Building Surrogate Models for Capability-Based Evaluation: Comparing Morphing and Fixed Geometry Aircraft in a Fleet Context

Recent advances in adaptive structures and advanced compact actuators have renewed interest in variable geometry aircraft that can change shape in flight to obtain better performance during dissimilar flight conditions. These new morphing aircraft may allow for shape changes beyond the current variable sweep and variable camber available in the F-111 or F-14 aircraft. Because of the potential for a wider range of shape changes, significant effort has been put forth to develop strategies for the conceptual sizing of such vehicles, including the “morphing as an independent variable” sizing approach that allows the use of continuous optimization techniques to size the morphing aircraft. Although these previous aircraft sizing studies have predicted advantages for variable geometry in performance and weight by conventional design comparisons, this paper extends the evaluation by investigating the effectiveness of a morphing aircraft design in a fleet of aircraft. A key feature of this work involves creating surrogate models to approximate the capability of an aircraft or a fleet of aircraft as a function of parameters describing the aircraft design mission. These capability surrogate models, coupled with similarlyconstructed cost models, enable the design of a best fleet in which the number of aircraft and the design parameters of the aircraft may be determined simultaneously. The approach here uses some initial simplifications to the approach and relies upon enumerating a number of discrete choices, but it suggests that more formalized approaches could be used for this kind of aircraft fleet design problem. For the morphing aircraft application, comparisons of the best fleet of morphing aircraft offer improvements in capability and cost over the best fleet of fixed-geometry aircraft for an example search-and-find concept of operations.