Study on Dynamics of Penetrator into Ice

Abstract

To realize the penetrator mission for icy objects in the solar system, the penetration dynamics into ice has been experimentally and numerically studied. In the experiments, the ogive/cylinder projectiles of the mass about 2.6 g were tested for the target made from water ice by the ballistic range at the impact velocity 100-350 m/s. The behavior of the projectile and target was observed by the high-speed video camera. The penetration trajectory was visualized by pouring the plaster into the crater. The empirical analysis model to describe the force acting on the body surface has been developed, based on the panel method and the shock wave analogy. It includes two parameters representing the effective speed of sound of crushed ice and the damping of the pitching motion. Fairly good agreement with the experiments was obtained with respect to the stop conditions of the penetrator by setting these parameters appropriately. The computational result assuming a flight model of the mass 14.9 kg and the impact velocity 300 m/s shows that the maximum deceleration G is in the same order as that for the lunar penetrator.

Visualization of High-Speed Impact of Penetrator into Icy Target

“…The shape of the crater can be visualized by making a mold by pouring plaster into the crater and taking it out after the plaster has been solidified and the ice disappears due to melting [9]. Figure 12 shows a mold of the crater in Figure 10.…”

“…The plaster pouring technique is also useful to visualize the trajectory of the penetrator in the ice. In [9], the analysis model of the penetration dynamics was validated by comparison with the experimental results of the trajectory visualization, the penetration distance and the final attitude of the penetrator. By combining the results obtained by the visualization of the crater formation and the final crater shape, the process of the penetration into ice is summarized as illustrated in Figure 15.…”

“…This is a rough understanding and the penetration distance should be determined after the analysis on the complicated motion of the body in the target, depending on the velocity and angle of attack at the impact, the strength of the target material, the shape, the mass, the moment of inertia and the center-of-gravity location of the penetrator, and so on. In [9], the numerical method to predict the force acting on the penetrator was developed and the penetration distance was predicted after the penetration trajectory analysis.…”