Numerical Study of a Novel Resonant Plasma localization approach for Microwave Electrothermal Thrusters*

Microwave electrothermal thrusters (METs) are promising propulsion systems for space missions due to their high specific impulse and power compatibility. METs use microwave energy to heat propellant to generate thrust. However, a challenge in METs is the plasma discharge deviating from the nozzle entrance, leading to energy losses and inefficient conversion of microwave energy. This behavior is primarily attributed to their electrodeless configurations. To address this challenge, we propose the integration of all-dielectric resonators into METs. These resonators are comprised of solid dielectric materials that efficiently localize and manipulate electromagnetic wave energy. In this study, we examine different configurations of a 2D planar computational model, focusing on the impact of varying shapes and sizes of the dielectric resonators on the operation of METs. The electric field distribution within METs is crucial for electron Joule heating, which is the primary mechanism for gas heating. Concentrating the highest electric field strength near the nozzle throat enables the gas flowing through it to be heated, resulting in higher nozzle exit velocity. This study aims to understand the interactions between the resonator and propellants, particularly focusing on microwave energy absorption, and how they affect thrust generation and exhaust characteristics. The goal is to demonstrate how these interactions contribute to achieving higher specific impulse and enhanced efficiency in METs.