Mission advantages of constant power, variable Isp electrostatic thrusters

Abstract

Electric propulsion has moved from stationkeeping capability for spacecraft to primary propulsion with the advent of both the Deep Space One asteroid flyby and geosynchronous spacecraft orbit insertion. In both cases notably more payload was delivered than would have been possible with chemical propulsion. To provide even greater improvements electrostatic thruster performance could be varied in specific impulse, but kept at constant power to provide better payload or trip time performance for different mission phases. Such variable specific impulse mission applications include geosynchronous and low earth orbit spacecraft stationkeeping and orbit insertion, geosynchronous reusable tug missions, and interplanetary probes. The application of variable specific impulse devices is shown to add from 5 to 15 % payload for these missions. The challenges to building such devices include variable voltage power supplies and extending fuel throughput capabilities across the specific impulse range.

Ion species fractions in the far-field plume of a high-specific impulse Hall thruster

“…[1][2][3][4] The NASA-173M series of laboratory-model Hall thrusters were conceived in order to understand the design challenges and physical mechanisms determining performance at high-specific impulse (2000 to 3000 seconds). [5][6][7][8][9] The basic design philosophy was that changes to the magnetic field topography would be required for efficient operation above 1600 seconds specific impulse.…”

Hall Thruster Technology for NASA Science Missions

“…Prior Hall thrusters have been designed for single set-point operation as might be used for north south station keeping of a geostationary communication satellite 15 or with a moderate throttle-ability as might be used for a combination of orbit insertion, station keeping, and de-orbit. 16 Prior to this investigation the challenge of designing a Hall thruster intended for operation over a wide range of input powers as needed for NASA science missions had not been addressed.…”

Performance of Solar Electric Powered Deep Space Missions Using Hall Thruster Propulsion

“…A common theme in past interplanetary mission analysis work is that the optimal specific impulses required for deep space missions are too high for Hall thrusters to attain, implying that the performance of the Hall thrusters would be inferior to the higher I sp ion thrusters. 6,7,8 While this may be true for constant power missions, it does not hold true for certain power-limited deep space missions. Fiehler and Oleson compared Hall and ion technology performance results for direct Earth-Mars Solar Electric Powered (SEP) missions.…”