Ceramic coating on flexible external insulation blankets for reusable missions

Abstract

Flexible thermal protection material (flexible external insulation; FEI) is used in the Reusable Launch Vehicle-Technology Demonstrator (RLV-TD) leeward region where multiple curvatures are present. FEI configuration has silica cloth layers on either side with Cerablanket felt sandwiched and stitched together using quartz thread. FEI should ensure an airframe skin temperature in the leeward region within the temperature constraint limits (100°C) of aluminum alloy during the RLV-TD ascent (4.8 W/cm2) and descent (3.7 W/cm2) phases. A ceramic room-temperature coating with low surface solar absorptivity (α) and high thermal emissivity (ε) to generate the required thermal gradient at the backwall was developed. The salient features of the ceramic coating are roomtemperature curability, ease of application, minimum weight, durability, erosion resistance, stable optical characteristics, easily repairable, non-contaminating, high purity and high temperature compatibility with silica fabric. The properties of the ceramic coating are weight/area: 0.025-0.030 g/cm2, solar absorptivity the UV-VIS region: 0.12-0.18, IR emittance: > 0.86, backwall temperature: < 120°C (from kinetic heating simulation test).