Los Angeles-class submarine

USS Asheville arrives at Naval Base Point Loma, California in November 2005.
Class overview
Builders:	Newport News Shipbuilding General Dynamics Electric Boat
Operators:	United States Navy
Preceded by:	Sturgeon-class attack submarine
Succeeded by:	Seawolf-class attack submarine
Cost:	$900 million [1990 prices]
Built:	1972–1996
In commission:	1976–present
Completed:	62
Active:	39
Retired:	23
General characteristics
Displacement:	Surfaced: 6,082 tonnes (5,986 long tons) Submerged: 6,927 tonnes (6,818 long tons)
Length:
Beam:
Draft:	31 ft (9.4 m)
Propulsion:	1 GE PWR S6G nuclear reactor, 2 turbines 35,000 hp (26 MW), 1 auxiliary motor 325 hp (242 kW), 1 shaft
Speed:	Surfaced: 20 knots (23 mph; 37 km/h) Submerged: +20 knots (23 mph; 37 km/h) (official), 33+ knots (reported)
Range:	Refueling required after 30 years
Endurance:	90 days
Test depth:	950 ft (290 m)
Complement:	129
Sensors and processing systems:	BQQ-5 Suite which includes Active and Passive systems sonar, BQS-15 detecting and ranging sonar, WLR-8V(2) ESM receiver, WLR-9 acoustic receiver for detection of active search sonar and acoustic homing torpedoes, BRD-7 radio direction finder, BPS-15 radar
Electronic warfare & decoys:	WLR-10 countermeasures set
Armament:	4× 21 in (533 mm) torpedo tubes, 37x Mk 48 torpedo, Tomahawk land attack missile, Harpoon anti–ship missile, Mk 67 mobile, or Mk 60 Captor mines (688i FLTII and FLTIII have a 12-tube VLS)

The Los Angeles class (also known as the 688-class) is a class of nuclear-powered fast attack submarines (SSN) in service with the United States Navy. They represent two generations and close to half a century of the U.S. Navy's attack submarine fleet. As of late 2015, 39 of the class are still in commission and 23 retired from service. Of the 23 retired boats, 14 of them were laid up half way (approximately 17–18 years) through their projected lifespans due to their midlife reactor refuelings being cancelled. A further four boats were proposed by the Navy, but later cancelled. The class has more operating nuclear submarines than any other in the world. All submarines of this class are named after American towns and cities (e.g. Key West, Florida, and Greeneville, Tennessee), the exception being the USS Hyman G. Rickover (SSN-709). This system of naming broke a long-standing tradition in the U.S. Navy of naming attack submarines for creatures of the ocean (e.g. USS Nautilus (SSN-571)).

In 1982 after building 31 boats, the class underwent a minor redesign, the following 8 that made up the second "flight" of subs had 12 new vertical launch tubes that could fire Tomahawk missiles. The last 23 saw a significant upgrade with the 688i improvement program. These boats are quieter, with more advanced electronics, sensors, and noise reduction technology. Externally they can be recognized quickly as their retractable diving planes were placed at their bows rather than on their sails.

Characteristics

The aft end of the control room for USS Jefferson City in June 2009

Capabilities

According to the U.S. Department of Defense, the top speed of the submarines of the Los Angeles class is over 25 knots (29 mph or 46 kph), although the actual maximum is classified. Some published estimates have placed their top speed at 30 to 33 knots. In his book Submarine: A Guided Tour Inside a Nuclear Warship, Tom Clancy estimated the top speed of Los Angeles-class submarines at about 37 knots.

The U.S. Navy gives the maximum operating depth of the Los Angeles class as 650 ft (200 m), while Patrick Tyler, in his book Running Critical, suggests a maximum operating depth of 950 ft (290 m). Although Tyler cites the 688-class design committee for this figure, the government has not commented on it. The maximum diving depth is 1,475 ft (450 m) according to Jane's Fighting Ships, 2004–2005 Edition, edited by Commodore Stephen Saunders of the Royal Navy.

Weapons

A portside bow view of the fore section of USS Santa Fe tied up at the pier in February 1994. The doors of the Mark 36 vertical launch system for the Tomahawk missiles are in the "open" position.

