Non-cylindrical mine drop experiment

Abstract

The Navy’s Impact Burial Model (IMPACT35) predicts the cylindrical mine trajectory in air and water columns and burial depth and orientation in sediment. Impact burial calculations are derived primarily from the sediment characteristics and from the mine’s threedimensional air and water phase trajectories. Accurate burial prediction requires that the model’s water phase trajectory reasonably mimics the object’s true trajectory. In order to determine what effect varying the shape to more closely match real-world mines has on the shape’s water phase trajectory, Mine Drop Experiment II was conducted. The experiment consisted of dropping four separate types of shapes into a water column, and the resultant falls were filmed from two nearly orthogonal angles. Initial drop position, initial velocities, and the drop angle were controlled parameters. Observed trajectories were highly variable, but several broad conclusions were reached: the Manta and Rockan shapes’ trajectories were much more complex than the Sphere and Gumdrop trajectories; the denser Gumdrop shape had the fastest and straightest drops overall to –250 cm depth; because of important factors, the dispersion of all four shapes was wide and variable. The data collected from the experiment can be used to develop and validate the mine Impact Burial Prediction Model with operational, non-cylindrical mine shapes.