Nasa systems engineering handbook fundamentals of

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Unformatted text preview: for use in design optimization. Even without knowing how to trade effectiveness for cost, designs that have lower cost and higher effectiveness are always preferred. NASA Systems Engineering Handbook Fundamentals of Systems Engineering tradeoff space between effectiveness and cost. A graph plotting the maximum achievable effectiveness of designs available with current technology as a function of cost would in general yield a curved line such as the one shown in Figure 1. (In the figure, all the dimensions of effectiveness are represented by the ordinate and all the dimensions of cost by the abscissa.) In other words, the curved line represents the envelope of the currently available technology in terms of cost -effectiveness. Points above the line cannot be achieved with currently available technology e that is, they do not represent feasible designs. (Some of those points may be feasible in the future when further technological advances have been made.) Points inside the envelope are feasible, but are dominated by designs whose combined cost and effectiveness lie on the envelope. Designs represented by points on the envelope are called cost-effective (or efficient or non-dominated) solutions. Design trade studies, an important part of the systems engineering process, often attempt to find designs that provide a better combination of the various dimensions of cost and effectiveness. When the starting point for a design trade study is inside the envelope, there are alternatives that reduce costs without decreasing any aspect of effectiveness. or increase some aspect of effectiveness with Figure 1 -- The Enveloping Surface of Non-dominated Designs. out decreasing others and without increasing costs. Then, the system manager's or system engineer's decision is easy. Other than in the sizing of subsystems, such "win-win" design trades are uncommon, but by no means rare. When the alternatives in a design trade study, however, require trading cost for effectiveness, or even one dimension of...
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This document was uploaded on 02/26/2014 for the course E 515 at University of Louisiana at Lafayette.

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