Vomit Comet
A Reduced Gravity Aircraft is a type of fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 that briefly provides a nearly weightless environment in which to train astronaut
An astronaut or cosmonaut is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft....

s, conduct research and film motion pictures.
Versions of such airplanes have in the past been operated by NASA Reduced Gravity Research Program, where the unofficial nickname originated. NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 has adopted the official nickname Weightless Wonder for publication.

Operating principles

The aircraft gives its occupants the sensation of weightlessness by following an (approximately parabolic) elliptic
In geometry, an ellipse is a plane curve that results from the intersection of a cone by a plane in a way that produces a closed curve. Circles are special cases of ellipses, obtained when the cutting plane is orthogonal to the cone's axis...

 flight path relative to the center of the Earth. While following this path, the aircraft and its payload are in free fall
Free fall
Free fall is any motion of a body where gravity is the only force acting upon it, at least initially. These conditions produce an inertial trajectory so long as gravity remains the only force. Since this definition does not specify velocity, it also applies to objects initially moving upward...

 at certain points of its flight path. The aircraft is used in this way to demonstrate to astronauts what it is like to orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...

 the Earth. During this time the aircraft does not exert any ground reaction force
Ground reaction force
In physics, and in particular in biomechanics, the ground reaction force is the force exerted by the ground on a body in contact with it.For example, a person standing on the ground exerts a contact force on it and at the same time an equal and opposite ground reaction force is exerted by the...

 on its contents, causing the sensation of weightlessness.

Initially the aircraft climbs with a pitch angle of 45 degrees. The sensation of weightlessness is achieved by reducing thrust and lowering the nose to maintain a zero-lift angle of attack
Angle of attack
Angle of attack is a term used in fluid dynamics to describe the angle between a reference line on a lifting body and the vector representing the relative motion between the lifting body and the fluid through which it is moving...

. 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 is pointed downward at high speed, and must begin to pull back into the nose-up attitude to repeat the maneuver. 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.

This aircraft is used to train astronauts in zero-g maneuvers, giving them about 25 seconds of weightlessness out of 65 seconds of flight in each parabola. In about two thirds of cases, this motion produces nausea
Nausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...

 due to airsickness
Airsickness is a sensation which is induced by air travel. It is a specific form of motion sickness, and is considered a normal response in healthy individuals...

, especially in novices, giving the plane its nickname.

Usage by NASA

NASA has flown zero-g flights on various aircraft for many years. In 1959, Project Mercury
Project Mercury
In January 1960 NASA awarded Western Electric Company a contract for the Mercury tracking network. The value of the contract was over $33 million. Also in January, McDonnell delivered the first production-type Mercury spacecraft, less than a year after award of the formal contract. On February 12,...

 astronauts trained in a C-131 Samaritan
C-131 Samaritan
The Convair C-131 Samaritan was an American military transport produced from 1954 to 1956. It is the military version of the Convair CV-240.-Design and development:...

 aircraft, which was dubbed the "Vomit Comet".

Twin KC-135 Stratotanker
KC-135 Stratotanker
The Boeing KC-135 Stratotanker is an aerial refueling military aircraft. It and the Boeing 707 airliner were developed from the Boeing 367-80 prototype. The KC-135 was the US Air Force's first jet-powered refueling tanker and replaced the KC-97 Stratotanker...

s were used until December 2004 but have since been retired. One, a KC-135A known as NASA 930, was also used by Universal Pictures
Universal Pictures
-1920:* White Youth* The Flaming Disc* Am I Dreaming?* The Dragon's Net* The Adorable Savage* Putting It Over* The Line Runners-1921:* The Fire Eater* A Battle of Wits* Dream Girl* The Millionaire...

 and Imagine Entertainment
Imagine Entertainment
Imagine Entertainment is a film and television production company founded in 1986 by director Ron Howard and producer Brian Grazer.Its productions include the television series 24 and Arrested Development and the films Apollo 13 , A Beautiful Mind and The Da Vinci Code .-Organization:Karen...

 for filming scenes involving weightlessness in the movie Apollo 13
Apollo 13 (film)
Apollo 13 is a 1995 American drama film directed by Ron Howard. The film stars Tom Hanks, Kevin Bacon, Bill Paxton, Gary Sinise, Kathleen Quinlan and Ed Harris. The screenplay by William Broyles, Jr...

; that aircraft was retired in 2000 and is now on display at Ellington Field
Ellington Field
Ellington International Airport is a joint civil-military airport located in the U.S. state of Texas within the city of Houston— southeast of Downtown. Established by the Army Air Service on 21 May 1917, Ellington Field was one of the initial World War I Army Air Service installations when...

, near the Johnson Space Center. The KC-135A 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
Pima Air & Space Museum
The Pima Air & Space Museum features a display of nearly 300 aircraft spread out over 80 acres on a campus occupying 127 acres . Located in Tucson, Arizona, it is one of the world's largest, non-government funded aerospace museums...

 in Tucson, Arizona.

In 2005, NASA replaced the aircraft with a McDonnell Douglas
McDonnell Douglas
McDonnell Douglas was a major American aerospace manufacturer and defense contractor, producing a number of famous commercial and military aircraft. It formed from a merger of McDonnell Aircraft and Douglas Aircraft in 1967. McDonnell Douglas was based at Lambert-St. Louis International Airport...

