High-speed civil transport design space exploration using aerodynamic response surface approximations

A method has been developed to generate and use polynomial approximations to the range and cruise drag components in a highly constrained, multidisciplinary design optimization of a high-speed civil transport (HSCT) configuration. The method improves optimization performance by eliminating the numerical noise present in the analyses through the use of response surface methodology. In this implementation quadratic polynomials are fit within variable bounds to data gathered from a series of numerical analyses of different aircraft designs. Because the HSCT optimization process contains noise and suffers from a nonconvex design space even when noise is filtered out, multiple optimization runs are performed from different starting points with and without the response surface models in order to evaluate both their effectiveness as surrogate functions and as a design exploration tool. The alternative method used is variable complexity modeling (VCM). It is shown that response surface methodology facilitates design space exploration, allowing improvements in terms of both convergence performance and computational effort when multiple starting points are required, although using VCM usually produces better final designs.