Space Environment Effects on Advanced Ceramic Coating for Aerospace Thermal-Proof Re-entry Systems

Advanced carbon-based composites, such as carbon/carbon (C/C) or carbon/silicon carbide (C/SiC), are ceramics matrix composites (CMC) employed in aerospace industry for thermal protection systems (TPS) to face the dramatic thermo-mechanical stress suffered by spacecraft structures during re-entry into Earth atmosphere. A branch of current aerospace research is focused in finding ever more effective coating solutions to preserve CMCs from oxidation due to prolonged exposure of the spacecraft surfaces to low Earth orbit (LEO) environment: in long-time missions, in fact, this may lead to so high TPS damaging that its main thermo-mechanical functionality (i.e., withstanding re-entry conditions) would be compromised. This chapter gives an overview of the experimental activity developed during recent years at the Aerospace Systems Laboratory (LSA) of Sapienza University of Rome about the study of C/C materials for protecting aerospace structures from thermal shock in re-entry missions. In particular, advanced coating treatments using ceramic-based (SiC-Al2O3-ZrO2) refractory varnishes, even reinforced by ceramic filling nanoparticles (SiO2 powder), are analyzed by space environment simulation ground-testing: in particular, the activity currently performed by means of LSA dedicate facilities concerns the reproduction of LEO aggressive aging in terms of atomic oxygen/UV irradiation, thermal cycling, and high-temperature ultra-high vacuum conditions.