Actively Cooled Thermal Protections for Future Space Vehicles through Sandwich Structured Ceramic Matrix Composites with Engineered Porous Cores

Kurzfassung

Ceramic cellular structures and ceramic matrix composites (CMCs) are promising materials’ configurations for Thermal Protection Systems (TPS) of future space vehicles. This is because of the good thermal and fluid dynamic properties of their cellular cores coupled with a matchless resistance in harsh environments of their CMC skins. Indeed, their high specific surface area, low weight and oxidation resistance makes them ideal materials for gas cooled TPS. In detail, the high temperature active cooling configuration of the TPS investigated in this work consists of a sandwich structure composed of a highly porous Si‐SiC core coupled with SiCf/SiCm or Cf/Si‐SiCm composite skins. These structures, actively cooled exploiting their internal porosity, present several advantages over a similar passively cooled configuration. Compared with their passive Counterparts (previously developed in the FP7 project SMARTEES) they can lower materials’ temperatures on the skin facing the plasma and reduce the thermal shocks aftermaths avoiding the heat flux to go back and forth through them during a typical re‐entry thermal profile. In the frame of the FP7 project THOR, three‐dimensional thermo fluid dynamics analysis was first performed in order to evaluate temperature and pressure drop in the cellular structure and the CMCs during a re‐entry trajectory. The simulations, aiming at optimizing TPS configuration, were performed with the CFD ANSYS‐Fluent software package, analysed several cellular ceramics structures by varying: porosity, the coolant fluid, mass flows, and CMC composition. Sandwich components were separately produced by polymer infiltration and pyrolysis ( for the SiCf/SiCm CMC) and by reactive melt infiltration for both, the Cf/Si‐SiCm composite and the Si‐SiC cellular structures. They were finally joined with preceramic precursors in the case of SiCf/SiCm ‐to‐Si‐SiC lattices, while, due to different CTEs Cf/Si‐SiCm CMC were just held together by fixations Si‐SiC. Plasma wind tunnel tests were performed in a standard re‐entry condition. Cooling was performed with different gases and mass flows. Data are reported and discussed.