Indirect Thrust Measurement of the MP2S Pulsed Magnetoplasmadynamic Thruster

Pulsed, gas-fed electric propulsion systems are a promising option for future small satellite missions but pose significant challenges for accurate thrust characterization due to parasitic forces introduced by propellant feed lines. This paper presents and experimentally demonstrates an indirect thrust measurement methodology for a pulsed quasi steady-state magnetoplasmadynamic thruster prototype of the Modular Pulsed Propulsion System (\name). The thruster plume is directed onto a graphite target mounted on a high-precision thrust balance, decoupling the balance mechanically from the gas supply system. Since the impulse transfer between the argon plume and the target is unknown, it is quantified using LAMMPS molecular dynamics simulations to obtain an impulse transfer correction factor. The impulse bit is measured using nanometer-resolution pendulum displacement measurements processed via sinusoidal curve fitting and wavelet filtering. A comprehensive uncertainty analysis based on Gaussian error propagation is performed, accounting for calibration, sensor resolution, geometry, timing, frequency determination, damping, and impulse transfer. The methodology is used to determine impulse bit, specific impulse, and thrust efficiency of the \name, demonstrating thrust levels significantly above the cold-gas contribution alone, identifying distinct discharge modes, and outlining the design and operational changes required to approach the targeted performance.