Annular Colloid Thruster for Three-Axis Stabilized Military Satellites.

摘要

The report describes a program to increase the performance capability of high thrust density colloid thrusters. Single emitter sources have been developed which produce greater than 25micro lbs thrust at 75percent efficiency and 1300seconds specific impulse as measured by time-of-flight techniques. Multi-source modules were also built and successfully tested in the 100micro lb range for periods of the order of 100hours. The ability to maintain constant performance within plus or minus 3percent was also demonstrated. Beam probe measurements indicated that 90percent of the propellant exhaust was contained with a 15degree half angle. Lithium iodide and potassium iodide doped glycerol solutions were briefly looked at as candidate propellants with no performance improvements observed. Also the ability of an antistatic additive to induce electrical conductivity in a low vapor pressure pump oil was investigated with negative results. New evaporation rate measurements made with pure glycerol showed that the sodium iodide/glycerol evaporation rate was 40percent below that of pure glycerol. Furthermore the measured results showed that the evaporated mass loss at typical operating temperatures would be of the order of one percent of the nominal thruster operating mass flow. (Modified author abstract)