Human spaceflight
Human spaceflight is spaceflight with a crew or passengers aboard a spacecraft. Spacecraft carrying people may be operated directly, by human crew, or it may be either remotely operated from ground stations on Earth or be autonomous, able to carry out a specific mission with no human involvement.
The first human in space was Yuri Gagarin, who flew the Vostok 1 spacecraft, launched by the Soviet Union on 12 April 1961 as part of the Vostok program. Humans have flown to the Moon nine times from 1968 to 1972 in the United States Apollo program, and have been continuously present in space for on the International Space Station. All human spaceflight prior to Crew Dragon Demo-2 was human-piloted. The first autonomous human-carrying spacecraft was designed starting in 2015.
Russia and China have human spaceflight capability with the Soyuz program and Shenzhou program. In the United States, SpaceShipTwo reached the edge of space in 2018; this was the first crewed spaceflight from the US since the Space Shuttle retired in 2011. From 2011 to May 2020 expeditions to the International Space Station used Soyuz vehicles, which remain attached to the station to allow quick return if needed. The United States developed commercial crew transportation to facilitate domestic access to the ISS, low Earth orbit and beyond such as the Orion vehicle and the private SpaceX Starship. The first successful commercial launch from the United States was conducted in May 2020 aboard the SpaceX Crew Dragon spacecraft carrying NASA astronauts Robert Behnken and Douglas Hurley on their way to the International Space Station.
While spaceflight has typically been a government-directed activity, commercial spaceflight has gradually been taking on a greater role. The first private human spaceflight took place on 21 June 2004, when SpaceShipOne conducted a suborbital flight, and a number of non-governmental companies have been working to develop a space tourism industry. NASA has also played a role to stimulate private spaceflight through programs such as Commercial Orbital Transportation Services and Commercial Crew Development. With its 2011 budget proposals released in 2010, the Obama administration moved towards a model where commercial companies would supply NASA with transportation services of both people and cargo transport to low Earth orbit. The vehicles used for these services could then serve both NASA and potential commercial customers. Commercial resupply of ISS began two years after the retirement of the Shuttle, and commercial crew launches have operated since May 2020.
History
Cold War era
Human spaceflight capability was first developed during the Cold War between the United States and the Soviet Union, which developed the first intercontinental ballistic missile rockets to deliver nuclear weapons. These rockets were 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, the US worked on Project Mercury to launch men singly into orbit, while the USSR secretly pursued the Vostok program to accomplish the same thing. The USSR launched the first human in space, Yuri Gagarin, into a single orbit in Vostok 1 on a Vostok 3KA rocket, on 12 April 1961. The US launched its first astronaut, Alan Shepard, on a suborbital flight aboard Freedom 7 on a Mercury-Redstone rocket, on 5 May 1961. Unlike Gagarin, Shepard manually controlled his spacecraft's attitude, and landed inside it. The first American in orbit was John Glenn aboard Friendship 7, launched 20 February 1962 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. The US launched a total of two astronauts in suborbital flight and four into orbit through 1963. The US also made two flights in the North American X-15 piloted by Joseph A. Walker that exceeded the Kármán line, the internationally recognized 100 km altitude used by the FAI to denote the edge of space.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 by the end of the 1960s. The US started the three-man Apollo program in 1961 to accomplish this, launched by the Saturn family of launch vehicles, and the interim two-man Project Gemini in 1962, which flew 10 missions 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 in 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 into 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, made by Alexei Leonov on Voskhod 2 on 8 March 1965. But Voskhod did not have Gemini's capability to maneuver in orbit, and the program was terminated. The US Gemini flights did not accomplish the first spacewalk but overcame the early Soviet lead by performing several spacewalks and solving the problem of astronaut fatigue caused by overcoming the lack of gravity, demonstrating up to two weeks endurance in a human spaceflight, and the first space rendezvous and dockings 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 July 1969, Apollo 11 accomplished Kennedy's goal by landing Neil Armstrong and Buzz Aldrin on the Moon 21 July and returning them safely on 24 July along with Command Module pilot Michael Collins. A total of six Apollo missions landed 12 men to walk on the Moon through 1972, half of which drove electric powered vehicles on the surface. The crew of Apollo 13, Lovell, Jack Swigert, and Fred Haise, survived a catastrophic in-flight spacecraft failure and returned to Earth safely without landing on the Moon.
