23) were formed were spun from a standard conical
properties. the height
by spinning. To preform, welded
from three standard patterns that were cut from only one standard template. After welding, the conical preforms were stress relieved and pressed onto a mandrel in a horizontal shear spinning machine. Spinning was conducted in each direction from the center. The center of the reinforcement received the least section. After spinning was completed, finish
machined.
Reinforcement
amount of cold working and remained the thickest the reinforcement inner and outer diameters were
thickness
was
controlled
by measuring
the
thickness
of the
conical preform prior to installation on the mandrel, and estimating the amount of thinning required. Thinning was accomplished by belt sanding for a predetermined time after the reinforcement was formed. This method assured that each reinforcement received the same amount of cold reinforcement. In the
260-in.
thick,
the
working
(6.6
large
m)
by
motor
diameter
shear
(ref.
resulted
spinning
and
resulted
22), although in flexible
the
sections.
in a uniform
strength
reinforcements The
were
reinforcements
level
for each
0.7 in. (17.8 were
not
mm)
spherical
sections as in all previous joints but were conical sections. Since the joint envelope was cylindrical, each reinforcement was identical and only a single set of tooling was required for all reinforcements. This design resulted in cost savings in comparison with a joint with spherical reinforcements of progressively increasing radii. The reinforcements were machined from roll ring forgings. Any distortion occurring in the finished reinforcements either due to machining or handling was easily corrected in the joint mold as a result of the flexibility of the large-diameter reinforcements. Reinforcements
for the
Poseidon
motors
were
fabricated
by
stamping
washer-shaped
into the required section; this process required a die for each reinforcement. the steel was in a normalized condition. After stamping, the reinforcements machined, heat treated to the required properties, and then final machined. results
in
distortion
of
the
reinforcements,
but
performance if each individual reinforcement 2.1.6.3). The thinner reinforcements formed forming have not exhibited this distortion. The
reinforcements
for
blank of material. The reinforcement, making
the
dual-chamber
this
distortion
has
little
At stamping, were rough This method effect
is aligned in the joint molding by hydroforming, spinning,
motor
were
explosively
formed
disks
on
from
a circular
blank was clamped over a die that had the required contour it necessary to have a die for each reinforcement in the joint.
57
joint
fixture (sec. or explosive
of the Due to
forming, the thickness of the reinforcement was 4 percent to 5 percentlessthan the blank thickness.The reinforcement was final machinedfrom the formed section. The reinforcements for the NAVORD TMC/TVC joint (refs. 13 and 14) were machined from plate material. Only a few joints wereto be fabricated, andthis method eliminated the need for expensivetooling. The plate material was in a normalized condition and the reinforcements were rough machined. After machining, the reinforcements were heat treated andfinish machined. Composite reinforcements.12-end roving glass filaments
Early composite reinforcements were fabricated with an epoxy resin (ref. 28). The reinforcement
was formed by hoop winding between two plates. This system transverse strength and was modified by overlaying the hoop-wound cloth. A better method of forming these reinforcements was
with S-901 cross section
resulted in insufficient core with $34/901 glass to "B-stage" (partially
polymerize) the hoop-wound core, lay up the cloth on the faces of the core, replace in a mold, and cure under pressure (ref. 28). In this procedure, the ERR-4205 resin system was used because this sytem could be hardened, reliquified, and final cured. The same technique and materials were used to fabricate composite reinforcements for an experimental second-stage
Poseidon
C3 joint
(ref.
In the engineering development reinforcements were fabricated broadgoods,
each
27).
program, from
preimpregnated
with
for the second S-904 glass-fiber phenolic
resin
(ref.
stage of Trident I (C4) the joint broadgoods and carbon-fiber 25).
In the
motor
development
program, however, to overcome structural problems, the S-904 glass-fiber broadgoods preimpregnated with epoxy resin. The two types of broadgoods were sewn together, into The
specific patterns, glass broadgoods
assembled in a matched formed the reinforcement,
joint thermal protection. different mold for each To reduce the cost for the NAVORD molded included
in closed-die the
this method
2.1.6.2 The
joint
joint
metal mold, and cured at 325 ° F (436 and the carbon broadgoods formed
Each reinforcement reinforcement.
and complexity IRR joint were
had
of composite made from
compression thermal
molds
protection.
(ref.
These
were cut
a different
spherical
radius,
reinforcement fabrication, chopped S-glass/phenolic-resin 24).
The
reinforcement
reinforcements
demonstrated
K). the
requiring
a
reinforcements compound
molding the
integrally feasilibity
of
of fabrication.
JOINT
ADHESIVE
adhesive
system
by compression or injection 260-in. (6.6 m) motor joint
SYSTEM may
be formed
molding, (ref. 22).
during
or it may
the
molding
be obtained
process
by secondary
58
,\
(
_
for joints bonding,
fabricated as in the
Rubber-to-metal
adhesive
high stresses the adhesive
bonds
a bond Systems
adhesive
(sec.
strength designed
unbonding thin, the
problem resulting
During
Failures
have
also
fabrication,
occurred
and
Flexible
wiped the conditions.
of joints
in the
inch
adhesive When
strength, so that have consisted
failures are cohesive of a primer and an
system has acceptance close
monitoring
(sec.
2.1.7.2),
bond
FLEXIBLE joints
have
failures
that
were
when
the
been obtained tests of each
liaison
the
do not have
adhesive
layer
is then
the
to too
thickness
was
as
with
viscosity
the
of
sufficient
by lot
controlling of material
adhesive
the
primer
suppliers. and
being
thickness be used
Thickness
adhesive,
and the time for quadruple-lap shear
strength
the to
the
of the in joint
control rate
has
at which
spraying. The material tests (sec. 2.1.7.1) and
rejected.
JOINT been
The compression technique between the reinforcements compression, balls between
attributed
in the adhesive system materials. from 3 lbf per linear inch (5.25
fabricated
by
three
different
methods:
compression
molding (refs. 17, 23, 25, and 27), injection or transfer molding (refs. 29), or secondary bonding of precured elastomer (ref. 22). A summary and disadvantages of these methods is presented in table VIII.
parts
the result was used,
N/cm).
are sprayed on the reinforcements, have been selected by conducting
all lots that
system off the reinforcement, a compression molding process
unbonding did occur. When the bond layer was below acceptable levels, and adhesive failures
adhesive
(61.25
maintaining by
these materials lots to be used
2.1.6.3
joint,
of the fabrication problems involve the adhesive system is required to
resulted from lot-to-lot variations specimens failed at values varying
adhesive requiring
obtained
tests,
In a flexible
occurred.
to 35 lbf per linear
A satisfactory adhesive layer,
peel
changes.
in this kind of system has been affected by bond layer thickness. too thick and an injection molding process was used to fabricate
testing
required. These failures For example, peel test
been
and the bulk reliability,
was not as acute but bond strength was
bench
layer
have
N/cm)
process
2.1.3.3).
the joint, the flowing rubber being unacceptable unbonded
thin a bond
to small
greater than the elastomer to satisfy this requirement
The strength of the bonds When the bond layer was
occurred.
sensitive
are imposed on these bonds, system. To ensure increased
develop failures.
the too
are
compressed
or layup
13, 14, 24, 28, and of the advantages
involves physically placing strips of partially cured elastomer as the joint is assembled in the mold. The resulting assembly of by
closing
the
mold
and
providing
molding
pressure.
During
the thickness of the elastomer layers has been controlled by inserting steel the reinforcements. In early joints, the balls were positioned at the center of
reinforcements.
As the
joint
was vectored,
9
the
balls
gouged
the
reinforcement
and
cut
TABLE VIII. - Advantages
Process
Injection
and Disadvantages
of Joint Fabrication
Advantages
molding
Processes
Disadvantages
Demonstrated production technique used to " fabricate joints for nozzles on Poseidon firstand second-stage motors. Has the potential of giving uniform rubberpad thicknesses. (However, in actual production of joints for Poseidon this method resulted in nonuniform pad thicknesses on many joints. The lack of uniformity seems to be associated with tool design and wear.)
Comparatively expensive process because of the complicated method of setup and fabrication. The tooling costs are much higher than those for compression-molded joints. Has inherent bonding problems. The elastomer must flow considerable distances over the reinforcements and end rings, and the flow of hot rubber tends to remove the primer or adhesive. This problem does not occur with silicone elastomer, because the primer/adhesive system can be precured on the components. Sometimes yields joints in which the rubber is not fully compacted in all areas. This condition results in joints that leak during the proof test and are therefore rejected.
0 Compression
molding
Demonstrated production technique used to fabricate joints for nozzles on Poseidon firststage and second-stage motors. Low-cost manufacturing process and simple low-cost tooling. Joints produced by this method are approximately 30 percent lower in cost than those produced by the injection process. When natural rubber or polyisoprene rubbers are used, excellent bonding between the rubber and the reinforcements and between the rubber
Secondary
bonding
Some difficulty with bonding and porosity attributable to the tolerance variation on calendered rubber. Some difficulty
in bonding
silicone elastomer.
and end rings in achieved.
Produces joints with very uniform nesses.
pad thick-
The rubber pads have good compaction can be inspected prior to assembly. Tooling
Spacers are required. The spacers sometimes move as a result of rubber flow, and uneven rubber-pad thicknesses can result. Furthermore, small local defects in the rubber-pad layers are created when spacers are removed.
costs are low.
and
Process has inherent
bonding
problems.
Production experience limited. To date only a few joints have been fabricated by this process.
holes than
in the elastomer. In later that of the elastomer, the
joint
and
The
injection
were
removed
after
molding
technique
that holds them the reinforcements. The
molding
in position
method
joints balls
where the width of the reinforcements were positioned at the inner and outer
was greater edges of the
molding. consists
and
selected
have been used for the same occurred have been common
then
injecting
depends joint to
simply
of stacking
rubber
from
on the
preference
design and compression
produced molding
the
reinforcements
a reservoir
into
the
of the fabricator; similar results. and injection
in a mold gaps between
both
techniques
Major problems molding. The
that three
major problems have been porosity in the elastomer, variation in the thickness of each elastomer ring, and variation in the thickness between elastomer rings. Porosity in the elastomer occurred because the elastomer could flow .easily out of the mold or into large voids
in the
minimizing Variation
mold.
This
problem
was
eliminated
clearances between metal in the thickness of elastomer
clearances variations.
by
designing
a mold
without
voids
and
parts to avoid elastomer expansion out of the mold. rings has been due to a number of causes. Excessive
in the mold to accommodate parts with Thickness variations have also occurred
excessive because
tolerances has caused thickness of movement and deflection of
the joint under the high pressures of molding. Tolerance problems are avoided if the pad thickness is controlled directly by the two metal surfaces involved; this procedure minimizes the number of tolerances involved in a worst-on-worst situation. The deflection of parts can be reduced
only
by
specifications. In Movement of the surfaces that are variations inspected uniform
stiffening
the
in an elastomer
layer
for flatness and spherical elastomer layer thickness.
was cheaper (ref. 22). As bonded to the reinforcement.
axial
correct alignment. at 5 psi (0.0345 pressure
but
for a joint
The secondary bonding technique because of a lack of sufficiently
ensure loaded
parts,
stiffening
may
be impossible
because
of design
such a situation, the deflection must be tolerated and allowed for. parts in the mold, however, has been controlled by indexing parts from self-centering, i.e., conical or spherical surfaces. To avoid thickness
was
radius
with
thick
reinforcements,
variations
and
are
the
aligned
reinforcements in the
has had limited application. It was used large facilities to cure at high temperature
each reinforcement Care was taken
was laid in the during the layup
to
ensure
good
adherence
between
to give
on a large joint and because it
mold, the elastomer of the reinforcements
An ambient cure adhesive was used (sec. 2.1.3.3) MN/m 2) axial pressure by mechanical actuators
used
mold
are
the
and the joint during cure.
elastomer
and
was to was The metal
components. Two important diagnostic aids exist in joint manufacture. These aids have assisted in the discovery of manufacturing problems and the determination of the effectiveness of corrective actions. The first diagnostic aid is molding of a joint without applying the adhesive
system
to the
metal
parts;
with
this exception,
61
the
molding
process
is carried
out
normally. After molding, the rubber is easily removed from between the metal parts and examined for thicknessand porosity. The secondaid is simply the dissection of a normal, production joint by cutting through the rubber between metal parts; the resulting pieces reveal any areaswhere the rubber-to-metal bond was unsatisfactory. This technique also showsporosity andgeneralcondition of the rubber.
2.1.7 The
Testing
•
flexible-joint
test
program
is conducted
to determine
elastomer
material
characteristics,
joint spring stiffnesses, nozzle operating characteristics, and nozzle failure strengths so that compliance with motor requirements is demonstrated. If new elastomeric materials are to be considered, a material characterization program is conducted (sec. 2.1.3). The test program consists of subscale testing, joint bench testing, nozzle actuation testing, static firing testing, joint
aging
2.1.7.1 The and
testing,
frequency-response
SUBSCALE
TEST
subscale test program of the bond between
of the elastomer. in the
the test
specimen
most
same
modulus, the reinforcements.
manner
of test
as the
specimens,
surfaces
of the
the
of the
in the manner
properties
used
operation, in terms
!_, -: _._
:,
_
modulus ._
Go
=
elastomer
used
in the
with the quadruple-lap of the test as follows:
shear
strain
applied stress
r
Shear
strain
_/
=
2 × length
increase
in crosshead
2 X thickness
62
flexible
shear
of pad
separation of pad
joint
(QLS)
are
specimen
stress
MN/m 2 ) shear
load
× width
must
be
if possible,
of the joint.
MN/m 2 ) shear
at 50 psi (0.345
test plates
in the joint;
the
shear
of the elastomer to the metal range of temperature in the
-
Shear
of the
for manufacture
50 psi (0.345 Shear
surfaces
reinforcements
shear stress at failure, and the bond strength These properties are measured over the
elastomer expected during The properties are defined
'
testing.
is conducted to measure mechanical properties of the elastomer elastomer and reinforcement and to evaluate aging characteristics
is fabricated
important
and destructive
PROGRAM
In the preparation
prepared
The
testing,
stress
(fig. 20).
(7.62
cm)
3 in_ 118
i/8
in.
(3.2
(2.54
nun)
•v ---- f I: Ii
cm)
(2.54
I
I
I
II
I.!. '
J
i
II
N"////A l I
in.
cm)
(3.2
n-_) I
I/I///A,_
IlI l l----I"_Elastomeric for
material
test I in.
---_
I
Figure
Even
though
sufficient properties
the
elastomer
Shear
movement. reference
modulus The secant
- Quadruple-lap
in a joint
characteristics joint instability,
determine elastomer shear tension have been conducted The
20.
motor pressure, and have been determined
of the physical pressure, overall
,
I
cm)
shear test specimen.
is subjected
to compression
and
of flexible joints and nonlinearity
if vectored
at
(the reduction in actuation torque with of axial compression), limited efforts to
the
joint
spring
torque,
to superimposed
axial
compression
deflection,
stress-strain response is nonlinear, but most analyses shear modulus at 50 psi (0.345 MN/m 2 ) shear stress;
for quality control. necessary to ensure
shear
to tension and shear if vectored at zero motor pressure, the only for applied shear loads. To improve the understanding
properties when subjected (refs. 22 and 78).
controls
I__
and
and
pivot-point
assume linearity at a this value is also used
The elastomer varies from lot to lot, and close quality control a modulus acceptance range of 10 psi (0.069 MN/m 2). In a production
is
program, the testing of each lot can indicate a relaxation of manufacturing quality control or a change in the manufacturing process. The QLS is used as a quality control tool aS well as a means to qualify new elastomers and new adhesive systems. If the aging characteristics of the elastomer are not known, a subscale test initiated early in the program. This program includes testing not only characteristics of the cured elastomer but also the effect of aging of the uncured on the resulting cured elastomer. in a program, the results of joint
'
When such effects are not determined tests are subject to misinterpretation.
63
program is the aging elastomer
and controlled
early
In evaluating the aging of uncured material storage environment and,
elastomer, at intervals,
the uncured elastomer is stored test specimens are prepared and
in the cured.
usual Tests
are conducted, and the shelf life of the uncured elastomer is determined from the results. The selected shelf life is the time during which no change occurs in the secant shear modulus of the cured elastomer. To
evaluate
stored
aging
in the
characteristics
of
environment
and,
motor
cured
material,
at intervals,
elastomer properties are plotted against time, service life of the elastomer. Properties obtained Service life testing thereafter. Results modulus When
up to 3½ years a joint
therefore elastomer
and
is injection
2.1.7.2
by testing
BENCH
joint
bench
test
then
elastomer
a subscale
test
remain the
from
program
and the results are at zero time provide
monthly intervals up to natural-rubber formulations
several
lots
conducted.
is
The
extrapolated to predict a basis for compariso/_. 6 months and annually increase in secant shear
constant. test
specimen
elastomer aging joint. The aging
full-scale
TEST
at that
molded,
the measured in the full-scale
are assessed
The
is conducted have shown
cured
cannot
be fabricated
characteristics characteristics
in similar
may differ from of injection-molded
fashion;
those joints
of the usually
joints.
PROGRAM program
is conducted
to determine
axial
compression
due to pressure,
spring torque, offset torque, sealing capability of the joint, and the location of the effective pivot point; to verify calculations; and to demonstrate structural integrity of the joint. Thus data must be obtained as early as possible in a program to confirm clearance envelopes in the nozzle continued
design. When a program for quality control.
The
compression
axial
clearance the joint
envelopes. is expected
is in the
is required
to
production
determine
phase,
the
axial
the
spring
The bench testing is conducted at the same to transmit during actual motor operation.
bench
stiffness
test
program
and
to
is
check
pressure and axial load This condition requires
as a
special test fixture, as shown in figure 21, that contains provisions for adjusting the axial load on the joint. An unloading piston is used for this purpose. The unloading piston is sized such that the net axial load on the joint at pressure while undergoing test is equal to the load load
that will be imposed on the joint during acting on the joint during motor operation
During
the
development
axial compression analyses. The
quality
program,
of joints to eliminate
are
tests,
hoop
measured.
These
in a production possible
strains
at the
data
program
low-quality
actual motor is calculated are
of the reinforcements
of value
varies
joints
64
edges
and
operation. The net gas-pressure as described in section 2.1.2.3. in checking
considerably ensure
from the
the
joint
reliability
as well validity
to joint. of the
as the of the
In one motor,
a
Unloading
piston
Flexible
joint
UnloadingA
cross
I Un loadi_J_
cross
_J"
_Pressure
_--T-""_/_
_Post
I
pis ton
bar vessel attached
pressure |
piston bar
(pressure unloading reacted
See.
to
A-A
vessel acting
on
piston by post)
Figure 21. - Special fixture for testing joint axial deflection.
stringent after the pressurized extension leakage. successfully tested.
tensile-pressure leak test was imposed. This test was an axial tensile axial compression and vectoring tests. The joint was sealed with internally, of the joint, In the
motor
passing
the pressure causing axial b_t pressure was still applied program,
this_ 'J_
leaky
_, no
joints
failures
were
attributed
pressure effective
is less than pivot point.
the motor Attempts
rejected
after
to joint
this test but,
failure
occurred
for those in the
simulating the test
The reduced pressure affects the position an unloading-piston test arrangement that
65
joints motors
end o£ the joint, is sealed _into the closure that is connected to an more axial load is applied to the
Therefore, joints are tested only up to a pressure will be applied to a joint in the motor. Consequently, pressure. to design
conducted plates and
extension. The test fixture limited the at maximum extension to check for any
A typical join t_iest arrangement is shown in figure 22. One test bucket and the other end is sealed into a flat-plate actuator arm. In this type of test, however, at test pressure joint than occurs in a motor. the maximum axial load that
test end
Of the vectors
/ /7 ,/
7 jr
Hydraulic
actuator
Load.cell
joint
1
Pressure
chamber
Figure 22. - Fixture for testing joint actuation under pressure.
_\
"\
with
the
pivot
point
joint but
have
been
must
allow
unsuccessful, the joint
because to vector
the freely
test about
arrangement its effective
must
not
pivot
point.
control
the
Proper location of the test actuator is important. It should be positioned in the test with respect to the joint as it will in the motor. Although joint spring torque is used as a design concept, the joint is not in fact subjected to pure torque. It has been shown that when the actuator was not oriented correctly to the joint, the vectoring response in the test was different A flexible
from joint
that
in the motor.
deflects
linearly
in addition
effective pivot point. Attempts have tracking one or two points on the mathematical model to determine the model does not include linear motion,
to rotating;
thus,
it is difficult
to locate
the
been made to locate the pivot point by digitally joint or joint test fixture and using a rotational instantaneous pivot point. Because the mathematical the results are inaccurate to some unknown degree
66
.......
that depends on been developed
the joint design. (ref. 91). This
directly on a photograph, thus measurements and avoiding instantaneous Most
bench
direct shows
eliminating the the dependence
photographic the position
method of the
of measurement effective pivot
has point
need to calculate the position from deflection of each calculated position on previous
positions. tests
environmental
of joints
are
temperature
85 ° F (303 K). The extremes is predicted 2.1.7.1.
2.1.7.3
A more method
STATIC
conducted
at approximately
requirements
usually
are limited
test temperature is recorded, from the elastomeric-material
FIRING
75 ° F (297 to the
range
and joint response characterization
K),
because
60 ° F (289
the K) to
at the temperature described in section
PROGRAM
During the static firing tests, measurements are taken to check the overall design and to obtain data needed to design other components that interact with the nozzle design. Measurements taken include axial compression, vectoring capability, nozzle misalignment requirements,
friction
characteristics,
The axial compression interact with another
natural
is required to check stage or equipment.
frequency,
and damping
coefficient.
the envelope requirements when the motor must During a firing, the nozzle'is vectored to various
angles up to the maximum required angle in order to check clearances between the fixed and movable portions and to check the movable nozzle envelope requirements. During this vectoring, actuator force is measured. For comparison of static firing and bench testing results, Sizing from
the nozzles
are vectored
of the correct actuator the static firing. During
at the
same
frequency.
length for nozzle misalignment (sec. 2.1.2.3.1)is determined a firing, at several times selected to give as wide a pressure
range as possible, the actuators are held at the trial length for at least one-half second. Prior to the firing, the nozzle is actuated in the motor, sufficient measurements being made to enable calculation of the vector angle per inch of actuator stroke. From a comparison of firing
and
actuator The
pre-firing length
friction
data,
the
for null nozzle
characteristics
amount position
of the
of zero-pressure at pressure
nozzle
(i.e.,
the
misalignment
is calculated
and
the
is determined. flexible
joint)
are required
for the
design
of the guidance control system. As noted earlier, friction consists of viscous friction due to the viscoelastic characteristics of the elastomer (a rate-dependent component) and coulomb friction (a rate-independent component). During static firing tests, a nozzle is vectored at different rates but at constant amplitude, and the actuator force is measured. The data are plotted as determined.
shown
in
figure
14. Both
total
67
friction
and
the
two
components
are
thus
Frequency-responsetests are madeduring a static firing by imparting to the nozzle a duty cycle that cdnsistsof a successionof sinusoidalactuations, eachof short duration andlow amplitude. These actuations are made at different frequencies established from considerationsof the control system response.Attempts havebeen made to calculate the damping coefficient from the decaying force transient that occurs at the end of a step function applied to a nozzle;however,the attemptswerewithout success,sincethe damping coefficient could not be correlated with the viscous friction coefficient calculated from actuation data.
DESTRUCTIVE
2.1.7.4
TESTING
The failure strength of a flexible joint is determined by destructive testing. Joint failure occurs as a result of motor pressure and vectoring. Currently, failure strength of a joint for combined conditions cannot be defined. A test is conducted in which pressure is increased incrementally,
the
joint
being
actuated
to the
maximum
applied
operation at each pressure until failure of a component occurs. the design ultimate pressure, and sufficient clearance envelope increased until failure occurs. The failure test is conducted testing
vector
angle
during
motor
If the joint has not failed at remains, the vector angle is as an adjunct to the bench
program.
2.1.7.5
AGING
In addition the joints
PROGRAM
to the
subscale
is conducted.
aging
Joints
program
are stored
described in the service
in section
2.1.7.1,
environment;
an aging at intervals,
program joint
for spring
torque and axial deflection (sec. 2.1.7.2) are measured. These tests are conducted at zero time (for reference), at 3 months, 6 months, 1 year, and annually thereafter. Most changes occur in the first year. The measured values for spring torque and axial deflection are plotted against life is compared
time; the results are extrapolated to determine joint with required motor life to demonstrate probability
life. This extrapolated of satisfactory service
life.
2.1.8
Inspection
The inspection of a flexible joint fabricated by injection or compression molding is difficult. No techniqugs have been successful in evaluating the quality of the elastomer or the quality of the adhesive bonds between the reinforcements and the elastomer in a molded joint. Assurance dimensional
of joint control
and adherence
quality of the
to acceptance
is obtained reinforcements, bench
by
control process
tests.
68
of the quality of all materials used, control during mold setup and molding,
For joints fabricated by secondary bonding, it is possible to check the pre-molded elastomeric pads for internal defects such as voids, inclusions and delaminations,and the bond between the reinforcement andelastomerby C-scanultrasonic techniques(ref. 22). In addition, joint quality is assuredby control of the quality of all materialsused,dimensional control of the reinforcements,and alignmentof the reinforcementsduring joint layup.
2.1.8.1 To
INSPECTION
ensure
reliability
PLAN of the
fabrication process program is conducted.
joint,
control This
a detailed
in conjunction program permits
timely repair and correction of these areas. resulting in satisfactory joints. Development following
and
comprehensive
with a detection
program
nondestructive of potential
Proper inspection of a successful
processes inspection
(2)
Evaluation of existing inspection techniques for sufficient and development of new acceptable or adequate techniques
(3)
Verification that the of the actual defects.
(4)
Establishment inspection
of the
of
both
INSPECTION practice
types
of defects
inspection
accept-reject
that
techniques
standards
require
detection.
obtain
for
a valid
each
sensitivity and accuracy when necessary. indication
type
of
or description
defect
and
is
any redundant inspection, modification of new inspections as knowledge
development
of and
existing experience
inspections, are gained
and production.
PROCESSES to
inspect
the
joint
dimensions
and
performance.
The
dimensions
inspected are those that affect joint molding, joint performance, and joint assembly nozzle. In performance inspection, the operational integrity of the joint is demonstrated. Reinforcement
each
technique.
Elimination of and introduction during
Current
are the key factors plan involves the
steps: Determination
2.1.8.2
and
and destructive test causes of failure and the
(1)
(5)
of material
dimensions
such
as inner
and
outer
diameter
and
flatness
affect
the
in the
joint
molding. The spherical radius, thickness, and concentricity affect the joint performance. The elastomer thickness and porosity can be inspected only by molding a joint without adhesive on the reinforcement surfaces. After molding, the joint is disassembled to check elastomer
thickness
and
porosity.
The
frequency
69
of
this
inspection
depends
upon
the
variation that is noted in the thickness.Radiographicinspectionhasbeentried, but the large amount of metal in the joint preventsdefinition of the bond line or elastomerthickness being defined to the required accuracy. After molding, the joint is dimensionally inspectedfor overalllength, concentricity between the end attachment rings, and end-ring to end-ring reference plane parallelism. These dimensionsaffect the overallposition of the nozzle with respectto the motor. The operational integrity of the joint is demonstratedby bench testing (sec.2.1.7.2). The significanceof thesetests is basedon the premisethat joints successfullypassingthesetests aresuitablefor assemblyin a nozzle. 2.2
LIQUID
INJECTION
Thrust' vectoring by LITVC of a rocket motor through
THRUST
VECTOR
CONTROL
is accomplished by injecting a liquid into the supersonic holes in the wall of the nozzle exit cone. The injection
exhaust produces
side thrust by a combination of effects that include the thrust of the injectant jet itself, pressures on the nozzle wall from shock waves, and pressures on the nozzle wall resulting from addition of mass and energy to the exhaust flow. These effects are illustrated in figures 23, 24, and 25. Liquid injection TVC has provided thrust side forces of 17.6 percent of axial force injectant for such
specific impulse large deflections.
spreading forces act
vector deflections as large as 10 °, equivalent (ref. 46). However, efficiency as measured
drops to about 30% of maximum at the The low efficiency at high flowrates
of the LITVC pressures around in directions different from that
to by
high flowrates required is due largely to the
the nozzle circumference, where local LITVC of the desired thrust deflection. Serious losses in
efficiency can occur if the higher pressures induced by LITVC reach the opposite side of the nozzle. This condition can be caused by very high injectant flowrates, by the injector being located
too
incomplete close to disperse
near
the
the
and mix
the
easily
added
the gain in side less-than-maximum The
maximum
efficiency
throat,
or
by
a combination
mixing and reacting of the injectant with the nozzle exit or from using large concentrated
As the injectant flow Then as the flowrate because
nozzle
(refs.
105,
106,
is increased, is increased
flow
and
forces
practical that
thrust must
on the opposite
deflection be
accepted
!
due
injecting that do
to too not
and usually reaches a maximum. decreases. This decrease occurs side of the
Thus,
maximum
angle
is limited
if the
70
1ii
Inefficiency
gas may result from injectant streams
force increases the side force
force on the injector side. flowrates (ref. 108).
penalties
both.
107).
the side further,
is creating
of
system
side
to
nozzle
force
about
is designed
that
cancel
out
can be obtained
6 ° because to
produce
at
of
the
larger
Discharge
angle
positive injecting
When upstream
Separation
Pressure or
Squib tank
valve
(for
Toroidal tank
regulator relief
shock
valve
_arated
boundary
layer
high-|
only) Gas
High-pressure
gas
tank Injectant
or
gas
mixing
generator
Injector Manifold
Gas
to
roll-control
surplus-gas
dump
nozzles (gas
or
gen. only)
Flow Burst
Figure
23.
- Schematic
of typical
meter
Bladder
liquid
injection
TVC
system
and
diaphragm
side
force
phenomena.
/exhaust-gas and
reacting
Nozzle
Shock (Wall Nozzle
pressures
exit
area increase
I00
to
60_/o
thr_ above may
normal be
as
nozzle high
static
as
507°
of
pressure chamber
and pressure)
%
Injection
orifice
_'_'_ jectant (Wall
mixture
pressures
0 above
Sheltered (pressures 40_
below
area
to 300_ normal)
B
area 0
to
normal)
A
o °r4 4J (U
A
,r4
/_/_
&J
"I
__Pressure
along
A-A
J" \
--
\._
_Pressure
....
along
B-B
"- "----..__
O ..4
,-4 i
CI Nozzle ,-4 N _q O
Injector Pressure
along
C-C
= > o
f_
Injector
Figure
24.
- Nozzle
pressure
distribution
due
?2 ¸
to
injection
of
inert
injectant
(ref.
104).
exit
i/
L
2
0°
kN/m2 621
10°
psi
105o _9
75°
i 0.15
90 _k--_30
552
80
483
7O
414
60
345
50
276
4O
207
3O
_
°
_:_:
_/_1 _._._/\
__
__!
I
__o_
,-4
"_.
--
o.10
0
k 03 o3
O_
I/O'°kXX_k
_-/--_
' __15
I't_ _,_
e_
e = 21.81 e= 2.86 Injection
69
3,2"
°
,, I,, ",,',x_, ' : __,_._---",.>/''_ :'_ _, I00o_\\\ \ ._oo_ _ ___.._/_/_
U
138
¢=
L___
70°_
i __
.
T--__
_ 0.o5
•
_
Centerline
20
I0 0.oo
0 .0
2.0
3.0
4.0
5.0
Expansion
Figure 25. - Nozzle pressure _stribution
6.0
ratio
7.0
e
due to injection of reactive injectant.
8.0
9.0
o
deflections. To obtain higher deflections, larger located nearer the exit to reduce the side-force efficiency injection Liquid
of the locations injection •
has
a number
advantageous fluid through also obtained.
of desirable
•
fluid
with
Long-term demonstrated. including tetroxide, days in
2.2.1
System
The
the
low
objectives
parameters performance
are unique,
sizes and
as follows:
by the axial component of component makes it doubly
systems have
surplus thrust is
rapid and can produce a signal-to-force This speed is the result of the fact that the liquid injectant, and friction, and the reaction
the of
instantaneous.
in a state contained
in clean
The
aluminum
of instant readiness sealed supplies of
has been injectants
tanks.
Design
consists of a tank of injectant, liquid injectant, under pressure
valves
controlling
flow
operate
of an LrI'VC
system-design
of injectant, injector storage tank, and
effort
a source of compressed gas, tubing, from the gas, flows through tubing
on receipt
flight-control subsystem. Basic design features LITVC systems are shown in figures 27 and 28.
injectors, type liquid injectant
orifice
system during flight by jettisoning is removed from the vehicle, extra
gas is almost
LITVC systems
and these must be above. Thus, the
for various
of which
valve pintle and drive parts, inertia and move with little
exhaust
storage of These
A typical LITVC system and injector valves. The injectors.
be used, mentioned
Freon 114-B2 and aqueous solutions of strontium perchlorate. Nitrogen one of the most highly reactive injectants, has been stored as long as 75 the Titan III system (ref. 47)i Dry N204 probably can be stored
indefinitely
vehicle different
some
main motor thrust is increased on the nozzle wall. This axial
to lighten the LITVC the injectors; as weight
all moving parts-the tank bladder-have
to the
features,
Liquid injection TVC is inherently very time less than 20 msec without difficulty.
the
must effects
system at all flowrates is compromised. Effects are presented in references 46, 108, and 109.
During vectoring, the the increased pressures
•
injectors limiting
are
of electric illustrated
are to establish
the
in
signals
from
figure
26.
number
location and injection angle, the type the method of pressurizing the liquid
and
and shape injectant.
the Two
type
of
of the These
are established in the system-design analyses such that required vectoring is achieved at minimum weight without violating imposed constraints (e.g.,
74
Gas
generator
igniter Gas
roll
wiring
control
Gas Inj ectant Gas
\
pressurization
generator Gas Gas-generator
igniter
supply
l
tanks
_
pressure Roll
lin_
regulator control
pressure Nozzle
Clamps
--.
Liquid
Section
w ve
and
relief
control lines
Three-pintle Section
A-A
equalizing Bladder
line Skirt
Liquid
injectant
Figure 26. - Basic design features in a LITVC system.
B-B
injector
gas
Nitrogen gas vent valve
fill
i."".::." Com_n injectant _,"• ;.' _,,-gas tank
...o...,'. r,_Compressed
and
and
nitrogen
.°".':°°; '...%'
,
_Injectant ,
TVC electrical distribution
_ tlnaJneC f:nttube
/
Illl I
TVC
box battery
_/
power
_
switch "_'_"_
i __ E lec tromech anic injector valve
Figure
_Manifo ai
27. - Schematic
transfer
_ ld
drain
In j ec tant
_Nozzle manifold
Pyr o sea i
of Titan
III
76
ullage-blowdown
LITVC
system.
_
.
| I
.or-gas
i
generator
Hot-gas
pressure
relief
valve I
I
_ _r
aft
skirt
I
No
Toroidal for
tank
liquid
injectant
(a)
Side
view
Manifold Injector
orifice
(These
"sticks"
out
the
of
liquid
seals are
nozzle
for distribution
blown at
motor
ignition) ector
valve
for liquid
injectant
zle
Injector
Freon
pressure
sensing
Heat
Hot-gas
relief
va Gas
generator
igniter Hot-gas
firing
generator
I
Motor
(b)
Figure 28. - LITVC
End
aft
skirt
view
system for Polaris A3 second stage.
77
unit
shield
envelope, evaluation
response). of the
injection
pressure
2.2.1.1
SYSTEM
To
optimize
weight,
and location
in the
of an optimization study and related parameters
and such
an as
nozzle.
OPTIMIZATION
an
bulk,
The system-design analyses consist performance of injectants, injectors,
LITVC
and
system
performance
for data
a particular from
design,
known
the
LITVC
usual
procedure
components
is to compile
and
from
selected
designs provided by manufacturers. These data then are generalized in empirical equations or curves. Schematic designs representing the design alternates (e.g., type of fluid, number of injectors, and injection location) then are prepared to serve as a basis for optimization calculations. These alternates are evaluated for performance, weight, and compliance to the vehicle space envelope. For each design concept, an overall vehicle performance parameter is calculated for use in numerical evaluation; and typically has been either the payload burn. The results of the choice, injectant amount, This initial optimization considered and injector location
this parameter depends on the vehicle mission or the vehicle final velocity at the end of motor
early optimization give preliminary number of injectors, approximate reduces significantly the number
simplifies the detailed and discharge angle,
studies amount
for injection of injectant,
determinations of the injectant system pressure, and so forth. of design possibilities to be
pressure, orifice size and spacing, and the system pressurization gas
required. As the detailed studies of these items proceed, the empirical equations are improved and the optimization is repeated as necessary to improve the results. A limitation changing
of LITVC the
design
that to
is important
accommodate
design requirements. If the system performance of which is known, requirements.
Usually,
however,
the
changes being then new
design, and data scaling has to be applied of overdesign. Also, systems usually are trajectory reasons,
in the
major.redesign and operating
period
in maximum
designed the new design
are
different
and angle of the injector valves after the initial design phase and
revised
items that most tubing, injector
in
or other
any
the the
previous
and the likelihood of the worst-case
downwards.
For
these
better linearity and jet carried in the tank, are they do not necessitate influence system weight valves, and the location
on the nozzle wall) are difficult and therefore usually are left unchanged.
78
force
from
uncertainties initial estimate
in particular redesign of pintle shape to provide flowrates and to reduce the amount of injectant are made late in the development period because
and additional tests. However, the efficiency (sizes of tanks, brackets,
side
of flexibility
similar to an earlier design, can be designed close to
is significantly
estimates
is lack
required
is very system
with the attendant sized to meet the
requirements. Later these initial most systems in use are oversized.
Minor corrections, formation at lower changes that often
development
and curves preliminary
expensive
to redesign
Oversizingis minimized by repeating the optimization procedureas late as possiblebefore the systemdesignconcept is frozen. Corrected designand performance data are used, and the flight-control vectoring requirement is reviseddownward, if possible,usually by better definition of trajectory events. Thus, the more realistic the inputs in the optimization : procedure,the more nearly correct and usually lighter weight is the final systemdesign.
2.2.1.2 The
SELECTION
chief
impulse, tetroxide
OF INJECTANT
factors
considered
density, storability, and and an aqueous solution
Freon 114-B2, and operational injectants Side
in the
specific
selection
of the
liquid
injectant
toxicity. Prime candidates of strontium perchlorate;
for other
hydrogen peroxide. The basic properties are presented in table IX and discussed
impulse.
Side
specific
impulse
its
the injectant candidates
and below.
is a measure
are
side
are nitrogen are hydrazine,
characteristics
of the
specific
vectoring
of major
power
of the
injectant and is defined as the side force, lbf (N), divided by the injectant flow rate, lbm/sec (kg/s). Reactive injectants have larger side specific impulses than inert injectants. Inert injectants to 1569 solution
or
specific angles
such as Freon 114-B2 deliver N-sec/kg), while chemically nitrogen
impulses less
tetroxide
of
than
180
to
(N204)
300
0.5 ° in Titan
400
side specific impulses of 70 to 160 lbf-sec/lbm (686 reactive injectants such as strontium perchl0rate
lbf-sec/lbm
(1765
III
configurations,
(3923
N-sec/kg)
greater
than
specific location,
impulse depends on how well the design size and spacing of injector orifices,
injectant-stream Density. and
lbf-sec/lbm
significantly
are
more
to 2942 side
have
effective,
N-sec/kg)
specific
been
delivering or more.
impulse
recorded.
values
The
At for
actual
is optimized with respect injection angle, injection
side TVC N204
delivered
to the injector pressure, and
characteristics.
- Injectant
injectors
density
required.
is a major
Storage
space
influence on
on the volume
some
vehicles
has
and been
weight
of tanks,
sufficiently
preclude use of a low-density injectant. Even when storage space was available, larger tanks, piping, and injectors imposed a weight penalty that eliminated injectants from optimization studies. For this reason, the densities of injectants
piping,
limited
to
the required low-density used usually
have been approximately twice that of water. The high density has made it possible to store the injectant in compact tanks and permitted use of relatively small tubing, valves, and injectors. Thus, both weight and space on board the vehicle have been saved. ,
?
Storability.Storability of a liquid expected storage temperatures and materials it contacts. It is the measure LITVC
system
in a state
of
readiness
depends pressures of the over
both on the stability of the fluid under and on its compatibility with the tank capability of an injectant to be stored in the
long
achieved by controlling the purity of the injectant not react with the injectant and that contains reactions.
79
periods
of time.
This
condition
and by providing a tank material no trace elements that could
usually
is
that will catalyze
TABLE IX. - Basic Properties and Characteristics of Main Operational Liquid Injectants
Injectant
//
Property or characteristic
Freon 114-B2
Side specific impulse, (t) lbf-sec/lbm
70 to 160
Density, Ibm/ft 3
134.5
Freezing or crystallization point, °F
-31
Stability in storage
Reactivity metals
with
Strontium perchlorate (solution in water) ,'
Nitrogen
tetroxide
150 to 260
180 to 400
124.5, 62% solution 126.1, 72% solution
90.0
32, 62% solution 50, 72% solution
12
Very stable; nonflammable.
Solution
Stable if dry and without
sealed storage
impurities.
Inert in absence of water.
Noncorrosive to stainless steels and aluminum.
Noncorrosive in absence of water to stainless steels and aluminum
/
/
is stable in
oo O
(ref. 110). Stress corrosion with titanium (ref. 111). Reactivity
with
polymers
Penetrates
and deterio-
rates polymers.
Almost no effect on elastomers
problem
Most elastomers are incompatible with N 204 for long-term storage;
and most
other polymers (ref. 110).
some disintegrate in hours, others in days. Only nitroso compound AFE-110 and Parker compound B-591-8 are acceptable for 90-day storage (ref. 112).
Harmless on contact.
Toxicity
Fumes harmless in moderate amounts.
Solution has low toxicity. No problem with good housekeeping. Dry perchlorate is moderately toxic and irritating
Severely burns skin and eyes on contact. Inhalation of fumes can be fatal.
to the
skin. Vehicle on ,which injectant
is used
Polaris A3 second stage; Minuteman II second
Minuteman ili third stage (66% solution)
stage; Sprint first stage.
(I) Basedon test data for which injection location in the nozzle and injector geometry wereclose to optimum.
Titan I11
Studies
have
been
conducted
to
determine
the
compatibility
of
liquid
various materials (refs. 111 through 119). The results of one such study table X (ref. 120). As shown, Freon 114-B2 is almost completely
injectants
with
are summarized in inert with metals;
however, it should not be stored in metallic materials subject to corrosion, since any water contamination causes hydrolysis and subsequent corrosion. Freon 114-B2 does not affect Teflon materials but does permeate various elastomers, thermosets, and thermoplastics; it leaches plasticizer from the plastics, making them hard and brittle. Both N204 and Sr(C104)2 are reactive. Strontium perchlorate must be contained in stainless steel or titanium storage tanks. It is stable and safe at 350 ° F (450 K), but at higher temperatures it decomposes 811 K), reaction
and
storage
pressurization
temperatures,
Nitrogen
rocket
and
.gives
the
highest
or
percholorate
side
makes purity
range
for
to 1000 ° F (755
all reactive
for any
specific
to 900
crystallizing
of the
impulse
of
liquids.
liquids the
in a 62%
injectants
temperature
solution
In
comparison
that
are
and in readiness at operational pressure tetroxide has been selected for use in the
control is
of N2 04 has been
the
system. limiting
low
temperature
for
storage.
not occur either in Freon or nitrogen tetroxide. Freon K) and N2Oa freezes at 12 ° F (262 K). Strontium
with
with
here.
occur. Elastomeric materials cannot be used for and storage requirements are well established in the
water
crystallizes
out
of the
solution
at 32 ° F (273
- Nitrogen tetroxide burns on contact, and inhalation of fumes Freon 114-B2 is harmless on contact and its fumes are harmless
amounts.
At normal
mentioned
it difficult to handle. It can be stored successfully and container inertness are met; otherwise,
III post-boost
does (238
K to
with rubber that an almost explosive end of the duty cycle in systems with
problem
a problem
for up to 75 days 47 and 114). Nitrogen
Crystallization or separation 114-B2 freezes at -31 ° F
Toxicity. whereas
is not
for the Minuteman
freezing
the
present significant problems. The current practical storability in Titan III operational practice, where the LITVC system
to remain loaded a 30-day hold (refs. engine
is a potential
and degradation will Handling precautions
and do not demonstrated
Within
combines so readily has occurred near the
reactivity, however, requirements for
decomposition long-term seals. industry has been
oxidizer.
decomposition
tetroxide
operational;its only if strict
approved through
a strong
strontium perchlorate occurs. This reaction
gas-generator
The
becomes
Freon
114-B2,
strontium
perchlorate
K).
can be fatal, in moderate
delivers
50%
more
specific impulse, costs half as much, and involves fewer compatibility and storage problems. However, strontium perchlorate is moderately toxic and irritating to the skin. Care must be exercised to prevent the these saturated materials
2.2.1.3
INJECTION
In a typical formed by
perchlorate would burn
PRESSURES
LITVC system, the a convergent round
salt or solution from rapidly if ignited.
AND
INJECTION
saturating
clothing
or wood,
since
ORIFICES
liquiffis injected into the nozzle through an annular orifice outlet with a central pintle, as shown in the injector cross
81
TABLE X. -
Compatibility
of Selected
and Aqueous Strontium
Metals and Nonmetals
with Freon 114-B2
Perehlurate (ref. 120)
Materials Tested Metals
oo t-o
Nonmetals
Ti-6A 1-4V
Hypalon
4130 steel
Neoprenes
4340 steel
Polyvinyl
7505 aluminum
Thiokol ST (polysulfide)
2024
Viton
aluminum
CN and W alcohol
"A"
347 stainless
steel
Tygon ST (polyvinyi
Molybdenum
steel
Teflons
Results after 3-week exposure
Freon
Material
Metals
20
1,6, and 100
at room temperature
114-B2
No visible effect
chloride)
Sr (C 104)2
on any metal.
4130
and 4340
steels showed
some rust; other metals showed no visible effect.
Nonmetals
All specimens showed
except the Teflons
signs of permeation
deterioration.
Significant
of liquid indicates problems.
and pickup
permeability
Polyvinyl
alcohol and Thiokol
showed signs of chemical
ST
reaction
and deterioration; other specimens showed no visible effect. Pickup of liquid was negligible.
sections
in figures
29,
30, and
31. The
central
pintle
acts
as the
gate
of the
injector
valve.
Thus, the full system pressure is applied to the liquid up to the point of discharge through the orifice. The injection pressure, orifice size, and orifice spacing have a significant influence Injection through
on side-thrust
efficiency
system pressure the orifice with
because pressures 121, and
compexity. force best
that drives the liquid side-thrust efficiency.
from 450 to 1500 psi (3.10 to 10.34 MN/m 2 ). Analysis of test firings with LITVC indicates that for maximum side-thrust
injection pressure (ref. 121). Such
these pressures are used, the
system
is important because it provides the the high momentum needed to obtain
System pressures in use range data from small-scale motor efficiency the rocket motor
and
should be set at about high pressures may not
also influence the weight probable loss in side-thrust
twice the chamber pressure be optimum for the entire
of the system
of tanks, tubing, and injectors. If lower efficiency can be estimated (refs. 108,
122).
Efficient development of side force by fluid injection depends mainly on rapid mixing and chemical reaction of the injectant with the hot exhaust gas close to the wall This complex process involves droplet shattering, evaporation, and nonequilibrium chemistry. It should be noted that practically all injectants decompose and react chemically, including the so-called inert injectants, although for these liquids the energy this process and the effects that compose it are found For most efficient fully reacted with
development exhaust gas
released is small. Analytic models of in references 105, 106, 110, and 123.
of side force, the injectant should be thoroughly mixed and in the immediate neighborhood of the wall. For thorough
mixing, the liquid jets should have the highest possible However, to prevent the high-velocity jets from passing
momentum and therefore velocity. out of the immediate neighborhood
of the wall and penetrating too far into the gas stream, where their effects would be lost, the individual jets must be made so small that in spite of their high momentum they will have broken up and become mixed with the gas while still close to the wall. At all flowrates, the momentum per unit mass of liquid discharged remains about the same, since it is dependent on the pressure of the injectant in the system. This momentum contributes to the LITVC effect
by
partially injectant For
delivering
a force
against
the supersonic
stream
that
produces
the initial
shock
and
from
the
diverts the direction of flow. The balance of the LITVC effort results and its reactions producing higher flow pressures acting against the wall.
a well-designed
pintle-type
injector
(figs.
29
and
greatest side-thrust efficiency is obtained at low because at low injector openings the jet maintains discharged but the annular jet stream has a thin
30)
having
a given
orifice
flowrates (ref. 108). This effect occurs the usual high momentum per unit mass section, so that it mixes efficiently and
penetrates only into the gas that is closest to the annular jet increases in thickness, so that it penetrates
wall. At high flowrates, much more deeply into
stream, thereby must be applied
the
carrying the to be useful.
injectant
farther
83
from
size, the
wall
to which
the
however, the nozzle pressure
the gas
effects
Pintle
Erosion resistant insulation_
Injector valve
body
0
%
mechanism and hydraulic valve.operatol Nozzle
Figure
29. - Cross
section
drawing
Passages
of typical
for
fluid
single-orifice
that
powers
injector
mounted
on nozzle
injector
_njectant inlet
Orifice Pintle Nozzle
Figure
30. - Cross
section
drawing
of three-orifice
84
injector
wall
mounted
on
nozzle
wall.
wall.
Ball
screw
helical
bearing IX:
electric
torque field
Injectant
motor
inlets
J
5
/ i Pintle
position
transducer Injector
mount
Figure 31. - Cross section drawing of an electromechanical injectant valve.
Side-specific-impulse openings (ref. 108) The drop advantageous
in
efficiencies have an upper limit at very small orifice because increasing orifice friction reduces jet momentum
efficiency that occurs with to use a large number of small
large flow from orifices. The flow
jets, ,so that in spite of the great flow momentum the main stream; instead, the jets break up close the gas, vaporizes, and reacts to release energy The
large
Increasing
number the
of injectors, number
however,
of injection
add
ports
a single is divided
sizes and valve per unit mass. orifice among
the liquid does not penetrate to the wall, where the injectant that produces higher pressure
to the increases
complexity the
and
injection
the
makes it individual
deeply mixes on the
into with wall.
cost.
efficiency,
provided
that
overlap losses and cosine regions of shock pressure, not the sum of influences
losses are not excessive. Overlap losses result from the overlap of mixing, and reacting. In these regions the local pressure increase is from two separate orifices but a lesser amount, greater however
than
alone
that
for
one
orifice
(refs.
of the LITVC wall pressures around potential side force to be lost because
108
and
124).
Cosine
losses
the nozzle; this spreading opposing force components
85
result
from
the spreading
causes a portion of the cancel. These losses are
called cosinelossesbecausethe local LITVC force is diminished, for TVC purposes,by the cosineof the anglebetweenits direction andthe desiredside-forcedirection. The basic the rocket acting
liquid injection configuration has four nozzle for positive and negative pitch
between
the
simultaneously, and from these injectors.
pitch
and
yaw
planes
or more injectors and yaw control.
require
that
several
spaced Needed
equally control
adjacent
around forces
injectors
flow
the resultant force is obtained by vector addition of the control forces The use of more than four injectors (e.g., six, twelve, or twenty-four
injectors equally spaced around the nozzle) decreases the amount of fluid required, because the injectors that must provide a given control force will more likely be located closer to the direction of the required force; with more injectors flowing simultaneously, each injector will deliver
less flow
The predicted number, and
and
therefore
response of the spacing is reduced
optimization calculations contained in references 47,
2.2.1.4 The
INJECTOR
injector
AND
on the
higher
side-thrust
efficiency.
system to changes in injection to curves and equations for
(sec. 2.2.1.1). 121, 125, and
LOCATION
is positioned
will have
Examples 126.
of
DISCHARGE
nozzle
pressure or in orifice size, use as inputs in the system
such
curves
and
equations
are
ANGLE
wall (fig. 23)
at a location
and
a discharge
angle that
is optimum for the location for injection from the side force.
expected schedule of vectoring for a typical flight. The optimum is a compromise of two opposing tendencies that add to or subtract If the injection point is as far upstream in the nozzle exit cone as
possible, increased.
wall area over as the injection
the nozzle However,
injectant-augmented
portion
of the
which point flow
the pressures are augmented by injection is moved upstream, the shock wave of
spreads
out
around
and
across
the
nozzle
is the
until
it
produces a pressure on the opposite half of the nozzle that subtracts from the desired side force. This cross-interference tendency increases with rise in the ratio of injection flowrate to motor flowrate. For a very low injection flowrate, the optimum injector position on the nozzle the
wall
optimum
126). The at which expenditure
is upstream position most the
and
relatively
is downstream
close
to the
from
favorable injection point total required program
the
throat
but
nearer
for larger the
nozzle
injection exit
flowrates
(refs.
for a particular motor is an intermediate of thrust vectoring is accomplished
107 and
location with least
of liquid.
:The injector discharge (fig. 23) usually is directed 25 °. The 25 ° angle has been found to be optimum Pointing between
throat,
the liquid the exhaust
upstream at angles ranging from in subscale tests (refs. 108 and
jets upstream produces several effects. gas and the liquid jet shatters the droplets
The greater to a smaller
0 ° to 109).
relative velocity size, thus aiding
evaporation and mixing. The injectant is delivered slightly upstream of the injection point, an effect equivalent to moving the injection upstream by that amount. Directing the fluid
86
j_
jet upstream along the wall reduces the depth of penetration of the jet and keeps the injectant mixture and its higher pressures nearer the wall, where they will produce more side force. If the jet is directed too close to the wall, at angles appreciably greater than +25 ° , the beneficial effect of better mixing and improved positioning of the resulting higher pressure region is more than cancelled out by losses (ref. 125). These losses probably result from a reduction in the useful component of the injectant jet reaction force, loss in momentum of the
main
gas stream
momentum The
due
to more
in the injector
optimum
injection
due
direct
opposition
to the larger
location
usually
by the fluid jet,
diagonal
is closer
passage to the
and greater
through
throat
loss of fluid
the nozzle
than
to the
wall.
exit,
with
a value
of optimum X/L _ 0.3 being typical (X = distance from throat to the plane of the injector ports, and L -- distance from throat to exit plane). Motors with submerged nozzles do not permit injection at the optimum location, and a performance penalty is thus imposed. For the Poseidon consideration
C3 motors, the penalty was so as a TVC system, and the flexible-joint
The injection location parameter location, can be misleading when phenomena that divergence angle, LITVC effect. Since their
cause shock
In the usually
effects of injector 108, 122, and 125.
OF LIQUID
system optimization calculations, indicates the relative efficiency
amount
of liquid
the
largest
item
and
from
for specifying injection indirectly related to the
including are more
influence the calculations
location
INJECTANT
convenient it is only
parameters dimensions
angle of injection strongly in the system optimization
curves presenting the contained in references
AMOUNT
while simple and in design, because
the side force. Other angle, and mixing-path
the location and effect is included
2.2.1.5
X/L, used
large that LITVC was eliminated TVC system was adopted.
the expansion directly related
ratio, to the
LITVC side-force efficiency, (sec. 2.2.1.1). Examples of
angle
on
side-force
efficiency
are
REQUIRED
the amount of liquid required is the parameter of each design concept considered. Not only
of weight
that
must
be carried,
but
it determines,
that is the
through
its equvalent volume, the size and weight of the tubing, injectors, and tankage. The latter is usually the heaviest item of inert weight. Thus, the system design conceptJthat requires the smallest amount of injectant liquid usually is the one shown to be gtOst desirable by the optimization calculations. JJ The
amount
of liquid
very conservative of maximum extremely the flight
method expected
unlikely, including
required
depends
on
the
required
for calculating the amount vectoring requirements.
vectoring
of liquid Statistically,
since it provides for the most unfavorable the most irregular launch or separation,
87
program.
uses type the
the such
A simple
worst combination a combination
but is
of event at every stage of most severe weather and
wind shearsat all altitudes, the most eccentricpossiblealignment of vehicleweights,andthe greatestnozzle misalignment.The statistical oddsfor this worst combination usually is very small, typically lessthan 1 in 100000. This "worst-on-worst" method generallyhasresulted in overestimatesof the total side impulse required and in design of systemsthat carry grosslyexcessiveamountsof liquid. Sometimes,after flight experiencehad revealedthis fact asin the Polaris A3 program,the amount of liquid loaded in the tank hasbeenreduced,but useof an oversizedtank continued. A better method of determining the amount of side impulse and therefore the amount of liquid required for vectoring employs statistical techniquessuchasthe Monte Carlo method (refs. 47, 127, and 128). By this method, the amount of liquid required is determinedasa function of the probability that the vehicle will not run out of liquid before the vehicle operation is completed. The calculation considersa random probable requirementfor each separatepart of the vectoring program and sums eachpart to obtain the total amount of injectant required. The calculation is repeatedmany times to develop a statistical basisfor the amount of liquid to be carried. Preliminary estimatesof total sideimpulse required for vectoring have been obtained by assuminga side force of 0.02 of total axial impulse for first-stage motors, 0.01 of total axial impulse for second-stagemotors, and 0.006 of total axial impulse for third-stagemotors. In addition to the liquid that is neededfor vectoring, liquid is carried for ullage, filling of pipes andvalves,andvalveoperation; someinjectant is lost when valvesoperate,becausethe valves cannot open and close instantaneously. This unusable liquid is minimized by designingthe tank, bladder, piping, and valvesto avoid trapping liquid and to haveonly the flow volume required. Also, some valvesleak becauseof imperfect contact between the pintle and the valveseat.This leakagecanbe minimized and with good designshould be too smallto be included in establishingthe amount of liquid. The total required storage tank capacity thus includes'the liquid for vectoring plus the "unusable" liquid required for ullage, systemfill, valve operation, and possibly leakage.A typical procedurefor determining the total amount of liquid is asfollows: (,1) The
\
vectoring
requirement
is determined.
form by deflection angle and time; second, and 0.5 deg for the balance
Preferably
it is developed
e.g., 3 deg for two seconds, of the flight time. For each
1.5 deg for one deflection angle
the required side impulse is equal to the axial thrust times the deflection angle times the time required for this amount of deflection,
\\\\\,
the the
total latter
to estimate (2)
Curves scaling
in itemized
sine of the Sometimes
required side impulse and an average deflection angle are specified. In case, the maximum deflection angle is also specified, since it is needed the
injector
of estimated and replotting
size and
location.
side specific impulse versus deflection angle are developed by available data (refs. 46, 108, 109, 121, 124, 125, and 129).
88
(3) The liquid needed for vectoring each specified deflection angleis calculatedby dividing the side impulse required by the side specific impulse indicated on the curve developed in (2). The amounts of liquid thus determined for the various required anglesarethen summed. (4) The amount of additional liquid required for ullage,filling similar needs is estimated calculations, this amount liquid.
2.2.1.6
AMOUNT
of piping,
leakage,
and
and added to the above usable amount. For preliminary is sometimes estimated at 10 percent of the total usable
OF PRESSURIZATION
GAS REQUIRED
The liquid injectant in the system is kept under high pressures by gas that acts on the liquid in the tank either through a bladder (fig. 23) or piston or directly (fig. 27). The supply of compressed gas is made large enough so that when the liquid is expelled from the tank at the largest expected flowrate, its displaced volume is filled by fresh gas at a flowrate and pressure
sufficient
to ensure
that
the
system
pressure
does
not
fall below
its required
level.
The amount of gas that must be supplied to pressurize the LITVC system 'during operation usually is determined in the final evaluation of a system concept, the pressure the system and the amount of liquid to be injected having already been established. If the
LITVC
to expand pressure 2.2.1.3). required
system
into
the
is to be pressurized volume
occupied
by
by inert the
gas, only
displaced
the exact
injectant
must
amount
its of
of gas needed
be provided.
The
final
should, of course, not be less than the required injection pressure level (sec. If pressurization gas is to be generated by burning solid propellant, more gas will be than that needed for liquid displacement. The amount of gas required is the
maximum expected gas demand rate integrated over the operating time. This demand determined from the maximum expected injectant flowrate, which in turn is obtained the "worst-on-worst" severe vectoring requirements taken at all times through the operating
rate is from motor
time.
If a vectoring program requires only occasional side forces of short duration but large magnitude and if these can occur over a wide time span, the required amount of generated gas can be very much greater than that required to displace the ejected injectant. In some cases, this excessive required amount volume to act as a gas accumulator. compressed
2.2.2 The
inert
system
of the
concept
reduced by taking advantage of excess tank cases, it has been found to be better to use
gas.
Component design
has been In other
has
Design
components been
of the
developed;
i.e.,
LITVC after
89
system the
is begun
injectant
after
has been
the
optimum
selected;
the
LITVC injection
location, angle,maximum flowrate, orifice size and spacing,and systempressurehavebeen determined;the amounts of injectant and pressurizationgashavebeen calculated; and the approximate envelopeavailablefor the componentshasbeen checkedandbeenfound to be reasonablyadequate.Component design,asconsideredin the following section,includesthe detailed design of the LITVC systemas well as adaptation of the rocket motor for LITVC. The componentsof a typical LITVC systemarethe injectors, fittings and piping, tanks with or without bladders, gas supply for pressurization,meters to equalize tank drainage,and provisions for disposal of surplus injectant. The complete LITVC assembly usually is mounted around the nozzle on brackets that attach to the nozzle or the aft end of the motor. Erosion may be moderate or severeat the injectant holesin the nozzle wall, and this area may require special insulation and structure. Also, some form of heat barrier or insulation usually is required to protect the LITVC components from the heat of the exhaustplume.
2.2.2.1
INJECTORS
The injectors streamlined
are automatically operated discharge port, so that full
valves in which injection system
the valve closure is located in a pressure is effective close to the
point of release; thus high hot-gas flow in the nozzle
discharge velocity is imparted exit cone. The design of the
efficiency. A good injector velocity in order to impart
injects liquid in a linear, nondiverging jet at the highest possible high momentum to the fluid jet so that it interacts forcefully on
the
thereby
supersonic
dispersion, A range
gas
and of
stream,
mixing
sizes
and
causing
a shock
types
Variable-orifice injectors. become the most widely applications This
to
vehicle
-
of
injectors
is available
The variable-orifice used because of its
flight-control
are summarized
injector
has
a pintle
in table gate
is approximately cone-shaped, the ahnular orifice. Injector Supply piping flow resistance,
wave
and
liquid injected into the critically affects LITVC
maximum
droplet
breakup,
(fig. 23).
injectors have been designed for use on various or considered as the means of vectoring.
adaptation
to the injector
that
systems.
rocket
injector operating Design
from
control-valve
motors
for which
(figs. 29, flexibility features
of
suppliers. LITVC
was chosen
30, 31, 32, and and consequent this
These
33) has ease of
injector
in various
the
The
XI. moves
so that discharge
axially
in the port
to throttle
flow.
pintle
when moved into the exit throat it reduces or closes can be modulated from almost zero flow to full flow.
and passages usually are sized so that even at high flowrates
large enough to avoid pressure losses due to full system pressure reaches the liquid in the
injector valve and drives the jet through the orifice and into and pintle of the injector are designed with streamlined efficiently accelerated into a narrow, high-velocity stream.
90
the nozzle. The orifice approach contours so that the flow is The injector pintle is controlled
Servo
_o
6) _I_
_
_
_
_
\
Electrical
L__pSri!!!ye_
line I
.....
Control
Control valve
pressure line
kO
Feedback transducer Injector Nozzle
valve
not
shown
Actuator piston
Figure
32. - Injector
valve
assembly
with
hydraulic-powered
actuator.
_
Pintle
!
Hydraulic
Pintle
actuator
t ransducer
location
;. "
/
•
Injector
t
2
_D bO Electric i;:|
•
feedback
i/_J Injectant
i!i_ 1
Servo
torque
motor
)ply
i:;!
_:,1 i;I
Hydraulic control
valve
Control fluid
L .....
Note:
Liquid is
used
injectant as
control
fluid Electrical Liquid
Figure
33.
- Servo-controlled
injectant
hydraulic
power
connectors
supply
systems
for
variable-orifice
injectors.
TABLE _1.
Number Motor
of nozzles
Polaris A3 second
Minuteman _D
second
Number of
Number orifices
injectors
per injector
8
stage
- Chief Design Features
of
of Variable - Orifice
Angle of
Injector
injection
weight,
(fig. 23)
Ibm
25 °
4.4
(2 per nozzle) I1
on Operatioml
LITVC Systems
Operating Type of actuation
Electro-
Response
time,
Flowrate,
pressure,
lbm/sec
psig
deflection,
12.
750
0.230
60.
620
0.120
12.5
680
0.080
131
400.
800
0.022
50
signal to full
References
see
48
hydraulic
5.2
0 °
stage
Minuteman
Injectors
Electro-
49,113,130
hydraulic III
20 °
4.0
third stage
Electromechanical
Sprint
0
11.0
°
Electrohydraulic
Titan
II1
156-Inch
24
24
0 °
24.0
Electromechanical
100.
750
0.190
0 °
25.0
Electro-
158.
750
0.400
hydraulic
Note: The first five systems listed are operational; the last was tested in a development
program.
46,128,132
133
by a mechanism that provides signals from the vehicle flight
variable control.
control of the injector flow on command of electrical The control signals may be analog (variable voltage)
or digital. The valve motor may 'be electric, hydraulic, or both. Usually it is electro-hydraulic (table XI). In this case, the valve operation is controlled by a servo mechanism in which an electrically operated pilot valve is used to admit pressurized hydraulic fluid to move the valve closure or pintle injectors usually have
and thus to modulate the three orifices and pintles
orifices and pintles have electro-hydraulic systems, operate
the injectors
In
Titan
the
III
electro-mechanical
been designed the pressurized
(figs. and
32 and
NASA
actuators
flow (figs. 29 and (figs. 30, 32, and
and presumably injectant is used
system
Fixed-orifice
(ref.
could be to provide
fabricated. hydraulic
In some power to
33).
260-in. (fig.
(6.6
31).
m)
Adc
systems,
electric
the
motor
pintle position is sensed by a linear potentiometer connected adjusts the dc current so that the pintle position matches control
30). The servo-operated 33). Injectors with five
injectors
moves
the
are
operated
by
pintle
axially.
The
to an electronic the command
controller from the
that flight
47).
injector.
-On-off
fixed-orifice
development programs and have been been developed to operational status
injectors
proposed for any
have
been
tested
in various
LITVC
for use, but to date no on-off system has solid propellant motor and only one for a
liquid propellant engine (Lance). The two potential advantages of the on-off injector are high efficiency and light weight. The high efficiency is obtained if the valve gate or pintle is withdrawn fully from a countoured orifice so that the flow of liquid is not obstructed by the pintle but is accelerated and orifices must be made sufficiently
interacts small
wall
produces
where
mixing
from the modulation. (2.59 The
and
reacting
simple two-position (The Lance injector
kg/sec)
of hydrazine
disadvantage
of
greatest
wall
actuation that weighs 1.1 lbm (0.50
at 900
on-off
with the gas with maximum force. The size of the so that the jets break up and disperse close to the
psi (6.21
fixed-area
LITVC
frequency
is set outside
the
move
the
the injector The electric
injector
pintle
actuators
ranges
into the nozzle, signal is almost takes
the
flow begins when the pintle first Time for the liquid to accelerate reacting
of the
injectant
with
the
most
is that
that
weight
results
for flowrate of 5.7 lbm/sec
can be made the actuator
side-thrust
modulation
must
The resulting force pulses problems in the vehicle
can cause
time,
trouble. very rapid. The four events included pintle movement,, the movement of
typically
gas is very
94
be
produce a unless the
and the mixing and reacting of injectant instantaneous. The time for the actuator
opens and accelerates to full flow varies nozzle
light
MN/m 2).
Response time. - LITVC system response in response are the electric vector signal, liquid through in the. nozzle.
The
requires no feedback kg) and has a flow rate
accomplished by varying the length of the flow pulses. vibration effect that can cause structural or operating ,,
pressure.
15 to 200
milliseconds.
as the pintle completes from 1 to 10 msec. The
rapid,
ranging
from
less than
with gas drive to The
liquid
its motion. mixing and 1 msec
for
average-sizemotors to 2.5 msec for large motors time
is the
approximate
sum
of these
times
(note
such that
as the Titan III. The total response injectant flow and pintle movement
times overlap) and can be as little as 22 msec (ref. 139 and table time can be obtained by reducing the mass of the pintle, increasing and increasing the injectant pressure. Supplemental just upstream to malfunction.
injector hardware. - Screens of the injector to catch any
In some cases, closures storage or after system
are used activation
usually are installed pieces of solid matter
XI). A shorter response the pintle drive force,
in the liquid-supply piping that might cause the valve
at the injection orifices to prevent loss of liquid during but before motor ignition. For example, the Titan III
LITVC system is designed to be capable of being held at launch readiness for up to 75 days. The stored liquid is allowed to fill the entire system and is sealed from leakage loss at injector outlets by pyroseals sec after ignition (ref. 47).
2.2.2.2
STORAGE
The chief summarized The
liquid
TANK
AND
design features in table XII. injectant
is
(fig. 27).
of
Pyroseals
are fluid-tight
plugs
that
burn
off about
1/4
systems
are
BLADDER liquid
stored
storage
in one
or
systems
more
for
operational
spherical,
cylindrical,
LITVC
or
toroidal
tanks
typically made of stainless steel, titanium, or aluminum. Each tank usually is connected: to a system supplying compressed gas to pressurize the liquid. The gas may be cold and inert, usually nitrogen, or hot and reactive if generated by burning solid propellant. A membrane liquid and
or bladder prevent the
usually is used in each tank to keep the gas separated gas from mixing with, exchanging heat with, reacting
bypassing the fluid. It is advantageous and eliminate a development problem. and the liquid injectant are compatible tank outlet compressed
from the with, or
to eliminate the bladder if possible to reduce weight The bladder can be eliminated if the pressurizing gas and if the liquid is positively positioned over the
as in the LITVC system of the Minuteman helium to pressurize strontium perchlorate
III third stage. This system solution in a spherical tank.
uses The
gravity and acceleration forces apparently are sufficient to hold the liquid over the tank outlet. The bladder usually is a laminate of strong flexible plastic and fiber materials coated with an injectant-resistant material. Typically the internal fiber web has provided the needed mechanical strength and the facing side and an inert permeable seal bladder development, because the been critical to blow by
to the success the liquid and
plastic layers have provided thermal insulation on the gas on the liquid side. Much effort has been expended on dependable separation of liquid and pressurizing gas has
of most systems. enter the piping
95
A ruptured bladder may allow to the injectors, thus causing
pressurizing gas loss of control
TABLE XH.
Liquid
Motor
injectam
Polaris second
114-B2
Chief Design Features
Injectant density,
Amount of liquid
Liquid tank
lbm/ft 3
stored, Ibm
material
134.5
200
Aluminum
of Liquid Storage
Tank shape
third stage
Separation
on Operational
between
Toroidal
Bladder(Viton reinforced
LITVC Systems-
Source
of
pressurization
Initial
Surplus liquid
gas pressure,
jettisoned into nozzle during
psia
flight
Gas generator
NA
Gas generator
NA
Composed
3320
Yes
Dry weight of LITVC system,
139
with
Dacron)
!i
Freon
114-B2
134.5
259
Steel
Toroidal
(17-7PH)
stage
Minuteman
Systems
gas and liquid
stage
Minuteman second
Freon
A3
-
Bladder (Viton AVH reinforced with
111
Sr(Cl04)2 (62% solution
124.5
49.3
Ti-6AI-4V
Spherical
Yes
228
Dacron)
None
helium
No
42
gas
in H20 )
Sprint
Freon
Titan II1
N2 04
114-B2
134.5
160
Stainless
221
Piston
Gas generator
NA
None
Compre_ed
11O0
Yes
Cylindrical
7054
55O0
No
8808
steel
90.0
8424
Stainless
nitrogen
steel (41 O)
156-Inch
No
Cylindrical
N204
90.0
8170
Stainless steel
Cylindrical
Bladder (stainless steel and chlorobutyl rubber)
Notes: Status of systems and references for data are indicated in Table XI. NA = not applicable
gas
Compressed nitrogen gas
Ibm
effectiveness
and
system
pressure.
The
combustion of a reactive injectant. injectant in a system in which the serious result has been the reduction directly
to the
fluid
some of the best 117, and 118). A burst
and
diaphragm
have
at the
been
tank
of bladder
failure
also may
contraction obtained
outlet
of the
with
usually
gas. In bladder
laminated
is used
plastic
to seal
development
and metal
the
fluid
alternate
liquid
the
and
arrangement
pressurizing
having
gas in the
neither same
a bladder
tank
and
nor
relies
a burst
only
the
diaphragm
on gravity
work,
foil (refs.
in the
storage. On system activation, the rise of pressure in the fluid tank breaks and fluid flows through the tubing and manifold and into the injectors. A simpler
be sudden
For example, in an LITVC test using lead perchlorate bladder was eliminated, an explosion resulted. A less of the pressurizing capacity of hot gas by loss of heat
consequent
results
consequence
and
tank
115,
during
diaphragm,
stores
the
acceleration
forces to position the fluid over the outlet. The Titan III system uses this system (fig. 27). The supply tubing, the injectors, and about 2/5ths of the tank are filled with nitrogen tetroxide fluid and then pressurized by addition of compressed nitrogen gas into the remaining tank volume. Leakage from the injectors is prevented by pyroseals (ref. 47).
2.2.2.3
PRESSURIZATION
SYSTEM
High-pressure gas required to pressurize gas such as nitrogen or helium or by systems, the same gas generator is used The
compressed
gas system,
the fluid is provided either by a tank a solid-propellant gas generator (table as a source of gas for roll-control jets.
if independent
of the liquid
tank,
consists
bottle of any convenient shape, a squib valve, and a pressure pressure of the gas is from two to seven times the liquid system and XI), so that after is still greater than operation, the pressure-reducing injection liquid/gas bulk
the the
gas tank required
high gas pressure valve in order
usually is reduced to to obtain reproducible
liquid
has
been
used,
sufficient
With this _rangement, the initial injectant pressure but becomes successively less during cause a certain amount of wasted injectant also, in the case of electro-hydraulic valves variation
in injector
response
pressure
gas tank
or
valve. The initial pressure (tables X
needed, the tank pressure pressure. During motor
the liquid system pressure by a valve operation and to avoid an
pressure so high that it will degrade side-thrust efficiency tank is used (fig. 27), the initial gas pressure is made high
of the
of a metal
regulator operating
has discharged the full amount minimum system operating
of compressed XII). In some
still remains
(ref. 116). If a common enough so that after the for
effective
operation.
pressure is the same as the initial gas supply the TVC duty cycle. This reduced pressure will due to off-peak LITVC efficiency (ref. 133); operated by pressurized injectant, it will cause
time.
Usually the high-pressure tank is left filled remotely just before launch.
empty during storage and handling of the motor Otherwise, for the safety of personnel working
97
and is near
pressurevessels,the tank must be madeheavyweight with a factor of safety ranging from four to six. An advantageof pressurizingwith compressedinert gasis that no bladder or other separationis needed,provided gravity or accelerationforces constantly hold the liquid over the tank outlets for positive expulsion. The mixing of injectant vapor into inert pressurization gas and the dissolving of pressurizing gas into injectant liquid are minor problemsfor which allowancecanbe made(ref. 47). If a solid-propellant gasgenerator is used ir_steadof compressedinert gas as a sourceof pressurizationgas,the systemmay be designedwith the typical low factors of safetyusedin rocketry and also may be storable indefinitely in readinesscondition. The production of gas during motor operation dependson the burning rate of the solid propellant andthe burning surface at the moment. The generator propellant grain is shapedto provide a changing burning surface area that approximately matches the expected program of maximum demand for pressurizationgas.Accordingly, the gasgeneratorprovidesa continuous flow of gas throughout the motor operation sufficient to displacethe largest expectedliquid flow that may occur in each period of the motor operating time. Large vectoring usually is neededonly in the early part of the motor operation. Gas-generatorpropellant grains are designedto producelarge initial gasflows and relatively low flows later in the firing. Since adequategas flow must occur at all times whether gasis usedor not, significantly more gasmust be produced than is neededto displacethe total storedliquid. Whenexcess tank volume is provided to act as an accumulator, the total amount of gasrequiredcanbe reduced becausegas produced at times of low liquid flow demand will be retained for a limited time for useat times of largedemand. The surplus gasgeneratedthat exceedsthe liquid-displacementneedsand the accumulator capacity is diverted by a pressurerelief valve and releasedoverboard, preferably through small nozzles pointed aft so that thrust is recoveredfrom the unneeded gas.A screenis located upstreamof the pressurerelief valveto preventany particles of propellant or residue from enteringthe valveor the remainderof the system. The TVC pressurization system typically is activated either by firing a squib valveat the compressedgas tank outlet or, if a gas generator is used, by igniting the gas-generator propellant. In either casethe releasedpressureactsto break the tank outlet membraneseals (if the tank is so sealed) to fill the lines and injectors rapidly and then provide high momentum to the fluid jets dischargedinto the nozzleexhaustflow. An LITVC systemis not activated until about a secondbefore motor ignition; however,if the systemis activated but not launched,then the fluid and pressurizationdevicesmust be replenishedbefore another launch can be attempted. An exception is the Titan III LITVC system,which is filled with the fluid and pressurizedin the standbystate andrequiresonly electrical activation and the burning off of sealsat the injector port opening(ref. 114).
