During this flight gravity varies from the magnitude of the earth’s gravitational pull to near weightlessness for a period of 20 to 30 seconds. The aircraft flies horizontally for a period of time only to rise in a steep climb followed by the 25 second freefall. Weightlessness approaching 3g can be achieved with the Vomit Comet. However, gravity is kept under 2g as a rule, as most astronauts pass out at this level of gravity.

The Vomit Comet received its name from the percentage of its passengers who throw up on its flights. According to John Yaniec, lead test director for NASA’s Reduced Gravity Program, roughly one third of its passengers vomit, one third get sick but don’t vomit, and the rest don’t get sick at all. According to Yaniec, most airsickness is caused by anxiety over the upcoming flight.

The Vomit Comet is used to train future astronauts as well as to carry out microgravity experiments. In addition, many high school and college science experiments have been carried out over the years on the Vomit Comet. One of the original KC-135 Vomit Comets was used to film scenes of the 1995 movie Apollo 13 starring Tom Hanks.