Experimental Characterization of a 5 N Hydrogen Peroxide Monopropellant Thruster Prototype

In the framework of the LET-SME program funded by the European Space Agency, ALTA S.p.A. (Italy) and DELTACAT Ltd. (United Kingdom) jointly investigated the use of advanced catalytic beds on ceramic supports as a cost-effective alternative to metal screen reactors for the decomposition of high-concentration hydrogen peroxide in small monopropellant rockets. To this purpose ALTA S.p.A. designed and realized a reconfigurable test bench for the characterization of the operation and propulsive performance of small rocket thrusters. The present paper illustrates the experimental campaign carried out on a 5 N thruster prototype operating with two platinum catalysts on g− alumina supporting spheres, especially developed by ALTA in collaboration with the Chemistry and Industrial Chemistry Department of Pisa University, Italy. The results indicated that Pt/Al2 O3 is an effective catalyst combination for the decomposition of 87.5% propellant grade hydrogen peroxide, with good stability and performance comparable to silver screen beds of equal geometric envelope and operational conditions. Incomplete hydrogen peroxide decomposition and the onset of flow oscillations in the reactor were observed at the tested levels of bed loading, residence time and flow pressure. Thermal stresses due to the large temperature gradients occurring during the decomposition of high grade hydrogen peroxide (87.5% by weight) caused the ceramic pellets to break and the progressive occlusion of the bed. Based on the analysis of the test results, several ways to overcome these problems in future investigations have been tentatively identified, together with the necessary modifications to the present experimental set-up.