Advanced metallic thermal protection systems for reusable launch vehicles.

摘要

Metallic thermal protection systems are a key technology that may help achieve the goal of reducing the cost of space access. A study was performed to develop an understanding of the key factors that govern the performance of metallic thermal protection systems for reusable launch vehicles. Multi-disciplinary background information was assembled and reviewed critically to provide a basis for development of improved metallic thermal protection systems. The fundamentals of aerodynamic heating were reviewed and applied to the development of thermal protection systems. General approaches to thermal protection were categorized and critiqued. The high temperature materials used for thermal protection systems (TPS), including insulations, structural materials, and coatings were reviewed. The history of metallic TPS from early pre-Shuttle concepts to current concepts for a reusable launch vehicle was reviewed for the first time. A current advanced metallic TPS concept was presented and systematically analyzed to discover the most important factors governing the thermal performance of metallic TPS. A large number of relevant factors that influence the thermal analysis and thermal performance of metallic TPS were identified and quantified. Detailed finite element computational models were developed for predicting the thermal performance of variations of the advanced metallic TPS concept mounted on a simple, unstiffened structure. The computational models were also used, in an automated iterative procedure, for sizing the metallic TPS to maintain the structure below a specified temperature limit. A statistical sensitivity analysis method, based on orthogonal matrix techniques used in robust design, was used to quantify and rank the relative importance of the various modeling and design factors considered in this study. Results from this study identify factors that have the most potential to improve metallic TPS performance. The thermal properties of the underlying vehicle structure were found to have a major impact on the thickness and mass of metallic TPS required to protect the structure, leading to the conclusion that the structure and TPS should be designed concurrently. Improved insulation properties were also shown to reduce the required thickness and mass of TPS. Including some heat loss from the structural skin to the interior of a vehicle was found to decrease significantly the required TPS thickness and mass. These results provide a basis for guiding the direction of future research in metallic TPS.