Investigations on the cook-off response of GAP-based propellant under solid rocket motor structural constraints

GAP-based high-energy solid propellants are prone to ignition and explosion under accidental thermal stimuli during storage and use. This study investigates the cook-off response characteristics of GAP-based propellant under solid rocket motor structural constraints. A motor-representative experimental specimen that incorporates the structural constraints of a rocket motor was employed to conduct cook-off experiments. The complete response process of the propellant under motor-constrained conditions, i.e. from initial heating to final explosion, was captured using a high-speed laser schlieren imaging system. The study reveals that the GAP propellant-based motor response can be divided into several distinct stages: preheating, pyrolysis and gas generation, melting, ignition, convection combustion and potential deflagration-to-detonation transition (DDT). Furthermore, the influences of factors such as nozzle diameter, casing thickness, and heating flux density on the cook-off response behaviour were comprehensively investigated. Moreover, a two-dimensional transient numerical simulation model was developed, capable of representing the thermal decomposition, phase transition, ignition and rapid pressure rise processes of GAP-based propellant under thermal loading. The simulation results were validated against experimental data, showing <2 % deviation in ignition delay time and approximately 0.7 % difference in peak shock wave overpressure, demonstrating satisfactory predictive accuracy.