Bismuth Hall Thruster Spacecraft Interactions Study

Busek Co. Inc. and Stanford University propose to develop diagnostics to characterize the plume properties and quantify contamination effects of Hall thrusters operating on condensable propellants. Phase I proof-of-concept analysis and experiments will demonstrate the ability of the proposed diagnostic techniques to accurately measure the plume. In Phase I, Busek will characterize the plume of an existing bismuth Hall thruster using Faraday and Langmuir probes, and determine whether specialized probe development is required. Busek will also design a plume contamination and erosion experiment for Phase II. In a Phase I subcontract, Stanford and Busek will design, build, and test a probe for determining sticking and scattering coefficients of neutral bismuth as a function of incident angle. In Phase II, a similar ion probe will be built and used to determine surface interaction coefficients as a function of energy and angle. Both the neutral and ion probes will be tested with the Busek thruster running Xe and Bi. In Phase II, the Bi plume and its effects on key spacecraft materials will be measured in detail. The data will enable accurate numerical plume/spacecraft interaction models and lead to a flight model thruster with T/P much greater than possible with Xe.