Los Angeles-class submarines carry about 25 torpedo tube-launched weapons, as well as Mark 67 and Mark 60 CAPTOR mines and were designed to launch Tomahawk cruise missiles, and Harpoon missiles horizontally (from the torpedo tubes). The last 31 boats of this class also have 12 dedicated vertical launching system (VLS) tubes for launching Tomahawks.

Control Systems

Over close to forty years the control suite of the class has changed dramatically. The class was originally equipped with the Mk 113 mod 10 Fire control system, also known as the Pargo display program. The Mk 113 runs on a UYK-7 computer.

The Mk 117 FCS, the first "all digital" fire control system replaced the Mk 113. The Mk 117 transferred the duties of the analog Mk 75 attack director to the UYK-7, and the digital Mk 81 weapon control consoles, removing the two analog conversions, and allowing "all digital" control of the digital mk 48 control. The first 688 sub to be built with the Mk 117 was SSN-700, USS Dallas.

The Mark 1 Combat Control System/All Digital Attack Center replaced the Mk 117 FCS which it was based on. The Mk 1 CCS was built by Lockheed Martin, and gave the class the ability to fire Tomahawk missiles. The CSS internal tracker model provides processing for both towed array and spherical array trackers. Trackers are signal followers which generate bearing, arrival angle and frequency reports based on information received by an acoustic sensor. It incorporated the Gyro Static Navigator into the system in replacement of the DMINS of the earlier 688 class.

The Mk 1 CCS was replaced by the Mk 2. The Mk 2 was built by Raytheon. Mk 2 provides Tomahawk Block III vertical launch capability as well as fleet-requested improvements to Mk 48 ADCAP torpedo and Towed Array Target Motion Analysis (TMA) operability. The Mk 2 CCS paired with the AN/BQQ-5E system is referred to as the "QE-2" system. the CCS MK2 Block 1 A/B system architecture extends the CCS MK2 tactical system with a network of Tactical Advanced Computers (TAC-3). These TAC-3s are configured to support the SFMPL, NTCS-A, LINK-11 and ATWCS subsystems.

Sensors

Sonar

AN/BQQ-5

AN/BQQ-5 sensor suite consists of the AN/BQS-13 spherical sonar array and AN/UYK-44 computer. The AN/BQQ-5 was developed from the AN/BQQ-2 sonar system. The BQS 11, 12, and 13 spherical arrays have 1,241 transducers. Also equipped are a 104 hydrophone hull array and two towed arrays: the TB-12 (later replaced by the TB-16) and TB-23 or TB-29, of which there are multiple variants. There are 5 versions of the AN/BQQ-5 system, sequentially identified by letters A-E.

The 688i (Improved) subclass was initially equipped with the AN/BSY-1 SUBACS submarine advanced combat system that used an AN/BQQ-5E sensor system with updated computers and interface equipment. Development of the AN/BSY-1 and its sister the AN/BSY-2 for the Seawolf class was widely reported as one of the most problematic programs for the Navy, its cost and schedule suffering many setbacks.

A series of conformal passive hydrophones are hard-mounted to each side of the hull, using the AN/BQR-24 internal processor. The system uses FLIT (frequency line integration tracking) which homes in on precise narrowband frequencies of sound and, using the Doppler principle, can accurately provide firing solutions against very quiet submarines. The AN/BQQ-5’s hull array doubled the performance of its predecessors.

AN/BQQ-10

The AN/BQQ-5 system was replaced by the AN/BQQ-10 system. Acoustic Rapid Commercial Off-The-Shelf Insertion (A-RCI), designated AN/BQQ-10, is a four-phase program for transforming existing submarine sonar systems (AN/BSY-1, AN/BQQ-5, and AN/BQQ-6) from legacy systems to a more capable and flexible COTS/Open System Architecture (OSA) and also provide the submarine force with a common sonar system. A single A-RCI Multi-Purpose Processor (MPP) has as much computing power as the entire Los Angeles (SSN-688/688I) submarine fleet combined and will allow the development and use of complex algorithms previously beyond the reach of legacy processors. The use of COTS/OSA technologies and systems will enable rapid periodic updates to both software and hardware. COTS-based processors will allow computer power growth at a rate commensurate with the commercial industry.

