Medium-high kinetic energy impact on asteroids—The influence of target compressive strength and projectile velocity on momentum enhancement, ejecta characteristics and craters

This study investigates the influence of target compressive strength and projectile velocity on momentum enhancement under medium-high speed kinetic impact. Steel spheres with a diameter of 6 mm were employed as projectiles, while concrete targets with compressive strengths ranging from 20 to 60 MPa were used. Previous studies often utilized projectiles at velocities exceeding 1000 m/s, a regime where projectiles cannot typically be treated as rigid bodies. This research focuses on measuring momentum enhancement under rigid-body penetration conditions, with experimental impact velocities ranging from 300 to 1000 m/s. The momentum enhancement of the target was quantified, along with fragment velocities and crater morphology. Simultaneously, experiments were simulated using Autodyn. The results indicate that, under medium-high speed kinetic impacts, the effects of projectile velocity and target compressive strength on momentum enhancement are relatively small, approximating a constant value. The velocity distribution of the ejecta follows a near-normal distribution. At the same compressive strength, an increase in impact velocity corresponds to a gradual rise in the fragment speed associated with the peak frequency. However, at similar impact velocity, the change in peak frequency velocity is not significant with increasing material strength. The volume and depth of the craters are positively correlated with projectile impact velocity and negatively correlated with target compressive strength. This study provides empirical evidence support for understanding the momentum amplification effect under medium-high velocity kinetic impacts, offering references for future research in asteroid deflection.