Nitrous Oxide Propulsion System

The Nitrous Oxide Propulsion System (NOPS) is a new Extravehicular Mobility Unit (EMU) thruster concept using nitrous oxide as a monopropellant. Liquid monopropellants are often used in propulsion systems where simplicity of design, restartable/control on demand, and repeatability is desired. Unfortunately, many monopropellants are toxic and dangerous, ruling them out for EMU thruster application. Thus, EMU thrusters have relied upon cold gaseous nitrogen, which offers very low specific impulse and propellant mass fraction. A NOPS, however, uses nitrous oxide, a readily available safe and storable propellant which is not toxic, has performance comparable to hydrazine, and does not decompose spontaneously like hydrogen peroxide. Furthermore, Pioneer Astronautics has demonstrated a system that decomposes N2O into a breathable mix of oxygen and nitrogen. Thus, for example, an EMU propelled by a NOPS system would provide an astronaut with a large emergency backup supply of oxygen. Such a dual use system could also have great utility as the propulsion system for manned spacecraft, such as the International Space Station or the Space Shuttle, where safety is paramount and breathing gas reserves are desired. Replacing current liquid monopropellant thrusters with NOPS units would greatly reduce ground processing time and costs, while providing comparable performance.