Space Exploration

Space

exploration are sometimes made, generally on cost or safety grounds. Space exploration has often been used as a proxy competition for geopolitical rivalries such as the Cold War. The early era of space exploration was driven by a "Space Race" between the Soviet Union and the United States; the launch of the first man-made object to orbit the Earth, the USSR'sSputnik 1, on October 4, 1957, and the first Moon landing by the American Apollo 11 craft on July 20, 1969 are often taken as the boundaries for this initial period. The Soviet space program achieved many of the first milestones under Sergey Korolyov and Kerim Kerimov, (From top to bottom) 

Sputnik 1, the first artificialsatellite.



Cosmonaut Yuri Gagarin, the first person in space. (Photo from www.rirt.ru.)



including the first human spaceflight (Yuri Gagarin aboard Vostok 1) in 1961, the first spacewalk (by Aleksei Leonov) in 1965, and the launch of the first space station (Salyut 1) in 1971. However, the first man-made objects to reach space were Nazi-Germany's V2 rockets, used as early as the Second World War. After the first 20 years of exploration, focus shifted from one-off flights to renewable hardware, such as

Astronaut Buzz Aldrin on the surface of the Moon.

the Space Shuttle program, and from competition to cooperation as with the International Space Station.

exploration

From the 1990s onwards, private interests began

From Wikipedia, the free encyclopedia

promoting space tourism and now private space

Space explorations is the use

exploration of the Moon (see GLXP).

of astronomy and space technology to explore outer space.[1] Physical exploration of space

In the 2000s, China initiated a successful manned

is conducted both byhuman spaceflights and

spaceflight program, while Japan and India also

by robotic spacecraft.

plan future manned space missions. Larger government programs have advocated manned

While the observation of objects in space—known

missions to the Moon and possibly Mars sometime

as astronomy—pre-dates reliable recorded history,

after 2010.

it was the development of large liquid-fueledrocket

Contents

engines during the early 20th century that allowed

[hide]

physical space exploration to become a reality. Common rationales for exploring space include advancing scientific research, uniting different

•

1 History

nations, ensuring the future survival of humanity

o

1.1 First orbital flights

and developing military/strategic advantages

o

1.2 First human flights

against other countries. Various criticisms of space

o

1.3 First planetary explorations

•

•

o

1.4 Key people in early space exploration

2 Future of space exploration o

2.1 Private ventures

3 Targets of exploration

taken from space followed the same year while the first animal experiment saw fruit flies lifted into space in 1947, both also on V2's launched by Americans and their German advisors. These suborbital experiments only allowed a very short

o

3.1 Astrobiology

o

3.2 The Sun

o

3.3 Mercury

o

3.4 Venus

The first successful orbital launch was of

o

3.5 Earth

the Soviet unmanned Sputnik (Satellite I) mission

o

3.6 Earth's Moon

o

3.7 Mars 

3.7.1 Phobos

time in space which limited their usefulness. [edit]First

orbital flights

on October 4, 1957. The satellite weighed about 83 kg (184 pounds), and is believed to have orbited Earth at a height of about 250 km (150 miles). It had two radio transmitters (20 and 40 MHz), which

o

3.8 Jupiter

o

3.9 Saturn

o

3.10 Uranus

o

3.11 Neptune

density of the ionosphere, while temperature and

o

3.12 Dwarf planets

pressure data was encoded in the duration of radio

o

emitted "beeps" that could be heard by any radio around the globe. Analysis of the radio signals was used to gather information about the electron



3.12.1 Pluto

beeps. The results indicated that the satellite was



3.12.2 Ceres

not punctured by a meteoroid. Sputnik 1 was

3.13 Asteroids

launched by an R-7 rocket. It incinerated upon re-

•

4 Rationales

entry on January 3, 1958.

•

5 Opposition

This success led to an escalation of the

•

6 Related topics

American space program, which unsuccessfully

o

6.1 Spaceflight

attempted to launch Vanguard 1 into orbit two

o

6.2 Space colonization

months later. On January 31, 1958, the U.S.

•

7 See also

successfully orbited Explorer 1 on a Juno rocket. In

•

8 References

the meantime, the Soviet dog Laika became the

•

first animal in orbit on November 3, 1957.

