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Aug 19, 2014

Control and Modeling Shock Sensitivity of a High Explosive

Paul E. Anderson, PhD, Chemist, US Army ARDEC            

Douglas Ray, PhD, Statistician, US Army ARDEC

Erik Wrobel, Explosive Engineer, US Army ARDEC

Recent formulation efforts in the US Army have led to extremely insensitive high explosives. While these insensitive munitions (IM) provide an extra layer of safety for the warfighter, the physics of detonation initiation in them differ greatly from the more sensitive legacy explosives. In this study, glass microballoons were used to sensitize a particular IM explosive. Two sizes of microballoons were mixed into the test explosive at two different loadings (1 percent and 10 percent by volume) for a total of four formulations. The shock sensitivity, or "go/no-go" point was determined through expanded large scale gap tests (ELSGT) for each formulation. In this test, the shock pressure at which the explosive will carry the detonation is identified using a standard methodology. It was found that as little as 1 percent by volume addition of microballoons resulted in a statistically significant increase in shock sensitivity. Further modeling of the test series was done using a generalized linear model with penalized regression and nested factors. The resulting models were used to further explore 50 percent point as a function of the type of microballoon and volume loading of microballoon. The result, along with significant increases in sensitivity of the other three formulations, points to porosity distribution and not density as a main factor in promoting shock sensitivity.