Effect of Mission Requirements on the Economic Robustness of an HSCT Concept
Mavris, Dimitri N.
Schrage, Daniel P.
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Design for robustness and its subset design for economic robustness and viability are two areas in current design methodology and optimization research attracting a lot of attention, as the increasing number of publications and industry position papers in this field indicate. In fact, these publications attempt to address the paradigm shift taking place in industry, where design for performance is being replaced by design for affordability. That is designing and optimizing a system for a high yield while reducing the variation from that optimum yield. The study presented here can be viewed as a proof of concept for a proposed approach to design for robustness, called Robust Design Simulation (RDS). The paper outlines an alternative approach to Taguchi's, assigning probability distributions to uncontrollable factors (noise variables) which result in a distribution for the design objective instead of a point solution. The study also illustrates that indeed one is able to manipulate the mean and variance of the design objective concurrently, hence, optimizing a new Overall Evaluation Criterion (OEC) that is comprised of both the mean and variance of the design objective. The High Speed Civil Transport (HSCT) was utilized as an illustrative case to demonstrate the implementation of RDS. The objective of this case study is to show and quantify the effects of mission and aircraft sizing parameters on the mean and variance of direct and total operating cost as well as the required average yield per revenue passenger mile ($/RPM). Finally, the optimal mission requirement settings which yield an OEC that concurrently minimizes the mean $/RPM as well as its variance are identified for the HSCT configuration studied.