Vomit Comet

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Vomit Comet is a nickname for any fixed-wing aircraft that briefly provides a nearly weightless environment in which to train astronauts, conduct research, and film motion pictures. Versions of such airplanes have in the past been operated by NASA Reduced Gravity Research Program,^[1] where the unofficial nickname originated. NASA has adopted the official nickname Weightless Wonder for publication.^[2]

Contents 1 Operating principles 2 Usage by NASA 3 Outside of NASA 3.1 United States 3.2 Europe 3.3 Russia 3.4 Ecuador 4 Airsickness 5 See also 6 Notes 7 References 8 External links

[edit] Operating principles

The aircraft achieves weightlessness by following an elliptic flight path relative to the center of the Earth.^[3] While following this path, the aircraft and its payload are in free fall and are literally orbiting the earth. During this time the aircraft does not exert any g-forces on its contents.

The trajectory of this flight path is almost always ambiguously described as "parabolic" without providing a frame of reference. To an observer on the non-inertial surface of the Earth the exact shape of the flight path would be complex due the centrifugal force, Coriolis effect, and Eötvös effect. However, if the aircraft were capable of reaching escape velocity, the path would be a parabola, and the experience of weightlessness would last forever.

The graph of the aircraft's altitude as a function of time is a cycloid.^[4]

Initially the aircraft climbs with a pitch angle of 45 degrees. Weightlessness is achieved by reducing thrust and lowering the nose to maintain a zero angle of attack. Weightlessness begins while ascending and lasts all the way "up-and-over the hump", until the craft reaches a declined angle of 30 degrees. At this point, the craft has lost a significant amount of altitude, and must begin to pull into a climb. The forces are then roughly twice that of gravity on the way down, at the bottom, and up again. This lasts all the way until the aircraft is again halfway up its upward trajectory, and the pilot again initiates the zero-g flight path.^[5]

In general, this aircraft is used to train astronauts in zero-g maneuvers, giving them about 25 seconds of weightlessness out of 65 seconds of flight. This often produces nausea due to airsickness, especially in novices, giving the plane its nickname.

[edit] Usage by NASA

NASA has flown zero-g flights on various aircraft for many years. In 1959, Project Mercury astronauts trained in a C-131 Samaritan aircraft, which was dubbed the "Vomit Comet".^[6]

Twin KC-135 Stratotankers were used until December 2004 and have since been retired. One, a KC-135A known as NASA 930, was also used by Universal Pictures and Imagine Entertainment for filming scenes involving weightlessness in the movie Apollo 13; that aircraft was retired in 2000 and is now on display at Ellington Field, near the Johnson Space Center. It is estimated to have flown over 58,000 parabolas. The other (N931NA or NASA 931) made its final flight on October 29, 2004, and is permanently stored in the Pima Air & Space Museum in Tucson, Arizona.

In 2005, NASA replaced the aircraft with a McDonnell Douglas C-9B Skytrain II that was formerly owned by KLM Royal Dutch Airlines and the United States Navy [1].

[edit] Outside of NASA

[edit] United States

In late 2004, Zero Gravity Corporation became the first and only company in the United States to offer zero-g flights to the general public, using Boeing 727 jets. Each flight consists of around 15 parabolas, including simulations of the gravity levels of the Moon and Mars, as well as complete weightlessness.^[7]

[edit] Europe

Since 1984, the ESA and the CNES have flown similar reduced-gravity missions in a variety of aircraft, including NASA's KC-135, a Caravelle, an Ilyushin IL-76 MDK, and, most recently, an Airbus A300 known as the Zero-G, which is flown out of the Bordeaux-Mérignac airport in France.^[8] Since 1997, CNES subsidiary Novespace has handled the management of these flights.^[9]

[edit] Russia

In Russia, commercial flights are offered on the Ilyushin Il-76 jet; several U.S. companies book flights on these jets.^[10] The 1999 pornographic film The Uranus Experiment 1 had scenes filmed on such an aircraft; it is notable for containing the first instance of zero-gravity sex caught on film.^[11]

[edit] Ecuador

The first zero G plane in Latin America is a T-39 Sabreliner nicknamed CONDOR, operated by the Ecuadorian space agency and the Ecuadorian Air Force. It has operated since May, 2008.^[12] On June 19 2008, this plane carried 7 year old Jules Nader as he set the Guinness world record for the youngest human being to fly in microgravity. Nader worked on a hydrodynamics experiment designed by his brother.^[13]

[edit] Airsickness

According to former Reduced Gravity Research Program director John Yaniec, anxiety contributes most to passengers' airsickness. Yaniec gives a rough estimate that of passengers, "one third [become] violently ill, the next third moderately ill, and the final third not at all." Vomiting is referred to as a "kill".^[14]

Commercial operator Zero Gravity Corporation claims their tourist rides with up to 15 parabolas are much less traumatic compared to the typical research flight with 40–80 parabolas.^[15]

[edit] See also

• Microgravity
• Space tourism

[edit] Notes

[edit] References

• Haber, Fritz and Haber, Heinz: "Possible Methods of Producing the Gravity-Free State for Medical Research", Journal of Aviation Medicine XXI (1950)
• Easton, Pam (October 30, 2004). NASA's weightless aircraft is retired. Associated Press.
• Golightly, Glen (May 15, 2000). Vomit Comet finds a home. Space.com Houston Bureau.
• Overbye, Dennis (March 1, 2007), "Stephen Hawking plans prelude to the ride of his life", New York Times

[edit] External links

• Reduced Gravity Research Program
• Interview with John Yaniec
• About the NASA Reduced Gravity Research Program
• ATLAS aerospace is a Russian company that offers reduced gravity flights in an IL-76 MDK wide-body aircraft.
• Virtual tour of the Airbus A-300 Zero-G
• C-135 Variants Part 6 - includes scale drawing of NASA 930
• Reduced Gravity Experiment in a Nasa´s KC-135A