98
2.2.2.4
LIQUID
STORAGE
EQUALIZATION
When the system liquid distributed shifting excessively.
has two or more tanks, it is sometimes necessary to keep the weight of evenly between the tanks to prevent the vehicle center of gravity from A device such as an interlocked flow-drive positive-displacement pump
is used
the discharge
2.2.2.5
to equalize
DISPOSAL
from
OF SURPLUS
the tanks.
INJECTANT
LITVC systems almost always use liquid at a rate lower than that provided for in the design. This difference occurs because enough liquid must be carried for the worst possible flight control situation. Actual flight thrust vectoring requirements vary from vehicle to vehicle according penalized
to the mission requirements. by having to carry the excess
Some weight
flights of the
needing little vectoring liquid and not benefiting
would from
be the
added thrust resulting from liquid injection. To prevent this unneeded liquid from penalizing the vehicle performance as additional inert weight, provision is made to jettision this liquid and obtain thrust from it during its disposal. Flow meters are installed in the liquid lines to measure the amount of liquid used of liquid used. Flight control repeatedly compares and
signals
the
injectors
to expend
the
excess
motor thrust will be augmented expenditure of the excess liquid injectors and the rocket exhaust.
without and axial
2.2.2.6
MOTOR
Important exhaust dynamic
ADAPTATION
OF THE
advantages
of
LITVC
jet and usually does design of the nozzle.
are
liquid
thrust thrust
FOR
that
and the
an integrator sums the total amount total used with the programmed use
uniformly
around
the nozzle
so that
deflection. The vehicle is lightened is gained as the liquid leaves through
the by the
LITVC
it requires
only
light
protection
not complicate the structural design The design effort required to adapt
from
the
hot
of the motor or the gas the motor for LITVC is
simple and is limited to providing for (1) erosion in the nozzle around the injection ports, (2) shielding of LITVC system components from exhaust plume heating, and (3) possible structural reinforcement of the nozzle and motor aft end to accommodate the fixed loads of the LITVC system and the dynamic loads due to vectoring. The non-axisymmetric pressure in the nozzle due to injection must be provided for in the nozzle design. This pressure creates circumferential bending of the nozzle in a direction in which the nozzle typically has low stiffness. The exit cone diameter will increase in the direction of injection and decrease in the direction at right angles to injection. exit-cone structure may have to be increased. Provisions
for
erosion.
-
the liquid jets are injected within the injection ports
The
injection
In large
ports
into the exhaust-gas in the wall of the
99
nozzles
are the holes
of lightweight
in the nozzle
flow. The injector nozzle (figs. 29,
orifices 30, and
construction,
liner
through
the
which
are safely recessed 31). The interface
between the injector and the nozzle structure usually contains a gas-tight sealsuch as an O-ring. The wall
of the
nozzle
around
and
downstream
produce a characteristic pattern of deep grooves that begin on each
grooves side of
of the
injection
and ridges an injector
ports
erodes
(fig. 34). Typically, port and extend
abnormally
to
there are two aft (sometimes
spreading out in a V-pattern), a crescent of moderate erosion around the leading edge of the port, and a ridge of almost uneroded surface extending directly aft from the port. The chemical and gas dynamic effects that produce these effects have been studied by analysis and test The
(ref.
amount
119). of erosion
depends
on the
material. If a reactive injectant over which the exhaust-gas/injectant
such
reactivity
of the
injectant
and
the
as strontium perchlorate is used, the mixture passes usually has greater than
type
of ablative
entire wall area normal erosion;
typically, this erosion will be twice normal or more. Low-cost materials were considered for the 260-in. (6.6 m) motor, but subscale tests showed that these materials would be severely eroded
(ref.
119).
An inert injectant such as Freon if there were no injection from region
where
the
shock
The edges of holes severe erosion by downstream
edges
wave
will produce a cooling effect, and erosion will be less than the hole at all. However, at the outer edge of the mixture
contacts
the
wall,
the
through which the injectant the hot exhaust gas; this of
the
holes.
If
injection port and the adjacent nozzle The holes usually are tapered conically
erosion
erosion enters erosion
is allowed
is increased
slightly
over
the nozzle can be subject usually is concentrated to
degrade
wall, LITVC performance and are just large enough
the
geometry
normal. to very on the of the
may be reduced to accommodate
(ref. 47). the liquid
jet so that gas circulation and consequent heating in the hole will be minimized. are relatively small, having diameters less than about six times the boundary layer
Holes that thickness,
erode only moderately, because the supersonic gas stream tends to skip over the hole. However, large holes erode severely and are subject to a high rate of heat transfer on their downstream edge, because the high-velocity gas impinges against the downstream edge as if against an obstacle (refs. 134 and a large number of small orifices in efficiency. The problem of erosion overcome by making the holes as material such as graphite/phenolic. Minuteman III third-stage motors. in reference
135). This hole-size effect has provided a reason for using addition to that of obtaining greater side-specific-impulse in the immediate region of the injection ports has been small as possible, and by use of inserts of erosion-resistant This method was used in the A3 Polaris second-stage and Data on erosion of nozzle liners due to LITVC are given
119.
Thermal protection of LITVC system. - The LITVC system must be protected from heating by radiation and sometimes by gas circulation from the rocket jet plume. In some instances, this heating has been sufficiently great that liquid in unprotected tanks and tubing boiled,
100
! _
_iiiiii
ii
i iii_i_!ii¸¸
i
i i_
i ii!ii
i!i¸¸_¸ii¸_i_i¸ii
ii_ii!i_i il_
i i iiii_i
ii_ • _iiiiiii_i_ ¸_¸i i_iii!
!
i_i_%_i_i_i
'_,_,_'_ii_'," _'_"_ __i,,_i_!,_i '
iiiiiiii_i_iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!!ii!iiiii!!_!_
10t
control
circuitry
burned
and
malfunctioned,
However, the problem is easily solved, weak or negligible gas flow. Adequate as a thin layer plume and the Structural transmit mount motion
the
of sheet cork or rubber. Sometimes LITVC components (fig. 28(b)).
reinforcements.load to the
The LITVC nozzle, the motor
the entire LITVC system between the nozzle and
from
a fraction
lines
of an inch
or expansion
The dynamic nozzle. The
and
joints
bracketry
and
pressure
vessels
failed.
since the heating is passive and accompanied by only protection has been obtained by light insulation such a panel
system aft end,
is installed
between
the exhaust
is usually, supported by brackets or both. Generally, it is advantageous
that to
on the nozzle in order to avoid any problem of differential the motor aft dome or skirt. Such movements have ranged
to several
inches.
When
nozzle
mounting
is not possible,
flexible
are provided.
loads caused by liquid jet produces
LITVC are a reaction
the direct result of injection of liquid thrust like a small rocket motor. This
into the reaction
amounts to a significant fraction of the total side force. It is withstood by the injector mounts to which the injectors are bolted and the adjacent nozzle structure.The emerging jet both blocks and mixes with the flow to produce a pattern of local loads on the nozzle wall (figs. The
23, 24, and 25). character
of this load
can be best
understood
by
considering
the
nature
of the
liquid
injection effect in detail. Close to the hole, the jet acts like a solid object in blocking the main flow. A detached bow shock forms upstream of each jet and causes a large and abrupt increase in wall pressure upstream and along the sides of each injection port. Fluid dynamic shear breaks the drops of liquid into tiny droplets that rapidly evaporate and mix with the exhaust
gas. This mass,
thus
added
and mixed,
increases
the
density
and
pressure
in the
local
gas flow. If the liquid is chemically reactive, it adds thermal energy to the local portion of the main flow, which further increases its pressure. In either case, this portion of the exhaust flow that has been augmented by liquid injection expands and accelerates in a manner
similar
to,
but
more
energetically
than,
the
rest
of
the
exhaust
flow.
It
thus
undergoes a greater change in local momentum than do normal (unaugmented) portions of the exhaust flow, and this change is transmitted to the nozzle wall as increased pressure. The increase of wall pressure due to addition of injectant mass and energy to the gas stream travels
with
the
flow
all the way
to the nozzle
exit,
spreading
out in a broad
fan-shaped
(fig. 24). The
forces
area , ;
described
combine
to
produce
the
total
thrust
vector
control
force
caused
by
liquid injection. If the liquid is reactive, the total side force is 11/2 to 3 times greater than that produced with an inert injectant. The increase is due to higher pressures resulting from reaction of the injectant with the gas. Comparative breakdowns of these effects are shown in table
XIII.
A method wall
that
is presented
has been
used
in reference
for estimating 136.
LITVC
these operation
102
forces
and
produces
their
distribution
asymmetric
on the nozzle pressure
loads
on
Table XIII. -
Side Force Composition
for Inert and Reactive Injectants
(refs. 124 and 127) i
Percent of total side force Side force component Inert liquid
Reactive liquid I
i
a
Reaction thrust of the fluid jets
15 to 30
5 to 15
Pressure from shock waves
25 to 50
l0 to 30
Pressure from addition of mass
20 to 50
60 to 85
and energy to the exhaust flow
the nozzle equal to the vectoring side force. These loads usually are widely distributed and cause stresses that are not significant increases to the stresses due to symmetric gas flow. Other load conditions, including handling and assembly, ground level thrust, altitude thrust, vibration, withstand loads due wall exit
and thermal loads, result in exit-cone asymmetric LITVC loads. However, to LITVC are usually the primary loads cones
designed
for minimum
It is general practice to predict Pertinent test data are then used those for erosion, calculations. The ensure
operating
and sometimes results of the
Performance
Use
test
of
than adequate to the asymmetric nozzles with thin-
weight.
the heating, to check the
erosion, accuracy
and load conditions by calculation. of the calculated results, particularly
to evaluate the validity of empirical constants used in the analyses are used to modify the design, if necessary, to
integrity.
2.2.3
conceptual
designs that are more as mentioned previously, for large-expansion-ratio
data design
Evaluation
dominates
all
to full-scale
operation,
phases
and Testing
of
LITVC
because
103
the
performance technology
analysis of the
from
LITVC
the
effect
early is still
basically empirical. Early in a
development effort, data are obtained from the literature. These data are generalized by nondimensionalizing, cross-related by plotting, and then are transformed to the new operating conditions by use of relationships based on physical laws. This method results in some unavoidable errors. Later, subscale tests are conducted to provide Finally,
data the
under conditions full-scale rocket
capability is demonstrated. the LITVC system operates
2.2.3.1
PERFORMANCE
In the early being made
data
usually
are similar is tested
to those with its
Operating-capability as designed.
DATA
stages of the to determine
performance
that motor
FOR
tests
are
of the LITVC
particular system,
routine
procedures
to ensure
that
DESIGN
development the general
period when optimization configuration of the motor
available
design problem. and its vectoring
are
those
generated
and tradeoff studies are system, the only LITVC
in previous
LITVC
development
programs. Data from at least ten LITVC development efforts are available (refs. 46, 48, 50, 51,107, 109, 121, 122, 124, through 127, 129, 133, and 137 through 142). These data usually are reduced to standard plots and correlations (sec. 2.2.3.2) for comparison with the particular The
motor
methods
being
designed
and
and
correlating
of plotting
for generating LITVC
performance data
estimates
generally
involve
for new converting
systems. the
data
and parameters to dimensionless ratios that eliminate factors of secondary importance LITVC (e.g., the parameters of the main rocket motor). Thus, thrust vector capability
for is
expressed as side-force specific impulse, the thrust vector deflection is the ratio Fs/Fa, and the injection rate becomes the ratio of injectant flowrate to nozzle exhaust flowrate. Similarly, the location of the injection port in the nozzle is expressed as the ratio of its distance from the throat to the distance from the throat to the exit (X/L). In the resulting plots (figs. 35 different basic
through 42), different efficiencies; the upper
sets of data appear as different curves and curve invariably indicates the more efficient
represent injectant
or condition. The side
most force
a form
popular and generally useful to axial force or deflection
that
(sec.
2.2.1.5).
The
next
angle) plot that weight
is ready
most
versus
the
for
use
plot is that angle (figs.
in estimating
common
plot
presents
ratio
of injectant
the
the
of side specific impulse versus the ratio 35, 37, and 42). The data are presented fluid
ratio
flowrate
of side
and,
consequently,
is useful
conditions.
104
of analyst, that have for
and
force
to exhaust-gas
is not as convenient for use by the designer it reduces the scatter in data from motors flowrates
required
comparing
the
to axial
flowrate
maximum
force
(figs.
36
(or and
of in
flowrates
deflection 38).
This
but has the redeeming feature varying chamber pressures and data
from
diverse
sources
or
160 i
I
O_
Freon
O
X
I14-B2
injectant
\ 14(
o o
\
!
Z v
\
E .o
\ 120
o !
i i
_o
\\ i00 °_
°_ U_
O.
8C
4-I
O
6C 0
0.02
L
I I°
0o
,_Data
band of full-scale
Polaris firings
e = 14 X/L= 0.3 • = 0° Pinj=
500-750 Ibf/in.29 (3,447-5.171 MN/m-)
0.04
0.06
I 2°
I 3°
_Small data
0.08 I 4°
I
scale, F a = 1080 Ibf from LOX/RP-I motor
e = I0 X/L= 0.3 • = 0° Pinj = 750 Ibf/in_ 2 (5.171 MN/m _)
Figure 35, - Comparison of small-scaleand full-scale data on injectant specific impulse vs deflection angle and side force (ref. 121).
105
Fs/F a 0
(4804
N)
0
Fs/Fa
Constant 60_
area
pressure,variable
Pinj = 750
50
Pc = 728
injection Ibf/in'2
(5.171
MN/m 2)
N204
Ibf/in. 2
e=
8
Six
orifices
(5.019
MN/m 2)
_
j
NaC 104
7_/o H202
/
NaC I04
50?0 H202
/
NaC i04
307_ H202
40_
30_
Motor parameters (except for N_O 4) P = 375 Ibf/in.2( 2.586 MN/m_)
O /
Freon
e a
jo j 2°
= I0 = 17.5 °
F a = 1080
(4804.1
Wa = 4.0 Ibm/sec d
= 1.50
N)
in.
(1.814
(3.81
kg/sec)
cm)
t Pamb=l.5
ibf/in. 2 (10.342
LOX/RP-I
propellant
kN/m 2)
--
Injection
00
Ibf
--
/ 10
C
I14-B2
parameters
_nj = 2.45 X/L = 0.3 @ = 0°
_
0
0.04
0.08 Injectant Exhaust-gas
Figure 36. - Comparison
O. 12
0.16
Triple
orifice OLo.5 i(1.27
flowrate flowrate
of performance
of inert and reactive
injectants
(data from
refs. 121 and 142).
in. cm)
300
!
Sr
(CI 04) 2 injectant 6.
.
6
E .m ,--4
-j %
cO
'
I i
260
u_ ,m
_ _ 24o "_
x
L
220
-I
_ 2oo _z ---__. 180 ¢ = 25 ° o -.j 160
¢= 0o 140 0.3
0.35
0.4
0.45
0.5
0.55
2.18
2.45
2.73
3.04
3.35
3.68
X/L
6inj 2.14
2.26
Data
at
2.34
a constant jet
Figure
37. - Effects
of injection
2.42
F /F value s a deflection angle
location
2.51
of of
0.026,
which
2.59
M. znj
corresponds
to a
1.5 °
and angle on injectant
specific
impulse
(ref.
108).
Fs/F
0
a
m
I Sr
1 (Cl
1
04) 2 [
I
injectant f
\
6°
\ 5o_
4 ° _
//
3o_
b
\
f f
\
/
0
=
Pinj
/_
Pinj
Mmlm2)
1500 Ibf/In. 2 (10.34 I 800 Ibf/in. 2 (5.516
=
MN/m2)
/
2° -
Y
io_
0 O_ 0
0.I
0.2
0.3
0.4
0.5
0.6
Injectant
P
= c e =
800
a =
20 °
F a
=
Wa =
Figure
38.
2 (5.516
Injection MN/m
2)
7.4
7.9
- Effect
_nj
=
X/L=
ibf
(8896
Ibm/sec
of
injectant
N)
(3.583
i .0
parameters
2.45 0.35
=
2000
0.9
flowrate
parameters
Ibf/in.
0.8
flowrate
Exhaust-gas
Motor
0.7
25 °
Single
orifice
injection
kg/sec)
flowrate
and
108
injection
pressure
on
side
force
(ref.
108).
Fs/F a
0
I Freon
i13
injectant
4 °-
04
2 ° --
O-i o --
00 --
i
0
0.2
0.4
0.6
0.8
X/L
Pinj
=
do/d t Single e = i0 Pc _=
Figure 39. - Effect (adptd.
=
variable
=
Ws/Wa
=
0. i
A
_s/_a
=
0.2
_s/_a
= 0.3
_s/X_a
=
0.073 orifice
375 0°
of injection from
O
Ibf/ino
injection 2
(2.586
MN/m 2) <>
location
and orientation
ref. 109).
109
on side force for different
0.4
injectant
flowrates
140
!
!
Freon
I14-B2
injectant
r-4
Constant
O
injectant
flowrate,Ws/W
I
! tH #m
12C
e = l0
a
: 0.05
Original
data
'
I /
/ I i00
/
/
m 40
v
Transformed 40 O O
data
8O
=
60 400
0
800
Injection
:
_e
e =
e =
The
aata
the
: ein j: _
Pinj(e=7)
were
2 2)
P
= 0° =
c
used
to
calculate
the
I0 2.4 2
375 ibf/in. (2.586 MN/m
values
2)
for
relation
injection
pressures
were
= (Pinj/Pc_=loX
Figure 40. - Transformation (adptd.
145)
25 °
I0
7 by
2 (MN/m 2 x
_me
= 800 ibf/in. (5.516 MN/m
2OO0
1600
2.1
_:
The
pressure,lbf/in.
7
einj: Pc
1200
from
related
110
the
expression
Pc(e=7)
of data on injection ref. 121).
by
pressure vs injectant
specific
impulse
900
I
I Freon
I14-B2
I
800
injectant
I 3
annular
I orifices_
/
700
600 OO
o
_One
ann_u lar
orifice
50O z v
/
4OO U O
300 Note:
°rq
Orifices
circumferential
located line
on
on
a
nozzle
wall
200
I00
/ 2
0
4 Injectant
6 flowrate
(kg/sec
Figure
41.
- Effect function
of
number
x
Ws'
111
I0
ibm/sec
2.2046)
of annular
of injectant
8
flowrate
orifices (ref.
on side force 124).
as a
12
240
Sr
(CI
injectant
04) 2
Contoured Pinj
r-. o_ o
0-__
200
0
_,
Minuteman
= 750
X/L
nozzle
e = 23.5, e i= 12.5 Pc = 500 11 _in. 2 (3.447 Fa
X
_
i
=
16 001
= 290'
Ibf 2 =
data
= 0.55
(71.17
MN/m 2 ) kN)
16°
--E
o0
160 l
Design
z
cur
v
0
Pc = 400 ibf/in. 2 _2.758 MN/m 2) Pinj = 800 ibf/in. (5.516 MN/m 2)
_Q
_ i
X/L = 0.5, _ =25 ° , ein_ = 6.5 _ i = 330, _2 = 230
120
Ibf/in.
2 (10.342
MN/m 2)
bO 80
P
I
"
I
le
da_! _'_
_
--..nj =
,4
o arls
conzca
nozz
e
a a
_.._.........._._
O
.4
P
= 400
Ibf/in.
2
(2.758
MN/m 2 )
C
40 e=
19_
einj= X/L=
6.5 0.5
ibf/in.
= 25 ° =
27.5 °
I
Triple
2
Fa =
H
Wa
1050
ibf (4671
orifice
Variable = 4.0
injection
N)
ibm/sec(1.81
do
kg/sec) -I 0 =
.01
0
.02
.03
tan I .04
Fs/F a .05
.06
I
I
;
i
0o
io
2°
3°
Figure 42. - Transformation of performance data for strontium perchlorate injectant (adptd. from ref. 108).
.07
Fs/Fa
I
e
4°
2 (5.516
MNIm 2 )
Other some (figs.
useful LITVC
graphs design
37 through
are made to meet special design needs parameters on side specific impulse,
40).
The LITVC performance data accumulated represent motor configurations and operating motor and LITVC system being designed modification. The data is transformed from conditions
by applying
one
or more
For inert liquids been shown to
the momentum be the factor
impulse
changes
due
to
momentum principle shown in figure 40.
physical
in flowrate,
used
nozzle
this method is correlated residence
occupied
pressure,
to transform
the
laws that
data
available
appear
to be dominant.
energized
for injectant
or
density
through
(ref.
a change
total nozzle gas flow has changes in side specific 107).
An
in nozzle
example expansion
of the ratio
is
is the dominant effect. Accordingly, the most are based on the relative enthalpies and the fraction flow
for transforming data collected with a parameter representing time
The effects ratio have
by
from previous LITVC development programs conditions that are different from those of the and, therefore, cannot be applied without the original test conditions to the new design
of the injected flow relative to the that could be used to predict the
For reactive injectants, energy release successful data-transformation methods of the
and generally show the effect of force ratio, or thrust deflection
(refs. for one nozzle
mixing
and
143
through
146).
Figure
43 illustrates
reactive injectant. Side specific pressure and thermal energy
impulse and the
reacting.
of changes in nozzle geometry such as divergence angle, contour, and expansion been transformed by use of geometric, gas dynamic, and oblique shock wave
relationships. Some of the changes in nozzle geometry and can be transformed by simple geometric or vector summation
injection methods
geometry and spacing (ref. 107).
For changes in injector location or nozzle length, the coefficient of thrust relationship, separated into portions that are in or out of the injection region, can be used. The injection effect can then be assumed to change in proportion to the fraction of the motor thrust that originates in the injection region. This approach tends to favor injection at upstream locations in the nozzle, making it necessary to include a calculation of the degrading effect on the side force of the shock wave caused by injection when the shock wave reaches the other
side of the nozzle
(refs.
107,
126,
and
147).
A variety of computer programs for predicting the LITVC effect exist, but not one of them has adequately predicted the side force effect, because these programs are limited in the range of phenomena assumptions on which energy shock; reaction
addition; droplet with
thermochemistry,
that they they are
represent based are
displacement without breakup, vaporization, momentum interchange; and
shock
generation.
and the linearized
realism of supersonic
their results. Some of the flow with mass, bulk, or
mixing; boundary-layer separation and induced and bulk formation; mixing, vaporization, and and liquid breakup, mixing, vaporization, Use of these
113
computer
programs
has been
inhibited
2OO
E
O
150
!
J
O
,-4 O.
i00 O
J
U
v
Sr(Cl04) 5£ O 0J
2
Pinj
=
2°
jet
injectant
1500
Ibf/in.
2 (10.342
deflection
MN/m
2)
angle
i
I00
200
(
300
Ps,inj
400
T3s,inj
d
5 00
)1/2
Vinj
Nozzle
parameters
Pc
Ps,inj
Ts,inj
ibf/in.2 einj
Symbol
O ® Z_
2
x
145)
(K
9/5)
ft/sec
(mx39.37)(m/sec
x
6.2
3.00
375
3010
2.66
8800
3.2
2.48
800
44.8
3550
1.83
7940
19
3.0
2.42
375
23.6
3620
3.74
7820
19
3.0
2.42
650
41.0
3620
3.74
7820
19
3.0
2.42
800
50.4
3620
3.74
7820
2. i
2.12
800
85.5
3980
2.57
7200
The
correlation
the
parameters
- Correlation (adptd.
of from
shown listed
injectant ref.
should
8.6
x
in.
j
7
Note:
43.
(MN/m
oR
Vin
19
7
Figure
Mini
d
be considered
in the above
specific
122).
114
valid
only
within
the
range
table.
impulse
with
key
nozzle
parameters
of
3.281)
by
lack
of
empirical
correlation
with
correlations
2.2.3.2
the
data.
for transforming
SMALL-SCALE
Early in information
test
Therefore, data
(ref.
the
general
practice
has
been
to
use
51).
TESTS
development on which to
period, the designer needs only approximate parametric define optimization studies and preliminary designs. Existing
LITVC data are employed as far as possible, transformation-correlating methods being used to transform the data to the current design problem. The transformed data are approximate at best and contain errors that are in proportion to the differences between the motors from which
the
data
came
and
the
motor
being
designed.
As the
design
proceeds,
better
data
are
needed; these data usually are obtained a variety of LITVC arrangements that
from tests of scale models of the motor nozzle with are in the range of design interest. There is little
scaling problem involved Figure 35 shows LITVC full-scale motor.
small-scale model from small-scale
in translating data obtained
A small-scale test series includes sufficient data for construction pertinent features
ranges of variation in the test conditions of the plots and correlations needed
design parameters (sec. 2.2.3.1). that represent its larger counterpart
injection
geometry,
2.2.3.3
and
FULL-SCALE
ambient
Also, the small-scale motor in propellant gas properties,
scaling
are
DEVELOPMENT
eliminated
high-confidence in the horizontal
data at the or vertical
and
possible
earliest position.
LITVC
time. The
tank
and
bladder,
quality
tubing,
insensitive and
design
Static tests orientation
is designed with nozzle geometry,
first opportunity, usually the first tests, errors of data transformation
changes
are detected
and
defined
by
are usually conducted with the motor of the motor is considered in selecting
for the
static
test
to allow
for the change
L ITY TESTS
The operating capability of the parts and determined at various stages of manufacture, relatively
that will provide to establish the
TESTS
the orientation of the LITVC tank and plumbing in direction of gravity force on the liquid.
2.2.3.40PERATING-CAPABI
a
pressures.
A full-scale test of a LITVC system is conducted at the static test of the full-scale rocket motor. In the full-scale and
data to a full-scale counterpart. tests compared with data from
fittings,
to malfunction
flow after
components assembly,
meters,
and
they
have
operability.
115
of the storage, check been
LITVC system are regularly and launch preparation. The
valves tested
have
been
to demonstrate
shown
to be
specified
The
most
critical
components
are
the
injector
valves
and
the
pressurization
system
because
they are sensitive to malfunction. Surveillance tests to monitor the operating capability of these components have been developed (ref. 46). The injectors are evaluated in bench tests with an inert liquid (e.g., Freon) that evaporates and leaves the components clean. While this evaluation is not fully representative of actual conditions, it is sufficient because it provides an
effective
functional
nonevaporating necessary. After on the
motor,
injectant assembly these
response through storage or launch When
test
of the
components
a gas generator
is used
for continuity
pressure checked
is monitored for electrical
A complete check rocket motor; this
and
without
degrading
is used in bench testing, thorough and installation of the injector valves are tested
the electric readiness.
voltage
components
feedback
to pressurize
resistance.
by actuating
loop.
These
the
injectant, of inert
by pressure gages. The squib continuity and resistance.
valve
the
igniter
at the
means
components after without activating
above,
it is possible
to
check
the system has been installed and it or disturbing its launch readiness.
116
the
the
function
charged
with
the
during
at low
is used,
the gas
of the inert-gas
of injector valves sometimes is conducted while check is accomplished by connecting an auxiliary
discussed
desired
is checked
pressure
outlet
or
testing is system
and checking
when
squib
at high
liquid into the LITVC system, actuating the injectors, and noting used is inert and evaporative to avoid contaminating the system. By the
valves
are repeated
gas
If a reactive
cleaning after and pressurization
the injector
tests
If a tank
them.
tank
is
the system is on the supply of pressurized response.
The
of all critical injectant
and
liquid
LITVC gas
but
3.
DESIGN
CRITERIA
and
Recommended 3.1
Practices
FLEXIBLE
JOINT
3.1.1
Configuration
3.1.1.1
DESIGN
OPTIMIZATION
The flexible joint design shall be based on the movable-nozzle constraints and joint, motor, vehicle, and mission design parameters either maximum performance or maximum cost effectiveness, depending The
basic
motor
rate, actuation environmental possible, designer.
on specific and
needs
vehicle
acceleration, conditions)
and characteristics
joint
design
of the program.
parameters
(motor
flight inertia loads, should form the basis
optimization analyses. The following procedure optimum joint design (i.e., the least expensive without violating any imposed restraints): Calculate reference
(2)
Prepare a anticipated parameters:
(3)
Vary
constraints, initial joint
anglel mass design.
actuation properties, Whenever
as explicit design points to the joint must be established on the basis of
is recommended joint that satisfies
for establishing the all mission objectives
against
for this motor should call for state-of-the-art materials, philosophy expected for the operational system, and be for all loading conditons. Calculate motor performance, and
which
the independent
weights
other design
for this
designs
independent
and
optimization parameters
parameters
analyses for use in the
117
motor
design.
will be compared
pivot point, and cone angleand nozzle design, motor performance, tradeoff
at some
preliminary layout drawing of a motor approximately the size for use in the vehicle. This motor is designed to a particular set of motor pressure, joint actuation torque, pivot-point location, and cone
performance,
design
vector
the required nozzle vector angle that will produce a side force position consistent with the vehicle performance requirements.
angle. The drawing embody the design structurally adequate joint
pressure,
envelope for the
the joint design parameters should be provided Otherwise, these interdependent design points
(1)
envelope that result in the choice
- motor
determine and cost to
motor
pressure,
is the
baseline
an optimum
design.
joint
actuation
torque,
their influence on joint design, if considered. Continue to perform
obtain
final
This to select
design.
the
near-optimum
values
of the
Since no parametric weight-scalingequationsare availablefor flexible joints, the basic joint design should be varied geometrically for pivot position, joint diameter, and cone angle; and the effect of these parameters on weight at different motor pressures and spring torques should be calculated. Conduct structural analyses,using the empirical relationships of section 2.1.5 to establish joint component thicknesses.Layout drawings of the nozzle andjoints should be prepared and compared with envelope constraints to establish limits for joint geometry as a function of pressureand spring torque. The joint weights as a function of motor pressure, spring torque, and geometric limits should be included in motor andvehicleoptimization computerprograms. (4) Make new layout drawings basedon the near-optimum values of the operating parameters and check to ensure that computer-predicted weights, lengths and volumes,and performancesarevalid. To ensurethe validity of the design,perform necessary calculations external to the generalized computer program; e.g., structural analysis(sec.2.1.5), detailed weight calculations,and grain design. Steps3 and 4 should be repeatedasnecessary.The joint designcharacteristicsresulting from this procedure must be consistent with the required motor characteristics and with near-optimum systemperformancewhen all stagesareconsidered. The dependent design parameters considered in sections 3.1.2.3 and 3.1.2.4, the independent design parametersconsidered in section 3.1.2.5, the material properties (sec. 3.1.3), and other important parametersincluding internal pressure,axial load on the joint, flight loads, and loads resulting from the particular motor or vehicle configuration (sec. 3.1.4) should be included in the optimization analysis to the extent required by the particular application. Specific recommendedpracticesfor componentcost analysiscannotbe madebecauseof the many complexities involved. Cost-estimatingtechniquespresentedin reference 148(ch. X) should be usedas a guide. The generalrecommendation for cost analysisis to establishthe joint design and then to continue to improve the design with cost effectivenessas the criterion. The mission performanceof the vehicle should be maintained constant for each design alternative evaluated.The analysismust include the cost of all motor components redesignedasrequiredto maintain constantvehicleperformance.
3.1.1.2
ENVELOPE
The
values
joint
can operate
It is recommended nor
greater
than
for
LIMITATIONS the
inner
and
outer
joint
angles
_1 and
{32 shall
so that
angle/3_
ensure
that
the
as required. that
the
45 °, and
flexible angle
joint
_2 is not
be designed less than
118
45 ° nor greater
than
is not
less than
55 °. (All
40 °
successful
joints to date have operatedbetweentheselimits, but joints with largervaluesfor/31 and t32 may be possible). To reduce consistent with the allowable compression
3.1.2 3.1.2.1
spring torque, the difference (/32 -t31) should stresses in the elastomer and reinforcements
requirements.
Design Requirements ACTUATION
TORQUE
The total actuation torque -consisting offset torque, inertial and gravitational be less than The
be a minimum and any axial
total
actuation
dependent contributing
on
the
torque
available
torque
is the
of foint torques,
from
spring torque, frictional and aerodynamic torques
torque, - shall
the actuator.
summation
of all the
contributing
torques,
each
of which
the specific design of both nozzle and motor. It is recommended that torque, including the variability of the torque constituents, be calculated
is
each for
the full range of motor service life. The service life consists of (1) vectoring for checkout at zero motor pressure and (2) vectoring over the entire range of motor operating pressures. Use the maximum actuation torques (nominal determine total required actuation torque, and actuation necessary
system. statistical
3.1.2.1.1
Joint Spring Torque
The ]oint
A valid statistical analysis data will not be available
spring
torque
shall
be the
plus maximum variability) thus obtained to compare this value with the capability of the
is not possible at this point of design, since until a joint is designed, built, and tested.
minimum
required
to fulfill
motor
the
operating
requirements. The joint spring material properties
torque should be calculated obtained in a subscale test
by the methods of program (sec. 3.1.7.1).
section 2.1.2.1.1; To establish the
use range
of probable variability in spring torque, calculate the joint spring stiffness at zero motor pressure for the maximum and minimum elastomer shear modulus. This range should be assumed to exist at all motor operating pressures. The
spring
actuator. control
torque
at the
maximum
The spring torque system. If the joint
value
of shear
at the minimum is to be vectored
modulus
is used
in the
design
of
the
value of shear modulus affects design of the to different angles during motor operation,
take advantage of the reduction in spring torque due to motor pressure to reduce the actuation power requirements. Calculations using the average elastomer shear modulus must be made of the joint spring torque during motor firing. The expected variability calculated at
zero
motor
pressure
must
be
superimposed
119
on
the
average
values
to
establish
the
maximum and minimum spring torques. It is desirablethat the minimum spring torque be sufficiently large to prevent a negative joint spring stiffness due to pressure.If a joint designedto be vectored at pressureis to be vectoredat zero pressureduring motor preflight checkout, the vector angle at checkout must not result in a joint spring torque greaterthan that occurring during motor operation. 3.1.2.1.2
Friction
The
joint
shall
stability Neither
Torque demonstrate
of the flight
the
coulomb
coulomb
control
friction
and
nor
the
viscous
design. Both frictions should be measured time of relatively constant motor pressure three
or
four
different
cycles at each actuator force actuation
rates.
viscous
friction
consistent
with
the
system.
The
wave
friction
can
be
estimated
during a static firing. be selected and that
form
should
for
preliminary
It is recommended that a the nozzle be actuated at
be sinusoidal
and
run
for
at least
IIA
rate to avoid the force transients that occur at the start and stop points. Plot variation with either vector angle or actuator stroke for one cycle at each
rate,
and
determine
the
average
actuator
force
at zero-degrees
vector
angle
(fig.
14(a)). The test data should be smoothed and the actual instantaneous actuation rate at zero-degrees vector angle determined either by calculation or by use of a plot of vector angle Variation with time. The variation of actuator force at zero vector angle with actuation rate should
be plotted;
friction
(fig.
3.1.2.1.3
record
the
zero
intercept
as the
friction
and
the
slope
as viscous
14(b)).
Offset Torque
The flexible-joint and movable-nozzle consistent with reasonable manufacturing A value
coulomb
for
determine
offset
torque
pressure
cannot
distributions
offset torque shall practice and cost.
be calculated around
the
unless
movable
be a minimum
air cold-flow nozzle.
For
tests joints
are
value
conducted
to
up to 22 in. (55.88
cm), the offset torque is small compared with the joint spring torque, and it is recommended that it be ignored in estimating actuation torque. For larger joints, an assessment should be made of the offset torque, pivot-point movement (sec. 2.1.2.3) being considered
and
measured at
worst-on-worst
during
a minimum
requirements, 3.1.2.1.4
by and
Inertial
The actuator the
the
moving
bench
tolerances test
maintaining motor
being
program.
assumed.
The
It is recommended
minimum
tolerances
offset that
consistent
torque
should
also
the offset
torque
be kept
with
design
due
to the
practice,
cost
requirements.
Torque torque
shall
provide
for
the
nozzle.
120
maximum
torque
inertia
be
of
The inertial torque should be estimatedfrom the massof the movablenozzle assumedto be rotating about the geometric pivot point. It is recommendedthat half of the weight of the flexible joint be included with the movable section in calculating movable nozzle weight, center of gravity, and dynamic moment of inertia. It is recommendedthat the maximum inertial torque be included in the actuation torque. 3.1.2.1.5
Gravitational
The actuator accelerations. Calculate
the
Torque
torque
axial
and
shall
lateral
provide
accelerations
vehicle pitch accelerations
and yaw. The torques should be calculated
recommended
that
3.1.2.1.6
the
maximum
Insulating-Boot
for
the
at the
acting in the
gravitational
maximum
nozzle
insulating
modulus of requirements.
boot
torque
must
be
fabricated
insulating boot must be the bellows used, a wrap-around insulating boot that
even
It is difficult
to estimate
due
to
of gravity
that
pivot point for inertial
be included
in the
vehicle
result
from
due to torque.
actuation
these It is
torque.
Torque
such
elasticity and thickness) and If a material such as silica-filled
recommended allows.
center
at the geometric same manner as
The insulating-boot torque shall be a minimum requirements and available motor envelope. The
torque
with
the
this
that
consistent
it has
with
the
a minimum
stiffness
yet is thick enough butadiene acrylonitrile
to
a bellows-type
insulating-boot
diameter, with a bellows fabricated recommended that the insulating-boot
of
torque.
boot
For joints
be used
up
(product
of
satisfy insulation rubber is used, the
type, whereas if a silicone rubber such (fig. 7) will result in low boot torques.
material
insulating
when
as DC 1255 is However, it is the envelope
to 30 in. (76.2
silica-filled butadiene acrylonitrile torque be assumed to be 35 percent
cm)
in
rubber, it is of the joint
spring torque. With the same insulating-boot material for joints approximately 90 in. (2.29 m) in diameter, it is recommended that the insulating-boot torque be assumed to be 15 percent of the joint spring torque. For designs using low modulus silicone rubber, it is recommended spring torque. 3.1.2.1.7
Internal
A ctuator The and
that
aerodynamic propellant
the
insulating-boot
Aerodynamic
torque
shall
include
torque
be
assumed
to be
25
percent
of the joint
Torque the effects
of internal
aerodynamic
torque.
torque must be estimated as a function of vector angle, motor pressure, grain/nozzle configuration for the maximum expected vector angles during
121
motor operation. The torque should be determined from a knowledge of the pressure distribution along the nozzlesurfaces,using the methods outlined in section2.1.2.1.2 (i.e., air cold-flow testsor two-dimensionalmethod of characteristics). When a joint has a forward pivot point, the total aerodynamictorque must be addedto the actuation torque, so that the actuator can be sized properly. When a joint has an aft pivot point, the aerodynamictorque should be ignored.
3.1.2.1.8 The
External
Aerodynamic
Torque
external
aerodynamic
torque
during For
in which
the
nozzle
cause
a negative
is not
shrouded
by
a motor
torque in the high dynamic pressure region that This torque should be determined from a knowledge
along the nozzle external surfaces internal aerodynamic torque. The pressure
region
3.1.2.2
NOZZLE
The
not
actuation
torque
flight.
all motors
aerodynamic estimated.
shall
must
be less than
VECTOR
vector
angle
and total
the joint
ANGLE
shall
should be aerodynamic
be
large
spring
AND
PIVOT
enough
skirt,
the
external
occurs during flight must be of the pressure distribution
calculated torque
stiffness
case
in the stiffness
to ensure
same manner as the in the high dynamic
positive
actuation.
POINT
to cause
sufficient
side force
for
vehicle
steering. The vector angle required for steering either must be given in the motor requirements or calculated from a trajectory analysis that considers pitching requirements and worst-case winds. A method for calculating the required vector angle is given in reference 149. If
the
vector
angle
is given
in the
motor
(normal distance from the line of action vehicle center of gravity) or the required It is assumed that the side force causing point,
and
the
effective
pivot
point
requirements,
the
control-force
moment
arm
of the motor thrust for a vectored nozzle to the steering moment must be stated as a requirement. a steering moment acts through the effective pivot
should
be calculated;
from
this location,
the geometric
pivot point should be determined. The geometric pivot point should be as far aft as possible consistent with optimum vehicle performance. However, envelope restrictions on actuators and exit cone movement must be considered. It is recommended that a forward pivot point be
used
submerged
for
nozzles
nozzles
with because
little the
or exit
no cone
submergence, movement
122
and requires
an aft
pivot
less envelope.
point
be used
for
3.1.2.3
AXIAL
DEFLECTION
Clearances effects Joint
axial
between
the
movable
and fixed
nozzle
components
shall allow for
of axial deflection. deflection
is the
compressive
response
of the
flexible
joint
motor is pressurized. The clearances between the movable and must be sized to allow for this movement as well as for rotational The required clearances the nozzle as it deflects The
axial
considers
should be studied through axially and in the vectored
deflection the
should
geometric
be calculated
changes
loading. As soon as possible axial-deflection characteristics spring
stiffness
3.1.2.3.1 The
must
nozzle
caused motor
be known
Misalignment
nozzle
shall
have
must
be
by motor pressure.
assembled
pressure
Efforts occurs
should be made during in a nozzle, since the
excessive follows:
during
which
misalignment
(1)
Estimate effective
(2)
Estimate
layouts
overlaid
analysis
(sec.
in at least
joint
that
the
the
to show
2.1.2.3)
four
of the guidance
control
that
increments
of
at zero
system.
pressure
that
in the
motor
at some
vector
angle
length actuators will result that the pressure at which
results
in
vectoring
such
the
vectoring
that
in alignment alignment
at a selected occurs be the
occurs.
the joint design to estimate the amount of misalignment that orientation of the actuator to the nozzle could result in A recommended
procedure
for estimating
misalignment
the axial compression of the joint (sec. 2.1.2.3) and pivot point (sec. 2.1.2.3.1) during motor pressurization. the
when
pressure.
nozzle
angles.
occurs
should be bench tested to measure the compressive spring stiffness. The axial
misalignment
pressure and fixed It is recommended
average
loading
that
fixed nozzle components movement of the nozzle.
of two
a finite-element during
for the design
motor
the use position.
program, a joint obtain the axial
a vectoring
at a selected
with
of the joint
in the and
Nozzle
alignment The
the
spring
torque
stiffness
(sec.
the
is as
approximate
2.1.2.1.1)
during
motor
determine
graphically
pressurization. (3)
Assuming nozzle operating
(4)
Assume
vectoring
nozzle
is aligned
misalignment
as the
at zero motor
pressure, is pressurized
to maximum
the
expected
pressure. that
the
nozzle
as the misalignment calculate the actuator
misalignment
that occurs null length.
required
at the
123
selected
at zero motor
pressure
zero-misalignment
is the
same
pressure,
and
The actuator null length must be checked during the static firing test program. The recommendedprocedureto determinethe actuator null length is asfollows: (1) Estimate the effective pivot point at the motor pressureat which the nozzle and motor center lines are to be aligned (sec.2.1.2.3). (2) Align the nozzle to the motor at the pressurefrom item (1), and calculate the vector angleand actuator length at zero motor pressure,consideringthat the pivot point movesfrom the effective pivot to the geometricpivot point. (3) Prior to the firing, actuatethe nozzle in the motor and determine :
per inch
of actuator
the vector
angle
stroke.
For the static firing, set the actuator length as determined in item (2) and measure the vector angle change of the nozzle at various motor pressures during the firing,
(4)
the pressures being selected held at the trial length from (5)
Compare
the
pre-firing
to give as wide a range as possible item (2) for at least one half-second.
and
firing
data
to calculate
the
at its natural
frequency
with
amount
the
actuators
of zero-pressure
misalignment.
3.1.2.4
FREQUENCY
The
nozzle
RESPONSE
shall
not
be subject
to excitation
The stiffnesses
of all parts
of the nozzle
are higher
the
frequency
than
natural
should
of the
be designed
hydraulic
so that
actuator
frequency is almost equal to the natural frequency of the nozzle and the actuator system will occur and will produce frequency is less than the system will occur. Further, mechanical destructive The
natural frequency the nozzle natural
frequencies of the motor and vehicle failure of the nozzle results.
natural
firing. The consideration
frequency
of the
nozzle
assembly should be of the control system
and
motor
subjected response,
assembly
their
system.
natural If the
frequencies nozzle
that
should
to a frequency but if this is not
is known, a notch filter should be incorporated vectoring commands at or near the natural frequency.
124
of the natural
coupling with the guidance be greater than the natural no coupling
that
be measured range known,
into
the
could
prior
cause
to static
determined from it is recommended
that a frequency range from 2 to 100 Hz be tested. If the motor is too large frequency response tests, the natural frequency must be calculated. When frequency suppress
natural
actuator system, coupling instability. If the nozzle
of the actuator, frequency must to ensure
of vibration.
control
for practical the natural system
to
3,1.2.5
ENVIRONMENTAL
3,1,2.5.1
Thermal
Thermal
PROTECTION
Protection
protection
temperature
of
limits
the
for
joint
the full
shall
enable
duration
it to remain
motor
gases
be sufficiently motor shade
and
maintain
thin
the
to minimize
joint the
vectoring. For region in order
that reduce the the fixed nozzle
the radiation to minimize
additional stagnant
The
temperature.
torque
An
component
that a radiation gas. This practice
boot torque. Provide component to allow
protectors a result of
(fig. 7(b)) vectoring
insulating
due shield allows
to the
motor
gas as the joint
boot boot.
a clearance gap between for joint axial deflection
the and
must be located in a stagnant gas as the joint is vectored. must be or motor
sufficient pressure;
to prevent otherwise,
be located in a circumferential
is vectored.
Aging Protection joint
elastomeric
oxidation
during
Polymerization conditions that determined
material
shall
pre-fabrication
of uncured maintain
early
shear specimens properties. (2)
not
be subject
to adverse
and post-fabrication
(sec. 2.1.7.1) Store uncured
by
the
following
steps:
from new elastomer elastomer at different
of aging and
storage.
elastomer should be minimized by the elastomer within specifications.
in a program
effects
storing These
(1) Fabricate stock to conditions
the elastomer under conditions must be and
establish for the
test quadruple-lap initial elastomer time period it is
anticipated the elastomer will be stored during the program. (3) Fabricate quadruple-lap shear specimens from the stored elastomer stock to establish the elastomer properties. (4) Select storage conditions to be included in the processing To
must If the
(fig. 7(a)) be used to use of thinner, more
torque is generated. It is recommended that the joint protectors region in order to reduce the size of the protectors and to minimize
of the
3.1.2.5.2
ablative protectors (fig. 7). The the erosion by the flow of the
shield to be effective, the gap circumferential flow of the motor
The gap between sacrificial thermal contact of adjacent protectors as
flow
at allowable
additional
envelope allows space, it is recommended the insulation boot from the hot motor
pliant boot materials radiation shield and
allowable
of the firing.
Protect the joint with an insulating boot or with sacrificial insulation material must be sufficiently thick to withstand hot
at or below
minimize
and test change in elastomer
specifications. changes
in joint
performance,
select
elastomeric
materials
for which
long-term
aging data are available. To protect the joint against changes in the elastomer properties surfaces exposed to ozone or oxygen, it is recommended that the joint be covered by impervious
coating
such
as chlorobutyl
rubber
125
or Hypalon.
at an
3.1.2.6
PRESSURE
The 'joint
SEALING
shall
pressure
and
not
leak
vectoring
It is recommended
that
when
subjected
to either
a pressure
load
or a combined
load.
reliable
joint
sealing
be
accomplished
by
joint molding process until unbonded areas are at a minimum to ensure that this process is continued on all subsequent should be performed to bonding of the elastomer, after joint molding by
experimenting
determine unbonded areas. For joints fabricated inspect the elastomeric pads before joint molding C-scan ultrasonic techniques (ref. 22). Joints
by secondary and the bonds fabricated by
only by cutting joints fabricated
processes
the
inspected
on
a sampling
basis
to
ensure
debonded
area
have
not
the
and then establishing controls manufacture. An inspection
compression molding and injection molding can be inspected and inspecting the elastomer surface. It is recommended that be
with
that
molding
apart a joint by molding
process
has
not
changed. Quantitative
criteria
for
that the photographs an acceptable joint, two examples
of unacceptable
Material
3.1.3.1
ELASTOMERS
for structural rate, and joint
shear
rate
properties
problem minimum
It is recommended shows shows
joints.
material
The important mechanical are secant shear modulus reinforcements shear strain
established.
Selection
elastomeric
needed actuation
been
presented in figures 44 and 45 be used as a guide. Figure 44(a) figure 44(b) shows a marginally acceptable joint, and figure 45
3.1.3
The
the
loading at temperature,
rate,
and
maximum
joint
loading
the minimum
the critical as imposed
in a quadruple-lap temperature (sec.
be determined
(ref. 78 and sec. values for these
actuation
at least
mechanical
motor pressure, by design factors
properties
vector angle, of safety.
properties to consider in the selection of the elastomeric material at 50 psi (0.345 MN/m 2 ), shear strength, and bonding to the metal
- all measured and operating should
shall possess
joint
2.1.2.1.1). mechanical temperature
as evaluated
if joint
shear specimen tested at the appropriate 2.1.7.1). The effect of compression on the
instability
due
to motor
pressure
is a potential
The materials should be selected on the basis that the properties at the critical motor pressure, vector angle, are
not
by appropriate
less
than structural
those
required
analyses
(sec.
to withstand 2.1.5).
The specific material mechanical properties should be established from pre-existing on the selected elastomer material, or these properties should be established from
126
the
test data specimen
t"--
_4 er 0
¢O r_
E o m
0
2_
¢,a
2_
E X
o |
u5 L_ 2_ °_ t,I.
128
tests (sec. 2.1.7.1). section 2.1.3.1.
3.1.3.2
Materials
that
have
been
used
in successful
joint
programs
are given
in
REINFORCEMENTS
The
reinforcement
properties angle,
material
needed
for
as imposed
The important are the modulus
shall
structural
by design
possess
loading
factors
at
at the
least
the
critical
minimum
motor
mechanical
pressure
and vector
of safety.
mechanical properties to consider in the reinforcement material to be used of elasticity, the compressive yield strength, the ultimate tensile strength,
and, for composite reinforcments, the interlaminar shear strength. For joints with metal reinforcements, the required buckling stress of the reinforcement can be calculated (see. 2.1.5.2) from the modulus of elasticity and joint dimensions. For joints with composite reinforcements, the allowable compressive MN/m 2 ). The true allowable compressive from bench testing a joint to failure (sec. basis
that
the
minimum
values
and vector angle are not evaluated by appropriate The specific representative
material mechanical of the selected
evaluation of reinforcements. composite
3.1.3.3 The
specimen Aluminum
tests. alloys
reinforcements
ADHESIVE adhesive
that
the
mechanical
be assumed to be 60 000 psi (414 laminate used must be determined materials should be selected on the
properties
at the
those required to withstand analyses (sec. 2.1.5). properties material, Steel should
critical
the maximum
should be established or these properties
motor joint
pressure loading
as
from existing data that should be established
are by
or composite materials are recommended as also be considered for reinforcements but only if
are impractical.
BOND bond
properties needed angle; as imposed To ensure
for the
less than structural
stress should stress for the 2.1.4.1). The
SYSTEM system
shall
possess
at
for structural loading at the by design factors of safety.
adhesive
bond
system
is stronger
least
the
critical
than
minimum
motor
the
mechanical
pressure
elast0mer
and vector
material,
all failures
in a specimen test program (sec. 2.1.7.1) must be cohesive. The processing of the specimen must be as nearly identical to that of the joint as possible. To maintain the quality of the adhesive bond system, controls on the system materials must be established. Systems recommended for use with injection-molded joints, compression-molded joints, and secondary-bonded
joints
are described
in section
129
2.1.3.3.
3.1.3.4
JOINT
The
The
THERMALPROTECTION thermal-protection
materials
properties
joint
needed
to maintain
joint
important
thermal
properties
diffusivity, flexibility have been
shall possess
temperatures
for the joint
at least the minimum
at or below
thermal-protection
thermal
allowable
limits.
materials
are low thermal
high heat of ablation at strain levels anticipated in service, and mechanical with minimum char fracture at temperatures expected in service. Materials that used in previous programs are recommended; these are presented in section
2.1.3.4.
3.1.4
Mechanical
3.1.4.1
GENERAL
Design
CONSIDERATIONS
The flexible joint shall possess the combination of weight and structural that contributes most to optimum motor and vehicle performance. The
flexible
joint
subjected to accompanying integrity section
the
should 3.1.5.
should
be
designed
to
have
the
required
structural
critical design loads of motor pressure and vectoring environmental conditions. Analytical verification of be made;
the
recommended
practices
for
structural
strength
capability and the the joint analysis
while
effects of structural are given
in
If axial compressive deflection is a requirement that cannot be met by a joint sufficient for structural strength, the thickness of the elastomer layers should be reduced, the result being an increased number of elastomer layers. The number of reinforcements will be increased, and these in section
should be designed 3.1.5.2. Compliance
demonstrated Because the the amount limiters storage
for structural capability according to practices recommended with the axial compressive deflection requirement must be
by test. joint has little axial stiffness in tension, the design .must incorporate limiters oia of tensile axial deflection that can occur as a ,result o;f ground handling. The
must
also
ensure
that
the
cannot
over-vector
the
joint
during
horizontal
or transportation.
The joint design should be established close to zero as possible. However, the
nozzle
guidance
less-than-optimum
control joint
system design
and
to obtain positive margins of safety since the joint design is interdependent optimum
will result
motor
in optimum
130
performance, motor
design.
it
(sec. 2.1.4.1.1) with design is
possible
as of that
3.1.4.2
DESIGN
The joint specified
FACTOR
shall
have
joint
OF SAFETY at least
the
minimum
factor
of safety
required
A design factor of safety should contingencies (e.g., approximation
be used in the design in estimation of joint
of
loading
developed variables
through involved.
(i.e.,
operational
or
handling);
these
that
define
elastomer
ring thickness,
The
reliability
the
the
joint
structural
and joint
cannot
tests and joints involved. convergence of the curves upon
number
capability
geometric
be demonstrated
failures
The not
upper
After each probabifity
and lower
3.1,4.3
have
understanding of the is not available, it is
design factor
than is applied to of safety is 1.25,
factor should be applied be applied redundantly
(e.g.,
material
been
mechanical
to the to the
properties,
explicitly
because
that the reliability
allowed
during
of the
prohibitive
number
reliability be demonstrated levels. The upper reliability the
development
and
reliability
levels
should
be set up before
of
by the level is
production
the lower reliability level is based the development and production
test, the reliability from all test results is plotted and extrapolated of achieving the required reliability. A test program to establish
FLEXIBLE-JOINT
The joint combination
safety
tolerances).
It is recommended for upper and lower of
joint. must
programs and must be greater than the required reliability; upon the calculated reliability from test results during programs. show the
of
a history of successful designs and a knowledge and Since in the design of flexible joints this history
then a factor of 1.5 should be applied to the motor pressure and to the vector angle. It
based
factor of safety could to joint performance
factors
recommended that a greater factor of safety be applied to the joint the overall motor design. For example, if the overall motor design
joint
for in
the required reliability (ref. 150). Unfortunately, there is insufficient of how these variables affect joint performance, and a single factor of safety Usually design factors of safety are specified in a design for specific classes
conditions
parameters
the
of flexible joints to account stresses, undetected variations
material properties, and undetected manufacturing deviations). The be established from a statistical study of all variables contributing correlated to understanding is recommended.
to obtain
reliability.
development
program
to the
is begun.
LOADS
stress profile shall of design loads.
include
all
individual
design
loads
or
the
worst
All design loads (see. 2.1.4.1) should be used to determine the critical design stresses. The critical joint loading condition, or worst critical combination loading, should be defined by summation of a load/time history of the joint. This profile should be prepared by tabulating all design loads, temperature exposure, critical-loading condition for each structural
and vectoring conditions element of the joint should
131
encountered. The be used in the joint
structural analysis(sec.3.1.5) than
3.1.5
Structural The joint
The
theories
should
that
margins
of safety
for the joint
are not less
be
design
Analysis stresses
necessary analyzed
preliminary and 82). The
to determine
zero.
to with
dimensions
following •
factors
Loads
shall not analyze the
and
of
joint
empirical with
be included
should
the allowable
a flexible
reanalyzed
should
used
use
exceed
stresses.
have
not
relationships
nonlinear
loads
(i.e.,
formulated.
(refs.
17
finite-element
in the requirements
be design
been
loads
79)
methods
for the
limit
and
The
structural
times
joint
to obtain
(refs.
80, 81,
analysis:
appropriate
factor
of
safety). •
Combined
loading
should
be analyzed
The maximum permissible minimum 3-standard-deviation quadruple-lap shear strain The
maximum
limited ultimate •
The loads
shear rate.
maximum should
specimen
permissible
to the loads.
shear
0.2 percent
permissible be the lesser
to determine
the resultant
stress in the elastomer should values of the failure shear stress
(sec.
2.1.7.1)
at the
tensile
stresses
in metal
yield
stress
compressive
appropriate
at limit
loads
stress
in metal
of the 0.2 percent
yield
ELASTOMER
The
elastomer
adequate The shear calculated
shear
THICKNESS thickness
shall
be limited measured
to the
and
and
should
ultimate
reinforcements
stress
to the from a
temperature
reinforcements and
be
stress
at
at ultimate
the buckling
The maximum permissible stresses in composite reinforcements assumed to be 60 000 psi (414 MN/m 2 ) and must subsequently the reinforcement laminate in bench tests to failure.
3.1.5.1
stresses.
stress.
should initially be determined
be for
..... not
be
greater
than
the
thickness
that
provides
strength.
stress in the elastomer at ultimate conditions.
due to combined motor The empirical method
132
pressure and and procedure
vectoring must be given in section
2.1.5.1 are recommended.When calculating the shearstressdue to vectoring,allow for the reduction in joint springtorque due to motor pressure(sec.2.1.2.1.1). Although the allowable shear stress at failure is increased when compression is superimposed,ignore this increasewhen establishingallowableshearstresses.
3.1.5.2
REINFORCEMENT
The
reinforcement
adequate :
The '
THICKNESS
and
procedure stress due
shall
hoop
and buckling
compressive
compressive
pressure
thickness
stress
vectoring
on
the
must
inner
be
2.1.2.1.1).
The
allowable
compressive
stress
,
from
bench
tests
of the
at ultimate
of joints
ADVANCED
The
The
design
analyzed t methods.
finite-element
method
thickness, thickness,
provide that
by
loads
to combined empirical
When calculating spring torque due
for metal
motor
method
and
the compressive to motor pressure
reinforcements
tensile stresses and fracture
methods
of analysis
must
be the
shall
involve
description be divided
should
be the
as shown must
in be
are important. The allowable mechanics properties of the
be
confirmed
be divided into and reinforcements that the analysis 2.1.5.3 be used.
average
calculated
a sufficiently
by
a minimum be divided
include
stress
133
refined
of the internal into a minimum
stresses for combined motor pressure stresses as described in sections 3.1.5.1 should
The
nonlinear
•
each reinforcement and both elastomer
The calculated the allowable
due
conditions.
to failure.
empirical
an accurate each elastomer
layers. It is recommended methods outlined in section
comparison
reinforcement
ANALYSIS
finite-elemen
panels to recommended
provides
and the buckling stress calculated stress for composite reinforcements
If a joint is to be used a number of times, the tensile stresses must be based on the fatigue reinforcement material.
3.1.5.3
that
:
at ultimate
lesser of the 0.2 percent compressive stress section 2.1.5.2. The allowable compressive
thickness
strength.
surface
be calculated
minimum
given in section 2.1.5.2 are recommended. to vectoring, allow for the reduction in joint
(sec.
determined
the
various
of nodes
and
stress distribution. It is of four layers across the of into
three layers across the a minimum of t 2 radial
nonlinear
and vectoring and 3.1.5.2. at the
grid
centroid
effects
and
that
the
should be compared with The applied stresses in this of each
panel.
3.1.6
Manufacture The
joint
joint
fabrication
and program
process
shall
be the
most
cost
effective
for
the
particular
needs.
An engineering study of fabrication fabrication processes that afford the costs. The engineering study should
processes should be accomplished best compromise between fabrication include detailed tradeoff evaluations
to select the schedule and of fabrication
methods;
reliability
status
past
program: fabrication, The
behavior
included
experience
research, tooling, of the
material
as a tradeoff
3.1.6.1
with
development, and facility
and
the
various
processes;
when
parameter
it is exposed
when
to various
alternative
fabrication
structural
materials
reinforcement
particular Metal
joint
reinforcements
fabrication
processes
limiting axial recommended recommended the material required
should
be
are evaluated.
are
either
compression for research
prior
reinforcements
shall
be
those
most
suitable
heat
treated
treatment
considered
thin
or thick,
requirement or small
the
difference
having
the
an influence
(sec. 2.1.4.1). Hydroformed development programs. Spun
programs. condition,
to final
should
be
to the required will cause
in the
for
assembly
on
the
Thin reinforcements are defined as reinforcements that can or spinning (sec. 2.1.6.1) and will be used in joints with a
for production in a normalized
properties
processes
reinforcements reinforcements
some of
are are
For both types, the forming should be made with and the material should be heat treated to the
machining. machined
from
plates
for
research
or small
programs. The plate should be normalized for rough machining and heat required properties prior to final machining. For production programs, thick should be stamped to the required shape with the material in the normalized
Heat
the and
needs.
possible method of fabrication. be fabricated by hydroforming
then
of
on schedules;
REINFORCEMENTS
The
Thick
of
or production; effect of the processing costs versus the joint configuration.
properties
prior
distortion
of the
a joint
by
spots and then assembling the reinforcements elastomer thickness will be circumferentially Although composite reinforcements have and molding, and molding with a mixture
to final
so that uniform.
the
treated to the reinforcements condition, and
machining.
reinforcements.
inspecting
development
This
reinforcements
all the
high
spots
distortion for high
should and
are aligned
be low
and the "
been fabricated by winding and molding, lay-up of chopped fiber and resin, it is recommended for
134
all production programs that composite reinforcements be fabricated by laying resin impregnated cloth cut into specific patterns into a matchedmetal mold and curing under pressure at a temperature and time suitable for the resin. However, in research or development programs, consideration should be given to compression molding with a compound of choppedfiber andresin.The sacrificial ablativeprotector (sec.2.1.3.4) should be fabricated asan integral part of the reinforcement.
3.1.6.2
JOINT
The joint The
joint
ADHESIVE adhesive
adhesive
SYSTEM
system
shall
system
not fail before
must
be
the elastomer
evaluated
prior
to
material. joint
fabrication
by
use
of
quadruple-lap shear specimens (sec. 2.1.7.1); an acceptable system must fail cohesively. The specimens must duplicate the thickness and cure condition of the elastomer and bond system in the joint. Fabricated joints should be bench tested at least to ultimate pressure and vectoring conditions to demonstrate the structural capability of the adhesive bond system. Failures
can
thickness,
the
occur
when
viscosity
the
bond
of the
sprayed on the reinforcements, these items should be included Each
lot of adhesive
and quadruple-lap variation.
3.1.6.3
FLEXIBLE
The joint
system shear
is either
and the
too
adhesive,
thick
the
or too
rate
materials to
should
ensure
be tested
quality
and
prior to
thin.
at which
and the time for spraying should in the joint fabrication specification.
tests
to use
maintain
To
these
control
the
materials
are
be monitored;
limits
in a joint
by peel
a record
of
on
tests
lot-to-lot
JOINT
fabrication
of the particular
system
primer
process
shall be consistent
with
the needs
and
characteristics
joint.
The molding process selected must depend primarily upon the number of elastomer layers, and the thickness of the elastomer rather than on the scope of the joint program. Joints with thin
dimensions of the joint, the layers and reinforcements elastomer layers (layers that
cannot be fabricated by injection molding) should order to improve the bond to the reinforcements.
by compression molding in molding has been successful
on joints up to 60 in. method is recommended programs. molding
Injection method.
be fabricated Compression
(1.52 m) in diameter with thick and thin reinforcements, and this for research and development programs as well as for production
molding Secondary
is a proven production bonding is a proven
135
technique process
and should be evaluated and should be evaluated
as a as a
molding method, particularly for large joints where significant cost savingshave been indicated. Prior
to
molding
process molding,
the
injection
on elastomer thickness the first development
This practice done by the Advantages
3.1.7
by
and joints
allows examination injection process, and disadvantages
or
compression porosity should
processes,
the
effect
should be evaluated be cut open to show
of
the
(sec. 2.1.6.3). After the joint cross section.
of the elastomer layer thicknesses, and if molding determination of the effectiveness of the elastomer of the joint
fabrication
processes
molding
are listed
in table
has been injection. VIII.
Testing
3.1.7.1
SUBSCALE
The
subscale
mechanical
TEST
PROGRAM
specimen
test
properties
The important mechanical failure, and the strength QLS specimens should in the joint. The bond QLS specimen Joints
should
have
been
used
program
shall
provide
values
for
the
elastomer
in design.
properties of the bond
for the elastomer are the shear between the elastomer and the
modulus, shear stress at reinforcement material.
be tested at the strain rate and over the temperature range expected between the elastomer and reinforcement should be cohesive, and the be used
to develop
designed
and
a satisfactory
tested
adhesive
successfully
and bonding
without
including
system. the
effects
superimposed compression and shear. However, if a joint is to be designed to operate pressure to take advantage of the reduction in spring torque due to pressure, the change shear modulus due to pressure must be measured. The reduced shear modulus is used predict spring torque 2.1.2.1.1). A method reference 78. If aging data are not be initiated as soon
and that
the has
of at in to
motor pressure at which the spring torque is unstable (sec. been used to measure the changed shear modulus is given in
available, a subscale test program to evaluate aging as possible in the motor program. This program
aging characteristics life and (2) several
of (1) several lots of the cured lots of the uncured elastomer
storage months
cured elastomer, the recommended test intervals are monthly up to six thereafter. For the uncured elastomer, the recommended test intervals
life. and
For the annually
are weekly
until
A subscale
test
and to establish
the shelf program acceptance
life has been should
be used
elastomer in order
characteristics must should evaluate the
to enable prediction to define uncured
of service elastomer
established. to evaluate
criteria.
136
lot-to-lot
variation
of elastomer
material
3.1.7.2
BENCH
Bench
TEST
tests
production the nozzle A joint establish The
of
]oint
characteristics
joints and shall verify clearance envelope.
bench axial
test
PROGRAM
that the
test program must be deflection characteristics,
for
compressive
axial
shall
establish
effective
acceptance
pivot
point
set up during the motor vectoring characteristics,
deflection
should
be
freely
about
to conducting measure the null
its effective
the vectoring actuator force
position.
The
pivot
point
while
tests, a pressure test and hence the offset
in a test
vectoring
tests
should
fixture
with
an
pressure and associated that allows the joint to
as it would
should torque
with
development program to and joint pressure sealing.
conducted
oriented
for
is compatible
unloading piston (fig. 21) so that the joint is subjected to the motor axial load. The vectoring test should be conducted in a test fixture rotate
criteria
be in the
motor.
Prior
be conducted in the same fixture to necessary to maintain the joint in a
be conducted
with
and
without
the
joint
ihermal
protection to determine the effect of the protection on actuation torque. In addition to axial deflection, vector angle, and actuator force, the hoop strain on the inner surface of each reinforcement should be measured. To ensure that only reliable joints are used in a motor, a stringent be conducted after The
same
criteria
tests
for
should
the
tensile-pressure leak the axial compression
should
be
joints.
If
be removed,
It is necessary should
that
be made
operating follows:
(l)
the
position
fails
target
light,
motor
acceptance used
effective
average
recommended
the
test
program
in the
should
as acceptance
elastomer,
the
elastomer
again. pivot
motor
production
this test
be determined
operating
procedure
to
pressure, find
the
for each
joint.
and maximum effective
pivot
A test
expected point
is as
target on a part of the test arrangement that is rigidly end ring and is near the theoretical pivot point. The
leg is to be aligned
coincident
with
the
center
line
of the
fixed
joint
ring.
Pressurize the
an
of the
pressure,
The
during
reinforcements
Mount a cross-hair-shaped connected to the movable end
(3)
a joint
the
pressure.
axial
(2)
conducted
and
at zero
test (sec. 2.1.7.2) is recommended; and vectoring tests.
nozzle and
Interpret
the
test
arrangement
vectoring open the
and
actuate
requirement.
the Camera photograph
shutter
the joint
Illuminate for one
as indicated
to an angle
the
cross-hair
complete
actuation
in the
sketch
in figure
at least
target
with
as large
as
a strobe
cycie. 46 to find
the
pivot
point. It is recommended between fixed and
that acceptable movable nozzle
limits on pivot-point components, rather
137
location be based than on clearances
on the tailored
clearances to fit the
Reference
line
+ Effective
pivot
point _ Axial point
pivot-
coordinate Reference
Figure 46. - Sketch
illustrating
determination
factors
of effective
138
involved pivot
in experimental
point.
line
measured pivot point. The clearance past with the purpose of providing radiation then should be established to be compatible The
recommended
set of layouts
design
practice
of the nozzle.
The
the radiation shield should be fixed in accordance protection, and the pivot-point acceptance limits with the required clearances.
to study movable
the effect
of pivot-point
components
are drawn
location on one
is to prepare
sheet
and
a
the fixed
components on another sheet. Superimpose the two sheets with an axial deflection appropriate to the pressure being considered, and successively pin the two sheets together at a series of pivot points. The limiting pivot point should be one that just permits the movable component
3.1.7.3
to rotate
to the
STATIC-FIRING
The
static-firing
requirements interact with Measurements misalignment coefficient develop
nozzle
program
shall demonstrate
and shall provide the nozzle. be
made
requirements, the nozzle,
a statistical
vector
angle.
PROGRAM
should of
required
that
the
data
needed
during
the
static
the joint
design
to design
firing
other
fulfills
the motor
components
program
to
that
determine
friction characteristics, natural frequency, and axial deflection, and vectoring capability. Sufficient
variation
should
be
obtained.
requirements. The final design of the guidance the results of the static firing tests.
control
Compare
measured
system
should
results
nozzle damping data to and
motor
be in accordance
with
The actuation power requirements should be established during the static firing. Certain increments to the actuation torque-friction and insulating-boot torque--cannot be calculated. With a bellows-type design (fig. 7(a)), the boot torque has been as much as 50 percent of the spring torque for joints up to 30 in. (76.2 cm) diameter (ref. 13). Therefore, when a bellows-type insulating boot is exposed to the motor environment, it is recommended that the actuator be capable of developing 50 percent more torque than the sum of the calculated increments to the actuation torque (sec. 2.1.2.1). When an exposed wrap-around insulating boot is used with joints up to 30 in. (76.2 cm) diameter, the actuator should be capable of developing 75 percent more torque than calculated. For an insulating boot protected by a radiation shield (fig. 7(a)), the insulating material usually is a soft silicone rubber (e.g., DC 1255), and for joints up to 30-in. (76.2 cm) diameter the recommended calculated.
3.1.7.4
actuator
DESTRUCTIVE
Destructive
testing
should
be
capable
of
developing
25
percent
TESTING shall demonstrate
join t failure
139
characteristics.
more
torque
than
The joint can fail in the mode can be demonstrated should
be mounted
angle
elastomer layers in an actuation
in an actuation
at various
pressures
up
or in the reinforcements bench test. The joint
bench
to
the
test
fixture
maximum
and
(sec. without
actuated
expected
2.1.5). Each failure the insulating boot
to the
operating
maximum
pressure
vector
MEOP.
At
pressures in excess of the MEOP, the vector angle should be increased in the ratio of the test pressure to the MEOP. Pressurization and vectoring should be increased at least up to the design ultimate pressure to demonstrate minimum compliance to motor requirements, and up to pressure producing joint failure usually identified by failure of the joint
3.1.7.5
AGING
The
joint
if the failure characteristics to maintain a pressure seal.
are required.
Failure
is
PROGRAM aging
program
shall
demonstrate
that joints
possess
acceptable
storage
life. Bench
tests
since
changes
should
be conducted
in joint
spring
on joints torque
that
have
been
formulation (sec. intervals and the
2.1.2.5.2). It is recommended spring torque measured. The
versus
time,
the
motor
specifications
and
3.1.8
Inspection
3.1.8.1
INSPECTION
The inspection initial ,material necessary
results
extrapolated
for the required
have
been noted
stored for
joints
service
using
environment,
a natural-rubber
that stored joints be vectored changes in spring torque should
to demonstrate
joint
in the
that
the
joint
at selected be plotted
will remain
within
life.
PLAN master plan procurement
to assure
shall incorporate through final
conformance
to design
inspection processes for use from joint acceptance to the extent
requirements.
Inspection processes should be used throughout the joint program beginning with material procurement and continuing through fabrication, process control, and final acceptance. Each phase :can use different inspection techniques with different acceptance or rejection standards. For this reason, an overall master plan for the use and management of the quality-control
program
the master plan and orientation master alertness planned
plan
should
of the
should
be established
prior
should be established on the basis of defects encountered, and the require
operators;
requirements
and
the
periodic
it should
evaluation
also provide
procedures.
140
to the
start
of fabrication.
The
scope
of
of the required reliability level, the type process sensitivity required. Also, the of the
for random
equipment checks
and on the
of the execution
skill
and
of the
Particular caution should be usedin planning the inspection requirements and in applying the inspection program so that material characteristicsand fabrication processesthat can affect the integrity of the inspection are identified. As an example, an inspection of elastomer thicknessthat is too infrequent could result in joints that weremarginalbecause of elastomerlayersthat varied in thickness.
3.1.8.2
INSPECTION
The
For the
For
PROCESSES
inspection
processes
reinforcements,
the
•
Spherical elastomer
•
Concentricity.
•
Thickness
•
Flatness.
•
Inner
the
shall
have
following
and outer
elastomer,
capability
minimum
radius at sufficient rings in a joint.
at various
the
inspection
positions
to
the
minimum
inspection
should
The
inspection
minimum deflection,
between
performance joints porosity
minimum
performance actuation, tests
should
be
inspected
the
dimensional end
attachment
rings,
inspections recommended and tensile-pressure seal
should taken
defects.
is recommended:
establish
expected
thicknesses
of
diameters.
su_faces,
concentricity
all critical
positions.
joint without adhesive on the reinforcement thicknesses and evaluate porosity visually.
recommended
of detecting
be
used
apart
to ensure
that
to verify
and
the
quality
cover then
for and
thickness
the
elastomer-to-reinforcement
141
joint
maintained.
is overall
flange-to-flange
envelopes.
porosity.
it. Measure
are the bench tests test (sec. 2.1.7.2).
clearance
is being
and
disassemble
At
Mold
a
elastomer
length,
parallelism.
the The
for compressive axial The data from the intervals, bond
production and
elastomer
3.2
LIQUID
INJECTION
3.2.1
System
3.2.1.1
SYSTEM
The
design
THRUST
VECTOR
CONTROL
Design
OPTIMIZATION of the
liquid
injection
system
shall be based
on a vehicle
optimization
study (including vehicle performance parameters, reliability, external constraints, and cost) that results in optimum vehicle performance. The recommended presented in chart
sequence of steps form in figure 47.
The design requirement based on a statistical allowance determined
for determining
because almost
optimum
should be defined as the maximum analysis of the operation of the vehicle
for the expected variation correctly at an early date
avoided, increases
the
envelope
LITVC
system
strongly side-thrust
affects impulse.
is
required vectoring capability on its various missions with
in the environments. This requirement and the use of inflated initial estimates
the vectoring requirement linearly with the required
design
the
design.
The
should should
system
be be
weight
The likely LITVC-system design options should be laid out without detail but should include basic design parameters such as type of injectant, injection pressure, source of pressurizing gas, number and spacing of orifices, injection location and angle, and tank type and
shape.
General
design
injector should
(including
motor
data,
candidate
injectant
specific
injection Initial
vehicle performance of these evaluations
configuration, design
amount
provide represent
the
of a system of data
tank should
for
LITVC
(e.g., should
range, payload, be used as the
shape,
and
be based
the pressurization on performance
systems
an empirical basis for design motor geometry and operating
final basis
is available
velocity), reliability, and for selecting the injectant,
data
(sec.
thrust
deflection
deflection angle
angle
be limited
cost. the
method. from
2.2.3.1)
previous and
programs.
should
be used
A to
analysis. The available data, however, will always conditions different from those of the motor for
which the new LITVC system is to be developed. Therefore, those data must or scaled to the geometry and operating conditions of the present motor section 3.2.3. The
impulses,
weight variation with flowrate, and tank weight variation with volume and pressure) be assembled. Each possible design choice must be evaluated in terms of its effect on
the desired The results
large
information
can be as much to 6 °, because
as l0 °, but the
142
efficiency
it is recommended as measured
by
be transformed as described in
that injectant
the
thrust specific
Define design requirements vectoring capability, motor meters, space envelope, constraints) .
