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The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons. Major missions included launching numerous satellites and interplanetary probes, conducting space science experiments, and the servicing and construction of space stations. A major international contribution was the Spacelab payload suite, from the ESA.

The Space Shuttle was a partially reusable launch system and orbital spacecraft operated by the U.S. National Aeronautics and Space Administration (NASA) for human spaceflight missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons. The first of four orbital test flights occurred in 1981 leading to operational flights beginning in 1982, all launched from the Kennedy Space Center, Florida. The system was retired from service in 2011 after 135 missions; on July 8, 2011, with Space Shuttle Atlantis performing that 135th launch - the final launch of the three-decade shuttle program. The program ended after Atlantis landed at the Kennedy Space Center on July 21, 2011. Major missions included launching numerous satellites and interplanetary probes, conducting space science experiments, and servicing and construction of space stations. Enterprise was a prototype orbiter used for atmospheric testing during development in the 1970s and lacked engines and heat shield. Five space-worthy orbiters were built—two were destroyed in accidents and the others have been retired.

It was used for orbital space missions by NASA, the U.S. Department of Defense, the European Space Agency, Japan, and Germany. The United States funded Space Transportation System (STS) development and shuttle operations except for Spacelab D1 and D2 — sponsored by West Germany and reunified Germany respectively. In addition, SL-J was partially funded by Japan.

At launch, it consisted of the "stack", including a dark orange-colored external tank (ET); two white, slender Solid Rocket Boosters (SRBs); and the Orbiter Vehicle (OV), which contained the crew and payload. Some payloads were launched into higher orbits with either of two different booster stages developed for the STS (single-stage Payload Assist Module or two-stage Inertial Upper Stage). The Space Shuttle was stacked in the Vehicle Assembly Building and the stack mounted on a mobile launch platform held down by four explosive bolts on each SRB which are detonated at launch.

The shuttle stack launched vertically like a conventional rocket. It lifted off under the power of its two SRBs and three main engines, which were fueled by liquid hydrogen and liquid oxygen from the external tank. The Space Shuttle had a two-stage ascent. The SRBs provided additional thrust during liftoff and first-stage flight. About two minutes after liftoff, explosive bolts were fired, releasing the SRBs, which then parachuted into the ocean, to be retrieved by ships for refurbishment and reuse. The shuttle orbiter and external tank continued to ascend on an increasingly horizontal flight path under power from its main engines. Upon reaching 17,500 mph (7.8 km/s), necessary for low Earth orbit, the main engines are shut down. The external tank was then jettisoned to burn up in the atmosphere. After jettisoning the external tank, the orbital manoeuvring system (OMS) engines were used to adjust the orbit.

The orbiter carried people and payload such as satellites or space station parts into low Earth orbit, into the Earth's upper atmosphere or thermosphere. Usually, five to seven crew members rode in the orbiter. Two crew members, the commander and pilot, were sufficient for a minimal flight, as in the first four "test" flights, STS-1 through STS-4. The typical payload capacity was about 22,700 kilogrammes (50,000 lb) but could be increased depending on the choice of the launch configuration. The orbiter carried its payload in a large cargo bay with doors that opened along the length of its top, a feature which made the Space Shuttle unique among spacecraft. This feature made possible the deployment of large satellites such as the Hubble Space Telescope, and also the capture and return of large payloads back to Earth.

When the orbiter's space mission was complete, it fired its OMS thrusters to drop out of orbit and re-enter the lower atmosphere. During the descent, the orbiter passed through different layers of the atmosphere and decelerates from hypersonic speed primarily by aerobraking. In the lower atmosphere and landing phase, it was more like a glider but with reaction control system (RCS) thrusters and fly-by wire-controlled hydraulically-actuated flight surfaces controlling its descent. It landed on a long runway as a spaceplane. The aerodynamic shape was a compromise between the demands of radically different speeds and air pressures during re-entry, hypersonic flight, and subsonic atmospheric flight. As a result, the orbiter had a relatively high sink rate at low altitudes, and it transitioned during re-entry from using RCS thrusters at very high altitudes to flight surfaces in the lower atmosphere.

Early history

President Nixon (right) with NASA Administrator Fletcher in January 1972, three months before Congress approved funding for the shuttle program

The formal design of what became the Space Shuttle began with "Phase A" contract design studies issued in the late 1960s. However, conceptualization began two decades earlier, before the Apollo program of the 1960s. One of the places the concept of a spacecraft returning from space to a horizontal landing originated was within NACA, in 1954, in the form of an aeronautics research experiment, later named the X-15. The NACA proposal was submitted by Walter Dornberger.

In 1958, the X-15 concept further developed into a proposal to launch an X-15 into space, and another X-series spaceplane proposal called the X-20, which was not constructed, as well as a variety of aerospace plane concepts and studies. Neil Armstrong was selected to pilot both the X-15 and the X-20. Though the X-20 was not built, another spaceplane similar to the X-20 was built several years later and delivered to NASA in January 1966 called the HL-10 ("HL" indicated "horizontal landing").

In the mid-1960s, the US Air Force conducted a series of classified studies on next-generation space transportation systems and concluded that semi-reusable designs were the cheapest choice. It proposed a development program with an immediate start on a "Class I" vehicle with expendable boosters, followed by the slower development of a "Class II" semi-reusable design and perhaps a "Class III" fully reusable design later. In 1967, George Mueller held a one-day symposium at NASA headquarters to study the options. Eighty people attended and presented a wide variety of designs, including earlier Air Force designs as the Dyna-Soar (X-20).

In 1968, NASA officially began work on what was then known as the Integrated Launch and Re-entry Vehicle (ILRV). At the same time, NASA held a separate Space Shuttle Main Engine (SSME) competition. NASA offices in Houston and Huntsville jointly issued a Request for Proposal (RFP) for ILRV studies to design a spacecraft that could deliver a payload to orbit but also re-enter the atmosphere and fly back to Earth. For example, one of the responses was for a two-stage design, featuring a large booster and a small orbiter, called the DC-3, one of the several Phase A shuttle designs. After the aforementioned "Phase A" studies, B, C, and D phases progressively evaluated in-depth designs up to 1972. In the final design, the bottom stage was recoverable solid rocket boosters, and the top stage used an expendable external tank.

In 1969, President Richard Nixon decided to support proceeding with Space Shuttle development. A series of development programs and analysis refined the basic design, prior to full development and testing. In August 1973, the X-24B proved that an unpowered spaceplane could re-enter Earth's atmosphere for a horizontal landing.

Across the Atlantic, European ministers met in Belgium in 1973 to authorise Western Europe's manned orbital project and its main contribution to Space Shuttle — the Spacelab program. Spacelab would provide a multi-disciplinary orbital space laboratory and additional space equipment for the Shuttle.

Description

STS-1 on the launch pad, 1981

The Space Shuttle was the first operational orbital spacecraft designed for reuse. It carried different payloads to low Earth orbit, provided crew rotation for the International Space Station (ISS) and performed servicing missions. The orbiter could also recover satellites and other payloads from orbit and return them to Earth. Each Shuttle was designed for a projected lifespan of 100 launches or ten years of operational life, although this was later extended. The person in charge of designing the STS was Maxime Faget, who had also overseen the Mercury, Gemini, and Apollo spacecraft designs. The crucial factor in the size and shape of the Shuttle Orbiter was the requirement that it be able to accommodate the largest planned commercial and military satellites, and have the cross-range recovery range to meet the requirement for classified USAF missions for a once-around abort from a launch to a polar orbit. Factors involved in opting for solid rockets and an expendable fuel tank included the desire of the Pentagon to obtain a high-capacity payload vehicle for satellite deployment, and the desire of the Nixon administration to reduce the costs of space exploration by developing a spacecraft with reusable components.

Each Space Shuttle is a reusable launch system that is composed of three main assemblies: the reusable Orbiter Vehicle (OV), the expendable external tank (ET), and the two reusable solid rocket boosters(SRBs). Only the orbiter entered orbit shortly after the tank and boosters are jettisoned. The vehicle was launched vertically like a conventional rocket, and the orbiter glided to a horizontal landing like an aeroplane, after which it was refurbished for reuse. The SRBs parachuted to splashdown in the ocean where they were towed back to shore and refurbished for later shuttle missions.

 
Discovery rockets into orbit, seen here just after booster (SRB) separation

Five space-worthy orbiters were built: Columbia (OV-102), Challenger (OV-099), Discovery (OV-103), Atlantis (OV-104), and Endeavour (OV-105). An additional craft, Enterprise (OV-101), was not built for orbital space flight and was used only for testing gliding and landing. Enterprise was originally intended to be made fully space-worthy after use for the approach and landing test (ALT) program, but it was found more economical to upgrade the structural test article STA-099 into orbiter Challenger (OV-099). Challenger disintegrated 73 seconds after launch in 1986, and Endeavour was built as a replacement for Challenger from structural spare components. Columbia broke apart during re-entry in 2003. Building Space Shuttle Endeavour cost about US$1.7 billion. One Space Shuttle launch costs around $450 million.

Roger A. Pielke, Jr. has estimated that the Space Shuttle program has cost about US$170 billion (2008 dollars) through early 2008. This works out to an average cost per flight of about US$1.5 billion. However, two missions were paid for by Germany, Spacelab D1 and D2 (D for Deutschland) with a payload control centre in Oberpfaffenhofen, Germany. D1 was the first time that control of a manned STS mission payload was not in U.S. hands.

