With the number of foreign diesel-electric/air-independent propulsion submarines increasing yearly, the United States Submarine Force relies on its technological superiority and the speed, endurance, mobility, stealth and payload afforded by nuclear power to retain its preeminence in the undersea battlespace.
The Navy has three classes of SSNs in service. Los Angeles (SSN 688)-class submarines are the backbone of the submarine force with 40 now in commission. Thirty Los Angeles-class SSNs are equipped with 12 Vertical Launch System tubes for firing Tomahawk cruise missiles.
The Navy also has three Seawolf-class submarines. Commissioned on July 19, 1997, USS Seawolf (SSN 21) is exceptionally quiet, fast, well-armed, and equipped with advanced sensors. Though lacking Vertical Launch Systems, the Seawolf class has eight torpedo tubes and can hold up to 50 weapons in its torpedo room. The third ship of the class, USS Jimmy Carter (SSN 23), has a 100-foot hull extension called the multi-mission platform. This hull section provides for additional payloads to accommodate advanced technology used to carry out classified research and development and for enhanced warfighting capabilities.
The Navy continues to build the next-generation attack submarine, the Virginia (SSN 774) class. Twelve VIRGINIA's have been commissioned to date and they will replace Los Angeles Class submarines as they retire. The Virginia class has several innovations that significantly enhance its warfighting capabilities with an emphasis on littoral operations. Virginia class SSNs have a fly-by-wire ship control system that provides improved shallow-water ship handling. The class has special features to support SOF, including a reconfigurable torpedo room which can accommodate a large number of SOF and all their equipment for prolonged deployments and future off-board payloads. The class also has a large lock-in/lock-out chamber for divers. In Virginia-class SSNs, traditional periscopes have been supplanted by two photonics masts that host visible and infrared digital cameras atop telescoping arms. With the removal of the barrel periscopes, the ship's control room has been moved down one deck and away from the hull's curvature, affording it more room and an improved layout that provides the commanding officer with enhanced situational awareness. Additionally, through the extensive use of modular construction, open architecture, and commercial off-the-shelf components, the Virginia class is designed to remain state-of-the-practice for its entire operational life through the rapid introduction of new systems and payloads.
As part of the Virginia-class' third, or Block III, contract, the Navy redesigned approximately 20 percent of the ship to reduce their acquisition costs. Most of the changes are found in the bow where the traditional, air-backed sonar sphere has been replaced with a water-backed Large Aperture Bow (LAB) array which reduces acquisition and life-cycle costs while providing enhanced passive detection capabilities. The new bow also replaces the 12 individual Vertical Launch System (VLS) tubes with two large diameter 87-inch Virginia Payload Tubes (VPTs), each capable of launching six Tomahawk cruise missiles. The VPTs simplify construction, reduce acquisition costs, and provide for more payload flexibility than the smaller VLS tubes due to their added volume. The design changes were successfully proven out during NORTH DAKOTA's Builder Sea Trials in August 2014. Block III hulls include the eight ships procured from Fiscal Years 2008 through and 2013 (SSN hulls 784 - 791.)
Block IV submarines, which are comprised of the 10 submarines scheduled to be authorized in Fiscal Years 2014 - 2018 (SSN hulls 792 - 801), incorporate design changes focused on Reduced Total Ownership Cost (RTOC). By making these smaller-scale design changes to increase the component-level lifecycle of the submarine, the Navy will increase the periodicity between depot maintenance availabilities and increase the number of deployments. Blocks I-III Virginias will undergo four depot maintenance availabilities and conduct 14 deployments. Block IV RTOC efforts reduced the planned availabilities by one to three and increased deployments by one to 15. The Navy refers to this as 3:15.
The next major change will be incorporation of the VIRGINIA Payload Module (VPM) in Block V submarines. VPM, currently in the early concept development phase, will insert four additional payload tubes - each capable of carrying seven Tomahawk cruise missiles - into the Virginia class design. The VPM tubes will be very similar to the VPTs utilized on Block III and forward ships. By using these tubes in the VPM, the Navy leverages mission proven components for the new module, thereby minimizing design and cost risk.
From U.S. Navy Fact File