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Concept
Résistojet
Résumé
A resistojet is a method of spacecraft propulsion (electric propulsion) that provides thrust by heating a typically non-reactive fluid. Heating is usually achieved by sending electricity through a resistor consisting of a hot incandescent filament, with the expanded gas expelled through a conventional nozzle.
Resistojets have been flown in space since 1965 on board military Vela satellites. However, they only became used in commercial applications in 1980 with the launch of the first satellites in the INTELSAT-V program. Many GEO spacecraft, and all 95 Iridium, used Aerojet MR-501/MR-502 series resistojet engines. Nowadays resistojet propulsion is used for orbit insertion, attitude control, and deorbit of LEO satellites, and do well in situations where energy is much more plentiful than mass, and where propulsion efficiency needs to be reasonably high but low thrust is acceptable.
Resistojets have also been proposed as means of using biowaste as reaction mass, particularly in conjunction with hydrazine. Studies focus on the characteristics of steam and carbon dioxide as major constituents of a biowaste stream, and typically use cubic zirconia as a heating element.
Many satellite missions necessitate an ability for minor alterations in trajectory even after the craft has been inserted into orbit. Most satellites use monopropellant rocket motors or cold gas thrusters for such orbital adjustments. Both methods, however, suffer from some limiting drawbacks: Hydrazine, the most commonly used monopropellant, is highly expensive and due to its volatile nature unsuitable for smaller satellites that are sent to space as secondary cargo. Cold gas thrusters, while utilizing relatively cheap, inert and therefore "safe" gasses like nitrogen, suffer from low specific impulse in comparison to monopropellant motors. Resistojets are designed to bridge the gap between these two methods of propulsion, offering the safety of an inert propellant coupled with specific impulse nearing that of hydrazine.
Source officielle
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