Suborbital Travel
A sub-orbital spaceflight (or sub-orbital flight) is a spaceflight in which the spacecraft reaches space, but its path then crosses the atmosphere or surface of the gravitational body from which it was launched and does not enter a stable orbit. For example, any object launched from Earth that reaches 100 km (62 mi) above sea level, and then falls back to Earth, is considered a sub-orbital spaceflight. Some sub-orbital flights have been undertaken to test spacecraft and launch vehicles intended for later orbital spaceflight. Other vehicles are specifically designed only for sub-orbital flight; examples include manned vehicles such as the X-15 and SpaceShipOne, and unmanned ones such as ICBMs and sounding rockets. Sub-orbital spaceflights are distinct from flights that attain orbit but deorbit after less than one full orbital period. Thus neither the flights of the Fractional Orbital Bombardment System, nor Yuri Gagarin's flight aboard Vostok 1, are considered sub-orbital. Instead these are considered flights to low Earth orbit.
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