Abstract
Crack propagation in burning solid propellants and explosives can affect the performance of a rocket motor by increasing both the burning surface area and local pressurization rates. This may sometimes lead to deflagration-to-detonation transition (DDT) or detonation due to some unresolved mechanisms (XDT). In order to obtain direct evidence of structural damage of the propellant sample during crack propagation and branching, an interrupted burning experiment has been designed, constructed, and tested. Sample recovered from a preliminary test firing showed rough surface structure and several macrocracks in directions from the initial crack orientation. The propellant sample is believed to undergo significant cracking and branching before the extinction. This is supported by the experimental evidence of rough and cracked surfaces of the recovered sample, source-flow pattern observed from high-speed movie films, and extremely rapid pressurization of the source-flow region beyond the initial crack tip due to the fast burning of damaged propellant sample.