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The Los Angeles-class, sometimes called the LA-class or the 688-class, is a class of nuclear-powered fast attack submarines that forms the backbone of the U.S. Navy's submarine force, with 62 submarines of this class being completed. As of late 2013, 41 of the class are still in commission and 21 retired from service. Of the 21 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. One boat, USS Miami (SSN-755), was retired due to extensive fire damage caused by arson when she was a few months into a maintenance period. A further four boats were proposed by the Navy, but later cancelled.

The Los Angeles class contains more nuclear submarines than any other class in the world. The class was preceded by the Sturgeon-class submarine and followed by the Seawolf-class submarine. Except for USS Hyman G. Rickover (SSN-709), all submarines of this class are named after American cities and a few towns (e.g. Key West, Florida, and Greeneville, Tennessee). 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)).

The final 23 boats of the Los Angeles class were designed and built to be quieter than their predecessors and also to carry more-advanced sensor and weapons systems. Externally they can be recognized quickly as their retractable diving planes were placed at their bows rather than on their sails.

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, while Patrick Tyler, in his book Running Critical, suggests a maximum operating depth of 950 ft. Although Tyler cites the 688-class design committee for this figure, the government has not commented on it. The maximum diving depth is 1475 ft according to Jane's Fighting Ships, 2004–2005 Edition, edited by Commodore Stephen Saunders of the Royal Navy.

Weapons and fire control systems
 Los Angeles class submarines carry about 25 torpedo tube-launched weapons and all boats of the class are capable of launching Tomahawk cruise 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.

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 nicknamed "the bomb". It is called "the bomb" because it electrically removes the bonds of hydrogen and oxygen which make up water. This produces oxygen for the crew and hydrogen. The hydrogen is pumped overboard but there is always a risk of fire or explosion from this process. 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.



In popular culture

 * Los Angeles-class submarines have been featured prominently in numerous Tom Clancy novels and film adaptations, most notably the 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, the USS Charleston (SSN-704).
 * In the 2009 film Terminator Salvation, Resistance Headquarters is located aboard a Los Angeles-class submarine, called the 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 the USS Chicago (SSN-721) as the launching platform for TF 141's operations. Another Los Angeles -class submarine, the USS Dallas (SSN-700), can also be seen in the level "The Only Easy Day... Was Yesterday".
 * The USS Alexandria (SSN-757) was used in filming Stargate: Continuum.
 * A fictional Los Angeles-class submarine named the USS Orlando appeared in the 1996 comedy film Down Periscope.