At times, the orbiter itself was referred to as the Space Shuttle. Technically, this was a slight misnomer, as the actual "Space Transportation System" (Space Shuttle) was the combination of the orbiter, the external tank, and the two solid rocket boosters. Combined, these were referred to as the "stack"; the components were assembled in the Vehicle Assembly Building, originally built to assemble the Apollo Saturn V rocket.

Responsibility for the shuttle components was spread among multiple NASA field centres. The Kennedy Space Center was responsible for launch, landing and turnaround operations for equatorial orbits (the only orbit profile actually used in the program), the US Air Force at the Vandenberg Air Force Base was responsible for launch, landing and turnaround operations for polar orbits (though this was never used), theJohnson Space Center served as the central point for all shuttle operations, the Marshall Space Flight Center was responsible for the main engines, external tank, and solid rocket boosters, the John C. Stennis Space Center handled main engine testing, and the Goddard Space Flight Center managed the global tracking network.

Orbiter vehicle

 
Atlantis deploys the landing gear before landing on a selected runway just like a common aircraft.

The orbiter resembles a conventional aircraft, with double-delta wings, swept 81° at the inner leading edge and 45° at the outer leading edge. Its vertical stabiliser's leading edge is swept back at a 50° angle. The four elevons mounted at the trailing edge of the wings, and the rudder/speed brake, attached at the trailing edge of the stabiliser, with the body flap, controlled the orbiter during descent and landing.

The orbiter's payload bay measures 15 by 60 feet (4.6 by 18 m), comprising most of the fuselage. Information declassified in 2011 showed that the payload bay was designed specifically to accommodate the KH-9 HEXAGON spy satellite operated by the National Reconnaissance Office. Two mostly symmetrical lengthwise payload bay doors hinged on either side of the bay comprise its entire top. Payloads are generally loaded horizontally into the bay while the orbiter is oriented vertically on the launch pad and unloaded vertically in the near-weightless orbital environment by the orbiter's robotic remote manipulator arm (under astronaut control), EVA astronauts, or under the payloads' own power (as for satellites attached to a rocket "upper stage" for deployment.)

Three Space Shuttle main engines (SSMEs) are mounted on the orbiter's aft fuselage in a triangular pattern. The engine nozzles can swivel 10.5 degrees up and down, and 8.5 degrees from side to side during ascent to change the direction of their thrust to steer the shuttle. The orbiter structure is made primarily from aluminium alloy, although the engine structure is made primarily from titanium alloy.

The space-capable orbiters built were OV-102 Columbia, OV-099 Challenger, OV-103 Discovery, OV-104 Atlantis, and OV-105 Endeavour.

1950s

Sputnik 1 – First Earth orbiter
Luna 2 – First lunar impact

1957

  • Soviet Union Sputnik 1 – 4 October 1957 – First Earth orbiter
  • Soviet Union Sputnik 2 – 3 November 1957 – Earth orbiter, first animal in orbit, a dog named Laika

1958

  • United States Explorer 1 – 1 February 1958 – Earth orbiter; first American orbiter, discovered Van Allen radiation belts
  • United States Vanguard 1 – 17 March 1958 – Earth orbiter

1959

  • Soviet Union Luna 1 – 2 January 1959 – First lunar flyby (attempted lunar impact?)
  • United States Pioneer 4 – 3 March 1959 – Lunar flyby
  • Soviet Union Luna 2 – 12 September 1959 – First lunar impact
  • Soviet Union Luna 3 – 4 October 1959 – Lunar flyby; First images of far side of Moon

1960s

Vostok 1 – First manned Earth orbiter
Mariner 2 – First Venus flyby
Luna 9 – First lunar lander
Venera 4 – First Venus atmospheric probe
Zone 5 – First lunar flyby and return to Earth
Apollo 8 – First manned lunar orbiter
Apollo 11 – First manned lunar landing

1960

  • United States Pioneer 5 – 11 March 1960 – Interplanetary space investigations

1961

  • Soviet Union Sputnik 7 – 4 February 1961 – Attempted Venus impact (failed to escape Earth orbit)
  • Soviet Union Venera 1 – 12 February 1961 – Venus flyby (contact lost)
  • Soviet Union Vostok 1 – 12 April 1961 – First manned Earth orbiter
  • United States Mercury-Redstone 3 – 5 May 1961 – First American in space
  • United States Ranger 1 – 23 August 1961 – Attempted lunar test flight
  • United States Ranger 2 – 18 November 1961 – Attempted lunar test flight

1962

  • United States Ranger 3 – 26 January 1962 – Attempted lunar impact (missed Moon)
  • United States Mercury-Atlas 6 – 20 February 1962 – First American manned Earth orbiter
  • United States Ranger 4 – 23 April 1962 – Lunar impact (but unintentionally hit lunar farside and returned no data)
  • Soviet Union Sputnik 19 – 25 August 1962 – Attempted Venus lander (failed to escape Earth orbit)
  • United States Mariner 2 – 27 August 1962 – First successful planetary encounterFirst successful Venus flyby
  • Soviet Union Sputnik 20 – 1 September 1962 – Attempted Venus lander (failed to escape Earth orbit)
  • Soviet Union Sputnik 21 – 12 September 1962 – Attempted Venus flyby (exploded)
  • United States Ranger 5 – 18 October 1962 – Attempted lunar impact (missed Moon)
  • Soviet Union Sputnik 22 – 24 October 1962 – Attempted Mars flyby (exploded)
  • Soviet Union Mars 1 – 1 November 1962 – Mars flyby (contact lost)
  • Soviet Union Sputnik 24 – 4 November 1962 – Attempted Mars lander (broke up)

1963

  • Soviet Union Sputnik 25 – 4 January 1963 – Attempted lunar lander (failed to escape Earth orbit)
  • Soviet Union Luna 4 – 2 April 1963 – Attempted lunar lander (missed Moon)
  • Soviet Union Cosmos 21 – 11 November 1963 – Attempted Venera test flight?

1964

  • United States Ranger 6 – 30 January 1964 – Lunar impact (cameras failed)
  • Soviet Union Cosmos 27 – 27 March 1964 – Attempted Venus flyby (failed to escape Earth orbit)
  • Soviet Union Zond 1 – 2 April 1964 – Venus flyby (contact lost)
  • United States Ranger 7 – 28 July 1964 – Lunar impact
  • United States Mariner 3 – 5 November 1964 – Attempted Mars flyby (failed to attain correct trajectory)
  • United States Mariner 4 – 28 November 1964 – First Mars flyby
  • Soviet Union Zond 2 – 30 November 1964 – Mars flyby (contact lost)

1965

  • United States Ranger 8 – 17 February 1965 – Lunar impact
  • Soviet Union Cosmos 60 – 12 March 1965 – Attempted lunar lander (failed to escape Earth orbit)
  • United States Ranger 9 – 21 March 1965 – Lunar impact
  • Soviet Union Luna 5 – 9 May 1965 – Lunar impact (attempted soft landing)
  • Soviet Union Luna 6 – 8 June 1965 – Attempted lunar lander (missed Moon)
  • Soviet Union Zond 3 – 18 July 1965 – Lunar flyby
  • Soviet Union Luna 7 – 4 October 1965 – Lunar impact (attempted soft landing)
  • Soviet Union Venera 2 – 12 November 1965 – Venus flyby (contact lost)
  • Soviet Union Venera 3 – 16 November 1965 – Venus lander (contact lost) – the First spacecraft to reach another planet's surfaceFirst Venus impact
  • Soviet Union Cosmos 96 – 23 November 1965 – Attempted Venus lander (stayed in Earth orbit due to launch failure)
  • Soviet Union Luna 8 – 3 December 1965 – Lunar impact (attempted the soft landing?)
  • United States Pioneer 6 – 16 December 1965 – "Space weather" observations

1966

  • Soviet Union Luna 9 – 31 January 1966 – First lunar lander
  • Soviet Union Cosmos 111 – 1 March 1966 – Attempted lunar orbiter? (failed to escape Earth orbit)
  • Soviet Union Luna 10 – 31 March 1966 – First lunar orbiter
  • United States Surveyor 1 – 30 May 1966 – Lunar lander
  • United States Explorer 33 – 1 July 1966 – Attempted lunar orbiter (failed to attain lunar orbit)
  • United States Lunar Orbiter 1 – 10 August 1966 – Lunar orbiter
  • United States Pioneer 7 – 17 August 1966 – "Space weather" observations
  • Soviet Union Luna 11 – 24 August 1966 – Lunar orbiter
  • United States Surveyor 2 – 20 September 1966 – Attempted lunar lander (crashed into Moon)
  • Soviet Union Luna 12 – 22 October 1966 – Lunar orbiter
  • United States Lunar Orbiter 2 – 6 November 1966 – Lunar orbiter
  • Soviet Union Luna 13 – 21 December 1966 – Lunar lander

