Theory and analysis of plasma formed by hypervelocity impacts

Meteoroid and space debris impacts on spacecraft are known to cause mechanical damage, but the associated electrical effects on spacecraft systems remain poorly understood. We present a theory to explain plasma production and subsequent electric fields occurring after a meteoroid strikes a spacecraft, and ionizes itself and part of the spacecraft. This plasma, with a charge separation commensurate with different species mobilities, can produce a strong electromagnetic pulse (EMP) spanning a broad frequency spectrum. Subsequent plasma oscillations can also emit significant power. We present both the theory for a dust-free plasma expansion with coherent electron oscillations, as well as results from an experiment carried out at the Max Planck Institute in Heidelberg, Germany using the Van de Graaff dust accelerator. Our experiment used a suite of sensors, including retarding potential analyzers (RPAs), a photomultiplier tube (PMT), and radiofrequency (RF) patch antennas spanning VHF through UHF. The targets included both charged and uncharged material. Our results show that RF emission occurs in conjunction with strong returns in the plasma sensors and depends strongly on the target configuration. Charged targets produced “beamed” plasma clouds, while uncharged targets produce significant return at a broader expansion angle.