Thomas Ullmann

Reentry Flight Testing of a C/C-SiC Structure with Yttrium Silicate Oxidation Protection

Hot structure design with ceramic matrix composites (CMC) which are based on carbon fiber reinforced materials like C/C-SiC is a key technology for the development of lightweight thermal protection systems (TPS) of advanced space reentry vehicles. In order to select suitable CMC and protective coating materials, ground based hypersonic flight simulation with plasma wind tunnel test facilities represents a valuable method for qualifying several structure components and to achieve a deeper understanding of the thermo-chemical interactions at the material’s surface. However, regarding the technical limitations with ground based test facilities it is indispensable to perform real flight testing with CMC structures in terms of validation of new design concepts which are based on innovative materials. This paper describes a reentry technology experiment – named “KERAMIK” – with its structural components designed and manufactured fully in C/CSiC material, a special type of CMC developed by DLR. It was successfully flown on the Russian Foton-M2 mission in June 2005. One of its C/C-SiC panels was partly protected with different coating. Special attention is paid to an effective two-layer coating system that is based on yttrium silicate and was chosen to improve both oxidation protection and erosion resistance of the C/C-SiC material. Before selected for the flight test, this coating system was extensively tested in plasma wind tunnel facilities. A comparison of the test results with such coated C/C-SiC specimens obtained from test campaigns in different plasma wind tunnel facilities shows two principal approaches for systematic ground based reentry qualification tests.