Altitude Requirement
By one definition a sub-orbital spaceflight reaches an altitude higher than 100 km above sea level. This altitude, known as the Kármán line, was chosen by the Fédération Aéronautique Internationale because it is roughly the point where a vehicle flying fast enough to support itself with aerodynamic lift from the Earth's atmosphere would be flying faster than orbital speed. The US military and NASA award astronaut wings to those flying above 50 miles (80.47 km), although the US State Department appears to not support a distinct boundary between atmospheric flight and space flight.
Read more about this topic: Sub-orbital Spaceflight
Famous quotes containing the words altitude and/or requirement:
“On a level plain, simple mounds look like hills; and the insipid flatness of our present bourgeoisie is to be measured by the altitude of its “great intellects.””
—Karl Marx (1818–1883)
“The work of the political activist inevitably involves a certain tension between the requirement that positions be taken on current issues as they arise and the desire that one’s contributions will somehow survive the ravages of time.”
—Angela Davis (b. 1944)