Analysis of ballistic anomalies in solid rocket motors

Abstract

Ballistic anomalies, defined as pressure deviations from the normally expected trace, have occurred frequently during solid rocket motor firings. This paper describes techniques for determining the probable cause of such anomalies. Mass and energy balance relationships, which account for changes in chamber volume and throat area, are derived for the purpose of calculating a burning surface history that corresponds to pressure data from flight measurements or static tests. Results indicate that chamber temperature variations caused by ballistic anomalies are negligible. Characteristic burning surface signatures for propellant voids, cracks, unbonds, and high burn rate pockets are discussed. Conservation of momentum relationships are derived for the purpose of describing anomalies caused by mass ejection through the nozzle throat. Specific examples form inertial upper stage motors and the Titan T34-D solid rocket booster are presented to illustrate the application of the generic analysis techniques described in this paper.