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  • The Nimitz-class supercarriers are a class of ten nuclear-powered aircraft carriers in

  • service with the United States Navy. The lead ship of the class is named for World War II

  • United States Pacific Fleet commander Fleet Admiral Chester W. Nimitz, the U.S. Navy's

  • last fleet admiral. With an overall length of 1,092 ft and full-load displacements of

  • over 100,000 long tons, they have been the largest warships built and in service, although

  • they are being eclipsed by the upcoming Gerald R. Ford-class aircraft carriers. Instead of

  • the gas turbines or diesel-electric systems used for propulsion on many modern warships,

  • the carriers use two A4W pressurized water reactors which drive four propeller shafts

  • and can produce a maximum speed of over 30 knots and maximum power of around 260,000 shp.

  • As a result of the use of nuclear power, the ships are capable of operating for over 20

  • years without refueling and are predicted to have a service life of over 50 years. They

  • are categorized as nuclear-powered aircraft carriers and are numbered with consecutive

  • hull numbers between CVN-68 and CVN-77. All ten carriers were constructed by Newport

  • News Shipbuilding Company in Virginia. USS Nimitz, the lead ship of the class, was commissioned

  • on 3 May 1975, and USS George H.W. Bush, the tenth and last of the class, was commissioned

  • on 10 January 2009. Since the 1970s, Nimitz-class carriers have participated in many conflicts

  • and operations across the world, including Operation Eagle Claw in Iran, the Gulf War,

  • and more recently in Iraq and Afghanistan. The angled flight decks of the carriers use

  • a CATOBAR arrangement to operate aircraft, with steam catapults and arrestor wires for

  • launch and recovery. As well as speeding up flight deck operations, this allows for a

  • much wider variety of aircraft than with the STOVL arrangement used on smaller carriers.

  • An embarked carrier air wing consisting of up to around 90 aircraft is normally deployed

  • on board. After the retirement of the F-14 Tomcat, the air wings' strike fighters are

  • primarily F/A-18E and F/A-18F Super Hornets and F/A-18A+ and F/A-18C Hornets. In addition

  • to their aircraft, the vessels carry short-range defensive weaponry for anti-aircraft warfare

  • and missile defense.

  • Description The Nimitz-class carriers have an overall

  • length of 1,092 ft and a full-load displacement of about 100,000–104,000 long tons. They

  • have a beam at the waterline of 135 ft, and the maximum width of their flight decks is

  • 251 ft 10 in to 257 ftin. The ships' companies can number up to 3,200, not including

  • an air wing of 2,480. Design

  • The Nimitz-class aircraft carriers were ordered to supplement the aircraft carriers of the

  • Kitty Hawk class and Enterprise class, maintaining the strength and capability of the U.S. Navy

  • after the older carriers were decommissioned. The ships were designed to be improvements

  • on previous U.S. aircraft carriers, in particular the Enterprise and Forrestal-class supercarriers,

  • although the arrangement of the ships is relatively similar to that of the Kitty Hawk class. Among

  • other design improvements, the two reactors on Nimitz-class carriers take up less space

  • than the eight reactors used on Enterprise. Along with a more generally improved design,

  • this means that Nimitz-class carriers can carry 90% more aviation fuel and 50% more

  • ordnance when compared to the Forrestal class. The U.S. Navy has stated that the carriers

  • could withstand three times the damage sustained by the Essex class inflicted by Japanese air

  • attacks during World War II. The hangars on the ships are divided into three fire bays

  • by thick steel doors that are designed to restrict the spread of fire. This addition

  • has been present on U.S. aircraft carriers since World War II, after the fires caused

  • by Kamikaze attacks. The first ships were designed around the time

  • of the Vietnam War, and certain aspects of the design were influenced by operations there.

  • To a certain extent, the carrier operations in Vietnam demonstrated the need for increased

  • capabilities of aircraft carriers over their survivability, as they were used to send sorties

  • into the war and were therefore less subject to attack. As a result of this experience,

  • Nimitz carriers were designed with larger stores of aviation fuel and larger magazines

  • in relation to previous carriers, although this was partly as a result of increased space

  • available by the new design of the ships' propulsion systems.

