However, a detailed understanding of the jetting occurring during blunt-body penetration, which is essential for planetary applications, has not yet been fully achieved. Jetting during a symmetric collision between two thin plates has been studied extensively.
This may contribute to an increase in the rock-to-ice ratio of the Pluto-Charon system. In addition, McKinnon showed that impacts owing to collisions between icy planetesimals cause an escape of water vapor from the system. Melosh and Sonett pointed out that a large amount of silicate vapor, as produced by impact jetting, may be important during giant impacts through injection of the ejected materials into a stable Earth orbit, facilitated by the silicate vapor's pressure gradient. Based on these intense features, impact jetting has been considered as a viable mechanism to explain the origin of chondrules and impact glasses.
There are two important features associated with impact jetting : (1) the jet velocity is greater than the impact velocity and (2) jetted materials suffer the highest degree of shock heating during an impact event. This phenomenon is widely known as “impact jetting”. Hypervelocity material ejection during oblique convergence between two thin plates has been observed in both hypervelocity impact experiments and hydrocode calculations. 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.
Isale tillotson eos free#
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. We also present a new formulation of the jet velocity with the equations of state for realistic materials. A decaying shock pressure during blunt-body penetration is a possible origin of the discrepancy. 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. 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. 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. We present the results of high-speed imaging observations of impact jetting during blunt-body penetration under oblique impacts.
Isale tillotson eos series#
We also discuss possible not-shock-related triggers for iron melt.A series of hypervelocity impact experiments was conducted in a new laboratory at Planetary Exploration Research Center of Chiba Institute of Technology (Japan).
Isale tillotson eos code#
Material impedances, grain shapes, and the porosity models available in the iSALE code are discussed. We demonstrate the difficulties of shock heating in iron and also the importance of porosity. The results showed that shock-darkening, associated with troilite melt and the onset of olivine melt, happened between 40 and 50GPa with 52GPa being the pressure at which all tracers in the troilite material reach the melting point. The post-shock temperatures (and the fractions of the tracers experiencing temperatures above the melting point) for each material were estimated after the passage of the shock wave and after the reflections of the shock at grain boundaries in the heterogeneous materials. We used Lagrangian tracers to record the peak shock pressures in each material unit.
We used equations of state (Tillotson EoS and ANEOS) and basic strength and thermal properties to describe the material phases. Iron and troilite grains were resolved in a porous olivine matrix in the sample layer. We simulated planar shock waves on a mesoscale in a sample layer at different nominal pressures. Abstract We determined the shock-darkening pressure range in ordinary chondrites using the iSALE shock physics code.
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