Experimental study on the velocity of fragments in collisional breakup

Abstract The motion of fragments following a catastrophic destruction by either a normal or an oblique impact at 2.5–2.9 km sec−1 into cubic and spherical basalt targets was studied with a high-speed framing camera. Velocities at the antipodes of the targets vary as (E/M)0.75 (E = impact energy; M = target mass) and are lower than 200 m sec−1 at E/M ⪅ 109 ergs g−1. Excluding fine-grained particles from the impact site, 70 to 80% by mass fraction of the fragments have velocities lower than twice the antipodal velocity. Comminution and ejection energies wasted in this mass fraction were a few percent of the impact energy at E/M ⪅ 5 × 107 ergs g−1. During a catastrophic impact into asteroids some of the fragmented bodies can be reconcentrated by mutual gravitation.