Primary Role: NASA Testbed
Under various designations, including NC-135A, NKC-135A and NKC-135E, NASA and the U.S. Air Force operate a fleet of heavily-modified C-135 airframes as aerial testbeds. The type of work performed by these aircraft is greatly varied, but includes refueling tests with new aircraft types, airborne laser trials, weightlessness training for astronauts, and numerous programs involving the testing of airborne equipment and space technology.
Zero Gravity Trainer (Vomit Comet)
The NKC-135A Zero Gravity Trainer is used to fly parabolas to investigate the effects of “zero” gravity. This aircraft, designated NASA 930, is operated by the Johnson Space Center’s Reduced Gravity Office in Houston, Texas.
To her crew, she’s the “Weightless Wonder”, to her passengers, she’s the “Vomit Comet”. Regardless of the name, this unusual aircraft helped the Planetary Missions and Materials Branch at the Johnson Space Center take another step closer to renewed human exploration of the moon, and beyond.
To fly on the “Comet” you must hold an Air Force Flying Class III Medical Examination card and complete an Aerospace Physiological Training course. The objective of the physiological training is to familiarize personnel who are exposed to a lowered barometric pressure with the physiological stresses encountered and how to successfully overcome these stresses.
By flying a series of “roller-coaster” parabolic maneuvers, short periods of reduced gravity are experienced onboard. Most flights are dedicated to zero-g astronaut training and equipment tests. During a “typical” mission, which lasts about two hours, the aircraft usually flies 40 parabolas. Longer flights are possible, depending on fuel and gross weight limitations. Consequently, more parabolas mean more flexing of the airframe and more stress.
Note: The NKC-135A “Vomit Comet” was used to film the zero-gravity scenes for the movie Apollo 13. Ron Howard, his crew, and the cast spent over six months on the plane to produce the movie.
Wingtip Research Aircraft
In 1979 and 1980, the Dryden Flight Research Center at Edwards AFB, California conducted a special wingtip “winglet” test program with the NKC-135. Winglets are small, nearly vertical fins installed on an airplane’s wingtips to help produce a forward thrust in the vortices that typically swirl off the end of the wing, thereby reducing drag. This winglet idea was tested at Dryden on a modified KC-135A tanker loaned to NASA by the Air Force. The research showed that the winglets could increase an aircraft’s range by as much as 7% at cruise speeds. The first application of NASA’s winglet technology in industry was in general aviation business jets, but winglets are now being incorporated into most new commercial and military transport jets, including the C-17 Globemaster III military transport.