Identify
the
(each option combination
LITVC
design
design
options
injectant, injector
loca-
available er'or i
ance data
data and to formulas
component and
weight curves
to
design
problem.
adapted
Determine
the
weight
and
capability option,
and
of each tion of
option on the rocket
Calculate
side-thrust
for each establish
the
(range, reliability,
payload,
for each optimum
option LITVC
Figure 47. - Recommended
and
will include one of design parameters
including type of injection pressure, tion, etc.).
i
(required para-
LITVC the
the configuramotor.
vehicle or
design effects
performance
final cost to system
as
velocity), required
determine design.
sequence of steps for determining
143
the
the optimum
LITVC
system design.
=.
impulse (refs.
drops 46,
3.2.1.2
to low
108,
and
The
The
shall
consistent
injectant
flowrates
required
for larger
deflections
deliver
maximum
with
material
side
specific
impulse
compatibilities,
and
storage
have
the
highest
requirements,
and
toxicity.
IX summarizes selection
high
OF INJECTANT
in]ectant
allowable
at the
122).
SELECTION
density
Table
values
_
the
of the
relevant
injectant
data
must
on the
consider
major the
operational
efficiency
injectants.
of the
injectant
in delivering
side
specific impulse. The relative efficiency of a candidate injectant may be known from existing data (secs. 2.2.1.2 and 2.2.3.1); if not, it should be checked by small-scale tests. Data on the relative efficiencies of various injectants are given in references 109, 121, and 141; figure 48 presents Isp(s) values for a number of inert and reactive liquids. The relative efficiency of a new injectant should be estimated from chemical-equilibrium calculations; various approaches and typical results are described in references 144, 145, and 146. Judgement make no injectants. injectant. and that
must be allowance
used in interpreting for the variation
the results in evaporation
of equilibrium calculations, rate and reaction time
Excessive time delay in energy release reduces the potential It is recommended that calculations be used only to screen the final evaluation be made by test firing.
since they of different
effectiveness of an injectant candidates
The injectant should be selected for highest density, so that the fluid tanks, valves, and tubing can be made as small as possible to save both space and system weight. A preliminary estimate should be made of the volume required for the liquid injectant, and the storage tank that will contain this volume should be designed and fitted around the nozzle so that the envelope
constraint
can be evaluated.
The liquid selected must long-term storage when kept of the Vehicle. As examples perchlorate in water boils at 70 ° F (294 should
not
propellants
crystalizes at temperatures K) at a pressure of one
be important
The compatibility neighboring systems on
places. If positive injectant cannot
not chemically decompose, evaporate, or crystalize during within the temperature and pressure limits specified for storage of typical limiting conditions, a 62% solution of strontium
with
of the should
contact.
sealed
systems
under
candidate injectants be checked, because
Danger
to
personnel
approaching atmosphere
32 ° F (273 K), and hydrazine (ref. 115). The latter limitation
pressure. with certain
may
be
the motor, propellant, reactive injectants ignite important,
especially
and other some solid in
safeguards against inadvertent spillage of an effective but highly be provided, then the injectant will have to be eliminated
144
confined reactive from
The for
Isp(s ) listed the following ,250;
emj=
is for typical booster stages (Pc _ 800 conditions: single orifice injection;'Pin
2.5;
Fs/F a
= 0.02
psia, j =
e _12) 1800 psia;
.
320 --
UDMH
+
N2H 4 (EXOTHERMIC
DECOMPOSITION)
Decomposition _.._under /These /difficul_
280
--
MHF-3
occurs
only
certain conditions. I s- values are to achieve.
(EXOTHERMIC
DECOMPOSITION)
240 NITROGEN
TETROXIDE
--
200
HYDROGEN
STRONT LEAD
PEROXIDE
IUM
PERCHLORATE
PERCHLORATE
+
+
METHANOL
WATER
MHF-3
1--
FREON 12, BROMINE
120-FREON
I14-B2
(INERT)
--l---
UDMH
+
FREON
113
(INERT)
N2H 4
N ITROMETHANE UDMH
--
FREON 114-12 (INERT) P E RCHLOROETHYLENE
l80--
BENZENE
I-
ISOPROPYL IRFNA ZINC WATER
40
ALCOHOL
(ENDOTHERMIC BROMIDE OR
DECOMPOSITION) IODIDE (INERT)
(INERT)
I
Isp(s
Injectants performance
Figure
48.
for is
- Values (data
which well
of from
),
lbf-sec/lbm
Injectants
TVC
performance
defined
side refs.
specific 121,125,
impulse and
145
for 129).
reactive
for is
and
which
TVC
not
well
inert
liquid
defined
injectants
consideration. For example, a toxic fluid such as nitrogen tetroxide or bromine shouldnot be selectedunless it is practical to provide protection to personnel and the environment during loading, checkout, ground testing, launch, and possibleother releasedue to mishap. The liquid must be compatible with every tank or bladder material with which it comesin contact. The tank or bladder materials must neither react with the liquid nor catalyzethe liquid's decomposition. The materials should resist decompositionby the liquid and remain impermeable,becauseliquid that has permeateda material is not available for injection. Resultsof investigationsof the permeability of variousbladdermaterialsgiven in references 115 through 118 should be consulted.
3.2.1.3
INJECTION
The
PRESSURES
injection
the orifices
pressure, shall
the
For
greatest
control orifice being tests.
orifice
maximize
The most efficient pattern circumferential line on the efficiency,
AND
INJECTION size,
the side
for injection nozzle wall
these
orifices
and
thrust
circumference
be estimated
number,
should
for minimum optimization
injector weight
and
of
have
omniaxis
control
orifices located in a 121, 124, and 125). rather
than
pitch-yaw
overlap losses should be 7 to 14 times the be studied and transformed to the system
If this is not possible, the spacing effect should be evaluated that cosine losses due to spreading the orifices around by vector
addition
system weight should be compared with pressures, and the overall optimum pressure three-orifice
and grouping
is obtained from many circular (figs. 29 and 31 and refs. 109,
of the
estimated
The injection pressure should be about twice the rocket side-thrust specific impulse (figs. 38 and 40 and refs.
The
spacing,
efficiency.
(ref. 142). Minimum spacing to avoid diameter, but the available data should designed (sec. 3.3.3.1). It is recommended
the
ORIFICES
since
simple
but
plumbing,
it provides this
effects.
chamber pressure to achieve highest 108 and 121). However, hardware
loss in side-thrust should be used.
is recommended,
side-force
in the
efficiency
excellent
effectiveness
must
for
lower
side-thrust
injection
efficiency
be confirmed
by an
study.
The simplest LITVC injector arrangement has four injectors 90 ° apart. However, thrust deflection may be required in any plane, not just the pitch and yaw planes. In this event, the side force is the vector sum of the forces produced by the two injectors. Two such injectors operating single
simultaneously
injector
As noted flowrate
to produce
will use injector the
previously, injection or side-force level,
same
liquid
at a rate
approximately
_/_'times
that
of a
side thrust.
is more efficient the number of
146
at low flowrates per injectors is increased,
orifice. then
If, for a given the side-thrust
efficiency is increased.The efficiency of a number of injectors usedto produce a singleside force is estimated by vector addition of their side-force contributions. Each injector is considered to produce a side force at its location independent of the adjacentinjectors. Therefore,the efficiency of multiple-injector LITVC can be estimatedfrom the equation
Cosineefficiency =
(12) n inj
where llin j =
I_/i
=
number
of injectors
angle between injector
operating
total
side force
and
the
side force
produced
Equation (12) does not include the efficiency increase due to reduced or efficiency decrease due to overlapping of adjacent mixing and shock
3.2.1.4
INJECTOR
The injector
LOCATION location
AND
DISCHARGE
and discharge
angle
side-thrust
For highest side-thrust efficiency, locate the injection orifices nozzle as is possible without incurring significant corss-nozzle vector deflection. (Cross-nozzle effects are pressure increases
(1)
Use the empirical
ratios
for X/L
listed
(refs.
X/L
Nozzle Small thrust deflection (about I °)
17.5°
0.3
0.4
27.5 °
0.2
0.3
Large thrust deflection (about 6° )
X = distance (along nozzle axis) from throat to point of injection
147
efficiency.
over.) One or more of location of the injector
108 and
divergence half-angle
L = distance from throat to nozzle exit plane
per injector
as far upstream in the rocket effects at maximum thrust on the wall of the opposite
that cross the optimum
below
Optimum
flowrate areas.
i TM
ANGLE
shall maximize
side of the nozzle caused by shocks and injectant following three methods should be used to estimate the nozzle exit-cone wall:
by the
125)"
the on
(2)
Estimate
the
Generate such that
a straight the line
curves
optimum
Use the
methods
shock
and
injector
location
by
use
of
empirical
curves
49. The
injection
point
at which
site (refs.
of fluid
mechanics
injectant-mixture
the line reaches
107 and
only
49).
and gas dynamics
disturbance
the
nozzle
for inert
wall is the
147).
in the
to estimate
nozzle
from
the path various
injection points; however, check the method selected against known before it is applied to the design problem. One such method utilizes computer program (ref. 151); however, in its present form the formulated
(fig.
line from the nozzle rim opposite the proposed injection point crosses the nozzle centerline at the angle X obtained from the
for _ in figure
probable
(3)
optimum
of the possible
test results the Boeing program is
injectants.
The optimum discharge angle (figs. 23 and 37) results in the greatest collision effect and mixing of the motor gas and injectant. From various studies (refs. 107, 108, and 125), the discharge angle should be 25 ° . However, as the discharge angle influences the location of the injectors and the discharge evaluated
3.2.1.5
their plumbing, envelope angle. For systems that
be a factor in the selection the discharge angle should
of be
by test.
AMOUNT
The
considerations should must be an optimum,
OF LIQUID
amount
maximum
of vehicle
liquid flight
INJECTANT
in]ectant duty
shall
REQUIRED be the
minimum
amount
necessary
for
the
cycle.
The weight of liquid injectant required must be calculated from the maximum required vectoring capability of the motor, the injectors and their location having been selected as described in section 3.2.1.4. The vectoring requirements will be given explicitly as thrust deflection The
angle
following
(1)
0 for
procedure
pitch
and yaw
is recommended
and
required
side thrust
for calculating
Fs, each
the weight
as a function
of injectant
of time.
required:
For each candidate liquid injectant, determine the side specific impulse Isp (s) as a function of deflection angle, and plot the results. Examples of such plots are given in figure
42.
(2)
Noting the motor vectoring requirements time t, use the results of item (1) to obtain function of time.
of deflectionang!e 0 as a function the estimated side specific impulse
of as a
(3)
Noting the motor side force requirements injectant weight flowrate _¢_ as a function
F_ as a function of time.
the
:
148
of time,
calculate
60 ° I
=25 °
50 ° __.__.__.----I
_
v
4oO
,[
0 ¢0 0 0
30 ° --
t4 0 4-I
qJ p-4
20 °
10 c __
O,
0°
i°
2°
Largest
Notes:
'
'
The rim
required
3°
deflection
diagonal from the injection is not the location of the
4°
5°
angle
0ma x
port shock
to the nozzle wave (cf. fig':23).
Figure is based on data from conical and contoured nozzies having e= 7 to 20, _ =18 to 28°,and _ both inert and reactive injectants.
Figure 49. - Relation
of thrust
deflection
angle to injector location
149
(refs. 107 and 147).
6°
Integrate estimate
(4)
the injectant the amount
determine
the
achieve The
(5)
The
the
of injectant
gas flow
of
of the
for the injector and transformed
the
injectant
liquid
side impulse
into
the tank warm-gas
cold
gas under
required
success.
for vectoring,
including
that
and valve vectoring.
for tank
ullage,
leakage, must be For preliminary
should
be carefully
estimated
for the motor
being
tank
within
of liquid
shall
expel
the liquid
the specified should
generator,
high
GAS REQUIRED
or
pressure
be from the
at a rate
response
gas
is the
a tank can
be
source
that will produce
time. of compressed contained
of the
inert with
gas used
gas or from
the
liquid
pressure be sufficient
The ......... of regulator so that
tank
may
a
in
to pressurize
gas should have a volume at LITVC operating pressure equal to the total volume, the volume of the piping and the manifold, and volume of liquid
in the
to
purposes.
OF PRESSURIZATION into
angles
to to
configuration and location selected by use of available test for application to the current design problem (sec. 3.2.3).
expelled. Because the specified injection point and be sustained acceleration and flow friction injectant should
available
10% for these
impulse
solid-propellant common tank.
injectant
not
of flight
deflection
add
gas flow
liquid, the own stored
probability
for the various
estimates,
AMOUNT
If a tank
of side impulse
ignition to the end of firing or use statistical methods
piping and valves, and for valve operation and added to the amount needed for
the required The
_Vs from motor injectant required,
for filling calculated
designed and, data, correlated
The
amount
specified
amount
side specific
3.2.1.6
flowrate of liquid
a
the of its to be
injectant pressure must be delivered to the fluid at the during sudden demands for large flows, the effects of liquid should be evaluated. The pressure applied to the liquid
have,
to
be
significantly
higher
at the injector valve. The piping sizes, to respond to the worst conditions.
the
than
the
gas supply
minimum
required
rate,
pressure
and
the gas delivered to the liquid tank should be reduced by a pressure liquid is not injeCted at pressures excessively above the pressure level set by
the design. The real
weight of gas so required should be calculated from one of the equations of state of a gas, such as the Beattie-Bridgeman equation or the equation of state with
compressibility factor contained in reference error
(ref. 152). An example of such 153. An estimate of the weight
< 10%, can be obtained
from
the ideal-gas
150
equation
a calculation for a LITVC system of the gas required, usually with of state:
is an
CPM p
-
(13)
RT
where p = density,
lbm/ft
P = pressure, M = molecular R
= universal
T = absolute
generator
3)
psia (N/m 2) weight
of the gas, Ibm/ibm-mole
gas constant,
1545.3
temperature,
C = conversion
If a warm-gas
3 (kg/m
lbf-ft/lbm-mole-°R
(8314.3
J/kg-mole-K)
°R (K)
factor,
is used
(kg/kg-mole)
144 in. 2/ft2
in place
of cold
(1 J/N-m)
compressed
inert
gas, a larger
total
quantity
of gas will be required than that calculated above. This condition arises because the supply of gas must be maintained at the maximum expected demand level through all periods of firing time, even though the actual demand for pressurization gas usually will be much lower than the maximum. The propellant grain in the warm-gas generator must be designed to produce vectoring overboard
sufficient
pressurizing
requirements (ref. through a pressure
gas
to
cause
154). The gas that relief valve.
the
injectant
is produced,
to but
not
If a common liquid/gas tank with no separation between the allowance should be made for the dissolving of part of the evaporation for example, N204
the real
of some in the
vapor methods and
not
with
used,
should
ideal
properties
of dissolving and evaporating of mixtures (ref. 152). Care of the
gases
in order
to avoid
the
motor
be released
liquid and the gas is used, gas in the liquid and for
of the liquid into the gas. The latter phenomenon Titan III system at 70 ° F (294 K), the pressurizing
(ref. 47). These effects of the thermodynamics the
comply
usually is negligible; N2 contains 1.5%
should be calculated by should be taken to use the substantial
errors
at high
pressures.
3.2.2
Component
The
size
represent
Design
of LITVC
components
the LITVC
system
shall
be based
to be designed.
151
on
verified
empirical
curves
that
The empirical curvesmust provide adequatedata of sufficient accuracyfor selectionof type of injectant fluid, injector location, number of orifices, injection angle, and injection pressure.Any additional data required must be generatedfrom subscaletests (sec.3.2.3.2). These curves must be based on test data, becauseavailable analytical methods do not reliably predict LITVC performance. Data for these curvesshould be obtained from earlier developmentprograms and subscale tests.These data should be plotted and correlated, then transformed for usein the current design(sec.3.2.3.1). After the first complete set of LITVC components has been designed, it should be fabricated, assembled,and evaluated in a full-scale test (sec. 3.2.3.3) at the earliest opportunity to confirm the design and to verify performancedata for usein further design improvementor performanceprediction.
3.2.2.1
INJECTORS
Injectors
shall
velocity
within
deliver
injectant
the required
The injector valves should flowrate as determined by satisfactory
accuracy
to the
response
be sized methods
for design.
The
exhaust time.
flow
in columnar
jets
at maximum
•
no larger described
than necessary for the in sections 3.2.1.3 and
injectors
must
contain
flow
maximum required 3.2.1.4; use data of
passages
and
orifices
that
are specially contoured and streamlined to accelerate the fluid to the maximum possible velocity on discharge. The pintles or gates must likewise be contoured and streamlined to achieve maximum acceleration of the fluid, so that on discharge the fluid is travelling at the highest
obtainable
pressure
The use of variable-flowrate side-thrust Off-on
center-pintle capability
injectors
vectoring (ref.
that
as little
to injection
as possible.
be
control
preferred
in
with
different
of actuating response,
the
from the inert
the natural
shock
cases
injector weight
frequencies
valves
must
penalty,
cost
76).
152
way,
or electro-mechanical these injectors can
minimal
certain
In this
the
system
momentum.
type injectors with servo is recommended, because
and versatile may
diverge
converted
because
These injectors should be of the center-pintle when fully open. To avoid vibration problems,
be set in a range method
in jets
efficiently
efficiency
simplicity. momentum
The
speed
will be most
of
their
of the structures
constraints,
for high
weight
and
loading.
type designed their operating
be determined
control provide
from and
low
for maximum flow frequency should of the vehicle.
the required
flight
control
speed limitations
of
Screensshould be installed in the liquid supply entranceto eachinjector valveto catchand hold any debris that might causetrouble in the injector valve. Measuresfor the control of contamination of fluid, components, and system may suffice in lieu of active screensor filters.
3.2.2,2
STORAGE
The
liquid
TANK in]ectant
during vehicle operation.
AND tank
storage
BLADDER shall
preserve
and provide
positive
The shape of the tank should of injectant to be carried
be selected should be
recommended
that,
amount
spherical
be used,
tanks
if
the
because
the
the
liquid
without
expulsion
of the
degradation liquid
to result in minimum weight. determined as described in
of
liquid
sphere
required
is the
most
shape;
during
motor
The required amount section 3.2.1.5. It is
is relatively efficient
or loss
small, but,
one
or
if a large
more
amount
of liquid must be carried, the tank should be toroidal, since this is the shape with the largest volume that fits around a nozzle. In intermediate cases, cylindrical tanks are suitable. The tank should be designed according to the recommended practices of reference 155, fabricated from a lightweight or high-strength alloy such as aluminum or stainless steel, and be compatible with the liquid. If the tank is to be left pressurized during storage or standby conditions when personnel may be near, the tank must be designed to meet the prevailing pressure-vessel safety code. To avoid this requirement so that a low factor of safety can be used, provision should be made to pressurize the tank when the vehicle is prepared for launch and after personnel have been cleared from the vicinity. If
a cool
depended be allowed
inert
gas
is used
for
pressurizing
upon to keep the liquid puddled to contact the liquid directly.
A bladder to separate the gas from warm gas, because the gas loses replenished
by
more
warm
gas.
if gravity the
outlet,
or
acceleration
reactive
injectants
forces
it is recommended
the liquid is recommended if the liquid heat to the liquid rapidly, contracts,
With
provide a positive seal because contact combustion or explosion in the tank. and plastic.
and over
and
warm
gas,
that
can be the gas
is pressurized and must the
bladder
by be must
between liquid and gas could result in failure through The bladder should be fabricated from laminated fiber
Special means should be provided to completely seal the injectant liquid in the tank. The filling and trapped-gas vent fittings should be designed with provision for positive closure (e.g., crimped or soldered metal closures). The tank outlet should be sealed with a metal diaphragm 156).
scored
to break
open
without
loose
153
fragments
when
the liquid
is pressurized
(ref.
3.2.2.3
PRESSURIZATION
The
SYSTEM
pressurization
injectant
When the LITVC in time for the high-pressure
within
shall, the
study The
system
the
pressure
prescribed range
time,
the injectant must be brought signal. The pressurization a warm-gas
given
tank
in section
system
pressurize
for injection
generator.
The
into
the
the nozzle.
up to operating system can be
choice
that considers pressurization system performance capacity of the pressurized-gas storage volume
to practices
If a high-pressure
or
within
design
system is activated, first vector-control
inert-gas
optimization performance. according
system
to a level
should
pressure either a
be based
and weight should be
on an
and LITVC determined
3.2.1.6.
is used,
the
tank
outlet
should
be sealed
by a squib
valve that
is opened by an electric signal or system activation. The gas flow from the high-pressure tank should be stepped down to the design injectant pressure level by a pressure-control valve. If there is any possibility that harmful debris might come from the tank, valve, or line, screens should be installed ahead of the controller. An inert gas such as nitrogen should be used weight unusual If
a
in a high-pressure
tank
system
to minimize
corrosion
is important, helium should be used, but special ability of helium to diffuse through materials (ref. common
liquid/gas
tank
optij..n_m for the system. liquid is used should be deflection.
is to
be
used,
the
range
and
compatibility
attention 118).
should
of pressures
and be
be given
provided
Also, the minimum pressure remaining when sufficient for effective injector-valve operation
Warm-gas generator systems usually employ solid propellants solid rocket motors. The warm-gas generator should
problems.
to the
should
almost all and thrust
If
be
of the vector
are designed like miniature designed to deliver the
gas-flowrate/time profile that is calculated as described in section 3.2.1.6 and reference 157. The propellant grain shape should be adjusted to cause the flowrate to vary to fit the desired curve (ref. 154). Usually a high rate is needed initially to provide for launch or staging pertubrations;
this
condition
is followed
when only vector trim and course generator should be a clean-burning 1922 K)) propellant alloy-steel tubing and will be usable only if safe levels. Otherwise The gas pressure
by a period
of low demand
corrections are needed. low-flame-temperature
during
the
rest
of flight
The propellant for the warm-gas (2000 ° F to 3000 ° F (1367 K to
that does not produce deposits and that is not too hot to use with valves. Propellants that burn at temperatures above 2500 ° F (1644 K) the operating period is short enough to limit heating of steel parts to insulation or high-temperature metals will have to be used.
flow from the generator should regulator designed to step down
pass through the pressure
(ref. 156). Since the production of gas by the generator of actual gas demand, the surplus gas must be diverted
154
a screen to catch debris and into a to the design injection pressure level is predetermined and independent through a pressure relief valve for
disposalto the environment. If possible,this unneededgasshould be releasedfrom a small nozzle pointed aft, so that a small increment of thrust canbe recoveredthrough its release. However, if the vehicle has a coast period and if the gasgenerator bums after the rocket motor has burned out, the small exhaust jet could cause unwanted changesin vehicle attitude. This condition should be preventedby exhaustingthe unneededgasthrough two equal orifices that areoriented in opposite directions. If the main vehicle system requiresa supply of gasfor roll control, the possibility of using the samegasgeneratorfor this purposeand for LITVC pressurizationshould be considered.
3.2.2.4
LIQUID
Flow
from
vehicle
If there prevent
STORAGE
and
inertial
is more offsetting
EQUALIZATION
sloshing
in multiple
tanks
and
large
lateral
than one tank, provision must the vehicle center of gravity.
be made Uniform
to drain expulsion
tank is dependent on the ability of the bladder to deflect circumference of the toroid during expulsion. The bladder so that one sector freely movement could generate
3.2.2.5
DISPOSAL
collapses on the liquid undesirable sloshing,
OF SURPLUS
injectant
flow
shall not
change
rate
should
the tanks at equal rates to of liquid from a toroidal
and fold uniformly around the should not be allowed to buckle
while other the sloshing
sectors should
are restrained. be inhibited
If vehicle by baffles.
INJECTANT
Injection system destgn shall provide flight weight and to obtain additional
The
tanks
properties.
for disposal thrust.
be measured
and
of surplus
integrated
over
injectant
time,
so that
to reduce
at any instant
of flight time the total amount of liquid actually used will be known. A computer or control device should continuously compare the amount of liquid used with the maximum that could
be
control nozzle The
used
up to that
time
without
jeopardizing
the
completion
of the
mission.
should then signal the injectors to expend the excess liquid equally around so that the motor thrust will be augmented but there will be no thrust deflection.
axial
thrust
added
by jettisoning
the surplus
expression:
155
liquid
can be estimated
with
Flight the
the following
aFa =
lsp(s ) (o = o*) Ws tan
a
(14)
inj
where /kF a
lsp(s)
(o
= axial
thrust
= specific
= o°j
impulse
deflection, lb f-sec/lbm = flowrate Odlnj
This
equation
added
by surplus
injectant,
of the liquid
estimated (N-sec/kg) of liquid
from
injectant,
lbf (N)
injectant a plot
in the side direction
of Isp (s)versus
lbm/sec
0 (e.g.,
at 0 ° figs. 35 and 42),
(kg/sec)
= the equivalent half angle of the nozzle from the injection point to the exit, determined as the angle between the nozzle centerline and a line from the injection point to the exit rim, deg
is applicable
to both
extrapolated to 0 ° deflection augment axial thrust. These
angle effects
conical
and
contoured
nozzles
(ref.
126).
The
Isp(s
)
is used because it best represents the LITVC effects that are the increased pressures on the exit cone caused by
injectant energy and mass and by injection shocks. I_p (s) values obtained at larger deflection angles should not be used in equation (14) because these Isp (_) values have been reduced by losses in measured side forces due to the circumferential spreading of the side forces around the nozzle. Such losses detract from side thrust but not from axial thrust. Correlation the data in reference 121 shows an accuracy within -+ 10% for nozzles with expansion
with ratios
up to 10. Equation (14) may underestimate the added thrust when applied to long contoured nozzles having expansion ratios greater than 20 with injection far upstream from the exit. This result occurs because the wall angle at the center of this region of added pressure usually is significantly pressure nozzles,
larger
than
the
equivalent
half-angle
OLin j.
The
center
of the
region
of added
generally is located a short distance downstream of the injection orifices. then, the value for the half-angle used in equation (14) will be less than
For such the local
wall angle at the injection point but greater than _inj as defined above; this effective half-angle is estimated from experience. The added thrust due to expending injectant in the nozzle is more accurately estimated by the use of data from subscale tests or, if an adequate mathematical model exists (sec. 2.2.3), by integrating the product of the added pressure and the tangent A detailed
of the
wall angle
performance
over
analysis
the
nozzle
wall
of a liquid-injectant
47.
156
area
affected. dump
system
is presented
in reference
3.2.2.6
ADAPTATION
The
motor
for system
OF THE
design
shall
MOTOR
provide
FOR
injector
LITVC
mounts
and ports
and
external
brackets
support.
The nozzle design should make provision for holes and mounts for the injectors. The metal orifice ends of the injectors should be recessed sufficiently inside the injection port (fig. 29) that they will not be damaged by heat flux. The heat flux at the inside end of the injection port should be estimated (refs. 134 and 135). The port hole should be made conical to fit the shape of the liquid jet and only large enough to permit the jet to be discharged without momentum losses due to wall friction. Small port hole size will minimize heat transfer into the
hole
and
the
exhaust-gas
Provide liner.
will minimize
erosion
at the
hole
edges
that
results
from
impingement
of
flow.
a gas-tight
The injector wail should
the
seal such
as an O-ring
mount, to which the have sufficient strength
at the interface
between
the
injector
and
the nozzle
injector will be bolted, and its attachment to the nozzle to withstand the full injector reaction thrust in addition
to other loads. If possible, the entire LITVC system should be mounted on the nozzle avoid any problems of differential motion between the nozzle and the motor aft dome skirt. If this mounting is not possible, provide flexible lines or expansion joints.
Mechanical and thermal analyses made of the nozzle and related LITVC
system
the major part these vectoring
The
only
that
occurs
and
to the
(i.e., stress, gas flow, heat transfer, and erosion) should be portions of the motor. Loads due to the weight of the
intermittent
TVC
Pressures
on the
of the vectoring force must be included in these pressures on the exit-cone wall can be estimated
thermal
problem
around
and
of consequence immediately
to or
due
downstream
to LITVC of the
exit
cone
walls
analyses. The (ref. 136).
is the
severe
injection
port
that
heating holes
produce
distribution
of
and erosion (fig.
34).
The
amount of erosion depends on the exhaust flow properties, the reactivity of the injectant, and the type of ablative material used. To predict this erosion, use methods for predicting erosion that include the capability for treating the effects of chemically reactive injectant and exhaust-gas mixtures (refs. 158 and 159). The analysis should be cross checked by scaling known LITVC hole erosion to the relationships being used as the scaling factors. typical
heating
and erosion
patterns
is shown
design condition, appropriate heat-transfer A design of an injector mounting pad with in figure
157
50.
Injector surface
Eroded
mounting-pad
surface
V/I/I//lllA
7075
aluminum
alloy
silica/phenolic Graphite
cloth/phenolic
Figure 50. - Typical LITVC port configuration showing erosion and char patterns.
3.2.3
Performance
Test
data
shall
operational Test
data
from
be
demonstrated
3.2.3.1
support
the
and Testing
LITVC
system
development
and
demonstrate
capability. other
being designed determine the should simulate
Evaluation
LITVC
should general
systems
be used configuration
transformed
for
supported by data from actual motor conditions. at test
conditions
PERFORMANCE
Performance to the LITVC
data
from
system
other
FOR
actual
correlated
by analysis
to the LITVC
design and motor tradeoff system. As soon as possible,
subscale tests The full-scale
simulating
DATA
and
conceptual of the motor
conducted under motor operating
flight
studies to these data
test conditions that capability must be
conditions.
DESIGN
LITVC
programs
required..
158
shall
be demonstrably
applicable
Existing LITVC data that canbe transformedto the required LITVC systemshouldbe used for motor optimization studies,tradeoff studies,and preliminary conceptual design.These studiesmust be conducted early in the program to determinethe adequacyof the data and to define neededadditional data so that a test programcan be commenced. The data obtained from various sourcesmust representthe variation of side-force specific impulse with injectant flowrate, injector location, injection angle,injection pressure,orifice size, and orifice spacing.The available test data should be transformed to dimensionless form except for the side-force specific impulse, which is retained in units of lbf-sec/lbm (N-sec/kg). Each of the designvariablesshould be presentedas a family of curves,wherein all other parameters are constant at one or more arbitrary configurations. These configurations should be selectedto representarange that includesthe optimum design.An example of this practice is shown in figure42 for an evaluationof injection pressure.Other plotting formats as illustrated in figures 36 through 40 should be used if they are more convenient. Data that have originated from rocket motors that were significantly different from the designmotor should be transformed; use the dominant physical lawsasdescribed in section2.2.3.1 to make them applicable. The suitability of the transformed data to the design motor must be evaluated for consistencyand agreementby using data from different sourcesplotted on the samegraph. If the results form a continuous plot with little scatter, the results can be usedwith confidence. If the scatter is larger than can be tolerated within designspecifications,a test program must be initiated to generatedata in the expecteddesignrange.Awaiting test data could result in a delay in a program, and in such a period the transformeddata will be the only availabledata. Thesedata must be usedfor initial optimization studiesandpreliminary design;useengineeringjudgement to allow for an amount of error defined by data scatter. The results obtained with such data must be reevaluatedwhen test data in the expected designrangebecomeavailable.
3.2.3.2
SMALL-SCALE
Small-scale provide Small-scale transformation injection the test
tests
design tests
TESTS using
data not
should of other
system
parameters
otherwise
available.
be conducted test data. The
in
to obtain test motors
the
expected
data should
design
that are use rocket
range
shall
not available nozzles and
from LITVC
geometries that are scale models of the expected full-scale design configuration; motor chamber pressure should be the same as that of the design motor; and the
test propellant exhaust gas should be similar to that of the full size motor in temperature and in oxidizing species that are free to react. To obtain valid data, the test motor need not be a solid-propellant motor but can be a liquid propellant motor, a change that usually results
in cost savings
and
test
convenience
(ref.
159
121).
3.2.3.3
FULL-SCALE
A full-scale An
firing
evaluation
of the
DEVELOPMENT
TESTS
test shall evaluate
the LITVC
full-scale
LITVC
system
system
should
design.
be conducted
on
the
first
static
test
firing of the motor, so that design changes can be incorporated without causing significant program delays or increased costs. Measurements must be made of all parameters affecting design of the LITVC system and the results used to reevaluate the injector valves, injectant requirements, and injectant tank size. If the motor is to operate at high altitude, the test should be conducted at the corresponding ambient pressure. The final LITVC design must be evaluated in static test firings, so that its actual performance and characteristics can be known
for flight-control
may be necessary
3.2.3.4
use. Vertical
OPERATING-CAPABILITY
Procedures operation
orientation
of the motor
or at least
of the liquid
tanks
for such-tests.
for
the
TESTS
component
of the LITVC
system
testing,
assembly
shall be developed
installation, and
checkout
and
documented.
The functional capability of all components of the LITVC system should be determined by test before assembly. These tests should employ pressurized gas and liquid supplies and control connections as necessary to simulate operating conditions. The bench testing should be performed with an inert liquid (e.g., Freon) clean. If a reactive or nonevaporating injectant thoroughly
cleaned
after
testing.
After the system has been should be checked during satisfactory documented. The
other
that will evaporate and leave the components is used in bench testing, components must be
operating The critical
assembled and installed on the motor, storage or launch readiness as often
capability. components
components
including
Procedures for these are the gas pressurization the
meters,
check
piping, and fittings are important but they are not procedures for correct installation, filling, operation, the rocket motor should be documented. If a gas generator is used, and resistance. If a tank pressure checked The
more
monitored
gage, should for continuity sensitive
be monitored, and resistance.
electric
by feedback
the igniter squib should of inert gas under high
portions
and
of the
the
squib
injectors
signals.
160
valves,
the critical components as necessary to ensure
check operations subsystem and injectant
should be the injectors.
tank
and
bladder,
nearly as sensitive to malfunction. Also, and unloading of the LITVC system on
be checked at low voltage for continuity pressure is used, its pressure, sensed by valve
should
at its outlet
be actuated
should
be electrically
and their
movements
APPENDIX Conversion
Physical
quantity
of U. S. Customary
U.S. customary
Angle
degree
Density
lbm/ft
Force
lbf
unit
3
A Units
to Si Units
SI unit
Conversion
radian
1.745x10
kg/m 3
16.02
N
4.448
factor a
-2
t
in.
cm
2.54
ft
m
0.3048
lbm
kg
0.4536
Ibm/Ibm-mole
kg/kg-mole
1.00
Peel strength
lbf/in.
N/cm
1.75
Pressure
atm
N/m 2
1.O13x10
psi
N/m 2
6,895x103
psi
N/cm 2
0.6895
lbf-sec/lbm
N-sec/kg
9.80665
Stress
psi
N/m 2
6.895x103
Temperature
oF
K
oR
K
K= 5(°R)
oF
K
K= 9"_--(°F )
oR
K
K = 95---(°R)
in.-lbf
m-N
0.1 130
Length
Mass
Molecular
Specific
weight
impulse
Temperature
Torque
difference
s
K:-_9(°F
+ 459.67)
aMultiply value given in U. S. customary unit by conversion factor to obtain equivalet_t value in SI unit. For a complete listing of conversion factors, see Mechtly, E. A.: The International System of Units. Physical Constants and Conversion Factors. Second Revision, NASA SP-7012, 1973.
162
APPENDIX
B
GLOSSARY*
Definition
Symbol A
Appears
reinforcement material constant value of elastomer shear modulus superimposed
eq. (3)
pressure
C
conversion
d
distance from point of liquid nozzle exit, in. (cm)
do
diameter
of the discharge
injector,
in.,(cm)
factor,
throat
t44 in. 2/ft2
diameter,
eq. (13)
injection
orifice
dt
nozzle
E
hoop modulus of elasticity ment, psi (N/m 2)
F a
axial component lbf(N)
U S
affecting with
In
to
of the
in. (cm)
figs. 39 and 42
fig. 36
of reinforce-
of the rocket
fig. 43
motor
fig. 19
thrust,
figs. 35,
36, 37,
38, 39, 40, and 42 and eq. (14)
side force due to liquid injectant, i.e., component of the total rocket motor thrust perpendicular to the motor axis,
figs. 35 - 42
lbf(N) G
effective subjected
G o
elastomer to external
shear
modulus
pressure,
elastomer secant shear modulus (3.45 x 10 s N/m 2) shear stress
when
at 50 psi and no
externally applied pressure, at the temperatures expected in operation, psi (N/m 2) Divided into three sections:
Symbols, Material Designations,
163
eqs. (2) and (3)
psi (N/m 2)
and Organization
Abbreviations
eqs. (1), (3), and (6)
Def'mition
Symbol lsp(s)
side specific
impulse,
Appears
ratio
of side force
produced by injectant to injectant flowrate causing side force, lbf-sec/lbm (N-sec/kg)
integral
i@
values
ible-joint I _1)
and 1 032)
for calculation
of
table VIII, figs.40 and 48, and eq. (14)
table
fiex-
In
V
:
spring torque
integral
values
at angles
eq. (1)
fll and/_2,
respectively
I% i¢,
correction
factor
a function
of cone angle
correction
factor
a function
of cone angle
distance
L
from
plane,
weight
Ibm/Ibm-mole Math
Mini
eq. (7)
to reinforcement
nozzle
fig. 18 and
stresses,
throat
stresses,
to nozzle
exit
in. (cm)
molecular
M
to elastomer
number
at the point
of pressurization
gas,
,
fig. 18 and eqs. (9) and (10) figs. 35, 36, 37, 38, 39, and 42 eq. (13)
(kg/kg-mole) of the rocket of secondary
expected
exhaust
gas
fig. 43
injection
MEOP
maximum
operating
pressure
MS
Margin of Safety: fraction by which the allowable load or stress exceeds the design
text eq. (5)
load or stress, MS -
number
n
1 R
of elastomer
1
rings in a flexible
joint number
ninj
P
Pal/l
Pc
b.
of injectors
operating
eqs. (6), (9), and (10) eq. (12)
pressure,
psi (N/m 2)
eq. (13)
ambient
air pressure
fig. 36
motor pressure: bustion chamber
pressure in the comof the rocket motor
eqs. (4), (7), and (9), figs. 25, 36; 38, 39, 40, 42, 43, and 48
164
Definition
Symbol
liquid injectant injector valves
Appears In
pressure
delivered to the
figs. 35,36138_ 40, 42, and 43
39,
static pressure of gas flow in the nozzle
fig. 25
static pressure of gas flow in the nozzle at the injection location
fig. 43
QLS
quadruple
various places in text
R
(1) ratio of design load or stress to the allowable load 0r stress (2) universal gas constant, lbf-ft/lbm-mole °R (J/kg-mole-K)
eq. (5)
inner joint radius
fig. 12
outer joint radius
fig. 12
pivot radius of joint measured from geometric pivot point, in. (cm)
fig. 12 and eqs:: (6), (7), (9), and (10)
Ps
_,ai
Rp
- lap shear:
eq. (13)
Ro+Ri 2
Rp-
eqs. (1) and (2)
ri
Rp -
nte/2
ro
Rp + nt_/2
eqs. (1) and (2) J
T
absolute
eq. (13)
Tq
flexible-joint (m-N)
temperature, °R (K) spring torque,
eqs. (1) and (2)
in. - lbf
• ,r,.
Ts,
inj
static temperature of the gas flow in the nozzle at the point of injection, °R (K)
fig. 43
time from start of motor
calculation procedure in sec. 3.2.1.5 ,
•
t_
A
thickness of elastomer
operation,
ring in flexible
joint, in. (cm) tr
thickness
of reinforcement
joint, in. (cm)
165
in flexible
sec
figs. 12 and 19, eqs. (6) and (7) figs. 12 and 19, eqs. (6), (7), and (10)
Definition
Symbol Vinj
velocity point
AppearsIn
of gas flow in the nozzle
of injection,
weight
flowrate
the rocket
ft/sec
fig. 43
(m/see)
of the exhaust
motor,
at the
_ '_ i :
lbm/sec
gas from
figs. 36, 38, 39,40, and 42
(kg/sec)
weight flowrate of the injectant injector into the rocket nozzle,
figs. 39, 40, and 41
from the lbm/sec
and eq. (14)
(kg/sec) X
distance
measured
line from containing ports, O/
O/1
O/inj
along
the nozzle
the nozzle throat to a plane the centers of the injection
divergence
half-angle
of nozzle
exit cone,
figs. 36, 38, and 49
fig. 42
divergence half-angle cone measured near
fig. 42
of a contoured exit the exit cone lip, deg
equivalent nozzle half-angle from the injection point to the exit plane, determined as the angle between nozzle centerline and a the injection
deg; for a conical angle,
point
nozzle,
to the exit
joint,
the angle between
the nozzle
rim,
fig. 12 eqs. (9) and (10)
deg fig. 12 and eqs. O),
inner and outer joint angles defining flexible joint geometry, deg shear
eq. (I4)
Otinj = ot
centerline and a line from the geometric pivot point to the middle of the flexible
strain
quadruple-lap A
deg
divergence half-angle of a contoured exit cone measured near the nozzle throat, deg
joint
and 42
in. (cm)
line from
3'
figs. 35 - 39
center-
incremental
in elastomer shear change
166
measured
(2), (4), (9), and (10) in
sec. 2.1.7
test in a quantity
eq. (14)
Definition
Symbol
X
angle between
Appears
the nozzle
centerline
line from an injection port side exit-plane rim, deg e
nozzle
expansion
of exit plane
ratio,
and a
In
fig. 49
to the opposite-
defined
area to throat
figs. 25,35,38,39, 40,42,43, and 48
as ratio
area
/
e inj
expansion
ratio
of the nozzle
exit cone
at
the plane of the injection ports, defined as the ratio of the area at this plane to the throat area 0
(1)
angle between motor centerline and centerline of nozzle when nozzle is rotated
(2)
P
about
density,
lbm/ft
fig. 13;eqs.(1),(2), (6),and
and
figs. 35,36,38,39, 42, and 49;eq.(14) eq. (13)
applied
motor
pressure
eqs. (3) and (4)
configuration
compressive hoop stress in reinforcements due to motor pressure, psi (N/m 2)
eqs. (9) and (10)
resultant compressive hoop stress forcements due to motor pressure nozzle vectoring, psi (N/m 2)
eq. (1 1)
in reinand
o_
compressive hoop stress due to nozzle vectoring,
in reinforcements psi (N/m 2)
eqs. (10)
7"
shear
as measured
sec. 2.1.7
stress
in elastomer
quadruple-lap
re
rr
shear
shear
psi (N/m 2)
resultant
shear
shear
stress
vectoring,
due to motor
stress in elastomer and nozzle
in elastomer psi (N/m 2)
167
in
and (11)
test, psi (N/m 2)
stress in elastomer
pressure,
motor pressure (N/m 2) rv
(10)
point,
3 (kg/m a)
relating
and flexible-joint
O" r
pivot
deg angle between motor centerline deflected thrust vector
parameter
Op
the effective
figs. 36,40,43, and 48
eqs. (7) and (8)
due to
vectoring,
due to nozzle
eq. (8)
psi
eqs. (6)and
(8)
Symbol
Definition
(1) (2)
Appears
flexible-joint cone angle, deg discharge angle of the injectant relative to the nozzle centerline,
Rp 2"4 cos
_2 :
3283
eq. (12)
fl
:
eqs. (9) and (10)
tr 3 + tr COS2 /3{Rp 2 (f12 -
/31) 2 - 3283
tr 2}
Identification
205,305,
220,231,and
608
trade
names
of Hughson
name
fiber
(polyethylene
DC 1255
trade
designation
elastomer
polymeric its length
: ERL 2256
of
E. I. du Pont
FM4030-190
material
:
44125
and
trade
of Fiberite
trade
designation
adhesive
epoxy
trade
molding
E. I. du Pont
designation
compound 20-WS-45).
Inc. for a polyester
(now
168
of General available
for silicone
can be stretched
to twice
length
terpolymer
Corp.
Carbide
Corp.
rubber
to its original
diene
Carbide
for bisphenol-A
Corp.
for
for phenolic
epoxy
epoxy
resin
resin
viscosity
impregnated
chopped
material
of FMC Corp.
of
& Co.,
temperature quickly
propylene
of Union
designation
Corp.
at room return
trade designation modifier
trade name fluorocarbons
Freon
that
for ethylene
S-glass compression FMC 47
de Nemours
of Dow Corning
trade designation of Union with viscosity modifier
:,_ERR4205
Co. for primer
terephthalate)
and on release
abbreviation
EPDM
Chemical
systems trade
Dacron
GTR
38,39,40,42,48, and 49
and the side
Material
Chemlok
fig. 12 and eq.(4) figs. 23,35,36,37,
jet deg
angle between side force resultant force vector of the ith injector
1
In
for epoxy
resin system
de Nemours
Tire only
and from
& Co.,
Rubber B.
F.
Co.
Inc.
for
a series
for natural
Goodrich
Co.
of
rubber as BFG
Material
Identification
f
GTR V-45
trade designation butadiene/acrylonitrile
of
General Tire and Rubber compound (now produced
Co. for silica-filled by HiU-Gard Rubber
Co.) trade
Hypalon
name
of
E.
chlorosulphonated IRFNA
inhibited
K1255
trade
LOX
liquid
oxygen,
MHF-3
mixed
hydrazine
Neoprene CN _ _ and Neoprene W
trade
red fuming
designation
name
synthetic
1-1 copolymer
nitroso
AFE-110
carboxy-nitroso Laboratory now
rubber
:_: S-glass
_':: S-901
rubber
acid, propellant
grade
grade
Corp.
&
Co.,
Inc.
for
per MIL-P-7254
for silicone
rubber
per MIL-P-25508
de Nemours
& Co., Inc. for general
of trifluoronitrosomethane polymer
purpose
developed
a butyl
by
rubber
by Parker-Hannifin high-energy
high-strength
and tetrafluoroethylene the
Air
Force
Materials
OH)
B-591-80;
an elastomer, either the hevea brasiliensis
trade
Nemours
(polychloroprene)
kerosene-base MIL-P-25576
Fiberglas
de
synthetic
fuel
(WPAFB,
Parker
Pont
Carbide
propellant
manufactured RP-1
nitric
of E. I. du Pont
rubber
B-591-8
du
of Union
rubber
nitroso
Parker
I.
polyethylene
used
for
O-rings;
Corporation
hydrocarbon
a synthetic tree
compound
fuel,
or a natural
MgO-A1203-SiO2
glass
propellant
compound
developed
by
grade
obtained
per
from
Owens-Coming
Corp.
designation
of
Owens-Corning
with aging surface
finish
S-904
trade designation non-aging surface
of Owens-Coming finish
$34/901
trade
of Owens-Corning
designation
glass fiber cloth
169
Fiberglas
Corp.
for S-glass fiber
Fiberglas
Corp.
for
Fiberglas
Corp.
S-glass
for woven
fiber
S-901
Identification
Material
TCC TR 3005
trade designation of Thiokol Corp. for natural
Teflon
trade
name of E. I. du Pont de Nemours
tetrafluoroethylene Thiokol
ST
Tonox 6040
rubber formulation
& Co., Inc. for a series of
polymers
trade name of Thiokol Corp. for polysulfide trade name of Uniroyal, Inc. for a blend curing agent for epoxy and urethane
elastomer of aromatic amines used as a
resins
_
Tygon ST
trade name of U. S. Stoneware
Co. for polyvinyl
UDMH
unsymmetrical
Viton A
trade name of E. I. du Pont de Nemours & Co., Inc. for a copolymer vinylidene fluoride and hexafluoropropylene
17_PH
semi-austenitic
301 304 347
designations
410
martensitic
2024
wrought
4130 4340
high-strengtl_
6061-T6
wrought aluminum temper T-6
alloy with Mg and Si as principal
7075-T6
wrought T-6
alloy with Zn as principal
dimethylhydrazine,
precipitation-hardening for austenitic
chromium aluminum
170
grade per MIL-P-25604 of
stainless steel
nickel-chromium
steels
steel
alloy with Cu as principal
martensite-hardening
aluminum
propellant
chloride
alloying element
low-alloy steels
alloying elements,
alloying element, temper
ABBREVIATIONS Identification
Organization
ABL
Allegany
ABMA
Army
AEDC
Arnold.Engineering
AFRPL
Air Force
Rocket
AIAA
American
Institute
BOWACA
Bureau
CPIA
Chemical
DAC
Douglas
ICRPG
Interagency
JANAF
Joint
Army-Navy-Air
JANNAF
Joint
Army-Navy-NASA-Air
JANAF-ARPA-NASA
Joint
Ballistics
Ballistic
Laboratory
Missile
Agency
Development Propulsion
Center
Laboratory
of Aeronautics
of Weapons
Advisory
Propulsion Aircraft
and Astronautics
Committee
Information
Agency
Company
Chemical
Rocket
Propulsion
Force Force-Advanced
National
Aeronautics
LMSC
Lockheed
Missiles
and Space
Company
LMSD
Lockheed
Missiles
and Space
Division
LPC
Lockheed
Propulsion
NAVORD
Naval Ordnance
Command
NOTS
Naval Ordnance
Test
SAE
Society
and Space
UTC
United
WPAFB
Wright-Patterson
of Automotive
Company
Station Engineers Center
Air Force
171
Group
Force
Army-Navy-Air
Technology
for Aeroballistics
Base
Research
Administration
Project
Agency-
REFERENCES 1.
Anon.:
Pintle
2.
Schaefer,
Thrust
R.
Vector
L.; and
Control.
Wilson,
K. C.:
Propellant Rockets. Bulletin June 1960, pp. 203-225. 3.
Amick, Located
4.
Strike, Located
6.
7.
Facility, S.; Lippert, ABL/Z-66
Podell,
H. L.:
Anon.:
Rocket
Fuller,
12.
13.
14.
C. M.;
Nozzle
Propellant
for
Trajectory
Group,
Vol.
Control
of Solid
2 (AD-317113),
CPIA,
P. C. Y.: Experimental Interaction Effects of Forward WTM 276, University of Michigan, March 1963. J. S.: AEDC
Interactions TDR-63-22
Produced by (AD-401911),
Sonic Lateral VonKarman
Jets Gas
1963.
P. F.; and Drewry, Hercules
Inc.,
Propulsion
Control
D. G.: A Unique
December
1963.
Subsystem
(U).
System.
W. F.: The
Study
Jones,
D.
A. T.:
Nike-Zeus
Unitized
CPIA
Thrust
Publ.
LMSC A120083,
Vector
18, Vol.
Lockheed
for a Simplified
Pershing
Manned
1960,
Propulsion
of
Certain
System. pp.
for a Simplified
Co., December
CPIA, June
June
Control
1, CPIA,
June
Missiles
and Space
Space
Vehicle.
NASA
Manned
Space
Vehicle.
DAC
16th
JANAF
Solid
1964.
System.
1960,
pp. 85-109.
Bulletin
of 16th
Bulletin
of
JANAF
Solid
Propellant
Group,
111-127.
Thrust
Vector
Control
Systems.
DAC
SM-27957,
Douglas
1961.
J. E.; Miltenberger, Thrust
Vector
Supporting
Research
Report
J. E.; and
Murray,
L.
1970,
E.;
Control -
pp.
Murray,
J. A.; _icario,
for Advanced
1969,
J. A.:
(AD-513921),
December
Steering Aircraft
Propulsion
Correlation
Magnitude,
DCN-N-5-14
Steering
of Head-End
1 (AD-317112),
CPIA,
Co., October
McNeer,
P.:
of Head-End
McDonnell-Douglas
Vol.
Aircraft
Inc./ABL,
Spike
Solid
Deitering, Stream.
Missile
II Study
and
Group,
1 (AD-317112),
McNeer,
1967.
1966.
Hickey,
(U).
Isentropic
JANAF
and Attitude
(N66-16017),
Mitchell,
Vol.
Velocity
G. M.: A Feasibility
Graves,
June
(CONFIDENTIAL)
March
Propellant 11.
The Shillelagh
CR-87450,
1962.
SM-48152 10.
April
T. E., Lease,
G. M.: Phase
Fuller,
Inc.,
(AD-349158L),
pp. 113-134.
CR-66173, 9.
ARO
System.
Co., May 8.
The
16th
W. T.; Schuelez, C. J.; and on Surfaces in a Supersonic
Kardon,
1963,
of
J. L.; Stubbleium, W.; and Chan, Side Jets on a Body of Revolution.
Dynamics 5.
NASA
Systems
Vol. 2, Hercules Thrust
Annual
Magnitude, Exploratory
1-59. (CONFIDENTIAL)
173
(U).
A.
Inc., December Thrust
A.;
and
Tulpinski,
ABL-TR-69-26
Vector
Development
1969.
Annual
(CONFIDENTIAL)
Control Report
J. E.: Thrust
(AD-507149),
for Advanced -
1970,
Vol.
Systems 2, Hercules
15. Anon.:PropulsionDevelopment Department Review.NOTSTP4100-6Part Ordnance
16. Wu,
Test Station,
Jain-Ming;
Control.
and
AFRPL
June Lee,
1 (AD-382851L),
Naval
1967.
Shen
TR-67-202
Ching:
Electric
(AD-822593),
Air Discharge
University
in Supersonic
of Tennessee,
Flow
September
for Thrust
veetor
1967. i'
"17.
Wilson, J. W.: Corp./Hercules
18. Nance, TR,70:52
Final Report, Poseidon Inc. (A Joint Venture),
B.: Advanced (AD-509374),
19. Marugg,
H.
C.;
20. Marugg,
H.
Bratton,
and
TMC-68-4-9-Bk2 (CONFIDENTIAL)
21. 22.
Control
23.
E.
O.:
Bratton,
Design,
Control
Rocket
25. 26.
Book May
1 (13). 1969.
C.
R.:
100-Inch
Motor
Program,
Book
2 (U).
Thiokol
Chemical
May
1969.
and
Corp./Wasatch
for Omniaxial Movable Co., April 1966.
Test
NASA
Demonstration
of
Omnidirectional
CR-72889,
June
Poseidon
Report-1973,
Propulsion
SE083-A2AC3HTJ-2,
27. Wilson,
W. G.:
Investigation
Mill Order
TES
Hercules
Poseidon
Nozzles
Flexible
(Lockseal).
Seals
for
Hercules
Second 74475,
Technical
Inc./Thiokol
an
Omniaxial (AD-385084),
Inc./ABL,
Stage Hercules
Review
Report-
Chemical
Corp.
Elastocomposite Inc./ABL,
February
Vector
Flexible Seal Movable Thiokol Chemical
January
AIAA
1 July (A Joint
Joint,
Final
Paper
1974,
Report
pp.
73-1262,
through Venture),
Thrust Vector Research and 115-199.
AIAA/SAE
30 September October Task
9th
1973.
1973.
II A-5. Poseidon
1971.
*Dossier,f0r design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
174
Thrust
AFRPL
1971.
Sherard, H.: Development of Advanced Flex Joint Technology. Propulsion Conference (Las Vegas, NV), Nov. 5-7, 1973. Anon.:
Div.,
J. E.; and Murray, J. A.: Integral Rocket Ramjet Booster System Demonstration (U). DCN-N-37-23, Annual
Exploratory Development (CONFIDENTIAL)
AFRPL
Program, Div.,
Motors.
L. E., McNeer, Nozzle Eject
'and
Chemical
Motor Demonstration Chemical Corp./Wasatch
ReportDevelopment and Demonstration of Thrust Vector Control. AFRPL TR-67-196, Div., October 1967.
24. Miltenberger,
Thiokol
100-Inch Thiokol
an Elastomeric Seal Lockheed Propulsion
Fabrication
of Large Solid
Anon.: Final Nozzle for Corp./Wasatch
TWR-2486,
R.:
(AD-502027L),
Anon.: Development of TR-66-11:2 (AD-373032), Wong,
Rep.
C.
(AD-502026L),
C.;
Joint.
Dual Chamber Propulsion System Component Design Report (If). Thiokol Chemical Corp./Wasatch Div., May 1970. (CONFIDENTIAL)'
and
TMC-68-4-9-Bkl (CONFIDENTIAL)
C3 Joint Venture July 1967.
Unpublished. Collected
source material
28. White,T. C.:ThrustVectorControl- Elastocomposite Joint(U).DCN-N-17-6, AnnualExploratory Research Report- 1971,Vol.2, Hercules Inc./ABL,February1972,pp. 1-68.(CONFIDENTIAL) 29.Miltenberger,L. E.: Elastocomposite Joint-Thrust Vector Control (U). DCN-N-26-2, Annual Research andExploratoryDevelopment Report- 1972,Vol.2. Hercules Inc./ABL,December 1972, pp. 119-202. (CONFIDENTIAL) 30. Hurley,L. H.; and Kimmel,N. A.: Applicationof ControllableSolidsin ReentryMeasurements Program (U).Rep.TR-0059($6816-89)-1, Aerospace Corp.,Aug.31,1970.(CONFIDENTIAL) 31. Bertocci,R. P.: The Nike-ZeusPropulsionandJetheadControl Systems(U). Bulletinof 18th JANAF-ARPA-NASA SolidPropellant Group,Vol. 1 (AD-330129), CPIA,June1962,pp.161-179. (CONFIDENTIAL) 32. Kirchner,W. R.: Development of Advanced PolarisFirst StagePropulsionSystem(U). Bulletinof 18thJANAF-ARPA-NASA SolidPropellant Group,Vol. 1 (AD-330129), CPIA,June1962,pp.3-27. (CONFIDENTIAL) 33. Ellis,R. A.: Development of a Carbon-Carbon Nozzlefor the TridentI (C4)ThirdStageMotor(U). CPIAPubl.242,Vol. I, CPIA,November 1973,pp.89-115. 34.
Sinclair, C. A.: Development CPIA Publ. 242, Vol. I, CPIA,
35.
Goddard,
S. G.: Demonstration
Vol. I, Thiokol 36.
Schoen, Techroll
of a High November
Chemical
Performance Third Stage Motor for the 1973, pp. 117-145. (CONFIDENTIAL)
of Advanced
Corp./Wasatch
ICBM Components
Div., January
Program,
Phase
Trident
I (C4)
(U).
I. AFRPL-TR-73-37,
1974.
c_. L.; Bahnsen, "_" Seal Movable
E. B.; Conner, G. E.; and Grimsley, Nozzle System. AFRPL-TR-73-47,
J. R.:
Propulsion
J. L.: Exploratory Development for the Vol. I, United Technology Center, June
1973. 37.
38.
Crooks, Group,
Vol.
Anon.:
156
CPIA,
Inch
Motor
1965.
Nance,
P. D.:
Hirsch,
N,
(AD-371800), 41.
Waldeck, Rep.
Diameter
AD-365662,
August
Final
(AD-376999), 40.
Report,
Thiokol A.;
June
Submerged
Chemical
Slegers, Air Force
L.;
1962,
pp.
and
and
Thrasher,
R. V.; Deslauriers, Corp.,
113-122. Program.
Nozzle
I.:
AFRPL-TR-65-4 Thiokol
Development,
Div., June D.
JANAF-ARPA-NASA
Air Force
E. J.; and McVey,
(Washington,
175
D.C.),
Propellant
(5 vols:
AD-365660,
Chemical
Corp./Wasatch
Div.,
Appendix
D. BSD-TR-66-31/C
1966.
Gimballed
(Edwards
Solid
(CONFIDENTIAL)
AD470452),
Gimbal
Command,
of 18th
Nozzle
Corp./Wasatch
Systems
Pneumodynamics
Bulletin
Movable
AD-365663,
G. H.; Hensley,
6602-1,
System.
I (AD-330129),
AD-365661,
39.
Skybolt
Integral
Nozzle.
Base, CA),
F. D.: Flexible
September
1959.
AFRPL-TR-64-172
December Skirt
1965. Nozzle
(CONFIDENTIAL)
Program.
42.: Waldecki_G. H.: :_
Skirt
Nozzle
Program
(U). Rep. 6602-i,
Pneumodynamics
Corp.,
July
1960.
Flexible
Skirt
Nozzle
Program
(U). Rep.
Pneumodynamics
Corp.,
November
(CONFIDENTIAL)
43.
Waldeck,
:,
1960. 44.
G. H.:
R. E.: Reinforced
Rocketdyne
45.
Hoover,
Div., G. H.:
.., _./._.: k(AD7373908), 46.
6602-k,
(CONFIDENTIAL)
Spann,
• : .
Rains,
Grain
North An
D. A.: Solid Solid
Advanced
American
Nozzle
1966,
Propellant
Development
Aviation,
Omnivector
CPIA , June
Interagency ,,
Flexible
for
pp. 813-842.
Motor
Propulsion
Thrust
AFRPL-TR-66-239
(AD-377073),
1966. Vector
Control
(U).
CPIA
Publ.
111,
Vol.
(CONFIDENTIAL)
Thrust
Meeting,
Program.
Inc.,•October
Vector
Control
Vol.
1
I and
II.
2
• ....
System
for Titan
(AD-352176),
CPIA,
III (U). Bulletin
May
1964,
of 20th
pp.
225-262.
_, (CONFIDENTIAL) y_.;
:
47.
i.i
.
Anon.:
TVC
(Sunnyvale, "48.
Systems
Analysis,
CA), April
Parts
UTC
4404-70-330,
United
Technology
Center
1971.
Huff, W. G.: Theoretical Control System (LO.
Analysis and LMSC 806591,
Functional Description Lockheed Missiles
of the Polaris A3 Thrust and Space Corp., May
Vector 1967.
(CONFIDENTIAL) 49.
Collis,
D. R.;
and
Rimington,
D.
A.:
Thrust
_ _ .;Liquid Injection (U). Bulletin of :, : :_(AD-352176), May 1964, pp. 263-281. 50.
Conklin,
.... 51.
Anon.: , NASA
52. ..
C. L.: The Sprint
CPIA, June
1968,
Thrust
Vector
C. G.:
20th Interageney (CONFIDENTIAL)
Vector
System
Chemical
Development
Control
Control
of the
Solid
System
Minuteman
Stage
Propulsion
Meeting,
(U). CPIA Publ.
167, Vol.
II Motor
CPIA,
by
VoL
and
Study
Corp.,
Program,
June
1, (AD-389918),
Final
Report
and
Final
Report
Summary.
1 1970.
Demonstration
, Control System for LSRM - Final Report AD-847113, and AD-847114), Thiokol
of
a Chamber
(U). AFRPL-TR-68-166, Chemical Corp./Wasatch
Bleed Vols. Div.,
Hot
Gas Thrust
Vector
I, II, and III (AD-395219, October 1967. (VOL.
CONFIDENTIAL) 53.? Benj0ck, G,' F.: Design (AD-350933), Hercules 54.
,*Dossier available
of Propellant Inc., February
Gas Secondary Injection 1964. (CONFIDENTIAL)
Thrust
Vector
Ar_on.: Development of a Hot Gas Valve for Secondary Injection AFRPL-TDR-64-33 (AD-348778), Lockheed Propulsion Co., March 1964.
for for
design_ inspection
Criteria
monograph
at NASA
Lewis
1
(CONFIDENTIAL)
Control
CR-72727,Thiokol
Kennedy,
Thrust
pp. 219-232.
Vector
"Solid
Rocket
Thrust
Research
Center,
Cleveland,
176
Vector Ohio.
Control."
Unpublished.
Control
Thrust
Collected
(U). ABL
Vector
source
X!02
Control.
material
I
55. Brownson, H.: Feasibility Demonstration for Direct Chamber Bleed Hot Gas Secondary Injection Thrust Vector Control - Final Report. AFRPL-66-224 (Vol. 1, Bk 1: AD-800937; Vol. 1, Bk2: AD-800938; Vol. 2: AD-800939), Lockheed Propulsion Co., September 1966. 56. Anon.: Proportional Solid Propellant CR-637, November 1966.
Secondary
Injection
Thrust
Vector
Control
Study.
NASA
57.
Bonin,
58.
Drewry, D. G.; and Newman; R. M.: Methods for Thrust Vector Control of Solid Propellant Rockets. Bulletin of 16th JANAF Solid Propellant Group, Vol. 2 (AD-317113), CPIA, June 1960, pp. 227-248.
59.
Anon.: Stage I Minuteman (M55A1) Production Support -Final Report, Appendix C, Submerged Hot Gas Valve Development. BSD-TR-66-31 (AD-373063L), Thiokol Chemical Corp./Wasatch Div., May 1966.
0.
J.; Fitzgerald, J. E.; and Miller, E.: Hybrid Thrust Vector Control 572-F (AD-330226), Lockheed Propulsion Co., June 1962. (CONFIDENTIAL)
Anon.: Development and Demonstration of Flightweight Thrust Vector Control Hardware, Interim Progress Report No. 2 (U). AFRPL-TR-67-92 (AD-380241), Thiokol Chemical Corp./Wasatch: Div., March 1967. (CONFIDENTIAL) Anon.:
NASA Propellant
Gas Valve Scale-Up Program
Final Report.
Shipley, J. D.; and Drewry, D. G.: Application of Propellant High Pressure, High Acceleration Solid Propellant Rocket Hercules Inc., May 1964. 63.
4°
• 65:
••66.
67.
NASA CR-78004,
March 1966.
Gas Valves for Thrust Vector Control of Motors. Rep. ABL[Z.72 (AD-353317),
Robinson, D. J.; and Montgomery, L. C.: Sergeant Motor Jet Vanes (U). Rep. (AD-321938), Jet Propulsion Lab., Calif. Inst. Tech., June 1960. (CONFIDENTIAL)
JPL 20-136
Skirmer, E. H.; 504, and Werner, C. T.: X SAM-N-66 Talos Weapon Jet Vane AerodynamieReport, X230-A5 Booster Unit. Rep. BPD 4330, Bendix Corp., February 1955. Davis; R. E.; O'Callaghan, T.; and Selbert, J. R.: The Jetevator as a Vector Control Deyice, Development of the Polaris Jetevator. CPIA Publ. 18A, Vol. 4 (AD-346945), CPIA July 1963, pp. 391-412. Gowen; L. F.: Subroc Propulsion CPIA, June 1960, pp. 63-83. Edwards, Control.
68.
Systems (U). Rep. LPC
S. S.; and •Parker, Rep. LMSD,2630,
System.
Bulletin of 16th JANAF
G. H.: An Investigation Lockheed
Solid Propellant
of the Jetevator
Missiles and Space Co., February
Group, Vol. 1,
as a Means of Thrust
Vector
1958.
Huizinga, J.: Jetevator Effectiveness and Base Pressure Measurements for FTV-1 and AX Polaris Missiles Tested at NASA - Lewis Laboratory. Rep. LMSC 462055, Lockheed Missiles andSpace Co., November 1958.
177
69.
Anon.: XM-38 Solid Propellant Corp./Wasatch Div., June 1959.
70.
Anon.: Jet Tab December 1961.
71.
Hollstein, H. J.: Jet pp. 927-930.
72.
Anon.: Cooled BPAD-863-14544,
73.
Auble,
Thrust
Vector
Control.
Tab Thrust
Vector
18, Vol.
Tab Thrust June
75.
Anon.: SP-8115
76.
Anon.: NASA
77.
Harrison, T.; Colbert, L.; Dykstra, for Application of Lockseal to December 1966.
Rocket Actuators May 1973.
and
Lockheed
Rockets,
Vector
1963.
Anon.: 156-Inch Diameter Motor Jet Tab ProgramAD-357024, Vol. 2: AD-357025, Vol. 3: AD-357026, Lockheed Propulsion Co., January 1965.
Liquid SP-8090,
TU-68-5-59,
NASA
Operators.
Control
Firing
Vehicle
NASA
Space
H.; Sullivan, P.; and McCorkle, 260-Inch Solid Rocket Motor-
Criteria
Vehicle
Design
Joints.
Matthews,
to
80.
Chemical
W.:
Application
Propulsion
F.
Structural
81.
Wilson, E. L.: Structural pp. 2269-2274.
82.
Dunham, Loadings.
of
Large
Integrity
Analysis
Poseidon
Investigation
Deformation Survey
of Axisymmetric
Theory
1972,
(U).
Rep.
Motors.
CPIA Publ.
Solids.
AIAA
Monograph,
Criteria
J.: Design Study Final Report.
Woodberry, R. F. H.: Rapid Design Equations for Elastometallic No. Misc/6/50-1113, Hercules Inc./Bacchus, Nov. 30, 1973.
Analysis-
Co.,
1965,
Solid Rocket
Design
*79.
Joint
Space
Report. AFRPL-TR-64-167 (Vol. 1: 4: AD-357027, Vol. 5: AD-357028),
Galford, February
Unstable
and
Evaluation
for Large
*78.
J. E.: 1971.
Missiles
Chemical
pp. 241-286. Final Vol.
Space
Thiokol
vol. 2, no. 6, Nov.-Dec.
Full Scale Rocket Motor 1962. (CONFIDENTIAL)
CPIA,
Nozzles.
Rep.
800917,
J. Spacecraft
74.
Solid Rocket Motor (to be published).
I (U).
LMSC
Control.
L, J.: Jet
3 (AD-338667L),
Vol.
Rep.
Probe TVC Systems for Bendix Corp., September
C. M.; and Spielberger,
CPIA Publ.
Rocket Motor, (CONFIDENTIAL)
Task
II-A.
CPIA,
Inc./Magna,
to J. E. McNeer,
Chamber
229,
Monograph,
and CostEstimate NASA CR-83073,
Hercules
Memo
NASA
Analysis September
J., vol. 3, no.
and
Ref.
Design.
1972.
12, December
1965,
R. S.; and NickeU, R. E.: Finite Element Analysis of Axisymmetric Solids with Arbitrary Rep. SEL-67-6 (AD-655253), University of California (Berkeley, CA), June 1967.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
178
Unpublished.
Collected
source material
83.
Eringen, A. C.: Small Twist Superimposed Shell. Tech. Rep. 12-3, General Technology
84. Kafadar,
C. B.; and
Hydrostatic (Lawrenceville,
851 Danninger,
Eringen,
*87.
Program Department,
Cronkrite,
W. R.: Analysis
Actuation
Torque
Tests.
W. R.:
Analysis
Cronkrite, Torque
Tests.
Rep.
Solid
Tech.
Rep.
A. R.: Project
Quick
Spherical 12-2,
Turn
Movalbe
Stage
Poseidon
17-10203/6/40-475
of First
Stage
17-10203/6/40-455
Machined
(HA-05960),
Poseidon
Flexible
(HA-04006),
Inc./Magna,
Axial
89.
Lund, R. K.: Final Report - Cold Flow Tests Poseidon Thiokol Chemical Corp./Hercules Inc. (A Joint Venture),
90.
Shapiro,
A. H.: The Dynamics
and Thermodynamics
Fluid
Anon.: Nozzle Joint, Method for Actuation, Department of the Navy, Naval Ordnance Systems
Axial Deflection, Command, March
*92.
Briggs,
Test
93.
*94.
W.; and Greenleaf,
LPC 754-STR-3,
Anon.: Electric
R. D.:
893-F,
Lockheed
Final
G.:
Lockseal
Lockheed
Silicone Rubber Co. (Waterford,
Wells,
Vector for
October
the
and 1967.
Actuation
1967.
Report
(U).
Stage.
Rep.
Flow.
Vol.
Data
Item
TWR-2320,
1, Ch. 15. The
1953.
"91.
Rep.
Thrust
and
to
Corp.
Deflection
Deflection
C3 First and Second February 1967.
of Compressible
Axial
October
Allen, M. J.: Poseidon C3 Second Stage Phase II Design Compliance SE048-A2A01HTJ, Rep. 9, Hercules Inc., March 1971. (CONFIDENTIAL)
Press Co.,
Nozzle
Joint
Inc./Magna,
Ring Subject
Propulsion Co. (CONFIDENTIAL)
Flexible
Joint
Hercules
Spherical
Technology
Hercules
88.
Ronald
Annular
General
(U). Rep. NWC-TP-4794, Lockheed Naval Weapons Center, August 1971.
of Second Rep.
Elastic,
Bending.
C. R.; and White,
Control Demonstration Propulsion Development *86.
A. C.: An Anisotropic,
Pressure and Prescribed N. J.), December 1970. G. A.; Pignoli,
on a Finite Compression of a Thick Anisotropic Corp. (Lawrenceville, N. J.), December 1970.
Subscale
Propulsion
Co., Feb.
for Design Engineers. N.Y.), no date.
Report
Propulsion
Task
II-
Co., February
95.
Anon.: System
Poseidon C3 First Stage (U). Hercules Inc./Thiokol
96.
Anon.:
Poseidon
System
(U). Hercules
C3 Second
I and
General
Synthetic
Report
and Leak 1971.
Results
of Test
Tests.
Series
Stage
Phase
No. 4, 8, and 15.
Electric
Technical
Elastomer
Data
Book
Development
S-1D,
Program.
General
Rep.
LPC
1969.
II Design
Chemical
Corp.,
Compliance Mar. 24,
Report, 1971.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
179 i
43336C,
1968.
Phase II Design Compliance Report, Fleet Ballistic Chemical Corp., Mar. 16, 1971. (CONFIDENTIAL)
Inc./Thiokol
OD
\
Fleet
Ballistic
Missile
Weapon
Missile Weapon
(CONFIDENTIAL)
Unpublished.
Collected
source material
*97.
Peterson, M. R.: SF002-A2A01HTJ, March
*98.
1971.
Anon.:
*99.
*100.
*101.
Compound,
Command,
Weapons
August
Specification.
Weapons
Naval Ordnance
Systems
Command,
September
AnOn.:
Memorandum
- Elastomer
Tire and Rubber
Co., November
Anon.:
Test
Special
Special
G.;
Vector
Test
Povinelli,
WS 8008E,
Department
of Navy,
Naval
Specification.
WS 12006B,
Department
of the Navy,
1969.
44125,
Lots
14, 15, and 16. Ref.
No. GA 15729,'General
Stage
Buckle
Test
Unit
Ref.
No.
OML
77223,
Ref.
No.
OML
77222,
DO08
(D010).
Second
Stage
Buckle
Test
Unit
D005/D008.
Co., Aug. 4, 1967. H.;
and
CR-803,
J. F.; and Control.
Material
First
Report,
Armen,
NASA
Newton,
Item No. Venture),
Co., Aug. 4, 1967.
Propulsion
Structures.
Status Report (U)._Data Chemical Corp. (A Joint
1968.
Report,
Propulsion
Isakson,
Reliability Inc./Thiokol
1970.
Compound,
Lockheed
103.
Quarterly Hercules
Rubber
• 102. _ Anon.:
104.
II20A,
Natural
Lockheed
103.
Rubber
Systems
Anon.:
Phase No.
(CONFIDENTIAL)
Natural
Ordnance
Poseidon Submittal
October
Spaid,
ARS
Pipko,
A.:
Discrete
Methods
for
the
Plastic
Analysis
of
1967.
F. W.: Interaction
J., vol. 32, August
F. P.: Displacement
Element
of Secondary
1962,
pp.
of Disintegrating
Injectants
and Rocket
Exlaaust
for Thrust
1203-1211.
Liquid
Jets in Crossflow.
NASA
TN D-4334,
i_ebruary
1968. 106.
Kurzins, Density
*10"I.
"108.
R.
Hercules
Inc./ABL,
Grunwald,
111.
J.:
G. J.: Polaris
Huizlnga,
J.:
Liquid
Missiles
Anon.:
Chemical
Science
Corp.
Anon.:
Principles July
of
Thrust
Sizes
in Liquid
December
1968.
(CONFIDENTIAL)
Vector
and Second
Lockheed
and Space
Corrosion
Center
Rocket
Injection
Aspects
of Droplet
CR-1242,
Control
by
Fluid
Jets
Atomized
Injection.
in Low
Memorandum,
1961. B3 First
(Sunnyvale,
Stress
Technology
Measurement
(U). NASA
(U). LMSC 804506,
Lockheed *110.
F. H.:
Streams
Zeamer,
Report "109.
S. C.; and Raab, Supersonic
Thrust
of
Fluid
Test
(Sunnyvale,
Evaluation, CA), July
Injection
Thrust
Co., October
Control
1961.
1964.
Effectiveness
(U).
Vector
Control
Data
(CONFIDENTIAL) Rep.
LMSC
800877,
(CONFIDENTIAL)
Injection
May 1961,
Secondary
and Space
Vector
Co., August
CA),
Stage
Missiles
(U).
July
Rep.
1961,
Final
Nos.
R-l,
and August Report
(Titan
R-2, 1961. III).
and R-3
of P-27,
Dynamic
(CONFIDENTIAL) UTC-4802-67-181,
United
10, 1969.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
180
Unpublished.
CoUeeted
source
material
112.
Anon.: Titala III-M TVC System Seal Material Compatibility and Pyroseal Development 'UTC-4802-68-i04, United Technology Center (Sunnyvale, CA), April 22, 1968.
113.
Childress,
H. E.; and
Mastrolia,
Rep. 0162-06 TDR-9, September i9B5.
Vol.
