An astronaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
In English-speaking nations, an astronaut is usually someone who is a professional outer space explorer.
While generally reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists. Starting in the 1950s up until 2002, astronauts were sponsored and trained exclusively by governments, either by the military or by civilian space agencies. With the sub-orbital flight of the privately funded SpaceShipOne in 2004, a new category of astronaut was created: the commercial astronaut.
The criteria for what constitutes human spaceflight vary. The Fédération Aéronautique Internationale (FAI) Sporting Code for astronautics recognizes only flights that exceed an altitude of 100 kilometers (62 mi). In the United States, professional, military, and commercial astronauts who travel above an altitude of 50 miles (80 km) are awarded astronaut wings. As of 8 June 2013, a total of 532 people from 36 countries have reached 100 km (62 mi) or more in altitude, of which 529 reached low Earth orbit or beyond. Of these, 24 people have traveled beyond Low Earth orbit, to either lunar or trans-lunar orbit or to the surface of the moon; three of the 24 did so twice: Jim Lovell, John Young and Eugene Cernan. The three astronauts who have not reached low Earth orbit are spaceplane pilots Joe Walker, Mike Melvill, and Brian Binnie. As of 20 June 2011, under the U.S. definition 538 people qualify as having reached space, above 50 miles (80 km) altitude. Of eight X-15 pilots who exceeded 50 miles (80 km) in altitude, only one exceeded 100 kilometers (about 62 miles). Space travelers have spent over 41,790 man-days (114.5 man-years) in space, including over 100 astronaut-days of spacewalks. As of 2008, the man with the longest cumulative time in space is Sergei K. Krikalev, who has spent 803 days, 9 hours and 39 minutes, or 2.2 years, in space. Peggy A. Whitson holds the record for the most time in space by a woman, 377 days.
Requirements and Criteria
NASA candidacy requirements
- Be citizens of the United States.
- Pass a strict physical examination, and have a near and distant visual acuity correctable to 20/20.
- Blood pressure, while sitting, must be no greater than 140 over 90.
Commander and Pilot
- A bachelor's degree in engineering, biological science, physical science or mathematics is required.
- At least 1,000 hours' flying time as pilot-in-command in jet aircraft. Experience as a test pilot is desirable.
- Height must be 5 ft 2 in to 6 ft 2 in (1.58 to 1.88 m).
- Distant visual acuity must be correctable to 20/20 in each eye.
- The refractive surgical procedures of the eye, PRK (Photorefractive keratectomy) and LASIK, are now allowed, providing at least 1 year has passed since the date of the procedure with no permanent adverse after effects. For those applicants under final consideration, an operative report on the surgical procedure will be requested.
- A bachelor's degree in engineering, biological science, physical science or mathematics, as well as at least three years of related professional experience (graduate work or studies) and an advanced degree, such as a master's degree (one to three years) or a doctoral degree (three years or more).
- Applicant's height must be between 4 ft. 10.5 in. and 6 ft. 4 in.