Skid Testing Report (FY 2019)

Abstract

The Skid Test is an experiment that impacts an explosive charge obliquely upon a gritty target in order to deliver a frictional ignition stimulus. At Los Alamos, the Skid Test has been used since 2011 to test myriad explosives, drop heights, impact angles, target materials, target coatings, and other variables. In FY19, forty-four tests were performed. The focus was twofold: 1) investigate the possibility that grit pre-embedded into PBX 9501 can create ignitions when impacting a gritty soft-rubber surface, via grit-grit interactions; 2) test the HMX-based UK explosive EDC37 in typical Skid Test conditions. Thirty-one tests were performed with grit pre-embedded in PBX 9501, dropped onto gritty soft rubber targets. No ignitions were observed in any of the tests. Previously, nominally identical tests were performed, except lacking the pre-embedded grit, and no ignitions were observed in those tests. Post-mortem analysis suggests that grit-grit collisions are common, yet still fail to produce ignitions. We hypothesize that the softness of the rubber target fails to provide sufficient normal force for frictional heating, regardless the grit-grit collisions. Eleven tests with EDC37 were conducted in total, at drop heights of 9 in, 6 ft, and 9 ft and with grit diameters of 75-150 µm, 150-250 µm, 250-500 µm, and 500-1000 µm. Ignition of hotspots followed by quench was observed in a single test at an incident angle of 14° and effective drop height of 9 ft. These results demonstrate that EDC37 is safer—i.e. less prone to ignition—than other conventional high explosives tested to date, including PBX 9501.