1967

  • United States Lunar Orbiter 3 – 4 February 1967 – Lunar orbiter
  • United States Surveyor 3 – 17 April 1967 – Lunar lander
  • United States Lunar Orbiter 4 – 8 May 1967 – Lunar orbiter
  • Soviet Union Venera 4 – 12 June 1967 – First Venus atmospheric probe
  • United States Mariner 5 – 14 June 1967 – Venus flyby
  • Soviet Union Cosmos 167 – 17 June 1967 – Attempted Venus probe (failed to escape Earth orbit)
  • United States Surveyor 4 – 14 July 1967 – Attempted lunar lander (crashed into Moon)
  • United States Explorer 35 (IMP-E) – 19 July 1967 – Lunar orbiter
  • United States Lunar Orbiter 5 – 1 August 1967 – Lunar orbiter
  • United States Surveyor 5 – 8 September 1967 – Lunar lander
  • United States Surveyor 6 – 7 November 1967 – Lunar lander
  • United States Pioneer 8 – 13 December 1967 – "Space weather" observations

1968

  • United States Surveyor 7 – 7 January 1968 – Lunar lander
  • Soviet Union Zond 4 – 2 March 1968 – Lunar programme test flight
  • Soviet Union Luna 14 – 7 April 1968 – Lunar orbiter
  • Soviet Union Zond 5 – 15 September 1968 – First lunar flyby and return to Earth
  • United States Pioneer 9 – 8 November 1968 – "Space weather" observations
  • Soviet Union Zond 6 – 10 November 1968 – Lunar flyby and return to Earth
  • United States Apollo 8 – 21 December 1968 – First manned lunar orbiter

1969

  • Soviet Union Venera 5 – 5 January 1969 – Venus atmospheric probe
  • Soviet Union Venera 6 – 10 January 1969 – Venus atmospheric probe
  • United States Mariner 6 – 25 February 1969 – Mars flyby
  • United States Apollo 9 – 3 March 1969 – Manned lunar lander (LEM) flight test
  • United States Mariner 7 – 27 March 1969 – Mars flyby
  • United States Apollo 10 – 18 May 1969 – Manned lunar orbiter
  • Soviet Union Luna 15 – 13 July 1969 – Lunar orbiter (attempted lunar lander?)
  • United States Apollo 11 – 16 July 1969 – First manned lunar landing
  • Soviet Union Zond 7 – 7 August 1969 – Lunar flyby and return to Earth
  • Soviet Union Cosmos 300 – 23 September 1969 – Attempted lunar sample return? (failed to escape Earth orbit)
  • Soviet UnionCosmos 305 – 22 October 1969 – Attempted lunar sample return? (failed to escape Earth orbit)
  • United States Apollo 12 – 14 November 1969 – Manned lunar landing

1970s

220px-Venera 11 lander
Venera 7 – First Venus lander
Mars 3 – First Mars lander
Pioneer 10 – First Jupiter flyby
Mariner 10 – First Mercury flyby
Voyager 2 – First Uranus/first Neptune flyby

1970

  • United States Apollo 13 – 11 April 1970 – Manned lunar flyby and return to Earth (manned lunar landing aborted)
  • Soviet Union Venera 7 – 17 August 1970 – First Venus lander
  • Soviet Union Cosmos 359 – 22 August 1970 – Attempted Venus probe (failed to escape Earth orbit)
  • Soviet Union Luna 16 – 12 September 1970 – First robotic lunar sample return
  • Soviet Union Zond 8 – 20 October 1970 – Lunar flyby and return to Earth
  • Soviet Union Luna 17/Lunokhod 1 – 10 November 1970 – First lunar rover

1971

  • United States Apollo 14 – 31 January 1971 – Manned lunar landing
  • Soviet Union Salyut 1 – 19 April 1971 – First space station
  • Soviet Union Cosmos 419 – 10 May 1971 – Attempted Mars orbiter (failed to escape Earth orbit)
  • United States Mariner 9 – 30 May 1971 – First Mars orbiter
  • Soviet Union Mars 2 – 19 May 1971 – Mars orbiter and attempted lander; First Mars impact
  • Soviet Union Mars 3 – 28 May 1971 – Mars orbiter, First Mars lander (lost contact after 14.5s) and First Mars atmospheric probe
  • United States Apollo 15 – 26 July 1971 – Manned lunar landing; First manned lunar rover
  • Soviet Union Luna 18 – 2 September 1971 – Attempted lunar sample return (crashed into Moon)
  • Soviet Union Luna 19 – 28 September 1971 – Lunar orbiter

1972

  • Soviet Union Luna 20 – 14 February 1972 – Lunar robotic sample return
  • United States Pioneer 10 – 3 March 1972 – First Jupiter flyby
  • Soviet Union Venera 8 – 27 March 1972 – Venus lander
  • Soviet Union Cosmos 482 – 31 March 1972 – Attempted Venus probe (failed to escape Earth orbit)
  • United States Apollo 16 – 16 April 1972 – Manned lunar landing
  • United States Apollo 17 – 7 December 1972 – Last manned lunar landing

1973

  • Soviet Union Luna 21/Lunokhod 2 – 8 January 1973 – Lunar rover
  • United States Pioneer 11 – 5 April 1973 – Jupiter flyby and First Saturn flyby
  • United States Skylab – 14 May 1973 – First American space station
  • United States Explorer 49 (RAE-B) – 10 June 1973 – Lunar orbiter/radio astronomy
  • Soviet Union Mars 4 – 21 July 1973 – Mars flyby (attempted Mars orbiter)
  • Soviet Union Mars 5 – 25 July 1973 – Mars orbiter
  • Soviet Union Mars 6 – 5 August 1973 – Mars flyby and attempted lander (contact lost)
  • Soviet Union Mars 7 – 9 August 1973 – Mars flyby and attempted lander (missed Mars)
  • United States Mariner 10 – 4 November 1973 – Venus flyby and First Mercury flyby

1974

  • Soviet Union Luna 22 – 2 June 1974 – Lunar orbiter
  • Soviet Union Luna 23 – 28 October 1974 – Attempted lunar sample return (failed due to damage on lunar landing)
  • United States Germany Helios-A – 10 December 1974 – Solar observations

1975

  • Soviet Union Venera 9 – 8 June 1975 – First Venus orbiter and lander; First images from surface of Venus
  • Soviet Union Venera 10 – 14 June 1975 – Venus orbiter and lander
  • United States Viking 1 – 20 August 1975 – Mars orbiter and lander; First lander returning data and First pictures from Martian surface
  • United States Viking 2 – 9 September 1975 – Mars orbiter and lander

1976

  • United States Germany Helios-B – 15 January 1976 – Solar observations, Closest solar approach (0.29 AU)
  • Soviet Union Luna 24 – 9 August 1976 – Lunar robotic sample return

1977

  • United States Voyager 2 – 20 August 1977 – Jupiter/Saturn/first Uranus/first Neptune flyby
  • United States Voyager 1 – 5 September 1977 – Jupiter/Saturn flyby, Furthest human-made object – currently (2011) over 117 AU

1978

  • United States Pioneer Venus 1 – 20 May 1978 – Venus orbiter
  • United States Pioneer Venus 2 – 8 August 1978 – Venus atmospheric probes
  • United States European Union ISEE-3 – 12 August 1978 – Solar wind investigations; later redesignated International Cometary Explorer and performed Comet Giacobini-Zinner and Comet Halley flybys – First comet flyby
  • Soviet Union Venera 11 – 9 September 1978 – Venus flyby and lander
  • Soviet Union Venera 12 – 14 September 1978 – Venus flyby and lander

1980s

Giotto – Comet Halley flyby

1981

  • Soviet Union Venera 13 – 30 October 1981 – Venus flyby and lander
  • Soviet Union Venera 14 – 4 November 1981 – Venus flyby and lander

1983

  • Soviet Union Venera 15 – 2 June 1983 – Venus orbiter
  • Soviet Union Venera 16 – 7 June 1983 – Venus orbiter

1984

  • Soviet Union Vega 1 – 15 December 1984 – Venus flyby, lander and balloon; continued on to Comet Halley flyby
  • Soviet Union Vega 2 – 21 December 1984 – Venus flyby, lander and balloon; continued on to Comet Halley flyby

1985

Galileo
  • Japan Sakigake – 7 January 1985 – Comet Halley flyby
  • European Union Giotto – 2 July 1985 – Comet Halley flyby
  • Japan Suisei (Planet-A) – 18 August 1985 – Comet Halley flyby

1988

  • Soviet Union Phobos 1 – 7 July 1988 – Attempted Mars orbiter/Phobos landers (contact lost)
  • Soviet Union Phobos 2 – 12 July 1988 – Mars orbiter/attempted Phobos landers (contact lost)

1989

  • United States Magellan – 4 May 1989 – Venus orbiter
  • United States Galileo – 18 October 1989 – Venus flyby, first Asteroid flyby, first Asteroid moon discovery, first Jupiter orbiter/atmospheric probe

1990s

1990

Mars Pathfinder – Mars lander and first Mars rover
  • Japan Hiten (Muses-A) – 24 January 1990 – Lunar flyby and orbiter
  • United States European Union Hubble Space Telescope – Orbital space telescope
  • United States European Union Ulysses – 6 October 1990 – Solar polar orbiter

1991

  • Japan United States United Kingdom Yohkoh (Solar-A) – 30 August 1991 – Solar observations

1992

  • United States Mars Observer – 25 September 1992 – Attempted Mars orbiter (contact lost)

1994

  • United States Clementine – 25 January 1994 – Lunar orbiter/attempted asteroid flyby
  • United States WIND – 1 November 1994 – Solar wind observations

