Diaphragm Material Optimization for Monopropulsion Systems for Spacecraft

Propellant tanks with elastomeric diaphragms have been used to provide positive propellant expulsion since the mid-1960s. The materials used in existing diaphragms have been optimized for hydrazine. However, because of the toxicity and costs of associated with handling hydrazine, the USAF has developed non-toxic alternatives such as hydroxylammonium nitrate (HAN)-based monopropellants for next-generation propulsion systems. Under the proposed program, METSS will develop new diaphragm materials for use in positive expulsion propellant tanks that can support long-term storage and expulsion of HAN-based monopropellants. The new diaphragm materials will provide consistent and reliable performance in HAN-based energy systems, over a projected service life of 20 years, and be compatible with existing engineering design and environmental performance criteria, including rocket transport, launch, and operational requirements. Manufacturability and maintainability will be considered, as these factors have a significant impact on technology transition and overall system costs. The proposed efforts will leverage previous work conducted by METSS to support fuel storage delivery in next-generation propulsion systems for unmanned, underwater vehicles requiring liquid fuels and oxidizers. A critical factor in the success of this project was a design approach that allowed for the use of separate materials to address chemical resistance and mechanical performance requirements.