Advanced high thrust colloid sources

Abstract

This paper describes recent advances in the development of high-thrust tubular colloid sources for satellite applications. Single emitter technology has advanced to the point where steady reliable performance has been demonstrated at greater than 111 /zN (25 yJb) per unit, 75% time-of-flight efficiency, and 1300 sec specific impulse for periods on the order of 100 hr. The most significant findings were the importance of orienting the emitter vertically in order to equalize gravitational effects around the emitter rim, the need to enlarge the extractor aperture, and the development of special tooling techniques for manufacturing emitters. A four-source module was subjected to extensive performance testing in addition to runs of 100 hr and 360 hr. Long-term steady performance was demonstrated at several levels up to 547 /*N at 75% time-of-flight efficiency and 1325 sec specific impulse. The ability to neutralize the beam without interfering with thruster performance was also demonstrated. Beam probe measurements showed that 90% of the beam was contained within a 15° half angle. The thruster's ability to provide constant performance to within ±3% was also demonstrated. During short-term testing at high-feed pressures, the thruster produced 1339 /iN at 70% efficiency and 1029 sec specific impulse.