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Human spaceflight (also referred to as crewed spaceflight, or more historically manned 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 telerobotic from ground stations on Earth, or Autonomous robot, without any direct human involvement. People trained for spaceflight are called (American or other), cosmonauts (Russian), or taikonauts (Chinese); and non-professionals are referred to as spaceflight participants or spacefarers.
The first human in space was Soviet Union cosmonaut Yuri Gagarin, who launched as part of the Soviet Union's Vostok program on Cosmonautics Day 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 (ISS). 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 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.
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 programme 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. (2026). 9780387341750, Springer. ISBN 9780387341750 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 space capsule, 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 (90 and 91, piloted by Joseph A. Walker), that exceeded the Kármán line, the altitude used by the Fédération Aéronautique Internationale (FAI) 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, Jim 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 , using the Soyuz as a ferry to take cosmonauts to and from the stations. They started with a series of Salyut program sortie stations from 1971 to 1986.
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 programme-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.
In 1993, President Bill Clinton secured Russia's cooperation in converting the planned Space Station Freedom into the International Space Station (ISS). 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.
In 1992, under China Manned Space Program (CMS), also known as "Project 921", authorization and funding was given for the first phase of a third, successful attempt at crewed spaceflight. To achieve independent human spaceflight capability, China developed the Shenzhou spacecraft and Long March 2F rocket dedicated to human spaceflight in the next few years, along with critical infrastructures like a new launch site and flight control center being built. The first uncrewed spacecraft, Shenzhou 1, was launched on 20 November 1999 and recovered the next day, marking the first step of the realization of China's human spaceflight capability. Three more uncrewed missions were conducted in the next few years in order to verify the key technologies. On 15 October 2003 Shenzhou 5, China's first crewed spaceflight mission, put Yang Liwei in orbit for 21 hours and returned safely back to Inner Mongolia, making China the third nation to launch a human into orbit independently.
The goal of the second phase of CMS was to make technology breakthroughs in extravehicular activities (EVA, or spacewalk),space rendezvous, and docking to support short-term human activities in space. On 25 September 2008 during the flight of Shenzhou 7, Zhai Zhigang and Liu Boming completed China's first EVA. In 2011, China launched the Tiangong 1 target spacecraft and Shenzhou 8 uncrewed spacecraft. The two spacecraft completed China's first automatic rendezvous and docking on 3 November 2011. About 9 months later, Tiangong 1 completed the first manual rendezvous and docking with Shenzhou 9, which carried China's first female astronaut Liu Yang.
In September 2016, Tiangong 2 was launched into orbit. It was a space laboratory with more advanced functions and equipment than Tiangong 1. A month later, Shenzhou 11 was launched and docked with Tiangong 2. Two astronauts entered Tiangong 2 and were stationed for about 30 days, verifying the viability of astronauts' medium-term stay in space. In April 2017, China's first cargo spacecraft, Tianzhou 1 docked with Tiangong 2 and completed multiple in-orbit propellant refueling tests, which marked the successful completion of the second phase of CMS.
The third phase of CMS began in 2020. The goal of this phase is to build China's own space station, Tiangong. The first module of Tiangong, the Tianhe core module, was launched into orbit by China's most powerful rocket Long March 5B on 29 April 2021. It was later visited by multiple cargo and crewed spacecraft and demonstrated China's capability of sustaining Chinese astronauts' long-term stay in space.
According to CMS announcement, all missions of Tiangong Space Station are scheduled to be carried out by the end of 2022. Once the construction is completed, Tiangong will enter the application and development phase, which is poised to last for no less than 10 years.
Japan (NASDA) began the development of the HOPE-X experimental shuttle spaceplane in the 1980s, to be launched on its H-IIA expendable launch vehicle. A string of failures in 1998 led to funding reductions, and the project's cancellation in 2003 in favor of participation in the International Space Station program through the Kibō Japanese Experiment Module and H-II Transfer Vehicle cargo spacecraft. As an alternative to HOPE-X, NASDA in 2001 proposed the Fuji crew capsule for independent or ISS flights, but the project did not proceed to the contracting stage.
From 1993 to 1997, the , Kawasaki Heavy Industries, and Mitsubishi Heavy Industries worked on the proposed Kankoh-maru vertical-takeoff-and-landing single-stage-to-orbit reusable launch system. In 2005, this system was proposed for space tourism.
