ABSTRACT
This chapter discusses several kinds of solid, liquid, and hybrid chemical propellants have been devised over the years. Chemical propellants can be classified according to their respective physical states, namely, liquid, solid, gel, or hybrid. All types of chemical propellants based on physical entity have their own desirable characteristics for high-level performance. Solid propellants fall mainly into two categories: homogeneous and heterogeneous propellants, depending upon the physical entities of fuel and oxidizer in the propellant. Generally, oxidizers like AP and metallic fuels like aluminum are added to the fuel-rich double base (DB) propellants that reduce its fuel-richness and improve its performance. Liquid-propellant rocket engines in spite of inherent complexities are preferred over the solid-propellant engines due to the added advantages of liquid propellants. Some examples of liquid oxidizers are hydrogen peroxide, nitric acid, liquid oxygen, ozone, nitrogen peroxide, liquid fluorine, chlorine trifluoride, chlorine pentafluoride, nitrogen trifluoride, and oxygen difluoride.