E. J.: System 2 (Part
Support
1, AD-479227; =
Studies Part
Under
ProductiOn
2, AD-479205),
AnÙn.: Static Test Report TVC 50-Cycle/75-Day Hold Technology center (Sunnyvale, CA), September 1970.
115.
H0nma, Missiles
116.
Hess, F. D.: Diffusion of Perchlorate Solutions Through Elastomer TOR-669(6855-20)-I (AD-482982), Aerospace Corp., February 1966.
117.
Anon.: Atlantic
Freon Compatibility Studies. Research Corp., 1961-1962.
Perchlorate
Monthly
118.
Anon.: An Evaluation of Composite Teflon-Aluminum Propulsion System. NASA CR-84663, March 1967.
119.
Ross, L. G.; and LeFebvre, Ablative Performance. NASA
*120._
Hi'rsch, R. L.: Physical Properties and Aetojet-General Corp., June 24, 1963.
"121.
LeC0unt, R. L;: Fluid (BOWACA),Lockheed
• 122.
Grunwald, Lockheed
123.
"124.
and
Water
Progress
C. A.: Determination CR-72792, DeCember
Support
Aerojet
Recycle.
UTC
Solutions.
Reports
Foil
of the 1970.
Compatibility
1-10,
Rep.
Corp.,
Effects
of Strontium
4404-70-230.
Wu, Jain,Ming; Chapkis, R. L.; Ai, D. K.; and Rao, G. V. R.: Liquid National Engineering Science Co. (Pasadena, CA), July 1961.
LMSC
BSD-TR-66-93,
Subcontract
for
the
of Liquid
Surveyor
Thrust
LeCounL R. L.; et al.: Preliminary Data Release of Fluid Injection Thrust Vector LMSC DP/M-431, DP/M-557, and DP/M-722, Lockheed Missiles and Space Co., 1960.
"126.
Zeamer, R. J.: The Thrust. Memorandum,
on TVC
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." Unpublished. available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
on Nozzle
Memo,
Jet Effects
(U). TM 53-42-4,
"125.
Parameters 1965.
Vernier
Interoffice
Panel
LMSC 803311,
Vector
R. G.: Preliminary Results of P-29 Fluid Injection Lockheed Missile s and Space cO., November 196i.
Effect of Some Nozzle and TVC Hercules Inc./Magna, September
18-10703,
Injectants
Perchlorate.
Injection
United
IDC 52-30, Lockheed ' .... '_ ' _ ....
Membranes.
Bladders
G. J.; and LeCount, R. L.: Fluid Injection TVC Research Missiles and Space Co., October 1963. (CONFIDENTIAL)
181
Program.
General
Injection TVC Research (U). Report to Rocket and Nozzles Missiles and SpaCe Co., July 1963. (CONFIDENTIAL)
Grunwald, G_J.; and Anderson, _'Cotitr01 _Fests_ Re pl IDC-57-11-356,
Report.
_
114.
J.: Research Study, Strontium and Space Co., September 1963.
Test
Thrust
Vector _
Control
Effectiveness
Collected
Control.
Tests.
and Motor
source material
'i27, Anon.: PolarisB3 Fluid InjectionTVC (U). LMSC804632,LockheedMissilesand SpaceCo., October1964.(CONFIDENTIAL) "128. Anon.: Titan III Thrust Vector Control Fluid RequirementUtilizing UBS. Tech. Memo. 5141/31-68-02, Martin-Marietta Corp.(Denver, CO) January1968. "129. LeCount, Missiles 130. ..... 131.
R.
L.:
Fluid
and Space
Anon.: Weapons GM-TR-0165-00478, Anon.:
Item
(U). Figure
Injection
Co., May
Thrust
System 133B, Aerojet-General
Detailed A6658,
Second Corp.,
Specification
Thiokol
Vector
Control
No. S-133-1003-0-4,
Corp.,
Analysis
Jan.
6, 1972.
133.
Anon.: 156-5.
134.
Charwat, A. F.; Roos, J. N.; Dewey, F. C.; Flows - Part I - The Pressure Field. J. Aerospace
135.
Charwat, Flows-
F.; II-
Rep.
IDC-57-11-59,
Lockheed
(Titan
III
Wing VI Motor Data 1969. (CONFIDENTIAL).
Motor,
Solid
Book
Propellant
Model
United
Technology
Report,
Test
(U).
SR-73-AJ-I
(CONFIDENTIAL)
Anon.: TVC System December 1970.
A. Part
P-10.
Stage/Minuteman Revised March 21,
132.
156-Inch Diameter AFRPL-TR-66-109,
Test
1961.
C/D).
UTC
4404-70-330,
Motor Liquid Injection TVC Program Vol. 2, Lockheed Propulsion Co., July
Final 1966.
Center,
Results,
Motor
and Hitz, J. A.: An Investigation of Separated Sci., vol. 28, no. 6, June 1961, pp. 457-470.
Roos, J. N.; Dewey, F. C.; and Hitz, J. A.: An Investigation of Separated Flow in the Cavity and Heat Transfer. J. Aerospace Sci., vol. 28, no. 7, July 1961,
pp. 513-527. "136.
Zeamer,
R. J.:
Memorandum, 137.
138. "139.
140.
Anon.:
156-Inch
October
1965.
Anon.:
Hibex.
McQueen, Inc./ABL,
142.
Injection
Fiberglass
Rep.
Thrust
Inc./ABL,
LITVC
D2-99600-1
Vector
August
Control,
Starrett,
D.: Final
Report
Motor
Program.
(AD-371266L),
Co., October
Anon.:
Polaris
Space
Co., March
- Sprint
Fluid
1964. Injection
Missile
Distribution
of Loads
Due
to Vectoring.
1963. AFRPL-TR-65-192,
The Boeing
J. E.: Thrust Vector Control System October 1965. (CONFIDENTIAL)
and Space 141.
Fluid Hercules
Operation
Control
Study
Co., March Report
(U). Rep.
Thiokol
Chemical
Corp.,
1966.
(U). Rep.
LMSC
ZM-656-401D,
665480,
Hercules
Lockheed
Missiles
(CONFIDENTIAL) Thrust
Vector
:Control.
Rep.
LMSC
800550,
Lockheed
Missiles
and
1961.
Speisman, C.; and Kallis, 63-1942.27-28, Aerospace
J.: Preliminary Results, Corp., (San Bernadino,
Quadrant Interaction CA), June 3, 1963.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio. 182
Analytical
Unpublished.
Study
CoUeeted
Effort.
Rep.
source material
143. Hair,L. M.; andBaumgartner, A. T.: An EmpiricalPerformance Modelof Secondary Injection Thrust Vector Control (CONFIDENTIAL) "144. ! Green, August 145.
146.
C. J.i Desired 1960.
Green, C. Preliminary Walker,
R. E.; and
Rep.
Properties
J.: Effects Summary
Control. Preprint 29-31, 1964.
(U).
of the
4-64-014,
Lockheed
Injectant.
Rep.
Missiles
4511-196,
and
Space
U. S, Naval
Co., October
Ordnance
Test
Shandor,
M.: Influence
64-112,
Injection
AIAA
Properties
Propellant
Anon.: August
148.
Large, Corp.,
149.
Daniels, C. J.; et al.: Thrust VeCtor Control Requirements Rocket First Stage. NASA TM X-1906, December 1969.
150.
Lloyd, 1962.
151.
Lee, R. S. N.: Vector Control
152.
Obert,
153.
Anon.: Ullage Blowdown System Fluid Technology Center, March 11, 1971.
154.
Anon.: Solid Propellant Grain Design and Monograph, NASA SP-8076, March 1972.
155.
Anon.: Liquid Rocket Metal Tanks and Monograph, NASA SP-8088, May 1974.
156,
Anon.: Valves.
Liquid Rocket Pressure Regulator, NASA Space Vehicle Design Criteria
157.
Anon.: Criteria
Solid Rocket Motor Performance Analysis Monograph, NASA SP-8039, May 1971.
J. P.: Concepts June 1963.
and
D. K.; and Lipow,
Scaling
of Injectant
Solid
147.
Effects.
Procedures
Rep_
of Cost
M.: Reliability:
Rocket
4511-195,
Analysis.
Management,
Rep.
for Fluid
U.S.
Naval
Thrust
(Palo
Alto,
Ordnance
RM-3589-PR
for Launch
Methods
Injection
Conference
Station,
(AD
Vehicles
of Thermodynamics.
McGraw-Hill Expulsion
Internal
Tank
Book
Co. (New
Performance.
UTC
Ballistics.
Components.
York),
Station,
411554),
RAND
Prentice-Hall,
183
Inc.,
Thrust
440A-70-310,
Rev. A., United
NASA
Space
Vehicle
Design
Criteria
NASA
Space
Vehicle
Design
Criteria
Prediction.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
Solid
1960.
Relief Valves, Check •Valves, Burst Disks, Monograph, NASA SP-8080, March 1973. and
Jan.
Test
Using a 260-Inch
and Mathematics.
Vector
CA),
A Computer Program for Conducting Parametric Studies of Liquid Injection Systems. Rep. BOAC D2-30873 (AD-812413L), The Boeing Company, 1964.
E. F.: Concepts
for 1964.
of Additives on Propellant Performance and Motor Operating Conditions. Report 1DP1210, U. S. Naval Ordnance Test Station, December 1960.
No.
Secondary 1960.
LMSC
NASA
Unpublished.
Space
Collected
and Explosive
Vehicle
Design
source material
FirstStageMotor. "158. Anon.:StructuralandThermalAnalysisFinalReport,Poseidon Data
Item
October
159. Heaton,
No. SEO25-A2A00HTJ,
Rep.
1, Hercules
Inc./Thiokol
Chemical
Corp.
Vol. III - Nozzle. (A Joint Venture),
1970. H.
(AD-510749),
S.; and
Daines,
Hercules
W. L.: Flow
Inc./Magna,
Field
September
Analysis 1970.
of Rocket
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
184
Motors
(U).
AFRPL-TR-70-98
(CONFIDENTIAL)
Unpublished.
Collected
source
material
NASA SPACE VEHICLE DESIGN CRITERIA MONOGRAPHS ISSUED TO DATE
ENVIRONMENT SP-8005
Solar
SP-8010
Models
of Mars Atmosphere
SP-8011
Models
of Venus
SP-8013
Electromagnetic
Radiation,
SP-8017
Magnetic
SP-8020
Mars Surface
SP-8021
Models
SP-8023
Lunar
SP-8037
Assessment
SP-8038
Meteoroid Environment October 1970
SP-8049
The Earth's
SP-8067
Earth
SP-8069
The Planet
SP-8084
Surface Revised
SP-8085
The Planet
Mercury
SP-8091
The Planet
Saturn
SP-8092
Assessment June 1972
and
(1968),
Models,
(90
March
(1970),
to
Lunar
March
1969
km),
Revised
Surface),
to 2500
March
1973
Magnetic
(1970),
(Interplanetary
Radiation,
July
December
1971
(1971),
(Launch
March June of
Fields,
September and
1970
Planetary),
1971
Extremes
Control
Earth
1972
1969
Model-1970
and Emitted
185
(Near
of Spacecraft
Ionosphere,
Atmospheric June 1974
September
May 1969
and Control
Jupiter
Revised
May
Atmosphere
1971
1968
and Extraterrestrial,
Models
of Earth's
May
May
Model-1969
Fields-Earth
Albedo
(1967),
Atmosphere(1972),
Meteoroid Environment March 1969
Surface
Revised
1971
and
Transportation
Areas),
1972
1972
Spacecraft
Electromagnetic
Interference,
SP-8103
ThePlanets Uranus, Neptune,andPluto(1971),November 1972
SP-8105
Spacecraft ThermalControl,May1973
SP-8111
Assessment andControlof Electrostatic Charges, May1974
STRUCTURES SP-8001
BuffetingDuringAtmospheric Ascent,Revised November 1970
SP-8002
Flight-Loads Measurements DuringLaunchandExit, December 1964
SP-8003
Flutter,Buzz,andDivergence, July 1964
SP-8004
PanelFlutter,Revised June1972
SP-8006
LocalSteadyAerodynamic LoadsDuringLaunchandExit, May 1965
SP-8007
Bucklingof Thin-Walled CircularCylinders, Revised August1968
SP-8008
Prelaunch GroundWindLoads,November 1965
SP-8009
Propellant SloshLoads,August1968
SP-8012
NaturalVibrationModalAnalysis,September 1968
SP-8014
EntryThermal Protection,August1968
SP-8019
Bucklingof Thin-Walled Truncated Cones,September 1968
SP-8022
Staging Loads,February1969
SP-8029
Aerodynamic andRocket-Exhaust HeatingDuringLaunchandAscent May1969
SP-8030
Transient LoadsFromThrustExcitation,February1969
SP-8031
SloshSuppression, May1969
SP-8032
Bucklingof Thin-Walled DoublyCurvedShells,August1969
SP-8035
WindLoadsDuringAscent,June1970
SP-8040
FractureControlof MetallicPressure Vessels, May1970
SP-8042
MeteoroidDamage Assessment, May1970
186
SP-8043
Design-Development Testing,May1970
SP_044
Qualification Testing, May1970
SP-8045
Acceptance Testing,April 1970
SP-8046
LandingImpactAttenuationfor Non-Surface-Planing Landers,April 1970
SP-8050
StructuralVibrationPrediction, June1970
SP-8053
NuclearandSpace RadiationEffectsonMaterials, June1970
SP-8054
Space RadiationProtection, June1970
SP-8055
Prevention of CoupledStructure-Propulsion Instability(Pogo),October 1970
SP-8056
FlightSeparation Mechanisms, October1970
SP-8057
StructuralDesignCriteriaApplicable to a Space Shuttle,Revised March 1972
SP-8060
Compartment Venting,November 1970
SP-8061
Interactionwith Umbilicals andLaunchStand,August1970
SP-8062
EntryGasdynamic Heating,January1971
SP-8063
Lubrication,Friction,andWear,June1971
SP-8066
Deployable Aerodynamic Deceleration Systems, June1971
SP-8068
BucklingStrengthof StructuralPlates,June1971
SP-8072
AcousticLoadsGenerated by thePropulsion System, June1971
SP-8077
Transportation andHandlingLoads,September 1971
SP-8079
StructuralInteraction with ControlSystems, November 1971
SP-8082
Stress-Corrosion Cracking in Metals,August1971
SP-8083 SP-8095
" DiscontinuityStresses in MetallicPressure Vessels, November 1971 PreliminaryCriteria for the FractureControl of SpaceShuttle Structures, June1971
187
SP-8099
Combining AscentLoads,May1972
_...
SP-8104
Struc, tural InteractionWith Transportationand Hand!ingSystems, January1973
GUIDANCE ANDCONTROL SP-8015
Guidance andNavigation for EntryVehicles,November 1968 "
SP-8016
Effectsof StructuralFlexibilityon Spacecraft Control
Systems,:
April
1969
SP-8018
Spacecraft
Magnetic
SP-8024
Spacecraft
Gravitational
SP-8026
Spacecraft
Star
SP-8027
Spacecraft
Radiation
SP-8028
Entry
SP-8033
Spacecraft
Earth
SP-8034
Spacecraft
Mass Expulsion
SP-8036
Effects
Vehicle
Torques,
Torques,
Trackers,
July
Control,
May 1969
October
November
Horizon
1969
1970
Torques,
of Structural
February
March
1969
1969
Sensors,
December
Torques,
Flexibility
1969
December
1969
Launch
Vehicle
on
Control
Systems,
1970
SP-8047
Spacecraft
Sun Sensors,
SP-8058
Spacecraft
Aerodynamic
SP-8059
Spacecraft 1971
SP-8065
Tubular
SP-8070
Spaceborne
Attitude
June
Torques, Control
Spacecraft
Booms
Digital
1970 January
During
(Extendible,
Computer
Systems,
1971
Thrusting
_ Maneuvers,
Reel
Stored),
March
1971
" _:, February
February
1971
i
SP-8071
Passive
SP-8074
Spacecraft
SP-8078
Spaceborne
Gravity-Gradient Solar
Libration
Cell Arrays,
Electronic
188
May
Imaging
Dampers,
February
1971
Systems,
June
197!
1971
SP-8086
Space
Vehicle
Displays
SP-8096
Space
Vehicle
Gyroscope
SP-8098
Effects of June 1972
SP-8102
Space
CHEMICAL
Design
Structural
Vehicle
Criteria,
Sensor
1972
Applications,
Flexibility
Aceelerometer
March
on
October
Entry
Applications,
Vehicle
1972 Control
December
Systems,
1972
PROPULSION
SP-8087
Liquid
Rocket
Engine
SP-8113
Liquid 1974
Rocket
SP-8107
Turbopump
SP-8109
Liquid
Rocket
SP-8052
Liquid
Rocket
Engine
Turbopump
SP-8110
Liquid
Rocket
Engine
Turbines,
SP-8081
Liquid
Propellant
SP-8048
Liquid
Rocket
SP-8101
Liquid 1972
SP-8100
Liquid
Rocket
Engine
SP-8088
Liquid
Rocket
Metal
SP-8094
Liquid
Rocket
Valve Components,
SP-8097
Liquid
Rocket
Valve
SP-8090
Liquid
Rocket
Actuators
SP-8080
Liquid Rocket Pressure Regulators, Disks, and Explosive Valves, March
Engine
Systems
Rocket
Fluid-Cooled Combustion
for Liquid
Engine
January
Turbopump
Engine
189
Turbopump Tanks
1974 December
1973
1972 March
Shafts
Gears,
and
March
1971 Couplings,
September
1974
Components,
August
May
1974
1973
Assemblies,November and Operators,
November
May 1971
Bearings,
and Tank
1972
1974
March
Turbopump
August
Turbopumps,
Inducers,
April
Devices,
Engines,
Flow
Gas Generators,
Chambers,
Stabilization
Rocket
Centrifugal
Engine
Combustion
.1973 May 1973
Relief 1973
Valves,
Check
Valves,
Burst
SP-8064
SolidPropellant Selection andCharacterization, June1971
SP-8075
SolidPropellantProcessing Factorsin RocketMotorDesign,October 1971
SP-8076
SolidPropellant GrainDesign andInternalBallistics, March1972
SP-8073
SolidPropellant GrainStructuralIntegrityAnalysis, June1973
SP-8039
SolidRocketMotorPerformance AnalysisandPrediction,May1971
SP-8051
SolidRocketMotorIgniters,March1971
SP-8025
SolidRocketMotorMetalCases, April 1970
SP-8041
Captive-Fired Testingof SolidRocketMotors,March1971
190 *U.S.
GOVERNMENT
PRINTING
OFFICE:
1975
-
635-275/53
NASA experience has indicated a need Accordingly, criteria are being developed
for uniform criteria for the design of space in the following areas of technology:
vehicles.
Environment Structures
Individual components are completed. This
of this document,
Guidance
and Control
Chemical
Propulsion
work will be issued as separate monographs as soon as they part of the series on Chemical Propulsion, is one such
monograph. A list of all monographs of this document. These except
monographs as may be
these
documents,
unifqrm This
design
of Howard management
are to be regarded specified in formal revised
practices
monograph,
issued
"Solid
Rocket
W. Douglass, Chief, was by M. Murray
to this one
can be found
on the
as guides to design and not as NASA project specifications. It is expected,
as experience for NASA
prior
may
space
indicate
to be desirable,
final
pages
requirements, however, that
eventually
will provide
vehicles.
Thrust
Vector
Design Bailey.
Control,"
Criteria Office, The monograph
was prepared Lewis was
under
the direction
Research Center; written by Robert
project F. H.
Woodberry and Richard J. Zeamer of Hercules, Inc., and was edited by Russell B. Keller, Jr. of Lewis. To assure technical accuracy of this document, scientists and engineers throughout the technical community participated in interviews, consultations, and critical review of the text.
In
particular,
Thomas
S. Clark
Aircraft Corporation; Lionel H. Erickson of Aerojet Solid Propulsion Company; Center reviewed the monograph in detail. Comments National Office), December
concerning Aeronautics Cleveland, 1974
Ohio
the and
of
United
of Thiokol and James
Technology Chemical J. Pelouch,
Center,
Corporation;Myron Jr. of the Lewis
technical content of this monograph Space Administration, Lewis Research
44135.
Division
will be welcomed Center (Design
of United Morgan Research
by the Criteria
For sale by the National Technical Springfield, Virginia 22161 Price - $7.00
Information
Service
GUIDE
The
purpose
significant programs
of this
is to organize
and
present,
accumulated current design
for effective
that
The
the
of which
are
Art,
design
preceded
by
section
2,
elements
a brief
reviews
introduction
and
are involved
discusses
in successful
use
in design,
the
in development and operational practices, and from them establishes
for achieving greater consistency in design, increased greater efficiency in the design effort. The monograph
major sections references. State
monograph
experience and knowledge to date. It reviews and assesses
firm guidance product, and
identifies
TO THE USE OF THIS MONOGRAPH
reliability is organized
and
complemented
the
total
design.
current technology pertaining to these elements. When detailed best available references are cited. This section serves as a survey background material and prepares a proper technological base Recommended Practices.
design
It describes
in the end into two by
a set
of
problem,
and
succinctly
the
information is required, the of the subject that provides for the Design Criteria and
The Design Criteria, shown in italics in section 3, state clearly and briefly wha.._.__t rule, guide, limitation, or standard must be imposed on each essential_ design element to assure successful design. The Design Criteria can serve effectively as a checklist of rules for the project manager to use in guiding a design or in assessing its adequacy. The
Recommended
Whenever appropriate
Practices,
also
in section
3, state
Design Criteria, successful design.
provide
positive
guidance
to
Both sections have been organized into decimally within similarly numbered subsections correspond the Contents displays design can be followed The design specifications,
how
to satisfy
each
of the
possible, the best procedure is described; when this cannot be done references are provided. The Recommended Practices, in conjunction
this continuity through both
criteria monograph or a design manual.
loosely organized its merit should to the designer.
body of existing be judged on how
the
practicing
designer
on
how
that
a particular
is not intended to be a design handbook, It is a summary and a systematic ordering of the
nl
to achieve
numbered subsections so that the subjects from section to section. The format for
of subject in such a way sections as a discrete subject.
successful effectively
criteria.
concisely, with the
design techniques and it makes that material
practices. available
aspect
of
a set of large and
Its value and to and useful
CONTENTS
Page
.
INTRODUCTION
2.
STATE
3.
DESIGN
1
............................
OF THE
ART
CRITERIA
and Recommended
Practices
Units to SI Units
APPENDIX
A - Conversion
of U. S. Customary
APPENDIX
B - Glossary
............................
REFERENCES NASA
3
........................ ................
161
............
163 173
................................
Space Vehicle
Design
Criteria
Monographs
Issued
to Date
STATE
SUBJECT
185
.............
OF THE
ART
DESIGN
CRITERIA
2.1
18
3.1
117
Configuration Design Optimization Envelope Limitations
2.1.1 2.1.1.1 2.1.1.2
18 21 22
3.1.1 3.1.1.1 3.1.1.2
117 117 118
Design Requirements Actuation Torque
2.1.2 2.1.2.1
22 23
3.1.2 _1.2.1
119
2.1.2.1.1 2.1.2.1.2 2.1.2.1.3
24 26 27
_1.2.1.1 3.1.2.1.2 3.1.2.1.3
2.1.2.1.4 2.1.2.1.5
29 29
3.1.2.1.4 3.1.2.1.5
120 120 121
2.1.2.1.6 2.1.2.1.7
29 30
3.1.2.1.6 3.1.2.1.7
121 121
2.1.2.1.8 2.1.2.2
30 31
3.1.2.1.8 _1.2.2
122 122
2.1.2.3 2.1.2.3.1
33 35
_1.2.3 3.1.2.._1
123 123
2.1.2.4 2.1.2.5 2.1.2.5.1
36 37 37
3.1.2.4 _1.2.5 _1.2.5.1
124 125 125
2.1.2.5.2 2.1.2.6
39 40
_1.2.5.2 3.1.2.6
125
FLEXIBLE
JOINT
Joint Spring Torque Friction Torque Offset Torque Inertial Torque Gravitational Torque Insulating-Boot Torque Internal Aerodynamic Torque External Aerodynamic Torque Nozzle Vector Angle Axial Deflection Nozzle
and Pivot
Misalignment
Frequency Response Environmental Protection Thermal Protection Aging Pressure
Protection Sealing
Point
119 119 120
126
SUBJECT
Material
STATE OF THE ART
Selection
Elastomers Reinforcements Adhesive Bond System Joint Thermal Protection Mechanical General
Design Considerations
Design Definitions Design Safety Factor Flexible-Joint Loads Structural Analysis Elastomer Thickness Reinforcement Thickness Advanced
Analysis
Manufacture Reinforcements Joint Adhesive Flexible Joint
System
Testing Subscale Test Program Bench Test Program Static-Firing Destructive Aging
Program
Inspection Inspection Inspection LIQUID
Plan Processes
INJECTION
CONTROL
Program Testing
THRUST
CRITERIA
2.1.3
40
3.1.3
126
2.1.3.1
41
3.1.3.1
126
2.1.3.2 2.1.3.3 2.1.3.4
42 44 44
3.1.3.2 3.1,3.3 3.1.3.4
129 129 130
2.1.4
45
3.1.4
130
2.1.4.1 2.1.4.1.1 2.1.4.2
45 46 47
3.1.4.1
130
3.1.4.2
131
2.1.4.3
47
3.1.4.3
131
2.1.5
48
3.1.5
132
2.1.5.1 2.1.5.2 2.1.5.3
48 51 54
3.1.5.1 3.1.5.2 3.1.5.3
132 133 133
2.1.6
55
3.1.6
134
2.1.6.1 2.1.6.2 2.1.6.3
55 58 59
3.1.6.1 3.1.6.2 3.1.6.3
134 135 135
2.1.7
62
2.1.7.1 2.1.7.2 2.1.7.3
62 64 67
3.1.7 3.1.7.1
136 136
3.1.7.2 3.1.7.3
137 139
2.1.7.4 2.1.7.5
68 68
3.1.7.4 3.1.7.5
139 140
2.1.8
68
3.1.8
140
2.1.8.1
69
3.1.8.1
140
2.1.8.2
69
3.1.8.2
141
2.2
70
3.2
t42
2.2.1
74
3.2.1
142
2.2.1.1 2.2.1.2
78 79
3.2.1.1 3.2.1.2
142 144
3.2.1.3
146
3.2.1.4 3.2.1.5 3.2.1.6
147 148 150
VECTOR
(LITVC)
System
DESIGN
Design
System Optimization Selection of Injectant Injection Pressures and Injection Orifices Injector Amount
Location and Discharge Angle of Liquid Injectant Required
2.2.1.3 2.2.1.4 2.2.1.5
81 86 87
Amount
of Pressurization
2.2.1.6
89
Gas Required
vi
SUBJECT
STATE
Component Design Injectors Storage Tank and Bladder
OF THE ART
DESIGN
CRITERIA
2.2.2 2.2.2.1
89 90
3.2.2 3.2.2.1
151 152
2.2.2.2 2.2.2.3 2.2.2.4
95 97 99
3.2.2.2 3.2.2.3 3.2.2.4
153 154 155
2.2.2.5
99
3.2.2.5
155
2.2.2.6
99
3.2.2.6
157
Performance Evaluation and Testing Performance Data for Design Small-Scale Tests
2.2.3 2.2.3.1 2.2.3.2
103 104 115
3.2.3 3.2.3.1
158 158
Full-Scale Development Tests Operating-Capability Tests
2.2.3.3 2.2.3.4
115 115
3.2.3.2 3.2.3.3
159 160
3.2.3.4
160
Pressurization System Liquid Storage Equalization Disposal of Surplus Injectant Adaptation of the Motor for LITVC
vii
LIST OF FIGURES
Title
Figure 1
Classification
2
Gimbal/swivel
3
Gimbal/integral
4
Supersonic-splitline
5
Ball-and-socket
6
Rotatable
7
Flexible-joint
8
Fluid-bearing/roiling-seal
9
Liquid
10
Hot-gas
11
Jet tab TVC systems
12
Flexible
of thrust
control
subsonic-splitline
nozzle
nozzle nozzle
canted
injection
joint
...................
14
Graphical
15
Effect
16
Movement
17
Effect
18
Shear-stress
19
Buckling stress and dimensions
joint
12
......................
14
.......................
15
.....................
15
...........................
16
position
......................
position
location point
related
for metal reinforcements of the reinforcement test specimen
in a flexible-joint
envelope
different
(due to motor factors
20
of friction
on required
for three
19
.....................
of the effects
of axial deflection
shear
11 12
leg mounted
presentation
correction
11
13
nozzle
in vectored
of pivot
.................
...........................
TVC system
of pivot-point
nozzle
11
.........................
in neutral
Flexible
4
........................
nozzle
TVC system,
.................
..........................
nozzle
Quadruple-lap
systems
low-subsonic-splitline
13
20
vector
Page
as a function ....................
ix
28 31
nozzles
on nozzle
to cone angle
.....................
......
...............
flexible-joint
pressure)
nozzle
alignment
...............
.........
34 .......
36 49
of the properties 53 63
Figure
Title
Page
21
Specialfixturefor testingjoint axialdeflection ................
65
22
Fixturefor testingjoint actuationunderpressure................
66
23
Schematic of typicalliquidinjectionTVCsystemandsideforcephenomena .....
71
24
Nozzlepressure distributiondueto injectionof inertinjectant
72
25
Nozzlepressure distributiondueto injectionof reactive injectant
73
26
Basicdesignfeatures in a LITVCsystem ...................
75
27
Schematic of TitanIII ullageblowdownLITVCsystem .............
76
28
LITVCsystem for PolarisA3 secondstage
77
29
Crosssectiondrawingof typicalsingle-orifice injector mountedonnozzlewall .........................
84
..........
3O
Crosssectiondrawingof three-orifice injectormountedonnozzlewall
31
CrosssectiondrawingOfanelectromechanical injectantvalve ............
85
32
Injectorvalveassembly withhydraulic-powered actuator
91
33
Servo-controlled hydraulicpowersystems forvariable-orifice injectors .......
92
34
Erosionaroundinjectorportsin theTitanIII nozzle ..............
101
35
Comparison of small-scale andfull-scale dataoninjectantspecific impulsevsdeflectionangleandsideforce ...................
105
.......
84
36
Comparison of performance of inertandreactive injectants ............
106
37
Effectsofinjectionlocationandangleoninjectantspecificimpulse .......
107
38
Effectof injectantflowrateandinjectionpressure onsideforce ..........
39
Effectof injectionlocationandorientationonsideforcefor differentinjectantflowrates ........................
109
40
Transformation of dataoninjectionpressure vsinjectantspecificimpulse ......
110
41
Effectofnumberof annularorificesonsideforceasa functionof injectantflowrate
111
x
108
Figure
Title
42
Transformation of performance
data
43
Correlation
impulse
44
TWo examples
of acceptable
45
Two
of unacceptable
46
of injectant
examples
Sketch illustrating of effective pivot
47
Recommended
48
Values
49
Relation
50
Typical
for strontium
perchlorate
with key nozzle
unbonded-elastomer unbonded-elastomer
sequence
of thrust
of steps impulse
deflection
port
for determining
for reactive angle
configuration
showing
xi
112
........
114 127
..........
128
determination 138 the optimum liquid
location erosion
.......
...........
conditions
and inert
to injector
injectant
parameters
conditions
factors involved in experimental point ..........................
of side specific
LITVC
specific
Page
LITVC
injectants
system ........
.............
and char patterns
design
143 145 149
........
158
LIST OF TABLES
Table
Title
Page
I
Advantages,
Disadvantages,
and Current Status of Movable Nozzle Systems
II
Advantages,
Disadvantages,
and Current Status of Secondary
III
Advantages,
Disadvantages,
and Current Status of Mechanical
IV
Advantages,
Disadvantages,
and Current Status of Special Systems
V VI VII
VIII IX X
XI XlI XIII
Integral Values 103) for/3 = 15 ° to 13= 60 ° Comparative
Effects of Forward
Details of Reinforcements and Development Motors Advantages
Compatibility and Aqueous
........
of Joint Fabrication
Pivot Point
Processes
of Main Operational
Chief Design Features of Variable-Orifice
°°°
9
32
56 ..........
Liquid Injectants
60 .....
80
114-B2 82
of Liquid Storage Systems on Operational
Xlll
8
10
.........
Injectors on Operational
for Inert and Reactive Injectants
6
25
of Selected Metals and Nonmetals with Freon Strontium Perchlorate ....................
Side Force Composition
Systems
..................
and Aft Geometric
and Characteristics
Chief Design Features
Deflector
Systems
Used in Flexible Joints on Operational ........................
and Disadvantages
Basic Properties
Injection
.....
LITVC Systems LITVC Systems
............
93 96 103
ROCKET
SOLID THRUST
VECTOR
CONTROL
1. INTRODUCTION Most the
vehicles required
used flight
for launching trajectory
spacecraft
require
will be achieved.
for flight disturbances (e.g., thrust and center of gravity).
winds) and To provide
equipped with a thrust vector control have been used to redirect the motor
some
guidance
In addition,
or steering
steering
to ensure
is needed
that
to compensate
for vehicle imperfections (e.g., misalignment this steering, solid propellant rocket vehicles
system. thrust
Both mechanical and provide the
and aerodynamic required steering
of are
techniques forces. This
monograph is limited to treatment of thrust vector control systems that superimpose a side force on the motor thrust, steering being achieved by the side force causing a moment about the vehicle center of gravity. A brief review of thrust vector control systems is presented, and two systems, flexible joint and liquid injection, are treated were selected because they are in use on a number of operational likely to be used in future depends upon the particular reliability, development system different from within the restrictions presented
to allow
Treatment
of the
flexible
joint
and
These two systems and they are most
vehicles. The choice between these two systems performance requirements, system weights, cost,
risk, and envelope constraints. However, it i_ possible that a control the selected systems could result in an optimum vehicle performance imposed for particular types of missions. Sufficient references are
investigation flexible-joint its
aerospace vehicle
in detail. vehicles
in detail thrust
insulation
of control vector
against
hot
systems
control motor
other
system gases;
no
than
the
is limited
two
to the
evaluation
the injectant distribution The
design
and within
erosion at the the nozzle.
technology
for
the
injection
two
selected
port
injectant, of the and
systems
design
is presented
movable nozzle, the actuation system, or the means for attachment of the the movable nozzle and the fixed structure. Treatment of the liquid-injection control system is limited to discussion of the pressurization system; no evaluation is presented
selected. of the of the
flexible joint to thrust vector
valves, piping, storage tanks, and nozzle except for (1) the effect of
(2)
the
effect
has
progressed
of injection
to the
point
on
pressure
where
the
basic problems have been overcome and efficient and reliable systems can be designed for any required use. Design problems with flexible joints have been associated with difficulty in establishing the envelope for the movable nozzle; definition of the actuator power
requirements to vector the movable nozzle; definition of allowable properties for the elastomerand the reinforcement; adhesivebonding of the elastomerto the reinforcements; test methodsthat adequatelysimulate the motor operating conditions; and quality control inspection of the molded joint. Design problems in liquid injection systemshave been associatedwith definition of the maximum steering-forceduty cycle; determination of the optimum location and geometry of the injector Valves;andincompatibility of the injectant with many of the materials used for the nozzle walls, seals,and injectant pressurization system. Emphasis in the monograph is placed on those areaswhere specific technical approacheshavesolveddesignanddevelopmentproblems. The material herein is organized around the major tasks in thrust vector control: configuration as related to motor requirements;designparameterscontrolling the response of the mechanism; material selection; system design; structural and thermal analysis; manufacturing; testing, both nondestructiveanddestructive;and inspection.Thesetasksare consideredin the order and manner in which the designermust handle them. Within these task areas, the critical aspects of the performance, structural, thermal, and physical boundary requirementsthat the thrust vector control systemmust satisfy arepresented.
2. STATE OF THE ART
The
vehicle
flight-control
system
must
perform
two
functions:
fly
the
vehicle
along
a
commanded trajectory, and maintain vehicle flight stability in the atmosphere. Vehicles without aerodynamic stabilizing fins normally are unstable, and those with fins may be only marginally stable. Disturbances that effect vehicle attitude and stability include atmospheric winds; motor thrust misalignments due to fabrication tolerances and thrust-vectorcontrol-system offsets such of gravity; and unbalanced disturbances requirements,
be
corrected structural
as those forces with loads,
that occur with flexible joints; during launch and staging. It proper and
timing and aerodynamic
requirements are a function of interrrelated and the vehicle aerodynamic and structural requirements and the design of the control the development of a space vehicle system.
amplitude heating
shifts of vehicle center is desirable that these
so are
that control minimized.
energy Control
effects of disturbances, the trajectory required, dynamics. The determination of flight-control system are two of the most complex problems in
The control system causes a side force to be applied to the vehicle at some distance from the vehicle center of gravity, resulting in a control moment and a change in the vehicle attiude. A number
of force-producing
mechanisms
have
been
employed
or considered
as means
provide attitude and trajectory control of aerospace vehicles. The available considered in this monograph are divided into two main groups: movable-nozzle and fixed-nozzle systems. A classification of the different force-producing associated used, and
with movable and fixed nozzles is shown still others have been evaluated to determine
used include aerodynamic movable 15), and
jet reaction fins (refs.
pintles electric
(refs. 1 to 6), movable external rocket 10 and 1 1). Preliminary evaluations
(refs. 1, 12, 13, and 14), movable arc discharge (ref. 16).
The correct definition and design of the requiring tradeoff analyses between control system as they relate to vehicle performance. vector
control
response, and the systems;
system
are
the
control
plug
(ref.
systems systems, systems have have
motors (refs. 7 to 9), have been conducted 2),
electro
gas dynamic
been been and on (ref.
flight-control system is a complex problem requirements and the penalties of the control Factors affecting the selection of a thrust
moment
required,
the
characteristics
of
vehicle
the stability requirements during flight, reliability requirements, cost restrictions, behavior of the candidate systems. Movable-nozzle systems are linear response i.e., the turning moment is almost directly proportional to the amount of nozzle
vectoring, although directly proportional. rate
in figure 1. Other sytems feasibility. Systems that
to
of injectant
the power required to cause that amount of nozzle vectoring may not be Fixed-nozzle systems generally are nonlinear systems; i.e., twice the
flow
in a liquid
injection
system
does
not
cause
twice
the turning
moment.
TVC
Fixed
J
' Liquid
i
Mechanical
Special systems
deflectors
__J
I
Gas injection
--Jet
I Movable
I
injection l
injection
I
I nozzle i
I Secondary
systems
nozzle
!
I
Low subsonic
High subsonic
_A
I Supersonic
--_Flexible
vane
_____J
-_mbal
joint i
--Flexible --Rotatable
Movable
-Jetevator
L--Hinged
joint --Fluid
bearing/
rolling _Inert liquid
i
I
Warm
gas
--Jet
Pintle --Gimbal
L--Movable
tab
--Fluid
bearing/
plug rolling _Reactive liquid
.-Hot
"Jet
seal
probe --Hinged
--Gimbal
gas _Segmented nozzle
--Ball
&
socket
--Hinged
Figure
1. - Classification
of
thrust
vector
control
systems.
seal
Thrust in the
vector control mechanisms past have been outmoded
have been undergoinging continual by increased severity of operational
development of lighter, more reliable status of the systems listed in figure features of major systems are shown
systems. The general characteristics and technology 1 are presented in tables I through IV; basic design in figures 2 through 11. The systems summarized in
tables I to IV can be divided into three categories: (1) systems systems that have been tested in static firings, and (3) experimental been abandoned or require significant development. Movable rotatable
nozzles.The movable-nozzle systems nozzle and flexible joint) or have been
splitline,
gimbal/integral
change. Concepts used requirements and by
low-subsonic
splitline,
that are systems
(table I) either static fired (e.g.,
supersonic
splitline,
would cause of the vehicle
(2) have
are operational (e.g., gimbal/swivel subsonic and
ball and
of the systems have demonstrated problems or limitations. All movable require that the actuation hardware for the staging maneuvers be carried remainder of the flight. The rotatable nozzle is limited to multinozzle movement of only one nozzle vehicle; effective maneuvering
operational, that either
socket).
All
nozzle systems throughout the motors because
pitch, yaw, and roll forces to be applied to the requires movement of at least two nozzles. The
supersonic splitline and ball-and-socket type are not developed systems, and it is unlikely that further development will be conducted since the other movable nozzle systems have demonstrated all the advantages of these nozzles but with fewer operational and design problems. The
fluid
fluid-filled deflection
bearing/rolling
seal
bearing configured of the rocket motor
deflected as both
(designated
as
TECHROLL
®)
is
a
constant-volume,
with a pair of rolling convolutes that permit omniaxis nozzle. The bearing is shown in figure 8 in the neutral and
positions. The fluid-filled bearing is pressurized by nozzle ejection loads the movable nozzle bearing and nozzle seal. The seal is fabricated
fabric-reinforced
elastomeric
composite
manufacturing processes or tight tolerances. that the actuation torques are lower than
material The those
that
does
not
and serves from a
require
complex
most significant advantage of this bearing is of any other thrust vector control system.
The most significant disadvantages of the bearing are that it has a low rotational stiffness about the nozzle axis in the unpressurized condition, the pivot-point location is limited, and the low lateral stiffness results in larger offset torques than those occurring with a flexible joint.
The
rotational
stiffness
is important
for upper
stages
only
when
vibrational
problems
could occur during lower-stage motor operation. To overcome the limits on pivot-point location, it has been proposed that the rolling convolutes be oriented on a cone; however, this design will increase the actuation torque. The larger offset torque must be allowed for when defining nozzle vectoring angle has been bench tested and static fired joint (ref. 35), thus allowing a direct ®Trademark
of United
* Parenthetical conversion monograph.
units
factors
Technologies
here
and elsewhere
appears
in Appendix
(formerly in the A.
For
requirements. A 24-in. (60.96 cm)*-diameter bearing in a large rocket motor that normally uses a flexible performance comparison of the two systems. The
United
Aircraft
monograph simplicity
Corporation).
are in the International and
brevity,
SI units
System are
not
of Units presented
(SI units). in the
A table
tables
of
in the
TABLE I. - Advantages, Disndvantal|es, and Current Status of Movable Nozzle System
System
Advantages
Flexible joint (refs. 17-30)
State of the art Flexible duty cycle
(fig. 7)
No splitlines Large deflection capability Flexible pivot point location Negligible thrust loss Minimum seal problem Can be used for deeply submerged nozzle Fast response capability Lightweight
Status of Technology
Disadvantages
Operational system for Poseidon C3 first and second stage.
Joint requires thermal protection Joint requires vrotection
of
elastomer during storage Only small tension loads can be applied to joint Joint pivot point is floating, dependent on motor pressure and vector angle Nozzle aligned only at one design pressure and misaligned at all other
(refs. 31 and 32) (fig. 6)
System static fired to 15° vector angle at 355 deg/sec and 300 psi. One static firing, 13-in. and 34-in. throat, submerged nozzles. Three static firings, 2.3-in., 2.6-in., and 8 in. throat. angle at 428 deg/sec and 300 psi.
State of the art
Limited to multiport
Flexible duty cycle Low bearing loadings
Large bearing required Movement of a nozzle results
motors
Operational system for Polaris A2 second stage and Polaris A3 first stage.
in pitch, yaw, and roll forces Nozzle rotation angle much larger than jet deflection
Fluid bearing/
State of the art
Bearing requires thermal
rolling seal
Flexible duty cycle
(refs. 33-36)
No splitlines Large deflection capability
protection Low rotational
(fig.8)
Army Re-entry Measurements Program Phase B; throat diameter approximately 2.8 in., + 8 ° deflection.
System bench tested to 15° vector
pressures
Rotatable nozzle
Twelve successful flight tests on
Negligible thrust loss Minimum seal problem Can be used for deeply submerged or supersonic splitline nozzles Fast response capability Lightweight Minimum envelope required
angle
stiffness about
nozzle axis in unpressurized condition Bearing pivot point is floating, dependent on motor pressure and vector angle
Flightweight systems for Trident 1 (C4) first-, second-, and third-stage motors demonstrated in static firings. Static firings, 4-in. and 10-in. throat, submerged nozzles. Two static firings, 2.44n. and 8.5-in. throat.
Nozzle aligned only at one design pressure and misaligned at all other pressures
Low spring torque (continUed)
/
TABLE I. - Advantages, Dissdvantalles , sad Currant Status of Menmble Noz_
System
Gimbal/swivel subsonic splitline (refs. 37 and 38) (fig. 2)
Advantages
Disadvantages
State of the art Flexible duty cycle Negligible thrust loss Large deflection capability Low-to-medium blowout load Low entry erosion
Excessive envelope required for submerged nozzle High erosion and heat flux in splitline Limited operation time Inflexible pivot-point locations
Systems (oaududed)
Status of Tedmology
Operational system for Minuteman i and 1I first and third stages and Minuteman 111 tint stage. One fullscale firing, 38-in. throat, single external-gimbal nozzle. Two subsonic firings, 15-in. throat, single external-glmbal nozzle. One firing, 4.71 -in. throat, single externalglmbal nozzle.
Gimbal/integral low subsonic splitline (refs. 37-40)
(t_g.3)
State of the art
High blowout
Minimum splitline erosion and heat flux
High actuation torque Large volume required within chamber
Minimum seal problem Continuity of entry, throat, and exit cone Flexible duty cycle Negligible thrust loss Large deflection capability Long burn time durability
load
Medium entry erosion Inflexible pivot-point location Potentially large vectoring envelopes
One firing, 24-in. throat, single submerged nozzle. Two firings, i 5-in. throat, nozzle.
single submerged
One firing, 9.2-in. throat, single submerged nozzle. One firing, 3.9-in. throat, single submerged nozzle. Two f'uings, 1.75-in. throat, single submerged nozzle" +-14 °, 235 sec operation, 163 sec actual firing, 20 pulses, 72 sec coast time.
Supersonic splitline (refs. 41-44) (fig. 4)
Attractive for submerged nozzle
Sealing and erosion problems at splitline
Low entry erosion Lightweight potential Fast response capability Low blowout load
High actuation torque Limited to small vector angles
size: one successful, one failure, single nozzle one-plane motion. Several firings, 4.9-in. throat
High coulomb torque Unpredictable friction torque
One firing, 9.6-in. throat, single submerged nozzle.
Sealing problem Antirotation device required High axial thrust loss
Development
Small deflection Ball and socket (ref. 45)
(fig.5)
envelope
Potentially lightweight Small envelope requirement Large deflection capability Flexible pivot-point location Deflection
Two firings of Minuteman motor, first-stage
of the seal region
is minimized and seal gap is maintained by uniformly distributed load
Notes: Throat dimension in column 4 is throat diamct_. Factors for converting U_. customary units to SI ualts are presented h_ Append_ A.
flexible joint.
discontinued
in favor of
TABLE I1. - Advantages, Disadvantages, and Current Status of Seeondmy In_
Liquid injection (refs. 46-51) (fig. 9)
Disadvantages
Advantages
System
Systems
Status ofTechnology
State of the art
Limited thrust deflection
Operational system for Polaris A3 second
Liquid injection thrust adds to motor thrust
System weight is high Careful attention must be given
little
to selection of liquid and bladder
stage;Minuteman III second and third stages; 120-in. motor for Titan IIIC and IIID; Sprint first- and second-stage motors; Hibex motor; and Lance motor.
prelaunch
checkout
required Fast response capability
material for long-term storage A long hold period after the system is energized requires replenishment of the liquid and pressurization devices Lack of flexibility for accommodation
Development static firings on 120-in. Titan IIIM motor, 156-in. motor, and 260-in. motor.
of changes in control
requirements Must be designed for worst-onworst requirements
oo
Gaseous injection (refs. 52-62)
(fig. lO)
Little prelaunch
check out
required Fast response capability Lighter in weight than liquid injection
systems
Should be linfited to applications
Demonstration
static firing on 156-in. motor.
with required thrust deflection
Demonstration Demonstration
static firing on 1204n. motor. static firings of Minuteman
angles less than 7° Cannot be used where precise velocity control is required Hot-gas valve is subjected to severe thermal environment Warm-gas valve requires large and heavy gas generators Additional propellant necessary to recover thrust losses
Note: Dimensiongiven in column 4 is motor diameter.
motor, first-stage size. Problems concerning durability
of materials
for valves and pintles need to be solved.
•
TABLE !II. - Advantages, Disadvantages, and Current Status ofMechanical Deflector Systems
System Jetvane (refs. 10,63, and 64)
Advantages Actuation torques are low Small installation envelope around nozzle Power requirements are low, and thus actuator weights are low Fast response capability
Jetevator
Side force is linear with
(refs. 65-69)
jetevator deflection angle
Disadvantages
Status of Technology
High thrust losses Restricted to motors with lowtemperature propellant short burn time
or
Operational system for Sergeant, Talos, and Pershing and for Algo !I and 111 motors. No current development.
Large vane rotation angle required for small jet thrust deflection Jetevator envelopes nozzle exit, restricting maximum available nozzle exit diameter
Operational system for Polaris AI first and second stages and Polaris A2 first stage.
Restricted to motors with low-
Operational system for BOMARC and SUBROC.
temperature propellant short burn time
or
No current development.
Heat shields required to protect afterdome, nozzle exterior, and actuation system significantly increase total system envelope
',D
Large thrust loss (half of generated side force) Torque varies with time System is relatively heavy Limited to multiport systems for omniaxis vectoring. Jet tab
Side force is directly
Restricted to motors with low-
(refs. 70-74) (fig, 11)
proportional to ratio of tab area to nozzle area
temperature propellant burn time.
or short
Caused significant local erosion in the nozzle
Limited to development static firings. Test results indicate significant design and material problems. No current development.
Large thrust loss (equal to generated side force) Jet tabs at the exit plane increase envelope requirements Segmented
nozzle
(refs. 12 and 58)
Major portion of nozzle is fixed to motor Thrust losses at small deflection negligible.
angles are
(Testing to date insufficient to determine disadvantages of system)
Limited to experimental static firings. No current development.
Table IV. - Advantages, Disadvantages, and Current Status of Special Systems
i
System Movable pintle (refs. 1 and 12-14)
Advantages Can be used as a throttling device
Side forceis nonlinear
Omniaxial movement is
Plug subjected to severe thermal environment
C_
Movable plug (ref. 2)
Status of Technology
Disadvantages
possible
with
pintle cant angle Small pintle cant angles produce negative side forces Pintle subjected to severe thermal environment
Analytical and experimental development only. No current development.
Limited to cold-flow air tests. No current development.
Fixed
structure Subsonic
splitline
\
Figure
Low
Fixed
_
structure
Figure
2. - Gimbal/swivel
subsonic
subsonic-splitline
Movable
nozzle
Movable
nozzle
nozzle.
splitline
_ Gimbal 3. - Gimbal/integral
Iow-subsonic-splitline
nozzle.
I Fixed
structure Supersonic
splitline Movable
Gimbal
Figure
4. - Supersonic-splitline
]1
nozzle.
nozzle
ovab le nozzle
Ba 1 i/socket
Antirotation
Figure
5. - Ball-and-socket
Rolling
bellows
nozzle.
bearing Bolted
joint
table nozzle
Seal
Figure
6. - Rotatable
12
canted
nozzle.
Bellows
insulating
boot
_eomet_ic
£orward
pivot
poi
_ctuator
Flexible joint Radiation
/
shield
X
/
I
] Elas
Reinforcement
boot
I
ttOmer
_, ,,
_
_
insulating
bracket
\
nozzle
Wrap-around
_
]
Fixed
_y_
_"
Aft
/
geometric
_pivot
point
I
I (a)
Flexible
joints
with
insulating
boot
Reinforcement
E la s tome
/
r
Ablative
protection
Fixed
Movable
'_Aft
attach
r±ng_
\_
attach
structure
nozzle
ring
i Aft
geometric
pivot
J (b)
Flexible
joint
with
sacrificial
Figure 7. - Flexible-joint
13
ablative
nozzle.
t
protector.
point
_---
1
'_
_l_u_: one
Falbric_reinforced
neoprene
bladder
Pivot
-
point (a)
Neutral
position
Extended
side
.Vector
angle
,ressed ide_
(b)
Figure
Vectored
position
8. - Fluid-bearing/rolling-seal
14
nozzle.
Act
us for
bracket
Actuator
Exit
_lild
cone
tank_ valve (a)
External
(b)
Submerged
Figure
9. - Liquid
nozzle
nozzle
injection
Gas
TVC
system.
injectant
I
Hot-gas
valve
Motor
Figure
10. - Hot-gas
TVC
]5
system,
leg mounted.
_
._ XIE cone
xit
Exit
(b)
Submerged
Figure
11.
cone
cone
nozzle
- Jet
tab
16
TVC
systems.
comparison showed that the actuation percent of the actuation torque for the (60.96 cm) diameter have been tested vectoring 35
rates
and
36).
vector
up to 40 An
angles
demonstrated
The
(20.32
and
2) of for for
or
flexible
pressures
rates
bearing up
up has
to 1000 been
to 140 deg/sec
tested
and
for
an
operational
flight
motor
MN/m 2) (refs.
in static
motor
and
firings
pressures
up to
up to 2700
therefore
will
not
be
in this monograph.
joint
has
demonstrated
the
capabilities
of the
gimbal
development problems, has been demonstrated in a number operational in the first- and second-stage motors for Poseidon treated in detail in this monograph (secs. 2.1 and 3.1).
Liquid (table
psig (6.89
for firing times of 20 seconds (ref. 35). This bearing has also been tested + 15 °, vectoring rate of 762 deg/sec, and motor pressure of 2100 psia a firing time of 5.5 seconds (ref. 35). The fluid bearing/rolling seal has use in a large high-performance motor, but as yet has not been
accepted
further
motor
cm)-diameter
of + 12 ° at vectoring
psia (18.6 MN/m at vector angles (14.5 MN/m 2) been selected evaluated
8-in.
deg/sec,
torque for the fluid bearing/rolling seal was 30 flexible joint. Fluid bearing/rolling seals up to 24-in. in static firings up to vector angles of -+ 6.5 °, at
injection.II) has been
A large amount accumulated. The
of experience liquid-injection
splitline
but
with
fewer
of flight motors, and C3; therefore, this joint
on secondary-injection system is a state-of-the-art
is is
TVC systems system that
is operational on several vehicles. This system has the advantage over the movable-nozzle system in that most of the excess liquid can be dumped after staging and recovery of flight attitude, the vehicle thereby having less inert weight during the remainder of the flight than the vehicle that must continue to carry nozzle actuation hardware. Hot-gas injection systems are promising, but valve and piping problems due to the severe thermal be solved. Warm-gas injection systems reduce the thermal environment large
and
heavy
this monograph
Mechanical
gas generators. (secs,
systems.-
The
2.2 and
The
liquid-injection
system
therefore
is treated
in detail
listed
table
either
mechanical
are no longer being considered weights and material problems now
plug under
(table
IV) have
not
in
3.2).
deflector
systems
on
operational (e.g., jet vane and jetevator) but have now been replaced were limited to development static firings (e.g., jet tab and segmented
and
environment need to problem but require
in the industry. These techniques due to exposure to hot exhaust advanced
beyond
development.
17
limited
experimental
III
were
by other systems, or nozzle) and in general
generally suffer from high gases. The movable pintle evaluation
and
are not
2.1
The
FLEXIBLE
flexible
movable
joint
nozzle
JOINT
is a nonrigid that
direction*. The deflection moment about the vehicle Two
kinds
of flexible
position in figure descriptive terms definitions appears
2.1.1
pressure-tight
allows
the
nozzle
joints
are
shown
of the
a movable any
in figure
by
the
rocket
as much
as
motor 15 ° in
and
a
a given
the motor thrust vector and generates altering the course of the vehicle. 7. The
flexible
joint
13. These complete
is shown
a
in a neutral
figures also show list of symbols
the and
Configuration rings of an elastomeric These rings are usually
flexible
nozzle. direction.
elastomeric part of the
Since When
components total vector
material spherical
alternating with rings of sections with a common
to as the geometric pivot point. A joint wherein the rings were sections has been designed and successfully tested (ref. 22). This of requiring a single set of tooling for all the rings rather than
tooling for each ring as is necessary the joint was limited to a cylindrical
in
between
deflected
12 and in a vectored position in figure used throughout this monograph. A in Appendix B.
center of radius referred identically shaped conical design had the advantage
end
connection be
of the nozzle deflects center of gravity, thereby
The flexible joint consists of metallic or composite material.
One
to
joint the the
with spherical envelope.
is connected joint
rings.
to a fixed
is symmetrical
nozzle
are strained angle, and
is acted
Since
each
ring had
and
the other
structure,
about upon
its centerline, by
an
the
same
is connected
the nozzle
external
shape,
actuator
to
can vector force,
the
in shear, each reinforcement ring rotates a proportional the nozzle rotates about the effective pivot point (fig.
13). Usually the effective pivot point does not coincide with because of different amounts of distortion in each reinforcement.
the
geometric Omniaxis
pivot point movement of
the nozzle is obtained by using two actuators 90 ° apart. In addition to providing a means for thrust vectoring, the joint also acts as a pressure seal. Flexible joints are designed so that the axial compressive pressure imposed on the elastomer is higher than the chamber pressure. An important property of the elastomer in the operation compressive modulus is approximately 15 000 times the shear
* This
amount
of
motion
has
been
demonstrated,
but
an upper
limit
to deflection
of a joint is that the bulk modulus. This relation means
angle
has
not
been
established.
18 '\
Ro + Pivot
radius
Geometric
pivot
point,common center for Joint
joint angle
_1
Outer
joint
as tomer Reinforc
Figure
12. - Flexible
joint
]9
all
angle "oint
Inner
Ri
Rp =
in neutral
position.
ement
angle
radii
Deflected
joint
Original
joint
Geometric
Vector
angle
@
envelope
pivot
point
point Effective
I,
/----
Joint
0
U
Deflected
joint
0
0
__.._ .-
Rotation \
jl
Figure
about
13. - Flexible
joint
20
effective
in vectored
occurs pivot
position.
point
pivot
that a joint but permits
can transmit high axial compressive high shear deflections at low applied
The reinforcements to motor pressure
cylinder
The
nozzle
with
section,
the
movable
flexible joint. fixed structure
DESIGN
Flexible-joint reinforcement materials
when
an actuator a
actuation is discussed
design
protection.
These
motor
requirements
design
previous
;_,applied ai>plied geometry apart each
of
structure,
four the
main
subsystems:
actuation
system,
pressure,
(ref.
is dependent
incremental analysis increment
when
the
joint to the in reference
joint
and
actuator
not
in the plane cross section
be
must
be selected
the number layers, and
of the
combined
to
and
angle,
and
envelope
constraints
must be determined in studies joint design requirements and
are specified. to define the stage
the and
77).
on many
geometric
variables,
and
no general
solution
for joint
is based on empirical relationships (refs. 17, 23, 78, and by finite-element techniques (refs. 80, 81, and 82), and to the analytical results. Analysis of a flexible joint is of and joint
procedure is conducted, and
elements
vector
material properties, large deflections and strains, nonsymmetric geometries during vectoring. However, test results and calculated results has been obtained by (ref. 80). The using material
a geometry
determined
load is axisymmetric, the deflected load is asymmetric (e.g., an actuation will
joint
the and the
performance, and reliability at minimum weight and Joint design is affected also by the attachment to the nozzle. In some programs, the basic joint design
these design requirements relationship between the
complicated by nonlinearity nonsymmetric loading systems, reasonable correlation between
the
consists fixed
system on the flexible in this monograph.
design exists. Preliminary design 79). A selected design is analyzed the design is modified according
use of an finite-element
and axial loads due sideways as would
consists of the determination of the joint configuration, the material for the reinforcement rings and elastomeric
including programs, tradeoff
joint
deflections,
OPTIMIZATION
design rings,
requirements
The
axial
was applied.
joint to the
provide the required spring stiffness, within cost and envelope limitations. fixed structure and the movable
vehicle
load
flexible
attachment
for environmental
In other optimum
resulting
The movable-nozzle section and the attachment of the flexible are treated in reference 75, and actuation systems are treated
76. The effect of the characteristics interact
2.1.1.1
low
provide rigidity to the joint against motor pressure and constrain the joint to vector instead of deflecting
an all-elastomer
movable-nozzle
loads with torques.
axisymmetric.
of actuation have is axisymmetric
from
the
previous
increment.
geometry will be axisymmetric. load applied by one actuator),
The
deflected
been (refs.
analyzed 22 and
21
load is applied incrementally, properties associated with the
geometries
at two
cross
and a stress at When
the
the •
When the deflected
sections
180 °
by finite-element methods that assume 78). Methods of mathematical analyses
other
than
the
finite
material
anisotropy
2.1.1.2
ENVELOPE
The
joint
element (refs.
envelope
have
been
employed
to consider
(fig.
angle/32 /32-55 The
12) nor
difference
minimum
value
deformations
and
LIMITATIONS is defined
by the
less than
pivot
0 °. It has
up to 70 ° are feasible; °- may
joint
83 and 84).
radius
Rp,
the inner
/32, and the cone angle _b (fig. 12). The pivot radius is throat diameter, but the inner and outer joint angles designer. All joints that have been successfully tested to 40 ° to 45 °, angle t32 ranging from 45 ° to 55 °, and angle angle/3
finite
not be the
limit.
between
the
possible
without
these
inner
been
and
suggest
outer
exceeding
joint
the
outer
joint
angles
131 and
determined primarily by the nozzle and cone angle are selected by the date have had angle/31 ranging from ¢ that was not greater than the joint
demonstrated
results
and
by
that
analysis
the largest
angles
allowable
that
joints
demonstrated
with value
for
at
the
(/32 -/31 ) is maintained
elastomer
stresses,
so that
an
the joint
spring torque is kept to a minimum. It has been shown analytically (ref. 17) that the cone angle significantly affects the joint axial deflection and the elastomer and reinforcement stresses. As the cone angle increases, these values increase, and the effective pivot point moves farther from the geometric pivot point (fig. 13). However, decreasing the cone angle has resulted in nozzles with large section of the nozzle and require the
amount
Cost
also
with
has been
cylindrical
2.1.2
that increase the weight of the movable envelopes in the motor, thereby reducing
of propellant.
conical-shaped
section,
re-entry sections larger clearance
envelope thus
reducing
a factor
in determining
reinforcements
was
(_b =/3 as shown tooling
and
the joint
The must
A large The
on fig. 13), and each
fabrication
joint
flexible was
reinforcement
joint
designed had
the
(ref.
22)
with same
a
cross
costs.
Design Requirements
The requirements affecting the design of a flexible angle, axial deflection, frequency response, motor sealing,
envelope.
manufactured.
cost,
actuation
joint are nozzle actuation torque, vector pressure, environmental effects, pressure
and weight. torque
be estimated
(sec. for
2.1.2.1),
preliminary
is made design
up of many and
subsequently
vector angle (sec. 2.1.2.2) required to produce sufficient dependent on the position of the pivot point (fig. requirements.
Axial
deflection
(sec.
2.1.2.3)
affects
22
contributing
the
torques,
checked
in static
each
of which
firings.
The
maneuvering force on the vehicle 13) and the vehicle performance clearance
envelope
required
between
is
the fixed and movable portions of the nozzle; in addition, the axial deflection controls the axial spring stiffness of the flexible joint between the fixed and movable nozzle sections. The natural frequency and frequency responseof the movablesection(sec.2.1.2.4) depend upon the axial stiffness and the massproperties of the movable section. The frequency responseaffects designof the actuator andguidancecontrol system;sufficient stiffnessmust be designedinto the movablenozzleto avoid dynamic coupling of variousforcing functions. The motor pressure influences the selection of the joint materials and dimensions and affects the joint responseto all of the aforementioneddesignrequirements.The joint needs to be protected against a high-temperature environment on the motor side and the atmospheric environment on the outside (sec. 2.1.2.5). In addition, the joint must be a pressuresealbetweenthe motor andthe atmosphere(sec.2.1.2.6). Flexible joints with elastomericringsformulated from natural rubber havebeen operatedat elastomer temperatures ranging from 65° F (291 K) to 85 ° F (302 K), and have been vectored
in motors
operating
up to 600
not less than 65 ° F (291 acceptable results in bench (ref. 85).
2.1.2.1
ACTUATION
In order accordance
(182
required. The actuation torque total torque is the summation
including torques due to internal the following component torques: •
Joint
•
Frictional
•
Offset
•
Inertial
•
are
spring
and
external
torque torque
torque torque
Gravitational
identified
900
m) altitude
with
the
elastomer
at
has demonstrated K) to 165 ° F (347 K)
TORQUE
to define the requirements of the control with the motor or vehicle requirements,
actuation torque pivot point. The
Materials
000 feet
K). A joint with neoprene*/polybutadiene tests at temperatures from -40 ° F (233
torque
in Appendix
B.
23
system and to actuate the the designer must know usually is defined of a number of
aerodynamics.
The
total
about the contributing torque
nozzle in the total geometric torques,
is made
up of
• Insulating boot torque • Internal aerodynamictorque o The
External
total
aerodynamic
actuation
torque
torque
varies
from
motor
to motor
and
from
cycle
to cycle
continuous sinusoidal cycling on the been determined to be -+ 20% (refs.
nozzle. The total variability 86 and 87). The variability
including of a new
determined,
be
not_ identical
since
prior
results
may
based
on joints
that
are
during
both items has design must be to
the
new
design. 2.1.2.1.1 The
Joint Spring Torque
flexible-joint
spring
torque
(resistance
of
maximum torque contributing to the actuation factors: total thickness of elastomer, pivot radius, affected '2.1.2.5.2).
by
environmental The resistance
• convenience
of analysis,
geometric
pivot
point
the
joint
necessary
torque
to the line of action
The spring torque is dependent on the combined on the thickness of each ring (ref. 17). The spring of the pivot radius (i.e., Tq _ Rp 3 are a minimum, the joint diameter
mechanical is overcome
is calculated
of the
movement)
torque. It is dependent joint angles, and motor
effects on the elastomer of the joint to movement the
to
as the
usually
on a number of pressure; it is also
characteristics by the actuator; moment
arm
(sec. for
from
the
actuator. thickness of all the elastomer torque is roughly proportional
rings and not to the cube
Therefore, to ensure that the spring torque is minimized by placing the joint as close
).
is the
and envelope to the throat
plane as possible; the pivot radius is then made as small as possible, but not so small as to increase the stresses in the joint above the allowable values. The inner and outer joint angles /31 and/32 (fig. 12) control the joint thickness. is kept to a minimum consistent with the
As noted, elastomer
the difference between allowable stresses. The
these joint
angles spring
torque reduces attributed to
as the motor pressure increases the effect of compression on
(refs. 13, 22, 86, and 87). This phenomenon the elastomer shear modulus properties,
configuration
of
in shape
the
joint,
and
the
change
of
the
joint
(refs.
83
and
is the
84).
If
sufficient pressure is applied, the spring torque can become zero. Little data are available on the variation in spring torque. Tests conducted on joints for two different motors that used a natural-rubber formulation show a variation of + 20% at zero pressure. This torque variation in absolute units remained approximately constant and independent of motor pressure modulus For
rapid
(refs. 86 and 87). The variation of the elastomer (sec. 2.1.3.1 ). calculation
number of equations correlation with test
of the have results
Spring
was correlated
torque
for joints
with
with
lot-to-lot
spherical
variation
reinforcement
in the shear
rings,
a
been developed (refs. 17, 21, 23, and 78). Of these, the best for many different joints is the expression (adptd. from ref. 78)
24
_
Tq 0
12Goroari ro 3_
ri 3
(1)
3 [I(fl2)-I(fl,)]
where = joint
Tq
spring
0 = vector Go
torque,
angle,
= elastomer
in. - lbf (m-N)
radians
secant
shear
modulus
at 50 psi (0.345
MN/m 2)
shear
stress (sec. 2.1.7.1), with no externally imposed pressure, at the elastomer temperatures expected in operation, psi (N/m 2) ro
= Rp
+ nte/2,
in. (cm)
q
= Rp
-
in. (cm)
Rp t_ n
_, _
nte/2,
= pivot
radius
= thickness
of individual
= number = inner
of elastomer and
I(f3) = integral
in. (cm)
outer
values
TABLE
V.
elastomer
in. (cm)
rings
joint
angles,
listed
in table
-
layer,
deg V (ref.
78)
Integral Values 103) for/3 = 15 ° to/3 = 60 ° (ref. 78)
fl, deg
10)
/3, deg
15
0.0518
27
16
.0588
28
.1713
40
.3249
52
.4999
17
.0661
29
.1828
41
.3389
53
.5148
18
.0739
30
.1946
42
.3531
54
.5298
43
.3674
55
.5448
/3, deg 39
0.1601
t_) 0.3110
/3, deg 51
I Wig) 0.4849
19
.0820
31
.2067
20
.0906
32
.2189
44
.3818
56
.5599
21
.0995
33
.2315
45
.3963
57
.5749
22
.1088
34
.2442
46
.4109
58
.5899
23
.1184
35
.2572
47
.4256
59
.6048
24
.1283
36
.2704
48
A403
60
.6198
25
.1386
37
.2838
49
.4551
26
.1492
38
.2973
50
.4700
25
From
test
data,
the
following
pressure has been natural-rubber-formulation
empirical
developed elastomers
Tq
relationship
for (adptd.
0.156Gro
0
--
calculating
joints with from ref. 78):
3 ri 3 (/32 -
ro 3
for
steel
the
spring
torque
reinforcements
/31)
at and
(2)
ri 3
where G
= effective
elastomer
pressure, = Go A
shear
modulus
when
subjected
to external
psi (N/m 2 )
+ Ao 2
= constant
(3)
depending
= - 0.2595
upon
reinforcement
material
x 10 -6 for steel Pc sin2/32
O2
(sin2/32
Pc
from
joints
with
equation
cone
Friction bearings friction
torque in and O-rings. theoretically major
cos 2 q_
psi (N/m 2)
deg
angles
(2) have
Friction
three
pressure, angle,
2.1.2.1.2
from
- sin2/31)
= motor
q_ = cone
For
(4)
=
agreed
varying within
from
15 ° to 50 ° , at high
+ 8% with
torques
measured
pressure, in bench
torques
calculated
tests.
Torque a conventional movable nozzle arises from sliding surfaces Since there are no sliding surfaces in a flexible-joint nozzle, does not exist. Elimination of the joint friction eliminates
sources:
26
such as coulomb problems
(1) Friction varies significantly from unit to unit and cannot be predicted with accuracy. (2) Friction is the major sourceof steady-stateerror in the servoactuator system. (3) The changefrom static to sliding friction causesa breakawaypeakin actuation. Although there is no sliding friction in a flexible joint, the joint doesrespondto actuation in a manner similar to that of a spring-masssystemwith both viscousfriction and coulomb friction. The viscousfriction probably is associatedwith the viscoelasticbehavior of soft elastomeric materials. Viscous damping is an important consideration in determining the stability characteristicsof the thrust vector control system. No methods are availableto calculate either coulomb friction or viscous friction. Attempts to calculate the damping coefficient from the decaying actuator force transient occurring at the end of a step vector-angle function applied to a nozzle have been unsuccessfulbecauseno correlation could be obtained with the friction coefficient calculated from actuation data. For sinusoidal actuation of the nozzle, the viscoustorque component doesnot contribute to the maximum actuation torque, sincethe viscousfriction torque is a maximum when the nozzle is at zero position andzero when the nozzle is fully vectored. The coulomb friction and viscous friction are determined experimentally. A nozzle is vectored at different frequencies but constant amplitude, and the actuator force is measured.A typical actuator force responseis shown on figure 14(a); the actuator force at zero vector angle is the total friction. When the variation in total friction force with vectoring rate is plotted as shown in figure 14(b), the two friction components can be determined. Experimental data have shown that for joints fabricated by the samemanufacturer the variation in viscous friction is -+30% and for coulomb friction is -+15%(ref. 88). Joints fabricated by different manufacturers to the same specifications have demonstrated significantly different friction torque results,although the variability wasapproximately the same. Test results have indicated that the viscous friction is dependent on vectoring amplitude in addition to vectoring rate. The coulomb friction has been shown to be dependent on vectoring amplitude and pressure.The phenomenon of friction is little understood, and the elastomerproperties anddimensionsinfluencing friction havenot been identified. 2.1.2.1.3
Offset Torque
Offset torque manufacturing during additive
is the torque tolerances.
resulting from Consequently,
motor firings. The offset torque to that due to nozzle vectoring°
asymmetry in the nozzle offset torque can occur
due to misalignment and in bench tests as well as
during a motor firing is an aerodynamic torque The amount of alignment offset is dependent on
27
t Total
frequency
friction
+ Vector
Total
--
Response
friction
to
slnusoldal
different Highest
(a)
angle
actuation
at
frequencies
frequency
Variation
in
vector
angle
with
sinusoidal
actuation
force
O 4J U v_4
Rate-dependent
component
(viscous
friction)
! 4J O
Rate-independent
Maximum
(b)
Figure
14.
Variation vectoring
- Graphical
vectoring
in total rate
presentation
component
friction
of
the
28
effects
(Coulomb
friction)
rate
with
of
maximum
friction
sinusoldal
in a flexible-joint
nozzle.
axial deflection characteristics be at zero vector angle (sec. diameter has been small determining the actuation torque
could
2.1.2.1.4
of the joint 2.1.2.3). The
contribution
to the
actuation
torque is determined the movable section
by assuming of the nozzle
of the vector
the
actuation
it is ignored in joints the offset
torque.
joint acts with the angles at zero motor
spring
torque
cycles,
and
even
produced The inertial
less
to a fixed structure, and in the determination movable nozzle it is usually assumed that half
movable pressure,
at high
is much
point resulting from accelerations on the vectoring acceleration.
that the mass of the nozzle acts at the center of gravity of and that the movable section vectors about the geometric
pivot point. One end of the joint is connected of section mass and center of gravity of the
with
at which the nozzle must up to 22-in. (55.88 cm)
Torque
The inertial torque is the torque about the pivot on the nozzle by the actuator and is dependent
the mass maximum
pressure for joints
in comparison with the spring torque, and torque. However, it is possible that for larger
be a significant
Inertial
and the motor offset torque
section. For joints the inertial torque
vectoring
than
the
rates
up
variability
to
designed to demonstrate usually is small compared
500
in actuation
deg/sec
for
torque
from
sinusoidal motor
to
motor. 2.1.2.1.5
Gravitational
The gravitational movable nozzle maneuvers,
Torque
torque is the torque produced mass as a result of accelerations
pitch,
yaw,
and
axial
gravity, causing axial and lateral As before in the determination assumed usually
to act with is small
with
2.1.2.1.6
Insulating-Boot
A flexible
joint
7).
Either
separates The
this
often
wrap-around
a wrap-around a 13-in. (33
and boot
section. the
accelerations
booster
is protected boot
against
hot
is wrapped
motor
1255
center
vehicles,
of
nozzle. mass is
the gravitational
directly
gases by use of an insulating
torque
around
the
joint,
or
boot
a dead
air
(fig. space
the boot. adds
significantly
to the
nozzle
boot fabricated of silica-filled butadiene cm)-diameter joint increased the actuation
DC
vehicle
torque.
m-N/deg) to 2100 in.-lbf/deg (237 m-N/deg) changed to a bellows type (fig. 7), the actuation 1600 in.-lbf/deg (180 m-N/deg) (ref. 14). incorporating
at the
at the center of gravity of the movable and center of gravity, half of the joint
For large
spring
occur
by the vehicle
Torque
insulating
the joint
lateral
accelerations of net mass
the movable
compared
and
about the geometric pivot point imposed by the vehicle. As the
silicone
rubber
resulted
29
vectoring
torque.
For
acrylonitrile rubber torque from 1000
example,
use of
(GTR V-45) on in.-lbf/deg (113
(ref. 13). When the design of the boot was torque increased from 1000 in.-lbf/deg to A wrap-around boot design (fig. 7(a)) in a 20%
increase
in actuation
torque
for a
joint 22 in. (55.88 cm) in diameter. This was
found
to be
i_ct_ase 'was ratio of joint
dependent
on
increase was not uniform from joint to joint the boot was bonded to the reinforcements:
whether
greater when the boot was diameter to insulating boot
bonded thickness
to the reinforcements. In general, as the increases, the proportionate increase in
actuation attributable percent.
torque due to the boot will be less. to the insulating boot for a joint 112
2.1.2.1.7
Internal
.... _ '"_Th_ :internal
Aerodynamic
aerodynamic
For example, the increase in torque in. (2.84 m) in diameter was 11 to 15
Torque
torque
acting
on a submerged
nozzle
is the
result
of unsymmetric
flow between the around the vectored
propellant grain and the movable nozzle. Pressure nozzle cause side forces and a resultant torque.
variations
If the
pivot
is forward
torque
torque
and
point hence
and the
of the
is an increment
nozzle
to the
throat,
actuation
the
aerodyl_amic
torque
and
needs
that
occur
is a restoring
to be calculated.
If the
pivot point is aft of the nozzle throat, the aerodynamic torque is sustaining and reduces the actuation torque (ref. 23). For an aft pivot point, the aerodynamic torque usually is ignored in calculating the actuation torque, thus ensuring a conservative estimate for actuation torque.
