Test Your Knowledge of Human Spaceflight

Human spaceflight has been conducted by the United States, Russia, and China, with the first human in space being Soviet cosmonaut Yuri Gagarin in 1961 and the first American being Alan Shepard in the same year. Humans have traveled to the Moon nine times between 1968 and 1972, and have had a continuous presence in space for 22 years and 181 days on the International Space Station (ISS). The United States, Russia, and China are the only countries with public or commercial human spaceflight-capable programs, while non-governmental spaceflight companies have been working to develop human space programs of their own. The first private human spaceflight launch was a suborbital flight on SpaceShipOne in 2004, and the first commercial orbital crew launch was by SpaceX in 2020. Human spaceflight capability was first developed during the Cold War between the United States and the Soviet Union, with the former launching Project Mercury and the latter launching the Vostok program. The two countries continued to compete rather than cooperate in space, with the US turning to developing the Space Shuttle and planning the space station, which was dubbed Freedom, while the USSR launched three Almaz military sortie stations from 1973 to 1977, followed by the development of Mir, the first modular, semi-permanent space station. Following the dissolution of the Soviet Union in 1991, the US and Russia cooperated in the Shuttle-Mir Program, which 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. The US and Russia also cooperated in converting the planned Space Station Freedom into the International Space Station (ISS), which was constructed beginning in 1998. China was the third nation to send humans into space, with its first crewed spaceflight mission, Shenzhou 5, launching in 2003. China developed the Shenzhou spacecraft and Long March 2F rocket dedicated to human spaceflight, and the goal of the second phase of China's Manned Space Program was to make technology breakthroughs in extravehicular activities (EVA, or spacewalk), space rendezvous, and docking to support short-term human activities in space. The third phase of China's Manned Space Program began in 2020, with the goal of building China's own space station, Tiangong.Human Spaceflight: A Summary

• The European Space Agency began development of the Hermes shuttle spaceplane in 1987, to be launched on the Ariane 5 expendable launch vehicle. The project was canceled in 1992.

• Japan began the development of the HOPE-X experimental shuttle spaceplane in the 1980s but the project was canceled in 2003.

• A number of private spaceflight ventures have been undertaken, including SpaceX, Virgin Galactic, Blue Origin, and Sierra Nevada, all of which plan to fly commercial passengers in the emerging space tourism market.

• SpaceX has developed Crew Dragon, which first launched astronauts to the ISS in May 2020.

• Boeing is developing the Starliner capsule as part of NASA's Commercial Crew Development program.

• Virgin Galactic is developing SpaceshipTwo, a commercial suborbital spacecraft aimed at the space tourism market.

• Blue Origin is in a multi-year test program of their New Shepard vehicle.

• Over the decades, a number of spacecraft have been proposed for spaceliner passenger travel.

• Participation and representation of humanity in space has been an issue ever since the first phase of space exploration.

• The first woman to ever enter space was Valentina Tereshkova. Women are still underrepresented among astronauts and cosmonauts.

• NASA is developing a plan to land humans on Mars by the 2030s.

• Planners of human spaceflight missions face a number of safety concerns, including environmental hazards, life support, medical issues, microgravity, and equipment malfunctions.Challenges and Risks of Human Spaceflight

• Astronauts experience physical and motor disturbances after prolonged exposure to weightlessness, which can affect their ability to perform tasks required for approach and landing, docking, remote manipulation, and emergencies.

• Male astronauts may experience severe eyesight problems after long spaceflight missions, which could be a significant concern for future deep space flight missions, including a crewed mission to Mars.

• Radiation exposure from solar particle events, galactic cosmic rays, and extended spaceflight may cause short- and long-term consequences to the bone marrow stem cells, resulting in a weakened immune system and the activation of dormant viruses in the body.

• Isolation and confinement during long missions may lead to depression, anxiety, cabin fever, and other psychological problems, impacting crew safety and mission success.

• Astronauts' sensory input weakens in an extreme environment, which could affect their ability to perform tasks.

• Space flight requires high energy density propellants for launch and the dissipation of large amounts of energy for safe reentry through the Earth's atmosphere, which carry inherent risks.

• Launch escape systems are employed to quickly carry the capsule away from the launch vehicle in case of fire or explosive destruction, but they are not always practical for multiple-crew-member vehicles.

• The risk of fire is high when using a pure oxygen atmosphere, and the risk of decompression sickness is high when transitioning to or from the pure oxygen space suit environment.

• Reliability issues can occur, such as an attitude control system thruster sticking in the on position, the failure of a cryogenic liquid oxygen tank en route to the Moon, and mechanical malfunctions leading to cabin decompression.

• As of December 2015, 23 crew members have died in accidents aboard spacecraft, and over 100 others have died in accidents during activities directly related to spaceflight or testing.