Analysis of plasma contactor on-orbit performance

Abstract

A hollow cathode based plasma contactor (PC) will be flown on the International Space Station (ISS) to control the Station's potential to within +/- 40 V with respect to the local ionosphere. Prediction of the expected on-orbit performance of the ISS plasma contactor involves looking at both the plasma contactor current-voltage characteristics, and the effect of the interaction of the PC current plume with the space station on that relationship. Several phenomena can affect the ability of the plasma contactor to keep the space station to within +/- 40 volts of plasma ground. Among these effects are the wake caused by the motion of the space station through the local ionosphere, the impingement of the PC plasma plume on space station surfaces, and current loops between the plasma contactor and the station photovoltaic arrays. In this paper, we first review the background on the ISS voltage requirement and how the PC current-voltage requirement derives from that. We present new models of PC plume expansion based on laboratory data. These models are then used in the Environment Work Bench to examine the interactions between the plasma contactor and its environment including both ISS structure, the PVA's and the local ionosphere. (Author)