PROBABILITY OF SOLID-PROPELLANT MOTOR FAILURE DUE TO ENVIRONMENTAL TEMPERATURES

Solid-propellant rocket motors are frequently stored in the field without environmental protection; hence they are subjected to variable thermal stresses and material degradation due to aging and fatigue. Temperature variations are modeled as narrow-band random processes; thermal stresses in the motor will exhibit similar characteristics. Because material properties are statistically distributed, the probability that the thermal stress exceeds the strength of the propellant is synonymous with the probability of failure. A simplified solidpropellant rocket motor is analyzed as a long hollow elastic cylinder in a thin case (plane strain). The daily probabilities of failure are determined from a stress-strength interference-type analysis as functions of time and are summed up to produce the probability of failure at the end of the service life. The additional complexities of viscoelasticity, aging, and loads other than thermal will be introduced in subsequent analyses. © American Institute of Aeronautics and Astronautics, Inc., 1979, All rights reserved.