Shock evolution after shaped charge jet impact and its relevance to explosive initiation

Abstract When a shaped charge jet impacts a target containing explosive, the explosive may be initiated by one of three shocks: the impact shock, a bow shock that forms in the inert plate covering the exlosive, or a bow shock that forms in the explosive. In this paper, numerical calculations are used to determine how thick the cover plate must be to prevent initiation by the impact shock and how much time (or distance) is required to form a bow shock in the explosive. The results show that the cover plate must be from 4 to 12 jet diameters (depending on jet velocity) thick to sufficiently attenuate the impact shock so that it will not cause initiation in a common secondary explosive. For a 7-km/s copper jet, a distance of about 8 jet diameters was required to form a bow shock in the explosive. This corresponds well to experimental data reported elsewhere.