Shock sensitivity of a double-base propellant as a function of age, processing method, and size

Abstract

Shock sensitivity of a double-base propellant (nitroglycerin and nitrocellulose with smaller quantities of other ingredients) was compared for fresh and aged samples. Because the available amount of propellant was less than that needed for extrusion, most samples were pressed. The large-scale gap test (LSGT) was consistent for 240-g samples of fresh propellant whether extruded as one piece or ~6-mm pieces pressed together directly into the confinement tube. The latter had the same density but with microscopic gaps between pieces and nitrocellulose fibers randomly oriented instead of being aligned with the extrusion axis. In a further reduction of the amount of required propellant, 11-g samples pressed from ~3-mm pieces had the same critical shock pressure in the Insensitive High Explosive gap test (IHEGT), which has a LSGT donor and replicates its confinement. There was just enough propellant aged for ~13 and ~16 years to press several IHEGT samples each. The critical shock pressure was somewhat lower for aged propellant. These results demonstrate how smaller tests can mimic results in larger ones upon proper consideration of shock, detonation, and material science.