Thrust noise suppression of a micro direct current ion thruster

Space-based gravitational wave detection requires micro-propulsion systems to achieve thrust noise below 0.1 μN/√Hz in the 1 mHz–1 Hz band. To meet the high-precision demands, this paper develops and experimentally validates a closed-loop control strategy for a 3 cm micro direct current (DC) ion thruster. First, the thrust is measured with a micro-thrust stand, and the thrust calculation formula is refined by combining the current and voltage data with these measurements. This approach provides a reliable feedback signal for real-time control. The dynamics of the transfer path from screen grid voltage to thrust are then analyzed. Based on this analysis, a PID controller with the screen grid voltage as the adjustable parameter was designed, and the optimization design and parameter tuning were carried out. With the optimized PID controller, the engineering prototype achieves a maximum thrust noise of 0.0902 μN/√Hz over the 1–50 μN thrust range in the frequency band from 1 mHz to 1 Hz. The findings demonstrate that micro-DC ion thrusters are capable of ultra-low-noise performance for future gravitational wave detection missions.