Simulated experiment on case overheating failure of solid rocket motor under flight overload condition

Abstract

Under flight overload condition, the local heat transfer in a solid rocket motor (SRM) is strengthened due to the erosion of dense two-phase flow which may cause the case to overheat or even fail. To solve this problem, it is necessary to develop effective ground simulation experiment methods. In this study, an experimental device using HTPB/AP propellant and 30CrMnSi case material was set up to simulate the case overheating failure of SRMs under overload condition, meanwhile ablation and temperature measuring experiments were carried out. The case temperature response of the critical state, under which the insulation layer burned out but the case was not destroyed, was measured successfully, and the highest case temperature was estimated at 423 °C. The case temperature started to vary when the virgin insulation layer attained a thickness of 0.6 mm. If residual insulation layer is quite thin when the operation of SRM ends, the case temperature will continue to rise to a fairly high level. This heat transfer aftereffect might not only destroy the case, but also damage other equipment. The results of this study can provide a basis for evaluating the working safety of flight vehicles that employ SRM and undergo flight overloads.