Influence of Initial Propellant Temperature on Solid Rocket Internal Ballistics

Abstract

The influence of initial propellant temperature on solid propellant rocket motor performance is examined in the present study, with the focus primarily on predicted steady and nonsteady burning rate behavior. The present evaluation includes an examination of quasi-steady burning of a conventional composite propellant under pressure, core flow (erosive burning), and normal acceleration (say, due to motor spinning). The most direct and well-known influence of initial propellant temperature is on the pressure-dependent burning rate. The pressure-dependent burning rate, as the base burning rate, in turn influences the degree of augmentation seen under core flow and normal acceleration; in general, the lower the base rate, the higher the augmentation. The explicit presence of initial propellant temperature in various model equations for the flow- and acceleration-dependent burning components, and the corresponding effect of the initial temperature on the propellant’s burning surface temperature, can produce an overall compounding effect that adds to the nominal augmentation produced by the base burning rate value. The same considerations apply when one moves from quasi-steady to transient operational conditions, where the transient burning rate response of the solid propellant (which is a function of the quasi-steady burning rate components, as well as the initial temperature of the propellant) can be modified significantly by varying the propellant’s initial temperature.