Manufacturing and performance testing of sol/gel based oxidation protection systems for re-usable space vehicles

Future re-usable spacecraft replacing the US Space Shuttle could be manufactured with heat shields made of carbon fibre reinforced materials; most likely using carbon fibre reinforced silicon carbide (C/SiC). These materials combine excellent thermo-mechanical properties, low weight, and high strength. They can be manufactured by various established production processes. The main drawback is the sensitivity of the carbon fibre against oxidation. An oxidation protection system is required to avoid carbon fibre burn-off during the re-entry phase, where temperatures higher than 1550 °C are reached. Most of the oxidation protection systems currently available are manufactured by costly and time-consuming multilayer chemical vapour deposition (CVD) processes. In this work, novel sol/gel based SiC coatings have been developed and tested under approximately identical re-entry conditions (mechanical, thermal, and chemical loads). The manufacturing and application process of several sol/gel based oxidation protection systems are presented, as well as the characterisation of the materials and the post mortem micro structural analysis after various re-entry test conditions. The results show that the oxidation protection performance is comparable to the oxidation protection systems currently available on the market, however, at significantly lower manufacturing costs.