Variable Thrust Hybrid Propulsion for Mission Flexibility

A novel type of high burning rate hybrid rocket fuel is an enabling technology for a wide range of DoD rocket propulsion applications. This fuel system has been demonstrated to provide burn rate at least four times that of conventional polymers, while retaining the physical properties and specific impulse capability of HTPB based fuels. The result is a high density impulse capability utilizing storable propellant combinations, while eliminating environmental hazards. This fuel maintains a hydrodynamically rough surface to radically enhance convective heat transfer rate, and hence the fuel burn rate. This is achieved by incorporating a particulate fuel material dispersed within a continuum phase polymer matrix. The dispersed fuel material is chosen to transition from solid to gas much more readily than the polymer matrix, and with a particle size scale sufficiently large that the resulting surface voids provide a hydrodynamically rough surface. Combustion of this fuel system maintains the rough surface as theparticles are continually exposed. Secondary effects include increased surface area; decreased fuel phase change enthalpy; and potential for increased specific impulse by inclusion of high energy compounds. The high fuel burn rate enables increased propellant mass fraction while retaining the strength and storage stability of polymeric fuels.