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 aircraft gives its occupants the sensation of weightlessness by following an elliptic 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. There are 25 seconds of weightlessness out of 65 seconds of flight in each parabola. The airplane typically flies about 40–60 parabolic maneuvers. In about two thirds of the passengers, these flights produce nausea due to airsickness, giving the plane its nickname ‘vomit comet.
The Daily Omnivore 