, first manned space station, with docked Soyuz spacecraft
Meanwhile, 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 the lunar programs in 1974. On 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.
After the Apollo program, the US launched the Skylab sortie space station in 1973, inhabiting it for 171 days with three crews aboard Apollo spacecraft. President Richard Nixon and Soviet Premier Leonid Brezhnev negotiated an easing of relations known as détente, an easing of Cold War tensions. As part of this, they negotiated the Apollo-Soyuz Test Project, in which an Apollo spacecraft carrying a special docking adapter module rendezvoused and docked with Soyuz 19 in 1975. The American and Russian crews shook hands in space, but the purpose of the flight was purely diplomatic and symbolic.
Nixon appointed his Vice President Spiro Agnew to head a Space Task Group in 1969 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 by 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 flyback 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.
, first manned orbital spaceplane
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, 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 a 51.6° inclination. 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 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. Twenty-two Shuttle flights carried a European Space Agency sortie space station called Spacelab in the payload bay from 1983 to 1998.
The USSR copied the reusable Space Shuttle orbiter, which it called Buran. It was designed to be launched into orbit by the expendable Energia rocket, and capable of robotic orbital flight and landing. Unlike the US Shuttle, Buran had no main rocket engines, but like the Shuttle used its orbital maneuvering engines to perform its final orbital insertion. A single uncrewed orbital test flight was successfully made in November 1988. A second test flight was planned by 1993, but the program was cancelled due to lack of funding and the dissolution of the Soviet Union in 1991. Two more orbiters were never completed, and the first one 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, now 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 inclination of 51.65°.
The Space Shuttle was retired in 2011 after 135 orbital flights, several of which helped assemble, supply, and crew the ISS. Columbia was destroyed in another accident during reentry, which killed 7 astronauts on 1 February 2003.
Russia has continued cooperation though half of the International Space Station is its sole singular half.
China
After Russia's launch of Sputnik 1 in 1957, Chairman Mao Zedong intended to place a Chinese satellite in orbit by 1959 to celebrate the 10th anniversary of the founding of the People's Republic of China, However, China did not successfully launch its first satellite until 24 April 1970. Mao and Premier Zhou Enlai decided on 14 July 1967, that the PRC should not be left behind, and started China's own human spaceflight program. The first attempt, the Shuguang spacecraft copied from the US Gemini, was cancelled on 13 May 1972.China later designed the Shenzhou spacecraft resembling the Russian Soyuz, and became the third nation to achieve independent human spaceflight capability by launching Yang Liwei on a 21-hour flight aboard Shenzhou 5 on 15 October 2003. China launched the Tiangong-1 space station on 29 September 2011, and two sortie missions to it: Shenzhou 9 16–29 June 2012, with China's first female astronaut Liu Yang; and Shenzhou 10, 13–26 June 2013. The station was retired on 21 March 2016 and reentered on 2 April 2018, burning up with smaller fragments impacting the ocean. Tiangong-1's successor Tiangong-2 was launched in September 2016 to then be derorbited in July 2019. Tiangong-2 hosted a crew of two for 26 days. The Tianzhou 1 cargo spacecraft docked to the station on 22 April 2017.
