There was a need to acclimate astronauts in training to zero gravity. In 1950, the U.S.    Air Force recruited two German brothers, aeronautical engineer Fritz Haber and physicist Heinz Haber. They proposed simulating the microgravity in airplanes that would make parabolic flights in a wave-like configuration similar to a rollercoaster. In 1957, the Air Force began what would become NASA’s Reduced Gravity Program, training astronauts this way.

• During a typical flight, the plane flies out over the sea, climbing in a wave pattern of steep climbs and sharp dives. As it climbs up the parabola, or the top of the “hump,” passengers achieve several seconds of weightlessness at the peak. The plane then dives back toward the ground, pulling up to create the bottom of the wave. Passengers experience nearly twice the tug of Earth’s gravity from the midpoint on the way down, across the bottom and halfway back up.

• Adjusting the flight pattern can vary the pull of gravity and affect how long weightlessness lasts. Complete weightlessness lasts about 25 seconds. Passengers can experience different gravities, ranging from Martian gravity (about one-third of Earth’s gravity) which lasts about 30 seconds, or lunar gravity (one-sixth Earth’s gravity) which lasts about 40 seconds. This maneuver is typically repeated forty times during a two-hour flight, making up to one hundred parabolas on some flights.

• Because of the nature of the ride, many people become ill. Generally, one-third become violently ill, one-third become moderately ill, and one-third do not get sick at all. Thus, it has earned the name of the Vomit Comet.

In 1973, NASA took over the program from the Air Force. However, since 2008, a private company, Zero-G Corp., has handled the training. Although the program was designed for astronaut training, it’s open for use by other people as well.

• Celebrities such as director James Cameron, “Star Trek” actor George Takei, and Virgin Galactic’s billionaire founder, Sir Richard Branson, have all taken flights on Zero-G planes. In 2007, renowned physicist Stephen Hawking flew on G-Force One.   

• Actors in the movie “Apollo 13″    Tom Hanks, Kevin Bacon, and Bill Paxton, were probably the most famous visitors on the Vomit Comet in the 1990s. Set designers created a spacecraft interior adapted to the inside of the airplane, then the cameras captured shots on film, 25 seconds at a time. Director Ron Howard leased the aircraft over six months to achieve the weightless shots.

• Today you can book a ride on the Zero-G Experience now for $8200. Each ticket includes 15 parabolas, your own Zero-G flight suit, a “Regravitation Celebration,” a certificate of weightless completion, photos, and video of your unique experience.

• To avoid becoming ill, it’s recommended that you always try to stay right side up even if it is more fun to have your feet on the ceiling. Doing flips in mid-air is fun but will exacerbate the nausea. Try to lay down during the period of heavy gravity. You are also welcome to partake in motion sickness remedies, including either a pill or an injection of an intense version of Dramamine which slows the movement of fluid in the inner ear. Don’t make any quick motions while on the ground after taking these meds as it interferes with the sensation of movement.