The evolution of a 1 Newton monopropellant thruster utilizing 87.5 % concentration hydrogen peroxide is reported. The design of the thruster is described, along with the testing of the catalyst material. Thruster firings were completed at sea-level atmospheric conditions and in vacuum, with a vacuum specific impulse of 160 seconds and a characteristic velocity efficiency of greater than 95 % achieved. The final thruster design demonstrated good overall performance, with initial lifetime testing suggesting that the catalyst offers good robustness. A case study suggests that the thruster would provide a level of performance comparable to that of a hydrazine-based propulsion system for a high velocity-change, volume-constrained Low Earth Orbit spacecraft mission, but at lower cost.

Experimental testing of a number of novel additively manufactured monopropellant micro-thrusters was conducted under atmospheric conditions, using 87.5% concentration hydrogen peroxide. The aim of this work was to select a specific catalyst bed geometry for the thruster system, and to investigate more general methodologies for monopropellant packed catalyst bed optimization. Characteristic velocity efficiencies approaching 0.98 were demonstrated, and performance improved for smaller beds with low aspect ratios, although these beds flooded at lower propellant flow rates. The onset of bed flooding was used to identify physical limits of propellant flow rate supported by the catalyst. The particular propellantcatalyst pairing limit was defined by a Damköhler number of 56, independent of the bed geometry, with thermal performance peaking for the high flow rates just before flooding occurred. It is suggested that this method is extensible to other monopropellant systems, although with further work required to confirm it is a more general effect beyond thrusters using hydrogen peroxide.

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