9 External links [edit]History

[edit]First

See also: Timeline of space exploration , Astronomy#History , and Timeline of first orbital launches by country

Yuri Gagarin was the first man in space.

The first steps into space were taken by German

The first human spaceflight was Vostok 1 (East 1),

scientists during World War II while testing the V2

carrying 27 year old Russian cosmonaut Yuri

rocket which became the first human-made object

Gagarin on April 12, 1961. The spacecraft

in space. After the war, the Allies used German

completed one orbit around the globe, lasting

scientists and their captured rockets in programs

about 1 hour and 48 minutes. Gagarin's flight

for both military and civilian research. The first

resonated around the world; it was a demonstration

scientific exploration from space was the cosmic

of the advanced Soviet space programand it

radiation experiment launched by the U.S. on a V2

opened an entirely new era in space exploration

rocket on May 10, 1946. The first images of Earth

— human spaceflight.

human flights

The U.S. first launched a person into space within a

both the Americans and Soviets as were its

month of Gagarin's flight with the

designers. The initial driving force for further

first Mercury flight, by Alan Shepard. Orbital flight

development of the technology was a weapons

was achieved by the United States when John

race for inter-continental ballistic missiles (ICBMs)

Glenn's Mercury-Atlas 6 orbited the Earth

to be used as long-range carriers for fast nuclear

on February 20, 1962.

weapon delivery, but in 1961 whenUSSR launched

Valentina Tereshkova, the first woman in space, orbited the Earth 48 times aboard Vostok 6 on June

the first man into space, the U.S. declared itself to be in a "Space Race" with Russia.

16, 1963. China first launched a person into space 42 years after the launch of Vostok 1, on October 15, 2003,

Sergei Korolev was the founder of the Soviet space program.

with the flight of Yang Liwei aboard the Shenzhou 5(Spaceboat 5) spacecraft. [edit]First



planetary explorations

Goddard, Hermann Oberth and Reinhold Tilling laid the groundwork of rocketry in the

The first successful interplanetary flyby was the

early years of the 20th century.

1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometers). Flybys for the other planets

Konstantin Tsiolkovsky, Robert



Wernher von Braun was the lead rocket engineer for Nazi Germany's World War II V-2

were first achieved in 1965 for Mars by Mariner 4,

rocket project. In the last days of the war he led

1973 for Jupiter by Pioneer 10, 1974

a caravan of workers in the German rocket

for Mercury by Mariner 10, 1979

program to the American lines, where they

for Saturn by Pioneer 11, 1986

surrendered and were brought to the USA to

for Uranus byVoyager 2, and 1989 for Neptune by

work on U.S. rocket development. He acquired

Voyager 2.

American citizenship and led the team that The first interplanetary surface mission to return at

developed and launched Explorer 1, the first

least limited surface data from another planet was

American satellite. Von Braun later led the team

the 1970 landing of Venera 7 on Venus which

at NASA's Marshall Space Flight Center which

returned data to earth for 23 minutes. In 1971 the Mars 3 mission achieved the first soft landing on Mars returning data for almost 20 seconds. Later

developed the Saturn V moon rocket. 

by Sergei Korolyov, whose legacy includes

much longer duration surface missions were

both the R7 and Soyuz—which remain in service

achieved, including over 6 years of Mars surface

to this day. Korolev was the mastermind behind

operation by Viking 1 from 1975 to 1982 and over 2

the first satellite, first man (and first woman) in

hours of transmission from the surface of Venus

orbit and first spacewalk. Until his death his

by Venera 13 in 1982 (the longest ever Soviet

identity was a closely guarded state secret; not

planetary surface mission).

people in early space exploration

Initially the race for space was often led

even his mother knew that he was responsible

[edit]Key

for creating the Russian space program. 

