Low Power Arcjet Performance Evaluation

The use of electric propulsion for stationkeeping and orbit repositioning missions offers significant' advantages to Air Force users. Commercial interest in electric propulsion has largely focused on geostationary north-south stationkeeping of high power communication satellites. and has resulted in the development and flight qualification of several thruster types operating in the 1500-2000 W power range. Since the power available for propulsion on many current and future Air Force satellites is substantially less. the development of high performance, low power thrusters is important to the support of Air Force missions. To support this development effort, the Air Force Phillips Laboratory has begun a low power arcjet research project to quantify and improve thruster performance. The objective of this effort is the improvement o thruster performance over the powe rrange of 300-600 W using storable propellants. In this first phase, thrust, specific impulse. thrust efficiency and arcjet anode temperature were measured over the power range of 900-1200 W. A 1 kW modular arcjet operating on simulated hydrazine N2-2H2, propellant with regular and extended length anodes was used for testing; the extended length. anode provided a larger surface for temperature measurements. Thrust stand measurements were used to obtain arcjet performance data and two-color optical pyrometry and thermocouple systems were used to measure anode temperature. Performance measurements were taken with both nozzles while temperature measurements were made with the extended anode alone. Measurement errors were quantified at 5% for thrust and 6-8% for temperature. Methods of reducing these errors to 2% for both cases are discussed. Best available copy. Prepared in collaboration with Sparta Inc. and Aerospace Corp.