 C-9B Skytrain II that was formerly owned by KLM Royal Dutch Airlines and the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...



The Italian Space Agency
Italian Space Agency
The Italian Space Agency is a government agency established in 1988 to fund, regulate and coordinate space exploration activities in Italy...

 contracts SpaceLand, an Italian parabolic flight and sub-orbital flight engineering and operational agency to support research, development and educational flight campaigns.


The Canadian Space Agency and the National Research Council have a Falcon 20 used for microgravity research. The small plane is normally not used for people to float freely and experience weightlessness, however comedian Rick Mercer
Rick Mercer
Richard Vincent "Rick" Mercer is a Canadian comedian, television personality, political satirist, and blogger.Mercer first came to national attention in 1990, when he premiered his one man show Show Me the Button, I'll Push It, or Charles Lynch Must Die at the Great Canadian Theatre Company in...

 did so for a segment on his show
Rick Mercer Report
Rick Mercer Report is a Canadian television comedy series which airs on CBC Television...



The first zero G plane to enter service in Latin America is a T-39 Sabreliner nicknamed CONDOR. CONDOR has been in operation for the Ecuadorian Civilian Space Agency
Ecuadorian Civilian Space Agency
The Ecuadorian Civilian Space Agency is the organization in charge of administering and executing the Ecuadorian civilian space program and conducting scientific research on space and planetary sciences. It is a mixed capital non-profit organization, 50% civilian and 50% Ecuadorian government...

 and the Ecuadorian Air Force
Ecuadorian Air Force
The Ecuadorian Air Force is the Air arm of the Military of Ecuador and responsible for the protection of the Ecuadorian airspace.-Mission:To develop the military air wing, in order to execute institutional objectives which guarantee sovereignty and contribute towards the nation's security and...

 since May, 2008. 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.


Since 1984, the ESA
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...

 and the CNES
The is the French government space agency . Established under President Charles de Gaulle in 1961, its headquarters are located in central Paris and it is under the supervision of the French Ministries of Defence and Research...

 flew similar reduced-gravity missions in a variety of aircraft, including NASA's KC-135, a Caravelle
Sud Aviation Caravelle
The Sud Aviation SE 210 Caravelle was the first short/medium-range jet airliner produced by the French Sud Aviation firm starting in 1955 . The Caravelle was one of the more successful European first generation jetliners, selling throughout Europe and even penetrating the United States market, with...

, an Ilyushin IL-76 MDK
Ilyushin Il-76
The Ilyushin Il-76 is a multi-purpose four-engined strategic airlifter designed by Ilyushin design bureau. It was first planned as a commercial freighter in 1967. Intended as a replacement for the Antonov An-12, the Il-76 was designed for delivering heavy machinery to remote, poorly-serviced areas...

, and, most recently, an Airbus A300
Airbus A300
The Airbus A300 is a short- to medium-range widebody jet airliner. Launched in 1972 as the world's first twin-engined widebody, it was the first product of Airbus Industrie, a consortium of European aerospace companies, wholly owned today by EADS...

 known as the Zero-G, which is flown out of the Bordeaux-Mérignac airport
Aéroport de Bordeaux Mérignac
-Ground transport:The airport is accessible by :*Road: Rocade 11b*Public transport:**Jet'Bus shuttle serving the Bordeaux Saint-Jean railway station**Bus line 1 serving the city centre....

 in France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

. Since 1997, CNES subsidiary Novespace has handled the management of these flights.


In Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, commercial flights are offered on the Ilyushin Il-76
Ilyushin Il-76
The Ilyushin Il-76 is a multi-purpose four-engined strategic airlifter designed by Ilyushin design bureau. It was first planned as a commercial freighter in 1967. Intended as a replacement for the Antonov An-12, the Il-76 was designed for delivering heavy machinery to remote, poorly-serviced areas...

 jet; several U.S. companies book flights on these jets. 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.

United States

In late 2004, the Zero Gravity Corporation
Zero Gravity Corporation
Zero Gravity Corporation is an American company based in Vienna, Virginia, formerly of Fort Lauderdale, Florida, which operates weightless flights from United States airports...

 became the first company in the United States to offer zero-g flights to the general public, using Boeing 727
Boeing 727
The Boeing 727 is a mid-size, narrow-body, three-engine, T-tailed commercial jet airliner, manufactured by Boeing. The Boeing 727 first flew in 1963, and for over a decade more were built per year than any other jet airliner. When production ended in 1984 a total of 1,832 aircraft had been produced...

 jets. Each flight consists of around 15 parabolas, including simulations of the gravity levels of the moon and Mars, as well as complete weightlessness.
There is also a company in Oldsmar, Florida
Oldsmar, Florida
Oldsmar is a city in Pinellas County, Florida, United States. The population was 11,910 at the 2000 census. The U.S. Census Bureau estimates the population to be 13,401 as of 2008....

 called Aurora Aerospace that also offers zero-g flights using a Fuji/Rockwell Commander 700
Fuji/Rockwell Commander 700
|-See also:-References:* The Illustrated Encyclopedia of Aircraft , 1985, Orbis Publishing, Page 1920-External links:...

. It is also used to simulate the gravity of the moon and Mars.


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

Further reading

  • 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.

External links

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