Scaling and reproducibility of craters produced at the Experimental Projectile Impact Chamber (EPIC), Centro de Astrobiologia, Spain

The Experimental Projectile Impact Chamber (EPIC) is a specially designed facility for the study of processes related to wet-target (e.g., marine) impacts. It consists of a 7 m wide, funnel-shaped test bed, and a 20.5 mm caliber compressed N-2 gas gun. The target can be unconsolidated or liquid. The gas gun can launch 20 mm projectiles of various solid materials under ambient atmospheric pressure and at various angles from the horizontal. To test the functionality and quality of obtained results by EPIC, impacts were performed into dry beach sand targets with two different projectile materials; ceramic Al2O3 (max. velocity 290 m s(-1)) and Delrin (max. velocity 410 m s(-1)); 23 shots used a quarterspace setting (19 normal, 4 at 53 degrees from horizontal) and 14 were in a half-space setting (13 normal, 1 at 53 degrees). The experiments were compared with numerical simulations using the iSALE code. Differences were seen between the nondisruptive Al2O3 (ceramic) and the disruptive Delrin (polymer) projectiles in transient crater development. All final crater dimensions, when plotted in scaled form, agree reasonably well with the results of other studies of impacts into granular materials. We also successfully validated numerical models of vertical and oblique impacts in sand against the experimental results, as well as demonstrated that the EPIC quarter-space experiments are a reasonable approximation for half-space experiments. Altogether, the combined evaluation of experiments and numerical simulations support the usefulness of the EPIC in impact cratering studies.