Investigation on acceleration process of field reversed configuration plasmoid in an electrodeless Lorentz force thruster using Magnetohydrodynamics simulation

Abstract

Rotating Magnetic Field (RMF) driven Field Reversed Configuration (FRC) plasmoid, originating from magnetic confined fusion research, has been developed as a novel propulsion method for high-power electric thrusters, namely the electrodeless Lorentz force (ELF) thruster. To address the dilemma between the high potential in theory and the low performance in the experiment, this paper numerically investigates the acceleration processes of FRC plasmoid in ELF thruster through a two-dimensional Hall Magnetohydrodynamics method. Direct comparisons with experiments have been made to verify the model. The correlation between the plasma behavior and the thruster performance has been obtained, providing insight into the experimental phenomena. The power scaling rule of thruster performance is obtained by investigating the influence of magnetic field strength and thruster geometry on the exhaust velocity and momentum of the FRC plasmoid. The simulation revealed that the low thruster performance in recent experiments is due to the low power input. High performance is expected to be achievable by scaling up the input power to hundreds kW or MW levels. Increasing the bias field to more than 1000 G, RMF frequency to 1 MHz, and RMF strength to hundreds Gausses, enables a per-shot momentum of mNs level of and specific impulse to be more than 5000 s. Additionally, the contribution of gas pressure force and Lorentz body force to the plasmoid acceleration has been analyzed, showing that the magnetic forces are dominant in high power regime, whereas gas forces being dominant in low power regime. The power scaling rule and geometry design principle formed in this work can help improve the ELF thruster performance, highlighting the necessity of testing prototypes under high-power conditions.