Nitride and carbide of molybdenum and tungsten as substitutes of iridium for the catalysts used for space communication

Satellites are equipped with microthrusters that control their orbit and attitude. The thrust is achieved by the catalytic decomposition of hydrazine by iridium supported on alumina. As nitrides and carbides of molybdenum and tungsten behave like noble metals in many catalytic reactions, they were tried in a 2 newton hydrazine microthruster. Their performance was similar to that of the iridium catalyst, with respect to ignition delay and thrust. Their mechanical resistance appears higher than that of iridium-based catalyst. This application is the first practical one for nitrides and carbides of early transition metals as substitutes of noble metals, a possibility first reported in 1973. This revised version was published online in July 2006 with corrections to the Cover Date.