Weightlessness inside the Vomit Comet
Vomit Comet is a nickname for any airplane 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's Reduced Gravity Research
Program since 1973, where the nickname originated. NASA prefers the nickname Weightless Wonder for public relations
reasons.
Operating principles
-
The airplane produces weightlessness by following a parabolic vertical flight path. A
parabolic flight path is the same path that would be taken by an object in free fall, such as
a cannonball fired into the air. As a result, the aircraft does not exert any G force on its
contents, so the contents have zero apparent weight relative to the aircraft.
The aircraft heads upward at an angle of 45 degrees. As soon as the pilot begins the rotation into the parabolic trajectory,
weightlessness is achieved. This 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 hard upward turn. 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 half way up its upward trajectory, and the pilot again initiates the zero-g parabola. [1]
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. Astronauts training for the
Moon missions practiced walking with 1/6 of their weight
to simulate the level of gravity on the Moon.
History
NASA has flown parabolic 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".[2]
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 airplane was retired in 2000 and is now on display at
Ellington Field, near the Johnson Space
Center. It's 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 airplane with a McDonnell Douglas C-9B Skytrain II that was formerly owned by KLM Airlines and the
United States Navy [1]. The
same year, the Zero-Gravity Corporation, a commercial parabolic flight operator
which offers parabolic flight to both researchers and adventure tourists, began flying parabolic flights for NASA with
Boeing 727 jets.
Since 1984, the ESA and the CNES have flown
similar reduced-gravity missions in a variety of airplanes, 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.[3]
Commercial flights
In late 2004, Zero Gravity Corporation became the first and only company in
the United States to offer parabolic weightlessness flights to the general public. Each flight consists of around 15 parabolas,
including simulations of the gravity levels of the Moon and Mars, as well as complete weightlessness.[4]
Airsickness
According to 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."
Commercial operator ZeroG Corp claims their tourist rides with up to 15 parabolas are much less traumatic compared to the
typical research flight with from 40 up to 80 parabolas.[5]
Other uses of the term
Vomit comet may also refer to any other form of transportation on which riders are said to become nauseated or seasick,
such as a bus that transports late-night revelers [6]
[7] or a fast boat such as a high speed catamaran. [8] [9]
See also
Notes
References
- Haber, Fritz and Haber, Heinz: Possible Methods of Producing the Gravity-Free State for Medical Research, Journal of
Aviation Medecine XXI (1950)
- Easton, Pam (Oct. 30, 2004). NASA's weightless aircraft is retired. Associated Press.
- Glen Golightly (May. 15, 2000). Vomit Comet finds a home. Space.com Houston Bureau.
- Dennis Overbye (March 1, 2007), Stephen Hawking plans prelude to the ride of his life, New York Times
External links
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