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).^[3] However, in the United States, professional, military, and commercial astronauts who travel above an altitude of 80 kilometers (50 mi)^[4] are awarded astronaut wings.

As of November 14, 2008, a total of 489 humans from 38 countries^[5] have reached 100 km or more in altitude, of which 486 reached Low Earth orbit or beyond.^[6][7] 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 (Lovell, Young and Cernan).^[8]

Under the U. S. definition, 496 people qualify as having reached space (above 50 miles (80 km) altitude). Of eight X-15 pilots who reached 50 miles (80 km) or more in altitude, seven reached above 50 miles (80 km) but below 100 kilometers (about 62 miles).^[9] Space travelers have spent over 30,400 person-days (or a cumulative total of over 83 years) in space, including over 100 astronaut-days of spacewalks.^[9][10] As of 2008, the man with the longest time in space is Sergei K. Krikalev, who has spent 803 days, 9 hours and 39 minutes, or 2.2 years, in space.^[11][12] Peggy A. Whitson holds the record for most time in space by a woman, 377 days.^[13]

In the United States, Canada, United Kingdom, and many other English-speaking nations, a professional space traveler is called an astronaut.^[14] The term derives from the Greek words ástron (??????), meaning “star”, and nautes (??????), meaning “sailor”. The first known use of the term “astronaut” in the modern sense was by Neil R. Jones in his short story The Death’s Head Meteor in 1930. The word itself had been known earlier. For example, in Percy Greg’s 1880 book Across the Zodiac, “astronaut” referred to a spacecraft. In Les Navigateurs de l’Infini (1925) of J.-H. Rosny aîné, the word astronautique (astronautic) was used. The word may have been inspired by “aeronaut”, an older term for an air traveler first applied (in 1784) to balloonists.

NASA applies the term astronaut to any crew member aboard NASA spacecraft bound for Earth orbit or beyond. NASA also uses the term as a title for those selected to join its Astronaut Corps.^[15] The European Space Agency similarly uses the term astronaut for members of its Astronaut Corps.^[16]

With the rise of space tourism, NASA and the Russian Federal Space Agency agreed to use the term “spaceflight participant” to distinguish those space travelers from astronauts on missions coordinated by those two agencies.

July 10, 2009