Design and Experimental Validation of a Piezoelectrically Controlled Micro-Newton Cold-Gas Thruster Head

Micro-Newton cold-gas thrusters are promising actuators for precision space missions, but their performance is strongly influenced by the integrated head architecture. This study presents the design, fabrication, and experimental validation of a piezoelectrically controlled cold-gas microthruster head for space-based gravitational-wave detection missions. The proposed head integrates a cone-needle throttle, a micro-orifice interface, and a downstream micro-nozzle, thereby converting actuator displacement into a regulated mass flow and ultimately into thrust. One-dimensional theory was first used for preliminary sizing, and Direct Simulation Monte Carlo (DSMC) analysis of the complete throttle-nozzle geometry was then applied to determine the final design parameters under rarefied-flow conditions. The selected design uses a throat radius of 29 μm and a needle half-angle of 10 degrees. Following fabrication and structural characterization, the integrated device was validated through mass-flow calibration and vacuum thrust testing. The experimental results show that the pressure-decay-based calibration provides a consistent mapping between actuation command, calibrated flow rate, and thrust output. The measured flow–thrust relation preserves the high linearity predicted by simulation, while the experimentally evaluated specific impulse meets the specified design target over the tested range. In addition, thrust-resolution testing at a baseline thrust of approximately 98.4 micro-Newton demonstrates a minimum resolvable step of 50 nano-Newton, and the measured thrust-noise amplitude spectral density remains below 0.07 micro-Newton/sqrt(Hz) over the 10 mHz–1 Hz band for the tested thrust levels. These results support the feasibility of the proposed integrated cold-gas microthruster head and its device-level validation approach for future space-based gravitational-wave detection applications.