1136. Trade Studies: Foundation of the Design-To-Cost Process


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R A Butts, R E Johnston: 1136. Trade Studies: Foundation of the Design-To-Cost Process. 1976.



Design-to-Cost has been part of the Navy Tomahawk Cruise Missile since the start of the program. Early in the concept phase design-to-cost tradeoffs established the launch concept. Later activities refined the baseline and defined major configuration elements. As the program matures, design-to-cost will continue to guide selection of alternative solutions at greater levels of detail.
The heart of design-to-cost for the Tomahawk has been the trade study process. This is a dynamic process in keeping with the phased Tomahawk program approach. Emphasis shifts through a design-to, develop-to, and produce-to-cost sequence as the program matures. Following this sequence, the tradeoffs started at the system level and move to successively lower levels of detail. At the same time, costs (estimated and actual) and the configuration are tracked continuously to provide full traceability.
Although trade study emphasis changes with time, there is a continuing cycle in the process. Results of each trade study are compared with previous decisions. This ensures that an optimum mix is maintained and the performance remains with threshold boundaries.
General Dynamics Convair Division developed its Tomahawk candidate using this phased design-to-cost approach. A light weight, encapsulated flight vehicle was selected as the best balance of cost and performance for the submarine, ship, air and land array of mission launch platforms. An alternate was a bare, flying-torpedo concept. For the baseline submarine launched mission, cost and range for the Convair candidate and bare alternate were about equal but with a small advantage to the encapsulated missile. As other Navy-specified evaluation criteria were considered, encapsulation emerged as the better configuration choice. The separate capsule protected the missile and significantly improved chances for mission success. The capsule provided added safety and security aboard the submarine and reduced the effect of nuclear shock loads into the mission structure.
Maximum advantage for the encapsulated Tomahawk missile candidate came from alternative mission requirements. Ship and land-launch missions required a canister, which was an added development for a bare missile, but was only an adaption of the submarine baseline capsule.
Air launch required identical modifications but the encapsulated configuration provided a superior, lighter flight vehicle when the capsule was removed. Additionally, the tactical-mission version retained a high degree of commonality with the baseline strategic missile.
The combination of these factors resulted in Convair’s selection of an encapsulated cruise missile candidate judge superior within the concept of seeking an optimum balance of cost and performance.


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