Ageing studies on AP/HTPB based composites solid propellants

Abstract

Abstract Components of solid rocket motor that are susceptible to ageing are propellant, insulator, inhibitor, interfaces, igniter system, and seals. Seals, insulator, ignition systems are replaceable but the motor would be recast when the deterioration in propellant and liner are beyond specified limits due to the ageing. There is a large body of literature available on the ageing of composite solid propellant, each focusing only on a particular type of ageing in propellants rather than having a synergistic view of the various different ageing processes and hence the literature looks disconnected. Further, there are a few studies which are still classified and are one of the reasons for the above disconnect. This review paper is an attempt towards establishing the bridge among these studies. Different types of ageing: physical, chemical ageing, hygro-chemical ageing and the deterioration associated with cumulative damage have been discussed in detail. The ageing related deterioration plays an important role in the safe-life estimation of solid propellant based rocket motor. Therefore, sources and mechanisms of ageing have been explored and their associated effects on the propellant properties (physical and mechanical) are also described. A summary on accelerated ageing methods which are typically followed to study thermo-chemical ageing of propellants is presented in this paper. Studies related to the degradation of propellant-liner interface are also reviewed. Advances in health monitoring (passive and active) of stored grains have been visited. Further, the gap in propellant ageing research have been identified and suggestions are provided for the future research.