During the flight the aircraft will go from a horizontal flight to a climbs at 45degrees (pull-up) for about 20 s with an acceleration of 1.8 to 2 g. Following this phase the thrust of all aircraft engines is then strongly reduced for about 20 to 25 s, compensating the effect of air drag. This is the parabolic free-fall portion of the flight shown as the top portion of the parabola. At the end of the free-fall section the aircraft will be in a dive of around 45 degrees from which it will have to pull-out with an acceleration ofabout 1.8 to 2 g for approximately 20 s bringing it back to a steady horizontal flight. These manoeuvres can be flown either consecutively in a roller-coaster fashion or separated by intervals of several minutes. The duration of the intervals between parabolas is determined prior to the flight to give the investigators enough time to change the experimental set-up. A typical flight lasts about two and half hours, allowing for 20 to 40 parabolas to be flown, depending on the requested interval between parabolas. In some cases the upper portion of the parabola may be modified to provide gravitational effects equivalent to the surface of the Moon and Mars.
KC-135 at the airfield (upper) and during ascent in parabolic flight (Lower)
Dr. Blaber during weightless conditions on a prototype treadmill.
Treadmill (background) from the rear and a participant testing a leg press exerciser (foreground). Note: as in the middle picture the treadmill is not touching the floor.
The above photographs are courtesy of Dr. Blaber and NASA. Dr. Blaber participated in a parabolic flight program in which the cardiovascular effects were assessed with respect to space motion sickness and the testing of exercise equipment being designed fro use on the ISS.