Toward a Lightweight Design Philosophy for High‐Speed Sealift Ships

Abstract

AbstractThe US Navy's new Center for Innovation in Ship Design (CISD) completed in 2004 a Concept Formulation (CONFORM) study, under the sponsorship of the Naval Sea Systems Command, of a lightweight High‐Speed Sealift (HSS) Ship as part of the Navy's Sea Basing concept studies. The objective of the ship CONFORM study was to develop design concepts that would reduce weight in order to facilitate higher speeds. These lightweight design concepts were looked at in the context of total‐ship concepts. CISD investigated both near‐term product and process technologies, where the Navy would have enough confidence to begin the design of a lightweight high‐speed ship within 5 years. Importance was given to developing a lightweight, high‐speed design philosophy consisting of a Sea Basing “System of Systems” (SOS) approach driven by a Concept of Operations (CONOPS). This top‐down approach, or systems architecting, included functional analyses to determine necessary military capabilities, functional allocation of these capabilities to the various component systems of the Sea Basing System, and concept design analyses to determine the best total ship architecture for a lightweight, HSS ship. Concurrent with the SOS top‐down approach was a bottom‐up approach of assessing emerging technologies that would enable optimum total ship architectures for lightweight, high‐speed ships. The ship CONFORM study was conducted by the Light Weight, Total Ship Architecture, Design Concepts Innovation Cell, a multi‐disciplinary team comprised of ship designers, structural engineers, shipbuilders, and student interns. By applying a top‐down, systems engineering process of functional analysis and functional allocation, the Innovation Cell quickly learned that the easiest way to reduce ship weight was to allocate ship functions to the Sea Base through Operational Innovations. The authors highlight that many traditional shipboard systems and equipment that a transport ship would normally carry to provide necessary services aboard the ship would have to be located on and provided by the Sea Base. Also, the derivation, rationale, and validity of every explicit and derived design requirement were questioned. Because hull structure is the largest contributor to full‐load displacement, emphasis was placed on taking advantage of new manufacturing technologies and joining methods such as laser welding to enable the development of near‐term, innovative, and lightweight structural design concepts such as sandwich panels. The authors discuss the significant weight reductions and cost/producibility aspects of these innovative structural design concepts, as well as the results of a peer review by the Navy's technical authorities. In addition to describing this lightweight, high‐speed design philosophy, rationale is also presented that leads to the overwhelming conclusion for the need to develop a near‐term, lightweight, high‐speed, oceangoing Innovative Naval Prototype ship. Technical aspects of the prototype ship are presented to support the objective to capitalize on large‐scale, transformational system technologies, such as long slender stabilized monohull forms, 60–70‐MW axial flow waterjets, and lightweight structures, in order to resolve important technical and operational problems that will enable significant gains in Sea Basing warfare capabilities.