Analysis of Jetting Simulation Experiments.

Abstract : This report describes calculational and analytical studies of high explosive jetting experiments designed to simulate energy injection into a nuclear line of sight. Numerous experiments were performed using identical spherical HE source embedded in wet sand. Damage was assessed by comparing the volume and depth of holes produced in aluminum target plates at the end of each pipe. An evacuated steel pipe, 19 mm o.d. and 0.3 mm thick, was the standard configuration. Many variations were used. Axially symmetric experiments produced some unexpected results, for example: use of a 2 mm jacket of lead around a standard pipe produced holes about twice as great in depth and volume as the average of the standard configurations; use of an air-filled pipe with wall thickness of 0.7 mm produced triple the standard hole size. Simplified calculation including the wall were performed for all three axisymmetric configurations in the frame of reference of a steady shock to provide guidance for the calculations of the actual configurations with a decaying shock. These produced the unexpected result that all three jet particulate mass and energy at equal rates as a steady state is approached. This result is explained by an adaptation of impulsive jetting theory. Configurations employing helical spiral asymmetries, 0.3 to 0.5 mm thick, also produced unexpected results, Spirals resting against the outer pipe wall resulted in essentially no change in target damage, whereas spirals resting against the inner wall virtually eliminated target damage.