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Dynamics of hypervelocity jetting during oblique impacts of spherical projectiles investigated via ultrafast imaging
Author(s) -
Kurosawa Kosuke,
Nagaoka Yoichi,
Senshu Hiroki,
Wada Koji,
Hasegawa Sunao,
Sugita Seiji,
Matsui Takafumi
Publication year - 2015
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2014je004730
Subject(s) - hypervelocity , projectile , oblique case , ultrashort pulse , materials science , aerospace engineering , optics , physics , engineering , laser , astronomy , linguistics , philosophy , metallurgy
A series of hypervelocity impact experiments was conducted in a new laboratory at Planetary Exploration Research Center of Chiba Institute of Technology (Japan). We present the results of high‐speed imaging observations of impact jetting during blunt‐body penetration under oblique impacts. The observations were sampled at a frame rate of 100 ns frame −1 , which is much shorter than the characteristic time of projectile penetration under our experimental conditions. The maximum jet velocity was obtained as a function of both impact velocity and the contrast of shock impedance between a projectile and target, enabling us to test theoretical models of impact jetting during oblique impacts of spherical projectiles. We find that the jet velocities measured in this study are much slower than the prediction by the standard theory based on the previous experimental/theoretical results of collisions between two metal plates. A decaying shock pressure during blunt‐body penetration is a possible origin of the discrepancy. We also present a new formulation of the jet velocity with the equations of state for realistic materials. The particle velocities of ejected materials from a free surface are calculated using the Riemann invariant along the isentropes and the Tillotson equations of state in this study. Based on the extremely high velocity of the jet, we point out that impact jetting might contribute to chemistry near the ground surface of planets/satellites with a thick atmosphere, such as Titan.