NASA has several mechanisms for assisting researchers investigating the effects of reduce gravity on physical and biological systems. The reduced gravity environment is variously called microgravity, zero gravity, free fall, or weightlessness. (For more on "micro" gravity, see the Gravity section of C.K. Purvis' document, "The Space Environment: An Overview.") The document you are reading is a brief introduction to the NASA facilities and provides contact information for researchers wishing to make use of those facilities.
Contrary to a surprisingly popular belief, NASA does not have a "zero gravity chamber." There is no way to "turn off" gravity and allow people and experiments to float freely while on or near the Earth. The main mechanism for investigating microgravity's effects is to put the experiment in free fall, where the whole experiment is falling freely through air or space, and every part of the experiment is equally affected by gravity. The following facilities make use of this technique to allow microgravity experimentation:
NASA has several drop tower facilities. In a drop tower, the experiment is dropped from the top of the tower and falls freely to the bottom, where it is deccellerated and recovered. Some towers can be evacuated to greatly reduce air resistance, providing very "clean" microgravity. The difficulties with drop towers include the short duration of microgravity exposure, the small size of the experiment mandated by the diameter of the shaft, and the decceleration experienced by the experiment at the bottom of the shaft.
For more information on the 2.2 Second Drop Tower at NASA Lewis Research Center, contact Jack Lekan at (216) 433-3459 or by e-mail at firstname.lastname@example.org
For more information on the Zero Gravity Facility at NASA Lewis Research Center, contact Dennis Thompson at (216) 433-5485 or by e-mail at email@example.com
An aircraft can be flown on a "parabolic" trajectory which provides a reduced gravity environment at the top of the parabola. NASA has two aircraft which fly these trajectories regularly, the KC-135 and the DC-9. The DC-9 has been continuously booked with flight experiments since it went into service here at LeRC. The difficulties with zero gravity aircraft include motion sickness, the short duration of microgravity exposure, and residual accelerations due to aerodynamic effects causing a "dirty" microgravity enviroment.
For more information on the DC-9 at NASA Lewis Research Center, contact Eric Neumann at (216) 433-2608 or by e-mail at firstname.lastname@example.org
For more information on the KC-135, contact:
NASA/Johnson Space Center Reduced Gravity Office Mail Code CC32 Houston, Texas 77058 (713) 244-9875
Microgravity experiments can be flown on "sounding" rockets which fly sub-orbital trajectories. These rockets, which NASA can launch out of its Wallops Island Facility, allow longer durations than drop towers, but a cleaner microgravity environment than zero gravity aircraft can provide. The difficulties with sounding rockets include cost, experiment mass and size, and the accelerations of launch and landing.
While NASA provides some unique scientific capabilities, there are many other launch services available from a wide variety of sources around the world.
Microgravity experiments can be flown on the Space Shuttle. This provides up to 14 days of exposure to a relatively clean microgravity environment, while allowing servicing of the experiment by astronauts. Disadvantages of Shuttle experiments include cost, time required to develop and manifest experiments, and launch accelerations and vibrations.
For more information about Shuttle payload accomodations for scientific experiments, contact:
NASA/Johnson Space Center John A. Rummel, Ph.D. Assistant to the Director for Science Payloads Mail Code SA Houston, TX 77058 (713) 483-7317
In cooperation with the Russian Space Agency, NASA is flying a limited set of experiments on the Mir space station. This can provide an extended duration exposure to microgravity, with either astronauts or cosmonauts tending the experiments. Disadvantages of Shuttle/Mir experiments include cost, time required to develop and manifest experiments, launch accelerations and vibrations, and the language barrier.
For more information about Shuttle/Mir payload accommodations, contact:
NASA/Johnson Space Center Richard Nygren Assistant Director for Russian Programs Mail Code SA Houston, TX 77058 (713) 483-7317
To simulate the effects of microgravity on cell cultures, the Medical Sciences Division at NASA/Johnson Space Center has developed the bioreactor. This uses a rotating cylinder to randomize the gravity vector in a small sample, greatly reducing shear forces and simulating microgravity exposure.
For more information about the bioreactor, contact: Dr. Neal R. Pellis at NASA JSC