Los Angeles class

   Comprising the largest number of nuclear-powered vessels built to one design, the Los Angeles class couples the speed advantage of the elderly Skipjack class with the sonar and weapons capability of the Permit and Sturgeon classes.

   The significant increase in size is mainly the result of doubling the installed power available by the fitting of a new reactor design, the S6G pressurized-water reactor based on the D2G reactor fitted in the nuclear-powered cruisers of the Bainbridge and Truxtun classes. Reactor refueling takes place every 10 years.

   The boats originally carried the BQQ-5 passive/active search and attack sonar system. From the USS San Juan (SSN-751) onward, the BSY-1 system was fitted. The USS Augusta and the USS Cheyenne were both fitted with a BQG-5D wide-aperture flank array. All boats have the BQS-15 active close-range high-frequency sonar for ice detection. Other sensors include a MIDAS (Mine and Ice Detection Avoidance System) first fitted in the San Juan, and all the boats from this onward were fitted with sound-reducing tiles and hydroplanes relocated from the fin to the forward part of the hull.

   Thanks to its electronic systems, the class has proved to be an exceptionally good ASW platform although, on one occasion on the first out-of-area Alpha I deployment, the Soviet boat was easily able to outrun a trailing Los Angeles-class boat off Iceland just by using its superior underwater speed. Against more conventional Soviet-designed nuclear-powered boats the success rate of detection and tracking is quite high. The advanced BQQ-5 system on one occasion acquired and held contact with two Soviet Victor-class SSNs for an extended time.

  The class features a very potent weapons array including the Tomahawk Tactical Land Attack Missile (TLAM) with a range between 900 and 1 700 km (559 and 1 056 miles). Current versions of the missile are the TLAM-C version, which can carry a single 454-kg (1 000-lb) warhead and the TLAM-D which carries a submunition payload to 900 km. The standard unitary HE warhead can also be replaced by a 318-kg (692-lb) shaped-charge warhead. In order to overcome the problem of limited weapons stowage, all boats from the USS Providence (SSN-719) onward are fitted with a vertical launch system in which the launch tubes for the TLAMs are placed outside the pressure hull behind the sonar array. Although the Tomahawk is nuclear-capable, such weapons are not now deployed on a routine basis.

   Furthermore, the boats can also carry the 21-in (533-mm Mk 48 active/passive homing torpedo with a wire-guidance option. This guidance is suitable for ranges up to 50 km (31 miles) or 38 km (23 miles) in the active or passive modes respectively. The torpedo has a 267-kg (588-lb) warhead, and 26 Mk 48 weapons can be carried by a Los Angeles-class boat though another load is 14 torpedoes and 12 tube-launched TLAMs. These are fired out of four tubes placed amidships in the vessel. The Los Angeles class has already participated in operations in Iraq, Kosovo and Afghanistan. Furthermore, the boats have also continued their under-ice operations, and in mid-2001, the USS Scranton (SSN-756) surfaced through the Arctic ice cap. Eleven of the class have been retired.