CRATERING EXPERIMENTS ON ICE - DEPENDENCE OF CRATER FORMATION ON PROJECTILE MATERIALS AND SCALING PARAMETER

We have carried out the cratering experiments on -18 degrees C (255 K) water ice. The projectiles of ice, aluminum alloy, polycarbonate and iron were used to investigate the effects of projectiles' physical properties to crater formation. We found dependencies of the cratering efficiency related to projectile materials on the scaling parameter for strength dominant crater, late-stage effective energy [Karo et al., 1995]. Shock waves propagating in ice were measured to obtain new Hugoniot data and to consider the effects of the material properties of the projectiles. With analysis of shock wave pulse, the impact duration for ice projectile reduced 20 to 50 % from that by one dimensional analyses. On the basis of shock wave measurements, we have modified late-stage effective energy. With this modified late-stage effective energy, the experimental results using projectiles with various sizes and material became consistent.