Effect of Accelerated Cyclic Aging on the Ballistic Properties of Composite Solid Propellant

Abstract

Burn rate is a vital parameter of a propellant that highly influences the internal ballistics of a rocket motor. In the case of military applications of solid rocket motors, they are stored for a long duration, during which their performance deteriorates considerably due to aging. Conventionally, the accelerated isothermal technique is used for studying the effects of aging. However, in actual storage conditions, the temperature experienced by the propellant varies over time. In the present work, experimental investigations were carried out using accelerated cyclic and isothermal aging schemes. Here, the burn rates and temperature sensitivity of the propellant were recorded after the accelerated aging. A reduction in burn rates was observed in all aging techniques. There was a strong influence of the frequency of the aging cycle on burn rates. Theoretical analysis of motor performance indicates a reduction in chamber pressure to the tune of 18%, leading to deterioration of thrust by 20% and specific impulse by 2.5%. Remedies to recover the performance of the motor with aged propellant were explored, and throat inserts and thermal conditioning of aged motors were suggested as possible ways to overcome the aging effects.