Abandoned programs of other nations
The European Space Agency began development in 1987 of the Hermes shuttle spaceplane, to be launched on the Ariane 5 expendable launch vehicle and to be docks with European Columbus space station. The projects were cancelled in 1992, when it became clear that neither cost nor performance goals could be achieved. No Hermes shuttles were ever built. Columbus space station reconfigured to same name European module in International Space Station.Japan began development in the 1980s of the HOPE-X experimental shuttle spaceplane, to be launched on its H-IIA expendable launch vehicle. A string of failures in 1998 led to funding reduction, and the project's cancellation in 2003 in favour of participation in International Space Station by Kibō Japanese Experiment Module and H-II Transfer Vehicle cargo spacecraft.
As alternative to HOPE-X NASDA in 2001 proposed Fuji manned capsuled spacecraft for independent or ISS flights but project was no adopted.
Earlier in 1993-1997, Kawasaki Heavy Industries and Mitsubishi Heavy Industries proposed Kankoh-maru proposed vertical takeoff and landing single-stage manned of cargo reusable launch system. Later in 2005 this system was proposed for space tourism.
According to a press-release of Iraqi News Agency of 5 December 1989 about the first test of the Tammouz space launcher, Iraq intended to develop 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 hard times that followed.
United States post-Space Shuttle gap
Under the Bush administration, the Constellation program included plans for retiring the Shuttle program and replacing it with the capability for spaceflight beyond low Earth orbit. In the 2011 United States federal budget, the Obama administration cancelled Constellation for being over budget and behind schedule while not innovating and investing in critical new technologies. As part of the Artemis program, NASA is developing the Orion spacecraft to be launched by the Space Launch System. Under the Commercial Crew Development plan, NASA will rely on transportation services provided by the private sector to reach low Earth orbit, such as SpaceX's Dragon 2, Sierra Nevada Corporation's Dream Chaser, or Boeing CST-100 Starliner. The period between the retirement of the Space Shuttle in 2011 and the first launch to space of SpaceShipTwo Flight VP-03 on 13 December 2018 is similar to the gap between the end of Apollo in 1975 and the first Space Shuttle flight in 1981, is referred to by a presidential Blue Ribbon Committee as the U.S. human spaceflight gap.SpaceX Dragon 2 launched on May 30, 2020 with a crew of 2 US astronauts, making it the first flight to the International Space Station from US soil since STS-135.
Commercial private spaceflight
Since the early 2000s, a variety of private spaceflight ventures have been undertaken. Several of the companies, including Blue Origin, SpaceX, Virgin Galactic, and Sierra Nevada have explicit plans to advance human spaceflight. , all four of those companies have development programs underway to fly commercial passengers.A commercial suborbital spacecraft aimed at the space tourism market is being developed by Virgin Galactic called SpaceshipTwo which reached space in December 2018.
Blue Origin has begun a multi-year test program of their New Shepard vehicle and carried out 11 successful uncrewed test flights in 2015–2019. Blue Origin planned to fly with humans in 2019.
SpaceX and Boeing are both developing passenger-capable orbital space capsules as of 2020, with SpaceX carrying NASA astronauts to the International Space Station onboard a Crew Dragon spacecraft launched on a Falcon 9 Block 5 launch vehicle. Boeing will be doing it with their CST-100 launched on a United Launch Alliance Atlas V launch vehicle.
Development funding for these orbital-capable technologies has been provided by a mix of government and private funds, with SpaceX providing a greater portion of total development funding for this human-carrying capability from private investment.
There have been no public announcements of commercial offerings for orbital flights from either company, although both companies are planning some flights with their own private, not NASA, astronauts on board.
Milestones
By achievement
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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, only the USSR and the United States had their own astronauts. Citizens of other nations flew in space, beginning with the flight of Vladimir Remek, a Czech, on a Soviet spacecraft on 2 March 1978, in the Interkosmos programme., citizens from 38 nations have flown in space aboard Soviet, American, Russian, and Chinese spacecraft.
