Currently, a 20J fragment projection curve is being used by the Insensitive Munitions (IM) community to distinguish between hazardous and benign energetic responses for various munition systems subjected to simulated combat threats. Substantial resources are being expended to obtain benign responses. Thus it is important for this criterion to be meaningful, accurate, and practical to use. The current criterion is often regarded as too conservative. Accordingly, efforts have been undertaken to devise an improved criterion for what a benign response should entail. Issues include intent of the curve, appropriate hazard metric, conditions at which the metric applies, how the criterion should vary for different shapes and materials, and how many fragments may violate the criterion. These ambiguities led to trajectory modeling being performed to reproduce the curve. It was found that the curve represents the maximum distance a chunky steel warhead fragment could travel with a 20J launch energy. An impact energy criterion would be desirable, but for smaller masses the hazardous distances become unbounded. The community decided to keep 20J as the hazard metric, but changed the criterion to 20J impact at 15m, with a different curves for several fragment densities. This curve guarantees that if the criterion is violated, a 20J impact would occur at 15m if the trajectory were lowered. The authors have constructed the mass-distance curves being incorporated into the new version of AOP-39. Since this work, new calculations have been performed for different hazard metrics such as a larger energy as well as an energy density criterion. This paper documents the methodology and assumptions involved in the generation of the criterion, and lists the outputs for the new hazard metrics.
