Design study on multi-layered stand-off thermal protection system using porous titanium panels

New thermal protection systems (TPSs) with impact resistance, ability of refurbishment and enhanced weather resistance are required for future hypersonic airplanes (HSAs). Compared with reusable launch vehicles, heat flux during flights of HSAs is lower but total heating time of HSAs is much longer. Moreover, TPSs of HSAs will be exposed to elevated temperatures at shorter intervals. The purposes of this study are placed on the designing of multi-layered stand-off TPS (MLS-TPS) using SiC-fiber/SiC matrix composites (SiC/SiCs) and porous Titanium (PoTi) sandwich panels, and on discussing applicability of the TPS to a Mach 5 HSA which is under consideration at JAXA. The MLS-TPS consists of a surface panel made of a SiC/SiC separated from fuselage using SiC/SiC posts (Stand-off structure). PoTi sandwich panels are inserted between the surface panel and fuselage to reduce the heat input to fuselage (Multi-layered insulation structure). Thermal insulation performances at the Mach 5 cruise condition were estimated using three-dimensional finite element analysis (FEA) up to the heat flux of 30kW/m². The FEA results indicated that fuselage temperatures at the heat flux of up to 30kW/m² can be lower than allowable upper limit temperature of aluminium alloy without using active cooling. Furthermore, it was shown that the low thermal expansion of SiC/SiC surface panel was highly effective for supressing the thermal deformation of MLS-TPS.