Space programs
Human spaceflight programs have been conducted by the former Soviet Union and currently Russia, the United States, Mainland China, and by the American private spaceflight companies.Current programs
s are spacecraft used for transportation between the Earth's surface and outer space, or between locations in outer space. The following space vehicles and spaceports are currently used for launching human spaceflights:- Soyuz program : spacecraft on Soyuz launch vehicle, from Baikonur Cosmodrome; 140 crewed orbital flights since 1967, including two in-flight aborts which failed to reach orbit,
- Shenzhou program : spacecraft on Long March launch vehicle, from Jiuquan Satellite Launch Center; 5 flights since 2003,
- Spaceshiptwo : Air launched from White knight two carrier aircraft. 2 suborbital spaceflights since 2018, as of February 2019
- Crew Dragon : Part of the Commercial Crew Program, launched from Kennedy Space Center on a Falcon 9 rocket. One successful launch with more in the planning stages.
- International Space Station assembled in orbit: altitude, 51.65° inclination; crews transported by Soyuz spacecraft
Most of the time, the only humans in space are those aboard the ISS, whose crew of six spends up to six months at a time in low Earth orbit.
NASA and ESA use the term "human spaceflight" to refer to their programs of launching people into space. These endeavors have also been referred to as "manned space missions," though because of gender specificity this is no longer official parlance according to NASA style guides.
Planned future programs
Under the Indian Human Spaceflight Programme, India is planning to send humans into space on its orbital vehicle Gaganyaan before August 2022. The Indian Space Research Organisation began work on this project in 2006. The initial objective is to carry a crew of two or three to low Earth orbit for a 3 to 7 day flight in a spacecraft on a GSLV Mk III rocket and return them safely for a water landing at a predefined landing zone.On 15 August 2018, Indian Prime Minister Narendra Modi, from the rampart of the Red Fort in New Delhi, formally declared that India will independently send humans into space before the 75th anniversary of independence in 2022. In 2019, ISRO further revealed plans for a space station by 2030, followed by a crewed lunar mission. Activities are currently progressing with a focus on the development of critical technologies, infrastructure and subsystems such as the crew module, environmental control and life support system , crew escape system, etc. The department has initiated activities to study technical and managerial issues related to crewed missions. The program envisages the development of a fully autonomous orbital vehicle capable of carrying 2 or 3 crew members to an about low Earth orbit and bringing them safely back home. Development of space food and astronaut training is underway as of 2020, although the impact of the COVID-19 pandemic could delay the first mission by many months.
NASA is developing a plan to land humans on Mars by the 2030s. The first step will begin with Artemis 1 in 2021, sending an uncrewed Orion spacecraft to a distant retrograde orbit around the Moon and return it to Earth after a 25-day mission.
Several other countries and space agencies have announced and begun human spaceflight programs utilizing natively developed equipment and technology, including Japan, Iran and North Korea.
Since 2008 Japan Aerospace Exploration Agency developes H-II Transfer Vehicle cargo spacecraft based manned spacecraft and Kibō Japanese Experiment Module based small space laboratory.
Iranian manned spaceship project suggests small spacecraft and space laboratory. North Korea's space program has manned spacecraft and small shuttle system even as final aims.
Passenger travel via spacecraft
A number of spacecraft have been proposed over the decades that might facilitate spaceliner passenger travel. Somewhat analogous to travel by airliner after the middle of the 20th century, these vehicles are proposed to transport a large number of passengers to destinations in space, or to destinations on Earth which travel through space. To date, none of these concepts have been built, although a few vehicles that carry fewer than 10 persons are currently in the flight testing phase of their development process.One large spaceliner concept currently in early development is the SpaceX Starship which, in addition to replacing the Falcon 9 and Falcon Heavy launch vehicles in the legacy Earth-orbit market after 2020, has been proposed by SpaceX for long-distance commercial travel on Earth. This is to transport people on point-to-point suborbital flights between two points on Earth in under one hour, also known as "Earth-to-Earth," and carrying 100+ passengers.