According to a press release from the Iraqi News Agency dated 5 December 1989, there was only one test of the Al-Abid space launcher, which Iraq intended to use to develop its own crewed space facilities by the end of the century. These plans were put to an end by the Gulf War of 1991 and the economic hardships that followed.
SpaceX has developed Crew Dragon flying on Falcon 9. It first launched astronauts to orbit and to the ISS in May 2020 as part of the Demo-2 mission. Developed as part of NASA's Commercial Crew Development program, the capsule is also available for flights with other customers. A first tourist mission, Inspiration4, launched in September 2021.
Boeing developed the Boeing Starliner capsule as part of NASA's Commercial Crew Development program, which is launched on a United Launch Alliance Atlas V launch vehicle. Starliner made an uncrewed flight in December 2019. A second uncrewed flight attempt was launched in May 2022. A crewed flight to fully certify Starliner was launched in June 2024. Similar to SpaceX, development funding has been provided by a mix of government and private capital funds.
Virgin Galactic is developing SpaceshipTwo, a commercial suborbital spacecraft aimed at the space tourism market. It reached space in December 2018.
Blue Origin is in a multi-year flight test program of their New Shepard vehicle and has carried out thirty one launches as of May 2025, including twenty uncrewed test flights and eleven crewed flights. The first crewed flight, carrying founder Jeff Bezos, his brother Mark Bezos, aviator Wally Funk, and 18-year old Oliver Daemen launched on July 20, 2021.
One large spaceliner concept currently in early development is the SpaceX Starship, which, in addition to replacing the Falcon 9 and Falcon Heavy in the legacy Earth-orbit market after 2020, has been proposed by SpaceX for long-distance commercial travel on Earth, flying 100+ people suborbitally between two points in under one hour, also known as "Earth-to-Earth". Starship Earth to Earth, SpaceX, 28 September 2017, accessed 23 December 2017.
Small spaceplane or small space capsule suborbital spacecraft have been under development for the past decade or so; , at least one of each type is under development. Both Virgin Galactic and Blue Origin have craft in active development: the SpaceShipTwo spaceplane and the New Shepard capsule, respectively. Both would carry approximately a half-dozen passengers up to space for a brief time of zero gravity before returning to the launch location. XCOR Aerospace had been developing the Lynx single-passenger spaceplane since the 2000s,(2012) SXC - Buying your tickets into space! SXC web page, Retrieved 5 April 2013 but development was halted in 2017.
Despite these developments, women are still underrepresented among astronauts and especially cosmonauts. More than 600 people have flown in space but only 75 have been women. Issues that block potential applicants from the programs, and limit the space missions they are able to go on, are, for example:
| + !Country !Citizen to space (Spaceflight) !Crewed spaceflight launch !Citizen to land on moon | |||
| Soviet Union | Yuri Gagarin, ( Vostok 1, 1961) | Vostok 1, 1961 ! | |
| United States | Alan Shepard, ( Freedom 7, 1961) | Freedom 7, 1961 | Neil Armstrong ( Apollo 11, 1969) |
| Vladimír Remek ( Soyuz 28, 1978) ! ! | |||
| Mirosław Hermaszewski ( Soyuz 30, 1978) ! ! | |||
| Sigmund Jähn ( Soyuz 31, 1978) ! ! | |||
| Georgi Ivanov ( Soyuz 33, 1979) ! ! | |||
| Bertalan Farkas ( Soyuz 36, 1980) ! ! | |||
| Phạm Tuân ( Soyuz 37, 1980) ! ! | |||
| Arnaldo Tamayo Méndez ( Soyuz 38, 1980) ! ! | |||
| Jügderdemidiin Gürragchaa ( Soyuz 39, 1981) ! ! | |||
