April 21, 2012: The American SSN (nuclear attack sub) USS Seawolf has returned to service after a 31 month, $280 million refurbishment. The Seawolf entered service in 1997, and SSNs typically undergo a major maintenance and upgrades after about 20 years. The Seawolf went in for this kind of work early, and the refurbishment was more extensive (and expensive) than usual for regular Depot Modernization Period work. This may have to do with the fact that the Seawolf was the first of its class. This might indicate the installation of some special equipment for intelligence missions. A sister ship, the USS Carter, was extensively outfitted as an intelligence and special operations submarine. The navy admitted what the Carter was rebuilt for but for even more sensitive missions you would want to withhold all details.
The twenty-nine 9,000 ton Seawolf-class SSNs were supposed to replace the Cold War era Los Angeles boats but Seawolf proved too expensive. Only three were built. The Seawolf was designed for the Cold War, carrying fifty weapons (torpedoes, cruise missiles, or Harpoon anti-ship missiles) for its eight 26-inch (660-millimeter) torpedo tubes. Seawolf was fast (top speed of over 60 kilometers an hour) and much quieter than the Los Angeles boats. To replace the un-built Seawolfs the 7,800 ton Virginia-class was designed. Think of it as a Los Angeles size hull with a lot of Seawolf technology installed. The Virginia-class boats ended up costing about half as much as the Seawolfs. But that was largely possible because the Virginias used a lot of the new technology developed for Seawolf.
The U.S. currently has three classes of SSN. Most are the 6,900 ton Los Angeles-class SSNs. Sixty-two of these submarines were built, and 43 are still in service. Armed with four 21-inch (533-millimeter) torpedo tubes, they carry twenty-six weapons for those tubes (either the Mk 48 torpedoes or BGM-109 Tomahawk cruise missiles). The last 31 Los Angeles-class SSNs added the Mk 45 vertical-launch system (VLS), which carries another twelve Tomahawks. If built today these late model Los Angeles class boats would cost about $1.5 billion each. There are eight Virginias in service and another 24 planned.