Because of this instability, the MHD generator Typhoeus CEA did not work (it was designed from the perspective of a functioning bitempérature). But this instability could be mastered:
In 1966 the physicist Jean-Pierre Petit put out a first method, he had imagined. It was successfully tested in a pulsed MHD generator powered by a generator of hot gas, shock wave (shock wave wind tunnel called, more commonly shock tube, "shock tube"). The shock tube creates a burst of gas at very high temperatures (commonly 10 000 ° C for a burst rare gas such as argon, the pressure being of the order of the atmosphere and the speed of 2700 m / s ). These bursts are of short duration (50 microseconds) but still long enough that the tests can be considered significant, vis-à-vis the phenomena studied. Under these experimental conditions, the instability develops very quickly, within microseconds. Jean-Pierre Petit was one of those who have helped to define the conditions for development of electrothermal instability. For conditions gazodynamiques data, we can calculate the critical value of the Hall parameter beyond which the instability develops. When the plasma is called "Coulomb" (Dominated Coulomb plasma), that is to say, when the collision frequency-electron gas is dominated by those of electron-ion collisions, this critical value is close to 2. In experiments conducted by Jean-Pierre Petit, given the value of the magnetic field of 2 tesla, the plasma nozzle inlet was a priori very unstable (the value of the Hall parameter was well above its critical value). But, as he had surmised, it turned out that the development rate of ionization could be sufficiently rapid that the plasma from steady Coulomb, see his collision frequency electron-gas grow rapidly, and by beyond the local value of the Hall parameter to drop below the critical value. The growth of this collision frequency is related to high values of electron collision cross sections ion, which are three to four orders of magnitude higher than those associated with collisions between electrons and neutral species. And could be successfully run in 1966 at the Institute of Fluid Mechanics of Marseille, an MHD generator bitempérature, stable, with a homogeneous plasma in the MHD nozzle. The first tests gave an electron temperature of 10,000 ° C gas temperature of 6000 ° C, with an electrical capacity of 2 megawatts.
Jean-Pierre Petit immediately proved the authenticity of this non-equilibrium state by adding to the test gas 2% carbon dioxide. The collision cross section, linked to the phenomenon of excitation by electrons these molecules is high, this phenomenon very effectively absorbed energy any excess held by the electron gas, returning the temperature thereof to a close neighbor that of the gas. So this situation was out of balance she annihilated by these collisions between electrons and CO2.