Boeing and United States Air Force Research Lab (AFRL) have conducted a research program to study current production structural analysis methods for use in hypersonic vehicle design and analysis. The focus was to identify, verify and quantify knowledge gaps in understandings of design environment, high temperature material behavior, and analysis approach in the prediction of structural response and life of hypersonic structures. Phase I of the program identified these knowledge gaps by performing thermal and stress analyses and sizing on a hypersonic reference vehicle with design loads and thermal environment from a representative flight trajectory. In Phase II, the knowledge gaps were verified through detailed sizing and analysis of four vehicle surface panels. This paper focuses on the knowledge gaps associated with the panel dynamic response to thermal-acoustic loads. This knowledge gaps identified in Phase I were verified through detailed finite element analyses of a panel using both linear frequency response and nonlinear transient dynamic analysis. The study included a temperature field for loads and material properties. The acoustic loading was defined from a typical acoustic spectrum for Turbulent Boundary layer excitation. The dynamic analysis related knowledge gaps were discussed and comparisons of linear and nonlinear analysis results were made.
The paper presents a multi-disciplinary design/optimization method for the conceptual design of a hydrofoil based fast ship. The method is used to determine the maximum achievable lift-to-drag ratio (L/D) of an isolated foil-strut arrangement (hopefully greater than 50) at high transit speeds (greater than 75 knots) while lifting masses of 5,000 and 10,000 tons. First, the tools necessary for the study are presented. They comprise a panel method to compute three-dimensional flows around arbitrary configurations with a model for the free surface, a foil cross-section optimization tool, a strut cross-section design tool, and a structural analysis tool. The computational tools are then integrated into a multi-disciplinary design/optimization approach, which is applied to the design of single foil and biplane configurations. Results show that the goal of L/D = 50 is achievable for 75 knots (assuming that techniques can be developed for reducing the skin friction drag to a quarter of its nominal value) and, that for 90 knots, L/D ratios around 45 can be reached. The corresponding break horsepower requirements for 10,000 tons are around 130 khp and less than 200 khp, respectively.
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