However,
if a system
were
designed
to be vectored
only
at pressures
that
result
in a
low spring torque, the aerodynamic spring torque and produce a negative tolerated in a closed-loop system.
torque with an aft pivot point could actuation torque. A negative actuation
The aerodynamic torque is calculated point produced by the pressure forces knowledge of the wall static pressure
by summing the moments about the geometric pivot acting on the nozzle wall. This procedure requires a and the pressure differentials existing in the nozzle.
Two procedures are available airflow simulation tests (ref.
for developing the internal 89), and a two-dimensional
overcome the torque can be
wall pressure in a vectored method-of-characteristics
nozzle: solution
(ref. 90). When the aerodynamic torque is calculated from the results of a_rflow simulation tests, the calculated value generally is within + 20% of the measured value. When the aerodynamic torque is calculated from the results of a two-dimensional method-of-characteristics analysis, the result generally is within + 50% of measured value. As the grain burns and the clearances between the nozzle and the distribution becomes more symmetrical, so that the aerodynamic significance near the end of propellant burn. 2.1.2.1.8
External
Aerodynamic
In
specific
cases,
pressure of little
Torque
During flight, the external air stream impinges on the component, especially in the high dynamic pressure required.
grain increase, the torque becomes
this
effect
perhaps
30
nozzle region could
exit cone and creates a torque when large vector angles are be
utilized
to
increase
the
maneuverability of the vehicle in this flight region or to provide vehicle control after motor burnout. The external aerodynamictorque could be calculated from the pressureacting on the nozzle exterior surface in the same manner as the internal aerodynamic torque is calculated(sec.2.1.2.1.2). However, in most boosterapplications, the exit coneis shrouded by a motor caseskirt that preventssignificant air impingementthat would causean external aerodynamictorque. 2.1.2.2 The
NOZZLE
amount
the
nozzle
The
pivot
VECTOR
of nozzle
vector
is vectored, point
Vectored
can
nozzle,
Vectored
nozzle,
ANGLE
the be
pivot
PIVOT
side or aft
force of the
by the vehicle acts
aft
control
approximately
nozzle
throat
(fig.
requirements.
through
the pivot
15).The
position
/
pivot
Envelope
for
forward
pivot
point
point
for
forward
pivot
point
Envelope
1
,._
_SS
_ aft point _
| _J
Nozzle
in
neutral
position Forward
pivot
point Aft
Figure
point. of the
pivot
for
Envelope
When
point
/ Envelope
POINT
is determined
resultant
forward
forward
aft
angle
AND
15. - Effect
of pivot-point
pivot
position
31
point
on required
envelope.
pivot
for
geometric
pivot
point
is selected
from
a tradeoff
on the exterior clearance envelope between the and stroke to fulfill vehicle guidance requirements, movable
nozzle
presented
in table
A summary
of the
comparative
study
that
considers
the
effect
of position
fixed and movable parts, the actuator force and the spatial envelope available for the effects
of a forward
or aft pivot
point
is
VI.
TABLE VI. - Comparative Effects of Forward and Aft Geometric Pivot Point Comlmmtive effect Item
Reduced
Increased
Clearance envelope for exit cone
Increased
Reduced
Actuator stroke to produce a particular vector angle
Increased
Reduced
Actuator force to produce a particular vector angle
Reduced
Increased
Vector angle to produce a particular vehicle movement
Increased
Reduced
pivot point less envelope
will reduce the moment arm to the vehicle center angle to generate the necessary turning moment.
will reduce the required vectoring angle. A forward for movement of the nozzle nose cap region but more
exit cone (fig. 15). The moment arm from the forward pivot point, and therefore less actuator cone movement is increased, the actuator stroke Because
of the
recluced
nose-cap
movement,
(fig. 15). Regardless of whether tested to date has been between
pivot
points
generally
is greater with a because the exit
are
used
for
the motor chamber. Aft pivot points generally because the envelope for exit cone movement movement reduces the envelope available for
a forward or aft pivot 45 ° and 50 °.
32
of gravity Similarly,
pivot point will envelope for the
pivot point to the actuator force is required; however, is increased. forward
nozzles having little or no submergence into are used for nozzles having deep submergence, is critical. However, the increased nose-cap propellant t3 on joints
Aft pivot
Clearance envelope in nose cone region
As shown, a forward pivot point and thus require a large vectoring an aft require
Forward pivot
is selected,
the joint
angle
The position of the effective pivot point is dependent upon the applied loads and joint configuration. The actuator force, in addition to vectoring the joint, causes a movement of the joint in the radial and axial direction, so that the effective pivot point is offset from the geometric differently,
pivot point (fig. 13). Vectoring of the joint causes strongly influencing the position of the effective
each reinforcement to deflect pivot point. At zero motor
pressure, only the actuator force causes pivot point movement. At motor pressure, compressive load is applied to the joint and causes additional pivot point movement. 16 shows the measured pivot point movement for three different joints varying inches (53.3 cm) and at maximum by decreasing reinforcement reinforcement
diameter expected
to 112 inches (2.84 operating pressure.
an axial Figure from 21
m) diameter, vectored at zero motor pressure The pivot point movement can be decreased
the cone angle. Analytical studies (ref. 17) have indicated that the stresses decrease as the cone angle decreases (sec. 2.1.5.3), because the deflection decreases. Reduced reinforcement deflection results in reduced
pivot point movement. As shown in figure 16, pressure lateral movement of the pivot point due to vectoring. A knowledge
of the
effective-pivot-point
location
acting
on the joint
is important
also reduces
in establishing
the
the
clearance
envelope between the fixed and movable nozzle components. In one flexible-joint program, the effective pivot point was assumed to have moved an amount equal to the axial deflection, and a clearance envelope was set up accordingly. It was subsequently determined that the effective pivot point had moved approximately 1.5 in. (3.81 cm) while joint axial deflection was 0.4 in. (1.02 cm). The allowed clearance envelope was too small and had to be increased
by removing
predicts the lateral pivot-point position
2.1.2.3
AXIAL
Although
the
joint.
No
method
has
been
An approximate in the following
developed method section.
that
accurately
to determine
flexible
joint
stiff
in compression
in comparison
amount of axial compression occurs when the axial compression to determine nozzle
spring
acts to increases
is relatively
stiffness,
reduce some the vectoring
and
the
nozzle
clearances clearance
misalignment
between around
with
its vectoring
the motor is pressurized. envelope requirements, requirements.
axial the
properties envelope,
compression cone angle. in and
is dependent The axial
on the elastomer stiffness, the reinforcement compression involves an interaction among
compression, deformation the ratio of the dimensions
of the of the
33
The
It the axial
the fixed and movable nozzle the exit cone, and influences the
position of the pivot point. The spring stiffness is required in the design of the control system. The fixed-length actuator causes vectoring of the nozzle by motor and the nozzle is misaligned at zero pressure so that it is aligned at some required The and
the
DEFLECTION
compressive
compression components,
of the
movement of the pivot point. due to axial load is presented
stiffness, a measurable is necessary to know axial
part
elastomer, elastomer
guidance pressure, pressure. stiffness, elastomer
reinforcement stiffness, rings to the reinforcement
joint rings.
Force Joint
description
system
geometric
st
pivot
eosition
of
with
respect
point
effective to
pivot
(a) Mean
Joint
diameter
m
112
53
radius angle
m 73 50 °
-
in.
motor
pressure
Geometric
(1.85
000
lbf(2.358
x
105
pivot
point
N)
m) Aft
Vector
angle
point
in.
(2.84 m) Pivot Cone
Zero
pivot
geometric
6
ffi 2 °
in.
(£5.24
cm)
+ .I x (5.76
106 x
--_
in.-Ibf 105 m-N)
_Axial position is reference
Effective pivot point
plane
5-1/2 (b)
At
motor
pressure 3.97
49
000
Ibf
(2.180
1.15
x
x
105
10 6
(5.115
x
+---_
Ibf
10 8
cm)
N) Geometric N)
pivot
I-I/2 point Effective--
4.8 _*_----_/(5.42
x
1061n.-Ibf x 105 m-N) Joint
cm)
1
pivot
point
axial
deflectiou
pressure
in.
_---T(3,8i
Aft----Im_
ffi0.24
st
in.
(6.10
mm)
Geometric Mean
Joint
(53.3 Pivot Cone Vector
diameter
=
21
(a)
ih.
Zero
cm) radius angle angle
motor
1770 ffi 13.90
in.
(35.3
pressure
15f(7873
N)
I
in.
point
___/plvot
ca> $/__/
Aft
cm)
0.5
ffi 50 ° = 5°
1480
Ibf_(6583
+----.. 6327
At
(b)
:(1.27
iolhf
m-N)
t^ft...
Effective
pivot
210 000 ibf (9.341
x
105
N)_
835
N)
Aft_
ibf(3714
32 000 m_...._/(3615
point
2-1/4 _---
Ibfi(4448
om)
_
pressure
motor
I000
in.
N)
_
Aft
(5.71in. cm)
N)
.
0.02
Geometric pivot _Int
in.
(0.5
*mu)
ff tlve pivotS--- t
in.-ibf m-N)
point
Joint
axial
at
ffi0.4 pivot
Effective Zero
motor
1130
Ibf
(a) Mean
Joint
(53.7 Pivot Cone Vector
diameter
-
21.14
angle
_ 13.70 50.5 ° -
in.
(I.02
pressure
In.(34.80
(5026
N)
_
I
3100
ibf(13789
Aft
T
cm) 0.14
N)
5°
in.
(3.6
ram)
,%___t 000 (5197
in.-ibf m-N)
pivot
Geometric
Effective (b)
At
motor 785
Ii0
000
lbf
point
pivot
pressure
Ibf(3491
N)
(5.08
cm)
_ [
point
0.02 2160
lbf
(9608
in.
N)
I
(0.5 (4.893
x
i0
N)_
32
000
in.-ibf
(3615
m-N)
of pivot
point
for
34
three
point
mm)
| Aft-Jm_
at
16. - Movement
pivot
Geometric
Joint
Figure
ca)
point
in.
cm)
radius angle =
deflection
pressure
different
axial
pressure
flexible-joint
deflection -
O.3
in.
(7.6
nozzles.
_n)
Test
results
have
shown
compressive
loads
The
conditions
loading
compression
load
that
(refs.
these
22, 86, and for
due
interactions
in a nonlinear
response
to applied
axial
87).
a flexible
to the
result
joint
motor
consist
pressure
of an external
acting
on
the
radial
movable
The axial compression load due to motor pressure is calculated acting on the movable section. Solutions in the form of
pressure section
and
an axial
of the
by integrating equations to
nozzle.
the pressures predict axial
compression have not been satisfactory. Measured deflections have been as much as four times the calculated deflection. Most success in predicting axial compression has been obtained with computerized finite-element methods of analysis (refs. 78, 81, and 82). Reasonable correlations between calculated and measured axial deflections have been made with
the
use
of a sequential-loading
finite-element
method.
The
geometry
of the
joint
for
each loading increment is changed to the deflected geometry due to previous loading increments. For each loading increment, the elastomer shear modulus is assumed constant at the secant shear modulus at 50 psi (0.345 MN/m 2 ) shear stress (sec. 2. i .7.1), and all other elastomer ratio
properties
are
determined
assuming
isotropy
and incompressibility
(i.e., Poisson's
= 0.5).
An approximate estimate loaded by motor pressure point for each reinforcement.
of the position of the effective pivot point when the joint is is made by considering the movement of the geometric pivot When loaded by motor pressure, each reinforcement rotates
but undergoes negligible change point for each reinforcement amount, and the effective pivot
in cross-sectional shape. Consequently, the geometric pivot can be defined. Each reinforcement rotates a different point is approximately at a mean of all the geometric pivot
points.
2.1.2.3.1 Axial
Nozzle
deflection
attachment
points
Misalignment causes are
a
vectoring
a fixed
the guidance system begins the motor pressure increases.
misalignment
distance
apart,
of
as in the
the
nozzle.
case just
after
When booster
the
actuator
launch
to control the vehicle, the nozzle is not free to translate An actuator length that holds the movable components would be too short at operating the actuators were retracted (fig.
before aft as aligned
to the fixed components The nozzle at pressure
at zero motor pressure would vector as though
alignment condition
of the exit than in the
cone to the fixed components is less important in an unpressurized pressurized condition, the actuator length at zero pressure is set
minimize pressurized
the angle condition.
between the movable and the At zero pressure, this actuator
vectored as though the misalignment decreases.
actuators
were
extended.
35
pressure. 17). Since to
fixed components at some nominally length is too great, and the nozzle is As
the
motor
pressure
increases,
the
._Fixed-length
Nozzle position pressure
at
zero _/-
! ..__..I"
_41_
actuator
[ !_
i _ !. _
Axial displacement actuator brac_t
/__'--Misallgnment
!
of
an, le
, l-i'll
duetoaxi°l
...... Effective
pivot
point
"'-.
Nozzle after
position axial
"''--.
deflection"'--...j
Figure 17. - Effect of axial deflection (due to motor pressure)on nozzle alignment.
The actuator bracket (fig. 7(a)) usually is connected to the motor case; hence the actuator bracket deflects as the motor is pressurized. The effect of actuator-bracket deflection has to be
included
in determining
misalignment.
If the
actuator
bracket
is connected
to the
aft
adapter of a glass-filament-wound motor case, the misalignment due to act,6-ator bracket deflection is much larger than that due to axial deflection of the joint. This difference arises because the rotation of the aft adapter can be as much as 3 ° at maximum expected operating
2.1.2A
pressure
MEOP.
FREQUENCY
The_ movable nozzle -_ructure forms an
RESPONSE section additional
and the spring
frequency of the control system natural mode of nozzle oscillation, occurred
where
the
hydraulic
flexible in the
system. The fixed If a strong natural
applied through the actuators is near the frequency the nozzle oscillations will be reinforced. An instance
actuator
stiffness
36
/
joint form a spring-mass guidance control system.
was
low
enough
to be the primary
of a has
stiffness
determining
the
nozzle
natural
frequency.
All of the nozzle
subsystems
are designed
to have
enough stiffness so that their individual natural frequencies are high when compared with the driving frequencies transmitted through the control system. Preliminary estimates of the stiffness of each subsystem can be made, but mathematical models of the nozzle and actuation frequency
system are difficult to build without response, closed-loop damping, and
development
2.1.2.5
test data. open-loop
Consequently, damping are
tests to determine conducted early in a
program.
ENVIRONMENTAL
PROTECTION
Flexible joints are protected against exposure to hot motor atmospheres that could cause rapid aging of the elastomer. been demonstrated on a natural-rubber formulation (ref.
gases, warm atmospheres, The effect of temperature 91), the results showing
and has that
increasing temperature decreases the shear modulus, the allowable stresses and strains, and the strength of the bonds to the reinforcement. Atmospheric aging of specimens of natural-rubber formulations show increased shear modulus and reduced allowable stresses and
strains
aging
(ref,
(refs.
Limited
92).
93 and
studies
Other
studies
have
shown
that
silicone
rubber
is much
less sensitive
to
94).
(ref.
85)
with
laboratory
specimens
have
been
conducted
(1) neoprene, (2) neoprene/polybutadiene, (3) ethylene propylene butyl, and (5) silicone, for use in joints over a temperature range 165 ° F (347 K). The results showed that for all formulations (1) affected from -40 ° F (233 K) to 70 ° F (294 K) and decreases up to tensile elongation is neoprene/polybutadiene increases with decreasing
a maximum and silicone temperature,
K). The secant neoprene/polybutadiene
modulus at is little affected
shear
at 70 ° F (294 formulations showed and (2) shear elongation 50 from
psi (0.345 70 ° F (294
on formulations
of
terpolymer (EPDM), (4) from -40 ° F (233 K) to tensile strength is little 165 ° F (347 K), and (2)
K). Shear studies of the that (1) the shear strength is a maximum at 70 ° F (294 MN/m 2) shear stress K) to 165 ° F (347 K)
for but
increases significantly at -40 ° F (233 K), whereas the silicone formulation is little affected from -40 ° F (233 K) to 165 ° F (347 K). The neoprene/polybutadiene formulation was bench tested in a joint at -40 ° F (233 K), 70 ° F (294 K), and 165 ° F (347 K); the results showed torque
that (1) axial did not change
compression increased with increasing temperature, (2)the actuation from 20 ° F (266 K) to 120 ° F (322 K), and (3) with the value at 70 °
F (294 K) as a reference, the actuation torque decreased 18 percent at 165 ° F (347 K). 2.1.2.5.1 In most
Thermal cases,
the
increased
18 percent '_
at -40 ° F (233 K) and _ _ _ .... _
Protection flexible
joint
is protected
by controlling the atmosphere surrounding conducted with the joint at temperatures
against
exposure
the joint prior from 65 ° F (291
37
to warm
or cold
atmospheres
to firing. Most joint testing is K) to 85 ° F (302 K). Limited
bench testing has been conducted on joints at conditions from -40° (347 The
K) (ref. joint
F (233
K) to 165 ° F
85).
is protected
from
hot motor
gases either
by use of an insulating
boot
(fig. 7(a)),
by use of sacrificial ablative protectors (fig. 7(b)). As noted earlier, either the boot has been wrapped directly around the joint or a dead air space has separated and the boot. The wrap-around boot provides less heat-transfer barrier for thickness, boot and
because the joint.
there For
is no dead air space to act as an additional insulation the bellows-type designs, pressure relief holes through
required to balance the pressure across the boot. The vent holes allow the gas pressure to equalize during high rates of change ignition, the
so that
tearing
wrap-around
Both been
boot
is prevented.
the insulating and whether
boot requires decisions to expose the boot to the
from the high-temperature a radiation shield mounted
the exposed used. Motor
boot,
the
torque is greater more envelope.
requires
more
envelope
than
whether chamber
to use a wrap-around environment of radiant
required than
that
heating between
or a heat
char and erosion temperature, and
behavior velocity.
rubber. The boot and fixed sections
95 and 96) have material for the
as a function of strain in When a radiation shield is
and radiation shield are designed (fig. 7(a)) occurs in a stagnant around the such design,
and using a silicone rubber boot, showed only slight charring the boot needed to be thick enough to withstand only the gap between the boot and the protection shield. For the insulating of the
The sacrificial ablative protectors sufficient to provide a heat-transfer To minimize that the gap
to at
when the joint is actuated and the shape of the annular cavity is altered, there is little circumferential flow in the annulus. One
22 in. (55.88 cm) in diameter with no erosion. Consequently, radiant heating through the exposed
need to be sufficient of pressure occurring
boot (refs. 13, 14, and 23) and the protected boot (refs. designs using an exposed boot require an ablative plastic
the boot material is a silicone the gap between the movable
region. Even circumference
design
the are
motor gas stream or to minimize this heating by on either the fixed or movable nozzle components.
boot,making it necessary to know the addition to gas composition, pressure, provided, so that
This
between the boot
design.
The design of bellows design, transfer providing
of the
or
insulating the joint the same
material protected
extend barrier
is stiffer, boot.
outboard between
and
However,
thus the
the
increase
protected
in actuation boot
requires
of the elastomer rings a distance the hot motor gases and the elastomer.
in the cavity between protectors, the protectors is less than the elastomer
protectors thickness
are cross sectioned (fig. 7(b)). The
so gap
between protectors must be wide enough to prevent contact during vectoring or motor pressurization. Because there is a possible path from the hot motor gases to the elastomer, it is necessary environment
to determine the environment to the char and erosion
accumulation in the gaps anomalies in the vectoring
in the region characteristics
of the protectors of the protector
and
to relate material.
this Slag
after static firing has been noted, but this buildup did not cause response of the nozzle during firing. This result was attributed to
38
the lack of adherencebetween the slagandthe carbon-fiber/phenolic--resincompositeused for the protectors. The sacrificial ablative protector doesnot causean increasein actuation torque and requireslessenvelopethan the insulating boot with a radiation shield. All thermal protection designshave been tested successfully:the exposedinsulating boot with and without bellows (refs. 13 and 14), the protected insulating boot with and without bellows (refs. 23, 95, and 96), andthe sacrificial ablativeprotectors (ref. 25). Selectionof a design is made from a study evaluating such factors as gas characteristics(temperature, composition), gas flow (velocity, stagnation regions, pressure), envelope requirements, actuation power source, and overall system weight (actuation system, joint, insulating system)in relation to performancefactors (e.g.,range,payload, and reliability) and cost. 2.1.2.5.2 Tests
of
Aging Protection flexible
joints
using
a natural-rubber
surfaces protected from the environment changes, axial compression is reduced, change has been attributed to continued
formulation
(GTR
44125)
with
the
rubber
have demonstrated that, with aging, performance and spring torque is increased. The performance reaction of the components of the elastomer. The
spring torque increased by approximately remained constant thereafter (ref. 26).
six percent The joints
per year for 31/2 years in this program were
(ref. 97) and stored in an
atmosphere at 80 ° F (300 K) and where joints have been stored for data to be available. Similar results
approximately 50% humidity. This is the only program a sufficiently long period and in sufficient quantity for have been obtained in quadruple-lap shear and uniaxial
tensile testing 110 ° F (317
same rubber formulation; humidity for 9 months
modulus
from
of specimens K) and 90% 24 psi (0.165
The decrease in affects the nozzle nominally
of the relative
MN/m 2 ) to 30 psi (0.207
axial deflection misalignment
selected
operating
pressure
changes in joint performance made. The future performance probable
joint
life (ref.
that accompanies (sec. 2.1.2.3), since are
to
some
monitored, is compared
however, accelerated resulted in an increase
MN/m 2 ) (ref.
22).
increased spring it will change the
misalignment and projections with the motor
aging at in shear
at that
torque due to aging zero alignment at the pressure.
Currently,
of future performance are requirements to evaluate
26).
Elastomers less susceptible shear modulus and shear
to aging strength
are under development, make it difficult to
but the rigorous requirements of develop a satisfactory elastomer.
Further, the long time periods necessary to evaluate an elastomer make it difficult to assess property degradation with age for a new elastomer formulation. Accelerated aging tests at high relative humidity have indicated possible degrees of aging that have subsequently been found to be Silicone-rubber
more severe formulations
than are
aging under less susceptible
normal service to aging but
conditions (ref. 22). have a shear modulus
approximately 50% greater than that of natural-rubber formulations and a shear stress at failure approximately 50% less than natural-rubber formulations; in addition, silicones are more difficult to bond to metals.
39
A possibleadditional problem that hasbeen consideredis surface
by
either
ozone
possible exposed chlorobutyl rubber The
elastomer
showed
Such
elastomer or Hypalon
surfaces rubber.
uncured
condition
in the
a decrease
or oxygen.
in the
shear
oxidation are
coated
with
is susceptible
modulus
of
oxidation of the elastomer at its been prevented by ensuring that all
has
an
impervious
to aging.
Cured
rubber
material
A natural-rubber
of
1 psi (6895
such
as
formulation N/m 2) for
each
month of age of the uncured rubber stored at 40 ° F (278 K). The elastomer in this formulation was manufactured to as high a shear modulus as the specification allows so that if the shear modulus of the cured rubber decreased because of aging of the stored uncured rubber the formulation would for six months at 40 ° F (278
remain K) and
within if after
was
rubber
was
within
rubber
specification
the
specification. The" uncured storage the shear modulus
used,
but
if outside
rubber was stored of the cured rubber
of specification
limits
the
was rejected.
2.1.2.6 If the
PRESSURE axial
flexible
SEALING
compressive
joint
assures
that
force
due
the
joint
to motor
pressure
will seal against
is sufficiently leakage
without
high,
the geometry
the need
for any
of a special
precautions. The dimensions of the movable nozzle and joint are such that a compressive axial load is applied to the joint, the result being a compressive stress in the flexible joint that is greater than the motor pressure. Consequently, small unbonded spots and voids are tolerated. When joints are manufactured by injection molding or compression molding (sec. 2.1.6.3), unbonding cannot be detected. each
bond
line
assembled. the amount
2.1.3
can be controlled only on a sample basis, because unbonded areas For joints that are manufactured by secondary bonding (sec. 2.1.6.3),
can be inspected
for unbonding
Material
elastomer, insulating material for a given
boot, and use depends
that
seeks
techniques
as the joint
is no quantitative
to optimize
its environmental bonding system
protection, between
is being
definition
materials need the reinforcement
protection from the external atmosphere. on the motor operating requirements (e.g.,
vector angle), the environmental propellant gas velocity, atmospheric these variables in turn is evaluated cost
there
of
Selection
For fabrication of a flexible joint and selected for the elastomer, reinforcement,
and
by ultrasonic
Regardless of the manufacturing method, of unbonding that will result in a leak.
operating conditions ozone content), in a tradeoff study
vehicle
and motor
4O
The motor
to be and
choice of pressure,
(e.g., propellant gas temperature, and the envelope available. Each of involving range, payload, reliability,
performance.
2.1.3.1 The
ELASTOMERS
important
reproducibility the selected
properties
in the
elastomer
selection
are
the
shear
modulus,
shear
stress,
of these properties from lot to lot, and the ease of bonding the elastomer to reinforcement material. Since it has been demonstrated that the joint spring
torque could become zero because of axial compression, efforts determine shear properties with superimposed compression (ref. 78).
are
being
made
to
The joint spring torque is directly proportional to the elastomer shear modulus (sec. 2.1.2.1.1). In the selection of an elastomeric material, the aim is to use an elastomer with as low a shear modulus as possible and with a minimum of continued feaction of the components have been
(sec. 2.1.2.5.2), developed with
which secant
will increase shear moduli
shear modulus. (sec. 2.1.7.1)
Natural-rubber ranging from
formulations 20 psi (0.138
MN/m 2) to 35 psi (0.241 MN/m 2) at 50 psi (0.345 MN/m 2) shear stress. The low required shear modulus has presented difficulties to the elastomer formulators in preparing formulations that fulfilled the chemical stability requirement. The
shear
pressure specified
stress
in the
elastomer
is caused
by vectoring
and
usually is the more significant. Successful joints quadruple-lap shear stress (sec. 2.1.7.1) of
the requirements of shear modulus and shear stress, most joints have been of natural rubber or polyisoprene formulations. The joints of both stages of the motors are natural-rubber formulations, either GTR 44125 or TR 3005 (refs. 98
and
The
the 260-in.
all failures
(6.604
were
motor
To meet fabricated Poseidon
for
and
Of these,
having a minimum MN/m 2) have been
manufactured,
joint
tested,
pressure.
designed,
99).
and
motor
using elastomers 500 psi (3.45
m) motor
cohesive.
(ref.
22)
and
a joint
designedto
operate
at 3000 psi (20.7 MN/m 2) to + 15 ° at 300 deg/sec (ref. 14) used GTR 44125 elastomer. Required properties for these elastomers are minimum shear stress of 500 psi (3.45 MN/m 2) and secant shear modulus (at 50 psi (0.345 MN/m 2) shear stress) of 22 psi (0.152 MN/m 2) to
26
psi
(0.179
MN/m 2)
for
GTR
44125
and
18.5
psi (0.128
MN/m 2) to 24
psi (0.166
MN/m 2) for TR 3005. Actual shear strengths for these elastomers are greater than 1000 psi (6.9 MN/m 2 ) (ref. 100) for GTR 44125 and 660 psi (4.55 MN/m 2 ) for TR 3005, all failures being cohesive. m) motor (ref. motor (ref. 18). those of the
Polyisoprene elastomers have been used for the joints of the 156-in. (3.962 23), the 100-in. (2.54 m) motor (ref. 19), and an advanced dual-chamber The polyisoprene elastomers demonstrate shear properties that are equal to natural-rubber formulations but the shear modulus is greater, being
approximately used for joints
27 psi (0.186 MN/m 2) minimum. Natural-rubber when the minimum expected operating temperature
(283 process than
K). Because controls 10 psi (0.070
of the
difficulty
are maintained MN/m
A neoprene/polybutadiene between -40 ° F (233
in making to ensure
an elastomer
a lot-to-lot
with
variation
formulations have been was not less than 50 ° F a low shear
in shear
modulus,
modulus
close
not greater
2 ).
formulation has been bench tested K) and 165 ° F (347 K) at an equivalent
41
jJ
in a joint designed to operate motor pressure of 2550 psi
(17.6 MN/m 2) to + 17.5 ° at 360 deg/sec (ref. 85). Required secant shear modulus (at 50 psi (0.345 MN/m z) shear stress)
properties of the rubber were a of not more than 50 psi (0.345
MN/m 2 ) when the shear strength was greater than 600 psi (4.14 MN/m 2 ), and a secant shear modulus that could decrease linearly to 25 psi (0.172 MN/m 2) at 300 psi (2.07 MN/m 2) shear were
stress; these values achieved over most
secant
shear
Silicone
modulus
elastomer
apply over the required temperature range. The required values of the temperature range except at -40 ° F (233 K), where the
was 72 psi (0.496 formulations
MN/m 2).
that
are
satisfactory
for use in flexible
joints
from
-40 ° F
(233 K) to 165 ° F (347 K) have been developed (ref. 85), but these elastomers are difficult to bond to metals. The best bonds have been achieved with steel, but even these bonds demonstrated adhesive failures. The failure adhesive shear strength for silicone elastomers varied
from
250 psi (1.72
MN/m 2 ) to 560 psi (3.86
25 psi (0.172 MN/m 2) to 40 psi (0.276 associated with the higher strength. These applications (dimethyl silicone formulations (208 stress
allowable shear require thinner
joint
an envelope
to have
2.1.3.2
strengths elastomer
with
a cone
modulus
at -160 ° F (166 K). The induced upon elastomer ring thickness,
are less for silicone formulations, layers. The shear stress is minimized angle
yield with
of approximately
zero
have
been
fabricated
with
steel
reinforcements
important stress, which
properties
in the
selection
of
ultimate and yield tensile stress, elastomers can be bonded to
degrees
(ref.
17).
and
with
composite
the
reinforcement
as ease
material
epoxy
are
resin
compressive
modulus of elasticity, ease of fabrication, the material, and cost' of the material.
of fabrication
stresses
in
a
and
cost became
reinforcement
are
a
the dominant factor stresses are relatively
ease For
with
unbonding
between
the
in selecting materials. For low (ref. 17), and factors
important. tensile
hoop
stress
compressive hoop stress on the inner radius (sec. 2.1.5.2) vectoring. Failures in the reinforcements have always occurred stress is compressive. For joints with steel reinforcements, wrinkling
reinforcements. and 25).
reinforcements, the interlaminar shear stress is also an important property. In the selection of material depends on the joint envelope. For joints with a large cone
angle, the mechanical properties have been conical envelope joints, the reinforcement
The
shear and
REINFORCEMENTS
composite addition
such
from
joints using these by designing the
The composite reinforcements have been formed with S-glass filaments (refs. 27, 28, and 29) and S-glass filaments and phenolic resin (refs. 24 and The
varied
MN/m2), the higher modulus generally being elastomers have been used for low-temperature have a glass transition temperature at -85 ° F
K), and methyl-phenol silicone formulations, due to motor pressure is directly dependent
because the formulations
Joints
MN/m 2 ); the shear
elastomer
42
and the
on
the
outer
radius
and
a
due to motor pressure and at the inner radius, where the the failure appears as a local
reinforcement,
so that
the joint
is
no longer a pressure seal. The wrinkling proceeds circumferentially around the reinforcement in a high-frequency wavepattern. For joints with compositereinforcements, the failure has appearedas rupture acrossa reinforcement thickness(ref. 27), interlaminar shear failure between different types of lamina in the laminate (ref. 28), or compressive failure (ref. 25). Correlation of test data for metal reinforcementswith calculatedresults(ref. 17, pp. 14-48, and sec.2.1.5.2) indicates that the stressat failure is the compressiveyield stress.However, buckling as a possible failure mode cannot be discounted. The failure buckling stressis dependent on the reinforcement dimensions,compressiveyield stress,and the modulus of elasticity (sec.2.1.5.2). The reinforcement material selectedaffectsthe bond to the elastomer.Elastomersthat have failed cohesivelywhen bonded to steelhavefailed adhesivelyat lower stresseswhen bonded to aluminum. Although it has been shown analytically that aluminum could be usedas a reinforcement material, it has not been usedin any joints. Joints that were fabricated with natural-robber elastomersand either epoxy-resin composites or phenolic-resin composites have never shown failure at the bond between the reinforcement and elastomer during bench testing. The joints of the motors on both stagesof Poseidoncontain 4130 steel heat treated to 180000 psi (1241 MN/m2) ultimate tensile stress,and the 260-in. motor (6.6 m) (ref. 22) incorporates4130 normalized steel. The joints of the 100-in. (2.54 m) motor (ref. 19) and 156-in. (3.96 m) motor (ref. 23) used304 Condition-A stainlesssteel,and the joint for the advanceddual-chambermotor (ref. 18) used 17-7PHannealedstainlesssteel. All of these joints have been bench tested successfully to pressuresin excess of ultimate design requirements. The first joints with composite reinforcements used continuous hoop-wound S-glass filaments with ERL 2256/Tonox 6040 epoxy resin to provide hoop strength and stiffness (ref. 27). During bench testing, these reinforcementsfailed transverseto the windings, thus showing a need for transversestrength. The transversestrength was provided by S-glass filament mats laid up between the continuouslywound S-glassfilaments (ref. 34), the mat filaments being oriented at an angle acrossthe hoop windings (refs. 27, 28, and 29). Joints with these configurations exhibited a changein the reinforcement failure mode and an improvement in joint strength when bench tested. To reduce the fabrication costs of composite reinforcements and to improve processcontrol, joints were fabricated with closed-die compression-molded reinforcements consisting of FM 4030-190 (phenolic-preimpregnatedS-glassroving) chopped into one-inch lengths (ref. 24). These joints were bench tested and static fired. Early joints for all three stagesof the Trident I (C4) engineeringdevelopmentmotors were fabricated with reinforcements of S-glasscloth preimpregnatedwith phenolic resin (ref. 25). Thesejoints were successfullybench tested, and static firings with vectored nozzles were conducted successfully on second-and
43
third-stage motors. However, in the motor development program structural problems occurred in the reinforcements in flightweight joints. The resin systemwas changed from phenolic stiffness
to an epoxy resin, data have not been
2.1.3.3 For
ADHESIVE
test
joints
BOND with
formulation by injection
intended molding
205
and
primer
specimens overcome
The
steel
for operation or compression
even though by ensuring
adhesive
SYSTEM
either
Chemlok
layer thickness reinforcements
and no further problems occurred. Fundamental strength and generated for the composite materials used in reinforcements.
220
the that
for
composite
between molding,
adhesive.
The
reinforcement
bond
failed
at low
(sec. 2.1.6.2). Applying in which failures always
the joint
with
and
65 ° F (291 K) and the adhesive system
surfaces of the steel were carefully the material lots were of sufficient
was controlled resulted in joints system
or
secondary
a
natural-rubber
85 ° F (303 K), fabricated has consisted of Chemlok strength
levels
in steel
test
prepared. This problem was quality and that the adhesive
the same controls to composite occurred in the reinforcement.
bonding
consisted
of a primer
system
for
the reinforcements, FMC 47 epoxy resin, and Chemlok system is a high-temperature system. After the primer
305 adhesive (ref. 22). The primer was applied to the reinforcements,
the reinforcements was cured during
adhesive,
The
adhesive
formulation compression
were cured joint molding.
systefh
for operation molding, was
with this system silicone rubber dissolved cohesive
2.1.3.4 The
joint
for test
specimens between Chemlok
with
K).
The
steel plates
Shear failures with K) and -40 ° F (233
THERMAL
thermal
protection
and
an ambient-cure
this system K).
system was were
fabricated by Shear failures
for test specimens with a 75 percent Chemlok 608
adhesive
at 165 ° F (347
K) and
PROTECTION has
been
effected
either
by insulating
boots
or by
thermal protectors (sec. 2.1.2.5.1). The important properties for thermal-protection materials are a low thermal diffusivity, high heat of ablation levels anticipated in temperatures expected
adhesive,
neoprene/polybutadiene-rubber
-40 ° F (233 K) and 165 ° F (347 K), 205 primer and Chemlok 231 adhesive.
were cohesive (ref. 85). The adhesive formulation for the same environment
in methanol. at 70 ° F (294
JOINT
at 300 ° F (422
service, and in service.
mechanical
flexibility
with
minimum
char
sacrificial
the under fracture
joint strain at
The choice of insulating boot material depends on whether the boot is protected by a radiation shield (fig. 7(a)). For insulating boots protected by a radiation shield, K1255 silicone rubber has been used. For joints with exposed insulating boots, materials have been
44
DC 1255 reinforced with chopped asbestosfiller to reinforce the char layer (reL 18) and silica-filled butadiene acrylonitrile rubber (refs. 13, 14, 19, and20). All of thesematerials have performed successfully,but they haveincreasedthe joint spring torque (sec.2.1.2.5.1). The sacrificial thermal protector materials have been either S-glass/phenolic-resinor carbon-cloth/phenolic-resin composites. The molded S-glass/phenolic-or epoxy-resin reinforcements (sec. 2.1.3.2) included the protectors in the molding (ref. 24). The carbon-cloth/phenolic-resin protectors were fabricated as an integral part of S-glass/phenolic-or epoxy-resincomposite reinforcements(ref. 25). Both of thesematerials have performed successfullyin static firings (refs. 24 and 25) without causingan increasein joint spring torque.
2.1.4
Mechanical
2.1.4.1
GENERAL
A flexible-joint dozen other
CONSIDERATIONS
configuration has been flown joint configurations have been
firings (refs. mathematical
The derived
performance.
These
Torsional Effect
design from
of pressure
Reinforcement
at zero
modified
To
establish
because the
joint
the
expected
pressure stiffness
- Section
2.1.2.1.1
- Section
2.1.2.1.1
- Section
2.1.5.1
Section
2.1.5.2
thickness steel
reinforcements,
according is analyzed
a joint properties joint
the
initial
component
relationships. An improved of analyses (refs. 17, 79 through
design
to
the
results
of the
96). However, no with test results
developed preliminary
in this monograph
thickness
the preliminary-analysis finite-element methods modified
flexible joint is data, to establish
are presented
on torsional
layer
with
of a limited
relationships
stiffness
Elastomer
design
on an operational vehicle, and approximately a either bench tested or demonstrated in static
13, 14, 17 through 20, 22 through 29, 95, and equations have been developed that correlate
configurations. relationships,
For joints
Design
from simple dimensions
general for all
empirical and joint
as follows:
dimensions
are established
from
analysis is then conducted with 82, and sec. 2.1.5.3), and the joint
finite-element
analysis.
If necessary,
the
again. with
composite
of the composite dimensions.
The
reinforcements, were
elastomer
45
unknown. layer
a different A joint thickness
method
is designed and
and
number
has been
used
fabricated of
elastomer
at
layers are calculated according to proceduresin section 2.1.5.1. The reinforcements are designed according to procedures in section 2.1.5.2, maximum strength at failure being assumedto be 60 000 psi (414 MN/m 2). To establish the allowable composite strength, the joint
is pressure
tested
to
failure
without
vectoring
preliminary analysis of section 2.1.5.2 and The allowable composite strength is defined regardless allowable methods.
of the joint mode composite strength
2.1.4.1.1
Design Definitions
and
the
results
correlated
with
the
a detailed finite-element analysis of the joint. as the calculated reinforcement stress at failure
of failure. The joint design is modified in accordance with this at ultimate load conditions and analyzed by finite-element
The design of a flexible joint usually is established and then defined on the basis of the relationship between the loading conditions that will be imposed on the joint and the capacity of the joint to withstand these loads. Limit load, design factor of safety, design load, allowable load, and margin of safety to this relationship between joint loading are used Limit or
in this monograph,
load. service
-
The
limit
pressure
3-standard-deviation physical variables motor or combination Design applied
pressure)
load that
is the can
in the
specified
expected
vehicle, or (3) the maximum of 3-standard-deviation limits
quality,
and
load
load (or pressure). and the
following
maximum be
design terms that loading capacity.
to
design
or calculated occur
value
under
load
(or
-
and of the
design safety factor is an arbitrary multiplier greater thart for design contingencies (e.g., variations in material properties,
1
design
motor or vehicle operating limits and specified operating limits.
load
maximum
a
- The
stress).
the
all environmental operating limits
within load
the
defined
structure).
(or pressure)
is the product
of the limit
load
(or
of safety.
Design stress. - The design stress is the stress, in any structural element, application of the design load or combination of design loads, whichever the highest stress. Allowable
of a service
(1)
by
distributions
factor
are used with respect These terms, as they
paragraphs.
operating limits of the motor or vehicle including that influence loads, (2) the specified maximum
safety factor. -The in design to account
fabrication Design
are defined
are joint and joint
The
allowable
load
the slightest, produces joint failure. Joint failure failure, whichever condition prevents the joint Allowable load is sometimes referred to as criterion
46
(or stress) may from load
is the
be defined performing or stress.
load
resulting condition
that,
from the results in
if exceeded
as yielding its intended
or ultimate function.
in
Margin of safety. - The margin of safety (MS) is the fraction stress exceeds the design load or stress. The margin of safety MS
where
R is the ratio
2.1.4.2
DESIGN
Ideally,
the design
of the design
SAFETY safety
overall
factor
factor
All flexible-joint loads as defined
The
•
Motor
•
Vectoring
•
Vehicle
•
Handling
motor
joint. rings.
loads above.
tensile
would
be calculated
stresses
motor
modulus
load
or stress.
from
a knowledge
of the
randomness
is designed
to a safety
factor
of
there to the
sufficiently engineering requires an
of 1.5.
LOADS used in the flexible-joint The loads on the flexible
and
storage
acts
during
structural analysis (sec. 2.1.5) joint are those that result from
are
design
flight
conditions
as a crushing
pressure
tensile and compressive the compressive hoop
and
also
causes
an axial
compression
on the
hoop stresses are developed in the reinforcement stress in the reinforcements is more critical than the
....
pressure.
is dependent
As a result
of vehicle
section
the
of
the joint
accelerations
Vectoring of the joint reduces these stresses with
to the allowable
pressure
pressure
Significant In general,
or
(5)
required reliability and confidence levels. Unfortunately, of the relationship of the assumed failure criteria
of 1.25,
FLEXIBLE-JOINT
load
1
stress distributions in a joint, and the methods of analysis are not At present, a safety factor is established largely on the basis of combined with experience. As an example, if the motor specification safety
2.1.4.3
or stress
the allowable as
FACTOR
the design variables and the is insufficient understanding complex accurate. judgement
load
1 R
by which is defined
nozzle
increases the reinforcement hoop stresses on one side of the joint and on the other. Shear stresses induced in the elastomer rings increase Vectoring on strain accelerations imposes
rate
affects
the
elastomer
shear
stresses
since
the
shear
rate. during loads
on
launch, the
47
joint.
flight, These
or staging,the loads
can
mass cause
of the movable all the
stresses
induced by motor pressureor vectoring and, in addition, can causean axial tensileload on the joint. Usually the stressesdue to vehicle accelerationsare not critical conditions. Handling
and
storage
During handling joint, since such
2.1.5
conditions
and loads
Structural
The structural reinforcement
The
analysis thickness,
ELASTOMER
stresses
in the
all the
stresses
induced
by the
tensile from
previous
conditions.
loads are imposed the reinforcement.
consists and the
of the determination finite-element analysis.
to determine stresses.
internal
of the elastomer thickness, the All structural analyses consist of
stresses,
and
a strength
analysis
comparing
THICKNESS elastomer
are
caused
due to vectoring is approximately thickness of elastomer (i.e., number
by vectoring
and
constant in the of elastomer rings
motor
elastomer x thickness
pressure.
rv
=
0.01745Go
The
shear
on the joint spring due to vectoring is
Rp 0
(6)
_nte
where rv = shear
stress
due
to vectoring,
psi (N/m 2)
(eq.(1)),
Go
= secant shear modulus at 50 psi (0.345MN/m psi (N/m 2 ), at the elastomer temperatures
Rp
= pivot
radius,
0 = vector
angle,
n = number te
= thickness
Angle 0 is expressed
numerically
2 ) shear stress (sec. expected in operation.
in. (cm) deg*
of elastomer
layers
of individual in degrees,
elastomer
not radians,
layer,
in this empirical
48
stress
and depends on the total of each layer) and not the
thickness of each ring.: The induced stress due to vectoring is dependent torque, decreasing as the joint spring torque is reduced. The shear stress given by the expression (ref. 23)
and, as before
on the
Analysis
two parts: a stress analysis internal stresses to allowable
2;1.5.1
cause
storage care is taken that no axial can cause debonding of the elastomer
in. (cm) expression.
2.1.7.1),
The shearstressdue to pressureis dependentupon the thicknessof eachelastomerlayer and is givenby the expression(ref. 79)
re =
te Pc Ke Rp 2
(7)
17.5
where rp = shear
stress
Pc
= motor
Ke
= correction
Calculated
results
17). The
correction
in figure
18.
due
pressure,
have
factor
shown
factor
1°0
to pressure,
psi (N/m 2)
psi (N/m 2 ) for elastomer
that
stress,
the shear
Ke has been
derived
stress
depending
increases
from
the
upon
cone
as the cone
results
angle.
angle
of reference
n
O l.I
0.6
O 4-1 4.1
0.4 0
0.2
0
I
I
I
I
I
I0
20
30
40
50
Cone
angle
_ , deg
Figure 18. - Shear-stress correction factors related to cone angle (ref. 17).
49
(ref.
17 and is shown
_d
t_ q4
increases
The resultant pressure, i.e.,
shear
stress
Zr in the
elastomer
is the
sum of the stresses
due to vectoring
r_ = r_ + rp The
resultant
stress
is compared
shear
stress
the
been
considered
(8)
allowable
shear
The
allowable
from have
a quadruple-lap shear specimen (sec. 2.1.7.1). ignored the increase in failure shear stress due
stress in an elastomer criterion is not known. the The
increase
is a complex Until the failure
in failure
following
shear
procedure
Calculate the shear stress due to the maximum various elastomer layer thicknesses.
(4)
Calculate
the
net
(5)
Determine
the
design
(6)
Plot
axial mode
design
loading
stress
ultimate
ultimate
is
of
shear
a design using the
stress to date state of
associated whether
failure ignoring
thickness:
elastomer
due to vectoring
shear
shear
required
expected
elastomer
shear
stress:
stress
as a function
ru_t
stress
parameter, calculated
spring
torque
(sec.
rv.
rr at various
shear
for
=
operating
layer
of elastomer
the axial thickness,
rp for
thicknesses.
rr X design
to determine
pressure
safety
layer
the
factor
thickness
maximum
and
allowable
deflection is calculated and compared with
by the
The elastomer thickness may be reduced if the axial compression exceeds but the net radial thickness is maintained in order to satisfy spring torque The effect of reducing the thickness is to reduce the net shear stress and the
REINFORCEMENT
stresses
stress
it with the allowable layer thickness.
deflection, increase of the reinforcements.
2.1.5.2
shear
thickness
field, and the it is not known
elastomer
(3)
requirements. requirements, requirements.
radial
the
Calculate
the
net
to determine
measured
joints designed pressure. The
is conservative.
(2)
If axial compression finite-element methods,
these
is used
three-dimensional criterion is known,
due to pressure
minimum
All successful to superimposed
Calculate 2.1.2.1.1).
the
the
stress
stress.
to be the
(1)
compare elastomer
The
has
with
and
in the
the
number
layers,
and
affect
the
compressive
failure
THICKNESS
reinforcements
conditions,
of elastomer
each
are
caused
reinforcement
by cross
50
motor section
pressure rotates
and vectoring. but
does
not
For
both
significantly
of
\, ",\
change shape. reinforcement
Such rotation causes a bending stress distribution with tension at the outer radius and comPression on
compressive stress on outer surface, so that
the 'inner it is 0nly
radius has always been necessary to determine
13, 14, 24, 27 to 29, 101, and 102). fatigue charactei_istics and fracture stresses of equal concern.
For motors mechanics
radially the inner
greater than the tensile the compressive stress
across radius. stress (refs.
the The
on the 17, 22,
that will be operated a number of times, are considerations that make the tensile
\
The compressive reinforcements
hoop, stress (ref. 79):
due
to pressure
depends
on the
number
and
dimensions
of the
"\
ap
4087
-
Pc
Kr _2
n-1
(9)
where ap
= compressive
Kr
= correction
hoop factor
stress
due
to pressure,
for reinforcement
psi (N/m 2)
stress,
the
value
depending
cone angle (ref. 1'7). The correction factor Kr has been the results of reference 17 and is shown in figure 18. n = number
of elastomer
layers Rp
3283tr
/3,/31,/32 The
= joint
compressive
2-4
cos
of reinforcement
angles
hoop
stress
(fig.
as described
in section
from
2.1.5.1.
/3
3 + tr COS2 /3 {Rp 2 (/32 -
-- thickness
tr
determined
on the
derived
in joint,
/31 )2
_3283tr
2}
in. (cm)
12), deg*
due
to vectoring
Ov -
av is given
43950
0
by (ref.
79)
K_ £Z
(10)
n-1 Equations (9) and varied in diameter
(10) are empirical relationships from 8 in. (20.3 cm) to
relationships
not
/3,/31,
and
_2
have are
expressed
been numerically
developed in degrees,
for tensile not
radians,
51
derived from results of tests of joints that 22 in. (55.9 cm). Corresponding empirical stresses. in equation
When (9)
and
(10).
the
cone
angle
is large,
the
tensile stressesare only slightly less than the compressivestresses,but as the cone angle becomes smaller, the tensile stressdiminishes until the reinforcement is in a completely compressivestate (ref. 17). The resultant hoop compressivestressor stresses
due to vectoring
and pressure, Or
The net
stress
Failure
modes
and
bulk
or is compared for
compression.
windings only reinforcements compression.
The
allowable
(buckling material
=
the
The
failure
reinforcement
av
O'p
-k
allowable
reinforcements
is rupture fabricated
bulk
layers.
steel
with
in the
compressive
are buckling mode
stress
The
buckling
stress
in high-frequency
for composite
for metal
for
metal
on specimens slightly curved
that edge effects were negligible. thickness was varied, and different stainless 6061-T6
steel, 304 aluminum,
reinforcement
CRES and
material
reinforcements
The ratio reinforcement
of
depends
has
been
with
the
hoop
modes shear
failure
for and
mode
are
established
from
a test
surface of a joint. The column was long enough so
reinforcement materials were
dimensions
upon
waves
a function of the reinforcement and the thickness of the elastomer
stainless steel, 17-7PH aluminum. Results and
fabricated
thickness. The failure windings are interlaminar
reinforcements
1)
circumferential
reinforcements
representing the inside across the width, and the
annealed 7075-T6
properties
compressive
stress.
or bulk compression) and consequently is modulus of elasticity, reinforcement dimensions,
program conducted reinforcements were
sum of the
(1
across the reinforcement with mats and continuous
compressive
is the
i.e.,
thickness used: 301
CRES annealed of the tests shown
in
to elastomer CRES half-hard stainless correlated
figure
19.
The
steel, with bulk
compression stress has been established as the compressive yield stress (ref. 17). Tests were conducted on two joints with stainless steel reinforcements; the joints were identical except that the steel was heat treated to different yield compression stress levels. The failure pressures for the joints were different, and joint, calculated by finite-element methods, yield
stresses
The
allowable
test joints The
for the reinforcement
with
following
compressive composite procedure
the
stress
number
failed reinforcement of each equal to the compressive
materials. for
composite
reinforcements is used
the stress in the was approximately
that
to determine
reinforcements approximate
the reinforcement
(1)
Determine
of elastomer
(2)
Calculate the compressive hoop reinforcement thicknesses (eq. (9)).
52
layers stress
(sec. due
is often
the desired
established
joint
from
design.
thickness:
2.1.5.1). to
pressure
(Or)
for
various
l_/m
2
ksi
828
120
690
i00
552
80--
414
60
4.1
=
0
,-4
__
TEST
L_ GO
• 276
20
oV in.-ibf N-m
304
CRES
0 17-7 17 3ol c_s
40
138
DATA
units
units
0
7075
T6
A
6061
T6
I
I
I
I
I
2
3
4
3.32
6.63
9.95 E 1/2
t
5 x
13.26
16.58
3/4 r
1/2
t e
Figure
19. - Buckling
stress for
metal
reinforcements
as a function
of the
properties
and dimensions
of the reinforcement.
103 x
104
(3)
Calculate the compressive hoop reinforcement thicknesses (eq. (10)).
(4)
Calculate
(5)
the
thicknesses
(eq.
Determine
the
thicknesses: (6)
net
compressive
hoop
ultimate
compressive
design
the
=
or X design
buckling
Plot the function minimum
material
ADVANCED
Analysis
by
assembly, structural
The
with
test
limitations
theory
of
modified
properties, properties;
methods
hoop
the
technique
(refs.
the
finite-element
pressure
(ref.
been 80).
various
reinforcement
for various
reinforcement
for various yield
reinforcement
thicknesses
stress.
stress and intersection
the buckling stress as a of these plots is the
enough probably
to ensure that the failure results in over-strength
allows
in sections Results from
structures
to be analyzed
as an
2.1.5.1 and 2.1.5.2 analyzes the the finite-element method present a in an assembly. have shown good
results.
to account
has
stress
80 to 82)
method
load
that effects;
(1)
it is basically
(2) material
have been introduced (ref. structures such as a flexible
condition, obtained A
are
for large-deformation
during loading. Each of these in the elastomer are large strains;
motor
strains
stress
of the stress, strain, and deformation distribution of the assumptions in the method, calculated results
but depend upon the local stresses an axisymmetric loading condition, For
hoop
compressive
employed assembly.
although refinements and (3) for continuum
axisymmetric The strains
various
for
factor
the reinforcements thick However, this approach
the method forming the
complete description Within the limitations agreement
for
(Ov)
ANALYSIS
finite-element
whereas elements
vectoring
(or)
design ultimate compressive hoop of reinforcement thickness. The allowable reinforcement thickness.
It has been the practice to make mode will be bulk compression. reinforcements. 2.1.5.3
to
stress
safety
compressive
up to the reinforcement
(7)
due
(11)).
oult
Determine
stress
103) joint,
good
limitations affect the analysis of a flexible the elastomer material properties are not
correlation the
is applied
are elastic
to include nonlinear the structure must be
in the elastomer; and, although motor vectoring is an asymmetric condition.
with
small-deflection
properties
use to
54
with
axial
deflection
of an incremental the
initial
geometry;
pressure
and
loading the
joint. elastic imposes
reinforcement
and stress
deformation and
strain
distribution for that load are determined, and the shape for the next increment is established by algebraically adding the deflections to. the initial geometry. The final deflected shape is determined when the last load increment is applied; the final stressand strain distributions are obtained by summing the stressesand strains for each load increment. In generalin this analysisfour load incrementsgivea reasonablecorrelation with test results. Although the shear modulus of the elastomer is dependent upon the local stresses,a constant secantshearmodulus at 50 psi (0.345 MN/m2) shearstress(sec.2.1.7.1) is used for all loading increments. Other required properties are calculated on the assumptionthat the material is isotropic and hasa value for Poisson'sratio as closeto 0.5 as the computer can accept. Efforts to usean effective shearmodulus (sec.2.1.5.1)have been unsuccessful. For the vectoring condition, the joint cross section changes,extending on one side and compressingon the other. An analysistechnique similar to that for the motor pressureis used.Componentsof the actuator load are applied to the moving surfaceof the joint as a uniformly distributed axial loading, sinusoidally distributed shearloading, and a linearly varying bending distribution acrossthe joint diameter.An increment of loading is applied as before to determine the geometry for the next increment. The stresseson one sidewill add to the stressesdue to motor pressureand subtract on the other. Only the geometry for that sidewhere the vectoring stressesadd is usedin the next increment. The geometry for that sideis assumedto be axisymmetric, andthe loadsare applied incrementally. Final geometry and stress distribution are determined as described in the preceding paragraph;material properties aspreviouslydescribedare used. Net stressesdue to motor pressureand vectoring are obtained by algebraically adding the stressesdue to eachload condition. The strength analysisfor the elastomeris conductedby comparing the maximum principal shear stress to the minimum measuredshear stress measuredfrom a quadruple-lap shear(QLS) specimen(sec.2.1.7.1). The strength analysis for the reinforcementscomparesthe maximum compressivehoop stresson the inner radius to the allowable compressivestress(sec.2.1.5.2). 2.1.6
The
Manufacture
sequence
reinforcements, elastomer, and
2.1.6.1
of
steps
for
fabrication
development of the molding of the joint.
of adhesive
a flexible system
joint between
involves the
manufacture
of
the
reinforcement_and_.the
REINFORCEMENTS
The joint reinforcements reinforcement material,
have been fabricated by a number of methods; and fabrication method are summarized in table
55
dimensional VII.
details,
TABLE VII. - Details of Reinforcements
Average spherical Motor
radius
Rp, in.
100-1nch
14.6
156-Inch
36.8
260-Inch
Conical:
Used in Flexible
Joints on Operational
Thickness tr, in.
and Development
Material
Motors
Fabrication
method
Ref.
304
Hydroformed
19
0.040
304
Spun
23
0.700
4130
0.038
normalized
Machined
from roll ring 22
forging
58 outer radius, 54 inner radius
Poseidon
C3 first stage
13.85
0.183
4130,
180 ksi
Stamped
and machined
95
Poseidon
C3 Second stage
13.69
0.108
4130,
180 ksi
Stamped
and machined
96
Dual chamber
5.75
0.060
17-7PH
NAVORD
7.18
0.110
4130,
13.69
0.108
Hoop-wound S-glass core overlaid with S-glass cloth
Poseidon
TMC/TVC C3 modified
second-stage
annealed 180 ksi
Explosive
formed
18
Machined
from plate
14
Compression
molded
27
and epoxy resin Trident I (C4) second-stage
10.34
0.050
S-glass and carbon cloth pre-impregnated
NAVORD
IRR
3.69
Notes: 1 in. = 2.54 cm TMC/TVC = thrust magnitude control/thrust vector control IRR = integral rocket ramjet
0.140
with
phenolic
resin
Chopped resin
S-glass/phenolic
Matched-metal molded
Closed-die molded
compression
compression
25
24
Steel
reinforcements.
been formed pressure was
-Hydroformed
reinforcements
by mounting an annealed circular applied to the plate, it expanded
for the
plate into
100-in.
(2.54
m) motor
in a pressurizing fixture (ref. 17). When an ellipsoidal shape. The reinforcement
was then machined from the expanded plate and heat treated to the required The spherical radius for each reinforcement in a joint was controlled by varying to which the plate was expanded. The reinforcements for the 156-in, reduce costs, all the reinforcements
have
(3.96 m) motor (ref. 23) were formed were spun from a standard conical
properties. the height
by spinning. To preform, welded
from three standard patterns that were cut from only one standard template. After welding, the conical preforms were stress relieved and pressed onto a mandrel in a horizontal shear spinning machine. Spinning was conducted in each direction from the center. The center of the reinforcement received the least section. After spinning was completed, finish
machined.
Reinforcement
amount of cold working and remained the thickest the reinforcement inner and outer diameters were
thickness
was
controlled
by measuring
the
thickness
of the
conical preform prior to installation on the mandrel, and estimating the amount of thinning required. Thinning was accomplished by belt sanding for a predetermined time after the reinforcement was formed. This method assured that each reinforcement received the same amount of cold reinforcement. In the
260-in.
thick,
the
working
(6.6
large
m)
by
motor
diameter
shear
(ref.
resulted
spinning
and
resulted
22), although in flexible
the
sections.
in a uniform
strength
reinforcements The
were
reinforcements
level
for each
0.7 in. (17.8 were
not
mm)
spherical
sections as in all previous joints but were conical sections. Since the joint envelope was cylindrical, each reinforcement was identical and only a single set of tooling was required for all reinforcements. This design resulted in cost savings in comparison with a joint with spherical reinforcements of progressively increasing radii. The reinforcements were machined from roll ring forgings. Any distortion occurring in the finished reinforcements either due to machining or handling was easily corrected in the joint mold as a result of the flexibility of the large-diameter reinforcements. Reinforcements
for the
Poseidon
motors
were
fabricated
by
stamping
washer-shaped
into the required section; this process required a die for each reinforcement. the steel was in a normalized condition. After stamping, the reinforcements machined, heat treated to the required properties, and then final machined. results
in
distortion
of
the
reinforcements,
but
performance if each individual reinforcement 2.1.6.3). The thinner reinforcements formed forming have not exhibited this distortion. The
reinforcements
for
blank of material. The reinforcement, making
the
dual-chamber
this
distortion
has
little
At stamping, were rough This method effect
is aligned in the joint molding by hydroforming, spinning,
motor
were
explosively
formed
disks
on
from
a circular
blank was clamped over a die that had the required contour it necessary to have a die for each reinforcement in the joint.
57
joint
fixture (sec. or explosive
of the Due to
forming, the thickness of the reinforcement was 4 percent to 5 percentlessthan the blank thickness.The reinforcement was final machinedfrom the formed section. The reinforcements for the NAVORD TMC/TVC joint (refs. 13 and 14) were machined from plate material. Only a few joints wereto be fabricated, andthis method eliminated the need for expensivetooling. The plate material was in a normalized condition and the reinforcements were rough machined. After machining, the reinforcements were heat treated andfinish machined. Composite reinforcements.12-end roving glass filaments
Early composite reinforcements were fabricated with an epoxy resin (ref. 28). The reinforcement
was formed by hoop winding between two plates. This system transverse strength and was modified by overlaying the hoop-wound cloth. A better method of forming these reinforcements was
with S-901 cross section
resulted in insufficient core with $34/901 glass to "B-stage" (partially
polymerize) the hoop-wound core, lay up the cloth on the faces of the core, replace in a mold, and cure under pressure (ref. 28). In this procedure, the ERR-4205 resin system was used because this sytem could be hardened, reliquified, and final cured. The same technique and materials were used to fabricate composite reinforcements for an experimental second-stage
Poseidon
C3 joint
(ref.
In the engineering development reinforcements were fabricated broadgoods,
each
27).
program, from
preimpregnated
with
for the second S-904 glass-fiber phenolic
resin
(ref.
stage of Trident I (C4) the joint broadgoods and carbon-fiber 25).
In the
motor
development
program, however, to overcome structural problems, the S-904 glass-fiber broadgoods preimpregnated with epoxy resin. The two types of broadgoods were sewn together, into The
specific patterns, glass broadgoods
assembled in a matched formed the reinforcement,
joint thermal protection. different mold for each To reduce the cost for the NAVORD molded included
in closed-die the
this method
2.1.6.2 The
joint
joint
metal mold, and cured at 325 ° F (436 and the carbon broadgoods formed
Each reinforcement reinforcement.
and complexity IRR joint were
had
of composite made from
compression thermal
molds
protection.
(ref.
These
were cut
a different
spherical
radius,
reinforcement fabrication, chopped S-glass/phenolic-resin 24).
The
reinforcement
reinforcements
demonstrated
K). the
requiring
a
reinforcements compound
molding the
integrally feasilibity
of
of fabrication.
JOINT
ADHESIVE
adhesive
system
by compression or injection 260-in. (6.6 m) motor joint
SYSTEM may
be formed
molding, (ref. 22).
during
or it may
the
molding
be obtained
process
by secondary
58
,\
(
_
for joints bonding,
fabricated as in the
Rubber-to-metal
adhesive
high stresses the adhesive
bonds
a bond Systems
adhesive
(sec.
strength designed
unbonding thin, the
problem resulting
During
Failures
have
also
fabrication,
occurred
and
Flexible
wiped the conditions.
of joints
in the
inch
adhesive When
strength, so that have consisted
failures are cohesive of a primer and an
system has acceptance close
monitoring
(sec.
2.1.7.2),
bond
FLEXIBLE joints
have
failures
that
were
when
the
been obtained tests of each
liaison
the
do not have
adhesive
layer
is then
the
to too
thickness
was
as
with
viscosity
the
of
sufficient
by lot
controlling of material
adhesive
the
primer
suppliers. and
being
thickness be used
Thickness
adhesive,
and the time for quadruple-lap shear
strength
the to
the
of the in joint
control rate
has
at which
spraying. The material tests (sec. 2.1.7.1) and
rejected.
JOINT been
The compression technique between the reinforcements compression, balls between
attributed
in the adhesive system materials. from 3 lbf per linear inch (5.25
fabricated
by
three
different
methods:
compression
molding (refs. 17, 23, 25, and 27), injection or transfer molding (refs. 29), or secondary bonding of precured elastomer (ref. 22). A summary and disadvantages of these methods is presented in table VIII.
parts
the result was used,
N/cm).
are sprayed on the reinforcements, have been selected by conducting
all lots that
system off the reinforcement, a compression molding process
unbonding did occur. When the bond layer was below acceptable levels, and adhesive failures
adhesive
(61.25
maintaining by
these materials lots to be used
2.1.6.3
joint,
of the fabrication problems involve the adhesive system is required to
resulted from lot-to-lot variations specimens failed at values varying
adhesive requiring
obtained
tests,
In a flexible
occurred.
to 35 lbf per linear
A satisfactory adhesive layer,
peel
changes.
in this kind of system has been affected by bond layer thickness. too thick and an injection molding process was used to fabricate
testing
required. These failures For example, peel test
been
and the bulk reliability,
was not as acute but bond strength was
bench
layer
have
N/cm)
process
2.1.3.3).
the joint, the flowing rubber being unacceptable unbonded
thin a bond
to small
greater than the elastomer to satisfy this requirement
The strength of the bonds When the bond layer was
occurred.
sensitive
are imposed on these bonds, system. To ensure increased
develop failures.
the too
are
compressed
or layup
13, 14, 24, 28, and of the advantages
involves physically placing strips of partially cured elastomer as the joint is assembled in the mold. The resulting assembly of by
closing
the
mold
and
providing
molding
pressure.
During
the thickness of the elastomer layers has been controlled by inserting steel the reinforcements. In early joints, the balls were positioned at the center of
reinforcements.
As the
joint
was vectored,
9
the
balls
gouged
the
reinforcement
and
cut
TABLE VIII. - Advantages
Process
Injection
and Disadvantages
of Joint Fabrication
Advantages
molding
Processes
Disadvantages
Demonstrated production technique used to " fabricate joints for nozzles on Poseidon firstand second-stage motors. Has the potential of giving uniform rubberpad thicknesses. (However, in actual production of joints for Poseidon this method resulted in nonuniform pad thicknesses on many joints. The lack of uniformity seems to be associated with tool design and wear.)
Comparatively expensive process because of the complicated method of setup and fabrication. The tooling costs are much higher than those for compression-molded joints. Has inherent bonding problems. The elastomer must flow considerable distances over the reinforcements and end rings, and the flow of hot rubber tends to remove the primer or adhesive. This problem does not occur with silicone elastomer, because the primer/adhesive system can be precured on the components. Sometimes yields joints in which the rubber is not fully compacted in all areas. This condition results in joints that leak during the proof test and are therefore rejected.
0 Compression
molding
Demonstrated production technique used to fabricate joints for nozzles on Poseidon firststage and second-stage motors. Low-cost manufacturing process and simple low-cost tooling. Joints produced by this method are approximately 30 percent lower in cost than those produced by the injection process. When natural rubber or polyisoprene rubbers are used, excellent bonding between the rubber and the reinforcements and between the rubber
Secondary
bonding
Some difficulty with bonding and porosity attributable to the tolerance variation on calendered rubber. Some difficulty
in bonding
silicone elastomer.
and end rings in achieved.
Produces joints with very uniform nesses.
pad thick-
The rubber pads have good compaction can be inspected prior to assembly. Tooling
Spacers are required. The spacers sometimes move as a result of rubber flow, and uneven rubber-pad thicknesses can result. Furthermore, small local defects in the rubber-pad layers are created when spacers are removed.
costs are low.
and
Process has inherent
bonding
problems.
Production experience limited. To date only a few joints have been fabricated by this process.
holes than
in the elastomer. In later that of the elastomer, the
joint
and
The
injection
were
removed
after
molding
technique
that holds them the reinforcements. The
molding
in position
method
joints balls
where the width of the reinforcements were positioned at the inner and outer
was greater edges of the
molding. consists
and
selected
have been used for the same occurred have been common
then
injecting
depends joint to
simply
of stacking
rubber
from
on the
preference
design and compression
produced molding
the
reinforcements
a reservoir
into
the
of the fabricator; similar results. and injection
in a mold gaps between
both
techniques
Major problems molding. The
that three
major problems have been porosity in the elastomer, variation in the thickness of each elastomer ring, and variation in the thickness between elastomer rings. Porosity in the elastomer occurred because the elastomer could flow .easily out of the mold or into large voids
in the
minimizing Variation
mold.
This
problem
was
eliminated
clearances between metal in the thickness of elastomer
clearances variations.
by
designing
a mold
without
voids
and
parts to avoid elastomer expansion out of the mold. rings has been due to a number of causes. Excessive
in the mold to accommodate parts with Thickness variations have also occurred
excessive because
tolerances has caused thickness of movement and deflection of
the joint under the high pressures of molding. Tolerance problems are avoided if the pad thickness is controlled directly by the two metal surfaces involved; this procedure minimizes the number of tolerances involved in a worst-on-worst situation. The deflection of parts can be reduced
only
by
specifications. In Movement of the surfaces that are variations inspected uniform
stiffening
the
in an elastomer
layer
for flatness and spherical elastomer layer thickness.
was cheaper (ref. 22). As bonded to the reinforcement.
axial
correct alignment. at 5 psi (0.0345 pressure
but
for a joint
The secondary bonding technique because of a lack of sufficiently
ensure loaded
parts,
stiffening
may
be impossible
because
of design
such a situation, the deflection must be tolerated and allowed for. parts in the mold, however, has been controlled by indexing parts from self-centering, i.e., conical or spherical surfaces. To avoid thickness
was
radius
with
thick
reinforcements,
variations
and
are
the
aligned
reinforcements in the
has had limited application. It was used large facilities to cure at high temperature
each reinforcement Care was taken
was laid in the during the layup
to
ensure
good
adherence
between
to give
on a large joint and because it
mold, the elastomer of the reinforcements
An ambient cure adhesive was used (sec. 2.1.3.3) MN/m 2) axial pressure by mechanical actuators
used
mold
are
the
and the joint during cure.
elastomer
and
was to was The metal
components. Two important diagnostic aids exist in joint manufacture. These aids have assisted in the discovery of manufacturing problems and the determination of the effectiveness of corrective actions. The first diagnostic aid is molding of a joint without applying the adhesive
system
to the
metal
parts;
with
this exception,
61
the
molding
process
is carried
out
normally. After molding, the rubber is easily removed from between the metal parts and examined for thicknessand porosity. The secondaid is simply the dissection of a normal, production joint by cutting through the rubber between metal parts; the resulting pieces reveal any areaswhere the rubber-to-metal bond was unsatisfactory. This technique also showsporosity andgeneralcondition of the rubber.
2.1.7 The
Testing
•
flexible-joint
test
program
is conducted
to determine
elastomer
material
characteristics,
joint spring stiffnesses, nozzle operating characteristics, and nozzle failure strengths so that compliance with motor requirements is demonstrated. If new elastomeric materials are to be considered, a material characterization program is conducted (sec. 2.1.3). The test program consists of subscale testing, joint bench testing, nozzle actuation testing, static firing testing, joint
aging
2.1.7.1 The and
testing,
frequency-response
SUBSCALE
TEST
subscale test program of the bond between
of the elastomer. in the
the test
specimen
most
same
modulus, the reinforcements.
manner
of test
as the
specimens,
surfaces
of the
the
of the
in the manner
properties
used
operation, in terms
!_, -: _._
:,
_
modulus ._
Go
=
elastomer
used
in the
with the quadruple-lap of the test as follows:
shear
strain
applied stress
r
Shear
strain
_/
=
2 × length
increase
in crosshead
2 X thickness
62
flexible
shear
of pad
separation of pad
joint
(QLS)
are
specimen
stress
MN/m 2 ) shear
load
× width
must
be
if possible,
of the joint.
MN/m 2 ) shear
at 50 psi (0.345
test plates
in the joint;
the
shear
of the elastomer to the metal range of temperature in the
-
Shear
of the
for manufacture
50 psi (0.345 Shear
surfaces
reinforcements
shear stress at failure, and the bond strength These properties are measured over the
elastomer expected during The properties are defined
'
testing.
is conducted to measure mechanical properties of the elastomer elastomer and reinforcement and to evaluate aging characteristics
is fabricated
important
and destructive
PROGRAM
In the preparation
prepared
The
testing,
stress
(fig. 20).
(7.62
cm)
3 in_ 118
i/8
in.
(3.2
(2.54
nun)
•v ---- f I: Ii
cm)
(2.54
I
I
I
II
I.!. '
J
i
II
N"////A l I
in.
cm)
(3.2
n-_) I
I/I///A,_
IlI l l----I"_Elastomeric for
material
test I in.
---_
I
Figure
Even
though
sufficient properties
the
elastomer
Shear
movement. reference
modulus The secant
- Quadruple-lap
in a joint
characteristics joint instability,
determine elastomer shear tension have been conducted The
20.
motor pressure, and have been determined
of the physical pressure, overall
,
I
cm)
shear test specimen.
is subjected
to compression
and
of flexible joints and nonlinearity
if vectored
at
(the reduction in actuation torque with of axial compression), limited efforts to
the
joint
spring
torque,
to superimposed
axial
compression
deflection,
stress-strain response is nonlinear, but most analyses shear modulus at 50 psi (0.345 MN/m 2 ) shear stress;
for quality control. necessary to ensure
shear
to tension and shear if vectored at zero motor pressure, the only for applied shear loads. To improve the understanding
properties when subjected (refs. 22 and 78).
controls
I__
and
and
pivot-point
assume linearity at a this value is also used
The elastomer varies from lot to lot, and close quality control a modulus acceptance range of 10 psi (0.069 MN/m 2). In a production
is
program, the testing of each lot can indicate a relaxation of manufacturing quality control or a change in the manufacturing process. The QLS is used as a quality control tool aS well as a means to qualify new elastomers and new adhesive systems. If the aging characteristics of the elastomer are not known, a subscale test initiated early in the program. This program includes testing not only characteristics of the cured elastomer but also the effect of aging of the uncured on the resulting cured elastomer. in a program, the results of joint
'
When such effects are not determined tests are subject to misinterpretation.
63
program is the aging elastomer
and controlled
early
In evaluating the aging of uncured material storage environment and,
elastomer, at intervals,
the uncured elastomer is stored test specimens are prepared and
in the cured.
usual Tests
are conducted, and the shelf life of the uncured elastomer is determined from the results. The selected shelf life is the time during which no change occurs in the secant shear modulus of the cured elastomer. To
evaluate
stored
aging
in the
characteristics
of
environment
and,
motor
cured
material,
at intervals,
elastomer properties are plotted against time, service life of the elastomer. Properties obtained Service life testing thereafter. Results modulus When
up to 3½ years a joint
therefore elastomer
and
is injection
2.1.7.2
by testing
BENCH
joint
bench
test
then
elastomer
a subscale
test
remain the
from
program
and the results are at zero time provide
monthly intervals up to natural-rubber formulations
several
lots
conducted.
is
The
extrapolated to predict a basis for compariso/_. 6 months and annually increase in secant shear
constant. test
specimen
elastomer aging joint. The aging
full-scale
TEST
at that
molded,
the measured in the full-scale
are assessed
The
is conducted have shown
cured
cannot
be fabricated
characteristics characteristics
in similar
may differ from of injection-molded
fashion;
those joints
of the usually
joints.
PROGRAM program
is conducted
to determine
axial
compression
due to pressure,
spring torque, offset torque, sealing capability of the joint, and the location of the effective pivot point; to verify calculations; and to demonstrate structural integrity of the joint. Thus data must be obtained as early as possible in a program to confirm clearance envelopes in the nozzle continued
design. When a program for quality control.
The
compression
axial
clearance the joint
envelopes. is expected
is in the
is required
to
production
determine
phase,
the
axial
the
spring
The bench testing is conducted at the same to transmit during actual motor operation.
bench
stiffness
test
program
and
to
is
check
pressure and axial load This condition requires
as a
special test fixture, as shown in figure 21, that contains provisions for adjusting the axial load on the joint. An unloading piston is used for this purpose. The unloading piston is sized such that the net axial load on the joint at pressure while undergoing test is equal to the load load
that will be imposed on the joint during acting on the joint during motor operation
During
the
development
axial compression analyses. The
quality
program,
of joints to eliminate
are
tests,
hoop
measured.
