Online structural integrity monitoring of high-performance composite rocket motor casing

Abstract

Solid rocket motor (SRM) is one of the significant sub-systems for aerospace launch vehicles. The requirements of high range and high payload capabilities in aerospace systems demand the usage of high specific strength and high specific stiffness materials for rocket motor casings to minimize the inert weights. The present state-of-the-art technology is to realize stages of missile systems/launch vehicles with Composite Rocket Motor Casing (CRMC) to have a high-performance factor. CRMC is being designed with a marginal Factor of Safety (FOS) and mostly for a one-time use during its service life. CRMC is pressure tested to verify leak containment and its ability to sustain the Maximum Expected Operating Pressure (MEOP). Acoustic Emission Testing (AET), an online and global Structural Health Monitoring (SHM) technique along with strain and dilation measurement is used for observing the dynamic behavior of CRMC during the pressure test. Conventional Non-destructive Testing (NDT) such as Ultrasonic (UT) and Radiographic testing (RT) are employed to identify the type of defects. This unique capability of monitoring the dynamic behavior of active defects during real-time is of great significance for the acceptance of CRMC. The evolution of such an online system requires, first, identification of an appropriate process and next its adoption to meet the challenges posed by composite materials. There are various steps involved in the online SHM of CRMC. In this paper, various test practices, requirements, test parameters along with the details of strain and dilation measurements are given. This online inspection methodology and strain-dilation measurement during the Proof Pressure Test (PPT), along with a series of other inspection methods form the basis of CRMC acceptance for further use.