Vapor Containment and Fire Suppression System for Hypergolic Propellants

Toxicity and fire risks associated with monomethylhydrazine and nitrogen tetroxide must be mitigated for the continued fielding of divert and attitude control systems for MDA interceptors. In a Phase I study, IN Space, Ansul and Purdue University characterized a system allowing for simple retrofitting of propulsion systems already designed for the hypergols of interest. With the proposed Vapor Containment and Fire Suppression system, advanced sensing techniques detect a propellant leak and then trigger the injection of a persistent, rapidly expanding foam to extinguish fires and contain propellant vapors to acceptable levels. Experiments led to the identification of a foam capable of containing monomethylhydrazine vapors below 0.2 ppm for 8 hours and nitrogen tetroxide vapors below 1 ppm for 7 hours. This and other evaluated foams exhibit significant potential for improvements in containing vapors, extinguishing hypergol fires, and potentially neutralizing the propellants. In Phase II, the team, strengthened by Northrop Grumman and the capabilities of the NASA White Sands Test Facility, will continue the development and evaluation of candidate foams in lab- and field-scale tests. Detailed prototype designs for naval and portable interceptor systems will be generated using the information gained through development and experimentation.