Multicomponent Plasma Expansion Model for Arc Discharges on Large-Area Solar Arrays

Abstract

For decades it has been known that spacecraft charging-induced electrostatic arc discharge on solar arrays can cause cell degradation and damaging secondary arcs. While discharging on large-area solar arrays is the concern, there is no space data on primary arc current magnitudes on large arrays. Laboratory testing is normally performed on coupons with just a few solar cells. External capacitors and circuitry based on theoretical models are used to simulate the arc current profile from the charge stored on the rest of the array. Previously, the current profiles for large arrays were generated assuming that the arc plasma expanded at a constant velocity and instantaneously discharged cells at the plasma perimeter. Arc-current profiles using this perimeter model failed to agree with laboratory tests on large arrays. An improved model needs to account for the range of expansion velocities in a multicomponent plasma, and that the cell neutralization at the perimeter is not instantaneous but is limited by the arc-plasma thermal electron current density. A new, multifluid model of arc-plasma expansion addresses both concerns. The model assumes as input primary arc ion generation rates. Ion expansion velocities are calculated self-consistently from electric potentials in the expanding plasma.