| Dumitru Prunariu ( Soyuz 40, 1981) ! ! | |||
| Jean-Loup Chrétien ( Soyuz T-6, 1982) ! ! | |||
| Ulf Merbold ( STS-9, 1983) ! ! | |||
| Rakesh Sharma ( Soyuz T-11, 1984) ! ! | |||
| Marc Garneau ( STS-41-G, 1984) ! ! | |||
| Sultan Al-Saud ( STS-51-G, 1985) ! ! | |||
| Wubbo Ockels ( STS-61-A, 1985) ! ! | |||
| Rodolfo Neri Vela ( STS-61-B, 1985) ! ! | |||
| Muhammed Faris ( Soyuz TM-3, 1987) ! ! | |||
| Abdul Mohmand ( Soyuz TM-6, 1988) ! ! | |||
| Toyohiro Akiyama ( Soyuz TM-11, 1990) ! ! | |||
| Helen Sharman ( Soyuz TM-12, 1991) ! ! | |||
| Franz Viehböck ( Soyuz TM-13, 1991) ! ! | |||
| Klaus-Dietrich Flade ( Soyuz TM-14, 1992) ! ! | |||
| Aleksandr Kaleri ( Soyuz TM-14, 1992) | Soyuz TM-14, 1992 ! | ||
| Franco Malerba ( STS-46, 1992) ! ! | |||
| Claude Nicollier ( STS-46, 1992) ! ! | |||
| Talgat Musabayev ( Soyuz TM-19, 1994) ! ! | |||
| Leonid Kadeniuk ( STS-87, 1997) ! ! | |||
| Pedro Duque ( STS-95, 1998) ! ! | |||
| Ivan Bella ( Soyuz TM-29, 1999) ! ! | |||
| Mark Shuttleworth ( Soyuz TM-34, 2002) ! ! | |||
| Ilan Ramon ( STS-107, 2003) ! ! | |||
| Yang Liwei ( Shenzhou 5, 2003) | Shenzhou 5, 2003 ! | ||
| Marcos Pontes ( Soyuz TMA-8, 2006) ! ! | |||
| Christer Fuglesang ( STS-116, 2006) ! ! | |||
| Sheikh Muszaphar Shukor ( Soyuz TMA-11, 2007) ! ! | |||
| Yi So-Yeon ( Soyuz TMA-12, 2008) ! ! | |||
| Andreas Mogensen ( Soyuz TMA-18M, 2015) ! ! | |||
| Aidyn Aimbetov ( Soyuz TMA-18M, 2015) ! ! | |||
| Hazza Al Mansouri ( Soyuz MS-15, 2019) ! ! | |||
| Chris Boshuizen ( Blue Origin NS-18, 2021) ! ! | |||
| Mário Ferreira ( Blue Origin NS-22, 2022) ! ! | |||
| Sara Sabry ( Blue Origin NS-22, 2022) ! ! | |||
| Alper Gezeravcı ( Axiom Mission 3, 2024) ! ! | |||
| Marina Vasilevskaya ( Soyuz MS-25, 2024) ! ! | |||
Sally Ride became the first American woman in space, in 1983. Eileen Collins was the first female Shuttle pilot, and with Shuttle mission STS-93 in 1999 she became the first woman to command a U.S. spacecraft.
For many years, the USSR (later Russia) and the United States were the only countries whose astronauts flew in space. That ended with the 1978 flight of Vladimir Remek. , citizens from 38 nations (including space tourism) have flown in space aboard Soviet, American, Russian, and Chinese spacecraft.
The following space stations are currently maintained in Earth orbit for human occupation:
Most of the time, the only humans in space are those aboard the ISS, which generally has a crew of 7, and those aboard Tiangong, which generally has a crew of 3.
NASA and ESA use the term "human spaceflight" to refer to their programs of launching people into space. These endeavors have also formerly been referred to as "manned space missions", though this is no longer official parlance according to NASA style guides, which call for gender-neutral language.
Since 2008, the Japan Aerospace Exploration Agency had developed the H-II Transfer Vehicle cargo-spacecraft-based crewed spacecraft and Kibō Japanese Experiment Module–based small space laboratory.
NASA is developing a plan to land humans on Mars by the 2030s. The first step has begun with Artemis I in 2022, sending an uncrewed Orion spacecraft to a distant retrograde orbit around the Moon and returning it to Earth after a 25-day mission.
SpaceX is developing SpaceX Starship, a fully reusable two-stage system, with near-Earth and cislunar applications and an ultimate goal of landing on Mars. The upper stage of the Starship system, also called Starship, has had 9 atmospheric test flights as of September 2021. The first test flight of the fully integrated two-stage system occurred in April 2023. A Starship HLS of Starship is being developed for the Artemis program.
