Human spaceflight
Human spaceflight is spaceflight with a crew or passengers aboard a spacecraft, often with the spacecraft being operated directly by the onboard human crew. Spacecraft can also be remotely operated from ground stations on Earth, or autonomously, without any direct human involvement. People trained for spaceflight are called astronauts, cosmonauts, or taikonauts ; and non-professionals are referred to as spaceflight participants or spacefarers.
The first human in space was Soviet cosmonaut Yuri Gagarin, who launched as part of the Soviet Union's Vostok program on 12 April 1961 at the beginning of the Space Race. On 5 May 1961, Alan Shepard became the first American in space, as part of Project Mercury. Humans traveled to the Moon nine times between 1968 and 1972 as part of the United States' Apollo program, and have had a continuous presence in space for on the International Space Station. On 15 October 2003, the first Chinese taikonaut, Yang Liwei, went to space as part of Shenzhou 5, the first Chinese human spaceflight. As of December 2025, humans have not traveled beyond low Earth orbit since the Apollo 17 lunar mission in December 1972.
Currently, the United States, Russia, and China are the only countries with public or commercial human spaceflight-capable programs. Non-governmental spaceflight companies have been working to develop human space programs of their own, e.g. for space tourism or commercial in-space research. The first private human spaceflight launch was a suborbital flight on SpaceShipOne on June 21, 2004. The first commercial orbital crew launch was by SpaceX in May 2020, transporting NASA astronauts to the ISS under United States government contract.
History
Cold War era
Human spaceflight capability was first developed during the Cold War between the United States and the Soviet Union. These nations developed intercontinental ballistic missiles for the delivery of nuclear weapons, producing rockets large enough to be adapted to carry the first artificial satellites into low Earth orbit.After the first satellites were launched in 1957 and 1958 by the Soviet Union, the US began work on Project Mercury, with the aim of launching men into orbit. The USSR was secretly pursuing the Vostok program to accomplish the same thing, and launched the first human into space, the cosmonaut Yuri Gagarin. On 12 April 1961, Gagarin was launched aboard Vostok 1 on a Vostok 3KA rocket and completed a single orbit. On 5 May 1961, the US launched its first astronaut, Alan Shepard, on a suborbital flight aboard Freedom 7 on a Mercury-Redstone rocket. Unlike Gagarin, Shepard manually controlled his spacecraft's attitude. On 20 February 1962, John Glenn became the first American in orbit, aboard Friendship 7 on a Mercury-Atlas rocket. The USSR launched five more cosmonauts in Vostok capsules, including the first woman in space, Valentina Tereshkova, aboard Vostok 6 on 16 June 1963. Through 1963, the US launched a total of two astronauts in suborbital flights and four into orbit. The US also made two North American X-15 flights, that exceeded the Kármán line, the altitude used by the Fédération Aéronautique Internationale to denote the edge of space.
In 1961, US President John F. Kennedy raised the stakes of the Space Race by setting the goal of landing a man on the Moon and returning him safely to Earth by the end of the 1960s. That same year, the US began the Apollo program of launching three-man capsules atop the Saturn family of launch vehicles. In 1962, the US began Project Gemini, which flew 10 missions with two-man crews launched by Titan II rockets in 1965 and 1966. Gemini's objective was to support Apollo by developing American orbital spaceflight experience and techniques to be used during the Moon mission.
Meanwhile, the USSR remained silent about their intentions to send humans to the Moon and proceeded to stretch the limits of their single-pilot Vostok capsule by adapting it to a two or three-person Voskhod capsule to compete with Gemini. They were able to launch two orbital flights in 1964 and 1965 and achieved the first spacewalk, performed by Alexei Leonov on Voskhod 2, on 8 March 1965. However, the Voskhod did not have Gemini's capability to maneuver in orbit, and the program was terminated. The US Gemini flights did not achieve the first spacewalk, but overcame the early Soviet lead by performing several spacewalks, solving the problem of astronaut fatigue caused by compensating for the lack of gravity, demonstrating the ability of humans to endure two weeks in space, and performing the first space rendezvous and docking of spacecraft.
The US succeeded in developing the Saturn V rocket necessary to send the Apollo spacecraft to the Moon, and sent Frank Borman, James Lovell, and William Anders into 10 orbits around the Moon in Apollo 8 in December 1968. In 1969, Apollo 11 accomplished Kennedy's goal by landing Neil Armstrong and Buzz Aldrin on the Moon on 21 July and returning them safely on 24 July, along with Command Module pilot Michael Collins. Through 1972, a total of six Apollo missions landed 12 men to walk on the Moon, half of which drove electric powered vehicles on the surface. The crew of Apollo 13—Jim Lovell, Jack Swigert, and Fred Haise—survived an in-flight spacecraft failure, they flew by the Moon without landing, and returned safely to Earth.
