Longer periods are created through the use of airplanes, rockets, and spacecraft. The microgravity environment associated with the space shuttle is a result of the spacecraft being in orbit, which is a state of continuous freefall around the Earth. NASA has several facilities that can provide a microgravity environment for scientific research. The MRD then matches the experiment to a facility based on the length of time needed in microgravity to perform the experiment. While the experiments drop, they are in freefall, or microgravity.
Scientists make measurements and use video cameras to observe the experiments as they fall.
The airplane climbs rapidly until it is at an approximate 45-degree angle to the horizon. Then the engines are briefly cut back, the airplane slows, and the nose is pitched down to complete the parabola. As the plane is tracing the parabolic arc, microgravity conditions are achieved for 20-25 seconds. As many as 40 arcs can be flown on a typical flight so that scientists can conduct several experiments or can repeat short runs of one experiment many times. An experiment is placed on the rocket, which is launched and then freefalls back to Earth.