The NSSN: A 21st Century Design

By William H. Kowenhoven and Frederick J. Harris

Nuclear submarine design for the 21st century embraces modern processes, technology, and tools—and the walls that once divided engineering disciplines have been replaced by multifunctional teams. Designers and shipbuilders have become interdependent, and the arms-length relationship between suppliers and the Navy is being replaced by cooperative teaming arrangements. The focus is on providing the most cost-effective, capable product

In 1989, Electric Boat Corporation initiated a comprehensive review of submarine design and construction with the goal of reducing nuclear submarine acquisition and life-cycle costs. We mapped the process step by step for each technical discipline and settled on a fundamental core process to eliminate inefficient work practices. We also evaluated design and construction methods in use by a broad spectrum of U.S. and international industries—aircraft, automobile, power-plant equipment, reactor-plant equipment, and shipbuilding—to improve our overall understanding. Review of the literature on concurrent engineering yielded additional insights. It should be emphasized that concurrent engineering means concurrency of the development of the design with the development of the construction method, so that the design is optimized to the build process. It does not mean concurrency of design development with actual ship construction.

Integral to the review was an evaluation of computer tools and software available to support next-generation submarine design and construction. Designers selected IBM/Dassault's computer-aided three-dimensional interactive (CATIA) digital design system and CATIA data manager (CDM) for the base set of computer-aided design, engineering, and manufacturing application programs. These integrated tools have produced the highest quality construction drawings and reduced the average design-change period from many days to a fraction of a day.

The comprehensive reviews, conducted over two years, identified the best features of current industrial practice, which we incorporated into the structure of the New Attack Submarine design process to ensure maximum design producibility. Designers, construction personnel from each major trade, and key support personnel are working together to produce digital design drawings that consider material availability and ease of construction.

Four elements characterize recent successful military and commercial programs: a clearly defined program concept; concurrent engineering; full use of a complete computer design data base; and an organizational structure that facilitates concurrent engineering. We are using all of these to design the New Attack Submarine.

Program concept . The objective of the New Attack Submarine Program is to produce a multi-mission, easy-to-upgrade submarine with the acoustic performance of the Seawolf (SSN-21), an acquisition cost equal to or lower than the cost of additional Los Angeles (SSN-688)-class submarines, and low life-cycle cost.

As part of the Electric Boat and Navy concept formulation, numerous alternatives involving significant parameter variations were studied in detail with appropriate tradeoffs considered before deciding on the baseline NSSN design characteristics. Figure 1 depicts some of these alternatives.

We used a structured evaluation process for platform integration to establish design parameters. While such studies are hardly new, the significant difference for the NSSN program is the use of computerized solid modeling tools, which allowed us to study many variations in a shorter period with greater accuracy than on past submarine programs. This process permits us to evaluate cost and overall mission effectiveness continually.

The submarine's modular design will facilitate quick upgrades to adapt to changing threats. New technologies and components can be inserted during construction or back-fitted to enhance operational performance and reduce life-cycle costs. The submarine will stay state-of-the-art throughout her life.

Serial production enhanced by technology insertion avoids prohibitively high acquisition and life-cycle support costs that would be incurred by one-of-a-kind platforms (at the number needed to maintain an attack submarine force of 45-55 boats). Weapons, personnel, equipment, and special gear will be linked to a common platform that reflects the latest quieting technology.

A series-produced, modular class pays only a small penalty in ship speed compared to an optimized prototype with similar displacement and the same shaft horsepower. If, for example, the NSSN hull length were increased 30 feet to accommodate a mission-specific hull section, her displacement would increase by about 800 tons and maximum ship speed would decrease only one-half knot. Even if the hull length/hull diameter ratio were reduced to match the lowest achieved for a nuclear attack submarine (8:1 on the Skipjack [SSN-585]), the top speed improvement would be less than one knot for the same displacement. Thus, the NSSN will pay only a small speed penalty for the inherent benefit of serial production of the core platform. Each mission-unique modified ship becomes a prototype for the mission capabilities installed, yet is based on proven platform technology.

The submarine's open-architecture command, control, communications, and intelligence systems are based on the use of commercial off-the-shelf technologies components and systems—which provide the greatest capability at the lowest cost. In addition, the use of structurally integrated enclosures facilitates upgrades without replacing cabinets and provides shock-proof mounting. These initiatives take advantage of the fast-paced growth in the commercial electronics and computer industries for insertion into operational and new construction ships. (See Figure 2.)

Concurrent engineering . Electric Boat and the Navy worked together in a common office for several months to develop the New Attack Submarine Ship Specification. Concurrent engineering brings together designers, engineers, shipbuilders, material personnel, planners, life-cycle support and environmental impact personnel, quality and cost personnel, equipment suppliers, representatives of Knolls Atomic Power Laboratory (KAPL), Bettis Atomic Power Laboratory, the Navy Supervisor of Shipbuilding at Groton, Connecticut, and other Navy representatives in an active design process.

