Momentum Transfer in Hypervelocity Impact Experiments on Rock Targets

Abstract

A special phenomenon observed in hypervelocity impacts on rock targets is the so-called momentum multiplication, i.e. the momentum transferred to the target is greater than the original momentum of the projectile. This effect is caused by ejection of debris in the direction opposite to the flight direction of the projectile. In the present study momentum multiplication was investigated as a function of target material properties and projectile velocity. Hypervelocity impact experiments on target materials with different porosities were conducted and the momentum transfer was measured using a ballistic pendulum. Low porous materials like quartzite show larger momentum multiplication than porous materials like sandstone. The smallest momentum multiplication was measured for highly porous aerated concrete. Higher projectile velocity leads to higher momentum multiplication. Furthermore, this increase is stronger for low porous materials compared with porous materials. These observations can be explained by the different ejection behavior. Low porous materials show a directional and very fast ejection whereas porous materials show a slower ejection. The highly porous material shows a diffuse ejection behavior. Furthermore, cratering efficiency is reduced in porous targets leading to a smaller amount of ejected debris. This effect is attributed to energy dissipation caused by irreversible crushing of pore space.

Nanoindenting the Chelyabinsk Meteorite to Learn about Impact Deflection Effects in asteroids

“…In order to take into account these results in impact scenarios, the key parameter to be considered is the  parameter, known as the momentum multiplication factor (see Appendix). If  > 1 there are fragments ejected after the impact and the impact itself becomes more efficient, due to the "momentum multiplication effect" (Hoerth et al 2015). Several models have tried to account for the effects of collision and impact on the momentum multiplication in brittle, porous materials (Benz & Jutzi 2006;Hoerth et al 2015), and in all these models material parameters play a key role.…”

“…Schultz 1993;Holsapple & Housen 2012;Jutzi & Michel 2014; among many others). In solids with low porosity, like the Chelyabinsk meteorite, momentum multiplication is more pronounced, since material ejection is then more directional and no impact energy is dissipated in the form of pore compaction (Hoerth et al 2015). Then, the role of strength can be considered using the strength-dominated cratering model (see Appendix).…”

Nondestructive imaging of hypervelocity impact‐induced damage zones beneath laboratory‐created craters by means of ultrasound travel‐time tomography

“…), and an additional four experiments through the NEO shield program (for details, see Hörth et al. ). After the impact experiments, ultrasound tomography of selected target cross sections were performed to measure the extent of the damage zone underneath the impact crater.…”

Formation of shatter cones in MEMIN impact experiments

“…The sandstone blocks were impacted with the SLGG (space light gas gun) facility for the NEOShield Program at the Fraunhofer Ernst‐Mach‐Institute in Freiburg (Hoerth et al. ). Hoerth et al.…”

“…Both sandstone cubes were impacted roughly perpendicular to stratigraphic layering. The sandstone blocks were impacted with the SLGG (space light gas gun) facility for the NEOShield Program at the Fraunhofer Ernst-Mach-Institute in Freiburg(Hoerth et al 2015). Hoerth et al used aluminum spheres of 5 mm diameter and impacted the target rocks with velocities between 3 and 7 km s À1 .…”