Kerim Kerimov was one of the founders of

The dream of stepping into the outer reaches of the

the Soviet space program and was one of the

Earth's atmosphere was driven by rocket

lead architects behind the first human

technology. The German V2 was the first rocket to

spaceflight (Vostok 1) alongside Sergey

travel into space, overcoming the problems of

Korolyov. After Korolyov's death in 1966,

thrust and material failure. During the final days

Kerimov became the lead scientist of the Soviet

of World War II this technology was obtained by

space program and was responsible for the

totaling $30 million for the first privately funded

launch of the first space stations from 1971 to

robotic lunar landing. Companies such as White

1991, including the Salyut and Mir series, and

Label Space or Astrobotics are studying mission

their precursors in 1967, the Cosmos

concepts for the purpose of entering teams. Space

186 and Cosmos 188.[2][3]

Exploration Technologies Corp also performed a successful flight of their Falcon 1 launch

Other key people included: 



Valentin Glushko held role of Chief Engine

[edit]Targets

the engines used on the early Soviet rockets,

[edit]Astrobiology

but was constantly at odds with Korolyov.

Main article: Astrobiology

Vasily Mishin, Chief Designer working under inspect the captured German V2 design. Following the death of Sergei Korolev, Mishin was held responsible for the Soviet failure to be first country to place a man on the moon.



vehicles up into space (see Virgin Galactic).

Designer for USSR. Glushko designed many of

Sergey Korolyov and one of first Soviets to



vehicle.[4] Virgin Airlines has announced taking

of exploration

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology.[5] It is focused primarily on the study of the origin, distribution andevolution of life. It is also known as exobiology (from Greek: έξω, exo,

Bob Gilruth, was the NASA head of the Space

"outside").[6][7][8] The term "Xenobiology" has been

Task Force and director of 25 manned space

used as well, but this is technically incorrect

flights. Gilruth was the person who suggested

because its terminology means "biology of the

to John F. Kennedy that the Americans take the

foreigners".[9] Astrobiologists must also consider the

bold step of reaching the Moon in an attempt to

possibility of life that is chemically entirely distinct

reclaim space superiority from the Soviets.

from any life found on earth.[10]

Christopher C. Kraft, Jr., was NASA's first flight director and oversaw development of Mission Control and associated technologies

Image of the Sun from 7 June 1992 showing some

and procedures.

sunspots

[edit]Future

of space exploration

[edit]The

Sun

While the Sun will probably not be physically explored in the close future, one of the reasons for

In the past few years, several plans for space

going into space includes knowing more about the

exploration have been announced.

Sun. Once above the atmosphere in particular and

The major paradigm today is that both government entities and the private sector have space exploration objectives. [edit]Private

ventures

the Earth's magnetic field, this gives access to the Solar wind and infrared and ultraviolet radiations that cannot reach the surface of the Earth. The Sun generates a lot of space weather which can affect power generation and transmission systems on

Dozens of private projects have been announced.

Earth and interfere with, and even damage,

Among them, Bigelow Aerospace has made two

satellites and space probes.

orbital payload deliveries and plans to build the first in-orbit hotel within the decade. TheGoogle Lunar X-Prize also promotes private space exploration by offering first and second place prizes

MESSENGER image of Mercury

A MESSENGER image from 18,000 km showing a region

provide agravitational assist en route to other

about 500 km across

celestial bodies. In 1967 Venera 4 became the first

[edit]Mercury Main article: Exploration of Mercury

probe to enter and directly examine the atmosphere of Venus. In 1970 Venera 7 became

Mercury remains the least explored of the inner

the first successful lander to reach the surface of

planets. As of January 2008, the Mariner

Venus and by 1985 it had been followed by 8

10 and MESSENGER missions have been the only

additional successful Soviet Venus landers which

missions that have made close observations of

provided images and other direct surface data.

Mercury. MESSENGER made a fly-by of Mercury

Starting in 1975 with the Soviet orbiter Venera

on 14 January 2008, to further investigate the

9 some 10 successful orbiter missions have been

observations made by Mariner 10 in 1975 (Munsell,

sent to Venus including later missions which were

2006b). A third mission to Mercury, BepiColombo, is

able map the surface of Venus using radar to pierce

to include two probes. BepiColombo is a joint

the obscuring atmosphere.

mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help

The 'marble' Earth picture taken by Apollo 17

scientists understand many of the mysteries discovered by Mariner 10's flybys. First television image of Earth from space

Flights to other planets within the Solar System are

[edit]Earth

accomplished at a cost in energy, which is

Main article: Earth observation satellite

described by the net change in velocity of the spacecraft, or delta-v. Due to the relatively high delta-v to reach Mercury and its proximity to the Sun, it is difficult to explore and orbits around it are rather unstable.

