Impact damage on sandwich panels and multi-layer insulation

Most spacecraft rely intensively on sandwich construction for external structures with multi layer thermal insulation where appropriate. Experience gained in ESA with various spacecraft (ROSETTA, METOP, ATV,…) covers a substantial range of materials and configurations. In this work, the applicability of simple damage equations (e.g. those presently used for single or Whipple shield ballistic limits) to more complex configurations (e.g. sandwich plates with and without MLI) is analyzed. The different sandwich configurations which were submitted to testing are reviewed, impact test results are presented and compared with impact reference data on single plates and Whipple shields. It has been found that sandwich panels have a better tolerance to hypervelocity impacts than monolithic structures. MLI placed in front of the sandwich panels contributes significantly to the overall protection performance in the range of the projectile diameters tested. The complexity of the sandwich structure is responsible for a considerable scatter in the test results. The predictors for Whipple shields applied to sandwich panels with and without MLI can only be considered on a case by case basis for risk assessment analysis.