Duplication of hypersonic stagnation-region aerothermochemistry and gas-surface interaction in high-enthalpy ground testing

Testing thermal protection system materials in ground-based facilities, such as plasma wind tunnels, is a key step in the development of entry vehicles. The Local Heat Transfer Simulation methodology offers a systematic approach to identify, from a set of flight conditions such as altitude, velocity and vehicle size, the proper aerothermochemical testing environment to correctly reproduce the boundary layer near the stagnation point of the entry vehicle. Eventually, such a duplication ensures that the aerothermochemical flow characteristics of a hypersonic flight are correctly simulated during the ground testing of a material sample. The present work deals with the verification of the applicability of this methodology in the case of ablative-material testing, considering that the stagnation region could be significantly affected by the surface phenomena and the bulk mass injection. The performed theoretical analysis shows that the methodology can still be applied without any modifications to investigate the response of ablative thermal protection materials in a hypersonic environment. A numerical experiment is carried out which confirms these results, showing that the Local Heat Transfer Simulation methodology allows achieving in a ground-testing facility the complete duplication of the flight boundary-layer quantities near the stagnation region of the thermal protection material, regardless the specific gas-surface interaction mechanisms for the material under consideration.