High Burn Rate Hybrid Fuel for Improved Grain Design

A novel type of fuel providing high burning rate for hybrid rocket applications is proposed. 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 thus creates local pockets in the polymer surface, where the particulate fuel is exposed, and maintains the rough surface structure as the dispersed particles are continually exposed. Secondary effects include decreased phase change enthalpy of the mixture, relative to a conventional polymer fuel, and the potential for increased specific impulse by inclusion of high energy compounds as the dispersed phase. This high burn rate fuel will enable increased propellant mass fraction in hybrid rockets, by decreasing the number of ports required to achieve the desired net fuel combustion rate. It also simplifies the technology and retains the relatively high strength and good storage stability of polymeric fuels.