  • A major purpose of the ships was initially to support the U.S. military during the Cold

  • War, and they were designed with capabilities for that role, including using nuclear power

  • instead of oil for greater endurance when deployed in blue water, and the ability to

  • make adjustments to the carriers' weapons systems on the basis of new intelligence and

  • technological developments. They were initially categorized only as attack carriers, but ships

  • have been constructed with anti-submarine capabilities since USS Carl Vinson. As a

  • result, the ships and their aircraft are now able to participate in a wide range of operations,

  • which can include sea and air blockades, mine laying, and missile strikes on land, air and

  • sea. Because of a design flaw, ships of this class

  • have inherent lists to starboard when under combat loads that exceed the capability of

  • their list control systems. The problem appears to be especially prevalent on some of the

  • more modern vessels. This problem has been previously rectified by using damage control

  • voids for ballast, but a solution using solid ballast which does not affect the ship's survivability

  • has been proposed. Construction

  • All ten Nimitz-class aircraft carriers were constructed between 1968 and 2006 at Newport

  • News Shipbuilding Company, in Newport News, Virginia, in the largest drydock in the western

  • hemisphere, dry dock 12, now 2,172 feet long after a recent expansion.

  • Since USS Theodore Roosevelt, the carriers were manufactured in modular construction.

  • This means that whole sections could be welded together with plumbing and electrical equipment

  • already fitted, improving efficiency. Using gantry cranes, the modules were lifted into

  • the dry dock and welded. In the case of the bow section, these can weigh over 1,500,000

  • pounds. This method was originally developed by Ingalls Shipbuilding and increases the

  • rate of work because much of the fitting out does not have to be carried out within the

  • confines of the already finished hull. The total cost of construction for each ship

  • was around $4.5 billion. Propulsion

  • All ships of the class are powered by two A4W nuclear reactors, kept in separate compartments.

  • They power four propeller shafts and can produce a maximum speed of over 30 knots and maximum

  • power of 260,000 bhp. The reactors produce heat through nuclear fission which heats water.

  • This is then passed through four turbines which are shared by the two reactors. The

  • turbines power the four bronze propellers, each with a diameter of 25 feet and a weight

  • of 66,000 pounds. Behind these are the two rudders which are 29 feet high and 22 feet

  • long, and each weigh 110,000 pounds. The Nimitz-class ships constructed since USS Ronald Reagan

  • also have bulbous bows in order to improve speed and fuel efficiency by reducing hydrodynamic

  • drag. As a result of the use of nuclear power, the ships are capable of operating continuously

  • for over 20 years without refueling and are predicted to have a service life of over 50

  • years. Armament and protection

  • In addition to the aircraft carried on board, the ships carry defensive equipment for use

  • against missiles and hostile aircraft. These consist of either three or four NATO RIM-7

  • Sea Sparrow missile launchers designed for defense against aircraft and anti-ship missiles

  • as well as either three or four 20 mm Phalanx CIWS missile defense cannon. USS Ronald Reagan

  • has none of these, having been built with the RIM-116 Rolling Airframe Missile system,

  • two of which have also been installed on USS Nimitz and USS George Washington. These will be

  • installed on the other ships as they return for Refueling Complex Overhaul. Since USS

  • Theodore Roosevelt, the carriers have been constructed with 2.5 in Kevlar armor over

  • vital spaces, and earlier ships have been retrofitted with it: Nimitz in 1983–1984,

  • Eisenhower from 1985–1987 and Vinson in 1989.

  • The other countermeasures the ships use are four Sippican SRBOC six-barrel MK36 decoy

  • launchers, which deploy infrared flares and chaff to disrupt the sensors of incoming missiles;

  • an SSTDS torpedo defense system; and an AN/SLQ-25 Nixie torpedo countermeasures system. The

  • carriers also use AN/SLQ-32(V) electronic warfare systems to detect and disrupt hostile

  • radar signals in addition to the electronic warfare capabilities of some of the aircraft

  • on board. The presence of nuclear weapons on board U.S.

  • aircraft carriers since the end of the Cold War has neither been confirmed nor denied

  • by the U.S. government. As a result of this, as well as concerns over the safety of nuclear

  • power, the presence of a U.S. aircraft carrier in a foreign port has occasionally provoked

  • protest from local people, for example when USS Nimitz docked in Chennai, India, in 2007.

