Characterizing hypervelocity impact-generated dense plasmas via a computational thermodynamic and chemical kinetics analysis

Hypervelocity impacts (HVI) from micrometeoroids and orbital debris can produce dense plasmas that may interfere with spacecraft electronics via electromagnetic radiation. This work presents a computational framework to characterize plasma formation during the early stages of an HVI event. A solid-state shock model is used to calculate post-shock, pre-ionized thermodynamic properties for iron-on-iron impacts across a range of velocities (6–50 km/s), employing five different equations of state (EOS). These results serve as inputs to a 0D3V Monte Carlo collision model, which simulates the transient ionization of the shocked material. At low impact velocities (15 km/s), all EOS produce similar results but diverge at higher velocities due to differences in how they capture phase transitions and quantum effects. The system enters a warm dense matter regime in the post-shock, pre-ionized phase, characterized by strongly coupled ions and moderately degenerate electrons. Ionization occurs on the order of femtoseconds, which is much faster than plasma expansion or electromagnetic propagation over an impactor's characteristic length, validating the assumption of instantaneous plasma formation. We find lower impact velocities will produce partially ionized plasmas, while higher impact velocities will produce fully ionized plasmas, with the threshold defining “low” and “high” velocities depending on the EOS used. Overall, this work provides estimates of temperature, density, and ionization levels immediately after impact, offering improved initial conditions for plasma expansion and radiation models. It also underscores the need for more accurate EOS in extreme regimes and lays the groundwork for future integration with experimental validation and electromagnetic diagnostics in the context of spacecraft missions.