Development of a deterministic Boltzmann-Poisson solver for the simulation of a rarefied plasma plume

The DRAG-ON facility at the von Karman Institute is designed to replicate very low Earth orbit conditions for studying air-breathing electric propulsion intakes and gas-surface interactions. The particle flow generator exhausts a partially ionized plasma plume with ions reaching orbital speeds. Such a flow presents significant modeling challenges because of the charged particles, large differences in timescales between electrons and heavy species, reactive collisions, and the rarefied nature the flow. Accurate modeling of the electron energy distribution function (EEDF) is essential in this context, particularly for interpreting optical emission spectroscopy measurements via collisional-radiative models, where excitation rates are sensitive to the EEDF shape, especially its high velocity tail.

To address this difficulty, we are developing a deterministic spectral-lagrangian solver for the Boltzmann-Poisson system, aimed at computing the EEDF in weakly collisional, chemically reacting plasmas, ultimately for fully kinetic simulations of the plasma plume. The method represents the EEDF in velocity space, offering an interesting alternative to particle-based approaches which feature high statistical noise in the tails of the distribution. This presentation will focus on 0D results with elastic collisions as a first verification step, laying the foundation for future extensions to inelastic processes and full plasma chemistry.