不同密度弹丸对水冰的超高速撞击成坑实验

为了研究冰冻天体表面撞击坑的形成与演化，开展了水冰的超高速撞击成坑实验。使用二级轻气炮发射1.0 mm直径的球形弹丸，以3 km/s、5 km/s和7 km/s速度对圆柱状冰块进行撞击。弹丸材料包括聚碳酸酯和不锈钢两种，冰块温度为253 K。实验观察到了不同弹丸和不同速度条件下，冰块中撞击坑的形貌特征。对撞击坑直径、深度和剖面形状进行了测量，并与文献中铝弹丸对水冰的撞击坑进行了比较分析。获得了水冰撞击坑特征随撞击参数的变化规律，结果表明：撞击坑直径和深度的主导机制不同，坑深主要由弹丸侵彻作用形成，而坑径主要由冰块的剥落所致；坑深比坑径具有更强的对于弹丸密度的依赖性，高密度弹丸撞击坑直径具有比低密度弹丸更强的对于撞击速度的依赖性；撞击坑体积与撞击能量成正比，高密度弹丸形成的撞击坑直径表现出“能量缩比”行为，而低密度弹丸形成的撞击坑直径表现出“动量缩比”行为。

Hypervelocity Impact Cratering in Water Ice by Projectiles with Different Densities

 Hypervelocity impact cratering tests have been performed on water ice to investigate the formation and evolution of the impact craters on the surfaces of icy bodies. Spherical projectiles with 1.0 mm diameter are launched by a two-stage light gas gun to impact the ice cylinder at a velocity of 3 km/s, 5 km/s, and 7 km/s respectively. The projectile materials include the polycarbonate and stainless steel, and the temperature of the ice is 253 K. The crater morphologies in the solid ice caused by the different projectiles and different velocities are observed. The crater diameter, depth and profile are measured and compared with the craters caused by the aluminum projectiles in the previous literatures. The relationships between the crater characteristics and impact conditions are constructed. The results show that the crater diameter and crater depth are dominated by the different mechanisms. The crater depth is mainly caused by the projectile penetration, while the crater diameter is mainly caused by the ice spallation. The crater depth shows stronger projectile density dependence than the crater diameter, while the crater diameter caused by higher density projectile shows stronger velocity dependence than that caused by lower density projectile. The crater volume scales relate to the impact energy. The crater diameter caused by higher density projectile shows the “energy-scaling” behavior, while the crater diameter caused by lower density projectile shows “momentum-scaling” behavior.