MILNET: U.S.S. Seawolf SSN-21

U.S. Navy Fact File

During the cold war, U.S. subs were in constant play in a deadly game of hide and seek with Soviet and Chinese "boomers" as the missile subs are called. With the aid of underwater sonar detection nets such as the U.S. SOSUS array, U.S. subs would be deployed to intercept Soviet or Chinese submarines as they were detected. Once the sub aquires the submarine, it is then tracked, hopefully through the remainder of is mission.

The objective was to "tail" the boomer until such time as it returned home, or in the event of war, moved near the surface and prepared to launch its SLBMs at the U.S. or its allies.

Today, while the submarine threat appears to be lessened considerably, U.S. submarines continue the patrol, still finding their prey at work probing U.S. defenses. With a smaller target force, the U.S. subs must make use of each contact in order to continue to train and deter. Russian and Chinese submarines still conduct covert underwater missions, and certainly other third world diesel powered submarines threaten battlegroups in areas such as the Arabian Gulf.

The Seawolf class boats are fitted with Tomahawk missiles launched via tube or via Vertical Launch System (VLS) tubes embedded in the deck

All U.S. submarines are able to communicate both from the surface or near the surface as well as submerged. Underwater communication takes place via a underwater transponder and hydrophone, and a trailing wire Ultra Low Frequency antenna. The ULF system is immune to effects of sun spots or Electromagnetic Pulse or Ionization of the atmosphere following a nuclear blast, thus provides long distance communcation for the submarine while deployed. This ensures the submarine can receive its orders regardless of the wartime status.

Speculation is that satellite burst communications are used while near the surface so that a nuclear sub does not give up its position easily.

Underwater detection is accomplished by sophisticated, computer assisted, hydrophone gear, part of which is hull mounted as well as being fitted on a towed sonar array. Computers pick out man-made noises from the "symphony" of sounds made by sea creatures, and analyzes these anomolies for recognziable submarine sounds such as propeller motion, underwater hatches opening and closing, or even powerplant noises or ballast tank activity. The theory is that every submarine has its own unique underwater audio signature, and the stealthy attack sub keeps a database of these signatures for use in identifying their prey.

To fix a target for firing purposes, a large emitter dish is mounted in the bow of the submarine, which gives off a very loud underwater tone which moves through water somewhat slower than the speed of sound, impacts the target vessel, and is reflected. The reflected tone is analyzed by computers on the attack sub, and distance and bearing are computed. This allows a "firing solution" to be computed, and a torpedo, or sub-Asroc can be launched at submerged target, or Mk-48 torpedo, sub- Harpoon, or anti-shipping version of the Tomahawk cruise missile can be launched at surface targets.

For land attack, the Seawolf attack subs can launch the Tomahawk TLAM-D (Tactical Land Attack Missile), which flys a low and circuitous route to its target to avoid radar detection. This technique was proven quite useful during the Gulf War in 1991, as Los Angeles class subs performed this underwater attack on targets in Iraq, and then changed position to avoid retalation. Shots were fired from the Arabian Gulf and the Red Sea.

Nuclear Power Plant Propulsion System

For propulsion, the Seawolf class boats use a single nuclear reactor and a steam turbine which drives a geared shaft which in turn drives a screw which in turn drives the screw through the water.

 The powerplant (shown in the diagram above) is made up of two water systems, one, the primary, which is heated by the reactor, and the secondary which is heated via a heat exchanger, that actually is heated into steam and drives the turbine. In this way, water that comes in contact with the nuclear core is isolated from that which is used for propulsion. This increases the safety of ship and crew.

Below are the specifications for the U.S.S. Seawolf

U.S.S. Seawolf SSN-21

Nuclear Powered Attack Submarine

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