Metals, Energetic Additives, and Special Binders Used in Solid Fuels for Hybrid Rockets

Abstract

R low mass and linear regression rates of solid fuels have been among the major drawbacks of classical hybrid rocket engine technology due to low density, inertness of conventional solid fuels, and the diffusion-controlled combustion process. The thermal degradation in the pyrolysis process of inert polymeric fuels has been considered to be one of the key processes occurring in hybrid rocket engines and solid-fuel ramjet engines [1]. The fuel-surface regression rate generated by this process is a very important design and performance parameter and is strongly affected by the operating conditions and the composition and thermophysical properties of the solid fuel. In addition, fluid dynamic, heat-transfer, and combustion processes in these solid-fuel systems are characterized by complex interactions involving numerous physical phenomena, simultaneously taking place in the combustion chamber and the fuel grain. These complex interactions include solid-fuel pyrolysis; metal vaporization for metallized solid fuels; oxidizer atomization and vaporization; gas-phase species mass diffusion; mixing and combustion between the fuel-rich and oxidizer-rich species; turbulent flow with mass addition; conductive, convective, and radiative energy transfer; and time-varying