These
in a production possible
strains
at the
data
program
low-quality
actual motor is calculated are
of the reinforcements
of value
varies
joints
64
edges
and
operation. The net gas-pressure as described in section 2.1.2.3. in checking
considerably ensure
from the
the
joint
reliability
as well validity
to joint. of the
as the of the
In one motor,
a
Unloading
piston
Flexible
joint
UnloadingA
cross
I Un loadi_J_
cross
_J"
_Pressure
_--T-""_/_
_Post
I
pis ton
bar vessel attached
pressure |
piston bar
(pressure unloading reacted
See.
to
A-A
vessel acting
on
piston by post)
Figure 21. - Special fixture for testing joint axial deflection.
stringent after the pressurized extension leakage. successfully tested.
tensile-pressure leak test was imposed. This test was an axial tensile axial compression and vectoring tests. The joint was sealed with internally, of the joint, In the
motor
passing
the pressure causing axial b_t pressure was still applied program,
this_ 'J_
leaky
_, no
joints
failures
were
attributed
pressure effective
is less than pivot point.
the motor Attempts
rejected
after
to joint
this test but,
failure
occurred
for those in the
simulating the test
The reduced pressure affects the position an unloading-piston test arrangement that
65
joints motors
end o£ the joint, is sealed _into the closure that is connected to an more axial load is applied to the
Therefore, joints are tested only up to a pressure will be applied to a joint in the motor. Consequently, pressure. to design
conducted plates and
extension. The test fixture limited the at maximum extension to check for any
A typical join t_iest arrangement is shown in figure 22. One test bucket and the other end is sealed into a flat-plate actuator arm. In this type of test, however, at test pressure joint than occurs in a motor. the maximum axial load that
test end
Of the vectors
/ /7 ,/
7 jr
Hydraulic
actuator
Load.cell
joint
1
Pressure
chamber
Figure 22. - Fixture for testing joint actuation under pressure.
_\
"\
with
the
pivot
point
joint but
have
been
must
allow
unsuccessful, the joint
because to vector
the freely
test about
arrangement its effective
must
not
pivot
point.
control
the
Proper location of the test actuator is important. It should be positioned in the test with respect to the joint as it will in the motor. Although joint spring torque is used as a design concept, the joint is not in fact subjected to pure torque. It has been shown that when the actuator was not oriented correctly to the joint, the vectoring response in the test was different A flexible
from joint
that
in the motor.
deflects
linearly
in addition
effective pivot point. Attempts have tracking one or two points on the mathematical model to determine the model does not include linear motion,
to rotating;
thus,
it is difficult
to locate
the
been made to locate the pivot point by digitally joint or joint test fixture and using a rotational instantaneous pivot point. Because the mathematical the results are inaccurate to some unknown degree
66
.......
that depends on been developed
the joint design. (ref. 91). This
directly on a photograph, thus measurements and avoiding instantaneous Most
bench
direct shows
eliminating the the dependence
photographic the position
method of the
of measurement effective pivot
has point
need to calculate the position from deflection of each calculated position on previous
positions. tests
environmental
of joints
are
temperature
85 ° F (303 K). The extremes is predicted 2.1.7.1.
2.1.7.3
A more method
STATIC
conducted
at approximately
requirements
usually
are limited
test temperature is recorded, from the elastomeric-material
FIRING
75 ° F (297 to the
range
and joint response characterization
K),
because
60 ° F (289
the K) to
at the temperature described in section
PROGRAM
During the static firing tests, measurements are taken to check the overall design and to obtain data needed to design other components that interact with the nozzle design. Measurements taken include axial compression, vectoring capability, nozzle misalignment requirements,
friction
characteristics,
The axial compression interact with another
natural
is required to check stage or equipment.
frequency,
and damping
coefficient.
the envelope requirements when the motor must During a firing, the nozzle'is vectored to various
angles up to the maximum required angle in order to check clearances between the fixed and movable portions and to check the movable nozzle envelope requirements. During this vectoring, actuator force is measured. For comparison of static firing and bench testing results, Sizing from
the nozzles
are vectored
of the correct actuator the static firing. During
at the
same
frequency.
length for nozzle misalignment (sec. 2.1.2.3.1)is determined a firing, at several times selected to give as wide a pressure
range as possible, the actuators are held at the trial length for at least one-half second. Prior to the firing, the nozzle is actuated in the motor, sufficient measurements being made to enable calculation of the vector angle per inch of actuator stroke. From a comparison of firing
and
actuator The
pre-firing length
friction
data,
the
for null nozzle
characteristics
amount position
of the
of zero-pressure at pressure
nozzle
(i.e.,
the
misalignment
is calculated
and
the
is determined. flexible
joint)
are required
for the
design
of the guidance control system. As noted earlier, friction consists of viscous friction due to the viscoelastic characteristics of the elastomer (a rate-dependent component) and coulomb friction (a rate-independent component). During static firing tests, a nozzle is vectored at different rates but at constant amplitude, and the actuator force is measured. The data are plotted as determined.
shown
in
figure
14. Both
total
67
friction
and
the
two
components
are
thus
Frequency-responsetests are madeduring a static firing by imparting to the nozzle a duty cycle that cdnsistsof a successionof sinusoidalactuations, eachof short duration andlow amplitude. These actuations are made at different frequencies established from considerationsof the control system response.Attempts havebeen made to calculate the damping coefficient from the decaying force transient that occurs at the end of a step function applied to a nozzle;however,the attemptswerewithout success,sincethe damping coefficient could not be correlated with the viscous friction coefficient calculated from actuation data.
DESTRUCTIVE
2.1.7.4
TESTING
The failure strength of a flexible joint is determined by destructive testing. Joint failure occurs as a result of motor pressure and vectoring. Currently, failure strength of a joint for combined conditions cannot be defined. A test is conducted in which pressure is increased incrementally,
the
joint
being
actuated
to the
maximum
applied
operation at each pressure until failure of a component occurs. the design ultimate pressure, and sufficient clearance envelope increased until failure occurs. The failure test is conducted testing
vector
angle
during
motor
If the joint has not failed at remains, the vector angle is as an adjunct to the bench
program.
2.1.7.5
AGING
In addition the joints
PROGRAM
to the
subscale
is conducted.
aging
Joints
program
are stored
described in the service
in section
2.1.7.1,
environment;
an aging at intervals,
program joint
for spring
torque and axial deflection (sec. 2.1.7.2) are measured. These tests are conducted at zero time (for reference), at 3 months, 6 months, 1 year, and annually thereafter. Most changes occur in the first year. The measured values for spring torque and axial deflection are plotted against life is compared
time; the results are extrapolated to determine joint with required motor life to demonstrate probability
life. This extrapolated of satisfactory service
life.
2.1.8
Inspection
The inspection of a flexible joint fabricated by injection or compression molding is difficult. No techniqugs have been successful in evaluating the quality of the elastomer or the quality of the adhesive bonds between the reinforcements and the elastomer in a molded joint. Assurance dimensional
of joint control
and adherence
quality of the
to acceptance
is obtained reinforcements, bench
by
control process
tests.
68
of the quality of all materials used, control during mold setup and molding,
For joints fabricated by secondary bonding, it is possible to check the pre-molded elastomeric pads for internal defects such as voids, inclusions and delaminations,and the bond between the reinforcement andelastomerby C-scanultrasonic techniques(ref. 22). In addition, joint quality is assuredby control of the quality of all materialsused,dimensional control of the reinforcements,and alignmentof the reinforcementsduring joint layup.
2.1.8.1 To
INSPECTION
ensure
reliability
PLAN of the
fabrication process program is conducted.
joint,
control This
a detailed
in conjunction program permits
timely repair and correction of these areas. resulting in satisfactory joints. Development following
and
comprehensive
with a detection
program
nondestructive of potential
Proper inspection of a successful
processes inspection
(2)
Evaluation of existing inspection techniques for sufficient and development of new acceptable or adequate techniques
(3)
Verification that the of the actual defects.
(4)
Establishment inspection
of the
of
both
INSPECTION practice
types
of defects
inspection
accept-reject
that
techniques
standards
require
detection.
obtain
for
a valid
each
sensitivity and accuracy when necessary. indication
type
of
or description
defect
and
is
any redundant inspection, modification of new inspections as knowledge
development
of and
existing experience
inspections, are gained
and production.
PROCESSES to
inspect
the
joint
dimensions
and
performance.
The
dimensions
inspected are those that affect joint molding, joint performance, and joint assembly nozzle. In performance inspection, the operational integrity of the joint is demonstrated. Reinforcement
each
technique.
Elimination of and introduction during
Current
are the key factors plan involves the
steps: Determination
2.1.8.2
and
and destructive test causes of failure and the
(1)
(5)
of material
dimensions
such
as inner
and
outer
diameter
and
flatness
affect
the
in the
joint
molding. The spherical radius, thickness, and concentricity affect the joint performance. The elastomer thickness and porosity can be inspected only by molding a joint without adhesive on the reinforcement surfaces. After molding, the joint is disassembled to check elastomer
thickness
and
porosity.
The
frequency
69
of
this
inspection
depends
upon
the
variation that is noted in the thickness.Radiographicinspectionhasbeentried, but the large amount of metal in the joint preventsdefinition of the bond line or elastomerthickness being defined to the required accuracy. After molding, the joint is dimensionally inspectedfor overalllength, concentricity between the end attachment rings, and end-ring to end-ring reference plane parallelism. These dimensionsaffect the overallposition of the nozzle with respectto the motor. The operational integrity of the joint is demonstratedby bench testing (sec.2.1.7.2). The significanceof thesetests is basedon the premisethat joints successfullypassingthesetests aresuitablefor assemblyin a nozzle. 2.2
LIQUID
INJECTION
Thrust' vectoring by LITVC of a rocket motor through
THRUST
VECTOR
CONTROL
is accomplished by injecting a liquid into the supersonic holes in the wall of the nozzle exit cone. The injection
exhaust produces
side thrust by a combination of effects that include the thrust of the injectant jet itself, pressures on the nozzle wall from shock waves, and pressures on the nozzle wall resulting from addition of mass and energy to the exhaust flow. These effects are illustrated in figures 23, 24, and 25. Liquid injection TVC has provided thrust side forces of 17.6 percent of axial force injectant for such
specific impulse large deflections.
spreading forces act
vector deflections as large as 10 °, equivalent (ref. 46). However, efficiency as measured
drops to about 30% of maximum at the The low efficiency at high flowrates
of the LITVC pressures around in directions different from that
to by
high flowrates required is due largely to the
the nozzle circumference, where local LITVC of the desired thrust deflection. Serious losses in
efficiency can occur if the higher pressures induced by LITVC reach the opposite side of the nozzle. This condition can be caused by very high injectant flowrates, by the injector being located
too
incomplete close to disperse
near
the
the
and mix
the
easily
added
the gain in side less-than-maximum The
maximum
efficiency
throat,
or
by
a combination
mixing and reacting of the injectant with the nozzle exit or from using large concentrated
As the injectant flow Then as the flowrate because
nozzle
(refs.
105,
106,
is increased, is increased
flow
and
forces
practical that
thrust must
on the opposite
deflection be
accepted
!
due
injecting that do
to too not
and usually reaches a maximum. decreases. This decrease occurs side of the
Thus,
maximum
angle
is limited
if the
70
1ii
Inefficiency
gas may result from injectant streams
force increases the side force
force on the injector side. flowrates (ref. 108).
penalties
both.
107).
the side further,
is creating
of
system
side
to
nozzle
force
about
is designed
that
cancel
out
can be obtained
6 ° because to
produce
at
of
the
larger
Discharge
angle
positive injecting
When upstream
Separation
Pressure or
Squib tank
valve
(for
Toroidal tank
regulator relief
shock
valve
_arated
boundary
layer
high-|
only) Gas
High-pressure
gas
tank Injectant
or
gas
mixing
generator
Injector Manifold
Gas
to
roll-control
surplus-gas
dump
nozzles (gas
or
gen. only)
Flow Burst
Figure
23.
- Schematic
of typical
meter
Bladder
liquid
injection
TVC
system
and
diaphragm
side
force
phenomena.
/exhaust-gas and
reacting
Nozzle
Shock (Wall Nozzle
pressures
exit
area increase
I00
to
60_/o
thr_ above may
normal be
as
nozzle high
static
as
507°
of
pressure chamber
and pressure)
%
Injection
orifice
_'_'_ jectant (Wall
mixture
pressures
0 above
Sheltered (pressures 40_
below
area
to 300_ normal)
B
area 0
to
normal)
A
o °r4 4J (U
A
,r4
/_/_
&J
"I
__Pressure
along
A-A
J" \
--
\._
_Pressure
....
along
B-B
"- "----..__
O ..4
,-4 i
CI Nozzle ,-4 N _q O
Injector Pressure
along
C-C
= > o
f_
Injector
Figure
24.
- Nozzle
pressure
distribution
due
?2 ¸
to
injection
of
inert
injectant
(ref.
104).
exit
i/
L
2
0°
kN/m2 621
10°
psi
105o _9
75°
i 0.15
90 _k--_30
552
80
483
7O
414
60
345
50
276
4O
207
3O
_
°
_:_:
_/_1 _._._/\
__
__!
I
__o_
,-4
"_.
--
o.10
0
k 03 o3
O_
I/O'°kXX_k
_-/--_
' __15
I't_ _,_
e_
e = 21.81 e= 2.86 Injection
69
3,2"
°
,, I,, ",,',x_, ' : __,_._---",.>/''_ :'_ _, I00o_\\\ \ ._oo_ _ ___.._/_/_
U
138
¢=
L___
70°_
i __
.
T--__
_ 0.o5
•
_
Centerline
20
I0 0.oo
0 .0
2.0
3.0
4.0
5.0
Expansion
Figure 25. - Nozzle pressure _stribution
6.0
ratio
7.0
e
due to injection of reactive injectant.
8.0
9.0
o
deflections. To obtain higher deflections, larger located nearer the exit to reduce the side-force efficiency injection Liquid
of the locations injection •
has
a number
advantageous fluid through also obtained.
of desirable
•
fluid
with
Long-term demonstrated. including tetroxide, days in
2.2.1
System
The
the
low
objectives
parameters performance
are unique,
sizes and
as follows:
by the axial component of component makes it doubly
systems have
surplus thrust is
rapid and can produce a signal-to-force This speed is the result of the fact that the liquid injectant, and friction, and the reaction
the of
instantaneous.
in a state contained
in clean
The
aluminum
of instant readiness sealed supplies of
has been injectants
tanks.
Design
consists of a tank of injectant, liquid injectant, under pressure
valves
controlling
flow
operate
of an LrI'VC
system-design
of injectant, injector storage tank, and
effort
a source of compressed gas, tubing, from the gas, flows through tubing
on receipt
flight-control subsystem. Basic design features LITVC systems are shown in figures 27 and 28.
injectors, type liquid injectant
orifice
system during flight by jettisoning is removed from the vehicle, extra
gas is almost
LITVC systems
and these must be above. Thus, the
for various
of which
valve pintle and drive parts, inertia and move with little
exhaust
storage of These
A typical LITVC system and injector valves. The injectors.
be used, mentioned
Freon 114-B2 and aqueous solutions of strontium perchlorate. Nitrogen one of the most highly reactive injectants, has been stored as long as 75 the Titan III system (ref. 47)i Dry N204 probably can be stored
indefinitely
vehicle different
some
main motor thrust is increased on the nozzle wall. This axial
to lighten the LITVC the injectors; as weight
all moving parts-the tank bladder-have
to the
features,
Liquid injection TVC is inherently very time less than 20 msec without difficulty.
the
must effects
system at all flowrates is compromised. Effects are presented in references 46, 108, and 109.
During vectoring, the the increased pressures
•
injectors limiting
are
of electric illustrated
are to establish
the
in
signals
from
figure
26.
number
location and injection angle, the type the method of pressurizing the liquid
and
and shape injectant.
the Two
type
of
of the These
are established in the system-design analyses such that required vectoring is achieved at minimum weight without violating imposed constraints (e.g.,
74
Gas
generator
igniter Gas
roll
wiring
control
Gas Inj ectant Gas
\
pressurization
generator Gas Gas-generator
igniter
supply
l
tanks
_
pressure Roll
lin_
regulator control
pressure Nozzle
Clamps
--.
Liquid
Section
w ve
and
relief
control lines
Three-pintle Section
A-A
equalizing Bladder
line Skirt
Liquid
injectant
Figure 26. - Basic design features in a LITVC system.
B-B
injector
gas
Nitrogen gas vent valve
fill
i."".::." Com_n injectant _,"• ;.' _,,-gas tank
...o...,'. r,_Compressed
and
and
nitrogen
.°".':°°; '...%'
,
_Injectant ,
TVC electrical distribution
_ tlnaJneC f:nttube
/
Illl I
TVC
box battery
_/
power
_
switch "_'_"_
i __ E lec tromech anic injector valve
Figure
_Manifo ai
27. - Schematic
transfer
_ ld
drain
In j ec tant
_Nozzle manifold
Pyr o sea i
of Titan
III
76
ullage-blowdown
LITVC
system.
_
.
| I
.or-gas
i
generator
Hot-gas
pressure
relief
valve I
I
_ _r
aft
skirt
I
No
Toroidal for
tank
liquid
injectant
(a)
Side
view
Manifold Injector
orifice
(These
"sticks"
out
the
of
liquid
seals are
nozzle
for distribution
blown at
motor
ignition) ector
valve
for liquid
injectant
zle
Injector
Freon
pressure
sensing
Heat
Hot-gas
relief
va Gas
generator
igniter Hot-gas
firing
generator
I
Motor
(b)
Figure 28. - LITVC
End
aft
skirt
view
system for Polaris A3 second stage.
77
unit
shield
envelope, evaluation
response). of the
injection
pressure
2.2.1.1
SYSTEM
To
optimize
weight,
and location
in the
of an optimization study and related parameters
and such
an as
nozzle.
OPTIMIZATION
an
bulk,
The system-design analyses consist performance of injectants, injectors,
LITVC
and
system
performance
for data
a particular from
design,
known
the
LITVC
usual
procedure
components
is to compile
and
from
selected
designs provided by manufacturers. These data then are generalized in empirical equations or curves. Schematic designs representing the design alternates (e.g., type of fluid, number of injectors, and injection location) then are prepared to serve as a basis for optimization calculations. These alternates are evaluated for performance, weight, and compliance to the vehicle space envelope. For each design concept, an overall vehicle performance parameter is calculated for use in numerical evaluation; and typically has been either the payload burn. The results of the choice, injectant amount, This initial optimization considered and injector location
this parameter depends on the vehicle mission or the vehicle final velocity at the end of motor
early optimization give preliminary number of injectors, approximate reduces significantly the number
simplifies the detailed and discharge angle,
studies amount
for injection of injectant,
determinations of the injectant system pressure, and so forth. of design possibilities to be
pressure, orifice size and spacing, and the system pressurization gas
required. As the detailed studies of these items proceed, the empirical equations are improved and the optimization is repeated as necessary to improve the results. A limitation changing
of LITVC the
design
that to
is important
accommodate
design requirements. If the system performance of which is known, requirements.
Usually,
however,
the
changes being then new
design, and data scaling has to be applied of overdesign. Also, systems usually are trajectory reasons,
in the
major.redesign and operating
period
in maximum
designed the new design
are
different
and angle of the injector valves after the initial design phase and
revised
items that most tubing, injector
in
or other
any
the the
previous
and the likelihood of the worst-case
downwards.
For
these
better linearity and jet carried in the tank, are they do not necessitate influence system weight valves, and the location
on the nozzle wall) are difficult and therefore usually are left unchanged.
78
force
from
uncertainties initial estimate
in particular redesign of pintle shape to provide flowrates and to reduce the amount of injectant are made late in the development period because
and additional tests. However, the efficiency (sizes of tanks, brackets,
side
of flexibility
similar to an earlier design, can be designed close to
is significantly
estimates
is lack
required
is very system
with the attendant sized to meet the
requirements. Later these initial most systems in use are oversized.
Minor corrections, formation at lower changes that often
development
and curves preliminary
expensive
to redesign
Oversizingis minimized by repeating the optimization procedureas late as possiblebefore the systemdesignconcept is frozen. Corrected designand performance data are used, and the flight-control vectoring requirement is reviseddownward, if possible,usually by better definition of trajectory events. Thus, the more realistic the inputs in the optimization : procedure,the more nearly correct and usually lighter weight is the final systemdesign.
2.2.1.2 The
SELECTION
chief
impulse, tetroxide
OF INJECTANT
factors
considered
density, storability, and and an aqueous solution
Freon 114-B2, and operational injectants Side
in the
specific
selection
of the
liquid
injectant
toxicity. Prime candidates of strontium perchlorate;
for other
hydrogen peroxide. The basic properties are presented in table IX and discussed
impulse.
Side
specific
impulse
its
the injectant candidates
and below.
is a measure
are
side
are nitrogen are hydrazine,
characteristics
of the
specific
vectoring
of major
power
of the
injectant and is defined as the side force, lbf (N), divided by the injectant flow rate, lbm/sec (kg/s). Reactive injectants have larger side specific impulses than inert injectants. Inert injectants to 1569 solution
or
specific angles
such as Freon 114-B2 deliver N-sec/kg), while chemically nitrogen
impulses less
tetroxide
of
than
180
to
(N204)
300
0.5 ° in Titan
400
side specific impulses of 70 to 160 lbf-sec/lbm (686 reactive injectants such as strontium perchl0rate
lbf-sec/lbm
(1765
III
configurations,
(3923
N-sec/kg)
greater
than
specific location,
impulse depends on how well the design size and spacing of injector orifices,
injectant-stream Density. and
lbf-sec/lbm
significantly
are
more
to 2942 side
have
effective,
N-sec/kg)
specific
been
delivering or more.
impulse
recorded.
values
The
At for
actual
is optimized with respect injection angle, injection
side TVC N204
delivered
to the injector pressure, and
characteristics.
- Injectant
injectors
density
required.
is a major
Storage
space
influence on
on the volume
some
vehicles
has
and been
weight
of tanks,
sufficiently
preclude use of a low-density injectant. Even when storage space was available, larger tanks, piping, and injectors imposed a weight penalty that eliminated injectants from optimization studies. For this reason, the densities of injectants
piping,
limited
to
the required low-density used usually
have been approximately twice that of water. The high density has made it possible to store the injectant in compact tanks and permitted use of relatively small tubing, valves, and injectors. Thus, both weight and space on board the vehicle have been saved. ,
?
Storability.Storability of a liquid expected storage temperatures and materials it contacts. It is the measure LITVC
system
in a state
of
readiness
depends pressures of the over
both on the stability of the fluid under and on its compatibility with the tank capability of an injectant to be stored in the
long
achieved by controlling the purity of the injectant not react with the injectant and that contains reactions.
79
periods
of time.
This
condition
and by providing a tank material no trace elements that could
usually
is
that will catalyze
TABLE IX. - Basic Properties and Characteristics of Main Operational Liquid Injectants
Injectant
//
Property or characteristic
Freon 114-B2
Side specific impulse, (t) lbf-sec/lbm
70 to 160
Density, Ibm/ft 3
134.5
Freezing or crystallization point, °F
-31
Stability in storage
Reactivity metals
with
Strontium perchlorate (solution in water) ,'
Nitrogen
tetroxide
150 to 260
180 to 400
124.5, 62% solution 126.1, 72% solution
90.0
32, 62% solution 50, 72% solution
12
Very stable; nonflammable.
Solution
Stable if dry and without
sealed storage
impurities.
Inert in absence of water.
Noncorrosive to stainless steels and aluminum.
Noncorrosive in absence of water to stainless steels and aluminum
/
/
is stable in
oo O
(ref. 110). Stress corrosion with titanium (ref. 111). Reactivity
with
polymers
Penetrates
and deterio-
rates polymers.
Almost no effect on elastomers
problem
Most elastomers are incompatible with N 204 for long-term storage;
and most
other polymers (ref. 110).
some disintegrate in hours, others in days. Only nitroso compound AFE-110 and Parker compound B-591-8 are acceptable for 90-day storage (ref. 112).
Harmless on contact.
Toxicity
Fumes harmless in moderate amounts.
Solution has low toxicity. No problem with good housekeeping. Dry perchlorate is moderately toxic and irritating
Severely burns skin and eyes on contact. Inhalation of fumes can be fatal.
to the
skin. Vehicle on ,which injectant
is used
Polaris A3 second stage; Minuteman II second
Minuteman ili third stage (66% solution)
stage; Sprint first stage.
(I) Basedon test data for which injection location in the nozzle and injector geometry wereclose to optimum.
Titan I11
Studies
have
been
conducted
to
determine
the
compatibility
of
liquid
various materials (refs. 111 through 119). The results of one such study table X (ref. 120). As shown, Freon 114-B2 is almost completely
injectants
with
are summarized in inert with metals;
however, it should not be stored in metallic materials subject to corrosion, since any water contamination causes hydrolysis and subsequent corrosion. Freon 114-B2 does not affect Teflon materials but does permeate various elastomers, thermosets, and thermoplastics; it leaches plasticizer from the plastics, making them hard and brittle. Both N204 and Sr(C104)2 are reactive. Strontium perchlorate must be contained in stainless steel or titanium storage tanks. It is stable and safe at 350 ° F (450 K), but at higher temperatures it decomposes 811 K), reaction
and
storage
pressurization
temperatures,
Nitrogen
rocket
and
.gives
the
highest
or
percholorate
side
makes purity
range
for
to 1000 ° F (755
all reactive
for any
specific
to 900
crystallizing
of the
impulse
of
liquids.
liquids the
in a 62%
injectants
temperature
solution
In
comparison
that
are
and in readiness at operational pressure tetroxide has been selected for use in the
control is
of N2 04 has been
the
system. limiting
low
temperature
for
storage.
not occur either in Freon or nitrogen tetroxide. Freon K) and N2Oa freezes at 12 ° F (262 K). Strontium
with
with
here.
occur. Elastomeric materials cannot be used for and storage requirements are well established in the
water
crystallizes
out
of the
solution
at 32 ° F (273
- Nitrogen tetroxide burns on contact, and inhalation of fumes Freon 114-B2 is harmless on contact and its fumes are harmless
amounts.
At normal
mentioned
it difficult to handle. It can be stored successfully and container inertness are met; otherwise,
III post-boost
does (238
K to
with rubber that an almost explosive end of the duty cycle in systems with
problem
a problem
for up to 75 days 47 and 114). Nitrogen
Crystallization or separation 114-B2 freezes at -31 ° F
Toxicity. whereas
is not
for the Minuteman
freezing
the
present significant problems. The current practical storability in Titan III operational practice, where the LITVC system
to remain loaded a 30-day hold (refs. engine
is a potential
and degradation will Handling precautions
and do not demonstrated
Within
combines so readily has occurred near the
reactivity, however, requirements for
decomposition long-term seals. industry has been
oxidizer.
decomposition
tetroxide
operational;its only if strict
approved through
a strong
strontium perchlorate occurs. This reaction
gas-generator
The
becomes
Freon
114-B2,
strontium
perchlorate
K).
can be fatal, in moderate
delivers
50%
more
specific impulse, costs half as much, and involves fewer compatibility and storage problems. However, strontium perchlorate is moderately toxic and irritating to the skin. Care must be exercised to prevent the these saturated materials
2.2.1.3
INJECTION
In a typical formed by
perchlorate would burn
PRESSURES
LITVC system, the a convergent round
salt or solution from rapidly if ignited.
AND
INJECTION
saturating
clothing
or wood,
since
ORIFICES
liquiffis injected into the nozzle through an annular orifice outlet with a central pintle, as shown in the injector cross
81
TABLE X. -
Compatibility
of Selected
and Aqueous Strontium
Metals and Nonmetals
with Freon 114-B2
Perehlurate (ref. 120)
Materials Tested Metals
oo t-o
Nonmetals
Ti-6A 1-4V
Hypalon
4130 steel
Neoprenes
4340 steel
Polyvinyl
7505 aluminum
Thiokol ST (polysulfide)
2024
Viton
aluminum
CN and W alcohol
"A"
347 stainless
steel
Tygon ST (polyvinyi
Molybdenum
steel
Teflons
Results after 3-week exposure
Freon
Material
Metals
20
1,6, and 100
at room temperature
114-B2
No visible effect
chloride)
Sr (C 104)2
on any metal.
4130
and 4340
steels showed
some rust; other metals showed no visible effect.
Nonmetals
All specimens showed
except the Teflons
signs of permeation
deterioration.
Significant
of liquid indicates problems.
and pickup
permeability
Polyvinyl
alcohol and Thiokol
showed signs of chemical
ST
reaction
and deterioration; other specimens showed no visible effect. Pickup of liquid was negligible.
sections
in figures
29,
30, and
31. The
central
pintle
acts
as the
gate
of the
injector
valve.
Thus, the full system pressure is applied to the liquid up to the point of discharge through the orifice. The injection pressure, orifice size, and orifice spacing have a significant influence Injection through
on side-thrust
efficiency
system pressure the orifice with
because pressures 121, and
compexity. force best
that drives the liquid side-thrust efficiency.
from 450 to 1500 psi (3.10 to 10.34 MN/m 2 ). Analysis of test firings with LITVC indicates that for maximum side-thrust
injection pressure (ref. 121). Such
these pressures are used, the
system
is important because it provides the the high momentum needed to obtain
System pressures in use range data from small-scale motor efficiency the rocket motor
and
should be set at about high pressures may not
also influence the weight probable loss in side-thrust
twice the chamber pressure be optimum for the entire
of the system
of tanks, tubing, and injectors. If lower efficiency can be estimated (refs. 108,
122).
Efficient development of side force by fluid injection depends mainly on rapid mixing and chemical reaction of the injectant with the hot exhaust gas close to the wall This complex process involves droplet shattering, evaporation, and nonequilibrium chemistry. It should be noted that practically all injectants decompose and react chemically, including the so-called inert injectants, although for these liquids the energy this process and the effects that compose it are found For most efficient fully reacted with
development exhaust gas
released is small. Analytic models of in references 105, 106, 110, and 123.
of side force, the injectant should be thoroughly mixed and in the immediate neighborhood of the wall. For thorough
mixing, the liquid jets should have the highest possible However, to prevent the high-velocity jets from passing
momentum and therefore velocity. out of the immediate neighborhood
of the wall and penetrating too far into the gas stream, where their effects would be lost, the individual jets must be made so small that in spite of their high momentum they will have broken up and become mixed with the gas while still close to the wall. At all flowrates, the momentum per unit mass of liquid discharged remains about the same, since it is dependent on the pressure of the injectant in the system. This momentum contributes to the LITVC effect
by
partially injectant For
delivering
a force
against
the supersonic
stream
that
produces
the initial
shock
and
from
the
diverts the direction of flow. The balance of the LITVC effort results and its reactions producing higher flow pressures acting against the wall.
a well-designed
pintle-type
injector
(figs.
29
and
greatest side-thrust efficiency is obtained at low because at low injector openings the jet maintains discharged but the annular jet stream has a thin
30)
having
a given
orifice
flowrates (ref. 108). This effect occurs the usual high momentum per unit mass section, so that it mixes efficiently and
penetrates only into the gas that is closest to the annular jet increases in thickness, so that it penetrates
wall. At high flowrates, much more deeply into
stream, thereby must be applied
the
carrying the to be useful.
injectant
farther
83
from
size, the
wall
to which
the
however, the nozzle pressure
the gas
effects
Pintle
Erosion resistant insulation_
Injector valve
body
0
%
mechanism and hydraulic valve.operatol Nozzle
Figure
29. - Cross
section
drawing
Passages
of typical
for
fluid
single-orifice
that
powers
injector
mounted
on nozzle
injector
_njectant inlet
Orifice Pintle Nozzle
Figure
30. - Cross
section
drawing
of three-orifice
84
injector
wall
mounted
on
nozzle
wall.
wall.
Ball
screw
helical
bearing IX:
electric
torque field
Injectant
motor
inlets
J
5
/ i Pintle
position
transducer Injector
mount
Figure 31. - Cross section drawing of an electromechanical injectant valve.
Side-specific-impulse openings (ref. 108) The drop advantageous
in
efficiencies have an upper limit at very small orifice because increasing orifice friction reduces jet momentum
efficiency that occurs with to use a large number of small
large flow from orifices. The flow
jets, ,so that in spite of the great flow momentum the main stream; instead, the jets break up close the gas, vaporizes, and reacts to release energy The
large
Increasing
number the
of injectors, number
however,
of injection
add
ports
a single is divided
sizes and valve per unit mass. orifice among
the liquid does not penetrate to the wall, where the injectant that produces higher pressure
to the increases
complexity the
and
injection
the
makes it individual
deeply mixes on the
into with wall.
cost.
efficiency,
provided
that
overlap losses and cosine regions of shock pressure, not the sum of influences
losses are not excessive. Overlap losses result from the overlap of mixing, and reacting. In these regions the local pressure increase is from two separate orifices but a lesser amount, greater however
than
alone
that
for
one
orifice
(refs.
of the LITVC wall pressures around potential side force to be lost because
108
and
124).
Cosine
losses
the nozzle; this spreading opposing force components
85
result
from
the spreading
causes a portion of the cancel. These losses are
called cosinelossesbecausethe local LITVC force is diminished, for TVC purposes,by the cosineof the anglebetweenits direction andthe desiredside-forcedirection. The basic the rocket acting
liquid injection configuration has four nozzle for positive and negative pitch
between
the
simultaneously, and from these injectors.
pitch
and
yaw
planes
or more injectors and yaw control.
require
that
several
spaced Needed
equally control
adjacent
around forces
injectors
flow
the resultant force is obtained by vector addition of the control forces The use of more than four injectors (e.g., six, twelve, or twenty-four
injectors equally spaced around the nozzle) decreases the amount of fluid required, because the injectors that must provide a given control force will more likely be located closer to the direction of the required force; with more injectors flowing simultaneously, each injector will deliver
less flow
The predicted number, and
and
therefore
response of the spacing is reduced
optimization calculations contained in references 47,
2.2.1.4 The
INJECTOR
injector
AND
on the
higher
side-thrust
efficiency.
system to changes in injection to curves and equations for
(sec. 2.2.1.1). 121, 125, and
LOCATION
is positioned
will have
Examples 126.
of
DISCHARGE
nozzle
pressure or in orifice size, use as inputs in the system
such
curves
and
equations
are
ANGLE
wall (fig. 23)
at a location
and
a discharge
angle that
is optimum for the location for injection from the side force.
expected schedule of vectoring for a typical flight. The optimum is a compromise of two opposing tendencies that add to or subtract If the injection point is as far upstream in the nozzle exit cone as
possible, increased.
wall area over as the injection
the nozzle However,
injectant-augmented
portion
of the
which point flow
the pressures are augmented by injection is moved upstream, the shock wave of
spreads
out
around
and
across
the
nozzle
is the
until
it
produces a pressure on the opposite half of the nozzle that subtracts from the desired side force. This cross-interference tendency increases with rise in the ratio of injection flowrate to motor flowrate. For a very low injection flowrate, the optimum injector position on the nozzle the
wall
optimum
126). The at which expenditure
is upstream position most the
and
relatively
is downstream
close
to the
from
favorable injection point total required program
the
throat
but
nearer
for larger the
nozzle
injection exit
flowrates
(refs.
for a particular motor is an intermediate of thrust vectoring is accomplished
107 and
location with least
of liquid.
:The injector discharge (fig. 23) usually is directed 25 °. The 25 ° angle has been found to be optimum Pointing between
throat,
the liquid the exhaust
upstream at angles ranging from in subscale tests (refs. 108 and
jets upstream produces several effects. gas and the liquid jet shatters the droplets
The greater to a smaller
0 ° to 109).
relative velocity size, thus aiding
evaporation and mixing. The injectant is delivered slightly upstream of the injection point, an effect equivalent to moving the injection upstream by that amount. Directing the fluid
86
j_
jet upstream along the wall reduces the depth of penetration of the jet and keeps the injectant mixture and its higher pressures nearer the wall, where they will produce more side force. If the jet is directed too close to the wall, at angles appreciably greater than +25 ° , the beneficial effect of better mixing and improved positioning of the resulting higher pressure region is more than cancelled out by losses (ref. 125). These losses probably result from a reduction in the useful component of the injectant jet reaction force, loss in momentum of the
main
gas stream
momentum The
due
to more
in the injector
optimum
injection
due
direct
opposition
to the larger
location
usually
by the fluid jet,
diagonal
is closer
passage to the
and greater
through
throat
loss of fluid
the nozzle
than
to the
wall.
exit,
with
a value
of optimum X/L _ 0.3 being typical (X = distance from throat to the plane of the injector ports, and L -- distance from throat to exit plane). Motors with submerged nozzles do not permit injection at the optimum location, and a performance penalty is thus imposed. For the Poseidon consideration
C3 motors, the penalty was so as a TVC system, and the flexible-joint
The injection location parameter location, can be misleading when phenomena that divergence angle, LITVC effect. Since their
cause shock
In the usually
effects of injector 108, 122, and 125.
OF LIQUID
system optimization calculations, indicates the relative efficiency
amount
of liquid
the
largest
item
and
from
for specifying injection indirectly related to the
including are more
influence the calculations
location
INJECTANT
convenient it is only
parameters dimensions
angle of injection strongly in the system optimization
curves presenting the contained in references
AMOUNT
while simple and in design, because
the side force. Other angle, and mixing-path
the location and effect is included
2.2.1.5
X/L, used
large that LITVC was eliminated TVC system was adopted.
the expansion directly related
ratio, to the
LITVC side-force efficiency, (sec. 2.2.1.1). Examples of
angle
on
side-force
efficiency
are
REQUIRED
the amount of liquid required is the parameter of each design concept considered. Not only
of weight
that
must
be carried,
but
it determines,
that is the
through
its equvalent volume, the size and weight of the tubing, injectors, and tankage. The latter is usually the heaviest item of inert weight. Thus, the system design conceptJthat requires the smallest amount of injectant liquid usually is the one shown to be gtOst desirable by the optimization calculations. JJ The
amount
of liquid
very conservative of maximum extremely the flight
method expected
unlikely, including
required
depends
on
the
required
for calculating the amount vectoring requirements.
vectoring
of liquid Statistically,
since it provides for the most unfavorable the most irregular launch or separation,
87
program.
uses type the
the such
A simple
worst combination a combination
but is
of event at every stage of most severe weather and
wind shearsat all altitudes, the most eccentricpossiblealignment of vehicleweights,andthe greatestnozzle misalignment.The statistical oddsfor this worst combination usually is very small, typically lessthan 1 in 100000. This "worst-on-worst" method generallyhasresulted in overestimatesof the total side impulse required and in design of systemsthat carry grosslyexcessiveamountsof liquid. Sometimes,after flight experiencehad revealedthis fact asin the Polaris A3 program,the amount of liquid loaded in the tank hasbeenreduced,but useof an oversizedtank continued. A better method of determining the amount of side impulse and therefore the amount of liquid required for vectoring employs statistical techniquessuchasthe Monte Carlo method (refs. 47, 127, and 128). By this method, the amount of liquid required is determinedasa function of the probability that the vehicle will not run out of liquid before the vehicle operation is completed. The calculation considersa random probable requirementfor each separatepart of the vectoring program and sums eachpart to obtain the total amount of injectant required. The calculation is repeatedmany times to develop a statistical basisfor the amount of liquid to be carried. Preliminary estimatesof total sideimpulse required for vectoring have been obtained by assuminga side force of 0.02 of total axial impulse for first-stage motors, 0.01 of total axial impulse for second-stagemotors, and 0.006 of total axial impulse for third-stagemotors. In addition to the liquid that is neededfor vectoring, liquid is carried for ullage, filling of pipes andvalves,andvalveoperation; someinjectant is lost when valvesoperate,becausethe valves cannot open and close instantaneously. This unusable liquid is minimized by designingthe tank, bladder, piping, and valvesto avoid trapping liquid and to haveonly the flow volume required. Also, some valvesleak becauseof imperfect contact between the pintle and the valveseat.This leakagecanbe minimized and with good designshould be too smallto be included in establishingthe amount of liquid. The total required storage tank capacity thus includes'the liquid for vectoring plus the "unusable" liquid required for ullage, systemfill, valve operation, and possibly leakage.A typical procedurefor determining the total amount of liquid is asfollows: (,1) The
\
vectoring
requirement
is determined.
form by deflection angle and time; second, and 0.5 deg for the balance
Preferably
it is developed
e.g., 3 deg for two seconds, of the flight time. For each
1.5 deg for one deflection angle
the required side impulse is equal to the axial thrust times the deflection angle times the time required for this amount of deflection,
\\\\\,
the the
total latter
to estimate (2)
Curves scaling
in itemized
sine of the Sometimes
required side impulse and an average deflection angle are specified. In case, the maximum deflection angle is also specified, since it is needed the
injector
of estimated and replotting
size and
location.
side specific impulse versus deflection angle are developed by available data (refs. 46, 108, 109, 121, 124, 125, and 129).
88
(3) The liquid needed for vectoring each specified deflection angleis calculatedby dividing the side impulse required by the side specific impulse indicated on the curve developed in (2). The amounts of liquid thus determined for the various required anglesarethen summed. (4) The amount of additional liquid required for ullage,filling similar needs is estimated calculations, this amount liquid.
2.2.1.6
AMOUNT
of piping,
leakage,
and
and added to the above usable amount. For preliminary is sometimes estimated at 10 percent of the total usable
OF PRESSURIZATION
GAS REQUIRED
The liquid injectant in the system is kept under high pressures by gas that acts on the liquid in the tank either through a bladder (fig. 23) or piston or directly (fig. 27). The supply of compressed gas is made large enough so that when the liquid is expelled from the tank at the largest expected flowrate, its displaced volume is filled by fresh gas at a flowrate and pressure
sufficient
to ensure
that
the
system
pressure
does
not
fall below
its required
level.
The amount of gas that must be supplied to pressurize the LITVC system 'during operation usually is determined in the final evaluation of a system concept, the pressure the system and the amount of liquid to be injected having already been established. If the
LITVC
to expand pressure 2.2.1.3). required
system
into
the
is to be pressurized volume
occupied
by
by inert the
gas, only
displaced
the exact
injectant
must
amount
its of
of gas needed
be provided.
The
final
should, of course, not be less than the required injection pressure level (sec. If pressurization gas is to be generated by burning solid propellant, more gas will be than that needed for liquid displacement. The amount of gas required is the
maximum expected gas demand rate integrated over the operating time. This demand determined from the maximum expected injectant flowrate, which in turn is obtained the "worst-on-worst" severe vectoring requirements taken at all times through the operating
rate is from motor
time.
If a vectoring program requires only occasional side forces of short duration but large magnitude and if these can occur over a wide time span, the required amount of generated gas can be very much greater than that required to displace the ejected injectant. In some cases, this excessive required amount volume to act as a gas accumulator. compressed
2.2.2 The
inert
system
of the
concept
reduced by taking advantage of excess tank cases, it has been found to be better to use
gas.
Component design
has been In other
has
Design
components been
of the
developed;
i.e.,
LITVC after
89
system the
is begun
injectant
after
has been
the
optimum
selected;
the
LITVC injection
location, angle,maximum flowrate, orifice size and spacing,and systempressurehavebeen determined;the amounts of injectant and pressurizationgashavebeen calculated; and the approximate envelopeavailablefor the componentshasbeen checkedandbeenfound to be reasonablyadequate.Component design,asconsideredin the following section,includesthe detailed design of the LITVC systemas well as adaptation of the rocket motor for LITVC. The componentsof a typical LITVC systemarethe injectors, fittings and piping, tanks with or without bladders, gas supply for pressurization,meters to equalize tank drainage,and provisions for disposal of surplus injectant. The complete LITVC assembly usually is mounted around the nozzle on brackets that attach to the nozzle or the aft end of the motor. Erosion may be moderate or severeat the injectant holesin the nozzle wall, and this area may require special insulation and structure. Also, some form of heat barrier or insulation usually is required to protect the LITVC components from the heat of the exhaustplume.
2.2.2.1
INJECTORS
The injectors streamlined
are automatically operated discharge port, so that full
valves in which injection system
the valve closure is located in a pressure is effective close to the
point of release; thus high hot-gas flow in the nozzle
discharge velocity is imparted exit cone. The design of the
efficiency. A good injector velocity in order to impart
injects liquid in a linear, nondiverging jet at the highest possible high momentum to the fluid jet so that it interacts forcefully on
the
thereby
supersonic
dispersion, A range
gas
and of
stream,
mixing
sizes
and
causing
a shock
types
Variable-orifice injectors. become the most widely applications This
to
vehicle
-
of
injectors
is available
The variable-orifice used because of its
flight-control
are summarized
injector
has
a pintle
in table gate
is approximately cone-shaped, the ahnular orifice. Injector Supply piping flow resistance,
wave
and
liquid injected into the critically affects LITVC
maximum
droplet
breakup,
(fig. 23).
injectors have been designed for use on various or considered as the means of vectoring.
adaptation
to the injector
that
systems.
rocket
injector operating Design
from
control-valve
motors
for which
(figs. 29, flexibility features
of
suppliers. LITVC
was chosen
30, 31, 32, and and consequent this
These
33) has ease of
injector
in various
the
The
XI. moves
so that discharge
axially
in the port
to throttle
flow.
pintle
when moved into the exit throat it reduces or closes can be modulated from almost zero flow to full flow.
and passages usually are sized so that even at high flowrates
large enough to avoid pressure losses due to full system pressure reaches the liquid in the
injector valve and drives the jet through the orifice and into and pintle of the injector are designed with streamlined efficiently accelerated into a narrow, high-velocity stream.
90
the nozzle. The orifice approach contours so that the flow is The injector pintle is controlled
Servo
_o
6) _I_
_
_
_
_
\
Electrical
L__pSri!!!ye_
line I
.....
Control
Control valve
pressure line
kO
Feedback transducer Injector Nozzle
valve
not
shown
Actuator piston
Figure
32. - Injector
valve
assembly
with
hydraulic-powered
actuator.
_
Pintle
!
Hydraulic
Pintle
actuator
t ransducer
location
;. "
/
•
Injector
t
2
_D bO Electric i;:|
•
feedback
i/_J Injectant
i!i_ 1
Servo
torque
motor
)ply
i:;!
_:,1 i;I
Hydraulic control
valve
Control fluid
L .....
Note:
Liquid is
used
injectant as
control
fluid Electrical Liquid
Figure
33.
- Servo-controlled
injectant
hydraulic
power
connectors
supply
systems
for
variable-orifice
injectors.
TABLE _1.
Number Motor
of nozzles
Polaris A3 second
Minuteman _D
second
Number of
Number orifices
injectors
per injector
8
stage
- Chief Design Features
of
of Variable - Orifice
Angle of
Injector
injection
weight,
(fig. 23)
Ibm
25 °
4.4
(2 per nozzle) I1
on Operatioml
LITVC Systems
Operating Type of actuation
Electro-
Response
time,
Flowrate,
pressure,
lbm/sec
psig
deflection,
12.
750
0.230
60.
620
0.120
12.5
680
0.080
131
400.
800
0.022
50
signal to full
References
see
48
hydraulic
5.2
0 °
stage
Minuteman
Injectors
Electro-
49,113,130
hydraulic III
20 °
4.0
third stage
Electromechanical
Sprint
0
11.0
°
Electrohydraulic
Titan
II1
156-Inch
24
24
0 °
24.0
Electromechanical
100.
750
0.190
0 °
25.0
Electro-
158.
750
0.400
hydraulic
Note: The first five systems listed are operational; the last was tested in a development
program.
46,128,132
133
by a mechanism that provides signals from the vehicle flight
variable control.
control of the injector flow on command of electrical The control signals may be analog (variable voltage)
or digital. The valve motor may 'be electric, hydraulic, or both. Usually it is electro-hydraulic (table XI). In this case, the valve operation is controlled by a servo mechanism in which an electrically operated pilot valve is used to admit pressurized hydraulic fluid to move the valve closure or pintle injectors usually have
and thus to modulate the three orifices and pintles
orifices and pintles have electro-hydraulic systems, operate
the injectors
In
Titan
the
III
electro-mechanical
been designed the pressurized
(figs. and
32 and
NASA
actuators
flow (figs. 29 and (figs. 30, 32, and
and presumably injectant is used
system
Fixed-orifice
(ref.
could be to provide
fabricated. hydraulic
In some power to
33).
260-in. (fig.
(6.6
31).
m)
Adc
systems,
electric
the
motor
pintle position is sensed by a linear potentiometer connected adjusts the dc current so that the pintle position matches control
30). The servo-operated 33). Injectors with five
injectors
moves
the
are
operated
by
pintle
axially.
The
to an electronic the command
controller from the
that flight
47).
injector.
-On-off
fixed-orifice
development programs and have been been developed to operational status
injectors
proposed for any
have
been
tested
in various
LITVC
for use, but to date no on-off system has solid propellant motor and only one for a
liquid propellant engine (Lance). The two potential advantages of the on-off injector are high efficiency and light weight. The high efficiency is obtained if the valve gate or pintle is withdrawn fully from a countoured orifice so that the flow of liquid is not obstructed by the pintle but is accelerated and orifices must be made sufficiently
interacts small
wall
produces
where
mixing
from the modulation. (2.59 The
and
reacting
simple two-position (The Lance injector
kg/sec)
of hydrazine
disadvantage
of
greatest
wall
actuation that weighs 1.1 lbm (0.50
at 900
on-off
with the gas with maximum force. The size of the so that the jets break up and disperse close to the
psi (6.21
fixed-area
LITVC
frequency
is set outside
the
move
the
the injector The electric
injector
pintle
actuators
ranges
into the nozzle, signal is almost takes
the
flow begins when the pintle first Time for the liquid to accelerate reacting
of the
injectant
with
the
most
is that
that
weight
results
for flowrate of 5.7 lbm/sec
can be made the actuator
side-thrust
modulation
must
The resulting force pulses problems in the vehicle
can cause
time,
trouble. very rapid. The four events included pintle movement,, the movement of
typically
gas is very
94
be
produce a unless the
and the mixing and reacting of injectant instantaneous. The time for the actuator
opens and accelerates to full flow varies nozzle
light
MN/m 2).
Response time. - LITVC system response in response are the electric vector signal, liquid through in the. nozzle.
The
requires no feedback kg) and has a flow rate
accomplished by varying the length of the flow pulses. vibration effect that can cause structural or operating ,,
pressure.
15 to 200
milliseconds.
as the pintle completes from 1 to 10 msec. The
rapid,
ranging
from
less than
with gas drive to The
liquid
its motion. mixing and 1 msec
for
average-sizemotors to 2.5 msec for large motors time
is the
approximate
sum
of these
times
(note
such that
as the Titan III. The total response injectant flow and pintle movement
times overlap) and can be as little as 22 msec (ref. 139 and table time can be obtained by reducing the mass of the pintle, increasing and increasing the injectant pressure. Supplemental just upstream to malfunction.
injector hardware. - Screens of the injector to catch any
In some cases, closures storage or after system
are used activation
usually are installed pieces of solid matter
XI). A shorter response the pintle drive force,
in the liquid-supply piping that might cause the valve
at the injection orifices to prevent loss of liquid during but before motor ignition. For example, the Titan III
LITVC system is designed to be capable of being held at launch readiness for up to 75 days. The stored liquid is allowed to fill the entire system and is sealed from leakage loss at injector outlets by pyroseals sec after ignition (ref. 47).
2.2.2.2
STORAGE
The chief summarized The
liquid
TANK
AND
design features in table XII. injectant
is
(fig. 27).
of
Pyroseals
are fluid-tight
plugs
that
burn
off about
1/4
systems
are
BLADDER liquid
stored
storage
in one
or
systems
more
for
operational
spherical,
cylindrical,
LITVC
or
toroidal
tanks
typically made of stainless steel, titanium, or aluminum. Each tank usually is connected: to a system supplying compressed gas to pressurize the liquid. The gas may be cold and inert, usually nitrogen, or hot and reactive if generated by burning solid propellant. A membrane liquid and
or bladder prevent the
usually is used in each tank to keep the gas separated gas from mixing with, exchanging heat with, reacting
bypassing the fluid. It is advantageous and eliminate a development problem. and the liquid injectant are compatible tank outlet compressed
from the with, or
to eliminate the bladder if possible to reduce weight The bladder can be eliminated if the pressurizing gas and if the liquid is positively positioned over the
as in the LITVC system of the Minuteman helium to pressurize strontium perchlorate
III third stage. This system solution in a spherical tank.
uses The
gravity and acceleration forces apparently are sufficient to hold the liquid over the tank outlet. The bladder usually is a laminate of strong flexible plastic and fiber materials coated with an injectant-resistant material. Typically the internal fiber web has provided the needed mechanical strength and the facing side and an inert permeable seal bladder development, because the been critical to blow by
to the success the liquid and
plastic layers have provided thermal insulation on the gas on the liquid side. Much effort has been expended on dependable separation of liquid and pressurizing gas has
of most systems. enter the piping
95
A ruptured bladder may allow to the injectors, thus causing
pressurizing gas loss of control
TABLE XH.
Liquid
Motor
injectam
Polaris second
114-B2
Chief Design Features
Injectant density,
Amount of liquid
Liquid tank
lbm/ft 3
stored, Ibm
material
134.5
200
Aluminum
of Liquid Storage
Tank shape
third stage
Separation
on Operational
between
Toroidal
Bladder(Viton reinforced
LITVC Systems-
Source
of
pressurization
Initial
Surplus liquid
gas pressure,
jettisoned into nozzle during
psia
flight
Gas generator
NA
Gas generator
NA
Composed
3320
Yes
Dry weight of LITVC system,
139
with
Dacron)
!i
Freon
114-B2
134.5
259
Steel
Toroidal
(17-7PH)
stage
Minuteman
Systems
gas and liquid
stage
Minuteman second
Freon
A3
-
Bladder (Viton AVH reinforced with
111
Sr(Cl04)2 (62% solution
124.5
49.3
Ti-6AI-4V
Spherical
Yes
228
Dacron)
None
helium
No
42
gas
in H20 )
Sprint
Freon
Titan II1
N2 04
114-B2
134.5
160
Stainless
221
Piston
Gas generator
NA
None
Compre_ed
11O0
Yes
Cylindrical
7054
55O0
No
8808
steel
90.0
8424
Stainless
nitrogen
steel (41 O)
156-Inch
No
Cylindrical
N204
90.0
8170
Stainless steel
Cylindrical
Bladder (stainless steel and chlorobutyl rubber)
Notes: Status of systems and references for data are indicated in Table XI. NA = not applicable
gas
Compressed nitrogen gas
Ibm
effectiveness
and
system
pressure.
The
combustion of a reactive injectant. injectant in a system in which the serious result has been the reduction directly
to the
fluid
some of the best 117, and 118). A burst
and
diaphragm
have
at the
been
tank
of bladder
failure
also may
contraction obtained
outlet
of the
with
usually
gas. In bladder
laminated
is used
plastic
to seal
development
and metal
the
fluid
alternate
liquid
the
and
arrangement
pressurizing
having
gas in the
neither same
a bladder
tank
and
nor
relies
a burst
only
the
diaphragm
on gravity
work,
foil (refs.
in the
storage. On system activation, the rise of pressure in the fluid tank breaks and fluid flows through the tubing and manifold and into the injectors. A simpler
be sudden
For example, in an LITVC test using lead perchlorate bladder was eliminated, an explosion resulted. A less of the pressurizing capacity of hot gas by loss of heat
consequent
results
consequence
and
tank
115,
during
diaphragm,
stores
the
acceleration
forces to position the fluid over the outlet. The Titan III system uses this system (fig. 27). The supply tubing, the injectors, and about 2/5ths of the tank are filled with nitrogen tetroxide fluid and then pressurized by addition of compressed nitrogen gas into the remaining tank volume. Leakage from the injectors is prevented by pyroseals (ref. 47).
2.2.2.3
PRESSURIZATION
SYSTEM
High-pressure gas required to pressurize gas such as nitrogen or helium or by systems, the same gas generator is used The
compressed
gas system,
the fluid is provided either by a tank a solid-propellant gas generator (table as a source of gas for roll-control jets.
if independent
of the liquid
tank,
consists
bottle of any convenient shape, a squib valve, and a pressure pressure of the gas is from two to seven times the liquid system and XI), so that after is still greater than operation, the pressure-reducing injection liquid/gas bulk
the the
gas tank required
high gas pressure valve in order
usually is reduced to to obtain reproducible
liquid
has
been
used,
sufficient
With this _rangement, the initial injectant pressure but becomes successively less during cause a certain amount of wasted injectant also, in the case of electro-hydraulic valves variation
in injector
response
pressure
gas tank
or
valve. The initial pressure (tables X
needed, the tank pressure pressure. During motor
the liquid system pressure by a valve operation and to avoid an
pressure so high that it will degrade side-thrust efficiency tank is used (fig. 27), the initial gas pressure is made high
of the
of a metal
regulator operating
has discharged the full amount minimum system operating
of compressed XII). In some
still remains
(ref. 116). If a common enough so that after the for
effective
operation.
pressure is the same as the initial gas supply the TVC duty cycle. This reduced pressure will due to off-peak LITVC efficiency (ref. 133); operated by pressurized injectant, it will cause
time.
Usually the high-pressure tank is left filled remotely just before launch.
empty during storage and handling of the motor Otherwise, for the safety of personnel working
97
and is near
pressurevessels,the tank must be madeheavyweight with a factor of safety ranging from four to six. An advantageof pressurizingwith compressedinert gasis that no bladder or other separationis needed,provided gravity or accelerationforces constantly hold the liquid over the tank outlets for positive expulsion. The mixing of injectant vapor into inert pressurization gas and the dissolving of pressurizing gas into injectant liquid are minor problemsfor which allowancecanbe made(ref. 47). If a solid-propellant gasgenerator is used ir_steadof compressedinert gas as a sourceof pressurizationgas,the systemmay be designedwith the typical low factors of safetyusedin rocketry and also may be storable indefinitely in readinesscondition. The production of gas during motor operation dependson the burning rate of the solid propellant andthe burning surface at the moment. The generator propellant grain is shapedto provide a changing burning surface area that approximately matches the expected program of maximum demand for pressurizationgas.Accordingly, the gasgeneratorprovidesa continuous flow of gas throughout the motor operation sufficient to displacethe largest expectedliquid flow that may occur in each period of the motor operating time. Large vectoring usually is neededonly in the early part of the motor operation. Gas-generatorpropellant grains are designedto producelarge initial gasflows and relatively low flows later in the firing. Since adequategas flow must occur at all times whether gasis usedor not, significantly more gasmust be produced than is neededto displacethe total storedliquid. Whenexcess tank volume is provided to act as an accumulator, the total amount of gasrequiredcanbe reduced becausegas produced at times of low liquid flow demand will be retained for a limited time for useat times of largedemand. The surplus gasgeneratedthat exceedsthe liquid-displacementneedsand the accumulator capacity is diverted by a pressurerelief valve and releasedoverboard, preferably through small nozzles pointed aft so that thrust is recoveredfrom the unneeded gas.A screenis located upstreamof the pressurerelief valveto preventany particles of propellant or residue from enteringthe valveor the remainderof the system. The TVC pressurization system typically is activated either by firing a squib valveat the compressedgas tank outlet or, if a gas generator is used, by igniting the gas-generator propellant. In either casethe releasedpressureactsto break the tank outlet membraneseals (if the tank is so sealed) to fill the lines and injectors rapidly and then provide high momentum to the fluid jets dischargedinto the nozzleexhaustflow. An LITVC systemis not activated until about a secondbefore motor ignition; however,if the systemis activated but not launched,then the fluid and pressurizationdevicesmust be replenishedbefore another launch can be attempted. An exception is the Titan III LITVC system,which is filled with the fluid and pressurizedin the standbystate andrequiresonly electrical activation and the burning off of sealsat the injector port opening(ref. 114).
98
2.2.2.4
LIQUID
STORAGE
EQUALIZATION
When the system liquid distributed shifting excessively.
has two or more tanks, it is sometimes necessary to keep the weight of evenly between the tanks to prevent the vehicle center of gravity from A device such as an interlocked flow-drive positive-displacement pump
is used
the discharge
2.2.2.5
to equalize
DISPOSAL
from
OF SURPLUS
the tanks.
INJECTANT
LITVC systems almost always use liquid at a rate lower than that provided for in the design. This difference occurs because enough liquid must be carried for the worst possible flight control situation. Actual flight thrust vectoring requirements vary from vehicle to vehicle according penalized
to the mission requirements. by having to carry the excess
Some weight
flights of the
needing little vectoring liquid and not benefiting
would from
be the
added thrust resulting from liquid injection. To prevent this unneeded liquid from penalizing the vehicle performance as additional inert weight, provision is made to jettision this liquid and obtain thrust from it during its disposal. Flow meters are installed in the liquid lines to measure the amount of liquid used of liquid used. Flight control repeatedly compares and
signals
the
injectors
to expend
the
excess
motor thrust will be augmented expenditure of the excess liquid injectors and the rocket exhaust.
without and axial
2.2.2.6
MOTOR
Important exhaust dynamic
ADAPTATION
OF THE
advantages
of
LITVC
jet and usually does design of the nozzle.
are
liquid
thrust thrust
FOR
that
and the
an integrator sums the total amount total used with the programmed use
uniformly
around
the nozzle
so that
deflection. The vehicle is lightened is gained as the liquid leaves through
the by the
LITVC
it requires
only
light
protection
not complicate the structural design The design effort required to adapt
from
the
hot
of the motor or the gas the motor for LITVC is
simple and is limited to providing for (1) erosion in the nozzle around the injection ports, (2) shielding of LITVC system components from exhaust plume heating, and (3) possible structural reinforcement of the nozzle and motor aft end to accommodate the fixed loads of the LITVC system and the dynamic loads due to vectoring. The non-axisymmetric pressure in the nozzle due to injection must be provided for in the nozzle design. This pressure creates circumferential bending of the nozzle in a direction in which the nozzle typically has low stiffness. The exit cone diameter will increase in the direction of injection and decrease in the direction at right angles to injection. exit-cone structure may have to be increased. Provisions
for
erosion.
-
the liquid jets are injected within the injection ports
The
injection
In large
ports
into the exhaust-gas in the wall of the
99
nozzles
are the holes
of lightweight
in the nozzle
flow. The injector nozzle (figs. 29,
orifices 30, and
construction,
liner
through
the
which
are safely recessed 31). The interface
between the injector and the nozzle structure usually contains a gas-tight sealsuch as an O-ring. The wall
of the
nozzle
around
and
downstream
produce a characteristic pattern of deep grooves that begin on each
grooves side of
of the
injection
and ridges an injector
ports
erodes
(fig. 34). Typically, port and extend
abnormally
to
there are two aft (sometimes
spreading out in a V-pattern), a crescent of moderate erosion around the leading edge of the port, and a ridge of almost uneroded surface extending directly aft from the port. The chemical and gas dynamic effects that produce these effects have been studied by analysis and test The
(ref.
amount
119). of erosion
depends
on the
material. If a reactive injectant over which the exhaust-gas/injectant
such
reactivity
of the
injectant
and
the
as strontium perchlorate is used, the mixture passes usually has greater than
type
of ablative
entire wall area normal erosion;
typically, this erosion will be twice normal or more. Low-cost materials were considered for the 260-in. (6.6 m) motor, but subscale tests showed that these materials would be severely eroded
(ref.
119).
An inert injectant such as Freon if there were no injection from region
where
the
shock
The edges of holes severe erosion by downstream
edges
wave
will produce a cooling effect, and erosion will be less than the hole at all. However, at the outer edge of the mixture
contacts
the
wall,
the
through which the injectant the hot exhaust gas; this of
the
holes.
If
injection port and the adjacent nozzle The holes usually are tapered conically
erosion
erosion enters erosion
is allowed
is increased
slightly
over
the nozzle can be subject usually is concentrated to
degrade
wall, LITVC performance and are just large enough
the
geometry
normal. to very on the of the
may be reduced to accommodate
(ref. 47). the liquid
jet so that gas circulation and consequent heating in the hole will be minimized. are relatively small, having diameters less than about six times the boundary layer
Holes that thickness,
erode only moderately, because the supersonic gas stream tends to skip over the hole. However, large holes erode severely and are subject to a high rate of heat transfer on their downstream edge, because the high-velocity gas impinges against the downstream edge as if against an obstacle (refs. 134 and a large number of small orifices in efficiency. The problem of erosion overcome by making the holes as material such as graphite/phenolic. Minuteman III third-stage motors. in reference
135). This hole-size effect has provided a reason for using addition to that of obtaining greater side-specific-impulse in the immediate region of the injection ports has been small as possible, and by use of inserts of erosion-resistant This method was used in the A3 Polaris second-stage and Data on erosion of nozzle liners due to LITVC are given
119.
Thermal protection of LITVC system. - The LITVC system must be protected from heating by radiation and sometimes by gas circulation from the rocket jet plume. In some instances, this heating has been sufficiently great that liquid in unprotected tanks and tubing boiled,
100
! _
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ii
i iii_i_!ii¸¸
i
i i_
i ii!ii
i!i¸¸_¸ii¸_i_i¸ii
ii_ii!i_i il_
i i iiii_i
ii_ • _iiiiiii_i_ ¸_¸i i_iii!
!
i_i_%_i_i_i
'_,_,_'_ii_'," _'_"_ __i,,_i_!,_i '
iiiiiiii_i_iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!!ii!iiiii!!_!_
10t
control
circuitry
burned
and
malfunctioned,
However, the problem is easily solved, weak or negligible gas flow. Adequate as a thin layer plume and the Structural transmit mount motion
the
of sheet cork or rubber. Sometimes LITVC components (fig. 28(b)).
reinforcements.load to the
The LITVC nozzle, the motor
the entire LITVC system between the nozzle and
from
a fraction
lines
of an inch
or expansion
The dynamic nozzle. The
and
joints
bracketry
and
pressure
vessels
failed.
since the heating is passive and accompanied by only protection has been obtained by light insulation such a panel
system aft end,
is installed
between
the exhaust
is usually, supported by brackets or both. Generally, it is advantageous
that to
on the nozzle in order to avoid any problem of differential the motor aft dome or skirt. Such movements have ranged
to several
inches.
When
nozzle
mounting
is not possible,
flexible
are provided.
loads caused by liquid jet produces
LITVC are a reaction
the direct result of injection of liquid thrust like a small rocket motor. This
into the reaction
amounts to a significant fraction of the total side force. It is withstood by the injector mounts to which the injectors are bolted and the adjacent nozzle structure.The emerging jet both blocks and mixes with the flow to produce a pattern of local loads on the nozzle wall (figs. The
23, 24, and 25). character
of this load
can be best
understood
by
considering
the
nature
of the
liquid
injection effect in detail. Close to the hole, the jet acts like a solid object in blocking the main flow. A detached bow shock forms upstream of each jet and causes a large and abrupt increase in wall pressure upstream and along the sides of each injection port. Fluid dynamic shear breaks the drops of liquid into tiny droplets that rapidly evaporate and mix with the exhaust
gas. This mass,
thus
added
and mixed,
increases
the
density
and
pressure
in the
local
gas flow. If the liquid is chemically reactive, it adds thermal energy to the local portion of the main flow, which further increases its pressure. In either case, this portion of the exhaust flow that has been augmented by liquid injection expands and accelerates in a manner
similar
to,
but
more
energetically
than,
the
rest
of
the
exhaust
flow.
It
thus
undergoes a greater change in local momentum than do normal (unaugmented) portions of the exhaust flow, and this change is transmitted to the nozzle wall as increased pressure. The increase of wall pressure due to addition of injectant mass and energy to the gas stream travels
with
the
flow
all the way
to the nozzle
exit,
spreading
out in a broad
fan-shaped
(fig. 24). The
forces
area , ;
described
combine
to
produce
the
total
thrust
vector
control
force
caused
by
liquid injection. If the liquid is reactive, the total side force is 11/2 to 3 times greater than that produced with an inert injectant. The increase is due to higher pressures resulting from reaction of the injectant with the gas. Comparative breakdowns of these effects are shown in table
XIII.
A method wall
that
is presented
has been
used
in reference
for estimating 136.
LITVC
these operation
102
forces
and
produces
their
distribution
asymmetric
on the nozzle pressure
loads
on
Table XIII. -
Side Force Composition
for Inert and Reactive Injectants
(refs. 124 and 127) i
Percent of total side force Side force component Inert liquid
Reactive liquid I
i
a
Reaction thrust of the fluid jets
15 to 30
5 to 15
Pressure from shock waves
25 to 50
l0 to 30
Pressure from addition of mass
20 to 50
60 to 85
and energy to the exhaust flow
the nozzle equal to the vectoring side force. These loads usually are widely distributed and cause stresses that are not significant increases to the stresses due to symmetric gas flow. Other load conditions, including handling and assembly, ground level thrust, altitude thrust, vibration, withstand loads due wall exit
and thermal loads, result in exit-cone asymmetric LITVC loads. However, to LITVC are usually the primary loads cones
designed
for minimum
It is general practice to predict Pertinent test data are then used those for erosion, calculations. The ensure
operating
and sometimes results of the
Performance
Use
test
of
than adequate to the asymmetric nozzles with thin-
weight.
the heating, to check the
erosion, accuracy
and load conditions by calculation. of the calculated results, particularly
to evaluate the validity of empirical constants used in the analyses are used to modify the design, if necessary, to
integrity.
2.2.3
conceptual
designs that are more as mentioned previously, for large-expansion-ratio
data design
Evaluation
dominates
all
to full-scale
operation,
phases
and Testing
of
LITVC
because
103
the
performance technology
analysis of the
from
LITVC
the
effect
early is still
basically empirical. Early in a
development effort, data are obtained from the literature. These data are generalized by nondimensionalizing, cross-related by plotting, and then are transformed to the new operating conditions by use of relationships based on physical laws. This method results in some unavoidable errors. Later, subscale tests are conducted to provide Finally,
data the
under conditions full-scale rocket
capability is demonstrated. the LITVC system operates
2.2.3.1
PERFORMANCE
In the early being made
data
usually
are similar is tested
to those with its
Operating-capability as designed.
DATA
stages of the to determine
performance
that motor
FOR
tests
are
of the LITVC
particular system,
routine
procedures
to ensure
that
DESIGN
development the general
period when optimization configuration of the motor
available
design problem. and its vectoring
are
those
generated
and tradeoff studies are system, the only LITVC
in previous
LITVC
development
programs. Data from at least ten LITVC development efforts are available (refs. 46, 48, 50, 51,107, 109, 121, 122, 124, through 127, 129, 133, and 137 through 142). These data usually are reduced to standard plots and correlations (sec. 2.2.3.2) for comparison with the particular The
motor
methods
being
designed
and
and
correlating
of plotting
for generating LITVC
performance data
estimates
generally
involve
for new converting
systems. the
data
and parameters to dimensionless ratios that eliminate factors of secondary importance LITVC (e.g., the parameters of the main rocket motor). Thus, thrust vector capability
for is
expressed as side-force specific impulse, the thrust vector deflection is the ratio Fs/Fa, and the injection rate becomes the ratio of injectant flowrate to nozzle exhaust flowrate. Similarly, the location of the injection port in the nozzle is expressed as the ratio of its distance from the throat to the distance from the throat to the exit (X/L). In the resulting plots (figs. 35 different basic
through 42), different efficiencies; the upper
sets of data appear as different curves and curve invariably indicates the more efficient
represent injectant
or condition. The side
most force
a form
popular and generally useful to axial force or deflection
that
(sec.
2.2.1.5).
The
next
angle) plot that weight
is ready
most
versus
the
for
use
plot is that angle (figs.
in estimating
common
plot
presents
ratio
of injectant
the
the
of side specific impulse versus the ratio 35, 37, and 42). The data are presented fluid
ratio
flowrate
of side
and,
consequently,
is useful
conditions.
104
of analyst, that have for
and
force
to exhaust-gas
is not as convenient for use by the designer it reduces the scatter in data from motors flowrates
required
comparing
the
to axial
flowrate
maximum
force
(figs.
36
(or and
of in
flowrates
deflection 38).
This
but has the redeeming feature varying chamber pressures and data
from
diverse
sources
or
160 i
I
O_
Freon
O
X
I14-B2
injectant
\ 14(
o o
\
!
Z v
\
E .o
\ 120
o !
i i
_o
\\ i00 °_
°_ U_
O.
8C
4-I
O
6C 0
0.02
L
I I°
0o
,_Data
band of full-scale
Polaris firings
e = 14 X/L= 0.3 • = 0° Pinj=
500-750 Ibf/in.29 (3,447-5.171 MN/m-)
0.04
0.06
I 2°
I 3°
_Small data
0.08 I 4°
I
scale, F a = 1080 Ibf from LOX/RP-I motor
e = I0 X/L= 0.3 • = 0° Pinj = 750 Ibf/in_ 2 (5.171 MN/m _)
Figure 35, - Comparison of small-scaleand full-scale data on injectant specific impulse vs deflection angle and side force (ref. 121).
105
Fs/F a 0
(4804
N)
0
Fs/Fa
Constant 60_
area
pressure,variable
Pinj = 750
50
Pc = 728
injection Ibf/in'2
(5.171
MN/m 2)
N204
Ibf/in. 2
e=
8
Six
orifices
(5.019
MN/m 2)
_
j
NaC 104
7_/o H202
/
NaC I04
50?0 H202
/
NaC i04
307_ H202
40_
30_
Motor parameters (except for N_O 4) P = 375 Ibf/in.2( 2.586 MN/m_)
O /
Freon
e a
jo j 2°
= I0 = 17.5 °
F a = 1080
(4804.1
Wa = 4.0 Ibm/sec d
= 1.50
N)
in.
(1.814
(3.81
kg/sec)
cm)
t Pamb=l.5
ibf/in. 2 (10.342
LOX/RP-I
propellant
kN/m 2)
--
Injection
00
Ibf
--
/ 10
C
I14-B2
parameters
_nj = 2.45 X/L = 0.3 @ = 0°
_
0
0.04
0.08 Injectant Exhaust-gas
Figure 36. - Comparison
O. 12
0.16
Triple
orifice OLo.5 i(1.27
flowrate flowrate
of performance
of inert and reactive
injectants
(data from
refs. 121 and 142).
in. cm)
300
!
Sr
(CI 04) 2 injectant 6.
.
6
E .m ,--4
-j %
cO
'
I i
260
u_ ,m
_ _ 24o "_
x
L
220
-I
_ 2oo _z ---__. 180 ¢ = 25 ° o -.j 160
¢= 0o 140 0.3
0.35
0.4
0.45
0.5
0.55
2.18
2.45
2.73
3.04
3.35
3.68
X/L
6inj 2.14
2.26
Data
at
2.34
a constant jet
Figure
37. - Effects
of injection
2.42
F /F value s a deflection angle
location
2.51
of of
0.026,
which
2.59
M. znj
corresponds
to a
1.5 °
and angle on injectant
specific
impulse
(ref.
108).
Fs/F
0
a
m
I Sr
1 (Cl
1
04) 2 [
I
injectant f
\
6°
\ 5o_
4 ° _
//
3o_
b
\
f f
\
/
0
=
Pinj
/_
Pinj
Mmlm2)
1500 Ibf/In. 2 (10.34 I 800 Ibf/in. 2 (5.516
=
MN/m2)
/
2° -
Y
io_
0 O_ 0
0.I
0.2
0.3
0.4
0.5
0.6
Injectant
P
= c e =
800
a =
20 °
F a
=
Wa =
Figure
38.
2 (5.516
Injection MN/m
2)
7.4
7.9
- Effect
_nj
=
X/L=
ibf
(8896
Ibm/sec
of
injectant
N)
(3.583
i .0
parameters
2.45 0.35
=
2000
0.9
flowrate
parameters
Ibf/in.
0.8
flowrate
Exhaust-gas
Motor
0.7
25 °
Single
orifice
injection
kg/sec)
flowrate
and
108
injection
pressure
on
side
force
(ref.
108).
Fs/F a
0
I Freon
i13
injectant
4 °-
04
2 ° --
O-i o --
00 --
i
0
0.2
0.4
0.6
0.8
X/L
Pinj
=
do/d t Single e = i0 Pc _=
Figure 39. - Effect (adptd.
=
variable
=
Ws/Wa
=
0. i
A
_s/_a
=
0.2
_s/_a
= 0.3
_s/X_a
=
0.073 orifice
375 0°
of injection from
O
Ibf/ino
injection 2
(2.586
MN/m 2) <>
location
and orientation
ref. 109).
109
on side force for different
0.4
injectant
flowrates
140
!
!
Freon
I14-B2
injectant
r-4
Constant
O
injectant
flowrate,Ws/W
I
! tH #m
12C
e = l0
a
: 0.05
Original
data
'
I /
/ I i00
/
/
m 40
v
Transformed 40 O O
data
8O
=
60 400
0
800
Injection
:
_e
e =
e =
The
aata
the
: ein j: _
Pinj(e=7)
were
2 2)
P
= 0° =
c
used
to
calculate
the
I0 2.4 2
375 ibf/in. (2.586 MN/m
values
2)
for
relation
injection
pressures
were
= (Pinj/Pc_=loX
Figure 40. - Transformation (adptd.
145)
25 °
I0
7 by
2 (MN/m 2 x
_me
= 800 ibf/in. (5.516 MN/m
2OO0
1600
2.1
_:
The
pressure,lbf/in.
7
einj: Pc
1200
from
related
110
the
expression
Pc(e=7)
of data on injection ref. 121).
by
pressure vs injectant
specific
impulse
900
I
I Freon
I14-B2
I
800
injectant
I 3
annular
I orifices_
/
700
600 OO
o
_One
ann_u lar
orifice
50O z v
/
4OO U O
300 Note:
°rq
Orifices
circumferential
located line
on
on
a
nozzle
wall
200
I00
/ 2
0
4 Injectant
6 flowrate
(kg/sec
Figure
41.
