Testing of Thermal Protection Systems in High-Enthalpy Hypersonic Facilities

Abstract

During the hot phase of atmospheric entry or reentry a space vehicle is exposed to a high-enthalpy hypersonic flow field including regions with chemical and thermal non-equilibrium. The heat loads are significantly influenced by the local gas composition and thermodynamic state, which makes ground testing of thermal protection systems, e.g. in arc heated facilities, an essential task during vehicle design. The flow field used for testing differs from free flight, since the facilities in general cannot generate near-equilibrium free stream conditions due to limitations of the pressure level. The gas-surface interaction, however, is mainly controlled by the local state near the vehicle's surface, which can be duplicated even inside a partially different global flow field. Based on the results of several tests, which were performed for several earth reentry projects, the most important parameters for aerothermal ground tests are identified. Additionally, first results from tests in a CO2 atmosphere in DLR's arc heated facility L2K will be presented.