Several other countries and space agencies have announced and begun human spaceflight programs using natively developed equipment and technology, including Japan (JAXA), Iran (ISA), and North Korea (NADA). The plans for the Iranian crewed spacecraft are for a small spacecraft and space laboratory. North Korea's space program has plans for crewed spacecraft and small shuttle systems.
(1922–1991) | Soviet space program (OKB-1 Design Bureau) | космонавт (same word in:) kosmonavt cosmonaut Ғарышкер | Yuri Gagarin | 12 April 1961 | Vostok spacecraft | Vostok rocket | Orbital |
| NASA | astronaut spaceflight participant | Alan Shepard (suborbital) | 5 May 1961 | Mercury spacecraft | Redstone | Suborbital | |
| NASA | astronaut spaceflight participant | John Glenn (orbital) | 20 February 1962 | Mercury spacecraft | Atlas LV-3B | Orbital | |
| Space program of the People's Republic of China | — | 1973 (abandoned) | Shuguang | Long March 2A | Orbital | ||
| Space program of the People's Republic of China | — | 1981 (abandoned) | Piloted FSW | Long March 2 | Orbital | ||
| European Space Agency | CNES / European Space Agency (ESA) | spationaute astronaut | — | 1992 (abandoned) | Hermes | Ariane V | Orbital |
| Roscosmos | космонавт kosmonavt cosmonaut | Alexander Viktorenko, Alexander Kaleri | 17 March 1992 | Soyuz TM-14 to MIR | Soyuz-U2 | Orbital | |
| Ba'athist Iraq (1968–2003) | — | mallāḥ faḍāʼiy | — | 2001 (abandoned) | — | Tammouz rocket | |
| National Space Development Agency of Japan (NASDA) | or | — | 2003 (abandoned) | HOPE-X | H-II | Orbital | |
| China Manned Space Agency (CMSA) | taikonaut (p=tàikōng rén) | Yang Liwei | 15 October 2003 | Shenzhou spacecraft | Long March 2F | Orbital | |
| , Kawasaki Heavy Industries and Mitsubishi Heavy Industries | or | — | 2000s (abandoned) | Kankoh-maru | Kankoh-maru | Orbital | |
| JAXA | or | — | 2003 (abandoned) | Fuji | H-II | Orbital | |
| Indian Space Research Organisation (ISRO) | — | 2027 | Gaganyaan | LVM 3 | Orbital | ||
| European Space Agency | European Space Agency (ESA) | astronaut | — | 2020 (concept approved in 2009; but full development not begun) Apollo-like capsule chosen for Crew Space Transportation System, 22 May 2008 "Jules Verne" Automated Transfer Vehicle (ATV) Re-entry. Information Kit (PDF). Updated September 2008. European Space Agency. Retrieved on 7 August 2011. | CSTS, ARV phase-2 | Ariane V | Orbital |
| JAXA | or | — | TBD | HTV-based spacecraft | H3 | Orbital | |
| Iranian Space Agency (ISA) | — | — | 2019 (on hold) | ISA spacecraft | TBD | Orbital | |
| National Aerospace Development Administration (NADA) | — | — | 2020s | NADA spacecraft | Unha | Orbital | |
| Copenhagen Suborbitals | astronaut | — | 2020s | Tycho Brahe | SPICA | Suborbital |
The possibility of blindness and of Bone Loss have been associated with human space flight.
On 31 December 2012, a NASA-supported study reported that spaceflight may harm the brains of astronauts and accelerate the onset of Alzheimer's disease.
In October 2015, the NASA Office of Inspector General issued a health hazards report related to space exploration, which included the potential hazards of a human mission to Mars.
On 2 November 2017, scientists reported, based on MRI studies, that significant changes in the position and structure of the brain have been found in astronauts who have taken trips in space. Astronauts on longer space trips were affected by greater brain changes.
Researchers in 2018 reported, after detecting the presence on the International Space Station (ISS) of five Enterobacter bacterial strains, none to humans, that on ISS should be carefully monitored to assure a healthy environment for .
In March 2019, NASA reported that latent in humans may be activated during space missions, possibly adding more risk to astronauts in future deep-space missions.
On 25 September 2021, CNN reported that an alarm had sounded during the Inspiration4 Earth-orbital journey on the SpaceX Dragon 2. The alarm signal was found to be associated with an apparent toilet malfunction.
