The MDO approach to design has become a powerful vehicle for broad exploration of design space at relatively low cost. An example is the development of hypersonic vehicles for space access and defense applications, where there is a complex interdependence of vehicle structure and aerodynamic and thermal loads; static and dynamic structural deflections; propulsion system performance and operability; and vehicle control. Since many conditions of hypersonic flight cannot reasonably be replicated in any current or foreseeable wind tunnel, designs are not fully validated until actual flights are conducted. Thus the integration of validated analytical design tools with automated data transfer between disciplines in an MDO platform is essential for arriving at realistic but innovative and high-performing solutions. A tool integration scheme used by Boeing Phantom Works for the design of hypersonic vehicles is shown in Figure 2-2-1. This MDO scheme could, for example, be used to design an air-breathing, reusable, hypersonic flight vehicle, where strong interactions between aerodynamics, propulsion, aerothermal loads, structures, and control have a substantial impact on the optimal shape of the entire vehicle. With an MDO platform, thousands of potential vehicle shapes can be explored within the time frame of days (see Figure 2-2-2). Materials tools are notably absent from the MDO tool set (Figure 2-2-1).

FIGURE 2-2-1 Boeing’s integration of analytical tools for design of hypersonic vehicles. SOURCE: K.G. Bowcutt, “A perspective on the future of aerospace vehicle design,” American Institute of Aeronautics and Astronautics Paper 2003-6957, December 2003.