1995

  • European Union United States SOHO – 2 December 1995 – Solar observatory

1996

  • United States NEAR Shoemaker – 17 February 1996 – Eros orbiter, first near-Earth asteroid flybyfirst asteroid orbit and first asteroid landing
  • United States Mars Global Surveyor – 7 November 1996 – Mars orbiter
  • Russia Mars 96 – 16 November 1996 – Attempted Mars orbiter/landers (failed to escape Earth orbit)
  • United States Mars Pathfinder – 4 December 1996 – Mars lander and first planetary rover

1997

Cassini–Huygens – First Saturn orbiter and first Titan lander
  • United States ACE – 25 August 1997 – Solar wind and "space weather" observations
  • United States European Union Cassini–Huygens – 15 October 1997 – First Saturn orbiter and first outer planet lander
  • China AsiaSat 3/HGS-1 – 24 December 1997 – Lunar flyby

1998

  • United States Lunar Prospector – 7 January 1998 – Lunar orbiter
  • Japan Nozomi (probe) (also known as Planet-B) – 3 July 1998 – Attempted Mars orbiter (failed to enter Mars orbit)
  • United States Deep Space 1 (DS1) – 24 October 1998 – Asteroid and comet flyby
  • United States Russia European Union Japan Canada – 20 November 1998 – International Space Station
  • United States Mars Climate Orbiter – 11 December 1998 – Attempted Mars orbiter (orbit insertion failed)

1999

  • United States Mars Polar Lander/Deep Space 2 (DS2) – 3 January 1999 – Attempted Mars lander/penetrators (contact lost)
  • United States Stardust – 7 February 1999 – First comet coma sample return – returned January 15, 2006

2000s

Mars Express/Beagle 2 – First planetary mission by the ESA
 

2001

  • United States 2001 Mars Odyssey – 7 April 2001 – Mars orbiter
  • United States Genesis – 8 August 2001 – First solar wind sample return

2002

  • United States CONTOUR – 3 July 2002 – Attempted flyby of three comet nuclei (lost in space)

2003

  • Japan Hayabusa (Muses-C) – 9 May 2003 – Asteroid lander and First sample return from asteroid
  • United States Mars Exploration Rovers – 10 June/7 July 2003 – Two Mars rovers ("Spirit" and "Opportunity")
  • European Union Mars Express/Beagle 2 – 1 June 2003 – Mars orbiter/lander (lander failure)
  • European Union Sweden SMART-1 – 27 September 2003 – Lunar orbiter
  • China Shenzhou 5 – 15 October 2003 – China's first manned Earth orbiter

2004

  • European Union Rosetta – 2 March 2004 – Comet orbiter and lander (expected arrival 2014)
  • United States MESSENGER – 3 August 2004 – First Mercury orbiter (achieved orbit 18 March 2011)

2005

  • United States Deep Impact – 12 January 2005 – First comet impact
  • United States Mars Reconnaissance Orbiter – 12 August 2005 – Mars orbiter
  • European Union Venus Express – 9 November 2005 – Venus polar orbiter

2006

  • United States New Horizons – 19 January 2006 – First Pluto/Charon and Kuiper Belt flyby (expected arrival 14 July 2015)
  • Japan United States United Kingdom Hinode (Solar-B) – 22 September 2006 – Solar orbiter
  • United States STEREO – 26 October 2006 – Two spacecraft, solar orbiters

2007

  • United States Phoenix – 4 August 2007 – Mars polar lander
  • Japan Kaguya (Selene) – 14 September 2007 – Lunar orbiters
  • United States Dawn – 27 September 2007 – Asteroid Ceres and Vesta orbiter (entered orbit around Vesta on 16 July 2011)
  • China Change 1 – 24 October 2007 – Lunar orbiter

2008

  • China Shenzhou 7 – 25 September 2008 – China's first spacewalk
  • India Chandrayaan-1 – 22 October 2008 – Lunar orbiter and impactor – Discovered water on the moon

2009

  • United States Lunar Reconnaissance Orbiter/LCROSS – 18 June 2009 – Lunar polar orbiter and lunar impactor

[edit]the 2010s

2010

  • United States Solar Dynamics Observatory – 11 February 2010 – Continuous solar monitoring
  • Japan Akatsuki (Planet-C) – 20 May 2010 – Venus orbiter (orbit insertion failed in 2010 / postponed to 2016–17)
  • France PICARD – 15 June 2010 – Solar orbiter
  • China Change 2 – 1 October 2010 – Lunar orbiter

2011

  • United States Juno – 5 August 2011 – Jupiter orbiter
  • United States GRAIL – 10 September 2011 – Two spacecraft, Lunar orbiters

[edit]Planned or scheduled

2011

  • China Tiangong 1 – September 2011 – First Chinese orbital laboratory
  • United States Mars Science Laboratory Curiosity Rover – November/December 2011 (scheduled) – Mars Rover
  • Russia China Phobos-Grunt and Yinghuo-1 – November 2011 – Phobos orbiter, lander and sample return (Russia), Mars orbiter (China)

2012

  • India Aditya – Solar observations
  • India Astros – Space observatory

2013

  • United States LADEE – 15 January 2013 (scheduled) – Lunar orbiter
  • United States MAVEN – November/December 2013 – Mars orbiter
  • China Change 3 – Lunar rover
  • European Union Don Quijote – 2013 or 2015 – Asteroid orbiter, impactor

2014

  • European Union Japan BepiColombo – July–August 2014 – Mercury orbiters
  • Japan Hayabusa 2 – July 2014 – Asteroid lander and sample return
  • India Russia Chandrayaan-2 and Luna-Glob 2 – Lunar orbiter (India), lander & rover (Russia)[1]
  • Russia Luna-Grunt 1 – Lunar orbiter, lander and rover

2015

  • Russia Luna-Glob 1 – Lunar orbiter, lander and penetrators
  • Russia Luna-Grunt 2 – Lunar lander and sample return
  • Japan SELENE-2 – <2015 – Lunar lander and penetrator

2016

  • European Union United States ExoMars – Mars orbiter and lander
  • United States OSIRIS-REx – Asteroid sample return mission[2]
  • Russia Venera-D – Venus orbiter
  • India ISRO Orbital Vehicle – First Indian manned orbiter[3]

2017

  • European Union SOLO – January 2017 – Solar Orbiter
  • China Change 4 – Robotic lunar sample return mission[citation needed]

2018

  • United States Solar Probe Plus – July 30, 2018 – Solar Orbiter, Closest solar approach (0.04 AU)
  • European Union ExoMars – Mars Rover
  • European Union MoonNext – Lunar Lander
  • United States International Lunar Network – Lunar lander

2020

  • European Union MarcoPolo-R – Asteroid sample return mission
  • India Manned landing on Moon[4]
  • United States European Union Mars sample return mission
  • European Union Jupiter Icy Moon Explorer – Mission to explore Jupiter and its icy moons.
  • China Tiangong (Project 921-2) – First Chinese space station[3]
  • Russia Lunny Poligon – Russian robotic lunar base
  • United States European Union Titan Saturn System Mission – after 2020 – Exploration of Saturn and its moons Titan and Enceladus. Orbiter, lander, ballon.

2025

  • United States Manned landing on an Asteroid[2]
  • China Manned landing on Moon (2020–30?)[5]
  • Russia Manned lunar mission[6]

Past and present spacecraft

Manned spacecraft

The Apollo 15 Command/Service Module as viewed from the Lunar Module on August 2, 1971. Used on 16 manned missions

As of 2011, only three nations have flown manned spacecraft: USSR/Russia, USA, and China. India, Japan, Europe/ESA, Iran, DPRK, Denmark, and Romania have plans for manned spacecraft (for manned suborbital rockets).

The first manned spacecraft was Vostok 1, which carried Soviet cosmonaut Yuri Gagarin into space in 1961, and completed a full Earth orbit. There were five other manned missions which used a Vostok spacecraft.[2] The second manned spacecraft was named Freedom 7, and it performed a sub-orbital spaceflight in 1961 carrying American astronaut Alan Shepard to an altitude of just over 187 kilometres (116 mi). There were five other manned missions using Mercury spacecraft.

Other Soviet manned spacecraft include the Voskhod, Soyuz, unflown as manned Zond/L1, L3, TKS, and the Salyut and Mir manned space stations. Other American manned spacecraft include the Gemini Spacecraft, Apollo Spacecraft, the Skylab space station, and the Space Shuttle with undetached European Spacelab and private US Spacehab space stations-modules. China developed unflown Shuguang and currently using Shenzhou (the first manned mission was in 2003).

All of these recovery manned spacecraft were space capsules.

The International Space Station, manned since November 2000, is a joint venture between Russia, the United States, and several other countries.

Spaceplanes

Columbia orbiter landing

Some reusable vehicles have been designed only for manned spaceflight, and these are often called spaceplanes. The first example of such was the North American X-15 spaceplane, which conducted two manned flights which reached a height over 100 km in the 1960s. The first reusable spacecraft, the X-15, was air-launched on a suborbital trajectory on July 19, 1963.

The first partially reusable orbital spacecraft, winged non-capsule, the Space Shuttle, was launched by the USA on the 20th anniversary of Yuri Gagarin's flight, on April 12, 1981. During the Shuttle era, six orbiters were built, all of which have flown in the atmosphere and five of which have flown in space. The Enterprise was used only for approach and landing tests, launching from the back of a Boeing 747 SCA and gliding to deadstick landings at Edwards AFB, California. The first Space Shuttle to fly into space was the Columbia, followed by the ChallengerDiscoveryAtlantis, and Endeavour. The Endeavour was built to replace theChallenger when it was lost in January 1986. The Columbia broke up during reentry in February 2003.