During this time, the USSR secretly pursued crewed lunar orbiting and landing programs. They successfully developed the three-person Soyuz spacecraft for use in the lunar programs, but failed to develop the N1 rocket necessary for a human landing, and discontinued their lunar programs in 1974. Upon losing the Moon race they concentrated on the development of space stations, using the Soyuz as a ferry to take cosmonauts to and from the stations. They started with a series of Salyut sortie stations from 1971 to 1986.
Post-Apollo era
In 1969, Nixon appointed his vice president, Spiro Agnew, to head a Space Task Group to recommend follow-on human spaceflight programs after Apollo. The group proposed an ambitious Space Transportation System based on a reusable Space Shuttle, which consisted of a winged, internally fueled orbiter stage burning liquid hydrogen, launched with a similar, but larger kerosene-fueled booster stage, each equipped with airbreathing jet engines for powered return to a runway at the Kennedy Space Center launch site. Other components of the system included a permanent, modular space station; reusable space tug; and nuclear interplanetary ferry, leading to a human expedition to Mars as early as 1986 or as late as 2000, depending on the level of funding allocated. However, Nixon knew the American political climate would not support congressional funding for such an ambition, and killed proposals for all but the Shuttle, possibly to be followed by the space station. Plans for the Shuttle were scaled back to reduce development risk, cost, and time, replacing the piloted fly-back booster with two reusable solid rocket boosters, and the smaller orbiter would use an expendable external propellant tank to feed its hydrogen-fueled main engines. The orbiter would have to make unpowered landings.In 1973, the US launched the Skylab sortie space station and inhabited it for 171 days with three crews ferried aboard an Apollo spacecraft. During that time, President Richard Nixon and Soviet general secretary Leonid Brezhnev were negotiating an easing of Cold War tensions known as détente. During the détente, they negotiated the Apollo–Soyuz program, in which an Apollo spacecraft carrying a special docking adapter module would rendezvous and dock with Soyuz 19 in 1975. The American and Soviet crews shook hands in space, but the purpose of the flight was purely symbolic.
The two nations continued to compete rather than cooperate in space, as the US turned to developing the Space Shuttle and planning the space station, which was dubbed Freedom. The USSR launched three Almaz military sortie stations from 1973 to 1977, disguised as Salyuts. They followed Salyut with the development of Mir, the first modular, semi-permanent space station, the construction of which took place from 1986 to 1996. Mir orbited at an altitude of, at an orbital inclination of 51.6°. It was occupied for 4,592 days and made a controlled reentry in 2001.
The Space Shuttle started flying in 1981, but the US Congress failed to approve sufficient funds to make Space Station Freedom a reality. A fleet of four shuttles was built: Columbia, Challenger, Discovery, and Atlantis. A fifth shuttle, Endeavour, was built to replace Challenger, which was destroyed in an accident during launch that killed 7 astronauts on 28 January 1986. From 1983 to 1998, twenty-two Shuttle flights carried components for a European Space Agency sortie space station called Spacelab in the Shuttle payload bay.
The USSR copied the US's reusable Space Shuttle orbiter, which they called Buran-class orbiter or simply Buran, which was designed to be launched into orbit by the expendable Energia rocket, and was capable of robotic orbital flight and landing. Unlike the Space Shuttle, Buran had no main rocket engines, but like the Space Shuttle orbiter, it used smaller rocket engines to perform its final orbital insertion. A single uncrewed orbital test flight took place in November 1988. A second test flight was planned by 1993, but the program was canceled due to lack of funding and the dissolution of the Soviet Union in 1991. Two more orbiters were never completed, and the one that performed the uncrewed flight was destroyed in a hangar roof collapse in May 2002.
US / Russian cooperation
The dissolution of the Soviet Union in 1991 brought an end to the Cold War and opened the door to true cooperation between the US and Russia. The Soviet Soyuz and Mir programs were taken over by the Russian Federal Space Agency, which became known as the Roscosmos State Corporation. The Shuttle-Mir Program included American Space Shuttles visiting the Mir space station, Russian cosmonauts flying on the Shuttle, and an American astronaut flying aboard a Soyuz spacecraft for long-duration expeditions aboard Mir.In 1993, President Bill Clinton secured Russia's cooperation in converting the planned Space Station Freedom into the International Space Station. Construction of the station began in 1998. The station orbits at an altitude of and an orbital inclination of 51.65°. Several of the Space Shuttle's 135 orbital flights were to help assemble, supply, and crew the ISS. Russia has built half of the International Space Station and has continued its cooperation with the US.