Hypergolic Continuous Detonation with Space-Storable Propellants and Additively Manufactured Injector Design

Abstract

Initiation and sustained detonation of hypergolic liquid rocket propellants have been assessed in an annular combustor. An established impinging injector design was modified for additive manufacturing to improve hydraulic characteristics. Computational fluid dynamics analysis was used to verify decreased flow resistance and increased relative backflow resistance afforded by tapered propellant passageways enabled by additive manufacturing. Two injectors were manufactured and a honing process was employed on one of the injectors to reduce surface roughness associated with additive manufacturing. Cold-flow testing confirmed decreased hydraulic resistance due to tapering of the injector passageways and due to the honing process. The detonability of hypergolic space-storable propellants in an annular combustor with the injectors was assessed experimentally with dinitrogen tetroxide as the oxidizer and monomethylhydrazine as the fuel. The presence of rotating detonation waves was verified via multiple instrumentation methods, including a high-speed camera. The performance of the combustor was seen to increase with the total number of detonation waves, the total propellant flow rate, and the presence of a downstream flow constriction. The work demonstrates continuous detonability of hypergolic space-storable propellants under various operation conditions relevant to in-space rocket propulsion concepts, as well as several benefits of utilizing additive manufacturing for injection-system design.