The first automatic partially reusable spacecraft was the Buran (Snowstorm), launched by the USSR on November 15, 1988, although it made only one flight. This spaceplane was designed for a crew and strongly resembled the U.S. Space Shuttle, although its drop-off boosters used liquid propellants and its main engines were located at the base of what would be the external tank in the American Shuttle. Lack of funding, complicated by the dissolution of the USSR, prevented any further flights of Buran. The Space Shuttle has since been modified to allow for autonomous re-entry in case of necessity.

Per the Vision for Space Exploration, the Space Shuttle was retired in 2011 due mainly to its old age and the high cost of the program reaching over a billion dollars per flight. The Shuttle's human transport role is to be replaced by the partially reusable Crew Exploration Vehicle (CEV) no later than 2014. The Shuttle's heavy cargo transport role is to be replaced by expendable rockets such as the Evolved Expendable Launch Vehicle (EELV) or a Shuttle Derived Launch Vehicle.

Scaled Composites' SpaceShipOne was a reusable suborbital spaceplane that carried pilots Mike Melvill and Brian Binnie on consecutive flights in 2004 to win the Ansari X Prize. The Spaceship Company will build its successor SpaceShipTwo. A fleet of SpaceShipTwos operated by Virgin Galactic should begin reusable private spaceflight carrying paying passengers in 2011.

XCOR Aerospace also plans to initiate a suborbital commercial spaceflight service with the Lynx rocketplane in 2012 through a partnership with RocketShip Tours. First test flights are planned for 2011.

Unmanned spacecraft

The Hubble Space Telescope
Jules Verne Automated Transfer Vehicle (ATV)approaches the International Space Station on Monday, March 31, 2008.
Designed as manned but flown as unmanned only spacecraft
  • Zond/L1 – lunar flyby capsule
  • L3 – capsule and lunar lander
  • TKS – capsule
  • Buran Soviet shuttle
Semi-manned – manned as space stations or part of space stations
  • Progress – unmanned USSR/Russia cargo spacecraft
  • TKS – unmanned USSR/Russia cargo spacecraft and space station module
  • Automated Transfer Vehicle (ATV) – unmanned European cargo spacecraft
  • H-II Transfer Vehicle (HTV) – unmanned Japanese cargo spacecraft
Earth Orbit satellites
  • Explorer 1 – first US satellite
  • Project SCORE – first communications satellite
  • SOHO
  • Sputnik 1 – world's first artificial satellite
  • Sputnik 2 – first animal in orbit (Laika)
  • Sputnik 5 – first capsule recovered from orbit (Vostok precursor) – animals survived
  • STEREO – Earth environment observation
  • Syncom – first geosynchronous communications satellite
  • Hubble Space Telescope – biggest orbital observatory
  • X-37 – spaceplane

As of June 2011, there are more than 2,000 spacecraft in orbit.[citation needed]

Lunar probes

  • Clementine – US Navy mission, orbited Moon, detected hydrogen at the poles
  • Kaguya JPN – Lunar orbiter
  • Luna 1 – first lunar flyby
  • Luna 2 – first lunar impact
  • Luna 3 – first images of lunar far side
  • Luna 9 – first soft landing on the Moon
  • Luna 10 – first lunar orbiter
  • Luna 16 – first unmanned lunar sample retrieval
  • Lunar Orbiter – very successful series of lunar mapping spacecraft
  • Lunar Prospector – confirmed detection of hydrogen at the lunar poles
  • Lunar Reconnaissance Orbiter – Identifies safe landing sites & Locates moon resources
  • SMART-1 ESA – Lunar Impact
  • Surveyor – the first USA soft lander
  • Chandrayaan 1 – first Indian Lunar mission
Artist's conception of Cassini–Huygensas it enters Saturn's orbit
Artist's conception of the Phoenix spacecraft as it lands on Mars
Planetary probes
  • Akatsuki JPN – a Venus orbiter
  • Cassini–Huygens – first Saturn orbiter + Titan lander
  • Galileo – first Jupiter orbiter+descent probe
  • IKAROS JPN – first solar-sail spacecraft
  • Mariner 4 – first Mars flyby, first close and high resolution images of Mars
  • Mariner 9 – first Mars orbiter
  • Mariner 10 – first Mercury flyby, first close up images
  • Mars Exploration Rover – a Mars rover
  • Mars Express – a Mars orbiter
  • Mars Global Surveyor – a Mars orbiter
  • Mars Reconnaissance Orbiter – an advanced climate, imaging, sub-surface radar, and telecommunications Mars orbiter
  • MESSENGER – first Mercury orbiter (arrival 2011)
  • Mars Pathfinder – a Mars lander + rover
  • New Horizons – first Pluto flyby (arrival 2015)
  • Pioneer 10 – first Jupiter flyby, first close up images
  • Pioneer 11 – second Jupiter flyby + first Saturn flyby (first close-up images of Saturn)
  • Pioneer Venus – first Venus orbiter+landers
  • Vega 1 – Balloon release into Venus atmosphere and landed (joint mission with Vega 2), mothership continued on to fly by Halley's Comet[citation needed]
  • Venera 4 – first soft landing on another planet (Venus)
  • Viking 1 – first soft landing on Mars
  • Voyager 2 – Jupiter flyby + Saturn flyby + first flybys/images of Neptune and Uranus
Other – deep space
  • Cluster
  • Deep Space 1
  • Deep Impact
  • Genesis
  • Hayabusa
  • Near Earth Asteroid Rendezvous
  • Stardust
  • WMAP
Fastest spacecraft
  • Helios I & II Solar Probes (252,792 km/h/157,078 mph)
Furthest spacecraft from the Sun
  • Pioneer 10 at 89.7 AU as of 2005, travelling outward at about 2.6 AU/year
  • Pioneer 11
  • Voyager 1 at 106.3 AU as of July 2008, travelling outward at about 3.6 AU/year
  • Voyager 2 at 85.49 AU as of July 2008, travelling outward at about 3.3 AU/year

Unfunded/cancelled programs

The First Test Flight of the Delta Clipper-Experimental Advanced (DC-XA), a prototype launch system
Manned spacecraft
  • Shuguang – Chinese capsule
  • Soyuz Kontakt – USSR capsule
  • Almaz – USSR space station
  • Manned Orbiting Laboratory – US space station
  • Altair – US lunar lander of Orion spacecraft
Multi-stage spaceplanes
  • X-20 – US shuttle
  • Soviet Spiral Shuttle
  • Soviet Buran Shuttle
  • ESA Hermes shuttle
  • Kipper Russian semi-shuttle/semi-capsule
  • Japanese HOPE-X shuttle
  • Chinese Shuguang Project 921-3 shuttle
SSTO spaceplanes
  • RR/British Aerospace HOTEL
  • ESA Hopper Orbiter
  • McDonnell Douglas DC-X (Delta Clipper)
  • Roton Rotor-Hybrid
  • Lockheed-Martin VentureStar

Spacecraft under development

The Orion spacecraft

Manned

  • (USA-NASA) Multi-Purpose Crew Vehicle – capsule
  • (Russia-RKA) Prospective Piloted Transport System (PPTS) – capsule
  • (USA-SpaceX ) Dragon – capsule
  • (USA-Boeing) CST-100 – capsule
  • (USA-Sierra Nevada Corporation) Dream Chaser – suborbital spaceplane
  • (USA-Blue Origin) New Shepard – VTVL capsule
  • (India-ISRO) Orbital Vehicle – capsule
  • (Europe-ESA) Advanced Crew Transportation System – capsule
  • (China-CNSA) Shenzhou – capsule
  • (Iranian Space Agency) Orbital Vehicle – capsule
  • (USA-XCOR) Lynx rocketplane – suborbital spaceplane

Unmanned

  • SpaceX Dragon – cargo delivery to the ISS
  • Orbital Sciences Cygnus – cargo delivery to the ISS
  • CNES Mars Netlander
  • James Webb Space Telescope (delayed)
  • ESA Darwin probe
  • Mars Science Laboratory rover
  • Shenzhou spacecraft Cargo
  • Terrestrial Planet Finder cancelled probe
  • System F6—a DARPA Fractionated Spacecraft demonstrator
  • Reaction Engines Limited Skylon (spacecraft)

Subsystems

A spacecraft system comprises various subsystems, dependent upon mission profile. Spacecraft subsystems comprise the spacecraft "bus" and may include: attitude determination and control (variously called ADAC, ADC or ACS), guidance, navigation and control (GNC or GN&C), communications (Comms), command and data handling (CDH or C&DH), power (EPS), thermal control (TCS), propulsion, and structures. Attached to the bus are typically payloads.

