PIC-MCC Characterization of Expanding Plasma Plumes for a Low-Density Hypersonic Aerodynamics Facility

Ground testing of satellite aerodynamics in Very Low Earth Orbit requires facilities able to produce a rarefied flow of particles at hypersonic speeds up to 8 km/s. This is not possible with conventional gas dynamic nozzles. A plasma source, instead, can reach the required velocity by electrostatic acceleration of ions. In this work, we investigate the applicability of such approach to a low-density hypersonic aerodynamics facility currently being designed at the von Karman Institute. First, we present the development and verification of the PIC‑DSMC code PANTERA. Then, we employ it to perform 2D3V axisymmetric simulations of the expansion of an argon plasma plume in the vacuum chamber of the facility. We analyze the behavior of electron and ion currents in the collisionless plume. We notice that the expansion of electrons and ions is not isothermal as often assumed. We study the effect of plume density, showing that the divergence of the plume increases at higher injection densities. We investigate the result of collisions between the plume ions and a background gas, showing that charge exchange collisions can neutralize up to 10% of the ion beam. Finally, the consequences of our findings on the application to aerodynamic testing are addressed, and possible solutions proposed.