File:KSC-04-S-00398 (ksc 121504 vomit comet).webm

English: Affectionately called the 'vomit comet' by astronauts and also known as the 'weightless wonder,' NASA's KC-135 aircraft is retiring after many years of valuable service. NASA created the Reduced Gravity Program in 1959 and the KC-135 was later chosen as the perfect aircraft to better understand the role of gravity on humans and hardware in space. Reduced gravity is obtained with a specially modified aircraft, similar to the commercial Boeing 707 turbojet, flying steep climbs and dives that produce weightless periods. During a typical mission lasting two to three hours, the aircraft will make 30 to 40 climbs and dives, called parabolic arcs, providing periods of reduced gravity that last about 20 to 25 seconds. Weightlessness, though, can have a stomach-turning effect, even on the most seasoned astronaut -- hence the nickname, vomit comet. After about 34,000 ups and downs, the reliable KC-135 made its last flight in October 2004. A new Navy C-9 aircraft, designated as NASA 932, was chosen to take the place of the KC-135. After undergoing modification, it will be soar into service in 2005 as the next 'weightless wonder.'