Small spaceplane or small capsule suborbital spacecraft have been under development for the past decade or so and,, at least one of each type are under development. Both Virgin Galactic and Blue Origin are in active development, with 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 same location from where the trip began. XCOR Aerospace had been developing the Lynx single-passenger spaceplane since the 2000s but development was halted in 2017.
National spacefaring attempts
| Nation/Organization | Space agency | Term for space traveler | First launched astronaut | Date | Spacecraft | Launcher | Type |
| Soviet space program | космонавт kosmonavt cosmonaut Ғарышкер | Yuri Gagarin | 12 April 1961 | Vostok spacecraft | Vostok | Orbital | |
| National Aeronautics and Space Administration | astronaut spaceflight participant | Alan Shepard | 5 May 1961 | Mercury spacecraft | Redstone | Suborbital | |
| National Aeronautics and Space Administration | astronaut spaceflight participant | John Glenn | 20 February 1962 | Mercury spacecraft | Atlas LV-3B | Orbital | |
| Space program of the People's Republic of China | yǔhángyuán hángtiānyuán | ... | 1973 | Shuguang | Long March 2A | Orbital | |
| Space program of the People's Republic of China | yǔhángyuán hángtiānyuán | ... | 1981 | Piloted FSW | Long March 2 | Orbital | |
| European Space Agency | CNES / European Space Agency | spationaute astronaut | ... | 1992 | Hermes | Ariane V | Orbital |
| Russian Federal Space Agency | космонавт kosmonavt cosmonaut | Alexander Viktorenko, Alexander Kaleri | 17 March 1992 | Soyuz TM-14 to MIR | Soyuz-U2 | Orbital | |
 Ba'athist Iraq | ... | rajul faḍāʼ rāʼid faḍāʼ mallāḥ faḍāʼiy | ... | 2001 | ... | Tammouz 2 or 3 | |
| National Space Development Agency of Japan | uchūhikōshi or asutoronoto | ... | 2003 | HOPE | H-II | Orbital | |
| China National Space Administration | yǔhángyuán hángtiānyuán taikonaut | Yang Liwei | 15 October 2003 | Shenzhou spacecraft | Long March 2F | Orbital | |
| , Kawasaki Heavy Industries and Mitsubishi Heavy Industries | uchūhikōshi or asutoronoto | ... | 2000s | Kankoh-maru | Kankoh-maru | Orbital | |
| National Space Development Agency of Japan | uchūhikōshi or asutoronoto | ... | 2003 | Fuji | H-II | Orbital | |
| Indian Space Research Organisation | Vyomanaut | ... | 2022 | Gaganyaan | GSLV Mk III | Orbital | |
| European Space Agency | European Space Agency | astronaut | ... | 2020 | CSTS, ARV phase-2 | Ariane V | Orbital |
| Japan Aerospace Exploration Agency | uchūhikōshi or asutoronoto | ... | TBD | HTV-based spacecraft | H3 | Orbital | |
| Iranian Space Agency | ... | ... | 2019 | ISA spacecraft | TBD | Orbital | |
| National Aerospace Development Administration | ... | ... | 2020s | NADA spacecraft | Unha 9 | Orbital | |
| Copenhagen Suborbitals | astronaut | ... | 2020s | Tycho Brahe | SPICA | Suborbital | |
| ARCAspace | astronaut | ... | 2020s | IAR 111 | - | Suborbital |
Safety concerns
There are two main sources of hazard in space flight: those due to the environment of space which make it hostile to the human body, and the potential for mechanical malfunctions of the equipment required to accomplish space flight.Environmental hazards
Planners of human spaceflight missions face a number of safety concerns.Life support
The basic needs for breathable air and drinkable water are addressed by the life support system of the spacecraft.Medical issues
Medical consequences such as possible blindness and bone loss have been associated with human space flight.On 31 December 2012, a NASA-supported study reported that spaceflight may harm the brain 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, including a human mission to Mars.
