Magnetohydrodynamics simulation on the efficiency enhancement of electrodeless Lorentz force thrusters through traveling-wave acceleration

The electrodeless Lorentz force (ELF) Thruster is a novel electric propulsion concept that utilizes a Rotating Magnetic Field (RMF) driven Field Reversed Configuration (FRC) plasmoid to produce pulsed thrust, aimed at high-power applications. To address the substantial energy loss and low efficiency observed in the experiments, this study employed a two-dimensional Hall Magnetohydrodynamics (MHD) model to numerically analyze the acceleration dynamics of FRC plasmoids in an ELF thruster and assess the effectiveness of the traveling-wave acceleration method. The model is validated through direct comparison with the thruster test data. Analysis of the force distribution reveals a decline in the axial Lorentz force downstream. To overcome this, traveling-wave acceleration through bias field modulation is proposed and evaluated, strengthening the bias field coil to form a wave of magnetic strength gradient to accelerate the plasmoid further. Based on experimental parameters, this method achieves a 50 % increase in exhaust velocity and total momentum with only a 30 % increase in input power, without modifying the RMF parameters. The plasma efficiency more than doubles, and energy loss is reduced due to shortened plasmoid residual time, demonstrating the effectiveness of traveling-wave acceleration as a power-efficient strategy for enhancing ELF thruster performance. Plume simulations indicate over 90 % divergence efficiency, attributed to the frozen-in magnetic field lines that facilitate narrow-angle exhaust.