Design, fabrication and test of a solid propellant microthruster array by conventional precision machining

Prototypes of 10 × 10 and 100 × 100 scale solid propellant microthruster(SPM) array were fabricated with conventional precision machining, due to restriction on the manufacture of large-scale microthruster array with present MEMS manufacturing technique. The microthruster consists of ignition circuit layer, ignition powder layer, propellant layer, cavity layer and nozzle layer. Row–column driving control plan was applied in ignition circuit to realize simultaneous ignition and reduce the number of wires. The solid propellant was AP-HTPB pellet propellant with a diameter between 100 μm and 200 μm. A test to choose proper ignition powder was performed among black powder, modified back powder and self-made ignition powder, which demonstrated the reliability of self-made ignition powder and realize 100% ignition success rate. In the mean time, a measurement of ignition resistor's surface temperature was taken to determine ignition delay, together with numerical simulation and ignition resistor fusing test. Thrust was also measured for the 10 × 10 scale microthruster array, and the results show that the specific impulse is much lower than calculated result, so a more comprehensive numerical model is in need to depict the working process of a single SPM. The test also demonstrates the feasibility of large-scale solid propellant microthruster array's fabrication by conventional fabrication methods.