Collisional disruption of porous sintered glass beads at low impact velocities

Porous materials are believed to be common in the asteroids and satellites of the outer planets. In order to study the relationship between the structure of small bodies and their thermal and collisional evolution, we performed impact disruption experiments on porous sintered glass bead targets using a light-gas gun. The sintered glass bead targets were prepared to have various porosity and compressive strength. The compressive strength ranges over an order of magnitude according to the various sintering conditions. Both the compressive strength and the longitudinal wave velocity were found to have good correlations with the size of the necks developed between the bead particles. In our first low-velocity impact runs with these targets, we selected the targets with roughly the same porosity but different compressive strength. We shot the targets by cylindrical polycarbonate projectiles at velocities ranging from 10 to 120 m/s. The results showed that the targets of higher compressive strength have higher impact strength as could be expected. However, compared to previous results from the impact disruption of glass bead targets at velocity of 4.9-5.5 km/s [Love, S.G., Horz, F., Donald, E.B. Target porosity effects in impact cratering and collisional disruption. Icarus 105, 216-224, 1993], the impact strength derived in our study was found to be lower by more than an order of magnitude [Setoh, M., Nakamura, A.M., Hiraoka, K., et al. Collisional disruption of weakly sintered porous targets at Low impact velocities. Earth Planet. Space (in press)]. The differences between the two experiments were the impact velocity, target-projectile size ratio, and the projectile material and shape. In our new low-velocity impact runs, we used projectiles of glass spheres that are similar to those of Love et al. The impact strength was again found to be much smaller than those found in high-velocity runs performed by Love et al. Therefore our previous and present results show that collisional outcomes of porous bodies are highly dependent upon impact velocity. (C) 2007 Published by Elsevier Ltd on behalf of COSPAR.