PROPULSION AND CATALYSIS - HISTORICAL SURVEY, UP-TO-DATE OVERVIEW, AND CURRENT CHALLENGES

Abstract

This review presents a survey on the application of catalysis to propulsion. The first application was developed for the decomposition of concentrated aqueous solutions of hydrogen peroxide before WWII in Germany (He-176 plane, V1 and V2 rocket programs, torpedoes, and submarines). After WWII, the UK Black Knight rocket program associated kerosene with H2O2 and a silver screen catalyst bed. The beginning of the space programs led to the replacement of H2O2 by more stable hydrazine, using Ir/Al2O3 catalysts, for satellites and launchers. In recent years, hydrazine substitutes (called "green propellants") have been proposed to satisfy new environmental concerns, improve performance, and reduce cost. The most studied substitutes are energetic aqueous ionic mixtures containing an ionic oxidizer and a fuel. Commonly studied oxidizers are hydroxylammonium nitrate or ammonium dinitramide. The current challenge is to develop a catalyst that is active at low temperatures and able to sustain the high temperatures of the product gases. Other candidates that have also been proposed include highly concentrated hydrogen peroxide (90−98 wt-%) and nitrous oxide N2O(g). Other applications of catalysis to propulsion are: (1) hybrid engines, which could use a liquid oxidizer that would be able to burn a solid fuel, after catalytic decomposition; (2) hypergolic bipropellants with a soluble catalyst in the fuel; (3) catalytic cracking of endothermic fuel for hypersonic jets or for air breathing pulse detonating engines; (4) catalytic ignition of cryogenic H2−O2 mixtures; or (5) as a catalyst to modify burn rates for solid propulsion.