Preliminary Study of Arcjet Neutralization of Hall Thruster Clusters (Postprint)
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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Clustered Hall thrusters have emerged as a favored choice for extending Hall thruster options to very high powers 50 kW - 150 kW. This paper examines the possible use of an arcjet to neutralize clustered Hall thrusters, as the hybrid arcjet-Hall thruster concept can fill a performance niche amongst available propulsion options. We examine missions on which this hybrid concept would be a competitive or favored thruster option, report on fundamental experiments to understand how much electron current can be drawn to a surrogate anode from the plume of low power arcjets operating on hydrogen and helium, and then demonstrate the first successful operation of a low power Hall thruster-arcjet neutralizer package. In the surrogate anode studies, we find that the drawing of current from the arcjet plume has only a weak effect on overall arcjet performance thrust, with a slight decrease in arc voltage with increased extracted current. A single Hall thruster - arcjet neutralizer package was constructed for the hybrid concept demonstration. The arcjet operated at very low powers - 70-120W on helium, at a mass flow rate of 4.5 mgs, and was able to effectively neutralize the - 200 -900W xenon Hall thruster causing little measurable departure from the hollow-cathode neutralized Hall thruster VI characteristics up to 250V. At higher helium mass flow rates, the Hall discharge current is slightly perturbed from its expected values, due most likely to the ingestion of helium. Further developments of the hybrid concept to clustered configurations and higher powers will require a vacuum facility that can pump tens of milligrams of helium while maintaining the low pressures needed for normal xenon Hall thruster operation.
- Electric and Ion Propulsion
- Rocket Engines