Fabrication of a liquid monopropellant microthruster with built-in regenerative micro-cooling channels

- The use of micro-cooling channels to cool a liquid propellant microthruster is suggested.
- A liquid propellant microthruster with micro-cooling channels was fabricated with a photosensitive glass MEMS process.
- The feasibility of using micro-cooling channels was successfully validated through the design, fabrication and testing of a liquid propellant microthruster.

This paper reports a feasibility study of regenerative micro-cooling channels in a liquid microthruster composed of thermally fragile materials. Glass, which is among the most thermally insulating materials, has been used as microthruster fabrication material to suppress excessive heat loss in micro scale thruster. However, the frangibility of glass has remained a challenge to be solved. To thermally manage the fragile structure, the use of regenerative micro-cooling channels in a microthruster is suggested in this work, and the feasibility was tested through design, fabrication and experimental performance of a glass microthruster with microchannels. Nine photosensitive glass layers were wet etched and integrated to fabricate the microthruster. Before integration of the layers, a fabricated Pt/Al2O3 catalyst was inserted into the chamber of the microthruster for propellant decomposition. Hydrogen peroxide (90 wt%) was used as a monopropellant and served as the working fluid for regenerative cooling. A liquid microthruster with micro-cooling channels was successfully fabricated with a photosensitive glass MEMS process. Experimental performance tests were conducted while measuring the microthruster chamber pressure, chamber temperature, and surface temperatures. The test results showed normal operation of the microthruster, which had an estimated thrust of approximately 48 mN and temperature efficiency of approximately 41%. The decreasing surface temperatures of the microthruster during thruster operation successfully validated the cooling effect of the micro-cooling channels and demonstrated their practicality for the regenerative cooling of liquid microthrusters.