Military


SSN-774 Virginia-class Construction

Given the rate at which submarines were built in the 1970s and 1980s (3 or 4 a year), and their life expectancy (about thirty years), there will be a significant number of submarines that require replacement in the early part of the 21st century.

To maintain the force structure recommended by the Joint Chiefs of Staff, construction of VIRGINIA Class submarines must ramp up in the near future to 2 submarines per year.

The New Attack Submarine Program Office is applying the lessons learrned from successful government and industry programs of similar scope and complexity to improve producibility and lower costs. Integrated Product and Process Development (IPPD) teams bring the combined experience of the shipbuilders, vendors, designers and engineers, and ship operators to bear on the ship design. The early involvement of production people on these teams is intended to provide a match between the design and the shipbuilder's construction processes and facilites, a smoother transition from design to production, and reduction in the number of changes during construction. The ship is designed using a state-of-the-art digital database, which allows members of the IPPD teams to work from a single design database and provides three-dimensional electronic mockups throughout the design process.

The Electric Boat Corporation of Connecticut is the lead design authority for the New Attack Submarine [NAS]. The build of the first submarine started at the company's Groton Shipyard in 1998, and funding has been allocated for the second and third submarines.

The 1993 Bottom Up Review decided not to consolidate all carrier and submarine construction in one shipyard due to concerns "about the resulting loss of competition as well as other long-term defense industrial base and national security implications that would result from having only one provider for two key classes of naval vessels..." The BUR directed construction of CVN 76 at Newport News Shipbuilding and the New Attack Submarine at Groton. The Navy's original plan approved in May 1995 was to build one ship in fiscal year 1998, a second ship in fiscal year 2000, and two ships per year beginning in fiscal year 2002--all at Electric Boat Corporation, Groton, Connecticut.

However, after the CVN 76 construction contract was awarded in FY 95, Congress questioned the BUR policy concerning New Attack Submarine. Congress rejected the Navy's plan, directing that the NAS would not be a serially-produced new class of nuclear attack submarines and further directing that Newport News Shipbuilding would participate in the future construction of such submarines. Public Law 104-106 directed the Navy to start construction of an NSSN at Newport News Shipbuilding and Drydock Company (Newport News) in 1999 and submit a plan for building four NSSNs between fiscal year 1998 and 2001, two of which were to be built by Electric Boat (one in 1998 and one in 2000) and two by Newport News (one in 1999 and one in 2001). According to the Navy, this change increased the estimated cost of developing and building 30 NSSNs by $3 billion. The Congressional plan stated that the best designs from each shipyard would form the basis for serial production of the first of a new class of next-generation submarines beginning in 2003 (amended to 2002 by the National Defense Authorization Act for Fiscal Year 1997 (Public Law 104-201)).

In December 1996, Electric Boat and Newport News Shipbuilding proposed to construct New Attack Submarines as a team, rather than as competitors. This was consistent with the Congressional direction to involve both nuclear submarine shipbuilders; to foster cooperation between the shipbuilders on both construction and design improvements; and to facilitate the cross pollination of knowledge and the insertion of advanced technology. Both shipbuilders would use Electric Boat's digital design database to construct New Attack Submarines and each shipbuilder would specialize in certain assemblies, thereby approaching single learning curve efficiencies. Both would initially deliver alternating ships with Electric Boat delivering the lead fiscal year 1998 submarine.

The Virginia-class submarines are being built at both Electric Boat (EB) and Newport News Shipbuilding (NNS). Each shipyard constructs about one half of each ship and for the most part repeats the build of the same sections each time. The constructed sections from each shipyard are barged to their counterpart, and the shipyard designated as the "delivery yard" for that ship completes the construction. The delivery yard is also where the pre-commissioning crew will be stationed, and where the ship will undergo an extensive pre-delivery certification test pro-gram. Therefore, the crew of Texas (SSN-775) (the second Virginia-class ship) will report to NNS; the crew of Hawaii (SSN-776) will report to EB; and the crew of North Carolina (SSN-777) will report to NNS. Homeports for the ships have not yet been assigned.

The five-to-six year submarine construction of VIRGINIA began in an enclosed facility at Quonset Point, RI where a multi-skilled work force fabricates modular hull sections and outfits them with systems, subsystems and components that are manufactured on-site.

These hull sections, weighing up to 1,400 tons, are barged to the Groton shipyard for final assembly. Also in Groton, the shipyard tests propulsion and other ship systems and performs sea trials, delivery and fleet maintenance.

Traditionally, labor, material, and equipment flowed through the shipyard to arrive at a single production site: the ship on an inclined way. But construction for Texas has been broken down into two dozen hull sections and modules, with each portion representing a key sub-assembly of the submarine's hull or equipment.

Modules are extensively outfitted and tested "off-hull" before the individual pieces a re loaded into the open ends of hull sections and joined to form the ship. This modular construction process is very similar to working with toy building blocks, but on a gigantic scale. At Newport News the ground-work for modular construction was started in the Ring Module Shop, where initial construction of steel hull sections creates tanks, foundations, and deck assemblies.

Electric Boat's Quonset Point Facility in Rhode Island also contributes groundwork for Texas by building hull rings and subsections outfitted with pipe, machinery, and electrical components. Electric Boat will send 11 major ship sections to Newport News on an ocean-going barge called the Sea Shuttle. Some of these modules will weigh several hundred tons and will ultimately be joined with others built by Newport News to create the Texas. The modules from the Ring Module Shop and Electric Boat will be moved to the MOF, a ten-story building with four large bay doors. Here the work of thousands of employees comes together as major systems and large components are systematically installed and outfitted. Systems and components vary in size - from entire decks and huge condensers to small electric motors and switches. All arrive at the MOF ready for installation on the modules and ultimately in the various hull cylinders.

After each module is completed and loaded into the hull cylinders, four-wheel electric transfer cars are rolled under the hull ring's strongbacks. Hydraulic jacks on the cars lift the large sections of the ship, which are then wheeled into place and welded together to form part of the complete hull. After the modules are joined and the ship's systems are interconnected, transfer cars under the ship's strongbacks will lift the vessel simultaneously and roll the ship on rails (at four feet per minute) to the outboard ways for additional outfitting and testing.

After Texas is christened in 2004, it will be transported westward to the edge of the James River and moved onto the yard's 640-foot floating dry dock. As the ship is transferred from land, the floating dry dock's onboard computer receives input from load sensors, tide gauges, vessel position sensors, draft gauges, and tank level sensors to control 40 onboard ballast tanks so the dock remains level during the loading process. After Texas is loaded, the floating dry dock will move to a nearby 70-foot deep basin where the dock will submerge, and the submarine will float free. Tugboats then will pull the ship out of the dock and to a pier in the South Yard for additional testing in preparation for the ship's sea trials and final delivery to the Navy.





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