Performance of a High Specific Impulse Hall Thruster

Busek Co. Inc., in a SBIR program sponsored by the NASA Glenn Research Center, designed, and tested a nominally 1 kW thruster capable of both single stage and two-stage operation. This paper describes the results from detailed performance testing using several thruster geometries in both the single stage and two-stage configurations. Experimental testing revealed that specific impulses of greater than 3000 seconds at moderate applied voltage(s) (<1000 V) is feasible. Measured thrust, efficiency and Isp were obtained over a range of input power and propellant mass flowrates providing detailed characterization of both single and two-stage designs. In the single stage configuration, the measured thrust was 88 mN and 3000 sec Isp at an input power of 2.3 kW into the discharge. In the twostage configuration, the maximum Isp obtained was 3300 seconds, also at 2.3 kW input power. The experimental results are used to compare and contrast the performance of single stage and two-stage operation. Data was comparable in both configurations and showed little advantage for this style of two stage operation. Also presented are the results from a simple analytical model that is used to characterize and understand the performance of the thruster(s). The model, applicable to all sizes and types of Hall thrusters, is useful in correlating the measured thrust and Isp expressed in terms of two global parameters, primary electron utilization and a lumped voltage loss. Analysis of the data using the model show that electron utilization efficiency is an important parameter for increasing thrust efficiency at high Isp.