On 2 November 2017, scientists reported that significant changes in the position and structure of the brain have been found in astronauts who have taken trips in space, based on MRI studies. Astronauts who took longer space trips were associated with greater brain changes.
Researchers in 2018 reported, after detecting the presence on the International Space Station of five Enterobacter bugandensis bacterial strains, none pathogenic to humans, that microorganisms on ISS should be carefully monitored to continue assuring a medically healthy environment for astronauts.
In March 2019, NASA reported that latent viruses in humans may be activated during space missions, adding possibly more risk to astronauts in future deep-space missions.
Microgravity
Medical data from astronauts in low Earth orbits for long periods, dating back to the 1970s, show several adverse effects of a microgravity environment: loss of bone density, decreased muscle strength and endurance, postural instability, and reductions in aerobic capacity. Over time these deconditioning effects can impair astronauts' performance or increase their risk of injury.In a weightless environment, astronauts put almost no weight on the back muscles or leg muscles used for standing up, which causes them 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 return 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, or any other mass with gravity, they have to readjust to the gravity and may have problems standing up, focusing their gaze, walking and turning. Importantly, those body motor disturbances after changing from different gravities only get worse the longer the exposure to little gravity. These changes will affect operational activities including approach and landing, docking, remote manipulation, and emergencies that may happen while landing. This can be a major roadblock to mission success.
In addition, after long space flight missions, male astronauts may experience severe eyesight problems. Such eyesight problems may be a major concern for future deep space flight missions, including a crewed mission to the planet Mars. Long space flights can also alter a space traveler's eye movements.
Radiation
Without proper shielding, the crews of missions beyond low Earth orbit might be at risk from high-energy protons emitted by solar flares and associated solar particle events. Lawrence Townsend of the University of Tennessee and others have studied the overall most powerful solar storm ever recorded. The flare was seen by the British astronomer Richard Carrington in September 1859. Radiation doses astronauts would receive from a Carrington-type storm could cause acute radiation sickness and possibly even death. Another storm that could have incurred a lethal radiation dose if astronauts were outside the Earth's protective magnetosphere occurred during the Space Age, in fact, shortly after Apollo 16 landed and before Apollo 17 launched. This solar storm of August 1972 would likely at least have caused acute illness.Another type of radiation, galactic cosmic rays, 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. Some of the problems are a weakened immune system and the activation of dormant viruses in the body. Radiation can cause both short and long term consequences to the bone marrow stem cells which create the blood and immune systems. 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.
Isolation
During long missions, astronauts are isolated and confined into small spaces. Depression, cabin fever and other psychological problems may impact the crew's safety and mission success.Astronauts may not be able to quickly return to Earth or receive medical supplies, equipment or personnel if a medical emergency occurs. The astronauts may have to rely for long periods on their limited existing resources and medical advice from the ground.
During astronauts' stay in space, they may experience mental disorders, more than for an average person. NASA spends millions of dollars on psychological treatments for astronauts and former astronauts. To date, there is no way to prevent or reduce mental problems caused by extended periods of stay in space.
Due to these mental disorders, the efficiency of their work is impaired and sometimes they are forced to send the astronauts back to Earth, which is very expensive. A Russian expedition to space in 1976 was returned to Earth after the cosmonauts reported a strong odor that caused 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 hallucinations of the smell, which brought many unnecessary wasted expenses.
It is possible that the mental health of astronauts can be affected by the changes in the sensory systems while in prolonged space travel.
Sensory systems
During astronauts' spaceflight, they are in a very extreme state where there is no gravity. This given state and the fact that no change is taking place in the environment will result in the weakening of sensory input to the astronauts in all seven senses.- Hearing - In the space station and spacecraft there are only mechanical noises. There can be no environmental noise; there is no medium that can transmit the sound waves. Although there are other team members who can talk to each other, their voices stop stimulating the sense of hearing, since they get used to it quickly.
