TY - JOUR
T1 - Low-speed impacts between rubble piles modeled as collections of polyhedra
AU - Korycansky, D. G.
AU - Asphaug, Erik
N1 - Funding Information:
The authors are members of the Center for Origin, Dynamics and Evolution of Planets (CODEP) at UC Santa Cruz. CODEP is a branch of the Institute of Geophysics and Planetary Physics (IGPP) of the University of California. This research was sponsored by NASA's Planetary Geology and Geophysics Program. Research by D.G.K. was supported by NASA Grant NNGO4G198G, “Asteroid shapes and surface processes.” Effort by E.A. was supported by NASA Grant NNG04GI09G, “Small bodies and planetary collisions.” D.G.K. thanks B.L. Grossman for helpful discussions about collision-detection algorithms and program development. The presentation of the paper has been improved by comments from P. Michel and anonymous referee.
PY - 2006/4
Y1 - 2006/4
N2 - We present results of modeling rubble piles as collections of polyhedra. The use of polyhedra allows more realistic (irregular) shapes and interactions (e.g. collisions), particularly for objects of different sizes. Rotational degrees of freedom are included in the modeling, which may be important components of the motion. We solved the equations of rigid-body dynamics, including frictional/inelastic collisions, for collections of up to several hundred elements. As a demonstration of the methods and to compare with previous work by other researchers, we simulated low-speed collisions between km-scale bodies with the same general parameters as those simulated by Leinhardt et al. [Leinhardt, Z.M., Richardson, D.C., Quinn, T., 2000. Icarus 146, 133-151]. High-speed collisions appropriate to present-day asteroid encounters require additional treatment of shock effects and fragmentation and are the subject of future work; here we study regimes appropriate to planetesimal accretion and re-accretion in the aftermath of catastrophic events. Collisions between equal-mass objects at low speeds (<103 cms-1) were simulated for both head-on and off-center collisions between rubble piles made of a power-law mass spectrum of sub-elements. Very low-speed head-on collisions produce single objects from the coalescence of the impactors. For slightly higher speeds, extensive disruption occurs, but re-accretion produces a single object with most of the total mass. For increasingly higher speeds, the re-accreted object has smaller mass, finally resulting in complete catastrophic disruption with all sub-elements on escape trajectories and only small amounts of mass in re-accreted bodies. Off-center collisions at moderately low speeds produce two re-accreted objects of approximately equal mass, separating at greater than escape speed. At high speed, complete disruption occurs as with the high-speed head-on collisions. Head-on collisions at low to moderate speeds result in objects of mostly oblate shape, while higher speed collisions produce mostly prolate objects, as do off-center collisions at moderate and high speeds. Collisions carried out with the same dissipative coefficients (coefficient of restitution εn = 0.8, zero friction) as used by Leinhardt et al. [Leinhardt, Z.M., Richardson, D.C., Quinn, T., 2000. Icarus 146, 133-151] result in a value for specific energy for disruption QD* ≈ 1.4 J/kg, somewhat lower than the value of 2 J/kg found by them, while collisions with a lower coefficient of restitution and friction [εn = 0.5, ε t = 0, μ = 0.5, similar to those used by Michel, et al. [Michel, P., Benz, W., Richardson, D.C., 2004. Planet. Space Sci. 52, 1109-1117] for SPH + N-body calculations] yield QD* ≈ 1.4 J/kg.
AB - We present results of modeling rubble piles as collections of polyhedra. The use of polyhedra allows more realistic (irregular) shapes and interactions (e.g. collisions), particularly for objects of different sizes. Rotational degrees of freedom are included in the modeling, which may be important components of the motion. We solved the equations of rigid-body dynamics, including frictional/inelastic collisions, for collections of up to several hundred elements. As a demonstration of the methods and to compare with previous work by other researchers, we simulated low-speed collisions between km-scale bodies with the same general parameters as those simulated by Leinhardt et al. [Leinhardt, Z.M., Richardson, D.C., Quinn, T., 2000. Icarus 146, 133-151]. High-speed collisions appropriate to present-day asteroid encounters require additional treatment of shock effects and fragmentation and are the subject of future work; here we study regimes appropriate to planetesimal accretion and re-accretion in the aftermath of catastrophic events. Collisions between equal-mass objects at low speeds (<103 cms-1) were simulated for both head-on and off-center collisions between rubble piles made of a power-law mass spectrum of sub-elements. Very low-speed head-on collisions produce single objects from the coalescence of the impactors. For slightly higher speeds, extensive disruption occurs, but re-accretion produces a single object with most of the total mass. For increasingly higher speeds, the re-accreted object has smaller mass, finally resulting in complete catastrophic disruption with all sub-elements on escape trajectories and only small amounts of mass in re-accreted bodies. Off-center collisions at moderately low speeds produce two re-accreted objects of approximately equal mass, separating at greater than escape speed. At high speed, complete disruption occurs as with the high-speed head-on collisions. Head-on collisions at low to moderate speeds result in objects of mostly oblate shape, while higher speed collisions produce mostly prolate objects, as do off-center collisions at moderate and high speeds. Collisions carried out with the same dissipative coefficients (coefficient of restitution εn = 0.8, zero friction) as used by Leinhardt et al. [Leinhardt, Z.M., Richardson, D.C., Quinn, T., 2000. Icarus 146, 133-151] result in a value for specific energy for disruption QD* ≈ 1.4 J/kg, somewhat lower than the value of 2 J/kg found by them, while collisions with a lower coefficient of restitution and friction [εn = 0.5, ε t = 0, μ = 0.5, similar to those used by Michel, et al. [Michel, P., Benz, W., Richardson, D.C., 2004. Planet. Space Sci. 52, 1109-1117] for SPH + N-body calculations] yield QD* ≈ 1.4 J/kg.
KW - Asteroids
KW - Collisional physics
KW - Dynamics
KW - Impact processes
KW - Planetesimals
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U2 - 10.1016/j.icarus.2005.10.028
DO - 10.1016/j.icarus.2005.10.028
M3 - Article
AN - SCOPUS:33645889647
SN - 0019-1035
VL - 181
SP - 605
EP - 617
JO - Icarus
JF - Icarus
IS - 2
ER -