Numerical Simulation of Microwave-Sustained Supersonic Plasmas for Application to Space Propulsion ∗ V.P. Chiravalle † , R.B. Miles ‡ , and E.Y. Choueiri § Princeton University, Princeton, New Jersey 08544 AIAA-2001-0962 ¶ Abstract The concept of adding energy to an expanding super- sonic flow using a microwave-sustained plasma is ex- plored numerically by solving the complete system of both the Maxwell equations and the Navier Stokes equations for the case of an argon flow in a realistic thruster geometry. Results show that when an addi- tional amount of power, equal to 45 % of the power deposited in the plenum, is added to the supersonic flow a toroidal plasma forms, but only a 3 % increase in specific impulse is achieved. It is concluded that future work relating to this concept should concen- trate on finding ways to confine the plasma to the cen- terline. * This research was funded by an AASERT grant from AFOSR with additional support from NSF. † Graduate Student, Mechanical & Aerospace Engineering, AIAA ‡ Professor, Mechanical & Aerospace Engineering, Associate Fellow AIAA § Assistant Professor, Mechanical & Aerospace Engineering, Senior Member AIAA ¶ Presented at the 39 th AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, January 8-11, 2001. Copyright by au- thors. Published by the AIAA with permission. 1 Introduction 1.1 Motivation The conventional approach for electrothermal space propulsion systems has been to heat a propellant gas to a high temperature in the plenum and then to ex- pand the flow in a nozzle and produce thrust. Exam- ples of such systems are resistojets, arcjets, and mi- crowave electrothermal thrusters. For all these sys- tems, the specific impulse is limited to the maximum average temperature that can be achieved by heating a low molecular weight propellant in the plenum. For a state of the art 2 kW hydrazine arcjet the specific impulse is roughly 600 sec[1]. Both arcjets and mi- crowave electrothermal thrusters make use of a high temperature plasma to heat the flow. The plasma in an arcjet is sustained by electric current emitted from a cathode; in the case of a microwave elec- trothermal thruster, microwave energy is used to sus- tain the plasma. The fact that a microwave-sustained plasma can be created without electrodes and can be maintained away from the material surfaces of the thruster, may allow for large reductions in thruster erosion and significant improvements in overall life- time, compared with arcjets. From a fundamental point of view the maximum average temperature that can be achieved for a given propellant in a microwave 1