Solar Arrays for Direct-Drive Electric Propulsion: Arcing at High Voltages

The results from an experimental investigation to assess arcing during operation of high-voltage solar arrays in a plasma environment are presented. The experiments were part of an effort to develop systems that would allow safe operation of Hall-effect thruster(s) in direct-drive mode. Arc discharges are generated when the array is biased negative with respect to the plasma. If sustained for long periods of time between adjacent solar cells, arcs can severely damage a solar array, thus significantly shortening its lifetime. Most often sustained arcs are triggered by plasma produced during short-duration discharge arcs (approximately 20 ms). These "trigger" arcs are sparked between the semiconducting cell and the covering dielectric. Both trigger and sustained (greater than l-ms) arcs have been captured during the tests. Current and voltage waveforms associated with the different arc events are presented. The test results have defined operational limits (thresholds) for the various array concepts studied that minimize the likelihood of damage from sustained arcs. Experimental trends regarding the effect of the solar-array substrate on arc duration are also presented.