In our numerical investigations we are particularly interested in the dynamics of material fragmentation upon impact. For modeling the solids, we use discrete spherical particles that interact with each other via potentials. We present here the results of a systematic numerical study on HVI of solids. Our paper constitutes the first application of DEM to the modeling and simulating of impact events for velocities beyond 5 kms-1. We show that significant impact-produced radio frequency (RF) emissions occurred in frequencies ranging from VHF through L-band and that these emissions were highly correlated with fast (>20 km/s) impacts that produced a fully ionized plasma.ĭiscrete Particle Method for Simulating Hypervelocity Impact Phenomenaĭirectory of Open Access Journals (Sweden)įull Text Available In this paper, we introduce a computational model for the simulation of hypervelocity impact (HVI phenomena which is based on the Discrete Element Method (DEM. We also show results from particle-in-cell (PIC) and computational fluid dynamics (CFD) simulations that allow us to extend to regimes not currently possible with ground-based technology. We present theory and recent results from ground-based impact tests aimed at characterizing hypervelocity impact plasma. Subsequent plasma oscillations resulting from instabilities can also emit significant power and may be responsible for many reported satellite anomalies. Hypervelocity micro particles, including meteoroids and space debris with masses produce a strong electromagnetic pulse (EMP) with a broad frequency spectrum. This is the same velocity threshold for the detection of RF emission in recentĬharacterizing Hypervelocity Impact Plasma Through Experiments and SimulationsĬlose, Sigrid Lee, Nicolas Fletcher, Alex Nuttall, Andrew Hew, Monica Tarantino, Paul We also find that the plasma plume is weakly ionized for impact speeds less than 14 km/s and fully ionized for impact speeds greater than 20 km/s, independent of impactor mass. For a large range of higher impact speeds (30–72 km/s), we find the temperature is unvarying at 2.5 eV. By examining a series of hypervelocity impacts, basic properties of the impact produced plasma plume (density, temperature, expansion speed, charge state) are determined for impactor speeds between 10 and 72 km/s. A smoothed particle hydrodynamics method is used to perform a continuum dynamics simulation with these additional physics. These simulations incorporate elasticity and plasticity of the solid target, phase change and plasma formation, and non-ideal plasma physics due to the high density and low temperature of the plasma. Multi-physics simulations of plasma production from hypervelocity impacts are presented. Under certain conditions, the impact-produced plasma can have deleterious effects on spacecraft electronics by providing a new current path, triggering an electrostatic discharge, causing electromagnetic interference, or generating an electromagnetic pulse. There have been both ground-based and in-situ measurements of radio frequency (RF) emission from hypervelocity impacts, but the physical mechanism responsible and the possible connection to the impact-produced plasma are not well understood. While plasma measurements from hypervelocity impacts have been made using ground-based technologies such as light gas guns and Van de Graaff dust accelerators, some of the basic plasma properties vary significantly between experiments. The resulting plasma rapidly expands into the surrounding vacuum. Hypervelocity particles, such as meteoroids and space debris, routinely impact spacecraft and are energetic enough to vaporize and ionize themselves and as well as a portion of the target material. 258, Moffett Field, California 94035 (United States) Simulating plasma production from hypervelocity impactsĮnergy Technology Data Exchange (ETDEWEB)įletcher, Alex, E-mail: Close, Sigrid [Stanford University, Aeronautics and Astronautics, 496 Lomita Mall, Stanford, California 94305 (United States) Mathias, Donovan [NASA Ames Research Center, Bldg.
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