Ejection Angles During Hypervelocity Impacts on Flat and Spherical Targets Investigated with Hydrocode Simulations

Abstract Introduction The NASA’s Double Asteroid Redirection Test (DART) mission was done on 26 September 2022. he DART spacecraft collided with the asteroid Dimorphos, the binary asteroid (65803) Didymos's satellite, at 6.1449 km s-1. The recoil from the impact ejecta generated by the hypervelocity impact to the target body changed the orbital period of Dimorphos [1]. Since the β value, which is defined by the ratio of the momentum of the impactor to the total momentum of the system after the impact, has been estimated to be larger than two, the orbital change was caused mainly by the recoil [2]. The origin of the large β value has been discussed by theoretical studies [e.g., 3,4]. The crater size predicted by the π-group scaling laws on a saturated soil [5] is larger than the radius of Dimorphos under the microgravity condition, indicating that the DART impact would significantly deform the shape of Dimorphos. It is difficult to investigate such collisions with large deformation in analytical ways. Thus, numerical simulations become powerful tools to estimate the momentum of the impact ejecta.