Selection of Critical Failure Modes for Service Life Overtesting

Abstract

An empirical technique for identifying critical failure modes of a solid-propellant rocket motor is presented. The technique was utilized in the Minuteman Long-Range Service Life Analysis (LRSLA) program, where the critical failure modes were selected for overtest. The technique provides for a numeric ranking of the failure potential of all possible failure modes. The failure potential ranking is achieved by identifying and assessing numerically the contributing factors. By assessing such factors as age sensitivity of material properties, evidence of age degradation, initial margin of safety, and effect of component failure mode on system performance, failure modes are ranked least critical to most critical. The technique is verified by reassessment of the margin of safety for each failure mode using data inputs from the dissected overtest motor and material property test program.