- Effect function
of
number
x
Ws'
111
I0
ibm/sec
2.2046)
of annular
of injectant
8
flowrate
orifices (ref.
on side force 124).
as a
12
240
Sr
(CI
injectant
04) 2
Contoured Pinj
r-. o_ o
0-__
200
0
_,
Minuteman
= 750
X/L
nozzle
e = 23.5, e i= 12.5 Pc = 500 11 _in. 2 (3.447 Fa
X
_
i
=
16 001
= 290'
Ibf 2 =
data
= 0.55
(71.17
MN/m 2 ) kN)
16°
--E
o0
160 l
Design
z
cur
v
0
Pc = 400 ibf/in. 2 _2.758 MN/m 2) Pinj = 800 ibf/in. (5.516 MN/m 2)
_Q
_ i
X/L = 0.5, _ =25 ° , ein_ = 6.5 _ i = 330, _2 = 230
120
Ibf/in.
2 (10.342
MN/m 2)
bO 80
P
I
"
I
le
da_! _'_
_
--..nj =
,4
o arls
conzca
nozz
e
a a
_.._.........._._
O
.4
P
= 400
Ibf/in.
2
(2.758
MN/m 2 )
C
40 e=
19_
einj= X/L=
6.5 0.5
ibf/in.
= 25 ° =
27.5 °
I
Triple
2
Fa =
H
Wa
1050
ibf (4671
orifice
Variable = 4.0
injection
N)
ibm/sec(1.81
do
kg/sec) -I 0 =
.01
0
.02
.03
tan I .04
Fs/F a .05
.06
I
I
;
i
0o
io
2°
3°
Figure 42. - Transformation of performance data for strontium perchlorate injectant (adptd. from ref. 108).
.07
Fs/Fa
I
e
4°
2 (5.516
MNIm 2 )
Other some (figs.
useful LITVC
graphs design
37 through
are made to meet special design needs parameters on side specific impulse,
40).
The LITVC performance data accumulated represent motor configurations and operating motor and LITVC system being designed modification. The data is transformed from conditions
by applying
one
or more
For inert liquids been shown to
the momentum be the factor
impulse
changes
due
to
momentum principle shown in figure 40.
physical
in flowrate,
used
nozzle
this method is correlated residence
occupied
pressure,
to transform
the
laws that
data
available
appear
to be dominant.
energized
for injectant
or
density
through
(ref.
a change
total nozzle gas flow has changes in side specific 107).
An
in nozzle
example expansion
of the ratio
is
is the dominant effect. Accordingly, the most are based on the relative enthalpies and the fraction flow
for transforming data collected with a parameter representing time
The effects ratio have
by
from previous LITVC development programs conditions that are different from those of the and, therefore, cannot be applied without the original test conditions to the new design
of the injected flow relative to the that could be used to predict the
For reactive injectants, energy release successful data-transformation methods of the
and generally show the effect of force ratio, or thrust deflection
(refs. for one nozzle
mixing
and
143
through
146).
Figure
43 illustrates
reactive injectant. Side specific pressure and thermal energy
impulse and the
reacting.
of changes in nozzle geometry such as divergence angle, contour, and expansion been transformed by use of geometric, gas dynamic, and oblique shock wave
relationships. Some of the changes in nozzle geometry and can be transformed by simple geometric or vector summation
injection methods
geometry and spacing (ref. 107).
For changes in injector location or nozzle length, the coefficient of thrust relationship, separated into portions that are in or out of the injection region, can be used. The injection effect can then be assumed to change in proportion to the fraction of the motor thrust that originates in the injection region. This approach tends to favor injection at upstream locations in the nozzle, making it necessary to include a calculation of the degrading effect on the side force of the shock wave caused by injection when the shock wave reaches the other
side of the nozzle
(refs.
107,
126,
and
147).
A variety of computer programs for predicting the LITVC effect exist, but not one of them has adequately predicted the side force effect, because these programs are limited in the range of phenomena assumptions on which energy shock; reaction
addition; droplet with
thermochemistry,
that they they are
represent based are
displacement without breakup, vaporization, momentum interchange; and
shock
generation.
and the linearized
realism of supersonic
their results. Some of the flow with mass, bulk, or
mixing; boundary-layer separation and induced and bulk formation; mixing, vaporization, and and liquid breakup, mixing, vaporization, Use of these
113
computer
programs
has been
inhibited
2OO
E
O
150
!
J
O
,-4 O.
i00 O
J
U
v
Sr(Cl04) 5£ O 0J
2
Pinj
=
2°
jet
injectant
1500
Ibf/in.
2 (10.342
deflection
MN/m
2)
angle
i
I00
200
(
300
Ps,inj
400
T3s,inj
d
5 00
)1/2
Vinj
Nozzle
parameters
Pc
Ps,inj
Ts,inj
ibf/in.2 einj
Symbol
O ® Z_
2
x
145)
(K
9/5)
ft/sec
(mx39.37)(m/sec
x
6.2
3.00
375
3010
2.66
8800
3.2
2.48
800
44.8
3550
1.83
7940
19
3.0
2.42
375
23.6
3620
3.74
7820
19
3.0
2.42
650
41.0
3620
3.74
7820
19
3.0
2.42
800
50.4
3620
3.74
7820
2. i
2.12
800
85.5
3980
2.57
7200
The
correlation
the
parameters
- Correlation (adptd.
of from
shown listed
injectant ref.
should
8.6
x
in.
j
7
Note:
43.
(MN/m
oR
Vin
19
7
Figure
Mini
d
be considered
in the above
specific
122).
114
valid
only
within
the
range
table.
impulse
with
key
nozzle
parameters
of
3.281)
by
lack
of
empirical
correlation
with
correlations
2.2.3.2
the
data.
for transforming
SMALL-SCALE
Early in information
test
Therefore, data
(ref.
the
general
practice
has
been
to
use
51).
TESTS
development on which to
period, the designer needs only approximate parametric define optimization studies and preliminary designs. Existing
LITVC data are employed as far as possible, transformation-correlating methods being used to transform the data to the current design problem. The transformed data are approximate at best and contain errors that are in proportion to the differences between the motors from which
the
data
came
and
the
motor
being
designed.
As the
design
proceeds,
better
data
are
needed; these data usually are obtained a variety of LITVC arrangements that
from tests of scale models of the motor nozzle with are in the range of design interest. There is little
scaling problem involved Figure 35 shows LITVC full-scale motor.
small-scale model from small-scale
in translating data obtained
A small-scale test series includes sufficient data for construction pertinent features
ranges of variation in the test conditions of the plots and correlations needed
design parameters (sec. 2.2.3.1). that represent its larger counterpart
injection
geometry,
2.2.3.3
and
FULL-SCALE
ambient
Also, the small-scale motor in propellant gas properties,
scaling
are
DEVELOPMENT
eliminated
high-confidence in the horizontal
data at the or vertical
and
possible
earliest position.
LITVC
time. The
tank
and
bladder,
quality
tubing,
insensitive and
design
Static tests orientation
is designed with nozzle geometry,
first opportunity, usually the first tests, errors of data transformation
changes
are detected
and
defined
by
are usually conducted with the motor of the motor is considered in selecting
for the
static
test
to allow
for the change
L ITY TESTS
The operating capability of the parts and determined at various stages of manufacture, relatively
that will provide to establish the
TESTS
the orientation of the LITVC tank and plumbing in direction of gravity force on the liquid.
2.2.3.40PERATING-CAPABI
a
pressures.
A full-scale test of a LITVC system is conducted at the static test of the full-scale rocket motor. In the full-scale and
data to a full-scale counterpart. tests compared with data from
fittings,
to malfunction
flow after
components assembly,
meters,
and
they
have
operability.
115
of the storage, check been
LITVC system are regularly and launch preparation. The
valves tested
have
been
to demonstrate
shown
to be
specified
The
most
critical
components
are
the
injector
valves
and
the
pressurization
system
because
they are sensitive to malfunction. Surveillance tests to monitor the operating capability of these components have been developed (ref. 46). The injectors are evaluated in bench tests with an inert liquid (e.g., Freon) that evaporates and leaves the components clean. While this evaluation is not fully representative of actual conditions, it is sufficient because it provides an
effective
functional
nonevaporating necessary. After on the
motor,
injectant assembly these
response through storage or launch When
test
of the
components
a gas generator
is used
for continuity
pressure checked
is monitored for electrical
A complete check rocket motor; this
and
without
degrading
is used in bench testing, thorough and installation of the injector valves are tested
the electric readiness.
voltage
components
feedback
to pressurize
resistance.
by actuating
loop.
These
the
injectant, of inert
by pressure gages. The squib continuity and resistance.
valve
the
igniter
at the
means
components after without activating
above,
it is possible
to
check
the system has been installed and it or disturbing its launch readiness.
116
the
the
function
charged
with
the
during
at low
is used,
the gas
of the inert-gas
of injector valves sometimes is conducted while check is accomplished by connecting an auxiliary
discussed
desired
is checked
pressure
outlet
or
testing is system
and checking
when
squib
at high
liquid into the LITVC system, actuating the injectors, and noting used is inert and evaporative to avoid contaminating the system. By the
valves
are repeated
gas
If a reactive
cleaning after and pressurization
the injector
tests
If a tank
them.
tank
is
the system is on the supply of pressurized response.
The
of all critical injectant
and
liquid
LITVC gas
but
3.
DESIGN
CRITERIA
and
Recommended 3.1
Practices
FLEXIBLE
JOINT
3.1.1
Configuration
3.1.1.1
DESIGN
OPTIMIZATION
The flexible joint design shall be based on the movable-nozzle constraints and joint, motor, vehicle, and mission design parameters either maximum performance or maximum cost effectiveness, depending The
basic
motor
rate, actuation environmental possible, designer.
on specific and
needs
vehicle
acceleration, conditions)
and characteristics
joint
design
of the program.
parameters
(motor
flight inertia loads, should form the basis
optimization analyses. The following procedure optimum joint design (i.e., the least expensive without violating any imposed restraints): Calculate reference
(2)
Prepare a anticipated parameters:
(3)
Vary
constraints, initial joint
anglel mass design.
actuation properties, Whenever
as explicit design points to the joint must be established on the basis of
is recommended joint that satisfies
for establishing the all mission objectives
against
for this motor should call for state-of-the-art materials, philosophy expected for the operational system, and be for all loading conditons. Calculate motor performance, and
which
the independent
weights
other design
for this
designs
independent
and
optimization parameters
parameters
analyses for use in the
117
motor
design.
will be compared
pivot point, and cone angleand nozzle design, motor performance, tradeoff
at some
preliminary layout drawing of a motor approximately the size for use in the vehicle. This motor is designed to a particular set of motor pressure, joint actuation torque, pivot-point location, and cone
performance,
design
vector
the required nozzle vector angle that will produce a side force position consistent with the vehicle performance requirements.
angle. The drawing embody the design structurally adequate joint
pressure,
envelope for the
the joint design parameters should be provided Otherwise, these interdependent design points
(1)
envelope that result in the choice
- motor
determine and cost to
motor
pressure,
is the
baseline
an optimum
design.
joint
actuation
torque,
their influence on joint design, if considered. Continue to perform
obtain
final
This to select
design.
the
near-optimum
values
of the
Since no parametric weight-scalingequationsare availablefor flexible joints, the basic joint design should be varied geometrically for pivot position, joint diameter, and cone angle; and the effect of these parameters on weight at different motor pressures and spring torques should be calculated. Conduct structural analyses,using the empirical relationships of section 2.1.5 to establish joint component thicknesses.Layout drawings of the nozzle andjoints should be prepared and compared with envelope constraints to establish limits for joint geometry as a function of pressureand spring torque. The joint weights as a function of motor pressure, spring torque, and geometric limits should be included in motor andvehicleoptimization computerprograms. (4) Make new layout drawings basedon the near-optimum values of the operating parameters and check to ensure that computer-predicted weights, lengths and volumes,and performancesarevalid. To ensurethe validity of the design,perform necessary calculations external to the generalized computer program; e.g., structural analysis(sec.2.1.5), detailed weight calculations,and grain design. Steps3 and 4 should be repeatedasnecessary.The joint designcharacteristicsresulting from this procedure must be consistent with the required motor characteristics and with near-optimum systemperformancewhen all stagesareconsidered. The dependent design parameters considered in sections 3.1.2.3 and 3.1.2.4, the independent design parametersconsidered in section 3.1.2.5, the material properties (sec. 3.1.3), and other important parametersincluding internal pressure,axial load on the joint, flight loads, and loads resulting from the particular motor or vehicle configuration (sec. 3.1.4) should be included in the optimization analysis to the extent required by the particular application. Specific recommendedpracticesfor componentcost analysiscannotbe madebecauseof the many complexities involved. Cost-estimatingtechniquespresentedin reference 148(ch. X) should be usedas a guide. The generalrecommendation for cost analysisis to establishthe joint design and then to continue to improve the design with cost effectivenessas the criterion. The mission performanceof the vehicle should be maintained constant for each design alternative evaluated.The analysismust include the cost of all motor components redesignedasrequiredto maintain constantvehicleperformance.
3.1.1.2
ENVELOPE
The
values
joint
can operate
It is recommended nor
greater
than
for
LIMITATIONS the
inner
and
outer
joint
angles
_1 and
{32 shall
so that
angle/3_
ensure
that
the
as required. that
the
45 °, and
flexible angle
joint
_2 is not
be designed less than
118
45 ° nor greater
than
is not
less than
55 °. (All
40 °
successful
joints to date have operatedbetweentheselimits, but joints with largervaluesfor/31 and t32 may be possible). To reduce consistent with the allowable compression
3.1.2 3.1.2.1
spring torque, the difference (/32 -t31) should stresses in the elastomer and reinforcements
requirements.
Design Requirements ACTUATION
TORQUE
The total actuation torque -consisting offset torque, inertial and gravitational be less than The
be a minimum and any axial
total
actuation
dependent contributing
on
the
torque
available
torque
is the
of foint torques,
from
spring torque, frictional and aerodynamic torques
torque, - shall
the actuator.
summation
of all the
contributing
torques,
each
of which
the specific design of both nozzle and motor. It is recommended that torque, including the variability of the torque constituents, be calculated
is
each for
the full range of motor service life. The service life consists of (1) vectoring for checkout at zero motor pressure and (2) vectoring over the entire range of motor operating pressures. Use the maximum actuation torques (nominal determine total required actuation torque, and actuation necessary
system. statistical
3.1.2.1.1
Joint Spring Torque
The ]oint
A valid statistical analysis data will not be available
spring
torque
shall
be the
plus maximum variability) thus obtained to compare this value with the capability of the
is not possible at this point of design, since until a joint is designed, built, and tested.
minimum
required
to fulfill
motor
the
operating
requirements. The joint spring material properties
torque should be calculated obtained in a subscale test
by the methods of program (sec. 3.1.7.1).
section 2.1.2.1.1; To establish the
use range
of probable variability in spring torque, calculate the joint spring stiffness at zero motor pressure for the maximum and minimum elastomer shear modulus. This range should be assumed to exist at all motor operating pressures. The
spring
actuator. control
torque
at the
maximum
The spring torque system. If the joint
value
of shear
at the minimum is to be vectored
modulus
is used
in the
design
of
the
value of shear modulus affects design of the to different angles during motor operation,
take advantage of the reduction in spring torque due to motor pressure to reduce the actuation power requirements. Calculations using the average elastomer shear modulus must be made of the joint spring torque during motor firing. The expected variability calculated at
zero
motor
pressure
must
be
superimposed
119
on
the
average
values
to
establish
the
maximum and minimum spring torques. It is desirablethat the minimum spring torque be sufficiently large to prevent a negative joint spring stiffness due to pressure.If a joint designedto be vectored at pressureis to be vectoredat zero pressureduring motor preflight checkout, the vector angle at checkout must not result in a joint spring torque greaterthan that occurring during motor operation. 3.1.2.1.2
Friction
The
joint
shall
stability Neither
Torque demonstrate
of the flight
the
coulomb
coulomb
control
friction
and
nor
the
viscous
design. Both frictions should be measured time of relatively constant motor pressure three
or
four
different
cycles at each actuator force actuation
rates.
viscous
friction
consistent
with
the
system.
The
wave
friction
can
be
estimated
during a static firing. be selected and that
form
should
for
preliminary
It is recommended that a the nozzle be actuated at
be sinusoidal
and
run
for
at least
IIA
rate to avoid the force transients that occur at the start and stop points. Plot variation with either vector angle or actuator stroke for one cycle at each
rate,
and
determine
the
average
actuator
force
at zero-degrees
vector
angle
(fig.
14(a)). The test data should be smoothed and the actual instantaneous actuation rate at zero-degrees vector angle determined either by calculation or by use of a plot of vector angle Variation with time. The variation of actuator force at zero vector angle with actuation rate should
be plotted;
friction
(fig.
3.1.2.1.3
record
the
zero
intercept
as the
friction
and
the
slope
as viscous
14(b)).
Offset Torque
The flexible-joint and movable-nozzle consistent with reasonable manufacturing A value
coulomb
for
determine
offset
torque
pressure
cannot
distributions
offset torque shall practice and cost.
be calculated around
the
unless
movable
be a minimum
air cold-flow nozzle.
For
tests joints
are
value
conducted
to
up to 22 in. (55.88
cm), the offset torque is small compared with the joint spring torque, and it is recommended that it be ignored in estimating actuation torque. For larger joints, an assessment should be made of the offset torque, pivot-point movement (sec. 2.1.2.3) being considered
and
measured at
worst-on-worst
during
a minimum
requirements, 3.1.2.1.4
by and
Inertial
The actuator the
the
moving
bench
tolerances test
maintaining motor
being
program.
assumed.
The
It is recommended
minimum
tolerances
offset that
consistent
torque
should
also
the offset
torque
be kept
with
design
due
to the
practice,
cost
requirements.
Torque torque
shall
provide
for
the
nozzle.
120
maximum
torque
inertia
be
of
The inertial torque should be estimatedfrom the massof the movablenozzle assumedto be rotating about the geometric pivot point. It is recommendedthat half of the weight of the flexible joint be included with the movable section in calculating movable nozzle weight, center of gravity, and dynamic moment of inertia. It is recommendedthat the maximum inertial torque be included in the actuation torque. 3.1.2.1.5
Gravitational
The actuator accelerations. Calculate
the
Torque
torque
axial
and
shall
lateral
provide
accelerations
vehicle pitch accelerations
and yaw. The torques should be calculated
recommended
that
3.1.2.1.6
the
maximum
Insulating-Boot
for
the
at the
acting in the
gravitational
maximum
nozzle
insulating
modulus of requirements.
boot
torque
must
be
fabricated
insulating boot must be the bellows used, a wrap-around insulating boot that
even
It is difficult
to estimate
due
to
of gravity
that
pivot point for inertial
be included
in the
vehicle
result
from
due to torque.
actuation
these It is
torque.
Torque
such
elasticity and thickness) and If a material such as silica-filled
recommended allows.
center
at the geometric same manner as
The insulating-boot torque shall be a minimum requirements and available motor envelope. The
torque
with
the
this
that
consistent
it has
with
the
a minimum
stiffness
yet is thick enough butadiene acrylonitrile
to
a bellows-type
insulating-boot
diameter, with a bellows fabricated recommended that the insulating-boot
of
torque.
boot
For joints
be used
up
(product
of
satisfy insulation rubber is used, the
type, whereas if a silicone rubber such (fig. 7) will result in low boot torques.
material
insulating
when
as DC 1255 is However, it is the envelope
to 30 in. (76.2
silica-filled butadiene acrylonitrile torque be assumed to be 35 percent
cm)
in
rubber, it is of the joint
spring torque. With the same insulating-boot material for joints approximately 90 in. (2.29 m) in diameter, it is recommended that the insulating-boot torque be assumed to be 15 percent of the joint spring torque. For designs using low modulus silicone rubber, it is recommended spring torque. 3.1.2.1.7
Internal
A ctuator The and
that
aerodynamic propellant
the
insulating-boot
Aerodynamic
torque
shall
include
torque
be
assumed
to be
25
percent
of the joint
Torque the effects
of internal
aerodynamic
torque.
torque must be estimated as a function of vector angle, motor pressure, grain/nozzle configuration for the maximum expected vector angles during
121
motor operation. The torque should be determined from a knowledge of the pressure distribution along the nozzlesurfaces,using the methods outlined in section2.1.2.1.2 (i.e., air cold-flow testsor two-dimensionalmethod of characteristics). When a joint has a forward pivot point, the total aerodynamictorque must be addedto the actuation torque, so that the actuator can be sized properly. When a joint has an aft pivot point, the aerodynamictorque should be ignored.
3.1.2.1.8 The
External
Aerodynamic
Torque
external
aerodynamic
torque
during For
in which
the
nozzle
cause
a negative
is not
shrouded
by
a motor
torque in the high dynamic pressure region that This torque should be determined from a knowledge
along the nozzle external surfaces internal aerodynamic torque. The pressure
region
3.1.2.2
NOZZLE
The
not
actuation
torque
flight.
all motors
aerodynamic estimated.
shall
must
be less than
VECTOR
vector
angle
and total
the joint
ANGLE
shall
should be aerodynamic
be
large
spring
AND
PIVOT
enough
skirt,
the
external
occurs during flight must be of the pressure distribution
calculated torque
stiffness
case
in the stiffness
to ensure
same manner as the in the high dynamic
positive
actuation.
POINT
to cause
sufficient
side force
for
vehicle
steering. The vector angle required for steering either must be given in the motor requirements or calculated from a trajectory analysis that considers pitching requirements and worst-case winds. A method for calculating the required vector angle is given in reference 149. If
the
vector
angle
is given
in the
motor
(normal distance from the line of action vehicle center of gravity) or the required It is assumed that the side force causing point,
and
the
effective
pivot
point
requirements,
the
control-force
moment
arm
of the motor thrust for a vectored nozzle to the steering moment must be stated as a requirement. a steering moment acts through the effective pivot
should
be calculated;
from
this location,
the geometric
pivot point should be determined. The geometric pivot point should be as far aft as possible consistent with optimum vehicle performance. However, envelope restrictions on actuators and exit cone movement must be considered. It is recommended that a forward pivot point be
used
submerged
for
nozzles
nozzles
with because
little the
or exit
no cone
submergence, movement
122
and requires
an aft
pivot
less envelope.
point
be used
for
3.1.2.3
AXIAL
DEFLECTION
Clearances effects Joint
axial
between
the
movable
and fixed
nozzle
components
shall allow for
of axial deflection. deflection
is the
compressive
response
of the
flexible
joint
motor is pressurized. The clearances between the movable and must be sized to allow for this movement as well as for rotational The required clearances the nozzle as it deflects The
axial
considers
should be studied through axially and in the vectored
deflection the
should
geometric
be calculated
changes
loading. As soon as possible axial-deflection characteristics spring
stiffness
3.1.2.3.1 The
must
nozzle
caused motor
be known
Misalignment
nozzle
shall
have
must
be
by motor pressure.
assembled
pressure
Efforts occurs
should be made during in a nozzle, since the
excessive follows:
during
which
misalignment
(1)
Estimate effective
(2)
Estimate
layouts
overlaid
analysis
(sec.
in at least
joint
that
the
the
to show
2.1.2.3)
four
of the guidance
control
that
increments
of
at zero
system.
pressure
that
in the
motor
at some
vector
angle
length actuators will result that the pressure at which
results
in
vectoring
such
the
vectoring
that
in alignment alignment
at a selected occurs be the
occurs.
the joint design to estimate the amount of misalignment that orientation of the actuator to the nozzle could result in A recommended
procedure
for estimating
misalignment
the axial compression of the joint (sec. 2.1.2.3) and pivot point (sec. 2.1.2.3.1) during motor pressurization. the
when
pressure.
nozzle
angles.
occurs
should be bench tested to measure the compressive spring stiffness. The axial
misalignment
pressure and fixed It is recommended
average
loading
that
fixed nozzle components movement of the nozzle.
of two
a finite-element during
for the design
motor
the use position.
program, a joint obtain the axial
a vectoring
at a selected
with
of the joint
in the and
Nozzle
alignment The
the
spring
torque
stiffness
(sec.
the
is as
approximate
2.1.2.1.1)
during
motor
determine
graphically
pressurization. (3)
Assuming nozzle operating
(4)
Assume
vectoring
nozzle
is aligned
misalignment
as the
at zero motor
pressure, is pressurized
to maximum
the
expected
pressure. that
the
nozzle
as the misalignment calculate the actuator
misalignment
that occurs null length.
required
at the
123
selected
at zero motor
pressure
zero-misalignment
is the
same
pressure,
and
The actuator null length must be checked during the static firing test program. The recommendedprocedureto determinethe actuator null length is asfollows: (1) Estimate the effective pivot point at the motor pressureat which the nozzle and motor center lines are to be aligned (sec.2.1.2.3). (2) Align the nozzle to the motor at the pressurefrom item (1), and calculate the vector angleand actuator length at zero motor pressure,consideringthat the pivot point movesfrom the effective pivot to the geometricpivot point. (3) Prior to the firing, actuatethe nozzle in the motor and determine :
per inch
of actuator
the vector
angle
stroke.
For the static firing, set the actuator length as determined in item (2) and measure the vector angle change of the nozzle at various motor pressures during the firing,
(4)
the pressures being selected held at the trial length from (5)
Compare
the
pre-firing
to give as wide a range as possible item (2) for at least one half-second.
and
firing
data
to calculate
the
at its natural
frequency
with
amount
the
actuators
of zero-pressure
misalignment.
3.1.2.4
FREQUENCY
The
nozzle
RESPONSE
shall
not
be subject
to excitation
The stiffnesses
of all parts
of the nozzle
are higher
the
frequency
than
natural
should
of the
be designed
hydraulic
so that
actuator
frequency is almost equal to the natural frequency of the nozzle and the actuator system will occur and will produce frequency is less than the system will occur. Further, mechanical destructive The
natural frequency the nozzle natural
frequencies of the motor and vehicle failure of the nozzle results.
natural
firing. The consideration
frequency
of the
nozzle
assembly should be of the control system
and
motor
subjected response,
assembly
their
system.
natural If the
frequencies nozzle
that
should
to a frequency but if this is not
is known, a notch filter should be incorporated vectoring commands at or near the natural frequency.
124
of the natural
coupling with the guidance be greater than the natural no coupling
that
be measured range known,
into
the
could
prior
cause
to static
determined from it is recommended
that a frequency range from 2 to 100 Hz be tested. If the motor is too large frequency response tests, the natural frequency must be calculated. When frequency suppress
natural
actuator system, coupling instability. If the nozzle
of the actuator, frequency must to ensure
of vibration.
control
for practical the natural system
to
3,1.2.5
ENVIRONMENTAL
3,1,2.5.1
Thermal
Thermal
PROTECTION
Protection
protection
temperature
of
limits
the
for
joint
the full
shall
enable
duration
it to remain
motor
gases
be sufficiently motor shade
and
maintain
thin
the
to minimize
joint the
vectoring. For region in order
that reduce the the fixed nozzle
the radiation to minimize
additional stagnant
The
temperature.
torque
An
component
that a radiation gas. This practice
boot torque. Provide component to allow
protectors a result of
(fig. 7(b)) vectoring
insulating
due shield allows
to the
motor
gas as the joint
boot boot.
a clearance gap between for joint axial deflection
the and
must be located in a stagnant gas as the joint is vectored. must be or motor
sufficient pressure;
to prevent otherwise,
be located in a circumferential
is vectored.
Aging Protection joint
elastomeric
oxidation
during
Polymerization conditions that determined
material
shall
pre-fabrication
of uncured maintain
early
shear specimens properties. (2)
not
be subject
to adverse
and post-fabrication
(sec. 2.1.7.1) Store uncured
by
the
following
steps:
from new elastomer elastomer at different
of aging and
storage.
elastomer should be minimized by the elastomer within specifications.
in a program
effects
storing These
(1) Fabricate stock to conditions
the elastomer under conditions must be and
establish for the
test quadruple-lap initial elastomer time period it is
anticipated the elastomer will be stored during the program. (3) Fabricate quadruple-lap shear specimens from the stored elastomer stock to establish the elastomer properties. (4) Select storage conditions to be included in the processing To
must If the
(fig. 7(a)) be used to use of thinner, more
torque is generated. It is recommended that the joint protectors region in order to reduce the size of the protectors and to minimize
of the
3.1.2.5.2
ablative protectors (fig. 7). The the erosion by the flow of the
shield to be effective, the gap circumferential flow of the motor
The gap between sacrificial thermal contact of adjacent protectors as
flow
at allowable
additional
envelope allows space, it is recommended the insulation boot from the hot motor
pliant boot materials radiation shield and
allowable
of the firing.
Protect the joint with an insulating boot or with sacrificial insulation material must be sufficiently thick to withstand hot
at or below
minimize
and test change in elastomer
specifications. changes
in joint
performance,
select
elastomeric
materials
for which
long-term
aging data are available. To protect the joint against changes in the elastomer properties surfaces exposed to ozone or oxygen, it is recommended that the joint be covered by impervious
coating
such
as chlorobutyl
rubber
125
or Hypalon.
at an
3.1.2.6
PRESSURE
The 'joint
SEALING
shall
pressure
and
not
leak
vectoring
It is recommended
that
when
subjected
to either
a pressure
load
or a combined
load.
reliable
joint
sealing
be
accomplished
by
joint molding process until unbonded areas are at a minimum to ensure that this process is continued on all subsequent should be performed to bonding of the elastomer, after joint molding by
experimenting
determine unbonded areas. For joints fabricated inspect the elastomeric pads before joint molding C-scan ultrasonic techniques (ref. 22). Joints
by secondary and the bonds fabricated by
only by cutting joints fabricated
processes
the
inspected
on
a sampling
basis
to
ensure
debonded
area
have
not
the
and then establishing controls manufacture. An inspection
compression molding and injection molding can be inspected and inspecting the elastomer surface. It is recommended that be
with
that
molding
apart a joint by molding
process
has
not
changed. Quantitative
criteria
for
that the photographs an acceptable joint, two examples
of unacceptable
Material
3.1.3.1
ELASTOMERS
for structural rate, and joint
shear
rate
properties
problem minimum
It is recommended shows shows
joints.
material
The important mechanical are secant shear modulus reinforcements shear strain
established.
Selection
elastomeric
needed actuation
been
presented in figures 44 and 45 be used as a guide. Figure 44(a) figure 44(b) shows a marginally acceptable joint, and figure 45
3.1.3
The
the
loading at temperature,
rate,
and
maximum
joint
loading
the minimum
the critical as imposed
in a quadruple-lap temperature (sec.
be determined
(ref. 78 and sec. values for these
actuation
at least
mechanical
motor pressure, by design factors
properties
vector angle, of safety.
properties to consider in the selection of the elastomeric material at 50 psi (0.345 MN/m 2 ), shear strength, and bonding to the metal
- all measured and operating should
shall possess
joint
2.1.2.1.1). mechanical temperature
as evaluated
if joint
shear specimen tested at the appropriate 2.1.7.1). The effect of compression on the
instability
due
to motor
pressure
is a potential
The materials should be selected on the basis that the properties at the critical motor pressure, vector angle, are
not
by appropriate
less
than structural
those
required
analyses
(sec.
to withstand 2.1.5).
The specific material mechanical properties should be established from pre-existing on the selected elastomer material, or these properties should be established from
126
the
test data specimen
t"--
_4 er 0
¢O r_
E o m
0
2_
¢,a
2_
E X
o |
u5 L_ 2_ °_ t,I.
128
tests (sec. 2.1.7.1). section 2.1.3.1.
3.1.3.2
Materials
that
have
been
used
in successful
joint
programs
are given
in
REINFORCEMENTS
The
reinforcement
properties angle,
material
needed
for
as imposed
The important are the modulus
shall
structural
by design
possess
loading
factors
at
at the
least
the
critical
minimum
motor
mechanical
pressure
and vector
of safety.
mechanical properties to consider in the reinforcement material to be used of elasticity, the compressive yield strength, the ultimate tensile strength,
and, for composite reinforcments, the interlaminar shear strength. For joints with metal reinforcements, the required buckling stress of the reinforcement can be calculated (see. 2.1.5.2) from the modulus of elasticity and joint dimensions. For joints with composite reinforcements, the allowable compressive MN/m 2 ). The true allowable compressive from bench testing a joint to failure (sec. basis
that
the
minimum
values
and vector angle are not evaluated by appropriate The specific representative
material mechanical of the selected
evaluation of reinforcements. composite
3.1.3.3 The
specimen Aluminum
tests. alloys
reinforcements
ADHESIVE adhesive
that
the
mechanical
be assumed to be 60 000 psi (414 laminate used must be determined materials should be selected on the
properties
at the
those required to withstand analyses (sec. 2.1.5). properties material, Steel should
critical
the maximum
should be established or these properties
motor joint
pressure loading
as
from existing data that should be established
are by
or composite materials are recommended as also be considered for reinforcements but only if
are impractical.
BOND bond
properties needed angle; as imposed To ensure
for the
less than structural
stress should stress for the 2.1.4.1). The
SYSTEM system
shall
possess
at
for structural loading at the by design factors of safety.
adhesive
bond
system
is stronger
least
the
critical
than
minimum
motor
the
mechanical
pressure
elast0mer
and vector
material,
all failures
in a specimen test program (sec. 2.1.7.1) must be cohesive. The processing of the specimen must be as nearly identical to that of the joint as possible. To maintain the quality of the adhesive bond system, controls on the system materials must be established. Systems recommended for use with injection-molded joints, compression-molded joints, and secondary-bonded
joints
are described
in section
129
2.1.3.3.
3.1.3.4
JOINT
The
The
THERMALPROTECTION thermal-protection
materials
properties
joint
needed
to maintain
joint
important
thermal
properties
diffusivity, flexibility have been
shall possess
temperatures
for the joint
at least the minimum
at or below
thermal-protection
thermal
allowable
limits.
materials
are low thermal
high heat of ablation at strain levels anticipated in service, and mechanical with minimum char fracture at temperatures expected in service. Materials that used in previous programs are recommended; these are presented in section
2.1.3.4.
3.1.4
Mechanical
3.1.4.1
GENERAL
Design
CONSIDERATIONS
The flexible joint shall possess the combination of weight and structural that contributes most to optimum motor and vehicle performance. The
flexible
joint
subjected to accompanying integrity section
the
should 3.1.5.
should
be
designed
to
have
the
required
structural
critical design loads of motor pressure and vectoring environmental conditions. Analytical verification of be made;
the
recommended
practices
for
structural
strength
capability and the the joint analysis
while
effects of structural are given
in
If axial compressive deflection is a requirement that cannot be met by a joint sufficient for structural strength, the thickness of the elastomer layers should be reduced, the result being an increased number of elastomer layers. The number of reinforcements will be increased, and these in section
should be designed 3.1.5.2. Compliance
demonstrated Because the the amount limiters storage
for structural capability according to practices recommended with the axial compressive deflection requirement must be
by test. joint has little axial stiffness in tension, the design .must incorporate limiters oia of tensile axial deflection that can occur as a ,result o;f ground handling. The
must
also
ensure
that
the
cannot
over-vector
the
joint
during
horizontal
or transportation.
The joint design should be established close to zero as possible. However, the
nozzle
guidance
less-than-optimum
control joint
system design
and
to obtain positive margins of safety since the joint design is interdependent optimum
will result
motor
in optimum
130
performance, motor
design.
it
(sec. 2.1.4.1.1) with design is
possible
as of that
3.1.4.2
DESIGN
The joint specified
FACTOR
shall
have
joint
OF SAFETY at least
the
minimum
factor
of safety
required
A design factor of safety should contingencies (e.g., approximation
be used in the design in estimation of joint
of
loading
developed variables
through involved.
(i.e.,
operational
or
handling);
these
that
define
elastomer
ring thickness,
The
reliability
the
the
joint
structural
and joint
cannot
tests and joints involved. convergence of the curves upon
number
capability
geometric
be demonstrated
failures
The not
upper
After each probabifity
and lower
3.1,4.3
have
understanding of the is not available, it is
design factor
than is applied to of safety is 1.25,
factor should be applied be applied redundantly
(e.g.,
material
been
mechanical
to the to the
properties,
explicitly
because
that the reliability
allowed
during
of the
prohibitive
number
reliability be demonstrated levels. The upper reliability the
development
and
reliability
levels
should
be set up before
of
by the level is
production
the lower reliability level is based the development and production
test, the reliability from all test results is plotted and extrapolated of achieving the required reliability. A test program to establish
FLEXIBLE-JOINT
The joint combination
safety
tolerances).
It is recommended for upper and lower of
joint. must
programs and must be greater than the required reliability; upon the calculated reliability from test results during programs. show the
of
a history of successful designs and a knowledge and Since in the design of flexible joints this history
then a factor of 1.5 should be applied to the motor pressure and to the vector angle. It
based
factor of safety could to joint performance
factors
recommended that a greater factor of safety be applied to the joint the overall motor design. For example, if the overall motor design
joint
for in
the required reliability (ref. 150). Unfortunately, there is insufficient of how these variables affect joint performance, and a single factor of safety Usually design factors of safety are specified in a design for specific classes
conditions
parameters
the
of flexible joints to account stresses, undetected variations
material properties, and undetected manufacturing deviations). The be established from a statistical study of all variables contributing correlated to understanding is recommended.
to obtain
reliability.
development
program
to the
is begun.
LOADS
stress profile shall of design loads.
include
all
individual
design
loads
or
the
worst
All design loads (see. 2.1.4.1) should be used to determine the critical design stresses. The critical joint loading condition, or worst critical combination loading, should be defined by summation of a load/time history of the joint. This profile should be prepared by tabulating all design loads, temperature exposure, critical-loading condition for each structural
and vectoring conditions element of the joint should
131
encountered. The be used in the joint
structural analysis(sec.3.1.5) than
3.1.5
Structural The joint
The
theories
should
that
margins
of safety
for the joint
are not less
be
design
Analysis stresses
necessary analyzed
preliminary and 82). The
to determine
zero.
to with
dimensions
following •
factors
Loads
shall not analyze the
and
of
joint
empirical with
be included
should
the allowable
a flexible
reanalyzed
should
used
use
exceed
stresses.
have
not
relationships
nonlinear
loads
(i.e.,
formulated.
(refs.
17
finite-element
in the requirements
be design
been
loads
79)
methods
for the
limit
and
The
structural
times
joint
to obtain
(refs.
80, 81,
analysis:
appropriate
factor
of
safety). •
Combined
loading
should
be analyzed
The maximum permissible minimum 3-standard-deviation quadruple-lap shear strain The
maximum
limited ultimate •
The loads
shear rate.
maximum should
specimen
permissible
to the loads.
shear
0.2 percent
permissible be the lesser
to determine
the resultant
stress in the elastomer should values of the failure shear stress
(sec.
2.1.7.1)
at the
tensile
stresses
in metal
yield
stress
compressive
appropriate
at limit
loads
stress
in metal
of the 0.2 percent
yield
ELASTOMER
The
elastomer
adequate The shear calculated
shear
THICKNESS thickness
shall
be limited measured
to the
and
and
should
ultimate
reinforcements
stress
to the from a
temperature
reinforcements and
be
stress
at
at ultimate
the buckling
The maximum permissible stresses in composite reinforcements assumed to be 60 000 psi (414 MN/m 2 ) and must subsequently the reinforcement laminate in bench tests to failure.
3.1.5.1
stresses.
stress.
should initially be determined
be for
..... not
be
greater
than
the
thickness
that
provides
strength.
stress in the elastomer at ultimate conditions.
due to combined motor The empirical method
132
pressure and and procedure
vectoring must be given in section
2.1.5.1 are recommended.When calculating the shearstressdue to vectoring,allow for the reduction in joint springtorque due to motor pressure(sec.2.1.2.1.1). Although the allowable shear stress at failure is increased when compression is superimposed,ignore this increasewhen establishingallowableshearstresses.
3.1.5.2
REINFORCEMENT
The
reinforcement
adequate :
The '
THICKNESS
and
procedure stress due
shall
hoop
and buckling
compressive
compressive
pressure
thickness
stress
vectoring
on
the
must
inner
be
2.1.2.1.1).
The
allowable
compressive
stress
,
from
bench
tests
of the
at ultimate
of joints
ADVANCED
The
The
design
analyzed t methods.
finite-element
method
thickness, thickness,
provide that
by
loads
to combined empirical
When calculating spring torque due
for metal
motor
method
and
the compressive to motor pressure
reinforcements
tensile stresses and fracture
methods
of analysis
must
be the
shall
involve
description be divided
should
be the
as shown must
in be
are important. The allowable mechanics properties of the
be
confirmed
be divided into and reinforcements that the analysis 2.1.5.3 be used.
average
calculated
a sufficiently
by
a minimum be divided
include
stress
133
refined
of the internal into a minimum
stresses for combined motor pressure stresses as described in sections 3.1.5.1 should
The
nonlinear
•
each reinforcement and both elastomer
The calculated the allowable
due
conditions.
to failure.
empirical
an accurate each elastomer
layers. It is recommended methods outlined in section
comparison
reinforcement
ANALYSIS
finite-elemen
panels to recommended
provides
and the buckling stress calculated stress for composite reinforcements
If a joint is to be used a number of times, the tensile stresses must be based on the fatigue reinforcement material.
3.1.5.3
that
:
at ultimate
lesser of the 0.2 percent compressive stress section 2.1.5.2. The allowable compressive
thickness
strength.
surface
be calculated
minimum
given in section 2.1.5.2 are recommended. to vectoring, allow for the reduction in joint
(sec.
determined
the
various
of nodes
and
stress distribution. It is of four layers across the of into
three layers across the a minimum of t 2 radial
nonlinear
and vectoring and 3.1.5.2. at the
grid
centroid
effects
and
that
the
should be compared with The applied stresses in this of each
panel.
3.1.6
Manufacture The
joint
joint
fabrication
and program
process
shall
be the
most
cost
effective
for
the
particular
needs.
An engineering study of fabrication fabrication processes that afford the costs. The engineering study should
processes should be accomplished best compromise between fabrication include detailed tradeoff evaluations
to select the schedule and of fabrication
methods;
reliability
status
past
program: fabrication, The
behavior
included
experience
research, tooling, of the
material
as a tradeoff
3.1.6.1
with
development, and facility
and
the
various
processes;
when
parameter
it is exposed
when
to various
alternative
fabrication
structural
materials
reinforcement
particular Metal
joint
reinforcements
fabrication
processes
limiting axial recommended recommended the material required
should
be
are evaluated.
are
either
compression for research
prior
reinforcements
shall
be
those
most
suitable
heat
treated
treatment
considered
thin
or thick,
requirement or small
the
difference
having
the
an influence
(sec. 2.1.4.1). Hydroformed development programs. Spun
programs. condition,
to final
should
be
to the required will cause
in the
for
assembly
on
the
Thin reinforcements are defined as reinforcements that can or spinning (sec. 2.1.6.1) and will be used in joints with a
for production in a normalized
properties
processes
reinforcements reinforcements
some of
are are
For both types, the forming should be made with and the material should be heat treated to the
machining. machined
from
plates
for
research
or small
programs. The plate should be normalized for rough machining and heat required properties prior to final machining. For production programs, thick should be stamped to the required shape with the material in the normalized
Heat
the and
needs.
possible method of fabrication. be fabricated by hydroforming
then
of
on schedules;
REINFORCEMENTS
The
Thick
of
or production; effect of the processing costs versus the joint configuration.
properties
prior
distortion
of the
a joint
by
spots and then assembling the reinforcements elastomer thickness will be circumferentially Although composite reinforcements have and molding, and molding with a mixture
to final
so that uniform.
the
treated to the reinforcements condition, and
machining.
reinforcements.
inspecting
development
This
reinforcements
all the
high
spots
distortion for high
should and
are aligned
be low
and the "
been fabricated by winding and molding, lay-up of chopped fiber and resin, it is recommended for
134
all production programs that composite reinforcements be fabricated by laying resin impregnated cloth cut into specific patterns into a matchedmetal mold and curing under pressure at a temperature and time suitable for the resin. However, in research or development programs, consideration should be given to compression molding with a compound of choppedfiber andresin.The sacrificial ablativeprotector (sec.2.1.3.4) should be fabricated asan integral part of the reinforcement.
3.1.6.2
JOINT
The joint The
joint
ADHESIVE adhesive
adhesive
SYSTEM
system
shall
system
not fail before
must
be
the elastomer
evaluated
prior
to
material. joint
fabrication
by
use
of
quadruple-lap shear specimens (sec. 2.1.7.1); an acceptable system must fail cohesively. The specimens must duplicate the thickness and cure condition of the elastomer and bond system in the joint. Fabricated joints should be bench tested at least to ultimate pressure and vectoring conditions to demonstrate the structural capability of the adhesive bond system. Failures
can
thickness,
the
occur
when
viscosity
the
bond
of the
sprayed on the reinforcements, these items should be included Each
lot of adhesive
and quadruple-lap variation.
3.1.6.3
FLEXIBLE
The joint
system shear
is either
and the
too
adhesive,
thick
the
or too
rate
materials to
should
ensure
be tested
quality
and
prior to
thin.
at which
and the time for spraying should in the joint fabrication specification.
tests
to use
maintain
To
these
control
the
materials
are
be monitored;
limits
in a joint
by peel
a record
of
on
tests
lot-to-lot
JOINT
fabrication
of the particular
system
primer
process
shall be consistent
with
the needs
and
characteristics
joint.
The molding process selected must depend primarily upon the number of elastomer layers, and the thickness of the elastomer rather than on the scope of the joint program. Joints with thin
dimensions of the joint, the layers and reinforcements elastomer layers (layers that
cannot be fabricated by injection molding) should order to improve the bond to the reinforcements.
by compression molding in molding has been successful
on joints up to 60 in. method is recommended programs. molding
Injection method.
be fabricated Compression
(1.52 m) in diameter with thick and thin reinforcements, and this for research and development programs as well as for production
molding Secondary
is a proven production bonding is a proven
135
technique process
and should be evaluated and should be evaluated
as a as a
molding method, particularly for large joints where significant cost savingshave been indicated. Prior
to
molding
process molding,
the
injection
on elastomer thickness the first development
This practice done by the Advantages
3.1.7
by
and joints
allows examination injection process, and disadvantages
or
compression porosity should
processes,
the
effect
should be evaluated be cut open to show
of
the
(sec. 2.1.6.3). After the joint cross section.
of the elastomer layer thicknesses, and if molding determination of the effectiveness of the elastomer of the joint
fabrication
processes
molding
are listed
in table
has been injection. VIII.
Testing
3.1.7.1
SUBSCALE
The
subscale
mechanical
TEST
PROGRAM
specimen
test
properties
The important mechanical failure, and the strength QLS specimens should in the joint. The bond QLS specimen Joints
should
have
been
used
program
shall
provide
values
for
the
elastomer
in design.
properties of the bond
for the elastomer are the shear between the elastomer and the
modulus, shear stress at reinforcement material.
be tested at the strain rate and over the temperature range expected between the elastomer and reinforcement should be cohesive, and the be used
to develop
designed
and
a satisfactory
tested
adhesive
successfully
and bonding
without
including
system. the
effects
superimposed compression and shear. However, if a joint is to be designed to operate pressure to take advantage of the reduction in spring torque due to pressure, the change shear modulus due to pressure must be measured. The reduced shear modulus is used predict spring torque 2.1.2.1.1). A method reference 78. If aging data are not be initiated as soon
and that
the has
of at in to
motor pressure at which the spring torque is unstable (sec. been used to measure the changed shear modulus is given in
available, a subscale test program to evaluate aging as possible in the motor program. This program
aging characteristics life and (2) several
of (1) several lots of the cured lots of the uncured elastomer
storage months
cured elastomer, the recommended test intervals are monthly up to six thereafter. For the uncured elastomer, the recommended test intervals
life. and
For the annually
are weekly
until
A subscale
test
and to establish
the shelf program acceptance
life has been should
be used
elastomer in order
characteristics must should evaluate the
to enable prediction to define uncured
of service elastomer
established. to evaluate
criteria.
136
lot-to-lot
variation
of elastomer
material
3.1.7.2
BENCH
Bench
TEST
tests
production the nozzle A joint establish The
of
]oint
characteristics
joints and shall verify clearance envelope.
bench axial
test
PROGRAM
that the
test program must be deflection characteristics,
for
compressive
axial
shall
establish
effective
acceptance
pivot
point
set up during the motor vectoring characteristics,
deflection
should
be
freely
about
to conducting measure the null
its effective
the vectoring actuator force
position.
The
pivot
point
while
tests, a pressure test and hence the offset
in a test
vectoring
tests
should
fixture
with
an
pressure and associated that allows the joint to
as it would
should torque
with
development program to and joint pressure sealing.
conducted
oriented
for
is compatible
unloading piston (fig. 21) so that the joint is subjected to the motor axial load. The vectoring test should be conducted in a test fixture rotate
criteria
be in the
motor.
Prior
be conducted in the same fixture to necessary to maintain the joint in a
be conducted
with
and
without
the
joint
ihermal
protection to determine the effect of the protection on actuation torque. In addition to axial deflection, vector angle, and actuator force, the hoop strain on the inner surface of each reinforcement should be measured. To ensure that only reliable joints are used in a motor, a stringent be conducted after The
same
criteria
tests
for
should
the
tensile-pressure leak the axial compression
should
be
joints.
If
be removed,
It is necessary should
that
be made
operating follows:
(l)
the
position
fails
target
light,
motor
acceptance used
effective
average
recommended
the
test
program
in the
should
as acceptance
elastomer,
the
elastomer
again. pivot
motor
production
this test
be determined
operating
procedure
to
pressure, find
the
for each
joint.
and maximum effective
pivot
A test
expected point
is as
target on a part of the test arrangement that is rigidly end ring and is near the theoretical pivot point. The
leg is to be aligned
coincident
with
the
center
line
of the
fixed
joint
ring.
Pressurize the
an
of the
pressure,
The
during
reinforcements
Mount a cross-hair-shaped connected to the movable end
(3)
a joint
the
pressure.
axial
(2)
conducted
and
at zero
test (sec. 2.1.7.2) is recommended; and vectoring tests.
nozzle and
Interpret
the
test
arrangement
vectoring open the
and
actuate
requirement.
the Camera photograph
shutter
the joint
Illuminate for one
as indicated
to an angle
the
cross-hair
complete
actuation
in the
sketch
in figure
at least
target
with
as large
as
a strobe
cycie. 46 to find
the
pivot
point. It is recommended between fixed and
that acceptable movable nozzle
limits on pivot-point components, rather
137
location be based than on clearances
on the tailored
clearances to fit the
Reference
line
+ Effective
pivot
point _ Axial point
pivot-
coordinate Reference
Figure 46. - Sketch
illustrating
determination
factors
of effective
138
involved pivot
in experimental
point.
line
measured pivot point. The clearance past with the purpose of providing radiation then should be established to be compatible The
recommended
set of layouts
design
practice
of the nozzle.
The
the radiation shield should be fixed in accordance protection, and the pivot-point acceptance limits with the required clearances.
to study movable
the effect
of pivot-point
components
are drawn
location on one
is to prepare
sheet
and
a
the fixed
components on another sheet. Superimpose the two sheets with an axial deflection appropriate to the pressure being considered, and successively pin the two sheets together at a series of pivot points. The limiting pivot point should be one that just permits the movable component
3.1.7.3
to rotate
to the
STATIC-FIRING
The
static-firing
requirements interact with Measurements misalignment coefficient develop
nozzle
program
shall demonstrate
and shall provide the nozzle. be
made
requirements, the nozzle,
a statistical
vector
angle.
PROGRAM
should of
required
that
the
data
needed
during
the
static
the joint
design
to design
firing
other
fulfills
the motor
components
program
to
that
determine
friction characteristics, natural frequency, and axial deflection, and vectoring capability. Sufficient
variation
should
be
obtained.
requirements. The final design of the guidance the results of the static firing tests.
control
Compare
measured
system
should
results
nozzle damping data to and
motor
be in accordance
with
The actuation power requirements should be established during the static firing. Certain increments to the actuation torque-friction and insulating-boot torque--cannot be calculated. With a bellows-type design (fig. 7(a)), the boot torque has been as much as 50 percent of the spring torque for joints up to 30 in. (76.2 cm) diameter (ref. 13). Therefore, when a bellows-type insulating boot is exposed to the motor environment, it is recommended that the actuator be capable of developing 50 percent more torque than the sum of the calculated increments to the actuation torque (sec. 2.1.2.1). When an exposed wrap-around insulating boot is used with joints up to 30 in. (76.2 cm) diameter, the actuator should be capable of developing 75 percent more torque than calculated. For an insulating boot protected by a radiation shield (fig. 7(a)), the insulating material usually is a soft silicone rubber (e.g., DC 1255), and for joints up to 30-in. (76.2 cm) diameter the recommended calculated.
3.1.7.4
actuator
DESTRUCTIVE
Destructive
testing
should
be
capable
of
developing
25
percent
TESTING shall demonstrate
join t failure
139
characteristics.
more
torque
than
The joint can fail in the mode can be demonstrated should
be mounted
angle
elastomer layers in an actuation
in an actuation
at various
pressures
up
or in the reinforcements bench test. The joint
bench
to
the
test
fixture
maximum
and
(sec. without
actuated
expected
2.1.5). Each failure the insulating boot
to the
operating
maximum
pressure
vector
MEOP.
At
pressures in excess of the MEOP, the vector angle should be increased in the ratio of the test pressure to the MEOP. Pressurization and vectoring should be increased at least up to the design ultimate pressure to demonstrate minimum compliance to motor requirements, and up to pressure producing joint failure usually identified by failure of the joint
3.1.7.5
AGING
The
joint
if the failure characteristics to maintain a pressure seal.
are required.
Failure
is
PROGRAM aging
program
shall
demonstrate
that joints
possess
acceptable
storage
life. Bench
tests
since
changes
should
be conducted
in joint
spring
on joints torque
that
have
been
formulation (sec. intervals and the
2.1.2.5.2). It is recommended spring torque measured. The
versus
time,
the
motor
specifications
and
3.1.8
Inspection
3.1.8.1
INSPECTION
The inspection initial ,material necessary
results
extrapolated
for the required
have
been noted
stored for
joints
service
using
environment,
a natural-rubber
that stored joints be vectored changes in spring torque should
to demonstrate
joint
in the
that
the
joint
at selected be plotted
will remain
within
life.
PLAN master plan procurement
to assure
shall incorporate through final
conformance
to design
inspection processes for use from joint acceptance to the extent
requirements.
Inspection processes should be used throughout the joint program beginning with material procurement and continuing through fabrication, process control, and final acceptance. Each phase :can use different inspection techniques with different acceptance or rejection standards. For this reason, an overall master plan for the use and management of the quality-control
program
the master plan and orientation master alertness planned
plan
should
of the
should
be established
prior
should be established on the basis of defects encountered, and the require
operators;
requirements
and
the
periodic
it should
evaluation
also provide
procedures.
140
to the
start
of fabrication.
The
scope
of
of the required reliability level, the type process sensitivity required. Also, the of the
for random
equipment checks
and on the
of the execution
skill
and
of the
Particular caution should be usedin planning the inspection requirements and in applying the inspection program so that material characteristicsand fabrication processesthat can affect the integrity of the inspection are identified. As an example, an inspection of elastomer thicknessthat is too infrequent could result in joints that weremarginalbecause of elastomerlayersthat varied in thickness.
3.1.8.2
INSPECTION
The
For the
For
PROCESSES
inspection
processes
reinforcements,
the
•
Spherical elastomer
•
Concentricity.
•
Thickness
•
Flatness.
•
Inner
the
shall
have
following
and outer
elastomer,
capability
minimum
radius at sufficient rings in a joint.
at various
the
inspection
positions
to
the
minimum
inspection
should
The
inspection
minimum deflection,
between
performance joints porosity
minimum
performance actuation, tests
should
be
inspected
the
dimensional end
attachment
rings,
inspections recommended and tensile-pressure seal
should taken
defects.
is recommended:
establish
expected
thicknesses
of
diameters.
su_faces,
concentricity
all critical
positions.
joint without adhesive on the reinforcement thicknesses and evaluate porosity visually.
recommended
of detecting
be
used
apart
to ensure
that
to verify
and
the
quality
cover then
for and
thickness
the
elastomer-to-reinforcement
141
joint
maintained.
is overall
flange-to-flange
envelopes.
porosity.
it. Measure
are the bench tests test (sec. 2.1.7.2).
clearance
is being
and
disassemble
At
Mold
a
elastomer
length,
parallelism.
the The
for compressive axial The data from the intervals, bond
production and
elastomer
3.2
LIQUID
INJECTION
3.2.1
System
3.2.1.1
SYSTEM
The
design
THRUST
VECTOR
CONTROL
Design
OPTIMIZATION of the
liquid
injection
system
shall be based
on a vehicle
optimization
study (including vehicle performance parameters, reliability, external constraints, and cost) that results in optimum vehicle performance. The recommended presented in chart
sequence of steps form in figure 47.
The design requirement based on a statistical allowance determined
for determining
because almost
optimum
should be defined as the maximum analysis of the operation of the vehicle
for the expected variation correctly at an early date
avoided, increases
the
envelope
LITVC
system
strongly side-thrust
affects impulse.
is
required vectoring capability on its various missions with
in the environments. This requirement and the use of inflated initial estimates
the vectoring requirement linearly with the required
design
the
design.
The
should should
system
be be
weight
The likely LITVC-system design options should be laid out without detail but should include basic design parameters such as type of injectant, injection pressure, source of pressurizing gas, number and spacing of orifices, injection location and angle, and tank type and
shape.
General
design
injector should
(including
motor
data,
candidate
injectant
specific
injection Initial
vehicle performance of these evaluations
configuration, design
amount
provide represent
the
of a system of data
tank should
for
LITVC
(e.g., should
range, payload, be used as the
shape,
and
be based
the pressurization on performance
systems
an empirical basis for design motor geometry and operating
final basis
is available
velocity), reliability, and for selecting the injectant,
data
(sec.
thrust
deflection
deflection angle
angle
be limited
cost. the
method. from
2.2.3.1)
previous and
programs.
should
be used
A to
analysis. The available data, however, will always conditions different from those of the motor for
which the new LITVC system is to be developed. Therefore, those data must or scaled to the geometry and operating conditions of the present motor section 3.2.3. The
impulses,
weight variation with flowrate, and tank weight variation with volume and pressure) be assembled. Each possible design choice must be evaluated in terms of its effect on
the desired The results
large
information
can be as much to 6 °, because
as l0 °, but the
142
efficiency
it is recommended as measured
by
be transformed as described in
that injectant
the
thrust specific
Define design requirements vectoring capability, motor meters, space envelope, constraints) .
Identify
the
(each option combination
LITVC
design
design
options
injectant, injector
loca-
available er'or i
ance data
data and to formulas
component and
weight curves
to
design
problem.
adapted
Determine
the
weight
and
capability option,
and
of each tion of
option on the rocket
Calculate
side-thrust
for each establish
the
(range, reliability,
payload,
for each optimum
option LITVC
Figure 47. - Recommended
and
will include one of design parameters
including type of injection pressure, tion, etc.).
i
(required para-
LITVC the
the configuramotor.
vehicle or
design effects
performance
final cost to system
as
velocity), required
determine design.
sequence of steps for determining
143
the
the optimum
LITVC
system design.
=.
impulse (refs.
drops 46,
3.2.1.2
to low
108,
and
The
The
shall
consistent
injectant
flowrates
required
for larger
deflections
deliver
maximum
with
material
side
specific
impulse
compatibilities,
and
storage
have
the
highest
requirements,
and
toxicity.
IX summarizes selection
high
OF INJECTANT
in]ectant
allowable
at the
122).
SELECTION
density
Table
values
_
the
of the
relevant
injectant
data
must
on the
consider
major the
operational
efficiency
injectants.
of the
injectant
in delivering
side
specific impulse. The relative efficiency of a candidate injectant may be known from existing data (secs. 2.2.1.2 and 2.2.3.1); if not, it should be checked by small-scale tests. Data on the relative efficiencies of various injectants are given in references 109, 121, and 141; figure 48 presents Isp(s) values for a number of inert and reactive liquids. The relative efficiency of a new injectant should be estimated from chemical-equilibrium calculations; various approaches and typical results are described in references 144, 145, and 146. Judgement make no injectants. injectant. and that
must be allowance
used in interpreting for the variation
the results in evaporation
of equilibrium calculations, rate and reaction time
Excessive time delay in energy release reduces the potential It is recommended that calculations be used only to screen the final evaluation be made by test firing.
since they of different
effectiveness of an injectant candidates
The injectant should be selected for highest density, so that the fluid tanks, valves, and tubing can be made as small as possible to save both space and system weight. A preliminary estimate should be made of the volume required for the liquid injectant, and the storage tank that will contain this volume should be designed and fitted around the nozzle so that the envelope
constraint
can be evaluated.
The liquid selected must long-term storage when kept of the Vehicle. As examples perchlorate in water boils at 70 ° F (294 should
not
propellants
crystalizes at temperatures K) at a pressure of one
be important
The compatibility neighboring systems on
places. If positive injectant cannot
not chemically decompose, evaporate, or crystalize during within the temperature and pressure limits specified for storage of typical limiting conditions, a 62% solution of strontium
with
of the should
contact.
sealed
systems
under
candidate injectants be checked, because
Danger
to
personnel
approaching atmosphere
32 ° F (273 K), and hydrazine (ref. 115). The latter limitation
pressure. with certain
may
be
the motor, propellant, reactive injectants ignite important,
especially
and other some solid in
safeguards against inadvertent spillage of an effective but highly be provided, then the injectant will have to be eliminated
144
confined reactive from
The for
Isp(s ) listed the following ,250;
emj=
is for typical booster stages (Pc _ 800 conditions: single orifice injection;'Pin
2.5;
Fs/F a
= 0.02
psia, j =
e _12) 1800 psia;
.
320 --
UDMH
+
N2H 4 (EXOTHERMIC
DECOMPOSITION)
Decomposition _.._under /These /difficul_
280
--
MHF-3
occurs
only
certain conditions. I s- values are to achieve.
(EXOTHERMIC
DECOMPOSITION)
240 NITROGEN
TETROXIDE
--
200
HYDROGEN
STRONT LEAD
PEROXIDE
IUM
PERCHLORATE
PERCHLORATE
+
+
METHANOL
WATER
MHF-3
1--
FREON 12, BROMINE
120-FREON
I14-B2
(INERT)
--l---
UDMH
+
FREON
113
(INERT)
N2H 4
N ITROMETHANE UDMH
--
FREON 114-12 (INERT) P E RCHLOROETHYLENE
l80--
BENZENE
I-
ISOPROPYL IRFNA ZINC WATER
40
ALCOHOL
(ENDOTHERMIC BROMIDE OR
DECOMPOSITION) IODIDE (INERT)
(INERT)
I
Isp(s
Injectants performance
Figure
48.
for is
- Values (data
which well
of from
),
lbf-sec/lbm
Injectants
TVC
performance
defined
side refs.
specific 121,125,
impulse and
145
for 129).
reactive
for is
and
which
TVC
not
well
inert
liquid
defined
injectants
consideration. For example, a toxic fluid such as nitrogen tetroxide or bromine shouldnot be selectedunless it is practical to provide protection to personnel and the environment during loading, checkout, ground testing, launch, and possibleother releasedue to mishap. The liquid must be compatible with every tank or bladder material with which it comesin contact. The tank or bladder materials must neither react with the liquid nor catalyzethe liquid's decomposition. The materials should resist decompositionby the liquid and remain impermeable,becauseliquid that has permeateda material is not available for injection. Resultsof investigationsof the permeability of variousbladdermaterialsgiven in references 115 through 118 should be consulted.
3.2.1.3
INJECTION
The
PRESSURES
injection
the orifices
pressure, shall
the
For
greatest
control orifice being tests.
orifice
maximize
The most efficient pattern circumferential line on the efficiency,
AND
INJECTION size,
the side
for injection nozzle wall
these
orifices
and
thrust
circumference
be estimated
number,
should
for minimum optimization
injector weight
and
of
have
omniaxis
control
orifices located in a 121, 124, and 125). rather
than
pitch-yaw
overlap losses should be 7 to 14 times the be studied and transformed to the system
If this is not possible, the spacing effect should be evaluated that cosine losses due to spreading the orifices around by vector
addition
system weight should be compared with pressures, and the overall optimum pressure three-orifice
and grouping
is obtained from many circular (figs. 29 and 31 and refs. 109,
of the
estimated
The injection pressure should be about twice the rocket side-thrust specific impulse (figs. 38 and 40 and refs.
The
spacing,
efficiency.
(ref. 142). Minimum spacing to avoid diameter, but the available data should designed (sec. 3.3.3.1). It is recommended
the
ORIFICES
since
simple
but
plumbing,
it provides this
effects.
chamber pressure to achieve highest 108 and 121). However, hardware
loss in side-thrust should be used.
is recommended,
side-force
in the
efficiency
excellent
effectiveness
must
for
lower
side-thrust
injection
efficiency
be confirmed
by an
study.
The simplest LITVC injector arrangement has four injectors 90 ° apart. However, thrust deflection may be required in any plane, not just the pitch and yaw planes. In this event, the side force is the vector sum of the forces produced by the two injectors. Two such injectors operating single
simultaneously
injector
As noted flowrate
to produce
will use injector the
previously, injection or side-force level,
same
liquid
at a rate
approximately
_/_'times
that
of a
side thrust.
is more efficient the number of
146
at low flowrates per injectors is increased,
orifice. then
If, for a given the side-thrust
efficiency is increased.The efficiency of a number of injectors usedto produce a singleside force is estimated by vector addition of their side-force contributions. Each injector is considered to produce a side force at its location independent of the adjacentinjectors. Therefore,the efficiency of multiple-injector LITVC can be estimatedfrom the equation
Cosineefficiency =
(12) n inj
where llin j =
I_/i
=
number
of injectors
angle between injector
operating
total
side force
and
the
side force
produced
Equation (12) does not include the efficiency increase due to reduced or efficiency decrease due to overlapping of adjacent mixing and shock
3.2.1.4
INJECTOR
The injector
LOCATION location
AND
DISCHARGE
and discharge
angle
side-thrust
For highest side-thrust efficiency, locate the injection orifices nozzle as is possible without incurring significant corss-nozzle vector deflection. (Cross-nozzle effects are pressure increases
(1)
Use the empirical
ratios
for X/L
listed
(refs.
X/L
Nozzle Small thrust deflection (about I °)
17.5°
0.3
0.4
27.5 °
0.2
0.3
Large thrust deflection (about 6° )
X = distance (along nozzle axis) from throat to point of injection
147
efficiency.
over.) One or more of location of the injector
108 and
divergence half-angle
L = distance from throat to nozzle exit plane
per injector
as far upstream in the rocket effects at maximum thrust on the wall of the opposite
that cross the optimum
below
Optimum
flowrate areas.
i TM
ANGLE
shall maximize
side of the nozzle caused by shocks and injectant following three methods should be used to estimate the nozzle exit-cone wall:
by the
125)"
the on
(2)
Estimate
the
Generate such that
a straight the line
curves
optimum
Use the
methods
shock
and
injector
location
by
use
of
empirical
curves
49. The
injection
point
at which
site (refs.
of fluid
mechanics
injectant-mixture
the line reaches
107 and
only
49).
and gas dynamics
disturbance
the
nozzle
for inert
wall is the
147).
in the
to estimate
nozzle
from
the path various
injection points; however, check the method selected against known before it is applied to the design problem. One such method utilizes computer program (ref. 151); however, in its present form the formulated
(fig.
line from the nozzle rim opposite the proposed injection point crosses the nozzle centerline at the angle X obtained from the
for _ in figure
probable
(3)
optimum
of the possible
test results the Boeing program is
injectants.
The optimum discharge angle (figs. 23 and 37) results in the greatest collision effect and mixing of the motor gas and injectant. From various studies (refs. 107, 108, and 125), the discharge angle should be 25 ° . However, as the discharge angle influences the location of the injectors and the discharge evaluated
3.2.1.5
their plumbing, envelope angle. For systems that
be a factor in the selection the discharge angle should
of be
by test.
AMOUNT
The
considerations should must be an optimum,
OF LIQUID
amount
maximum
of vehicle
liquid flight
INJECTANT
in]ectant duty
shall
REQUIRED be the
minimum
amount
necessary
for
the
cycle.
The weight of liquid injectant required must be calculated from the maximum required vectoring capability of the motor, the injectors and their location having been selected as described in section 3.2.1.4. The vectoring requirements will be given explicitly as thrust deflection The
angle
following
(1)
0 for
procedure
pitch
and yaw
is recommended
and
required
side thrust
for calculating
Fs, each
the weight
as a function
of injectant
of time.
required:
For each candidate liquid injectant, determine the side specific impulse Isp (s) as a function of deflection angle, and plot the results. Examples of such plots are given in figure
42.
(2)
Noting the motor vectoring requirements time t, use the results of item (1) to obtain function of time.
of deflectionang!e 0 as a function the estimated side specific impulse
of as a
(3)
Noting the motor side force requirements injectant weight flowrate _¢_ as a function
F_ as a function of time.
the
:
148
of time,
calculate
60 ° I
=25 °
50 ° __.__.__.----I
_
v
4oO
,[
0 ¢0 0 0
30 ° --
t4 0 4-I
qJ p-4
20 °
10 c __
O,
0°
i°
2°
Largest
Notes:
'
'
The rim
required
3°
deflection
diagonal from the injection is not the location of the
4°
5°
angle
0ma x
port shock
to the nozzle wave (cf. fig':23).
Figure is based on data from conical and contoured nozzies having e= 7 to 20, _ =18 to 28°,and _ both inert and reactive injectants.
Figure 49. - Relation
of thrust
deflection
angle to injector location
149
(refs. 107 and 147).
6°
Integrate estimate
(4)
the injectant the amount
determine
the
achieve The
(5)
The
the
of injectant
gas flow
of
of the
for the injector and transformed
the
injectant
liquid
side impulse
into
the tank warm-gas
cold
gas under
required
success.
for vectoring,
including
that
and valve vectoring.
for tank
ullage,
leakage, must be For preliminary
should
be carefully
estimated
for the motor
being
tank
within
of liquid
shall
expel
the liquid
the specified should
generator,
high
GAS REQUIRED
or
pressure
be from the
at a rate
response
gas
is the
a tank can
be
source
that will produce
time. of compressed contained
of the
inert with
gas used
gas or from
the
liquid
pressure be sufficient
The ......... of regulator so that
tank
may
a
in
to pressurize
gas should have a volume at LITVC operating pressure equal to the total volume, the volume of the piping and the manifold, and volume of liquid
in the
to
purposes.
OF PRESSURIZATION into
angles
to to
configuration and location selected by use of available test for application to the current design problem (sec. 3.2.3).
expelled. Because the specified injection point and be sustained acceleration and flow friction injectant should
available
10% for these
impulse
solid-propellant common tank.
injectant
not
of flight
deflection
add
gas flow
liquid, the own stored
probability
for the various
estimates,
AMOUNT
If a tank
of side impulse
ignition to the end of firing or use statistical methods
piping and valves, and for valve operation and added to the amount needed for
the required The
_Vs from motor injectant required,
for filling calculated
designed and, data, correlated
The
amount
specified
amount
side specific
3.2.1.6
flowrate of liquid
a
the of its to be
injectant pressure must be delivered to the fluid at the during sudden demands for large flows, the effects of liquid should be evaluated. The pressure applied to the liquid
have,
to
be
significantly
higher
at the injector valve. The piping sizes, to respond to the worst conditions.
the
than
the
gas supply
minimum
required
rate,
pressure
and
the gas delivered to the liquid tank should be reduced by a pressure liquid is not injeCted at pressures excessively above the pressure level set by
the design. The real
weight of gas so required should be calculated from one of the equations of state of a gas, such as the Beattie-Bridgeman equation or the equation of state with
compressibility factor contained in reference error
(ref. 152). An example of such 153. An estimate of the weight
< 10%, can be obtained
from
the ideal-gas
150
equation
a calculation for a LITVC system of the gas required, usually with of state:
is an
CPM p
-
(13)
RT
where p = density,
lbm/ft
P = pressure, M = molecular R
= universal
T = absolute
generator
3)
psia (N/m 2) weight
of the gas, Ibm/ibm-mole
gas constant,
1545.3
temperature,
C = conversion
If a warm-gas
3 (kg/m
lbf-ft/lbm-mole-°R
(8314.3
J/kg-mole-K)
°R (K)
factor,
is used
(kg/kg-mole)
144 in. 2/ft2
in place
of cold
(1 J/N-m)
compressed
inert
gas, a larger
total
quantity
of gas will be required than that calculated above. This condition arises because the supply of gas must be maintained at the maximum expected demand level through all periods of firing time, even though the actual demand for pressurization gas usually will be much lower than the maximum. The propellant grain in the warm-gas generator must be designed to produce vectoring overboard
sufficient
pressurizing
requirements (ref. through a pressure
gas
to
cause
154). The gas that relief valve.
the
injectant
is produced,
to but
not
If a common liquid/gas tank with no separation between the allowance should be made for the dissolving of part of the evaporation for example, N204
the real
of some in the
vapor methods and
not
with
used,
should
ideal
properties
of dissolving and evaporating of mixtures (ref. 152). Care of the
gases
in order
to avoid
the
motor
be released
liquid and the gas is used, gas in the liquid and for
of the liquid into the gas. The latter phenomenon Titan III system at 70 ° F (294 K), the pressurizing
(ref. 47). These effects of the thermodynamics the
comply
usually is negligible; N2 contains 1.5%
should be calculated by should be taken to use the substantial
errors
at high
pressures.
3.2.2
Component
The
size
represent
Design
of LITVC
components
the LITVC
system
shall
be based
to be designed.
151
on
verified
empirical
curves
that
The empirical curvesmust provide adequatedata of sufficient accuracyfor selectionof type of injectant fluid, injector location, number of orifices, injection angle, and injection pressure.Any additional data required must be generatedfrom subscaletests (sec.3.2.3.2). These curves must be based on test data, becauseavailable analytical methods do not reliably predict LITVC performance. Data for these curvesshould be obtained from earlier developmentprograms and subscale tests.These data should be plotted and correlated, then transformed for usein the current design(sec.3.2.3.1). After the first complete set of LITVC components has been designed, it should be fabricated, assembled,and evaluated in a full-scale test (sec. 3.2.3.3) at the earliest opportunity to confirm the design and to verify performancedata for usein further design improvementor performanceprediction.
3.2.2.1
INJECTORS
Injectors
shall
velocity
within
deliver
injectant
the required
The injector valves should flowrate as determined by satisfactory
accuracy
to the
response
be sized methods
for design.
The
exhaust time.
flow
in columnar
jets
at maximum
•
no larger described
than necessary for the in sections 3.2.1.3 and
injectors
must
contain
flow
maximum required 3.2.1.4; use data of
passages
and
orifices
that
are specially contoured and streamlined to accelerate the fluid to the maximum possible velocity on discharge. The pintles or gates must likewise be contoured and streamlined to achieve maximum acceleration of the fluid, so that on discharge the fluid is travelling at the highest
obtainable
pressure
The use of variable-flowrate side-thrust Off-on
center-pintle capability
injectors
vectoring (ref.
that
as little
to injection
as possible.
be
control
preferred
in
with
different
of actuating response,
the
from the inert
the natural
shock
cases
injector weight
frequencies
valves
must
penalty,
cost
76).
152
way,
or electro-mechanical these injectors can
minimal
certain
In this
the
system
momentum.
type injectors with servo is recommended, because
and versatile may
diverge
converted
because
These injectors should be of the center-pintle when fully open. To avoid vibration problems,
be set in a range method
in jets
efficiently
efficiency
simplicity. momentum
The
speed
will be most
of
their
of the structures
constraints,
for high
weight
and
loading.
type designed their operating
be determined
control provide
from and
low
for maximum flow frequency should of the vehicle.
the required
flight
control
speed limitations
of
Screensshould be installed in the liquid supply entranceto eachinjector valveto catchand hold any debris that might causetrouble in the injector valve. Measuresfor the control of contamination of fluid, components, and system may suffice in lieu of active screensor filters.
3.2.2,2
STORAGE
The
liquid
TANK in]ectant
during vehicle operation.
AND tank
storage
BLADDER shall
preserve
and provide
positive
The shape of the tank should of injectant to be carried
be selected should be
recommended
that,
amount
spherical
be used,
tanks
if
the
because
the
the
liquid
without
expulsion
of the
degradation liquid
to result in minimum weight. determined as described in
of
liquid
sphere
required
is the
most
shape;
during
motor
The required amount section 3.2.1.5. It is
is relatively efficient
or loss
small, but,
one
or
if a large
more
amount
of liquid must be carried, the tank should be toroidal, since this is the shape with the largest volume that fits around a nozzle. In intermediate cases, cylindrical tanks are suitable. The tank should be designed according to the recommended practices of reference 155, fabricated from a lightweight or high-strength alloy such as aluminum or stainless steel, and be compatible with the liquid. If the tank is to be left pressurized during storage or standby conditions when personnel may be near, the tank must be designed to meet the prevailing pressure-vessel safety code. To avoid this requirement so that a low factor of safety can be used, provision should be made to pressurize the tank when the vehicle is prepared for launch and after personnel have been cleared from the vicinity. If
a cool
depended be allowed
inert
gas
is used
for
pressurizing
upon to keep the liquid puddled to contact the liquid directly.