- Sight - Because of the zero gravity, the body's liquids equalize in pressure throughout the body, a situation which is different from that on the Earth, where the pressures are not equal. Because of this reason, the astronauts' face swells and presses on the eyes, and therefore their vision is impaired. In addition, the landscape surrounding the astronauts is constant, which damages the visual stimulations. In addition, due to cosmic rays, astronauts may see flashes.
- Smell - The space station has a permanent odor described as the smell of gunpowder. Due to the zero gravity, the bodily fluids rise to the face and prevent the sinuses from drying up, which dulls the sense of smell.
- Taste - The sense of taste is directly affected by the sense of smell and therefore when the sense of smell is damaged, the sense of taste is also damaged. The astronauts' food is bland, and there are only certain foods that can be eaten. The food comes only once every few months when supplies arrive, and there is little to no variety.
- Touch – There are almost no physical contact changes. There is almost no human physical contact during the journey.
- The vestibular system - Due to the lack of gravity, all the movement of the astronauts changes, and the vestibular system is damaged by the extreme change.
- The proprioception system - As a result of the zero gravity, few forces are exerted on the astronauts' muscles and there is no input to this system.
Mechanical hazards
Launch
Since rockets carry the potential for fire or explosive destruction, space capsules generally employ some sort of launch escape system, consisting either of a tower-mounted solid-fuel rocket to quickly carry the capsule away from the launch vehicle, or else ejection seats to carry astronauts out of the capsule and away for individual parachute landing. The escape tower is discarded at some point before the launch is complete, at a point where an abort can be performed using the spacecraft's engines.Such a system is not always practical for multiple crew member vehicles, depending on location of egress hatch. 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 only been 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. The vehicle strayed off course, and the crew separated the spacecraft and fired its engines to pull it away from the errant rocket. 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 a crewed flight, the planned Soyuz T-10a launch on 26 September 1983 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 failure of a solid rocket booster seal which caused separation of the booster and failure of the external fuel tank, resulting in explosion of the fuel. All seven crew members were killed.
Spacewalking
Despite the ever-present risks related to mechanical failures while working in open space, no spacewalking astronaut has ever been lost. There is a requirement for spacewalking astronauts to use tethers and sometimes supplementary anchors. If those fail, a spacewalking astronaut would most probably float away according to relevant forces that were acting on him when breaking loose. Astronaut would possibly be spinning as kicking and flailing is of no use. At the right angle and velocity, he might even re-enter the Earth's atmosphere and burn away completely. NASA has protocols for such situations: astronauts would be wearing an emergency jetpack, which would automatically counter any tumbling to stabilize them. Then NASA's plan states that astronauts should take manual control and fly back to safety.However, if the pack's 3 pounds of fuel runs up, and if there is no other astronaut in close proximity to help, or if the air lock is irreparably damaged, the outcome would certainly be fatal. At the moment, there is no spacecraft to save an astronaut floating in space as the only one with a rescue-ready air-locked compartment — the Space Shuttle — retired years ago. There's approximately a litre of water available via straw in astronaut's helmet. He would wait roughly for 7.5 hours for breathable air to run out before dying of suffocation.
Reentry and landing
The single pilot of Soyuz 1, Vladimir Komarov was killed when his capsule's parachutes failed during an emergency landing on 24 April 1967, causing the capsule to crash.The crew of seven aboard the were killed on reentry after completing a successful mission in space on 1 February 2003. A wing leading edge reinforced carbon-carbon heat shield had been damaged by a piece of frozen external tank foam insulation which broke off and struck the wing during launch. Hot reentry gasses entered and destroyed the wing structure, leading to the breakup of the orbiter vehicle.
