Solid-propellant grain-to-case bond-stress measurement

Abstract

To satisfy the need for better definition of solid rocket-motor grain stress state, a through-the-case bond-stress gage^* which provides for measurement of the radial stress induced at the propellant/liner/case interface during environmental-temperature variations has been developed. This paper describes a study^† designed to evaluate theoretical approaches to grain stress analysis using experimental data from these gages. Four analog motors were cast with cylindrical-bore propellant grains in steel sleeves using a mechanically characterized solid propellant. The analog motors were exposed to thermal changes typical of prototype rocket motors. Radial stresses at the propellant-case interface were monitored using the stress gages during propellant cure and subsequent thermal testing. Correlation of the monitored results with state-of-the-art analytical methods reveals the need for improved analytical treatments and further application of experimental techniques.