  • At that time, the Strike Group commander Rear Admiral John Terence Blake stated that: "The

  • U.S. policy is that we do not routinely deploy nuclear weapons on board Nimitz."

  • Carrier air wing

  • In order for a carrier to deploy, it must embark one of ten Carrier Air Wings. The carriers

  • can accommodate a maximum of 130 F/A-18 Hornets or 85–90 aircraft of different types, but

  • current numbers are typically 64 aircraft. Although the air wings are integrated with

  • the operation of the carriers they are deployed to, they are nevertheless regarded as a separate

  • entity. As well as the aircrew, the air wings are also made up of support personnel involved

  • in roles including maintenance, aircraft and ordnance handling and emergency procedures.

  • Each person on the flight deck wears color-coded clothing to make their role easily identifiable.

  • A typical carrier air wing can include 12–14 F/A-18E or F Super Hornets as strike fighters;

  • two squadrons of 10–12 F/A-18C Hornets, with one of these often provided by the U.S.

  • Marine Corps, also as strike fighters; 4–6 EA-6B Prowlers for electronic warfare; 4–6

  • E-2C Hawkeyes used for airborne early warning; C-2 Greyhounds used for logistics; and a Helicopter

  • Antisubmarine Squadron of 6–8 SH-60F & HH-60H Seahawks. Aircraft that have previously operated

  • from Nimitz-class carriers include F-4 Phantoms, RA-5C Vigilantes, RF-8G Crusaders, F-14 Tomcats,

  • S-3 Vikings, A-7 Corsair II and A-6E Intruder aircraft.

  • Flight deck and aircraft facilities

  • The flight deck is angled at nine degrees, which allows for aircraft to be launched and

  • recovered simultaneously. This angle of the flight deck was reduced slightly in relation

  • to previous carriers, as the current design improves the air flow around the carrier.

  • Four steam catapults are used to launch fixed-wing aircraft, and four arrestor wires are used

  • for recovery. The two newest carriers, Ronald Reagan and George H.W. Bush, only have three

  • arrestor wires each, as the fourth was used infrequently on earlier ships and was therefore

  • deemed unnecessary. This CATOBAR arrangement allows for faster launching and recovery as

  • well as a much wider range of aircraft that can be used on board compared with smaller

  • aircraft carriers, most of which use a simpler STOVL arrangement without catapults or arrestor

  • wires. The ship's aircraft operations are controlled by the air boss from Primary Flight

  • Control or Pri-Fly. Four large elevators transport aircraft between the flight deck and the hangars

  • below. These hangars are divided into three bays by thick steel doors that are designed

  • to restrict the spread of fire. Strike groups

  • When an aircraft carrier deploys, it takes a Strike Group, made up of several other warships

  • and supply vessels which allow the operation to be carried out. The armament of the Nimitz

  • class is made up only of short range defensive weapons, used as a last line of defense against

  • enemy missiles and aircraft. The other vessels in the Strike Group provide additional capabilities,

  • such as long range Tomahawk missiles or the Aegis Combat System, and also protect the

  • carrier from attack. A typical Strike Group may include, in addition to an aircraft carrier:

  • up to six surface combatants, including frigates, guided missile cruisers and guided missile

  • destroyers; one or two attack submarines; and an ammunition, oiler, and supply ship

  • of Military Sealift Command to provide logistical support. The precise structure and numbers

  • of each type of ship can vary between groups depending on the objectives of the deployment.

  • Design differences within the class While the designs of the final seven ships

  • are slightly different from those of the earlier ships, the U.S. Navy considers all ten carriers

  • as a single class. When the older carriers come in for Refueling and Complex Overhaul,

  • their nuclear power plants are refueled and they are upgraded to the standards of the

  • later carriers. Other modifications may be performed to update the ships' equipment.

  • The ships were initially classified only as attack carriers but have been constructed

  • with anti-submarine capabilities since USS Carl Vinson. These improvements include better

  • radar systems and facilities which enable the ships to operate aircraft in a more effective

  • anti-submarine role, including the fitting of common undersea picture technology which

  • uses sonar to allow for better assessment of the threat from submarines. The changes

  • included better support for S-3 Viking ASW patrol planes and SH-60F Seahawk helicopters

  • with dipping sonar systems.