Characterizing the Run-to-Detonation Distance of Hexanitrostilbene by Gap Test Experiments and Simulations

The shock sensitivity of explosives and propellants is an important safety characteristic for developing insensitive munitions (IM). This material property is examined in initiation experiments such as flyer impact or gap tests resulting in critical flyer velocities or gap lengths. In this work the shock-to-detonation transition of Hexanitrostilbene (HNS-II) is investigated in a modified 21mm PMMA gap test. By measuring the time of arrival (ToA) of the shock in the explosive with equidistant short circuit pins on a PCB the run-to-detonation distance of the specimen is determined. The calibrated donor/gap system of the 21mm PMMA gap test provides the incoming shock pressure on the explosive. Combined with the run-to-detonation measurements this results in a Pop plot which is compared to numerical results and used to calibrate a reactive burn model.