The U.S. Navy has experimented with many approaches to design and build its ships. Using an existing design as the “parent” design, also referred to as “modified-repeat” design, is on its face an attractive option. Many acquisition executives, program managers and some ship design engineers believe that a design based on a parent has fewer technical risks than a new “clean sheet of paper” design and therefore the time and cost to design and build it will be reduced. They assume early in the ship acquisition program that “the design is mature”” and because of that fewer problems will be encountered in completing the design and savings will thus be accrued. Yet, a number of naval ships based on a parent design have in fact experienced unanticipated cost and schedule growth during construction as well as technical problems during their in-service life. The authors will examine some of these ship designs which were based on an existing design and/or prototypes and highlight the fallacies of such beliefs and assumptions. The authors will also briefly describe the development and use of more physics-based design tools during early stage design that can reduce the risks of a new clean sheet ship design through design space exploration and actual design maturation. The authors are convinced from our experience on over fifty major naval ship designs that much of the unbudgeted and unnecessary growth in the costs to produce naval ships can be attributed to poor design decisions during early concept design. Achieving a truly mature or stable ship design earlier in the design process is critical for ensuring successful ship design, acquisition, construction, and in-service outcomes.

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