Penetration of sea ice by air-dropped projectiles

Since 1961, Sandia Laboratories has had a continuing program on projectile penetration of in-situ earth materials. This program has resulted in a new technology, called terra-dynamics, which has been used in a variety of military and peaceful applications. During the past four years this technology has been extended to include the penetration of sea ice. Three test programs have been conducted in the Arctic in the development of an ice penetration technology and of various ice penetrator systems. Empirical equations developed during the earth penetration program were modified, based on the results of the Arctic tests, to predict the depth of penetration in ice. When the penetrator configuration, impact velocity, and ice properties are known, the depth of penetration (or maximum ice thick- ness which can be perforated) may be predicted with an accuracy of about ±15?. During the Arctic test programs approximately 25 penetrator configurations were drop tested, and all were instrumented to measure deceleration during ice penetration. From the deceleration records, the hardness and thickness of the ice were remotely determined.