Effects of metallic plasma thruster plume on solar cells

The increase in efficiency per surface area of solar cells in recent years, coupled with the continuous miniaturization of electric propulsion systems, have made propulsive capability a highly viable option for small satellites. These propulsion systems enable small satellites to perform orbital maneuvers, to the point where CubeSat-class satellites have been suggested for missions past the lunar orbit. However, applications of these miniature electric propulsion systems on small satellites pose a new challenge for satellite designs, where the appropriate distancing of the thrusters from solar panels cannot be accomplished within the limited volumetric constraints of small satellites. Accordingly, the degradation effects of the exhaust plume on the solar panels may have an undetermined impact on the small satellites. In addition, these new generation miniature electric propulsion systems often use an unconventional propellant that produces unconventional plasma within their plumes. One example is a pulse plasma thruster using metal propellant that results in a metallic plasma plume. Solar cell performance degradation due to radiation and ultraviolet light has been thoroughly studied in the past. Gaseous-plasma effects also have been studied, but there is a lack of data on how a metallic plasma plume will affect solar cells mainly because it is non-conventional plasma that is not frequently used in space applications. The main goal of this research is to characterize the degradation and coating effects of metallic plasma plume on solar cells. In particular, this study will focus on the Micro-Cathode Arc Thruster developed at The George Washington University. It is a compact propulsion system designed for small satellites and has been previously flown on a CubeSat. This paper will examine the theoretical issues, and characterize solar cell performance degradation resulting from deposition of the metallic exhaust plasma plume on the surface of the cover glass.