Life support Spacecraft intended for human spaceflight must also include a life support system for the crew.
Reaction control system thrusters on the nose of the U.S. Space Shuttle
Attitude control 
A Spacecraft needs an attitude control subsystem to be correctly oriented in space and respond to external torques and forces properly. The attitude control subsystem consists of sensors and actuators, together with controlling algorithms. The attitude control subsystem permits proper pointing for the science objective, sun pointing for power to the solar arrays and earth-pointing for communications.
GNC 
Guidance refers to the calculation of the commands (usually done by the CDH subsystem) needed to steer the spacecraft where it is desired to be. Navigation means determining a spacecraft's orbital elements or position. The control means adjusting the path of the spacecraft to meet mission requirements. On some missions, GNC and Attitude Control are combined into one subsystem of the spacecraft.[citation needed]
Command and data handling 
The CDH subsystem receives commands from the communications subsystem, performs validation and decoding of the commands, and distributes the commands to the appropriate spacecraft subsystems and components. The CDH also receives housekeeping data and science data from the other spacecraft subsystems and components and packages the data for storage on a data recorder transmission to the ground via the communications subsystem. Other functions of the CDH include maintaining the spacecraft clock and state-of-health monitoring.
Power 
Spacecraft need an electrical power generation and distribution subsystem for powering the various spacecraft subsystems. For spacecraft near the Sun, solar panels are frequently used to generate electrical power. Spacecraft designed to operate in more distant locations, for example, Jupiter, might employ a Radioisotope Thermoelectric Generator (RTG) to generate electrical power. Electrical power is sent through power conditioning equipment before it passes through a power distribution unit over an electrical bus to other spacecraft components. Batteries are typically connected to the bus via a battery charge regulator, and the batteries are used to provide electrical power during periods when primary power is not available, for example when a Low Earth Orbit (LEO) spacecraft is eclipsed by the Earth.
Thermal control 
Spacecraft must be engineered to withstand transit through the Earth's atmosphere and the space environment. They must operate in a vacuum with temperatures potentially ranging across hundreds of degrees Celsius as well as (if subject to reentry) in the presence of plasmas. Material requirements are such that either high melting temperature, low-density materials such as beryllium and reinforced carbon-carbon or (possibly due to the lower thickness requirements despite its high density)tungsten or ablative carbon/carbon composites are used. Depending on mission profile, spacecraft may also need to operate on the surface of another planetary body. The thermal control subsystem can be passive, dependent on the selection of materials with specific radiative properties. Active thermal control makes use of electrical heaters and certain actuators such as louvres to control temperature ranges of equipment within specific ranges.
A launch vehicle, like this Proton rocket, is typically used to bring a spacecraft to orbit.
Propulsion 
Spacecraft may or may not have a propulsion subsystem, depending upon whether or not the mission profile calls for propulsion. The Swift spacecraft is an example of a spacecraft that does not have a propulsion subsystem. Typically, though, LEO spacecraft (for example Terra (EOS AM-1) include a propulsion subsystem for altitude adjustments (called drag make-up manoeuvres) and inclination adjustment manoeuvres. A propulsion system is also needed for spacecraft that perform momentum management manoeuvres. Components of a conventional propulsion subsystem include fuel, tankage, valves, pipes, and thrusters. The TCS interfaces with the propulsion subsystem by monitoring the temperature of those components, and by preheating tanks and thrusters in preparation for a spacecraft manoeuvre.
Structures 
Spacecraft must be engineered to withstand launch loads imparted by the launch vehicle and must have a point of attachment for all the other subsystems. Depending upon mission profile, the structural subsystem might need to withstand loads imparted by entry into the atmosphere of another planetary body, and land on the surface of another planetary body.
Payload 
The payload is dependent upon the mission of the spacecraft, and is typically regarded as the part of the spacecraft "that pays the bills". Typical payloads could include scientific instruments (cameras, telescopes, or particle detectors, for example), cargo, or a human crew.
Ground segment 
The ground segment, though not technically part of the spacecraft, is vital to the operation of the spacecraft. Typical components of a ground segment in use during normal operations include a mission operations facility where the flight operations team conducts the operations of the spacecraft, a data processing and storage facility, ground stations to radiate signals to and receive signals from the spacecraft, and a voice and data communications network to connect all mission elements.
Launch vehicle 
The launch vehicle propels the spacecraft from the Earth's surface, through the atmosphere, and into an orbit, the exact orbit being dependent upon mission configuration. The launch vehicle may be expendable or reusable.

The first steps of putting a man-made object into space were taken by German scientists during World War II while testing the V2 rocket which became the first human-made object in space on October 3, 1942, with the launching of V-4. After the war, the U.S. used German scientists and their captured rockets in programs for both military and civilian research. The first scientific exploration of space was the cosmic radiation experiment launched by the U.S. on a V2 rocket on May 10, 1946. The first images of Earth taken from space followed the same year while the first animal experiment saw fruit flies lifted into space in 1947, both also on modified V2s launched by Americans. Starting in 1947, the Soviets, also with the help of German teams, launched sub-orbital V2 rockets and their own variant, the R-1, including radiation and animal experiments on some flights. These suborbital experiments only allowed a very short time in space which limited their usefulness.

First flights
Sputnik 1, the first artificial satellite orbited earth at 939 km (583 mi) to 215 km (134 mi) in 1957, and was soon followed by Sputnik 2. See First satellite by country (Replica Pictured)

The first successful orbital launch was of the Soviet unmanned Sputnik 1 ("Satellite 1") mission 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 emitted "beeps" that could be heard by radios around the globe. Analysis of the radio signals was used to gather information about the electron density of the ionosphere, while temperature and pressure data was encoded in the duration of radio beeps. The results indicated that the satellite was not punctured by a meteoroid. Sputnik 1 was launched by an R-7 rocket. It burned up upon re-entry on January 3, 1958.

This success led to an escalation of the American space program, which unsuccessfully attempted to launch a Vanguard satellite into orbit two months later. On January 31, 1958, the U.S. successfully orbited Explorer 1 on a Juno rocket. In the meantime, the Soviet dog Laika became the first animal in orbit on November 3, 1957.

First human flights

The first successful human spaceflight was Vostok 1 ("East 1"), carrying 27-year-old Russian cosmonaut Yuri Gagarin on April 12, 1961. The spacecraft completed one orbit around the globe, lasting about 1 hour and 48 minutes. Gagarin's flight resonated around the world; it was a demonstration of the advanced Soviet space program and it opened an entirely new era of space exploration: human spaceflight.

Apollo CSM in lunar orbit

The U.S. first launched a person into space within a month of Vostok 1 with Alan Shepard's suborbital flight in Mercury-Redstone 3. The orbital flight was achieved by the United States when John Glenn's Mercury-Atlas 6 orbited the Earth on February 20, 1962.

Valentina Tereshkova, the first woman in space, orbited the Earth 48 times aboard Vostok 6 on June 16, 1963.

China first launched a person into space 42 years after the launch of Vostok 1, on October 15, 2003, with the flight of Yang Liwei aboard the Shenzhou 5 (Spaceboat 5) spacecraft.

First planetary explorations

The first artificial object to reach another celestial body was Luna 2 in 1959. The first automatic landing on another celestial body was performed by Luna 9 in 1966. Luna 10 became the first artificial satellite of another celestial body.

The first manned landing on another celestial body was performed by Apollo 11 in its lunar landing on July 20, 1969.

The first successful interplanetary flyby was the 1962 Mariner 2 flyby of Venus (closest approach 34,773 kilometres). Flybys for the other planets were first achieved in 1965 for Mars by Mariner 4, 1973 for Jupiter by Pioneer 10, 1974 for Mercury by Mariner 10, 1979 for Saturn by Pioneer 11, 1986 for Uranus by Voyager 2, and 1989 for Neptune by Voyager 2.

The first interplanetary surface mission to return at least limited surface data from another planet was the 1970 landing of Venera 7 on Venus 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 much longer duration surface missions were achieved, including over 6 years of Mars surface operation by Viking 1 from 1975 to 1982 and over 2 hours of transmission from the surface of Venus by Venera 13 in 1982 (the longest ever Soviet planetary surface mission).

Key people in early space exploration

The dream of stepping into the outer reaches of the Earth's atmosphere was driven by the fiction of Jules Verne and H.G.Wells, and rocket technology was developed to try and realise this vision. The German V2 was the first rocket to travel into space, overcoming the problems of thrust and material failure. During the final days of World War II, this technology was obtained by both the Americans and Soviets as were its designers. The initial driving force for further development of the technology was a weapons race for intercontinental ballistic missiles (ICBMs) to be used as long-range carriers for fast nuclear weapon delivery, but in 1961 when USSR launched the first man into space, the U.S. declared itself to be in a "Space Race" with Russia.

  • Konstantin Tsiolkovsky, Robert Goddard, Hermann Oberth, and Reinhold Tiling laid the groundwork of rocketry in the early years of the 20th century.
  • Wernher von Braun was the lead rocket engineer for Nazi Germany's World War II V-2 rocket project. In the last days of the war, he led a caravan of workers in the German rocket program to the American lines, where they surrendered and were brought to the USA to work on U.S. rocket development ("Operation Paperclip"). He acquired American citizenship and led the team that developed and launched Explorer 1, the first American satellite. Von Braun later led the team at NASA's Marshall Space Flight Center which developed the Saturn V moon rocket.
  • Initially, the race for space was often led by Sergei Korolyov, whose legacy includes both the R7 and Soyuz—which remain in service to this day. Korolev was the mastermind behind the first satellite, the first man (and first woman) in orbit and first spacewalk. Until his death his identity was a closely guarded state secret; not even his mother knew that he was responsible for creating the Russian space program.
  • Kerim Kerimov was one of the founders of the Soviet space program and was one of the lead architects behind the first human spaceflight (Vostok 1) alongside Sergey Korolyov. After Korolyov's death in 1966, Kerimov became the lead scientist of the Soviet space program and was responsible for the launch of the first space stations from 1971 to 1991, including the Salyut and Mir series, and their precursors in 1967, the Cosmos 186and Cosmos 188.
Robert Gilruth

Other key people included:

  • Valentin Glushko held the role of Chief Engine Designer for USSR. Glushko designed many of the engines used on the early Soviet rockets but was constantly at odds with Korolyov.
  • Vasily Mishin was Chief Designer working under Sergey Korolyov and one of first Soviets to inspect the captured German V2 design. Following the death of Sergei Korolev, Mishin was held responsible for the Soviet failure to be the first country to place a man on the moon.
  • Bob Gilruth was the NASA head of the Space Task Force and director of 25 manned space flights. Gilruth was the person who suggested to John F. Kennedy that the Americans take the bold step of reaching the Moon in an attempt to reclaim space superiority from the Soviets.
  • Christopher C. Kraft, Jr. was NASA's first flight director, who oversaw development of Mission Control and associated technologies and procedures.
  • Maxime Faget was the designer of the Mercury capsule; he played a key role in designing the Gemini and Apollo spacecraft and contributed to the design of the Space Shuttle.

