Green Propulsion: Catalysts for the European FP7 Project GRASP

The Green Advanced Space Propulsion (GRASP) project investigated the issue of green propulsion and the possibility of replacing presently used toxic hydrazine propellant by green propellants. This project was financed by the European Commission in the 7th Framework Program (FP7). A large data base of about 100 green propellants was compiled including physical and material properties, toxicity and performance data. A preliminary selection was conducted to identify the most promising green propellant candidates for experimental work. Catalytic ignition, a very simple and robust subsystem with restart possibility, was thoroughly investigated focusing on the catalyst–propellant couple. For the whole project, more than 50 catalyst variations have been prepared comprising ceramic pellets, ceramic monoliths, metallic foams or gauzes. Very promising green propellant candidates, e.g. ammonium dinitramide-based monopropellants, have been methodically investigated leading to the development and manufacturing of advanced pellet-based catalysts for ionic liquid decomposition. The decomposition of concentrated hydrogen peroxide (87.5 wt%) for bipropellant applications led to a thorough investigation of monolithic catalysts. Examination of monolith parameters (channel shape, channel density, material) and preparation parameters (washcoating procedure, active phase precursor) led to the development of very efficient catalysts showing high activity and stability: 17.9 kg of H 2 O 2 could be decomposed for the first time by a single monolithic catalyst.