Investigation of Off-Axis Initiation of Long L/D Hemispherical Shaped Charge Warheads

Penetration performance of a shaped charge is strongly dependent on the axial symmetry of the warhead and any deviance from axial symmetry such as inhomogeneity in the explosive fill, dimensional inaccuracies of the liner or off-center initiation causes considerable reduction in the performance [1]. Among these defects, off-center initiation is very likely to occur when no precision initiation coupler is used in the warhead. Also, under severe environmental conditions, it is possible to have relatively large gaps between the initiation device and the main explosive, which may shift the initiation point. It is known that a spherical detonation wave flattens as it travels towards unreacted explosive. Therefore, for large length-to-diameter ratio (L/D) shaped charges, the effect of off-axis initiation is expected to be less severe compared to small L/D ratio warheads since the detonation wave has more distance to re-orient itself. In this study, off-axis initiation of hemispherical shaped charges with moderate to long L/D ratios have been investigated numerically and experimentally. Numerical investigations cover a wide range of L/D ratios and initiation points. The tests have been conducted with shaped charges having a L/D ratio of 4 and three different initiation points. Flash X-ray radiography was used to determine the deviation of the jets from the symmetry axis.