Space exploration has been used as a tool to understand the Earth as a celestial object in its own right. Orbital missions can provide data for the Earth that can be difficult or impossible to obtain from a purely ground based point of reference. For example the existence of the Van Allen

Mariner 10 image of Venus

belts was unknown until their discovery by one of the first artificial satellites. These belts contain radiation trapped by the Earth's magnetic fields,

Surface image of Venus taken by Venera 13

[edit]Venus

which currently renders construction of habitable space stations above 1000km impractical.

Main article: Observations and explorations of Venus

Following this early unexpected discovery, a large

Venus was the first target of interplanetary flyby

deployed specifically to explore the Earth from a

and lander missions and, despite one of the most

space based perspective. These satellites have

hostile surface environments in the solar system,

significantly contributed to the understanding of a

has had more landers sent to it, nearly all from the

variety of earth based phenomena. For instance,

Soviet Union, than any other planet in the solar

the hole in the ozone layer was found from an

system. The first successful Venus flyby was

artificial satellite that was exploring Earth's

the American Mariner 2 spacecraft, which flew past

atmosphere and satellites have allowed for the

Venus in 1962. Mariner 2 has been followed by

discovery of archeological sites or geological

several other flybys by multiple space agencies

formations that were difficult or impossible to

often as part of missions using a Venus flyby to

otherwise identify.

number of Earth observation satellites have been

Mars as seen by theHST The Moon as seen from the Earth Part of a panorama taken by the Spirit roverin 2004

[edit]Mars Apollo 16 astronaut John Young

[edit]Earth's

Moon

Main article: Exploration of the Moon

Main article: Exploration of Mars The exploration of Mars has been an important part of the space exploration programs of the Soviet

Earth's Moon was the first celestial object (apart

Union (later Russia), the United States, Europe,

from the Earth itself) to be the object of space

and Japan. Dozens of robotic spacecraft,

exploration. It holds the distinctions of being the

including orbiters, landers, and rovers, have been

first remote celestial object to be flown by, orbited

launched toward Marssince the 1960s. These

and landed upon by spacecraft and the only remote

missions were aimed at gathering data about

celestial object ever to be visited by humans.

current conditions and answering questions about

In 1959 the Soviets obtained the first images of

the history of Mars. The questions raised by the

the far side of the moon; something that was never

scientific community are expected to not only give

visible to humans. Starting in 1966 the Soviets

a better appreciation of the red planet but also

successfully deployed a number of landers to the

yield further insight into the past, and possible

moon which were able to obtain data directly from

future, of Earth.

the moon's surface. These unmanned Soviet

The exploration of Mars has come at a considerable

missions culminated in the Lunokhod program in

financial cost with roughly two-thirds of all

the early 70's which included the first ever

spacecraft destined for Mars failing before

unmanned rovers and also successfully returned

completing their missions, with some failing before

lunar soil samples to the earth for study. This

they even began. Such a high failure rate can be

marked the first (and to date the only) automated

attributed to the complexity and large number of

return of extraterrestrial soil samples to the Earth.

variables involved in an interplanetary journey, and

Unmanned exploration of the moon continues with

has led researchers to jokingly speak of The Great

various nations periodically deploying lunar

Galactic Ghoul[11] which subsists on a diet of Mars

orbiters.

probes. This phenomenon is also informally known

Manned exploration of the Moon began in 1968

as the Mars Curse.[12]

with the Apollo 8 mission that successfully orbited

[edit]Phobos

the Moon, the first time any object apart from the

Main article: Exploration of Phobos

Earth has been orbited by humans. In 1969 the Apollo 11 mission marked the first time humans had left the Earth to set foot upon another celestial body. Manned exploration of the Moon did not continue for long however. TheApollo 17 mission in 1972 marked the last time humans would visit the moon in any form and no mission is currently on

Russian space mission Phobos-Grunt, arriving in August-September 2010, will begin exploration of Phobos and Martian circumterrestrial orbit and study whether the moons of Mars (Phobos, at least) could be a "trans-shipment point" for spaceships travelling to Mars.[13] It will study Phobos as a target of colonization, too.[citation needed]

the drawing boards that would include any sort of human exploration of the moon sooner than the 2010's.