Targets of exploration

The Sun

While the Sun will probably not be physically explored in the close future, one of the reasons for going into space includes knowing more about the Sun. Once above the atmosphere in particular and 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 most space weather, which can affect power generation and transmission systems on Earth and interfere with, and even damage, satellites and space probes.

MESSENGER image of Mercury
A MESSENGER image from 18,000 km showing a region about 500 km across

Mercury

Mercury remains the least explored of the inner planets. As of May 2011, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury.MESSENGER entered orbit around Mercury in March 2011, to further investigate the observations made by Mariner 10 in 1975 (Munsell, 2006b). The third mission to Mercury, scheduled to arrive in 2020, BepiColombo is to include two probes. BepiColombo is a joint mission between Japan and the European Space Agency. MESSENGER and BepiColombo are intended to gather complementary data to help scientists understand many of the mysteries discovered by Mariner 10's flybys.

Flights to other planets within the Solar System are accomplished at a cost of energy, which is 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.

Mariner 10 image of Venus

Venus

Venus was the first target of interplanetary flyby and lander missions and, despite one of the most hostile surface environments in the solar system, has had more landers sent to it (nearly all from the Soviet Union) than any other planet in the solar system. The first successful Venus flyby was the American Mariner 2 spacecraft, which flew past Venus in 1962. Mariner 2 has been followed by several other flybys by multiple space agencies often as part of missions using a Venus flyby to provide a gravitational assist en route to other celestial bodies. In 1967 Venera 4 became the first probe to enter and directly examine the atmosphere of Venus. In 1970 Venera 7 became the first successful lander to reach the surface of Venus and by 1985 it had been followed by eight additional successful Soviet Venus landers which provided images and other direct surface data. Starting in 1975 with the Soviet orbiterVenera 9 some ten successful orbiter missions have been sent to Venus, including later missions which were able to map the surface of Venus using radar to pierce the obscuring atmosphere.

The "marble" Earth picture taken by Apollo 17
First television image of Earth from space

Earth

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 belts was unknown until their discovery by the United States' first artificial satellite, Explorer 1. These belts contain radiation trapped by the Earth's magnetic fields, which currently renders construction of habitable space stations above 1000 km impractical. Following this early unexpected discovery, a large number of Earth observation satellites have been deployed specifically to explore the Earth from a space-based perspective. These satellites have significantly contributed to the understanding of a variety of earth-based phenomena. For instance, the hole in the ozone layer was found by an artificial satellite that was exploring Earth's atmosphere, and satellites have allowed for the discovery of archaeological sites or geological formations that were difficult or impossible to otherwise identify.

The Moon as seen from the Earth
Luc Viatour (Belgium)
Apollo 16 astronaut John Young

Earth's Moon

Earth's Moon was the first celestial body to be the object of space exploration. It holds the distinctions of being the first remote celestial object to be flown by, orbited, and landed upon by spacecraft, and the only remote celestial object ever to be visited by humans.

In 1959 the Soviets obtained the first images of the far side of the Moon, never previously visible to humans. The U.S. exploration of the Moon began with the Ranger 4 impactor in 1962. Starting in 1966 the Soviets successfully deployed a number of landers to the Moon which were able to obtain data directly from the Moon's surface; just four months later, Surveyor 1 marked the debut of a successful series of U.S. lenders. The Soviet unmanned missions culminated in the Lunokhod program in the early '70s which included the first unmanned rovers and also successfully returned lunar soil samples to the Earth for study. This marked the first (and to date the only) automated return of extraterrestrial soil samples to the Earth. Unmanned exploration of the Moon continues with various nations periodically deploying lunar orbiters and in 2008 the Indian Moon Impact Probe.

Manned exploration of the Moon began in 1968 with the Apollo 8 mission that successfully orbited the Moon, the first time any extraterrestrial object was orbited by humans. In 1969 the Apollo 11mission marked the first time humans set foot upon another world. Manned exploration of the Moon did not continue for long, however. The Apollo 17 mission in 1972 marked the most recent human visit to another world, and there is no further planned human exploration of an extraterrestrial body, though robotic missions are still pursued vigorously.

Mars

The exploration of Mars has been an important part of the space exploration programs of the Soviet Union (later Russia), the United States, Europe, and Japan. Dozens of robotic spacecraft, including orbiters, landers, and rovers, have been launched toward Mars since the 1960s. These missions were aimed at gathering data about current conditions and answering questions about the history of Mars. The questions raised by the scientific community are expected to not only give a better appreciation of the red planet but also yield further insight into the past, and possible future, of Earth.

The exploration of Mars has come at a considerable financial cost with roughly two-thirds of all spacecraft destined for Mars failing before completing their missions, with some failing before they even began. Such a high failure rate can be attributed to the complexity and a large number of variables involved in an interplanetary journey and has led researchers to jokingly speak of The Great Galactic Ghoul which subsists on a diet of Mars probes. This phenomenon is also informally known as the Mars Curse.

Phobos

The Russian space mission Phobos-Grunt, Scheduled to launch in 2011, will begin exploration of the Phobos and Martian circumterrestrial orbit, and study whether the moons of Mars or at least Phobos, could be a "trans-shipment point" for spaceships travelling to Mars.

Asteroids and comets

Until the advent of space travel, objects in the asteroid belt were merely pinpricks of light in even the largest telescopes, their shapes and terrain remaining a mystery. Several asteroids have now been visited by probes, the first of which was Galileo, which flew past two: 951 Gaspra in 1991, followed by 243 Ida in 1993. Both of these lay near enough to Galileo's planned trajectory to Jupiter that they could be visited at the acceptable cost. The first landing on an asteroid was performed by the NEAR Shoemaker probe in 2000, following an orbital survey of the object. The dwarf planet Ceres and the asteroid 4 Vesta, two of the three largest asteroids, are targets of NASA's Dawn mission, launched in 2007.

While many comets have been closely studied from Earth sometimes with centuries-worth of observations, only a few comets have been closely visited. A few long-period comets are currently the furthest known objects in the solar system. In 1985, theInternational Cometary Explorer conducted the first comet fly-by (21P/Giacobini-Zinner) before joining the Halley Armada studying the famous comet. The Deep Impact probe smashed into 9P/Tempel to learn more about its structure and composition while the Stardust mission returned samples of another comet's tail. The Philae lander will attempt to land on a comet in 2014.

Hayabusa was an unmanned spacecraft developed by the Japan Aerospace Exploration Agency to return a sample of material from a small near-Earth asteroid named 25143 Itokawa to Earth for further analysis. Hayabusa was launched on 9 May 2003 and rendezvoused with Itokawa in mid-September 2005. After arriving at Itokawa, Hayabusa studied the asteroid's shape, spin, topography, colour, composition, density, and history. In November 2005, it landed on the asteroid to collect samples. The spacecraft returned to Earth on 13 June 2010.

Deep space exploration

Jupiter

Voyager 1 image of Jupiter
Image of Io taken by the Galileo spacecraft

The exploration of Jupiter has consisted solely of a number of automated NASA spacecraft visiting the planet since 1973. A large majority of the missions have been "flybys", in which detailed observations are taken without the probe landing or entering orbit; the Galileo spacecraft is the only one to have orbited the planet. As Jupiter is believed to have only a relatively small rocky core and no real solid surface, a landing mission is nearly impossible.

Reaching Jupiter from Earth requires a delta-v of 9.2 km/s, which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit. 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.

Jupiter has over 60 known moons, many of which have relatively little-known information about them.

A picture of Saturn taken by Voyager 2.
Huygens image from the surface ofTitan

Saturn

Saturn has been explored only through unmanned spacecraft launched by NASA, including one mission (Cassini–Huygens) planned and executed in cooperation with other space agencies. These missions consist of flybys in 1979 by Pioneer 11, in 1980 by Voyager 1, in 1982 by Voyager 2 and an orbital mission by the Cassini spacecraft which entered orbit in 2004 and is expected to continue its mission well into 2010.

Saturn has at least 62 satellites, although the exact number is debatable since Saturn's rings are made up of vast numbers of independently orbiting objects of varying sizes. The largest of the moons is Titan. Titan holds the distinction of being the only moon in the solar system with an atmosphere denser and thicker than that of the Earth. As a result of the deployment from the Cassini spacecraft of the Huygens probe and its successful landing on Titan, Titan also holds the distinction of being the only moon (apart from Earth's own Moon) to be successfully explored with a lender.

