STATE-OF-THE-ART OF RADIOFREQUENCY ION THRUSTERS

Since 1960, a family of radio-frequency ion thrusters (RIT) with ionizer diameters from 4 to 35 cm has been studied, developed, and tested at Giessen University. The 10-cm North-South-Stationkeeping engine RIT 10, with 10 mN of nominal thrust, has been industrialized since 1970 and fully ground qualified with mercury through 1980. This thruster has been redesigned for xenon as the propellant since 1983 envisaging a flight test onboard the European Retrievable Carrier EURECA in the year 1991. A chance for an operational application of the RIT 10 system is given onboard the European Space Agency satellite SAT 2, which is planned to be launched in the early 1990s. Because of the grown masses of satellites and with it the higher thrust requirements for North-South-Stationkeeping, a laboratory prototype of a scaled-up engine, the RIT 15, is presently under performance mapping aiming at a thrust level of 50 mN. For primary electric propulsion a large prototype engine, RIT 35, has been developed. After starting in 1984 with performance mapping using a flat grid extraction system and mercury as the propellant, the thruster has been modified for inert gases as argon and xenon. Finally, a dished grid extraction system has been fabricated and tested on the RIT 35 thruster.