The "Vomit Comet" refers to a NASA program that introduces astronauts to the feeling of zero-gravity spaceflight. Recruits climb aboard a specially fitted aircraft that dips and climbs through the air to simulate the feeling of weightlessness in 20- to 25-second intervals.

The downside? The sudden changes make a lot of astronauts feel ill. Very, very ill. Hence the tongue-in-cheek nickname.

According to NASA, its "reduced gravity" research program started in 1959. NASA has flown several types of aircraft over the years, perhaps most famously the KC-135A aircraft that is now retired.

The actors of the movie "Apollo 13" — Tom Hanks, Kevin Bacon and Bill Paxton — were the most famous visitors on the KC-135A parabola flights in the 1990s.

Set designers created a spacecraft interior adapted to the inside of the airplane, then the cameras captured shots on film (in less than 30 seconds of acting at a time). Director Ron Howard leased the aircraft over six months to achieve the weightless shots viewers see in the film.

NASA currently offers flight opportunities on the Boeing 727-200F operated by Zero G Corp. Zero G Corp also offers opportunities for tourists to take a ride. Be prepared to save for a while, tickets are more than $5,000 a person.

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