Uranus from Voyager 2
Voyager 2 image showing the tortured surface of Miranda

Uranus

The exploration of Uranus has been entirely through the Voyager 2 spacecraft, with no other visits currently planned. Given 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 and magnetosphere. Voyager 2also examined its ring system and the moons of Uranus including all five of the previously known moons, while discovering an additional ten previously unknown moons.

Images of Uranus proved to have a very uniform appearance, with no evidence of the dramatic storms or atmospheric banding evident on Jupiter and Saturn. Great effort was required to even identify a few clouds in the images of the planet. The magnetosphere of Uranus, however, proved to be completely unique and proved to be profoundly affected by the planet's unusual axial tilt. In contrast to the bland appearance of Uranus itself, striking images were obtained of the moons of Uranus, including evidence that Miranda had been unusually geologically active.

Picture of Neptune taken by Voyager 2
Triton as imaged by Voyager 2

Neptune

The exploration of Neptune began with the August 25, 1989, Voyager 2 flyby, the sole visit to the system as of 2009. The possibility of a Neptune Orbiter has been discussed, but no other missions have been given serious thought.

Although the extremely uniform appearance of Uranus during Voyager 2's visit in 1986 had led to expectations that Neptune would also have few visible atmospheric phenomena, Voyager 2 found that Neptune had obvious banding, visible clouds, auroras, and even a conspicuous anticyclone storm system rivalled in size only by Jupiter's small Spot. Neptune also proved to have the fastest winds of any planet in the solar system, measured as high as 2,100 km/h. Voyager 2 also examined Neptune's ring and moon system. It discovered 900 complete rings and additional partial ring "arcs" around Neptune. In addition to examining Neptune's three previously known moons, Voyager 2 also discovered five previously unknown moons, one of which, Proteus, proved to be the last largest moon in the system. Data from Voyager further reinforced the view that Neptune's largest moon, Triton, is a captured Kuiper belt object.

Pluto

Pluto and Charon (1994)

The dwarf planet Pluto (considered a planet until the IAU redefinition of "planet" in October 2006) presents significant challenges for spacecraft because of its great distance from Earth (requiring high velocity for reasonable trip times) and small mass (making capture into orbit very difficult at present). Voyager 1 could have visited Pluto, but controllers opted instead for a close flyby of Saturn's moon Titan, resulting in a trajectory incompatible with a Pluto flyby. Voyager 2 never had a plausible trajectory for reaching Pluto.

Pluto continues to be of great interest, despite its reclassification as the lead and nearest member of a new and growing class of distant icy 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"). After an intense political battle, a mission to Pluto dubbedNew Horizons was granted funding from the US government in 2003. New Horizons was launched successfully on January 19, 2006. In early 2007 the craft made use of a gravity assist from Jupiter. Its closest approach to Pluto will be on July 14, 2015; scientific observations of Pluto will begin five months prior to closest approach and will continue for at least a month after the encounter.

Future of space exploration

The European Space Agency's Columbus Module at the International Space Station launched into space on the U.S. Space Shuttle mission STS-122 in 2008

In the 2000s, several plans for space exploration were announced; both government entities and the private sector have space exploration objectives. The NASA Authorization Act of 2010 provides objectives for American space exploration.

Technical avenues for US space exploration beyond low earth orbit (LEO) are being investigated by a NASA multi-center Technology Applications Assessment Team led from the Johnson Spaceflight Center. This study has as of January 2011 outlined "Nautilus-X", a concept for a multi-mission space exploration vehicle useful for missions beyond LEO, of up to 24 months duration for a crew of up to six. Although adaptable to a variety of mission-specific propulsion units of various low thrust, high specific impulse (Isp) designs, a nuclear ion-electric drive is shown for illustrative purposes. It is intended for integration and checkout at the International Space Station (ISS) and would be suitable for deep-space missions from the ISS to and beyond the Moon, including Earth/Moon L1, Sun/Earth L2, near-Earth asteroidal, and Mars orbital destinations. It incorporates a reduced-g centrifuge providing artificial gravity for crew health to ameliorate the effects of long-term 0g exposure, and the capability to mitigate the space radiation environment.

NASA laid out its vision for deep space exploration on Sept 14, 2011. NASA proposes to move forward with the development of the Space Launch System -- an advanced heavy-lift launch vehicle that will provide an entirely new capability for human exploration beyond Earth's orbit.

The Space Launch System, or SLS, will be designed to carry the Orion Multi-Purpose Crew Vehicle, as well as important cargo, equipment and science experiments to Earth's orbit and destinations beyond. Additionally, the SLS will serve as a backup for commercial and international partner transportation services to the International Space Station.

The SLS rocket will incorporate technological investments from the Space Shuttle program and the Constellation program in order to take advantage of proven hardware and cutting-edge tooling and manufacturing technology that will significantly reduce development and operations costs. It will use a liquid hydrogen and liquid oxygen propulsion system, which will include the RS-25D/E from the Space Shuttle program for the core stage and the J-2X engine for the upper stage. SLS will also use solid rocket boosters for the initial development flights, while follow-on boosters will be competed based on performance requirements and affordability considerations. The SLS will have an initial lift capacity of 70 metric tonnes. That's more than 154,000 pounds, or 77 tonnes, roughly the weight of 40 sport utility vehicles. The lift capacity will be evolvable to 130 metric tonnes -- more than 286,000 pounds, or 143 tonnes -- enough to lift 75 SUVs. The first developmental flight, or mission, is targeted for the end of 2017. 

Rationales

Astronaut Buzz Aldrin, had a personal Communion service when he first arrived on the surface of the Moon.

The research that is conducted by national space exploration agencies, such as NASA and Roscosmos, is one of the reasons supporters cite to justify government expenses. Economic analyses of the NASA programs often showed ongoing economic benefits (such as NASA spin-offs), generating many times the revenue of the cost of the program.

Another claim is that space exploration is a necessity to mankind and that staying on Earth will lead to extinction. Some of the reasons are the lack of natural resources, comets, nuclear war, and worldwide epidemic. Stephen Hawking, the 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."

NASA has produced a series of public service announcement videos supporting the concept of space exploration.

Overall, the public remains largely supportive of both manned and unmanned space exploration. According to an Associated Press Poll conducted in 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.

Arthur C. Clarke (1950) presented a summary of motivations for the human exploration of space in his non-fiction semi-technical monograph Interplanetary Flight. He argued that humanity's choice is essentially between an expansion of the Earth into space, versus cultural (and eventually biological) stagnation and death.

Opposition

Critics such as the late physicist and Nobel prize winner Richard Feynman have contended that human space travel (as distinguished from space exploration in general, such as robotic missions) has never achieved any major scientific breakthroughs.

Related topics

Delta-v's in km/s for various orbital manoeuvres

Spaceflight

Spaceflight is the use of space technology to achieve the flight of spacecraft into and through outer space.

Spaceflight is used in space exploration, and also in commercial activities like space tourism and satellite telecommunications. Additional non-commercial uses of spaceflight include space observatories, reconnaissance satellites and other earth observation satellites.

A spaceflight typically begins with a rocket launch, which provides the initial thrust to overcome the force of gravity and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft—both when unpropelled and when under propulsion—is covered by the area of study called astrodynamics. Some spacecraft remain in space indefinitely, some disintegrate during atmospheric reentry, and others reach a planetary or lunar surface for landing or impact.

Satellites

Satellites are used for a large number of purposes. Common types include military (spy) and civilian Earth observation satellites, communication satellites, navigation satellites, weather satellites, and research satellites. Space stations and human spacecraft in orbit are also satellites.

Commercialization of space

Current examples of the commercial use of space include satellite navigation systems, satellite television and satellite radio. Space tourism is the recent phenomenon of space travel by individuals for the purpose of personal pleasure.

Militarization of space

While military activities have taken place in space and space is an operating location for many military spacecraft (such as imaging & communications satellites) or a temporary transit media for weapons (such as ballistic missiles), permanent placement of large-scale operational weapons in space has never been conducted.

Astrobiology

Astrobiology is the interdisciplinary study of life in the universe, combining aspects of astronomy, biology and geology. It is focused primarily on the study of the origin, distribution and evolution of life. It is also known as exobiology (from Greek: ???,ex, "outside"). The term "Xenobiology" has been used as well, but this is technically incorrect because its terminology means "biology of the foreigners". Astrobiologists must also consider the possibility of life that is chemically entirely distinct from any life found on earth. In the Solar System, some of the prime locations for current or past astrobiology are on Enceladus, Europa, Mars, and Titan.

Image of the Sun from 7 June 1992 showing some sunspots

Space colonization

Space colonisation, 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 theMoon or Mars, using significant amounts of in-situ resource utilisation.

To date, the longest human occupation of space is the International Space Station which has been in continuous use for 10 years, 325 days. Valeri Polyakov's record single spaceflight of almost 438 days aboard the Mir space station has not been surpassed. Long-term stays in space reveal issues with bone and muscle loss in low gravity, immune system suppression, and radiation exposure.

Many past and current concepts for the continued exploration and colonisation of space focus on a return to the Moon as a "stepping stone" to the other planets, especially Mars. At the end of 2006, NASA announced they were planning to build a permanent Moon base with continual presence by 2024.

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