L-307 Lifing Considerations of Composite Propellant Rocket Motors

Composite propellant rocket motors are highly complex, highly energetic systems that are required to operate in demanding and often changing environments. Failure of a composite propellant rocket motor in service represents a significant safety hazard; therefore, it is critical to understand and predict the relevant ageing behaviours that cause degradation of composite propellant rocket motors to an unacceptable level.

This report reviews the common ageing behaviours of composite propellant rocket motors, with a focus on ageing phenomena affecting the mechanical properties of composite propellant. Challenges in determining the primary safety critical ageing phenomena for composite propellant rocket motors are identified.

Current in-service surveillance activities for monitoring the ageing behaviour of composite propellant rocket motors are also reviewed and considerations for improving the efficacy of these activities are discussed. The challenges associated in using modelling techniques to inform safe-life assessments of composite propellant rocket motors are investigated, and the complexity of modelling just one aspect of ageing behaviour is demonstrated. Simpler models are shown to provide short term confidence in predictive estimates, with the support of validation through regular testing.

Several recommendations have been made and areas of future work identified with the aim of improving the current in-service surveillance testing and safe life assessment of composite propellant rocket motors.