Nontoxic Hydroxylammonium Nitrate (HAN) Monopropellant Propulsion

Abstract

Nontoxic monopropellants have been developed that provide better performance than toxic hydrazine. Formulations based on HAN have superior performance as compared to hydrazine with enhanced specific impulse (Isp), higher density and volumetric impulse, lower melting point, and much lower toxicity. However, HAN-based monopropellants require higher chamber temperatures (2,083 K vs. 883 K) to combust. Current hydrazine-based combustion chamber technology (Inconel® or niobium C103 and silicide coating) and catalyst (Shell 405) are inadequate. In Phase I, state-of-the-art iridium-lined rhenium chambers and innovative new foam catalysts were demonstrated in pulse and 10-second firings. Phase II developed and tested a flight-weight thruster for an environmentally green monopropellant.