An analysis of ion thruster impact on new Millennium spacecraft subsystems

The NASA SEP Technology Application Readiness (NSTAR) ion propulsion experiment is a technology demonstration payload under the New Millennium project. One of the primary objectives of this New Millennium program is to evaluate the potential impact of the ion thruster on spacecraft subsystems and payloads. Specifically, concern exists that thruster plume ions or ionized sputtered materials will be scattered onto surfaces resulting in solar array power degradation, emissivity changes in thermal control coatings, and contamination of optical surfaces. The authors have developed a parametric model of an ion thruster plume including primary beam and charge-exchange ions, hollow cathode neutralizer ions and ionized sputtered material. These models have been implemented in the Environment Work Bench (EWB) integrated analysis tool. EWB is a desktop analysis tool that models ambient and spacecraft generated environments and integrates them with interaction effects models. A calculation has been performed over the ion thruster operation time period to determine contaminant deposition on spacecraft surfaces and resultant solar array power reduction. Preliminary results, presented here, indicate that there will be no significant power system degradation over the mission due to contamination of solar array surfaces by sputtered thruster grid molybdenum ions.