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.