A non-equilibrium numerical study of a microwave electrothermal thruster

A numerical simulation of a microwave electrothermal thruster, incorporating two-temperature, non-equilibrium effects, is presented. This model includes the complete system of both the Maxwell equations and the Navier-Stokes equations for the case of a helium flow with different electron and heavy species temperatures, with finite rate ionization and excitation kinetics including 12 electronimpact reactions and Penning ionization, with routines for calculating transport properties of heavy particles and electrons using kinetic theory, and with a finiteelement solver for calculating heat transfer through the nozzle. Results from a simulation of the thruster are presented, involving a 220 mg/sec helium flow, with 4 kW of energy addition in the plenum section. This model is shown to give predictions of both the peak electron temperature (15,100 K) and the radial electron temperature profile, which are closer to the available data, than previous equilibrium models.