astronaut
Astronauts are people who fly. There are two main criteria for defining space flight: the United States recognizes space flights at altitudes of more than 50 mph, while the International Aviation Fleet is based on 100 km. Since April 1, 1961, Vostok 1 has been the first spacecraft in the Soviet Union to have returned to Earth, and as of April 3, 2010, a total of 38 countries 514 astronauts were flying in space, most of which were occupied by the United States and the Soviet Union / Russia. This number has risen to ballistic flights of more than 100 km, as well as Earth orbiting space, which is more than one-tenth of the Earth. Allan Sheppard, America's first astronaut who landed in the atmosphere, and rocket propulsion developed in the US in the 1960s X-15 pilots who are airplanes, and pilots at SpaceShip, a rocket-propelled plane developed by a US private company in 2004.