Susceptibility of spacecraft to impact-induced electromagnetic pulses

Spacecraft are routinely bombarded with interplanetary dust particles, called meteoroids, and defunct objects of hu man origin, called orbital debris. Collectively we refer to these particles as hypervelocity impactors. Meteoroids have impact speeds up to 72 km/s and orbital debris have impact speeds <11 km/s in low Earth orbit. Most hypervelocity impactors possess enough energy to ionize and vaporize themselves as well as a significant portion of the spacecraft material upon impact, forming a plasma that rapidly expands into the surrounding vacuum. A plasma is a gas of charged particles whose dynamics are dominated by electromagnetic forces. Under certain conditions, the expansion of the impact-induced plasma can trigger electrostatic discharges and electromagnetic pulses that can disable or destroy spacecraft electronics, and in the worst cases, result in complete loss of mission. A number of spacecraft have experienced unexplained electrical anomalies correlated with impact events or meteoroid showers. The associated electrical effects and potential for damage to satellite electronics through these processes have not been previously investigated. This paper describes multi-physics simulations of particle impacts on spacecraft using a combination of computational continuum dynamics and electromagnetic particle-in-cell methods. These simulations incorporate elasticity and plasticity of the solid target, phase change and plasma formation, strongly coupled plasma physics due to the high density and low temperature of the plasma, a fully kinetic description of the plasma, and free space electromagnetic radiation. By simulating a series of hypervelocity impacts, we determine properties (e.g., temperature, expansion speed, and charge state) of the plasma plume for impact speeds from 10 km /s to 72 km/s, and particle masses from one femtogram to one microgram. These plasma properties yield the amplitude, frequency, directionality, and the spatial and temporal decay of impact-induced electromagnetic pulses. In this paper, these simulation results are used to assess the susceptibility of spacecraft components to electrical damage from meteoroid and orbital debris impacts. The results show that electromagnetic pulses are only produced for impact speeds greater than 18 km/s and that the pulses are capable of causing significant damage via current and voltage spikes for impact speeds greater than 50 km/s. The particle mass does not affect these speed thresholds. The model predicts that the electric and magnetic field limits to which spacecraft electronics are currently designed are far below the fields produced by the fastest meteoroid impacts. While electronics are normally shielded in a Faraday cage, this also provides insufficient mitigation at the expected frequencies of the radiation from electromagnetic pulses. Results indicate the fields decay rapidly from the point of impact, meaning that a susceptible component must be physically nearby to be threatened. Understanding key parameters of impact plasma plumes and associated electromagnetic pulses will aid in designing more robust and reliable spacecraft that are well protected in the space environment.