An astronaut, cosmonaut (Russian: космона́вт), spationaut (French) or taikonaut (Chinese: 太空人; pinyin: tàikōng rén) is a person who travels into space, or who makes a career of doing so.
The criteria for determining who has achieved human spaceflight vary. In the United States, people who travel above an altitude of 80 kilometres (50 miles) are designated as astronauts. The FAI defines spaceflight as over 100 kilometres (62 miles). As of June 20, 2011, a total of 654 humans have reached space according to the U.S. definition, 529 people qualify under the FAI definition, while 444 people have reached Earth orbit or beyond. 24 astronauts have completely left the Earth’s Orbit. These individuals have spent over 29,000 crew-days (or a cumulative total of over 77 years) in space including over 100 crew-days of spacewalks. Astronauts from at least 35 countries have gone into space. The U.S. awards astronaut wings to those who fly into space on their rockets.
The first astronauts, both in the U.S. and USSR, tended to be jet fighter pilots, often test pilots, from military backgrounds. U.S. astronauts receive a special qualification badge, known as the Astronaut Badge upon completion of Astronaut training and participation in a space flight.
Astronauts may train for extra-vehicular activity in a facility such as NASA’s Neutral Buoyancy Laboratory. Astronauts-in-training may also experience short periods of weightlessness in aircraft such as the “vomit comet”, a modified KC-135 which performs parabolic flights. Astronauts are also required to accrue a number of flight hours in high-performance jet aircraft. This is mostly done in T-38 jet aircraft out of Ellington Field, due to its proximity to the Johnson Space Center. Ellington Field is also where the Shuttle Training Aircraft is maintained and developed, although most flights of the aircraft are done out of Edwards Air Force Base.
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