A bladder to separate the gas from warm gas, because the gas loses replenished
by
more
warm
gas.
if gravity the
outlet,
or
acceleration
reactive
injectants
forces
it is recommended
the liquid is recommended if the liquid heat to the liquid rapidly, contracts,
With
provide a positive seal because contact combustion or explosion in the tank. and plastic.
and over
and
warm
gas,
that
can be the gas
is pressurized and must the
bladder
by be must
between liquid and gas could result in failure through The bladder should be fabricated from laminated fiber
Special means should be provided to completely seal the injectant liquid in the tank. The filling and trapped-gas vent fittings should be designed with provision for positive closure (e.g., crimped or soldered metal closures). The tank outlet should be sealed with a metal diaphragm 156).
scored
to break
open
without
loose
153
fragments
when
the liquid
is pressurized
(ref.
3.2.2.3
PRESSURIZATION
The
SYSTEM
pressurization
injectant
When the LITVC in time for the high-pressure
within
shall, the
study The
system
the
pressure
prescribed range
time,
the injectant must be brought signal. The pressurization a warm-gas
given
tank
in section
system
pressurize
for injection
generator.
The
into
the
the nozzle.
up to operating system can be
choice
that considers pressurization system performance capacity of the pressurized-gas storage volume
to practices
If a high-pressure
or
within
design
system is activated, first vector-control
inert-gas
optimization performance. according
system
to a level
should
pressure either a
be based
and weight should be
on an
and LITVC determined
3.2.1.6.
is used,
the
tank
outlet
should
be sealed
by a squib
valve that
is opened by an electric signal or system activation. The gas flow from the high-pressure tank should be stepped down to the design injectant pressure level by a pressure-control valve. If there is any possibility that harmful debris might come from the tank, valve, or line, screens should be installed ahead of the controller. An inert gas such as nitrogen should be used weight unusual If
a
in a high-pressure
tank
system
to minimize
corrosion
is important, helium should be used, but special ability of helium to diffuse through materials (ref. common
liquid/gas
tank
optij..n_m for the system. liquid is used should be deflection.
is to
be
used,
the
range
and
compatibility
attention 118).
should
of pressures
and be
be given
provided
Also, the minimum pressure remaining when sufficient for effective injector-valve operation
Warm-gas generator systems usually employ solid propellants solid rocket motors. The warm-gas generator should
problems.
to the
should
almost all and thrust
If
be
of the vector
are designed like miniature designed to deliver the
gas-flowrate/time profile that is calculated as described in section 3.2.1.6 and reference 157. The propellant grain shape should be adjusted to cause the flowrate to vary to fit the desired curve (ref. 154). Usually a high rate is needed initially to provide for launch or staging pertubrations;
this
condition
is followed
when only vector trim and course generator should be a clean-burning 1922 K)) propellant alloy-steel tubing and will be usable only if safe levels. Otherwise The gas pressure
by a period
of low demand
corrections are needed. low-flame-temperature
during
the
rest
of flight
The propellant for the warm-gas (2000 ° F to 3000 ° F (1367 K to
that does not produce deposits and that is not too hot to use with valves. Propellants that burn at temperatures above 2500 ° F (1644 K) the operating period is short enough to limit heating of steel parts to insulation or high-temperature metals will have to be used.
flow from the generator should regulator designed to step down
pass through the pressure
(ref. 156). Since the production of gas by the generator of actual gas demand, the surplus gas must be diverted
154
a screen to catch debris and into a to the design injection pressure level is predetermined and independent through a pressure relief valve for
disposalto the environment. If possible,this unneededgasshould be releasedfrom a small nozzle pointed aft, so that a small increment of thrust canbe recoveredthrough its release. However, if the vehicle has a coast period and if the gasgenerator bums after the rocket motor has burned out, the small exhaust jet could cause unwanted changesin vehicle attitude. This condition should be preventedby exhaustingthe unneededgasthrough two equal orifices that areoriented in opposite directions. If the main vehicle system requiresa supply of gasfor roll control, the possibility of using the samegasgeneratorfor this purposeand for LITVC pressurizationshould be considered.
3.2.2.4
LIQUID
Flow
from
vehicle
If there prevent
STORAGE
and
inertial
is more offsetting
EQUALIZATION
sloshing
in multiple
tanks
and
large
lateral
than one tank, provision must the vehicle center of gravity.
be made Uniform
to drain expulsion
tank is dependent on the ability of the bladder to deflect circumference of the toroid during expulsion. The bladder so that one sector freely movement could generate
3.2.2.5
DISPOSAL
collapses on the liquid undesirable sloshing,
OF SURPLUS
injectant
flow
shall not
change
rate
should
the tanks at equal rates to of liquid from a toroidal
and fold uniformly around the should not be allowed to buckle
while other the sloshing
sectors should
are restrained. be inhibited
If vehicle by baffles.
INJECTANT
Injection system destgn shall provide flight weight and to obtain additional
The
tanks
properties.
for disposal thrust.
be measured
and
of surplus
integrated
over
injectant
time,
so that
to reduce
at any instant
of flight time the total amount of liquid actually used will be known. A computer or control device should continuously compare the amount of liquid used with the maximum that could
be
control nozzle The
used
up to that
time
without
jeopardizing
the
completion
of the
mission.
should then signal the injectors to expend the excess liquid equally around so that the motor thrust will be augmented but there will be no thrust deflection.
axial
thrust
added
by jettisoning
the surplus
expression:
155
liquid
can be estimated
with
Flight the
the following
aFa =
lsp(s ) (o = o*) Ws tan
a
(14)
inj
where /kF a
lsp(s)
(o
= axial
thrust
= specific
= o°j
impulse
deflection, lb f-sec/lbm = flowrate Odlnj
This
equation
added
by surplus
injectant,
of the liquid
estimated (N-sec/kg) of liquid
from
injectant,
lbf (N)
injectant a plot
in the side direction
of Isp (s)versus
lbm/sec
0 (e.g.,
at 0 ° figs. 35 and 42),
(kg/sec)
= the equivalent half angle of the nozzle from the injection point to the exit, determined as the angle between the nozzle centerline and a line from the injection point to the exit rim, deg
is applicable
to both
extrapolated to 0 ° deflection augment axial thrust. These
angle effects
conical
and
contoured
nozzles
(ref.
126).
The
Isp(s
)
is used because it best represents the LITVC effects that are the increased pressures on the exit cone caused by
injectant energy and mass and by injection shocks. I_p (s) values obtained at larger deflection angles should not be used in equation (14) because these Isp (_) values have been reduced by losses in measured side forces due to the circumferential spreading of the side forces around the nozzle. Such losses detract from side thrust but not from axial thrust. Correlation the data in reference 121 shows an accuracy within -+ 10% for nozzles with expansion
with ratios
up to 10. Equation (14) may underestimate the added thrust when applied to long contoured nozzles having expansion ratios greater than 20 with injection far upstream from the exit. This result occurs because the wall angle at the center of this region of added pressure usually is significantly pressure nozzles,
larger
than
the
equivalent
half-angle
OLin j.
The
center
of the
region
of added
generally is located a short distance downstream of the injection orifices. then, the value for the half-angle used in equation (14) will be less than
For such the local
wall angle at the injection point but greater than _inj as defined above; this effective half-angle is estimated from experience. The added thrust due to expending injectant in the nozzle is more accurately estimated by the use of data from subscale tests or, if an adequate mathematical model exists (sec. 2.2.3), by integrating the product of the added pressure and the tangent A detailed
of the
wall angle
performance
over
analysis
the
nozzle
wall
of a liquid-injectant
47.
156
area
affected. dump
system
is presented
in reference
3.2.2.6
ADAPTATION
The
motor
for system
OF THE
design
shall
MOTOR
provide
FOR
injector
LITVC
mounts
and ports
and
external
brackets
support.
The nozzle design should make provision for holes and mounts for the injectors. The metal orifice ends of the injectors should be recessed sufficiently inside the injection port (fig. 29) that they will not be damaged by heat flux. The heat flux at the inside end of the injection port should be estimated (refs. 134 and 135). The port hole should be made conical to fit the shape of the liquid jet and only large enough to permit the jet to be discharged without momentum losses due to wall friction. Small port hole size will minimize heat transfer into the
hole
and
the
exhaust-gas
Provide liner.
will minimize
erosion
at the
hole
edges
that
results
from
impingement
of
flow.
a gas-tight
The injector wail should
the
seal such
as an O-ring
mount, to which the have sufficient strength
at the interface
between
the
injector
and
the nozzle
injector will be bolted, and its attachment to the nozzle to withstand the full injector reaction thrust in addition
to other loads. If possible, the entire LITVC system should be mounted on the nozzle avoid any problems of differential motion between the nozzle and the motor aft dome skirt. If this mounting is not possible, provide flexible lines or expansion joints.
Mechanical and thermal analyses made of the nozzle and related LITVC
system
the major part these vectoring
The
only
that
occurs
and
to the
(i.e., stress, gas flow, heat transfer, and erosion) should be portions of the motor. Loads due to the weight of the
intermittent
TVC
Pressures
on the
of the vectoring force must be included in these pressures on the exit-cone wall can be estimated
thermal
problem
around
and
of consequence immediately
to or
due
downstream
to LITVC of the
exit
cone
walls
analyses. The (ref. 136).
is the
severe
injection
port
that
heating holes
produce
distribution
of
and erosion (fig.
34).
The
amount of erosion depends on the exhaust flow properties, the reactivity of the injectant, and the type of ablative material used. To predict this erosion, use methods for predicting erosion that include the capability for treating the effects of chemically reactive injectant and exhaust-gas mixtures (refs. 158 and 159). The analysis should be cross checked by scaling known LITVC hole erosion to the relationships being used as the scaling factors. typical
heating
and erosion
patterns
is shown
design condition, appropriate heat-transfer A design of an injector mounting pad with in figure
157
50.
Injector surface
Eroded
mounting-pad
surface
V/I/I//lllA
7075
aluminum
alloy
silica/phenolic Graphite
cloth/phenolic
Figure 50. - Typical LITVC port configuration showing erosion and char patterns.
3.2.3
Performance
Test
data
shall
operational Test
data
from
be
demonstrated
3.2.3.1
support
the
and Testing
LITVC
system
development
and
demonstrate
capability. other
being designed determine the should simulate
Evaluation
LITVC
should general
systems
be used configuration
transformed
for
supported by data from actual motor conditions. at test
conditions
PERFORMANCE
Performance to the LITVC
data
from
system
other
FOR
actual
correlated
by analysis
to the LITVC
design and motor tradeoff system. As soon as possible,
subscale tests The full-scale
simulating
DATA
and
conceptual of the motor
conducted under motor operating
flight
studies to these data
test conditions that capability must be
conditions.
DESIGN
LITVC
programs
required..
158
shall
be demonstrably
applicable
Existing LITVC data that canbe transformedto the required LITVC systemshouldbe used for motor optimization studies,tradeoff studies,and preliminary conceptual design.These studiesmust be conducted early in the program to determinethe adequacyof the data and to define neededadditional data so that a test programcan be commenced. The data obtained from various sourcesmust representthe variation of side-force specific impulse with injectant flowrate, injector location, injection angle,injection pressure,orifice size, and orifice spacing.The available test data should be transformed to dimensionless form except for the side-force specific impulse, which is retained in units of lbf-sec/lbm (N-sec/kg). Each of the designvariablesshould be presentedas a family of curves,wherein all other parameters are constant at one or more arbitrary configurations. These configurations should be selectedto representarange that includesthe optimum design.An example of this practice is shown in figure42 for an evaluationof injection pressure.Other plotting formats as illustrated in figures 36 through 40 should be used if they are more convenient. Data that have originated from rocket motors that were significantly different from the designmotor should be transformed; use the dominant physical lawsasdescribed in section2.2.3.1 to make them applicable. The suitability of the transformed data to the design motor must be evaluated for consistencyand agreementby using data from different sourcesplotted on the samegraph. If the results form a continuous plot with little scatter, the results can be usedwith confidence. If the scatter is larger than can be tolerated within designspecifications,a test program must be initiated to generatedata in the expecteddesignrange.Awaiting test data could result in a delay in a program, and in such a period the transformeddata will be the only availabledata. Thesedata must be usedfor initial optimization studiesandpreliminary design;useengineeringjudgement to allow for an amount of error defined by data scatter. The results obtained with such data must be reevaluatedwhen test data in the expected designrangebecomeavailable.
3.2.3.2
SMALL-SCALE
Small-scale provide Small-scale transformation injection the test
tests
design tests
TESTS using
data not
should of other
system
parameters
otherwise
available.
be conducted test data. The
in
to obtain test motors
the
expected
data should
design
that are use rocket
range
shall
not available nozzles and
from LITVC
geometries that are scale models of the expected full-scale design configuration; motor chamber pressure should be the same as that of the design motor; and the
test propellant exhaust gas should be similar to that of the full size motor in temperature and in oxidizing species that are free to react. To obtain valid data, the test motor need not be a solid-propellant motor but can be a liquid propellant motor, a change that usually results
in cost savings
and
test
convenience
(ref.
159
121).
3.2.3.3
FULL-SCALE
A full-scale An
firing
evaluation
of the
DEVELOPMENT
TESTS
test shall evaluate
the LITVC
full-scale
LITVC
system
system
should
design.
be conducted
on
the
first
static
test
firing of the motor, so that design changes can be incorporated without causing significant program delays or increased costs. Measurements must be made of all parameters affecting design of the LITVC system and the results used to reevaluate the injector valves, injectant requirements, and injectant tank size. If the motor is to operate at high altitude, the test should be conducted at the corresponding ambient pressure. The final LITVC design must be evaluated in static test firings, so that its actual performance and characteristics can be known
for flight-control
may be necessary
3.2.3.4
use. Vertical
OPERATING-CAPABILITY
Procedures operation
orientation
of the motor
or at least
of the liquid
tanks
for such-tests.
for
the
TESTS
component
of the LITVC
system
testing,
assembly
shall be developed
installation, and
checkout
and
documented.
The functional capability of all components of the LITVC system should be determined by test before assembly. These tests should employ pressurized gas and liquid supplies and control connections as necessary to simulate operating conditions. The bench testing should be performed with an inert liquid (e.g., Freon) clean. If a reactive or nonevaporating injectant thoroughly
cleaned
after
testing.
After the system has been should be checked during satisfactory documented. The
other
that will evaporate and leave the components is used in bench testing, components must be
operating The critical
assembled and installed on the motor, storage or launch readiness as often
capability. components
components
including
Procedures for these are the gas pressurization the
meters,
check
piping, and fittings are important but they are not procedures for correct installation, filling, operation, the rocket motor should be documented. If a gas generator is used, and resistance. If a tank pressure checked The
more
monitored
gage, should for continuity sensitive
be monitored, and resistance.
electric
by feedback
the igniter squib should of inert gas under high
portions
and
of the
the
squib
injectors
signals.
160
valves,
the critical components as necessary to ensure
check operations subsystem and injectant
should be the injectors.
tank
and
bladder,
nearly as sensitive to malfunction. Also, and unloading of the LITVC system on
be checked at low voltage for continuity pressure is used, its pressure, sensed by valve
should
at its outlet
be actuated
should
be electrically
and their
movements
APPENDIX Conversion
Physical
quantity
of U. S. Customary
U.S. customary
Angle
degree
Density
lbm/ft
Force
lbf
unit
3
A Units
to Si Units
SI unit
Conversion
radian
1.745x10
kg/m 3
16.02
N
4.448
factor a
-2
t
in.
cm
2.54
ft
m
0.3048
lbm
kg
0.4536
Ibm/Ibm-mole
kg/kg-mole
1.00
Peel strength
lbf/in.
N/cm
1.75
Pressure
atm
N/m 2
1.O13x10
psi
N/m 2
6,895x103
psi
N/cm 2
0.6895
lbf-sec/lbm
N-sec/kg
9.80665
Stress
psi
N/m 2
6.895x103
Temperature
oF
K
oR
K
K= 5(°R)
oF
K
K= 9"_--(°F )
oR
K
K = 95---(°R)
in.-lbf
m-N
0.1 130
Length
Mass
Molecular
Specific
weight
impulse
Temperature
Torque
difference
s
K:-_9(°F
+ 459.67)
aMultiply value given in U. S. customary unit by conversion factor to obtain equivalet_t value in SI unit. For a complete listing of conversion factors, see Mechtly, E. A.: The International System of Units. Physical Constants and Conversion Factors. Second Revision, NASA SP-7012, 1973.
162
APPENDIX
B
GLOSSARY*
Definition
Symbol A
Appears
reinforcement material constant value of elastomer shear modulus superimposed
eq. (3)
pressure
C
conversion
d
distance from point of liquid nozzle exit, in. (cm)
do
diameter
of the discharge
injector,
in.,(cm)
factor,
throat
t44 in. 2/ft2
diameter,
eq. (13)
injection
orifice
dt
nozzle
E
hoop modulus of elasticity ment, psi (N/m 2)
F a
axial component lbf(N)
U S
affecting with
In
to
of the
in. (cm)
figs. 39 and 42
fig. 36
of reinforce-
of the rocket
fig. 43
motor
fig. 19
thrust,
figs. 35,
36, 37,
38, 39, 40, and 42 and eq. (14)
side force due to liquid injectant, i.e., component of the total rocket motor thrust perpendicular to the motor axis,
figs. 35 - 42
lbf(N) G
effective subjected
G o
elastomer to external
shear
modulus
pressure,
elastomer secant shear modulus (3.45 x 10 s N/m 2) shear stress
when
at 50 psi and no
externally applied pressure, at the temperatures expected in operation, psi (N/m 2) Divided into three sections:
Symbols, Material Designations,
163
eqs. (2) and (3)
psi (N/m 2)
and Organization
Abbreviations
eqs. (1), (3), and (6)
Def'mition
Symbol lsp(s)
side specific
impulse,
Appears
ratio
of side force
produced by injectant to injectant flowrate causing side force, lbf-sec/lbm (N-sec/kg)
integral
i@
values
ible-joint I _1)
and 1 032)
for calculation
of
table VIII, figs.40 and 48, and eq. (14)
table
fiex-
In
V
:
spring torque
integral
values
at angles
eq. (1)
fll and/_2,
respectively
I% i¢,
correction
factor
a function
of cone angle
correction
factor
a function
of cone angle
distance
L
from
plane,
weight
Ibm/Ibm-mole Math
Mini
eq. (7)
to reinforcement
nozzle
fig. 18 and
stresses,
throat
stresses,
to nozzle
exit
in. (cm)
molecular
M
to elastomer
number
at the point
of pressurization
gas,
,
fig. 18 and eqs. (9) and (10) figs. 35, 36, 37, 38, 39, and 42 eq. (13)
(kg/kg-mole) of the rocket of secondary
expected
exhaust
gas
fig. 43
injection
MEOP
maximum
operating
pressure
MS
Margin of Safety: fraction by which the allowable load or stress exceeds the design
text eq. (5)
load or stress, MS -
number
n
1 R
of elastomer
1
rings in a flexible
joint number
ninj
P
Pal/l
Pc
b.
of injectors
operating
eqs. (6), (9), and (10) eq. (12)
pressure,
psi (N/m 2)
eq. (13)
ambient
air pressure
fig. 36
motor pressure: bustion chamber
pressure in the comof the rocket motor
eqs. (4), (7), and (9), figs. 25, 36; 38, 39, 40, 42, 43, and 48
164
Definition
Symbol
liquid injectant injector valves
Appears In
pressure
delivered to the
figs. 35,36138_ 40, 42, and 43
39,
static pressure of gas flow in the nozzle
fig. 25
static pressure of gas flow in the nozzle at the injection location
fig. 43
QLS
quadruple
various places in text
R
(1) ratio of design load or stress to the allowable load 0r stress (2) universal gas constant, lbf-ft/lbm-mole °R (J/kg-mole-K)
eq. (5)
inner joint radius
fig. 12
outer joint radius
fig. 12
pivot radius of joint measured from geometric pivot point, in. (cm)
fig. 12 and eqs:: (6), (7), (9), and (10)
Ps
_,ai
Rp
- lap shear:
eq. (13)
Ro+Ri 2
Rp-
eqs. (1) and (2)
ri
Rp -
nte/2
ro
Rp + nt_/2
eqs. (1) and (2) J
T
absolute
eq. (13)
Tq
flexible-joint (m-N)
temperature, °R (K) spring torque,
eqs. (1) and (2)
in. - lbf
• ,r,.
Ts,
inj
static temperature of the gas flow in the nozzle at the point of injection, °R (K)
fig. 43
time from start of motor
calculation procedure in sec. 3.2.1.5 ,
•
t_
A
thickness of elastomer
operation,
ring in flexible
joint, in. (cm) tr
thickness
of reinforcement
joint, in. (cm)
165
in flexible
sec
figs. 12 and 19, eqs. (6) and (7) figs. 12 and 19, eqs. (6), (7), and (10)
Definition
Symbol Vinj
velocity point
AppearsIn
of gas flow in the nozzle
of injection,
weight
flowrate
the rocket
ft/sec
fig. 43
(m/see)
of the exhaust
motor,
at the
_ '_ i :
lbm/sec
gas from
figs. 36, 38, 39,40, and 42
(kg/sec)
weight flowrate of the injectant injector into the rocket nozzle,
figs. 39, 40, and 41
from the lbm/sec
and eq. (14)
(kg/sec) X
distance
measured
line from containing ports, O/
O/1
O/inj
along
the nozzle
the nozzle throat to a plane the centers of the injection
divergence
half-angle
of nozzle
exit cone,
figs. 36, 38, and 49
fig. 42
divergence half-angle cone measured near
fig. 42
of a contoured exit the exit cone lip, deg
equivalent nozzle half-angle from the injection point to the exit plane, determined as the angle between nozzle centerline and a the injection
deg; for a conical angle,
point
nozzle,
to the exit
joint,
the angle between
the nozzle
rim,
fig. 12 eqs. (9) and (10)
deg fig. 12 and eqs. O),
inner and outer joint angles defining flexible joint geometry, deg shear
eq. (I4)
Otinj = ot
centerline and a line from the geometric pivot point to the middle of the flexible
strain
quadruple-lap A
deg
divergence half-angle of a contoured exit cone measured near the nozzle throat, deg
joint
and 42
in. (cm)
line from
3'
figs. 35 - 39
center-
incremental
in elastomer shear change
166
measured
(2), (4), (9), and (10) in
sec. 2.1.7
test in a quantity
eq. (14)
Definition
Symbol
X
angle between
Appears
the nozzle
centerline
line from an injection port side exit-plane rim, deg e
nozzle
expansion
of exit plane
ratio,
and a
In
fig. 49
to the opposite-
defined
area to throat
figs. 25,35,38,39, 40,42,43, and 48
as ratio
area
/
e inj
expansion
ratio
of the nozzle
exit cone
at
the plane of the injection ports, defined as the ratio of the area at this plane to the throat area 0
(1)
angle between motor centerline and centerline of nozzle when nozzle is rotated
(2)
P
about
density,
lbm/ft
fig. 13;eqs.(1),(2), (6),and
and
figs. 35,36,38,39, 42, and 49;eq.(14) eq. (13)
applied
motor
pressure
eqs. (3) and (4)
configuration
compressive hoop stress in reinforcements due to motor pressure, psi (N/m 2)
eqs. (9) and (10)
resultant compressive hoop stress forcements due to motor pressure nozzle vectoring, psi (N/m 2)
eq. (1 1)
in reinand
o_
compressive hoop stress due to nozzle vectoring,
in reinforcements psi (N/m 2)
eqs. (10)
7"
shear
as measured
sec. 2.1.7
stress
in elastomer
quadruple-lap
re
rr
shear
shear
psi (N/m 2)
resultant
shear
shear
stress
vectoring,
due to motor
stress in elastomer and nozzle
in elastomer psi (N/m 2)
167
in
and (11)
test, psi (N/m 2)
stress in elastomer
pressure,
motor pressure (N/m 2) rv
(10)
point,
3 (kg/m a)
relating
and flexible-joint
O" r
pivot
deg angle between motor centerline deflected thrust vector
parameter
Op
the effective
figs. 36,40,43, and 48
eqs. (7) and (8)
due to
vectoring,
due to nozzle
eq. (8)
psi
eqs. (6)and
(8)
Symbol
Definition
(1) (2)
Appears
flexible-joint cone angle, deg discharge angle of the injectant relative to the nozzle centerline,
Rp 2"4 cos
_2 :
3283
eq. (12)
fl
:
eqs. (9) and (10)
tr 3 + tr COS2 /3{Rp 2 (f12 -
/31) 2 - 3283
tr 2}
Identification
205,305,
220,231,and
608
trade
names
of Hughson
name
fiber
(polyethylene
DC 1255
trade
designation
elastomer
polymeric its length
: ERL 2256
of
E. I. du Pont
FM4030-190
material
:
44125
and
trade
of Fiberite
trade
designation
adhesive
epoxy
trade
molding
E. I. du Pont
designation
compound 20-WS-45).
Inc. for a polyester
(now
168
of General available
for silicone
can be stretched
to twice
length
terpolymer
Corp.
Carbide
Corp.
rubber
to its original
diene
Carbide
for bisphenol-A
Corp.
for
for phenolic
epoxy
epoxy
resin
resin
viscosity
impregnated
chopped
material
of FMC Corp.
of
& Co.,
temperature quickly
propylene
of Union
designation
Corp.
at room return
trade designation modifier
trade name fluorocarbons
Freon
that
for ethylene
S-glass compression FMC 47
de Nemours
of Dow Corning
trade designation of Union with viscosity modifier
:,_ERR4205
Co. for primer
terephthalate)
and on release
abbreviation
EPDM
Chemical
systems trade
Dacron
GTR
38,39,40,42,48, and 49
and the side
Material
Chemlok
fig. 12 and eq.(4) figs. 23,35,36,37,
jet deg
angle between side force resultant force vector of the ith injector
1
In
for epoxy
resin system
de Nemours
Tire only
and from
& Co.,
Rubber B.
F.
Co.
Inc.
for
a series
for natural
Goodrich
Co.
of
rubber as BFG
Material
Identification
f
GTR V-45
trade designation butadiene/acrylonitrile
of
General Tire and Rubber compound (now produced
Co. for silica-filled by HiU-Gard Rubber
Co.) trade
Hypalon
name
of
E.
chlorosulphonated IRFNA
inhibited
K1255
trade
LOX
liquid
oxygen,
MHF-3
mixed
hydrazine
Neoprene CN _ _ and Neoprene W
trade
red fuming
designation
name
synthetic
1-1 copolymer
nitroso
AFE-110
carboxy-nitroso Laboratory now
rubber
:_: S-glass
_':: S-901
rubber
acid, propellant
grade
grade
Corp.
&
Co.,
Inc.
for
per MIL-P-7254
for silicone
rubber
per MIL-P-25508
de Nemours
& Co., Inc. for general
of trifluoronitrosomethane polymer
purpose
developed
a butyl
by
rubber
by Parker-Hannifin high-energy
high-strength
and tetrafluoroethylene the
Air
Force
Materials
OH)
B-591-80;
an elastomer, either the hevea brasiliensis
trade
Nemours
(polychloroprene)
kerosene-base MIL-P-25576
Fiberglas
de
synthetic
fuel
(WPAFB,
Parker
Pont
Carbide
propellant
manufactured RP-1
nitric
of E. I. du Pont
rubber
B-591-8
du
of Union
rubber
nitroso
Parker
I.
polyethylene
used
for
O-rings;
Corporation
hydrocarbon
a synthetic tree
compound
fuel,
or a natural
MgO-A1203-SiO2
glass
propellant
compound
developed
by
grade
obtained
per
from
Owens-Coming
Corp.
designation
of
Owens-Corning
with aging surface
finish
S-904
trade designation non-aging surface
of Owens-Coming finish
$34/901
trade
of Owens-Corning
designation
glass fiber cloth
169
Fiberglas
Corp.
for S-glass fiber
Fiberglas
Corp.
for
Fiberglas
Corp.
S-glass
for woven
fiber
S-901
Identification
Material
TCC TR 3005
trade designation of Thiokol Corp. for natural
Teflon
trade
name of E. I. du Pont de Nemours
tetrafluoroethylene Thiokol
ST
Tonox 6040
rubber formulation
& Co., Inc. for a series of
polymers
trade name of Thiokol Corp. for polysulfide trade name of Uniroyal, Inc. for a blend curing agent for epoxy and urethane
elastomer of aromatic amines used as a
resins
_
Tygon ST
trade name of U. S. Stoneware
Co. for polyvinyl
UDMH
unsymmetrical
Viton A
trade name of E. I. du Pont de Nemours & Co., Inc. for a copolymer vinylidene fluoride and hexafluoropropylene
17_PH
semi-austenitic
301 304 347
designations
410
martensitic
2024
wrought
4130 4340
high-strengtl_
6061-T6
wrought aluminum temper T-6
alloy with Mg and Si as principal
7075-T6
wrought T-6
alloy with Zn as principal
dimethylhydrazine,
precipitation-hardening for austenitic
chromium aluminum
170
grade per MIL-P-25604 of
stainless steel
nickel-chromium
steels
steel
alloy with Cu as principal
martensite-hardening
aluminum
propellant
chloride
alloying element
low-alloy steels
alloying elements,
alloying element, temper
ABBREVIATIONS Identification
Organization
ABL
Allegany
ABMA
Army
AEDC
Arnold.Engineering
AFRPL
Air Force
Rocket
AIAA
American
Institute
BOWACA
Bureau
CPIA
Chemical
DAC
Douglas
ICRPG
Interagency
JANAF
Joint
Army-Navy-Air
JANNAF
Joint
Army-Navy-NASA-Air
JANAF-ARPA-NASA
Joint
Ballistics
Ballistic
Laboratory
Missile
Agency
Development Propulsion
Center
Laboratory
of Aeronautics
of Weapons
Advisory
Propulsion Aircraft
and Astronautics
Committee
Information
Agency
Company
Chemical
Rocket
Propulsion
Force Force-Advanced
National
Aeronautics
LMSC
Lockheed
Missiles
and Space
Company
LMSD
Lockheed
Missiles
and Space
Division
LPC
Lockheed
Propulsion
NAVORD
Naval Ordnance
Command
NOTS
Naval Ordnance
Test
SAE
Society
and Space
UTC
United
WPAFB
Wright-Patterson
of Automotive
Company
Station Engineers Center
Air Force
171
Group
Force
Army-Navy-Air
Technology
for Aeroballistics
Base
Research
Administration
Project
Agency-
REFERENCES 1.
Anon.:
Pintle
2.
Schaefer,
Thrust
R.
Vector
L.; and
Control.
Wilson,
K. C.:
Propellant Rockets. Bulletin June 1960, pp. 203-225. 3.
Amick, Located
4.
Strike, Located
6.
7.
Facility, S.; Lippert, ABL/Z-66
Podell,
H. L.:
Anon.:
Rocket
Fuller,
12.
13.
14.
C. M.;
Nozzle
Propellant
for
Trajectory
Group,
Vol.
Control
of Solid
2 (AD-317113),
CPIA,
P. C. Y.: Experimental Interaction Effects of Forward WTM 276, University of Michigan, March 1963. J. S.: AEDC
Interactions TDR-63-22
Produced by (AD-401911),
Sonic Lateral VonKarman
Jets Gas
1963.
P. F.; and Drewry, Hercules
Inc.,
Propulsion
Control
D. G.: A Unique
December
1963.
Subsystem
(U).
System.
W. F.: The
Study
Jones,
D.
A. T.:
Nike-Zeus
Unitized
CPIA
Thrust
Publ.
LMSC A120083,
Vector
18, Vol.
Lockheed
for a Simplified
Pershing
Manned
1960,
Propulsion
of
Certain
System. pp.
for a Simplified
Co., December
CPIA, June
June
Control
1, CPIA,
June
Missiles
and Space
Space
Vehicle.
NASA
Manned
Space
Vehicle.
DAC
16th
JANAF
Solid
1964.
System.
1960,
pp. 85-109.
Bulletin
of 16th
Bulletin
of
JANAF
Solid
Propellant
Group,
111-127.
Thrust
Vector
Control
Systems.
DAC
SM-27957,
Douglas
1961.
J. E.; Miltenberger, Thrust
Vector
Supporting
Research
Report
J. E.; and
Murray,
L.
1970,
E.;
Control -
pp.
Murray,
J. A.; _icario,
for Advanced
1969,
J. A.:
(AD-513921),
December
Steering Aircraft
Propulsion
Correlation
Magnitude,
DCN-N-5-14
Steering
of Head-End
1 (AD-317112),
CPIA,
Co., October
McNeer,
P.:
of Head-End
McDonnell-Douglas
Vol.
Aircraft
Inc./ABL,
Spike
Solid
Deitering, Stream.
Missile
II Study
and
Group,
1 (AD-317112),
McNeer,
1967.
1966.
Hickey,
(U).
Isentropic
JANAF
and Attitude
(N66-16017),
Mitchell,
Vol.
Velocity
G. M.: A Feasibility
Graves,
June
(CONFIDENTIAL)
March
Propellant 11.
The Shillelagh
CR-87450,
1962.
SM-48152 10.
April
T. E., Lease,
G. M.: Phase
Fuller,
Inc.,
(AD-349158L),
pp. 113-134.
CR-66173, 9.
ARO
System.
Co., May 8.
The
16th
W. T.; Schuelez, C. J.; and on Surfaces in a Supersonic
Kardon,
1963,
of
J. L.; Stubbleium, W.; and Chan, Side Jets on a Body of Revolution.
Dynamics 5.
NASA
Systems
Vol. 2, Hercules Thrust
Annual
Magnitude, Exploratory
1-59. (CONFIDENTIAL)
173
(U).
A.
Inc., December Thrust
A.;
and
Tulpinski,
ABL-TR-69-26
Vector
Development
1969.
Annual
(CONFIDENTIAL)
Control Report
J. E.: Thrust
(AD-507149),
for Advanced -
1970,
Vol.
Systems 2, Hercules
15. Anon.:PropulsionDevelopment Department Review.NOTSTP4100-6Part Ordnance
16. Wu,
Test Station,
Jain-Ming;
Control.
and
AFRPL
June Lee,
1 (AD-382851L),
Naval
1967.
Shen
TR-67-202
Ching:
Electric
(AD-822593),
Air Discharge
University
in Supersonic
of Tennessee,
Flow
September
for Thrust
veetor
1967. i'
"17.
Wilson, J. W.: Corp./Hercules
18. Nance, TR,70:52
Final Report, Poseidon Inc. (A Joint Venture),
B.: Advanced (AD-509374),
19. Marugg,
H.
C.;
20. Marugg,
H.
Bratton,
and
TMC-68-4-9-Bk2 (CONFIDENTIAL)
21. 22.
Control
23.
E.
O.:
Bratton,
Design,
Control
Rocket
25. 26.
Book May
1 (13). 1969.
C.
R.:
100-Inch
Motor
Program,
Book
2 (U).
Thiokol
Chemical
May
1969.
and
Corp./Wasatch
for Omniaxial Movable Co., April 1966.
Test
NASA
Demonstration
of
Omnidirectional
CR-72889,
June
Poseidon
Report-1973,
Propulsion
SE083-A2AC3HTJ-2,
27. Wilson,
W. G.:
Investigation
Mill Order
TES
Hercules
Poseidon
Nozzles
Flexible
(Lockseal).
Seals
for
Hercules
Second 74475,
Technical
Inc./Thiokol
an
Omniaxial (AD-385084),
Inc./ABL,
Stage Hercules
Review
Report-
Chemical
Corp.
Elastocomposite Inc./ABL,
February
Vector
Flexible Seal Movable Thiokol Chemical
January
AIAA
1 July (A Joint
Joint,
Final
Paper
1974,
Report
pp.
73-1262,
through Venture),
Thrust Vector Research and 115-199.
AIAA/SAE
30 September October Task
9th
1973.
1973.
II A-5. Poseidon
1971.
*Dossier,f0r design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
174
Thrust
AFRPL
1971.
Sherard, H.: Development of Advanced Flex Joint Technology. Propulsion Conference (Las Vegas, NV), Nov. 5-7, 1973. Anon.:
Div.,
J. E.; and Murray, J. A.: Integral Rocket Ramjet Booster System Demonstration (U). DCN-N-37-23, Annual
Exploratory Development (CONFIDENTIAL)
AFRPL
Program, Div.,
Motors.
L. E., McNeer, Nozzle Eject
'and
Chemical
Motor Demonstration Chemical Corp./Wasatch
ReportDevelopment and Demonstration of Thrust Vector Control. AFRPL TR-67-196, Div., October 1967.
24. Miltenberger,
Thiokol
100-Inch Thiokol
an Elastomeric Seal Lockheed Propulsion
Fabrication
of Large Solid
Anon.: Final Nozzle for Corp./Wasatch
TWR-2486,
R.:
(AD-502027L),
Anon.: Development of TR-66-11:2 (AD-373032), Wong,
Rep.
C.
(AD-502026L),
C.;
Joint.
Dual Chamber Propulsion System Component Design Report (If). Thiokol Chemical Corp./Wasatch Div., May 1970. (CONFIDENTIAL)'
and
TMC-68-4-9-Bkl (CONFIDENTIAL)
C3 Joint Venture July 1967.
Unpublished. Collected
source material
28. White,T. C.:ThrustVectorControl- Elastocomposite Joint(U).DCN-N-17-6, AnnualExploratory Research Report- 1971,Vol.2, Hercules Inc./ABL,February1972,pp. 1-68.(CONFIDENTIAL) 29.Miltenberger,L. E.: Elastocomposite Joint-Thrust Vector Control (U). DCN-N-26-2, Annual Research andExploratoryDevelopment Report- 1972,Vol.2. Hercules Inc./ABL,December 1972, pp. 119-202. (CONFIDENTIAL) 30. Hurley,L. H.; and Kimmel,N. A.: Applicationof ControllableSolidsin ReentryMeasurements Program (U).Rep.TR-0059($6816-89)-1, Aerospace Corp.,Aug.31,1970.(CONFIDENTIAL) 31. Bertocci,R. P.: The Nike-ZeusPropulsionandJetheadControl Systems(U). Bulletinof 18th JANAF-ARPA-NASA SolidPropellant Group,Vol. 1 (AD-330129), CPIA,June1962,pp.161-179. (CONFIDENTIAL) 32. Kirchner,W. R.: Development of Advanced PolarisFirst StagePropulsionSystem(U). Bulletinof 18thJANAF-ARPA-NASA SolidPropellant Group,Vol. 1 (AD-330129), CPIA,June1962,pp.3-27. (CONFIDENTIAL) 33. Ellis,R. A.: Development of a Carbon-Carbon Nozzlefor the TridentI (C4)ThirdStageMotor(U). CPIAPubl.242,Vol. I, CPIA,November 1973,pp.89-115. 34.
Sinclair, C. A.: Development CPIA Publ. 242, Vol. I, CPIA,
35.
Goddard,
S. G.: Demonstration
Vol. I, Thiokol 36.
Schoen, Techroll
of a High November
Chemical
Performance Third Stage Motor for the 1973, pp. 117-145. (CONFIDENTIAL)
of Advanced
Corp./Wasatch
ICBM Components
Div., January
Program,
Phase
Trident
I (C4)
(U).
I. AFRPL-TR-73-37,
1974.
c_. L.; Bahnsen, "_" Seal Movable
E. B.; Conner, G. E.; and Grimsley, Nozzle System. AFRPL-TR-73-47,
J. R.:
Propulsion
J. L.: Exploratory Development for the Vol. I, United Technology Center, June
1973. 37.
38.
Crooks, Group,
Vol.
Anon.:
156
CPIA,
Inch
Motor
1965.
Nance,
P. D.:
Hirsch,
N,
(AD-371800), 41.
Waldeck, Rep.
Diameter
AD-365662,
August
Final
(AD-376999), 40.
Report,
Thiokol A.;
June
Submerged
Chemical
Slegers, Air Force
L.;
1962,
pp.
and
and
Thrasher,
R. V.; Deslauriers, Corp.,
113-122. Program.
Nozzle
I.:
AFRPL-TR-65-4 Thiokol
Development,
Div., June D.
JANAF-ARPA-NASA
Air Force
E. J.; and McVey,
(Washington,
175
D.C.),
Propellant
(5 vols:
AD-365660,
Chemical
Corp./Wasatch
Div.,
Appendix
D. BSD-TR-66-31/C
1966.
Gimballed
(Edwards
Solid
(CONFIDENTIAL)
AD470452),
Gimbal
Command,
of 18th
Nozzle
Corp./Wasatch
Systems
Pneumodynamics
Bulletin
Movable
AD-365663,
G. H.; Hensley,
6602-1,
System.
I (AD-330129),
AD-365661,
39.
Skybolt
Integral
Nozzle.
Base, CA),
F. D.: Flexible
September
1959.
AFRPL-TR-64-172
December Skirt
1965. Nozzle
(CONFIDENTIAL)
Program.
42.: Waldecki_G. H.: :_
Skirt
Nozzle
Program
(U). Rep. 6602-i,
Pneumodynamics
Corp.,
July
1960.
Flexible
Skirt
Nozzle
Program
(U). Rep.
Pneumodynamics
Corp.,
November
(CONFIDENTIAL)
43.
Waldeck,
:,
1960. 44.
G. H.:
R. E.: Reinforced
Rocketdyne
45.
Hoover,
Div., G. H.:
.., _./._.: k(AD7373908), 46.
6602-k,
(CONFIDENTIAL)
Spann,
• : .
Rains,
Grain
North An
D. A.: Solid Solid
Advanced
American
Nozzle
1966,
Propellant
Development
Aviation,
Omnivector
CPIA , June
Interagency ,,
Flexible
for
pp. 813-842.
Motor
Propulsion
Thrust
AFRPL-TR-66-239
(AD-377073),
1966. Vector
Control
(U).
CPIA
Publ.
111,
Vol.
(CONFIDENTIAL)
Thrust
Meeting,
Program.
Inc.,•October
Vector
Control
Vol.
1
I and
II.
2
• ....
System
for Titan
(AD-352176),
CPIA,
III (U). Bulletin
May
1964,
of 20th
pp.
225-262.
_, (CONFIDENTIAL) y_.;
:
47.
i.i
.
Anon.:
TVC
(Sunnyvale, "48.
Systems
Analysis,
CA), April
Parts
UTC
4404-70-330,
United
Technology
Center
1971.
Huff, W. G.: Theoretical Control System (LO.
Analysis and LMSC 806591,
Functional Description Lockheed Missiles
of the Polaris A3 Thrust and Space Corp., May
Vector 1967.
(CONFIDENTIAL) 49.
Collis,
D. R.;
and
Rimington,
D.
A.:
Thrust
_ _ .;Liquid Injection (U). Bulletin of :, : :_(AD-352176), May 1964, pp. 263-281. 50.
Conklin,
.... 51.
Anon.: , NASA
52. ..
C. L.: The Sprint
CPIA, June
1968,
Thrust
Vector
C. G.:
20th Interageney (CONFIDENTIAL)
Vector
System
Chemical
Development
Control
Control
of the
Solid
System
Minuteman
Stage
Propulsion
Meeting,
(U). CPIA Publ.
167, Vol.
II Motor
CPIA,
by
VoL
and
Study
Corp.,
Program,
June
1, (AD-389918),
Final
Report
and
Final
Report
Summary.
1 1970.
Demonstration
, Control System for LSRM - Final Report AD-847113, and AD-847114), Thiokol
of
a Chamber
(U). AFRPL-TR-68-166, Chemical Corp./Wasatch
Bleed Vols. Div.,
Hot
Gas Thrust
Vector
I, II, and III (AD-395219, October 1967. (VOL.
CONFIDENTIAL) 53.? Benj0ck, G,' F.: Design (AD-350933), Hercules 54.
,*Dossier available
of Propellant Inc., February
Gas Secondary Injection 1964. (CONFIDENTIAL)
Thrust
Vector
Ar_on.: Development of a Hot Gas Valve for Secondary Injection AFRPL-TDR-64-33 (AD-348778), Lockheed Propulsion Co., March 1964.
for for
design_ inspection
Criteria
monograph
at NASA
Lewis
1
(CONFIDENTIAL)
Control
CR-72727,Thiokol
Kennedy,
Thrust
pp. 219-232.
Vector
"Solid
Rocket
Thrust
Research
Center,
Cleveland,
176
Vector Ohio.
Control."
Unpublished.
Control
Thrust
Collected
(U). ABL
Vector
source
X!02
Control.
material
I
55. Brownson, H.: Feasibility Demonstration for Direct Chamber Bleed Hot Gas Secondary Injection Thrust Vector Control - Final Report. AFRPL-66-224 (Vol. 1, Bk 1: AD-800937; Vol. 1, Bk2: AD-800938; Vol. 2: AD-800939), Lockheed Propulsion Co., September 1966. 56. Anon.: Proportional Solid Propellant CR-637, November 1966.
Secondary
Injection
Thrust
Vector
Control
Study.
NASA
57.
Bonin,
58.
Drewry, D. G.; and Newman; R. M.: Methods for Thrust Vector Control of Solid Propellant Rockets. Bulletin of 16th JANAF Solid Propellant Group, Vol. 2 (AD-317113), CPIA, June 1960, pp. 227-248.
59.
Anon.: Stage I Minuteman (M55A1) Production Support -Final Report, Appendix C, Submerged Hot Gas Valve Development. BSD-TR-66-31 (AD-373063L), Thiokol Chemical Corp./Wasatch Div., May 1966.
0.
J.; Fitzgerald, J. E.; and Miller, E.: Hybrid Thrust Vector Control 572-F (AD-330226), Lockheed Propulsion Co., June 1962. (CONFIDENTIAL)
Anon.: Development and Demonstration of Flightweight Thrust Vector Control Hardware, Interim Progress Report No. 2 (U). AFRPL-TR-67-92 (AD-380241), Thiokol Chemical Corp./Wasatch: Div., March 1967. (CONFIDENTIAL) Anon.:
NASA Propellant
Gas Valve Scale-Up Program
Final Report.
Shipley, J. D.; and Drewry, D. G.: Application of Propellant High Pressure, High Acceleration Solid Propellant Rocket Hercules Inc., May 1964. 63.
4°
• 65:
••66.
67.
NASA CR-78004,
March 1966.
Gas Valves for Thrust Vector Control of Motors. Rep. ABL[Z.72 (AD-353317),
Robinson, D. J.; and Montgomery, L. C.: Sergeant Motor Jet Vanes (U). Rep. (AD-321938), Jet Propulsion Lab., Calif. Inst. Tech., June 1960. (CONFIDENTIAL)
JPL 20-136
Skirmer, E. H.; 504, and Werner, C. T.: X SAM-N-66 Talos Weapon Jet Vane AerodynamieReport, X230-A5 Booster Unit. Rep. BPD 4330, Bendix Corp., February 1955. Davis; R. E.; O'Callaghan, T.; and Selbert, J. R.: The Jetevator as a Vector Control Deyice, Development of the Polaris Jetevator. CPIA Publ. 18A, Vol. 4 (AD-346945), CPIA July 1963, pp. 391-412. Gowen; L. F.: Subroc Propulsion CPIA, June 1960, pp. 63-83. Edwards, Control.
68.
Systems (U). Rep. LPC
S. S.; and •Parker, Rep. LMSD,2630,
System.
Bulletin of 16th JANAF
G. H.: An Investigation Lockheed
Solid Propellant
of the Jetevator
Missiles and Space Co., February
Group, Vol. 1,
as a Means of Thrust
Vector
1958.
Huizinga, J.: Jetevator Effectiveness and Base Pressure Measurements for FTV-1 and AX Polaris Missiles Tested at NASA - Lewis Laboratory. Rep. LMSC 462055, Lockheed Missiles andSpace Co., November 1958.
177
69.
Anon.: XM-38 Solid Propellant Corp./Wasatch Div., June 1959.
70.
Anon.: Jet Tab December 1961.
71.
Hollstein, H. J.: Jet pp. 927-930.
72.
Anon.: Cooled BPAD-863-14544,
73.
Auble,
Thrust
Vector
Control.
Tab Thrust
Vector
18, Vol.
Tab Thrust June
75.
Anon.: SP-8115
76.
Anon.: NASA
77.
Harrison, T.; Colbert, L.; Dykstra, for Application of Lockseal to December 1966.
Rocket Actuators May 1973.
and
Lockheed
Rockets,
Vector
1963.
Anon.: 156-Inch Diameter Motor Jet Tab ProgramAD-357024, Vol. 2: AD-357025, Vol. 3: AD-357026, Lockheed Propulsion Co., January 1965.
Liquid SP-8090,
TU-68-5-59,
NASA
Operators.
Control
Firing
Vehicle
NASA
Space
H.; Sullivan, P.; and McCorkle, 260-Inch Solid Rocket Motor-
Criteria
Vehicle
Design
Joints.
Matthews,
to
80.
Chemical
W.:
Application
Propulsion
F.
Structural
81.
Wilson, E. L.: Structural pp. 2269-2274.
82.
Dunham, Loadings.
of
Large
Integrity
Analysis
Poseidon
Investigation
Deformation Survey
of Axisymmetric
Theory
1972,
(U).
Rep.
Motors.
CPIA Publ.
Solids.
AIAA
Monograph,
Criteria
J.: Design Study Final Report.
Woodberry, R. F. H.: Rapid Design Equations for Elastometallic No. Misc/6/50-1113, Hercules Inc./Bacchus, Nov. 30, 1973.
Analysis-
Co.,
1965,
Solid Rocket
Design
*79.
Joint
Space
Report. AFRPL-TR-64-167 (Vol. 1: 4: AD-357027, Vol. 5: AD-357028),
Galford, February
Unstable
and
Evaluation
for Large
*78.
J. E.: 1971.
Missiles
Chemical
pp. 241-286. Final Vol.
Space
Thiokol
vol. 2, no. 6, Nov.-Dec.
Full Scale Rocket Motor 1962. (CONFIDENTIAL)
CPIA,
Nozzles.
Rep.
800917,
J. Spacecraft
74.
Solid Rocket Motor (to be published).
I (U).
LMSC
Control.
L, J.: Jet
3 (AD-338667L),
Vol.
Rep.
Probe TVC Systems for Bendix Corp., September
C. M.; and Spielberger,
CPIA Publ.
Rocket Motor, (CONFIDENTIAL)
Task
II-A.
CPIA,
Inc./Magna,
to J. E. McNeer,
Chamber
229,
Monograph,
and CostEstimate NASA CR-83073,
Hercules
Memo
NASA
Analysis September
J., vol. 3, no.
and
Ref.
Design.
1972.
12, December
1965,
R. S.; and NickeU, R. E.: Finite Element Analysis of Axisymmetric Solids with Arbitrary Rep. SEL-67-6 (AD-655253), University of California (Berkeley, CA), June 1967.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
178
Unpublished.
Collected
source material
83.
Eringen, A. C.: Small Twist Superimposed Shell. Tech. Rep. 12-3, General Technology
84. Kafadar,
C. B.; and
Hydrostatic (Lawrenceville,
851 Danninger,
Eringen,
*87.
Program Department,
Cronkrite,
W. R.: Analysis
Actuation
Torque
Tests.
W. R.:
Analysis
Cronkrite, Torque
Tests.
Rep.
Solid
Tech.
Rep.
A. R.: Project
Quick
Spherical 12-2,
Turn
Movalbe
Stage
Poseidon
17-10203/6/40-475
of First
Stage
17-10203/6/40-455
Machined
(HA-05960),
Poseidon
Flexible
(HA-04006),
Inc./Magna,
Axial
89.
Lund, R. K.: Final Report - Cold Flow Tests Poseidon Thiokol Chemical Corp./Hercules Inc. (A Joint Venture),
90.
Shapiro,
A. H.: The Dynamics
and Thermodynamics
Fluid
Anon.: Nozzle Joint, Method for Actuation, Department of the Navy, Naval Ordnance Systems
Axial Deflection, Command, March
*92.
Briggs,
Test
93.
*94.
W.; and Greenleaf,
LPC 754-STR-3,
Anon.: Electric
R. D.:
893-F,
Lockheed
Final
G.:
Lockseal
Lockheed
Silicone Rubber Co. (Waterford,
Wells,
Vector for
October
the
and 1967.
Actuation
1967.
Report
(U).
Stage.
Rep.
Flow.
Vol.
Data
Item
TWR-2320,
1, Ch. 15. The
1953.
"91.
Rep.
Thrust
and
to
Corp.
Deflection
Deflection
C3 First and Second February 1967.
of Compressible
Axial
October
Allen, M. J.: Poseidon C3 Second Stage Phase II Design Compliance SE048-A2A01HTJ, Rep. 9, Hercules Inc., March 1971. (CONFIDENTIAL)
Press Co.,
Nozzle
Joint
Inc./Magna,
Ring Subject
Propulsion Co. (CONFIDENTIAL)
Flexible
Joint
Hercules
Spherical
Technology
Hercules
88.
Ronald
Annular
General
(U). Rep. NWC-TP-4794, Lockheed Naval Weapons Center, August 1971.
of Second Rep.
Elastic,
Bending.
C. R.; and White,
Control Demonstration Propulsion Development *86.
A. C.: An Anisotropic,
Pressure and Prescribed N. J.), December 1970. G. A.; Pignoli,
on a Finite Compression of a Thick Anisotropic Corp. (Lawrenceville, N. J.), December 1970.
Subscale
Propulsion
Co., Feb.
for Design Engineers. N.Y.), no date.
Report
Propulsion
Task
II-
Co., February
95.
Anon.: System
Poseidon C3 First Stage (U). Hercules Inc./Thiokol
96.
Anon.:
Poseidon
System
(U). Hercules
C3 Second
I and
General
Synthetic
Report
and Leak 1971.
Results
of Test
Tests.
Series
Stage
Phase
No. 4, 8, and 15.
Electric
Technical
Elastomer
Data
Book
Development
S-1D,
Program.
General
Rep.
LPC
1969.
II Design
Chemical
Corp.,
Compliance Mar. 24,
Report, 1971.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
179 i
43336C,
1968.
Phase II Design Compliance Report, Fleet Ballistic Chemical Corp., Mar. 16, 1971. (CONFIDENTIAL)
Inc./Thiokol
OD
\
Fleet
Ballistic
Missile
Weapon
Missile Weapon
(CONFIDENTIAL)
Unpublished.
Collected
source material
*97.
Peterson, M. R.: SF002-A2A01HTJ, March
*98.
1971.
Anon.:
*99.
*100.
*101.
Compound,
Command,
Weapons
August
Specification.
Weapons
Naval Ordnance
Systems
Command,
September
AnOn.:
Memorandum
- Elastomer
Tire and Rubber
Co., November
Anon.:
Test
Special
Special
G.;
Vector
Test
Povinelli,
WS 8008E,
Department
of Navy,
Naval
Specification.
WS 12006B,
Department
of the Navy,
1969.
44125,
Lots
14, 15, and 16. Ref.
No. GA 15729,'General
Stage
Buckle
Test
Unit
Ref.
No.
OML
77223,
Ref.
No.
OML
77222,
DO08
(D010).
Second
Stage
Buckle
Test
Unit
D005/D008.
Co., Aug. 4, 1967. H.;
and
CR-803,
J. F.; and Control.
Material
First
Report,
Armen,
NASA
Newton,
Item No. Venture),
Co., Aug. 4, 1967.
Propulsion
Structures.
Status Report (U)._Data Chemical Corp. (A Joint
1968.
Report,
Propulsion
Isakson,
Reliability Inc./Thiokol
1970.
Compound,
Lockheed
103.
Quarterly Hercules
Rubber
• 102. _ Anon.:
104.
II20A,
Natural
Lockheed
103.
Rubber
Systems
Anon.:
Phase No.
(CONFIDENTIAL)
Natural
Ordnance
Poseidon Submittal
October
Spaid,
ARS
Pipko,
A.:
Discrete
Methods
for
the
Plastic
Analysis
of
1967.
F. W.: Interaction
J., vol. 32, August
F. P.: Displacement
Element
of Secondary
1962,
pp.
of Disintegrating
Injectants
and Rocket
Exlaaust
for Thrust
1203-1211.
Liquid
Jets in Crossflow.
NASA
TN D-4334,
i_ebruary
1968. 106.
Kurzins, Density
*10"I.
"108.
R.
Hercules
Inc./ABL,
Grunwald,
111.
J.:
G. J.: Polaris
Huizlnga,
J.:
Liquid
Missiles
Anon.:
Chemical
Science
Corp.
Anon.:
Principles July
of
Thrust
Sizes
in Liquid
December
1968.
(CONFIDENTIAL)
Vector
and Second
Lockheed
and Space
Corrosion
Center
Rocket
Injection
Aspects
of Droplet
CR-1242,
Control
by
Fluid
Jets
Atomized
Injection.
in Low
Memorandum,
1961. B3 First
(Sunnyvale,
Stress
Technology
Measurement
(U). NASA
(U). LMSC 804506,
Lockheed *110.
F. H.:
Streams
Zeamer,
Report "109.
S. C.; and Raab, Supersonic
Thrust
of
Fluid
Test
(Sunnyvale,
Evaluation, CA), July
Injection
Thrust
Co., October
Control
1961.
1964.
Effectiveness
(U).
Vector
Control
Data
(CONFIDENTIAL) Rep.
LMSC
800877,
(CONFIDENTIAL)
Injection
May 1961,
Secondary
and Space
Vector
Co., August
CA),
Stage
Missiles
(U).
July
Rep.
1961,
Final
Nos.
R-l,
and August Report
(Titan
R-2, 1961. III).
and R-3
of P-27,
Dynamic
(CONFIDENTIAL) UTC-4802-67-181,
United
10, 1969.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
180
Unpublished.
CoUeeted
source
material
112.
Anon.: Titala III-M TVC System Seal Material Compatibility and Pyroseal Development 'UTC-4802-68-i04, United Technology Center (Sunnyvale, CA), April 22, 1968.
113.
Childress,
H. E.; and
Mastrolia,
Rep. 0162-06 TDR-9, September i9B5.
Vol.
E. J.: System 2 (Part
Support
1, AD-479227; =
Studies Part
Under
ProductiOn
2, AD-479205),
AnÙn.: Static Test Report TVC 50-Cycle/75-Day Hold Technology center (Sunnyvale, CA), September 1970.
115.
H0nma, Missiles
116.
Hess, F. D.: Diffusion of Perchlorate Solutions Through Elastomer TOR-669(6855-20)-I (AD-482982), Aerospace Corp., February 1966.
117.
Anon.: Atlantic
Freon Compatibility Studies. Research Corp., 1961-1962.
Perchlorate
Monthly
118.
Anon.: An Evaluation of Composite Teflon-Aluminum Propulsion System. NASA CR-84663, March 1967.
119.
Ross, L. G.; and LeFebvre, Ablative Performance. NASA
*120._
Hi'rsch, R. L.: Physical Properties and Aetojet-General Corp., June 24, 1963.
"121.
LeC0unt, R. L;: Fluid (BOWACA),Lockheed
• 122.
Grunwald, Lockheed
123.
"124.
and
Water
Progress
C. A.: Determination CR-72792, DeCember
Support
Aerojet
Recycle.
UTC
Solutions.
Reports
Foil
of the 1970.
Compatibility
1-10,
Rep.
Corp.,
Effects
of Strontium
4404-70-230.
Wu, Jain,Ming; Chapkis, R. L.; Ai, D. K.; and Rao, G. V. R.: Liquid National Engineering Science Co. (Pasadena, CA), July 1961.
LMSC
BSD-TR-66-93,
Subcontract
for
the
of Liquid
Surveyor
Thrust
LeCounL R. L.; et al.: Preliminary Data Release of Fluid Injection Thrust Vector LMSC DP/M-431, DP/M-557, and DP/M-722, Lockheed Missiles and Space Co., 1960.
"126.
Zeamer, R. J.: The Thrust. Memorandum,
on TVC
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." Unpublished. available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
on Nozzle
Memo,
Jet Effects
(U). TM 53-42-4,
"125.
Parameters 1965.
Vernier
Interoffice
Panel
LMSC 803311,
Vector
R. G.: Preliminary Results of P-29 Fluid Injection Lockheed Missile s and Space cO., November 196i.
Effect of Some Nozzle and TVC Hercules Inc./Magna, September
18-10703,
Injectants
Perchlorate.
Injection
United
IDC 52-30, Lockheed ' .... '_ ' _ ....
Membranes.
Bladders
G. J.; and LeCount, R. L.: Fluid Injection TVC Research Missiles and Space Co., October 1963. (CONFIDENTIAL)
181
Program.
General
Injection TVC Research (U). Report to Rocket and Nozzles Missiles and SpaCe Co., July 1963. (CONFIDENTIAL)
Grunwald, G_J.; and Anderson, _'Cotitr01 _Fests_ Re pl IDC-57-11-356,
Report.
_
114.
J.: Research Study, Strontium and Space Co., September 1963.
Test
Thrust
Vector _
Control
Effectiveness
Collected
Control.
Tests.
and Motor
source material
'i27, Anon.: PolarisB3 Fluid InjectionTVC (U). LMSC804632,LockheedMissilesand SpaceCo., October1964.(CONFIDENTIAL) "128. Anon.: Titan III Thrust Vector Control Fluid RequirementUtilizing UBS. Tech. Memo. 5141/31-68-02, Martin-Marietta Corp.(Denver, CO) January1968. "129. LeCount, Missiles 130. ..... 131.
R.
L.:
Fluid
and Space
Anon.: Weapons GM-TR-0165-00478, Anon.:
Item
(U). Figure
Injection
Co., May
Thrust
System 133B, Aerojet-General
Detailed A6658,
Second Corp.,
Specification
Thiokol
Vector
Control
No. S-133-1003-0-4,
Corp.,
Analysis
Jan.
6, 1972.
133.
Anon.: 156-5.
134.
Charwat, A. F.; Roos, J. N.; Dewey, F. C.; Flows - Part I - The Pressure Field. J. Aerospace
135.
Charwat, Flows-
F.; II-
Rep.
IDC-57-11-59,
Lockheed
(Titan
III
Wing VI Motor Data 1969. (CONFIDENTIAL).
Motor,
Solid
Book
Propellant
Model
United
Technology
Report,
Test
(U).
SR-73-AJ-I
(CONFIDENTIAL)
Anon.: TVC System December 1970.
A. Part
P-10.
Stage/Minuteman Revised March 21,
132.
156-Inch Diameter AFRPL-TR-66-109,
Test
1961.
C/D).
UTC
4404-70-330,
Motor Liquid Injection TVC Program Vol. 2, Lockheed Propulsion Co., July
Final 1966.
Center,
Results,
Motor
and Hitz, J. A.: An Investigation of Separated Sci., vol. 28, no. 6, June 1961, pp. 457-470.
Roos, J. N.; Dewey, F. C.; and Hitz, J. A.: An Investigation of Separated Flow in the Cavity and Heat Transfer. J. Aerospace Sci., vol. 28, no. 7, July 1961,
pp. 513-527. "136.
Zeamer,
R. J.:
Memorandum, 137.
138. "139.
140.
Anon.:
156-Inch
October
1965.
Anon.:
Hibex.
McQueen, Inc./ABL,
142.
Injection
Fiberglass
Rep.
Thrust
Inc./ABL,
LITVC
D2-99600-1
Vector
August
Control,
Starrett,
D.: Final
Report
Motor
Program.
(AD-371266L),
Co., October
Anon.:
Polaris
Space
Co., March
- Sprint
Fluid
1964. Injection
Missile
Distribution
of Loads
Due
to Vectoring.
1963. AFRPL-TR-65-192,
The Boeing
J. E.: Thrust Vector Control System October 1965. (CONFIDENTIAL)
and Space 141.
Fluid Hercules
Operation
Control
Study
Co., March Report
(U). Rep.
Thiokol
Chemical
Corp.,
1966.
(U). Rep.
LMSC
ZM-656-401D,
665480,
Hercules
Lockheed
Missiles
(CONFIDENTIAL) Thrust
Vector
:Control.
Rep.
LMSC
800550,
Lockheed
Missiles
and
1961.
Speisman, C.; and Kallis, 63-1942.27-28, Aerospace
J.: Preliminary Results, Corp., (San Bernadino,
Quadrant Interaction CA), June 3, 1963.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio. 182
Analytical
Unpublished.
Study
CoUeeted
Effort.
Rep.
source material
143. Hair,L. M.; andBaumgartner, A. T.: An EmpiricalPerformance Modelof Secondary Injection Thrust Vector Control (CONFIDENTIAL) "144. ! Green, August 145.
146.
C. J.i Desired 1960.
Green, C. Preliminary Walker,
R. E.; and
Rep.
Properties
J.: Effects Summary
Control. Preprint 29-31, 1964.
(U).
of the
4-64-014,
Lockheed
Injectant.
Rep.
Missiles
4511-196,
and
Space
U. S, Naval
Co., October
Ordnance
Test
Shandor,
M.: Influence
64-112,
Injection
AIAA
Properties
Propellant
Anon.: August
148.
Large, Corp.,
149.
Daniels, C. J.; et al.: Thrust VeCtor Control Requirements Rocket First Stage. NASA TM X-1906, December 1969.
150.
Lloyd, 1962.
151.
Lee, R. S. N.: Vector Control
152.
Obert,
153.
Anon.: Ullage Blowdown System Fluid Technology Center, March 11, 1971.
154.
Anon.: Solid Propellant Grain Design and Monograph, NASA SP-8076, March 1972.
155.
Anon.: Liquid Rocket Metal Tanks and Monograph, NASA SP-8088, May 1974.
156,
Anon.: Valves.
Liquid Rocket Pressure Regulator, NASA Space Vehicle Design Criteria
157.
Anon.: Criteria
Solid Rocket Motor Performance Analysis Monograph, NASA SP-8039, May 1971.
J. P.: Concepts June 1963.
and
D. K.; and Lipow,
Scaling
of Injectant
Solid
147.
Effects.
Procedures
Rep_
of Cost
M.: Reliability:
Rocket
4511-195,
Analysis.
Management,
Rep.
for Fluid
U.S.
Naval
Thrust
(Palo
Alto,
Ordnance
RM-3589-PR
for Launch
Methods
Injection
Conference
Station,
(AD
Vehicles
of Thermodynamics.
McGraw-Hill Expulsion
Internal
Tank
Book
Co. (New
Performance.
UTC
Ballistics.
Components.
York),
Station,
411554),
RAND
Prentice-Hall,
183
Inc.,
Thrust
440A-70-310,
Rev. A., United
NASA
Space
Vehicle
Design
Criteria
NASA
Space
Vehicle
Design
Criteria
Prediction.
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
Solid
1960.
Relief Valves, Check •Valves, Burst Disks, Monograph, NASA SP-8080, March 1973. and
Jan.
Test
Using a 260-Inch
and Mathematics.
Vector
CA),
A Computer Program for Conducting Parametric Studies of Liquid Injection Systems. Rep. BOAC D2-30873 (AD-812413L), The Boeing Company, 1964.
E. F.: Concepts
for 1964.
of Additives on Propellant Performance and Motor Operating Conditions. Report 1DP1210, U. S. Naval Ordnance Test Station, December 1960.
No.
Secondary 1960.
LMSC
NASA
Unpublished.
Space
Collected
and Explosive
Vehicle
Design
source material
FirstStageMotor. "158. Anon.:StructuralandThermalAnalysisFinalReport,Poseidon Data
Item
October
159. Heaton,
No. SEO25-A2A00HTJ,
Rep.
1, Hercules
Inc./Thiokol
Chemical
Corp.
Vol. III - Nozzle. (A Joint Venture),
1970. H.
(AD-510749),
S.; and
Daines,
Hercules
W. L.: Flow
Inc./Magna,
Field
September
Analysis 1970.
of Rocket
*Dossier for design criteria monograph "Solid Rocket Thrust Vector Control." available for inspection at NASA Lewis Research Center, Cleveland, Ohio.
184
Motors
(U).
AFRPL-TR-70-98
(CONFIDENTIAL)
Unpublished.
Collected
source
material
NASA SPACE VEHICLE DESIGN CRITERIA MONOGRAPHS ISSUED TO DATE
ENVIRONMENT SP-8005
Solar
SP-8010
Models
of Mars Atmosphere
SP-8011
Models
of Venus
SP-8013
Electromagnetic
Radiation,
SP-8017
Magnetic
SP-8020
Mars Surface
SP-8021
Models
SP-8023
Lunar
SP-8037
Assessment
SP-8038
Meteoroid Environment October 1970
SP-8049
The Earth's
SP-8067
Earth
SP-8069
The Planet
SP-8084
Surface Revised
SP-8085
The Planet
Mercury
SP-8091
The Planet
Saturn
SP-8092
Assessment June 1972
and
(1968),
Models,
(90
March
(1970),
to
Lunar
March
1969
km),
Revised
Surface),
to 2500
March
1973
Magnetic
(1970),
(Interplanetary
Radiation,
July
December
1971
(1971),
(Launch
March June of
Fields,
September and
1970
Planetary),
1971
Extremes
Control
Earth
1972
1969
Model-1970
and Emitted
185
(Near
of Spacecraft
Ionosphere,
Atmospheric June 1974
September
May 1969
and Control
Jupiter
Revised
May
Atmosphere
1971
1968
and Extraterrestrial,
Models
of Earth's
May
May
Model-1969
Fields-Earth
Albedo
(1967),
Atmosphere(1972),
Meteoroid Environment March 1969
Surface
Revised
1971
and
Transportation
Areas),
1972
1972
Spacecraft
Electromagnetic
Interference,
SP-8103
ThePlanets Uranus, Neptune,andPluto(1971),November 1972
SP-8105
Spacecraft ThermalControl,May1973
SP-8111
Assessment andControlof Electrostatic Charges, May1974
STRUCTURES SP-8001
BuffetingDuringAtmospheric Ascent,Revised November 1970
SP-8002
Flight-Loads Measurements DuringLaunchandExit, December 1964
SP-8003
Flutter,Buzz,andDivergence, July 1964
SP-8004
PanelFlutter,Revised June1972
SP-8006
LocalSteadyAerodynamic LoadsDuringLaunchandExit, May 1965
SP-8007
Bucklingof Thin-Walled CircularCylinders, Revised August1968
SP-8008
Prelaunch GroundWindLoads,November 1965
SP-8009
Propellant SloshLoads,August1968
SP-8012
NaturalVibrationModalAnalysis,September 1968
SP-8014
EntryThermal Protection,August1968
SP-8019
Bucklingof Thin-Walled Truncated Cones,September 1968
SP-8022
Staging Loads,February1969
SP-8029
Aerodynamic andRocket-Exhaust HeatingDuringLaunchandAscent May1969
SP-8030
Transient LoadsFromThrustExcitation,February1969
SP-8031
SloshSuppression, May1969
SP-8032
Bucklingof Thin-Walled DoublyCurvedShells,August1969
SP-8035
WindLoadsDuringAscent,June1970
SP-8040
FractureControlof MetallicPressure Vessels, May1970
SP-8042
MeteoroidDamage Assessment, May1970
186
SP-8043
Design-Development Testing,May1970
SP_044
Qualification Testing, May1970
SP-8045
Acceptance Testing,April 1970
SP-8046
LandingImpactAttenuationfor Non-Surface-Planing Landers,April 1970
SP-8050
StructuralVibrationPrediction, June1970
SP-8053
NuclearandSpace RadiationEffectsonMaterials, June1970
SP-8054
Space RadiationProtection, June1970
SP-8055
Prevention of CoupledStructure-Propulsion Instability(Pogo),October 1970
SP-8056
FlightSeparation Mechanisms, October1970
SP-8057
StructuralDesignCriteriaApplicable to a Space Shuttle,Revised March 1972
SP-8060
Compartment Venting,November 1970
SP-8061
Interactionwith Umbilicals andLaunchStand,August1970
SP-8062
EntryGasdynamic Heating,January1971
SP-8063
Lubrication,Friction,andWear,June1971
SP-8066
Deployable Aerodynamic Deceleration Systems, June1971
SP-8068
BucklingStrengthof StructuralPlates,June1971
SP-8072
AcousticLoadsGenerated by thePropulsion System, June1971
SP-8077
Transportation andHandlingLoads,September 1971
SP-8079
StructuralInteraction with ControlSystems, November 1971
SP-8082
Stress-Corrosion Cracking in Metals,August1971
SP-8083 SP-8095
" DiscontinuityStresses in MetallicPressure Vessels, November 1971 PreliminaryCriteria for the FractureControl of SpaceShuttle Structures, June1971
187
SP-8099
Combining AscentLoads,May1972
_...
SP-8104
Struc, tural InteractionWith Transportationand Hand!ingSystems, January1973
GUIDANCE ANDCONTROL SP-8015
Guidance andNavigation for EntryVehicles,November 1968 "
SP-8016
Effectsof StructuralFlexibilityon Spacecraft Control
Systems,:
April
1969
SP-8018
Spacecraft
Magnetic
SP-8024
Spacecraft
Gravitational
SP-8026
Spacecraft
Star
SP-8027
Spacecraft
Radiation
SP-8028
Entry
SP-8033
Spacecraft
Earth
SP-8034
Spacecraft
Mass Expulsion
SP-8036
Effects
Vehicle
Torques,
Torques,
Trackers,
July
Control,
May 1969
October
November
Horizon
1969
1970
Torques,
of Structural
February
March
1969
1969
Sensors,
December
Torques,
Flexibility
1969
December
1969
Launch
Vehicle
on
Control
Systems,
1970
SP-8047
Spacecraft
Sun Sensors,
SP-8058
Spacecraft
Aerodynamic
SP-8059
Spacecraft 1971
SP-8065
Tubular
SP-8070
Spaceborne
Attitude
June
Torques, Control
Spacecraft
Booms
Digital
1970 January
During
(Extendible,
Computer
Systems,
1971
Thrusting
_ Maneuvers,
Reel
Stored),
March
1971
" _:, February
February
1971
i
SP-8071
Passive
SP-8074
Spacecraft
SP-8078
Spaceborne
Gravity-Gradient Solar
Libration
Cell Arrays,
Electronic
188
May
Imaging
Dampers,
February
1971
Systems,
June
197!
1971
SP-8086
Space
Vehicle
Displays
SP-8096
Space
Vehicle
Gyroscope
SP-8098
Effects of June 1972
SP-8102
Space
CHEMICAL
Design
Structural
Vehicle
Criteria,
Sensor
1972
Applications,
Flexibility
Aceelerometer
March
on
October
Entry
Applications,
Vehicle
1972 Control
December
Systems,
1972
PROPULSION
SP-8087
Liquid
Rocket
Engine
SP-8113
Liquid 1974
Rocket
SP-8107
Turbopump
SP-8109
Liquid
Rocket
SP-8052
Liquid
Rocket
Engine
Turbopump
SP-8110
Liquid
Rocket
Engine
Turbines,
SP-8081
Liquid
Propellant
SP-8048
Liquid
Rocket
SP-8101
Liquid 1972
SP-8100
Liquid
Rocket
Engine
SP-8088
Liquid
Rocket
Metal
SP-8094
Liquid
Rocket
Valve Components,
SP-8097
Liquid
Rocket
Valve
SP-8090
Liquid
Rocket
Actuators
SP-8080
Liquid Rocket Pressure Regulators, Disks, and Explosive Valves, March
Engine
Systems
Rocket
Fluid-Cooled Combustion
for Liquid
Engine
January
Turbopump
Engine
189
Turbopump Tanks
1974 December
1973
1972 March
Shafts
Gears,
and
March
1971 Couplings,
September
1974
Components,
August
May
1974
1973
Assemblies,November and Operators,
November
May 1971
Bearings,
and Tank
1972
1974
March
Turbopump
August
Turbopumps,
Inducers,
April
Devices,
Engines,
Flow
Gas Generators,
Chambers,
Stabilization
Rocket
Centrifugal
Engine
Combustion
.1973 May 1973
Relief 1973
Valves,
Check
Valves,
Burst
SP-8064
SolidPropellant Selection andCharacterization, June1971
SP-8075
SolidPropellantProcessing Factorsin RocketMotorDesign,October 1971
SP-8076
SolidPropellant GrainDesign andInternalBallistics, March1972
SP-8073
SolidPropellant GrainStructuralIntegrityAnalysis, June1973
SP-8039
SolidRocketMotorPerformance AnalysisandPrediction,May1971
SP-8051
SolidRocketMotorIgniters,March1971
SP-8025
SolidRocketMotorMetalCases, April 1970
SP-8041
Captive-Fired Testingof SolidRocketMotors,March1971
190 *U.S.
GOVERNMENT
PRINTING
OFFICE:
1975
-
635-275/53
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