PHYSICS OF INTERPLANETARY DUST CAPTURE VIA IMPACT INTO ORGANIC POLYMER FOAMS

The physics of hypervelocity impacts into foams is of interest because of the possible application to interplanetary dust particle (IDP) cap ture by spacecraft. We present a model for the phenomena occurring in such impacts into low-density organic polymer foams. Particles smaller than foam cells behave as if the foam is a series of solid slabs and are fragmented and, at higher velocities, thermally altered. Particles much larger than the foam cells behave as if the foam were a continuu m, allowing the use of a continuum mechanics model to describe the eff ects of drag and ablation. Fragmentation is expected to be a major pro cess, especially for aggregates of small grains. Calculations based on these arguments accurately predict experimental data and, for hypothe tical IDPs, indicate that recovery of organic materials will be low fo r encounter velocities greater than 5 km s(-1) For an organic particle 100 mu m in diameter, similar to 35% of the original mass would be co llected in an impact at 5 km s(-1), dropping to similar to 10% at 10 k m s(-1) and similar to 0% at 15 km s(-1). For the same velocities the recovery ratios for troilite (FeS) are similar to 95%, 65%, and 50%, a nd for olivine (Mg2SiO4) they are similar to 98%, 80%, and 65%, demons trating that inorganic materials are much more easily collected. The d ensity of the collector material has only a second-order effect, chang ing the recovered mass by <10% of the original mass.