ZHANG Yun, LIU Yan, LI Junfeng
The kinetic impact deflection would result in a number of unexpected hazardous fragments. For this reason, understanding the outcomes of impact is fundamental to assess the effects of this mitigation technique. The process of hyper-velocity impact of a small artificial aluminum projectile on an S-type asteroid is investigated with the material point method（MPM）. In order to evaluate the impact threat of the resulting fragments posed to the Earth, the impact outcomes are transferred to the heliocentric orbit of a hazardous asteroid. A parallel N-body code is applied to propagate the evolution of these fragments in the solar system. The impact hazard of the fragments on the Earth is analyzed and the role of asteroid interior structures is explored. The results show that the structure of the simulated body is partially destroyed by the kinetic impactor. Some of the resulting fragments move backward along the impact direction, enhancing the deflection efficiency. Furthermore, the collision outcomes proved to be very dependent on the internal structure of the asteroid. The fragments produced from the monolithic target are much smaller than those from the rubble-pile one, while the size and speed distribution of fragments in the former case is steeper and smaller. The hazard assessment implies that although the impact damage to the Earth is reduced from the deflection, there are still a number of small resulting fragments posing threat to the Earth. The expected damage caused by the deflected monolithic target is larger than the rubble-pile target because of the exist of numerous small dangerous fragments. The method presented in this study can be used to infer the impact condition and outcomes in future planetary defense missions.
