Electrical characteristics of a Hall effect thruster body in a vacuum facility testing environment

Abstract

The operational characteristics of Hall effect thrusters are altered by conductive surfaces in vacuum facilities. Conductive surfaces alter charge distribution in the plume by providing pathways for electron-ion recombination that do not exist in the spaceflight environment. Charge recombination pathways impact thruster performance and plume behavior through mechanisms that are not entirely understood. The incomplete understanding of the relationship between charge recombination pathways and thruster behavior limits the ability to characterize thruster performance through ground testing. This paper quantifies the effect of polarity and magnitude of body-to-cathode voltage on coupling between the thruster body and the local plasma environment. The effort operates the T-140 Hall thruster at a single, fixed operating condition of 300 V, 3.5 kW, with anode and cathode xenon flow rates of 11.6 ± 0.03 mg/s and 1.61 ± 0.12 mg/s, respectively. During data collection, the chamber was maintained at a pressure of 8.7 × 10–6 Torr-Xe. The thruster body-to-ground voltage is manipulated by varying body-to-ground resistance. Results show the thruster pole face and body circumference couple to the local plasma environment through distinct sheaths. The polarity of the body-to-cathode voltage determines the characteristics of these sheaths. Therefore, the body-to-cathode voltage controls the interaction between the thruster body recombination pathway and the local plasma environment.