Engineering and auxiliary systems

Two watertight compartments are used in the Los Angeles-class submarines. The forward compartment contains crew living spaces, weapons-handling spaces, and control spaces not critical to recovering propulsion. The aft compartment contains the bulk of the submarine's engineering systems, power generation turbines, and water-making equipment. Some submarines in the class are capable of delivering SEALs through either the dry deck shelter system or the advanced SEAL delivery system (program canceled in 2006 and rendered unusable in 2009). A variety of atmospheric control devices are used to allow the vessel to remain submerged for long periods of time without ventilating, including an electrolytic oxygen generator, which produces oxygen for the crew and hydrogen as a byproduct. The hydrogen is pumped overboard but there is always a risk of fire or explosion from this process.

USS Greeneville with an attached ASDS

While on the surface or at snorkel depth, the submarine may use the submarine's auxiliary or emergency diesel generator for power or ventilation (e.g., following a fire). The diesel engine in a 688 class can be quickly started by compressed air during emergencies or to evacuate noxious (nonvolatile) gases from the boat, although 'ventilation' requires raising a snorkel mast. During nonemergency situations, design constraints call for operators to allow the engine to reach normal operating temperatures before it is capable of producing full power, a process that may take from 20 to 30 minutes. However, the diesel generator can be immediately loaded to 100% power output, despite design criteria cautions, at the discretion of the submarine commander on the recommendation of the submarine's engineer, if necessity dictates such actions to: (a) restore electrical power to the submarine, (b) prevent a reactor incident from occurring or escalating, or (c) to protect the lives of the crew or others as determined necessary by the commanding officer.

Normally, steam power is generated by the submarine's nuclear reactor delivering pressurized hot water to the steam generator, which generates steam to drive the steam-driven turbines and generators. While the emergency diesel generator is starting up, power can be provided from the submarine's battery through the ship service motor generators. Likewise, propulsion is normally delivered through the submarine's steam-driven main turbines that drive the submarine's propeller through a reduction gear system. The submarine has no main drive shaft, unlike conventional diesel electric submarines.

USS Key West submerged at periscope depth off the coast of Honolulu, Hawaii in July 2004

Propulsion

The ship is equipped with a light water reactor, model GE PWR S6G, generating 35,000 shp, developed and supplied by General Electric. The auxiliary prop motor by Magnatek supplies 242 kW. The life of the fuel cells is approximately ten years. Part of the improved 688 program included the improved Performance Machinery Program Phase I.

The S6G reactor plant was originally designed to use the D1G-2 core, similar to the D2G reactor used on the Bainbridge-class guided missile cruiser, which is rated at 148 MW. All Los Angeles-class submarines from USS Providence (SSN-719) on were built with a D2W core rated at 165 MW, as opposed to the 150 MW cores found on older boats. The D1G-2 cores are being replaced with D2W cores when the boats are refueled.

In popular culture

• Los Angeles-class submarines have been featured prominently in numerous Tom Clancy novels and film adaptations, most notably USS Dallas (SSN-700) in The Hunt for Red October. Other mentions include USS Chicago (SSN-721) in Red Storm Rising and USS Cheyenne (SSN-773) in SSN.
• The 2000 Australian television film On the Beach features a fictional 688i Los Angeles-class submarine, USS Charleston (SSN-704).
• In the 2009 film Terminator Salvation, Resistance Headquarters is located aboard a Los Angeles-class submarine, called USS Wilmington according to the novelization and several behind-the-scenes books.
• The Los Angeles-class submarine is the focus of many submarine-related video games, such as the simulators 1989 688 Attack Sub, Electronic Arts' 1997 688(I) Hunter/Killer, and the 2005 Dangerous Waters.
• Call of Duty: Modern Warfare 2 (2009) features USS Chicago (SSN-721) as the launching platform for TF 141's operations. Another Los Angeles-class submarine, USS Dallas (SSN-700), can also be seen in the level "The Only Easy Day... Was Yesterday".
• USS Alexandria (SSN-757) was used in filming Stargate: Continuum.
• A fictional Los Angeles class submarine named USS Orlando appeared in the 1996 comedy film Down Periscope.

See also

• List of Los Angeles-class submarines
• List of active Los Angeles-class submarines by homeport

References

• This article includes information collected from the Naval Vessel Register, which, as a U.S. government publication, is in the public domain.

External links

• Role of the Modern Submarine at Submarine History.