Global Energy Transfer Model of a Microwave Electrothermal Thruster Operating With Helium Propellant at 2.45-GHz Frequency

Microwave electrothermal thruster (MET) is a type of space propulsion system that uses free floating plasma to heat the propellant gas. This paper presents a 0-D model that investigates the energy transfer from the electromagnetic wave to the propellant gas via atmospheric pressure plasma, and evaluates the steady-state plasma properties of an MET thruster. In the model, governing equations for electron particle balance, electron energy, balance and heavy particle energy balance equations are solved to obtain the plasma parameters. Electron temperatures of around 1 eV, electron number densities of $10^{19}~\#/\text {m}^{3}$ , and heavy particle temperatures of about 3000 K are evaluated for the free floating plasma inside the MET resonant cavity for 1200-W delivered power at 2.45-GHz frequency. Obtained solutions are in good agreement with the experimental results from the literature. Along with the plasma parameters, rocket performance parameters, and specific impulse and thrust are computed. The developed model is also used to predict the plasma and performance parameters of a prototype MET system developed at the Bogazici University Space Technologies Laboratory.