Fundamental Modeling and Thermal Performance Issues for Metallic Thermal Protection System Concept

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. A current advanced metallic thermal protection system concept was systematically analyzed to discover the most important factors governing its thermal performance. A large number of relevant factors that influence the thermal analysis and thermal performance system were identified and quantified. Detailed finite element models were developed for predicting the thermal performance of design variations of the metallic thermal protection system concept mounted on a simple, unstiffened structure. The computational models were also used, in an automated iterative procedure, for sizing the metallic thermal protection system 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. Thermal performance was shown to be sensitive to several analytical assumptions that should be chosen carefully. Of the design factors studied, the heat capacity of the underlying structure was found to have the greatest effect on thermal performance. Therefore the structure and thermal protection system should be designed concurrently.