Enabling Technology for Thermal Protection on HIAD and Other Hypersonic Missions

Gas conduction and radiation are the two important heat transfer mechanisms in highly porous reusable thermal protection systems used for planetary entry of space vehicles. The relative magnitude of the two varies depending on altitude, temperature and the planet. Usually radiation is more significant at lower pressures and at higher temperatures. Gas conduction is more dominant at higher pressures and lower temperatures. In most planetary entries, both modes of heat transfer are significant. Typical flexible or rigid refractory ceramic fiber Thermal Protection System (TPS) such as Advanced Flexible Reusable Surface Insulation (AFRSI) and Shuttle tiles can take high temperatures, can reduce gas conduction at lower pressures, and scatter radiation at higher temperatures. There is a need for more efficient TPS with lower mass, reduced thickness and significantly lower thermal conductivity to make inter planetary missions possible. In order to achieve this goal, insulations need to be developed that can further reduce gas conduction and radiation heat transfer compared to standard refractory ceramic fiber insulations. The overall objective of the Phase II program is to migrate and optimize proven paper making concepts to fabricate robust, flexible and cost efficient, fiber reinforced aerogels, without sacrificing the thermal and mechanical qualities, in large sections suitable for application on High Speed Vehicles (HSV?s). Further investigation in Phase II would focus on production methods and recipe optimization for this new class of thermal insulations. Embedding materials with advantageous properties into fibrous mats allows tailoring the temperature and flexibility requirements to meet the needs of specific missions.