Artificial atmosphere
There are two basic choices for an artificial atmosphere: either an Earth-like mixture of oxygen in an inert gas such as nitrogen or helium, or pure oxygen, which can be used at lower than standard atmospheric pressure. A nitrogen-oxygen mixture is used in the International Space Station and Soyuz spacecraft, while low-pressure pure oxygen is commonly used in space suits for extravehicular activity.The use of a gas mixture carries the risk of decompression sickness when transitioning to or from the pure oxygen space suit environment. There have also been instances of injury and fatalities caused by suffocation in the presence of too much nitrogen and not enough oxygen.
- In 1960, McDonnell Aircraft test pilot G.B. North passed out and was seriously injured when testing a Mercury cabin/spacesuit atmosphere system in a vacuum chamber, due to nitrogen-rich air leaking from the cabin into his spacesuit feed. This incident led NASA to decide on a pure oxygen atmosphere for the Mercury, Gemini, and Apollo spacecraft.
- In 1981, three pad workers were killed by a nitrogen-rich atmosphere in the aft engine compartment of the at the Kennedy Space Center Launch Complex 39.
- In 1995, two pad workers were similarly killed by a nitrogen leak in a confined area of the Ariane 5 launch pad at Guiana Space Centre.
Reliability
The March 1966 Gemini 8 mission was aborted in orbit when an attitude control system thruster stuck in the on position, sending the craft into a dangerous spin which threatened the lives of Neil Armstrong and David Scott. Armstrong had to shut the control system off and use the reentry control system to stop the spin. The craft made an emergency reentry and the astronauts landed safely. The most probable cause was determined to be an electrical short due to a static electricity discharge, which caused the thruster to remain powered even when switched off. The control system was modified to put each thruster on its own isolated circuit.The third lunar landing expedition Apollo 13 in April 1970, was aborted and the lives of the crew, James Lovell, Jack Swigert and Fred Haise, were threatened by 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 loss of its remaining oxygen in a span of 130 minutes. This in turn caused loss of electrical power provided by fuel cells 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. This necessitated 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: they were asphyxiated due to cabin decompression following 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.
Fatality risk
, 23 crew members have died in accidents aboard spacecraft. Over 100 others have died in accidents during activity directly related to spaceflight or testing.| Date | Mission | Accident cause | Deaths | Cause of death |
| 27 January 1967 | Apollo 1 | Electrical fire in 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 |
| 15 November 1967 | X-15 Flight 3-65-97 | The accident board found that the cockpit instrumentation had been functioning properly, and concluded that 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 |
| 24 April 1967 | Soyuz 1 | Malfunction of primary landing parachute, and entanglement of reserve parachute; loss of 50% electrical power and spacecraft control problems necessitated emergency abort | 1 | Trauma from crash landing |
| 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 piece of External Tank foam insulation broken off during launch; penetration of hot atmospheric gases during re-entry, leading to structural failure of wing, loss of control and disintegration of 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 disintegration of vehicle in flight; pilot survived, copilot died | 1 | Trauma from crash |
Human representation and participation
Women
The first woman to ever enter space was Valentina Tereshkova. She flew in 1963 but it was not until the 1980s that another woman entered space again. All astronauts were required to be military test pilots at the time and women were not able to enter this career, this is one reason for the delay in allowing women to join space crews. After the rule changed, Svetlana Savitskaya became the second woman to enter space, she was also from the Soviet Union. Sally Ride became the next woman to enter space and the first woman to enter space through the United States program.Since then, eleven other countries have allowed women astronauts. Due to some slow changes in the space programs to allow women.
The first all female space walk occurred in 2018, including Christina Koch and Jessica Meir. These two women have both participated in separate space walks with NASA. The first woman to go to the moon is planned for 2024.
Despite these developments women are still underrepresented among astronauts and especially cosmonauts. Issues that block potential applicants from the programs and limit the space missions they are able to go on, are for example:
- agencies limiting women to half as much time in space than men, argueing with unresearched potential risks for cancer.
- a lack of space suits sized appropriately for female astronauts.