The U.S. Navy plans to base most of its new Virginia class SSNs (nuclear attack submarines) at Pearl Harbor, Hawaii. Currently, fifteen SSNs are based at Pearl Harbor, almost all of them the older Los Angeles class boats. The navy is building 30 Virginias, and will initially base them at either Groton, Connecticut, or Pearl Harbor. This is to make it easier to stock spare parts and operate maintenance facilities. Eventually, Virginias will be sent to other bases, to replace retiring Los Angeles class SSNs. The navy now has 60 percent of its SSNs in the Pacific (and adjacent waters), and 40 percent in the Atlantic.
Currently, the U.S. has six Virginias in service, four under construction and nine on order. The United States has three classes of SSN. The mainstay of the American submarine force is still the 6,100 ton Los Angeles-class SSN. Sixty-two of these submarines were built, 45 of which remain in front-line service, making it probably the largest class of nuclear submarines that will ever be built. With four 21-inch (533-millimeter) torpedo tubes, it carries twenty-six weapons (either the Mk 48 ADCAP, the UGM-84 Harpoon anti-ship missile, or the BGM-109 Tomahawk). The last 31 Los Angeles-class SSNs add the Mk 45 vertical-launch system (VLS), which carries another twelve Tomahawks, making them closer to guided-missile submarines (SSGN).
The Seawolf-class of nuclear attack submarines stopped at three from a planned class of twenty-nine. The 8,600 ton Seawolf was designed as a super-submarine, designed to fight the Soviet Navy at its height. Carrying fifty weapons, and with eight 26-inch (660-millimeter) torpedo tubes, the Seawolf was designed for maximum performance. It delivered, posting a top speed of over 60 kilometers an hour, and remaining much quieter than the Los Angeles-class submarines. Reportedly, it is quieter at twenty-five knots than the Los Angeles-class submarines are at pier side.
With the cutback of the Seawolf to three ships, the Navy has gone with the Virginia-class submarine. Less-capable than the Seawolf (it is much like the Los Angeles-class attack subs, but with a lot of the more-advanced systems from the Seawolf-class subs, particularly the quieting and sonar systems), it was less expensive. The 7,700 ton Virginia-class submarines initially had a unit cost of $2.1 billion, but found a way to get the first six built for a total cost of $8.7 billion ($1.45 billion each). Like the Los Angeles-class, the Virginia-class submarines will be improved as the class is built. The most recent eight ordered are "Block III" boats, with over a hundred design changes, most of the major, some (in the vertical launch system and the bow sonar) are major.
Britain, France, Russia and China are all building new classes of SSNs that compete with the Virginias. The 7,800 ton British Astute class boats comes closest. The U.S. and Britain have long cooperated in the development of SSN technology. The moment, the U.S. has more of these "third generation" SSNs in service and on the way.