SSN Seawolf Class Attack Submarine, USA

The Seawolf was conceived as a faster, better-armed eventual replacement for the Los Angeles Class nuclear-powered attack submarines.

The first of class, the Seawolf (SSN21), was ordered from the Electric Boat Division of General Dynamics, Connecticut, in January 1989 and commissioned in July 1997. Connecticut (SSN22) was commissioned in December 1998. The third, Jimmy Carter (SSN 23), is to be modified to improve payload carrying and underwater manoeuvrability.

The alterations to the design will include modifications to the ballast control, mission management spaces and the creation of a flexible ocean interface known as a 'wasp waist', which will enable the deployment and recovery of payloads without the use of torpedo tubes. Other additions include a new high-capacity communications mast and ROV handling system. The Jimmy Carter was launched in June 2004 and commissioned in February 2005.

The Seawolf was a product of the Cold War, conceived to maintain the USA's acoustic advantage over Soviet submarines. With the end of the Cold War and the change of emphasis to littoral operations, the cost of the Seawolf submarines was judged prohibitive and the programme was curtailed in favour of the smaller and cheaper Virginia Class New Attack submarines.

Seawolf design

The Seawolf's modular design introduces important improvements and innovations. It has greater manoeuvrability than the Los Angeles Class, space for later upgrades and weapons developments, and better sonars.

The Seawolf has a submerged displacement of 9,137t dived (12,139t for the Jimmy Carter), and 8,060t surfaced. Full acoustic cladding has been installed. It has a maximum speed of 35kt dived, and a 'silent' speed of 20kt. It has a crew of 116 personnel, including 15 officers. With a diving depth of 610m, it has been designed with a sub-ice capability, with retractable bow planes.

Combat system

The combat data system is a Lockheed Martin BSY-2 with a network of some 70 or so 68030 Motorola processors. This being replaced by the Raytheon AN/BYG-1 combat system. Weapons control is managed by the Raytheon mk2 fire control system.

Missiles

Like the improved Los Angeles Class, the Seawolf does not have any external weapons. The submarine is armed with both the land-attack and anti-ship version of the Tomahawk missile from Raytheon. The land-attack Tomahawk has a range of 2,500km. A TAINS (Tercom aided inertial navigation system) guides the missile towards the target flying at subsonic speed at an altitude of 20m to 100m.

Tomahawk can be fitted with a nuclear warhead,a;though it is not normally carried. Block III improvements include an improved propulsion system and Navstar global positioning system (GPS) guidance capability. The anti-ship Tomahawk missile is equipped with an inertial guidance and an active radar and anti-radiation homing head. The range is up to 450km.

The first underwater launch of the new Raytheon Tactical Tomahawk block IV missile took place in November 2002. Block IV includes a two-way satellite link that allows reprogramming of the missile in flight and transmission of battle damage indication (BDI) imagery. The missile entered service with USN surface ships in September 2004.

The Seawolf Class also carries the Harpoon anti-ship missile from Boeing. Sub-harpoon uses active radar homing to deliver a 225kg warhead. The range is 130km and the speed is high subsonic.

Torpedoes

Seawolf has eight 660mm torpedo tubes for launching torpedoes and missiles. 50 missiles / torpedoes are carried. The Gould mk48 ADCAP torpedoes combat both high-performance surface ships and fast deep-diving submarines. The torpedo has a 267kg warhead. It is capable of operating with or without wire guidance and uses either or both active and passive homing. Range is 50km (active) and 38km (passive)

Countermeasures

Countermeasures include the Northrop Grumman WLY-1 torpedo decoy system and a GTE WLQ-4(V)1 electronic countermeasures (ECM) system.

Sensors

The submarine's sonar suite is the BQQ 5D with bow-mounted active / passive arrays and wide aperture passive flank arrays.

Also fitted are TB-16 surveillance and TB-29 tactical towed arrays, which will be replaced by the TB-29A thin-line towed array being developed by Lockheed Martin, and BQS 24 active sonar for close range detection.

The Seawolf submarines are being upgraded with the Lockheed Martin AN/BQQ-10(V4) sonar processing system under the acoustic-rapid commercial-off-the-shelf insertion (A-RCI) programme.

BPS 16 radar, operating at I band, is fitted for navigation.

Propulsion

The nuclear-powered Seawolf has a GE PWR S6W reactor system, two turbines rated 52,000hp (38.8MW), a pumpjet propulsor, a single shaft, and one secondary propulsion submerged motor.