Comparison of Materials for an Integrated Thermal Protection System for Spacecraft Reentry

摘要

An integrated thermal protection system for spacecraft reentry based on a corrugated core sandwich panel concept fulfilling both thermal and structural functions is optimized for minimal mass. We seek the optimal dimensions and the best materials, but directly optimizing both continuous geometric parameters and discrete material choices is difficult. Accordingly the optimization problem is solved in two steps. In the first step, good candidate materials are selected based mainly on their thermal performance, obtained from a spline interpolation of the maximum bottom face sheet temperature. Mild simplifying assumptions allowed a reduction of the number of variables in the interpolation to two nondimensional variables. In combination with a material database, this procedure allowed a graphical comparison and selection of candidate materials. In the second step, the geometry of the integrated thermal protection system panel is optimized for different combinations of the materials identified in step one. The optimization considers both thermal and structural constraints. The lightest panel employs aluminosilicate/Nextel 720 composites for the top face sheet and web corrugation and beryllium for the bottom face sheet. For the same thermal reentry environment, this design was found to be only about 40% heavier than a reference conventional thermal protection system that does not provide any structural load carrying capabilities.