From years 2000 to 2002, during parabolic flight experiments, our French team (from Lyon, Paris & Bordeaux) has studied the behavior of strongly vibrated granular matter in a 3-D container in low gravity environment. In a dilute regime, granular matter seems to behave like a usual gas in which particles follow erratic motions, but with striking different properties. Contrarily to usual gases, a "granular gas" is dissipative due to inelastic collisions between particles. When the number of particles in the container is varied, the collision statistics of a granular gas thus differs significantly from the one of usual gas:
The most striking result is that the collision frequency of particles does not increases linearly with the number of particles in the container as expected for usual gases. Due to the dissipative nature of collisions, the mean velocity of particles thus depends on the number of particles. When the number of particles in the container is doubled, the kinetic energy of particles thus is not doubled (this is not an extensive variable).
These results have been published in Europhysics Letters in 2006.
The motivation for low gravity is to achieve an experimental situation in which inelastic collisions are the only interaction mechanism, and where only one "input" variable (the inverse vibration frequency) has a dimension of time.
Parabolic flights are used to conduct short-term microgravity scientific and technological investigations, to test instrumentation prior to use in space, to validate operational and experimental procedures, and to train astronauts for a future space flight.
Such flights are conducted on specially-configured aircraft , and provide a period of up to 20 seconds of reduced gravity or weightlessness. During a flight campaign , which normally consists of three individual flights, around 30 parabolas are flown on each flight, i.e. around 90 parabolas in total. On each parabola, there is a period of increased gravity (1.8 g) which lasts for 20 seconds immediately prior to and following the 20 second period of reduced gravity.
ESA performed its performed its 24th campaign using the newly available Airbus A-300 Zero-G aircraft of CNES in September 1997, and it is this aircraft that has been used ever since. The Airbus A-300 Zero-G is operated out of the Bordeaux-Mérignac airport by the company Novespace.