High performance microthruster with ammonium-dinitramide-based monopropellant

A high performance environmentally friendly ammonium dinitramide (ADN) based liquid monopropellant was used to develop a thruster with improved performance compared to a conventional hydrogen peroxide propellant microthruster. Compared to regular thrusters, microthrusters have high heat loss due to the higher reactor surface area to volume ratio. A high enthalpy propellant needs to be used to increase the decomposition temperature in order to enhance the thruster performance. There is a need to increase the heat tolerance of the catalyst given the increased reactor temperature. A lanthanum doped Pt/Al2O3 catalyst was fabricated and applied to increase the heat resistance performance against the ADN-based propellant with a theoretical adiabatic decomposition temperature of 1630 °C. The microthruster was manufactured using a MEMS process. A total of five layers of photosensitive glass with different shapes were fabricated by wet etching and stacked and adhered, and sensors were assembled to measure the pressure and temperature. A combustion experimentation was carried out. 90 wt.% hydrogen peroxide was injected in advance for catalyst preheating and then the ADN-based propellant was injected. In the experimental results, ignition was observed within the reactor and the combustion temperature was 983 ℃. The thrust and specific impulse performances were obtained. Compared to a microthruster using 90 wt.% hydrogen peroxide, the ADN-based propellant enhanced thrust by 19% while the specific impulse increased by 86%.