The year 2011 was a watershed for the Ohio Replacement Program Office. The Milestone A Acquisition Defense Memorandum, issued 10 January 2011, officially authorized the Ohio replacement SSBN to enter the technology development phase. Over the past year, the Ohio Replacement Program worked to solidify requirements, a key step in finalizing the service-approved Capability Development Document. The program also has progressed in the development of common missile compartment (CMC) quad-pack ship specifications and the definition of propulsion-plant and hull/mechanical/electrical (HM&E) systems, and completed significant prototyping work.
The current configuration of the Ohio replacement is an SSBN with 16 87-inch-diameter missile tubes, a 43-foot-diameter hull, fairwater planes, electric-drive propulsion, X-stern, accommodations for 155 personnel, and a common submarine radio room tailored to the SSBN mission. The vessel will utilize the existing Trident II (D-5) life-extended strategic-weapon system (SWS).
Through small-scale model testing, the program postulated various hull configurations, including bow planes and stern configurations that included H-stern, cruciform with vertical stabilizers, and hybrid X-stern before finally deciding on the X-stern. A CMC design will be shared by both the United States and the United Kingdom as it moves forward with its successor program that will replace the current British Vanguard-class SSBNs. Recognizing missile-compartment construction is a major cost-contributor to an SSBN construction project, the Ohio Replacement Program is developing a missile-compartment build strategy to leverage modular-construction techniques that will help maximize cost savings as compared to the Ohio class. The previous “stick-built” method of construction used in all previous SSBN classes involved fabricating the hull first, then cutting the hull to insert the missile tubes. After installation in the hull, the shipbuilders would outfit the missile tube. This is a time-consuming, labor-intensive process with a majority of the outfitting being done less optimally within the hull.
During the past year, the Navy successfully completed prototyping the Integrated Tube and Hull (ITH) build strategy for the missile compartment. General Dynamics Electric Boat Division competitively awarded subcontracts to four companies, two in the United States and two in the United Kingdom, to produce prototype missile tubes. This process allowed the Navy to verify that the industrial base can produce large missile tubes to tight tolerances, and it creates the opportunity to compete the production work for the missile tubes that will ensure the best value to the Navy.
Employing this build strategy, missile-tube vendors will supply tubes with the upper portion of the pressure hull, known as the crown, to the shipbuilder. The shipbuilder then outfits the missile tubes off-hull and welds the four crown assemblies together using the E-fixture that maintains tube alignment while welding. The four tubes then are welded into a section of the pressure hull to form a “quad pack” that is joined with other such foursomes to create the missile compartment. The successful completion of the ITH build-strategy prototype in 2011 proved the effectiveness of this modular assembly method.
In January 2012, Secretary of Defense Leon Panetta announced a two-year program delay with lead-ship construction starting in Fiscal Year 2021 instead of 2019. This two-year delay will slow the rest of ship-design development consistent with reduced near-term funding while allowing more time for risk-reduction and cost-reduction efforts to proceed. The program will maintain key elements of the baseline design schedule to support the CMC for the U.K. successor program including the SWS development and propulsion-plant design progress to support the later construction start. These elements include ship specifications, key HM&E system definition and diagrams, design-for-affordability efforts, auxiliary machinery room I and II, integrated product-design environment, and select CMC support systems and arrangements.