Integrating functional specialties on design-build teams enables the shipbuilder to tailor the design to suit the planned construction method. This designer-shipbuilder interaction yields the most producible ship design.

All activities play a role in the design, which results in a shortened official review period, fewer design products requiring formal government approval, and fewer changes. (On the Seawolf , 27% of the construction drawings required government approval; on the NSSN, only 12% of the construction drawings require approval.)

Problems are being resolved during the development process rather than during construction; the integrated design involves all stakeholders up front, where it counts. Integration of government input not only reduced the number of formal government approvals, but also resulted in a reduction of the overall approval administration documents.

The concurrent engineering process empowers design-build teams to develop the products. Teams are given authority based on program objectives to ensure that their specific products are developed efficiently—a process developed in concert with design and construction labor unions. Union participation as partners in the entire concurrent engineering effort has fostered mutual respect.

Computerized design data bases . The NSSN uses a substantial computerized design data base to enable full integration of all program activities. (See Figure 3.) Each functional discipline has real-time access to the data base so that its design efforts can be performed concurrently rather than in the traditional series method. In addition, the centrally controlled data base ensures that everyone is working from the same baselines.

The primary interface between the design-build teams and the electronic design database takes place in electronic visualization system rooms. There are five rooms at Electric Boat and additional rooms at KAPL, Navy offices, and at key equipment suppliers' facilities. The systems provide full multimedia presentation of the design and permit interaction.

Team members, including equipment suppliers and customers, can see the details of the design at any stage of development and can interactively create, view, and modify design information. Immediate feedback enables team members to identify and correct problems.

Each week, electronic video conferences are conducted among Electric Boat, KAPL, and Navy offices to review the detailed design status, addressing problems that require discussion and joint resolution. In addition, common electronic data reduces the need for physical models and mockups.

With the design data available on a digital network, production can proceed without manual or graphical hardcopy transfer of data. The same data used for the design can drive numerically controlled manufacturing processes using the design database rather than physical drawings—the database can directly control cutting torches and pipe bending machines.

In addition, the database contains all the information needed to support current activities such as procurement, construction drawings, automated production, logistics, electronic mockups, and downstream activities such as repair, replacement, or modification. As such, it becomes a tool for initial design development, for ship construction, and for support throughout the life of the submarine.

Organization . Successful concurrent engineering requires an organization that can accommodate collocated or video-linked design-build teams by including all appropriate functional areas—and a structure that conveys to the teams the authority and responsibility for their products.

Electric Boat's New Attack Submarine Program Manager has overall ship design and construction responsibility for the program. The organizational structure instituted for multifunction, collocated designer-builder teams (see Figure 4), eliminates independent product development in favor of truly integrated product development. It includes about 75 system integration teams that design complete systems and structures throughout the ship; 15 major area teams are responsible for design of specific areas such as the command-and-control system module shown in Figure 5.

Four years into the program, the NSSN is taking shape—results to date:

  • A fully integrated master schedule defines and integrates all design and construction activities through ship delivery. This schedule provides each activity the ability to review and plan the work tasks two to three years in advance.
  • Shipboard systems have been simplified to reduce equipment.
  • A comprehensive cost-reduction program has been instituted covering design and construction processes for initial acquisition through life-cycle support. Approximately 4,000 good ideas have been identified and evaluated by Electric Boat, suppliers, and customer organizations.
  • Parts standardization has reduced the number of different parts. The NSSN uses fewer than 25% of the unique parts used in previous designs.
  • Early involvement of equipment suppliers in the equipment specification development allows the use of existing products and processes rather than forcing unique design and test requirements on suppliers.
  • Commercial and performance specifications rather than military specifications have been invoked where possible; 90% of the fasteners used on the NSSN are commercial specification.
  • Environmental considerations have been factored in for procurement, construction, and life cycle support activities.

In this era of change and imprecision, emphasis is shifting from weapon systems designed to counter specific targets and toward versatile systems that are effective against a range of threats and readily adaptable to evolving missions. Such is the case with the New Attack Submarine.

As the first U.S. nuclear submarine designed to face the certain, but indistinct, challenges of the next century, she must be adaptable to multiple missions and unforeseen scenarios worldwide. Her military capabilities must cover the warfare spectrum from covert surveillance and deployment of Special Forces to sudden attacks against land targets with precision missiles—and, she must be affordable.

As a major element of our naval power, the New Attack Submarine will contribute significantly to the United States' ability to control the seas and to influence events across the seas, well into the 21st century.

Mr. Kowenhoven is the New Attack Submarine Program Office Staff Engineer at Electric Boat; Mr. Harris is the New Attack Submarine Program Manager. 


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