In a weightless environment, astronauts put almost no weight on the back or leg muscles used for standing up, which causes the muscles to weaken and get smaller. Astronauts can lose up to twenty per cent of their muscle mass on spaceflights lasting five to eleven days. The consequent loss of strength could be a serious problem in case of a landing emergency. Upon returning to Earth from long-duration flights, astronauts are considerably weakened and are not allowed to drive a car for twenty-one days.
Astronauts experiencing weightlessness will often lose their orientation, get motion sickness, and lose their sense of direction as their bodies try to get used to a weightless environment. When they get back to Earth, they have to readjust and may have problems standing up, focusing their gaze, walking, and turning. Importantly, those motor disturbances only get worse the longer the exposure to weightlessness. These changes can affect the ability to perform tasks required for approach and landing, docking, remote manipulation, and emergencies that may occur while landing.
In addition, after long space flight missions, male astronauts may experience severe visual system problems, which may be a major concern for future deep space flight missions, including a crewed mission to the planet Mars. News (CNN-TV, 02/09/2012) – Video (02:14) – Male Astronauts Return With Eye Problems. CNN (9 February 2012). Retrieved on 22 November 2016. Long space flights can also alter a space traveler's eye movements.
Another type of radiation, galactic , presents further challenges to human spaceflight beyond low Earth orbit.
There is also some scientific concern that extended spaceflight might slow down the body's ability to protect itself against diseases, resulting in a weakened immune system and the activation of dormant in the body. Radiation can cause both short- and long-term consequences to the bone marrow stem cells from which blood and immune-system cells are created. Because the interior of a spacecraft is so small, a weakened immune system and more active viruses in the body can lead to a fast spread of infection.
Due to these mental disorders, the efficiency of astronauts' work is impaired; and sometimes they are brought back to Earth, incurring the expense of their mission being aborted. A Russian expedition to space in 1976 was returned to Earth after the cosmonauts reported a strong odor that resulted in a fear of fluid leakage; but after a thorough investigation, it became clear that there was no leakage or technical malfunction. It was concluded by NASA that the cosmonauts most likely had Phantosmia.
It is possible that the mental health of astronauts can be affected by the changes in the sensory systems while in prolonged space travel.
Such a launch escape system is not always practical for multiple-crew-member vehicles (particularly ), depending on the location of egress hatch(es). When the single-hatch Vostok capsule was modified to become the 2 or 3-person Voskhod, the single-cosmonaut ejection seat could not be used, and no escape tower system was added. The two Voskhod flights in 1964 and 1965 avoided launch mishaps. The Space Shuttle carried ejection seats and escape hatches for its pilot and copilot in early flights; but these could not be used for passengers who sat below the flight deck on later flights, and so were discontinued.
There have been only two in-flight launch aborts of a crewed flight. The first occurred on Soyuz 18a on 5 April 1975. The abort occurred after the launch escape system had been jettisoned when the launch vehicle's spent second stage failed to separate before the third stage ignited and the vehicle strayed off course. The crew finally managed to separate the spacecraft, firing its engines to pull it away from the errant rocket, and both cosmonauts landed safely. The second occurred on 11 October 2018 with the launch of Soyuz MS-10. Again, both crew members survived.
In the first use of a launch escape system on the launchpad, before the start of a crewed flight, happened during the planned Soyuz T-10a launch on 26 September 1983, which was aborted by a launch vehicle fire 90 seconds before liftoff. Both cosmonauts aboard landed safely.
The only crew fatality during launch occurred on 28 January 1986, when the Space Shuttle Challenger broke apart 73 seconds after liftoff, due to the failure of a solid rocket booster seal, which caused the failure of the external fuel tank, resulting in an explosion of the fuel and separation of the boosters. All seven crew members were killed.
On 1 February 2003, the crew of seven aboard the were killed on reentry after completing a successful mission in space. A wing-leading-edge reinforced carbon-carbon heat shield had been damaged by a piece of frozen external tank foam insulation that had broken off and struck the wing during launch. Hot reentry gasses entered and destroyed the wing structure, leading to the breakup of the orbiter vehicle.
The use of a gas mixture carries the risk of decompression sickness (commonly known as "the bends") when transitioning to or from the pure oxygen space suit environment. There have been instances of injury and fatalities caused by suffocation in the presence of too much nitrogen and not enough oxygen.
