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.