Observations on hypervelocity impact damage sustained by multi-layered insulation foils exposed in low earth orbit and simulated in the laboratory

Retrieved multi-layered foil thermal blankets exposed on the Japanese Space Flyer Unit and the MIR Space Station have revealed abundant evidence of damage generated by space debris and micrometeoroids. The blankets have acted as an efficient shield by disrupting small particles during penetration through the many foil layers, with abundant impact-derived residue material being identifiable on the upper layers of the blanket. The morphology of the impact-derived residues is complex with projectile fragments bound by degraded foil material, resulting in highly-evolved melt droplets. A light-gas-gun impact test programme was carried out using single homogeneous olivine mineral grains to help understand the observations of residue made on space-exposed samples from MIR and the Japanese Space Flyer Unit. The damage observed on the test samples, and the distribution and nature of the residue material, were found to be very similar to those from surfaces exposed in low Earth orbit. However, one of the experimental impact residues, preserved on the third layer of the foil stack, did yield a well-defined 820cm(-1) Raman band, characteristic of olivine. This observation suggests that the particle had retained crystallographic integrity and had not undergone extensive melting and quenching during the shock-heating of the impact events. (C) 2003 Elsevier Ltd. All rights reserved.