Thermal analysis and coupled thermo-electrical-mechanical characterization of a sub-micro-Newton indium field emission electric propulsion micro-thruster for space-borne gravitational wave detection

To meet the stringent drag-free control requirements of space-borne gravitational wave detection, this study develops a sub-micro-Newton indium field emission electric propulsion (In-FEEP) micro-thruster with a single-needle emitter. The mechanisms of emitter thermal effects influence field emission characteristics are systematically investigated. A combined numerical-experimental framework is proposed for cross-consistency verification of the coupled thermal-electrical-mechanical challenges in performance characterization, enabling quantitative mapping from temperature fluctuations to thrust variations. Theoretical modeling and finite-element simulations are employed to determine the key structural parameters. A harmonic analysis based on the linear control method is introduced to predict the emitter surface temperature, yielding deviations of 2.03–14.18 % compared with electrical-parameter-based estimation. This level of deviation contributes less than one to two orders of magnitude to the overall thrust noise. Experimentally, an integrated temperature-field and micro-thrust estimation scheme is implemented, significantly improving ignition stability and control accuracy. The fabricated thruster achieves a thrust range of 0–10 μN, with a resolution better than 0.05 μN in the lower half and 0.1 μN over the full scale. Thrust noise remains below 0.1 μN/√Hz across the majority of the critical low-frequency band of 10 −4 –0.5 Hz (99th percentile). By integrating thermal-electrical-thrust modeling that is experimentally supported through cross-method consistency checks with precision testing, this work provides a practical foundation for implementing tunable, low-noise FEEP systems in upcoming gravitational wave observatories, and offers insights into the coupling of local thermal mechanisms with overall system performance in micro-propulsion applications.