A pure oxygen atmosphere carries the risk of fire. The original design of the Apollo spacecraft used pure oxygen at greater than atmospheric pressure prior to launch. An electrical fire started in the cabin of Apollo 1 during a ground test at Cape Kennedy Air Force Station Launch Complex 34 on 27 January 1967, and spread rapidly. The high pressure, increased by the fire, prevented removal of the plug door hatch cover in time to rescue the crew. All three astronauts—Gus Grissom, Ed White, and Roger Chaffee—were killed. This led NASA to use a nitrogen–oxygen atmosphere before launch, and low-pressure pure oxygen only in space.
The third lunar landing expedition, Apollo 13, in April 1970, was aborted and the lives of the crew—Jim Lovell, Jack Swigert, and Fred Haise—were threatened after the failure of a cryogenic liquid oxygen tank en route to the Moon. The tank burst when electrical power was applied to internal stirring fans in the tank, causing the immediate loss of all of its contents, and also damaging the second tank, causing the gradual loss of its remaining oxygen over a period of 130 minutes. This in turn caused a loss of electrical power provided by to the command spacecraft. The crew managed to return to Earth safely by using the lunar landing craft as a "life boat". The tank failure was determined to be caused by two mistakes: the tank's drain fitting had been damaged when it was dropped during factory testing, necessitating the use of its internal heaters to boil out the oxygen after a pre-launch test; which in turn damaged the fan wiring's electrical insulation because the thermostats on the heaters did not meet the required voltage rating due to a vendor miscommunication.
The crew of Soyuz 11 were killed on 30 June 1971 by a combination of mechanical malfunctions; the crew were due to cabin decompression following the separation of their descent capsule from the service module. A cabin ventilation valve had been jolted open at an altitude of by the stronger-than-expected shock of explosive separation bolts, which were designed to fire sequentially, but in fact had fired simultaneously. The loss of pressure became fatal within about 30 seconds.
| 27 January 1967 | Apollo 1 | Electrical fire in the cabin, spread quickly by pure oxygen atmosphere and flammable nylon materials in cabin and space suits, during pre-launch test; inability to remove plug door hatch cover due to internal pressure; rupture of cabin wall allowed outside air to enter, causing heavy smoke and soot | 3 | Cardiac arrest from carbon monoxide poisoning |
| 24 April 1967 | Soyuz 1 | Malfunction of primary landing parachute, and entanglement of reserve parachute; loss of 50% electrical power and spacecraft control problems necessitating emergency abort | 1 | Physical trauma from crash landing |
| 15 November 1967 | X-15 Flight 3-65-97 | The accident board found that the cockpit instrumentation had been functioning properly, and concluded that pilot Michael J. Adams had lost control of the X-15 as a result of a combination of distraction, misinterpretation of his instrumentation display, and possible vertigo. The electrical disturbance early in the flight degraded the overall effectiveness of the aircraft's control system and further added to pilot workload. | 1 | Vehicle breakup |
| 30 June 1971 | Soyuz 11 | Loss of cabin pressurization due to valve opening upon Orbital Module separation before re-entry | 3 | Asphyxia |
| 28 January 1986 | STS-51L Space Shuttle Challenger | Failure of O-ring inter-segment seal in one Solid Rocket Booster in extreme cold launch temperature, allowing hot gases to penetrate casing and burn through a strut connecting booster to the External Tank; tank failure; rapid combustion of fuel; orbiter breakup from abnormal aerodynamic forces | 7 | Asphyxia from cabin breach, or trauma from water impact |
| 1 February 2003 | STS-107 Space Shuttle Columbia | Damaged reinforced carbon-carbon heat shield panel on wing's leading edge, caused by a piece of External Tank foam insulation broken off during launch; penetration of hot atmospheric gases during re-entry, leading to structural failure of the wing, loss of control and disintegration of the orbiter | 7 | Asphyxia from cabin breach, trauma from dynamic load environment as orbiter broke up |
| 31 October 2014 | SpaceShipTwo VSS Enterprise powered drop-test | Copilot error: premature deployment of "feathering" descent air-braking system caused the disintegration of the vehicle in flight; pilot survived, copilot died | 1 | Physical trauma from crash |
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