Ground-Based Experiment of Electric Breakdown of Spacecraft Surface Insulator in an Ambient Plasma Environment

Abstract

In the future, LEO spacecraft will be larger and higher powered. Because of the balance of the leakage currents through the ambient space plasma, their main conductive body will have a higher negative potential without plasma contactor operation. When the spacecraft operates with a higher voltage, more intensive arcing is suspected to occur on the surface. In this study, a ground-based experiment was carried out to understand the arcing phenomenon and to examine the influences of the ambient space plasma on the arcing process. Simulating plasmas were generated by electron-cyclotron-resonance discharge. When arcing occurred on negatively biased anodized-aluminum-sample (AAS) plates in the plasma environment, the time variations in the arc current and bias voltage were measured. The arc-spot diameter was also measured. The single-arcing characteristics showed that both the peak arc current and the total charge emitted by arcing increased with the initial-charging voltage and neutralparticle number density. The diameter of the arc spot increased with the initial-charging voltage although it was almost constant regardless of the neutral-particle density. The repetitive-arcing characteristics showed that the arc rate gradually increased with the arcing number. Lots of overlapping arc spot were observed after 1000 arcings, and its number increased with the arcing number. The influences of the initial-charging energy on arcing characteristics were also examined by widely changing the capacitance and the initial-charging voltage. The arc-spot diameter intensively increased with the initial-charging energy, and the fitting line could be evaluated. Accordingly, a high-voltage operation of the LEO spacecraft might bring a drastic degradation of AAS by arcing, depending on the ambient plasma conditions and spacecraft capacitance.Index Terms-Anodized aluminum, arc plasma, arc spot, discharge characteristics, electric breakdown, ground-based experiment, insulator surface, spacecraft environment, space-plasma environment.

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