Study of the Scale Size Effect on Momentum Enhancement in Hypervelocity Impact for Rock Target

Abstract The Kinetic Impactor concept at hypervelocity is one of the most mature asteroid deflection methods. Momentum enhancement is quantified by β, which is the ratio of the momentum of the initial impactor to the momentum of the target after impact. While it is known that the momentum transfer ratio scales to projectile size for aluminum targets, it is still unknown for rock targets at hypervelocity impact. Therefore, in this study, the effect of projectile size on the β in a rock target was investigated using impact experiments and data analysis. Furthermore, impact experiments and numerical simulations were conducted focusing not only on spherical projectiles but also on cylindrical ones. In experiments, spherical projectiles and four types of cylindrical projectiles with different lengths were impacted into firebrick targets. In simulations, cylindrical projectiles were impacted into rock targets at 1-6 km/s using ANSYS AUTODYN. In conclusion, at least spherical projectile, the size scale effect was observed for consolidated rock materials, but the effect was smaller for porous materials. Further simulation data are required to fully answer whether the same size scale effect is observed for cylindrical projectiles as for spherical ones.