ABSTRACT :

A hard landing probe "penetrator" has been thought to be a very useful tool for planetary exploration, because it provides cost-effective capability of deploying scientific instruments on planetary surface and subsurface. But development of the penetrator for planetary exploration requires better understanding penetration dynamics in geological materials. The present paper describes some experimental results on the penetrator dynamics obtained during the course of the development of the LUNAR-A penetrator. Special emphasis is placed on understanding the effect of the oblique incidence and the attack angle of the penetrator on penetration depth and a final attitude at the rest position. Many impact experiments into a simulated lunar surface material are made using penetrators 30 mm in diameter, and the penetration characteristics (penetration path length and inflection angle) are investigated as functions of impact velocity, penetrator shape, impact angle and attack angle. The results indicate that the torque applied to the penetrator in cases of the impact with a finite attack angle changes the penetration characteristics significantly. The experimental data also suggests that the impact angle does not have a substantial effect on penetration path length and that the truncation of the nose tip from a conical nose is efficient to stabilize the penetration orientation.