Operational limits for reusable STS due to physical boundaries of C/SiC materials

Abstract

The paper concentrates on the surface interaction phenomena of both SiC-coated and uncoated C/C–SiC material of DLR's well known liquid siliconizing process (LSI) while exposing samples and structures to simulated and real space vehicle reentry conditions. During reentry, physical limits for these types of CMC materials are defined by oxidation resistance, passive–active transition conditions and erosion effects by various reasons like `mechanical' fluid–surface interaction. Special emphasis is given to the passive–active transition behaviour of SiC and the related `temperature jump effect' which will be explained by new theoretical research results. In addition a quantitative evaluation of the effect is given based on experimental test sample data. The considerations given in the paper are checked against literature data, observations and experience which have been achieved so far by manifold tests with samples in various facilities, experimental space reentry tests with samples on Russian FOTON capsules and a test with a hot structure during the EXPRESS mission (experiment CETEX). Finally, the understanding of the mechanisms may lead to a revised strategy for optimizing criterions for reentry trajectories of reusable space transportation systems.