Thermal protection issues for reusable high-speed vehicles under combined thermal effects

This study focuses on reusable high-speed vehicles, investigating the physical modeling of aerodynamic heating near heated surfaces under coupled thermo-integrated effects, strongly unsteady heat conduction calculations on structural surfaces, and time-marching coupling strategies. A multi-level concept of reusable thermal protection is proposed, encompassing materials, structures, and flight performance. The influence of material property evolution and accumulated thermal deformation of structures on the thermal protection system and flight performance is elaborated. Furthermore, a multi-level evaluation methodology and a preliminary indicator system based on mission profiles are discussed. The analysis shows that the accuracy of the coupled analysis is limited by three specific aspects, namely the physical modeling of near-wall aerodynamic heating, the discretization of the transient surface temperature gradient, and the time-marching scheme, rather than by the coupling framework itself. It is also shown that reusability involves different nonlinear mappings and causal chains at the material, structural and flight-performance levels, so that the reusable range and the associated parameters differ from level to level and cannot be captured by a single material-level indicator; accordingly, the criterion should shift from requiring that the material properties do not degrade to requiring that their evolution be predictable and bounded. A hierarchical simplification route is therefore suggested, in which material evolution indicators serve as inputs, flight performance serves as the objective, and critical structural indicators serve as constraints, so as to obtain design results closer to engineering practice at an affordable computational cost, providing references for aerodynamic design, structural design, and thermal protection design in reusable high-speed vehicles.