A reduced-gravity aircraft is a type of fixed-wing aircraft that provides brief near-weightless environments for training astronauts, conducting research and making gravity-free movie shots. Versions of such airplanes, officially nicknamed Weightless Wonders, were operated by the NASA Reduced Gravity Research Program. The unofficial nickname ‘vomit comet’ became popular among those who experienced their operation. The aircraft gives its occupants the sensation of weightlessness by following a parabolic flight path relative to the center of the Earth. While following this path, the aircraft and its payload are in free fall at certain points of its flight path. The aircraft is used in this way to demonstrate to astronauts what it is like to orbit the Earth. During this time the aircraft does not exert any ground reaction force on its contents, causing the sensation of weightlessness.
The Zero Gravity Plane