Technology of elevated voltage solar arrays: Key items test and evaluation. Part 2: Simulated LEO-plasma tests

The electrical layout of a 250 kW solar array was analyzed in TEVSA-KITE I and potential problem areas were identified. In the present report (TEVSA-KITE II) research and development activities are described which have been made necessary by the desire to understand the phenomena observed in the initial tests and to make a more complete assessment of the in-orbit effects of 200 - 1000 volt solar arrays. System and component requirements of the power-conditioning system were compared with current practice in order to identify areas requiring development effort. It was found that for voltages up to 200/300 V, components and systems are available but are not yet space qualified. The high-voltage tests of solar-array components were continued. A critical threshold of 500 - 600 V was identified for vacuum orbit conditions. Outgassing after launch may be a potential reason for failure. The plasma tests at Freiburg showed that there was a very narrow range in which ohmic discharge occurs. Outside this range, a dramatic increase in leakage current is expected. The critical voltage threshold was identified at ca. 250 V. The study shows that current solar-array technology is adequate for low Earth orbit environment up to a voltage of about 250 V. Plasma discharge will then be initiated. At voltages above 500/600 V, partial discharge through the substrate will reduce the lifetime of the solar array.