Stardust interstellar dust calibration: Hydrocode modeling of impacts on Al-1100 foil at velocities up to 300kms ~(-1) and validation with experimental data

摘要

We present initial results from hydrocode modeling of impacts on Al-1100 foils, undertaken to aid the interstellar preliminary examination (ISPE) phase for the NASA Stardust mission interstellar dust collector tray. We used Ansys' AUTODYN to model impacts of micrometer-scale, and smaller projectiles onto Stardust foil (100μm thick Al-1100) at velocities up to 300kms -1. It is thought that impacts onto the interstellar dust collector foils may have been made by a combination of interstellar dust particles (ISP), interplanetary dust particles (IDP) on comet, and asteroid derived orbits, β micrometeoroids, nanometer dust in the solar wind, and spacecraft derived secondary ejecta. The characteristic velocity of the potential impactors thus ranges from 1 to a few kms -1 (secondary ejecta), approximately 4-25kms -1 for ISP and IDP, up to hundreds of kms -1 for the nanoscale dust reported by Meyer-Vernet et al. (2009). There are currently no extensive experimental calibrations for the higher velocity conditions, and the main focus of this work was therefore to use hydrocode models to investigate the morphometry of impact craters, as a means to determine an approximate impactor speed, and thus origin. The model was validated against existing experimental data for impact speeds up to approximately 30kms -1 for particles ranging in density from 2.4kgm -3 (glass) to 7.8kgm -3 (iron). Interpolation equations are given to predict the crater depth and diameter for a solid impactor with any diameter between 100nm and 4μm and density between 2.4 and 7.8kg m -3.