Design Qualification of a Single-Grain Rocket Motor for Shelf Life Extension Program of Multi-Grain Rocket Motor

Abstract

A single grain rocket motor was designed to be used in a shelf life assessment and extension program for a solid double-based propellant multigrain rocket motor. The qualification of the single-grain rocket motor has been performed through several static firings to measure the different ballistic characteristics at different temperatures. The purpose of such qualification firings was to approve the suitability of the design of the single-grain rocket motor to give comparable ballistic performance to the multi-grain rocket motor, which should match the original specifications of such motors.

A review on the effect of ageing on the ballistic properties of solid gun and rocket propellants

“…However, although the multi-grain motor had an approximately 15 % longer burn time, compared with the single-grain, this difference would not be expected to significantly affect the function and purpose desired from the single-grain rocket motor. The results verified the suitability of the designed single-grain rocket motor to give the required ballistic performance of a real motor [76].…”

“…The service life (safe use life) of a rocket motor is at an end when it reaches any critical condition for its functioning. This may correspond to the point at which a change in ballistic functioning brings such parameters outside the required limits, which includes the ability of the rocket motors to function satisfactorily at the high and low extremes of the service temperature range [76].…”

“…Life assessment programmes require a significant number of rocket motors of different ages and different climatic histories as the ballistic performance data would only be reliable if obtained from a minimum of three to five rocket motors. To reduce this significant burden, research was conducted to assess if a single-grain rocket motor could be designed to be used in a shelf life assessment and extension program for a solid double base propellant multi-grain rocket motor [76].…”

“…Life assessments of a number of double base rocket propellants, with 20-30 years in service, were performed and as part of this ballistic testing was conducted. These have enabled data to be obtained to predict the safe use life of the rocket motors containing these propellants, [30,77].…”

“…In a non-platonised propellant, the resulting degradation of NC results in an increase in burning rate at a given pressure, which progresses continuously with prolonged storage or ageing. However, in a platonised propellant, the rate of nitration of such agents is likely to be dominant, compared with NC degradation and this may play some part in the ballistic changes [77].…”