Voyager 1 image of Jupiter

Image of Io taken by the Galileo spacecraft

[edit]Jupiter

moon in the solar system with an atmosphere denser and thicker than that of the Earth. As a

Main article: Exploration of Jupiter

result of the deployment from the Cassini

The exploration of Jupiter has consisted solely of

spacecraft of the Huygens probe and its successful

a number of automated NASA spacecraft visiting

landing on Titan, Titan also holds the distinction of

the planet since 1973. A large majority of the

being the only moon (apart from Earth's own moon)

missions have been "flybys", in which detailed

to be successfully explored with a lander.

observations are taken without the probe landing or entering orbit; theGalileo spacecraft is only one to have orbited the planet. As Jupiter is projected to have only a relatively small rocky core and no real

Uranus from Voyager 2

solid surface, a landing mission is impossible. Reaching Jupiter from Earth requires a delta-v of 9.2 km/s,[14] which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit.[15] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required at launch to reach Jupiter, albeit at the cost of a significantly longer flight duration.[14] Jupiter has over 60 known moons, many of which have relatively little known about them.

Voyager 2 image showing the tortured surface of Miranda

[edit]Uranus Main article: Exploration of Uranus The exploration of Uranus has been solely through the Voyager 2 spacecraft, with no other visits currently planned. Given its its axial tilt of 97.77°, with its polar regions exposed to sunlight or darkness for long periods, scientists were not sure what to expect at Uranus. The closest approach to Uranus occurred on January 24, 1986. Voyager 2 studied the planet's unique atmosphere

A picture of Saturn taken by Voyager 2.

and magnetosphere.Voyager 2 also examined its ring system and the moons of Uranus including

Huygens image from the surface ofTitan

all five of the previously known moons, while

[edit]Saturn

discovering an additional 10 previously unknown

Main article: Exploration of Saturn

moons.

The exploration of Saturn has been solely

Images of Uranus proved to have a very uniform

through unmanned spacecraft launched by NASA

appearance with no evidence of the dramatic

including one mission (Cassini–Huygens) planned

storms or atmospheric banding evident on Jupiter

and executed in cooperation with other space

and Saturn. Great effort was required to even

agencies. These missions consist of flybys in 1979

identify a few clouds in the images of the planet.

by Pioneer 11, in 1980 byVoyager 1, in 1982

The magnetosphere of Uranus, however, proved to

by Voyager 2 and an orbital mission by the Cassini

be completely unique and proved to be profoundly

spacecraft which entered orbit in 2004 and is

affected by the planet's unusual axial tilt. In

expected to continue its mission well into 2010.

contrast to the bland appearance of Uranus itself

Saturn has at least 60 satellites, although the exact number is debatable since Saturn's rings are made up of vast numbers of independently orbiting

striking images were obtained of the moons of Uranus including evidence that Miranda had been unusually geologically active.

objects of varying sizes. The largest of the moons is Titan. Titan holds the distinction of being the only Picture of Neptune taken by Voyager 2

of Saturn's moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never Triton as imaged by Voyager 2

had a plausible trajectory for reaching Pluto.[19]

[edit]Neptune

Despite its reclassification, as the lead and nearest

Main article: Exploration of Neptune

member of a new and growing class of distant icy

The exploration of Neptune has begun, with the August 25, 1989 Voyager 2 flyby being the sole visit to the system. The possibility of aNeptune Orbiter was discussed, yet other than that, no other missions have been given serious thought.

bodies of intermediate size, in mass between the remaining eight planets and the small rocky objects historically termed asteroids (and also the first member of the important subclass, defined by orbit and known as "Plutinos"), Pluto continues to be of

Although the extremely uniform appearance of

great interest. After an intense political battle, a

Uranus during Voyager 2's visit in 1986 had led to

mission to Pluto dubbed New Horizons was granted

expectations that Neptune would also have few

funding from the US government in 2003.[20] New

visible atmospheric phenomena, Voyager 2 in fact

Horizons was launched successfully on January

found that Neptune had obvious banding, visible

19, 2006.

