NUMERICAL INVESTIGATION OF BLUFF-BODY STABILIZED MICROWAVE PLASMAS

Microwave heating of gases for space propulsion applications is addres sed analytically by means of coupled solutions of the Navier-Stokes an d Maxwell equations. The model is validated using experimental measure ments of bluff-body stabilized microwave plasmas sustained in a resona nt cavity. The size, shape, and location of the plasma are reasonably Hell-predicted, as are its overall thermal efficiency coupling efficie ncy, and peak temperature. Parametric trends such as the effect of pow er and mass flow variations on thruster performance verify that tile m odel incorporates the dominant physical processes of the plasma-fluid- dynamic interaction, In addition, the predictions indicate that the si ze of the plasma strongly influences the plasma temperature and its ab sorption characteristics. proper design of the flow tube/bluff-body co nfiguration enables tile control of the plasma size and, hence, the pl asma characteristics. This enables high-coupling efficiencies to he ob tained at high po,rer levels and, along with control of the mass flow to minimize wall heat, high thruster performance may be realized. Prel iminary efforts to maximize performance resulted in specific impulse p redictions of 600 s. Additional work is needed to identify methods for increasing the peak powers and to study size scale-up issues.