Statistical Methods for Rapid Aerothermal Analysis and Design Technology

AbstractThe cost and safety goals for NASA's next generation of reusable launch vehicle (RLV)will require that rapid high-fidelity aerothermodynamic design tools be used early in thedesign cycle. To meet these requirements, it is desirable to establish statistical modelsthat quantify and improve the accuracy, extend the applicability, and enable combinedanalyses using existing prediction tools. The research work was focused on establishingthe suitable mathematical/statistical models for these purposes. It is anticipated that theresuIfing models can be incorporated into a software tool to provide rapid, variable-fidelity, aerothermal environments to predict heating along an arbitrary trajectory. Thiswork will support development of an integrated design tool to perform automated thermalprotection system (TPS) sizing and material selection.IntroductionRecent design experience with NASA's X-37 has demonstrated the need for consideringhigher fidelity aerodynamic heating early in the design cycle. In the case of X-37, thevehicle shape was optimized for aerodynamic performance and resulted in severeaerodynamic heating that forced costly redesign of the nose and wing surfaces andlowered flight margins. The availability of higher fidelity aerothermal analysis earlier inthe design cycle could have prevented these problems.Development of this technology impacts NASA's goal of reduced cost by enabling fasterand more optimized design cycles. Utilizing higher fidelity analyses earlier in the designwill avoid the delay and expense of late design changes. Optimizing the thermal-structural and TPS design in the process will minimize vehicle weight leading to lowerlaunch cost. The technology described is applicable across all next generationsystems/architectures for any vehicle configuration and includes metallic and ceramicTPS and hot structures.There will be two phases to this effort and they are model development and modelvalidation. The initial phase will be to explore and/or develop thestatistical/mathematical methods that can be used to transform the point wise aeroheatingpredictions of current tools to yield complete aerothermal environments through atrajectory corridor. The approach is intended to identify statistical/math models thatbest characterize and/or model a set of sphere stagnation data. Once several acceptablemodels have been identified, they will be tested in the second phase to see if they are ableto predict heating values within the normal trajectory of corridor values.2