clouds, auroras and even a

In early 2007 the craft made use of a gravity

conspicuous anticyclone storm system rivaled in

assist from Jupiter. Its closest approach to Pluto will

size only by Jupiter's Great Spot. Neptune also

be on July 14, 2015; scientific observations of Pluto

proved to have the fastest winds of any planet in

will begin 5 months prior to closest approach and

the solar system, measured as high as 2,100 km/h.[16] Voyager 2 also examined Neptune's ring and moon system. It discovered 4 complete

will continue for at least a month after the encounter. [edit]Ceres

rings and additional partial ring "arcs" around

Main article: Ceres

Neptune. In addition to examining Neptune's 3 previously known moons, Voyager 2 also

Ceres is relatively ill explored at present, but in

discovered 5 previously unknown moons, one of

2015 Nasa's Dawn space probe is expected to

which, Proteus, proved to be the second largest

arrive at and enter into orbit around the dwarf

moon in the system. Data from Voyager further

planet.

reinforced the view that Neptune's largest moon, Triton, is a captured Kuiper belt object.[17] 951 Gaspra

[edit]Asteroids NASA artist's conception of Pluto

Main article: Exploration of the asteroids

[edit]Dwarf

Until the advent of space travel, objects in

planets

[edit]Pluto

the asteroid belt were merely pinpricks of light in

Main article: Exploration of Pluto

even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have

The dwarf planet Pluto (considered a planet until the IAU redefinition of "planet" in October 2006

[18]

)

now been visited by probes, the first of which

presents significant challenges for spacecraft

was Galileo, which flew past two: 951 Gaspra in

because of its great distance from Earth (requiring

1991, followed by 243 Ida in 1993. Both of these

high velocity for reasonable trip times) and small

lay near enough to Galileo's planned trajectory to

mass (making capture into orbit very difficult at

Jupiter that they could be visited at acceptable

present). Voyager 1 could have visited Pluto, but

cost. The first landing on an asteroid was

controllers opted instead for a close flyby

performed by the NEAR Shoemaker probe in 2000,

following an orbital survey of the object. The dwarf

has never achieved any major scientific

planet Ceres and the asteroid 4 Vesta, two of the

breakthroughs.[25]

three largest asteroids, are targets of NASA's Dawn

[edit]Related

mission, launched in 2007 September.

topics

[edit]Spaceflight Main article: Spaceflight

[edit]Rationales

Spaceflight is the use of space technology to fly

Main article: Space advocacy

a spacecraft into and through outer space.

The research that is conducted by national space

Spaceflight is very typically a component of space

exploration agencies, such as NASA and the RKA, is

exploration, but also supports commercial

among the reasons supporters cite to justify

activities, satellite launches.

government expenses. Some even claim that space

[edit]Space

exploration is a necessity to mankind and that

Main article: Space colonization

staying on our home planet will lead us to extinction. Some of the reasons are lack of natural resources, comets, nuclear war, worldwide epidemic etc. Stephen Hawking, renowned British theoretical physicist, said that "I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars."[21] NASA has produced a series of Public Service Announcement videos supporting the concept of space exploration.[22]

colonization

Space colonization, also called space settlement and space humanization, would be the permanent autonomous (self-sufficient) human habitation of locations outside Earth, especially of natural satellites or planets such as the Moon or Mars, using significant amounts of In-Situ Resource Utilization. To date, the longest human occupation of space was the space station Mir which was continuously inhabited for almost ten years including the record single spaceflight of Valeri Polyakovwho stayed in space for almost 438 days. Long-term stays in

Overall, the public remains largely supportive of

space reveal issues with bone and muscle loss in

both manned and unmanned space exploration.

low gravity, immune system suppression and

According to an Associated Press Poll conducted in

radiation exposure.

July 2003, 71% of U.S. citizens agreed with the statement that the space program is "a good investment", compared to 21% who did not.[23]

Many past and current concepts for the continued exploration and colonization of space focus on a return to the moon as a "stepping stone" to the

Arthur C. Clarke (1950) presented a summary of

other planets, especially Mars. At the end of 2006

motivations for the human exploration of space in

NASA announced they were planning to build a

his non-fiction semi-technical

permanent moon base with continual presence by

monograph Interplanetary Flight.

[24]

In it he argued

that humanity's choice is essentially between expansion off the Earth into space, versus cultural (and eventually biological) stagnation and death. [edit]Opposition Critics, such as the late physicist and Nobel prize winner Richard Feynman have contended that human space travel (as opposed to space exploration in general, such as robotic missions)

2024.[26]