Nimitz-class aircraft carrier
The Nimitz class is a class of ten nuclear-powered aircraft carriers in service with the United States Navy. The lead ship of the class is named after World War II United States Pacific Fleet commander Fleet Admiral Chester W. Nimitz, who was the last living U.S. Navy officer to hold the rank. With an overall length of and a full-load displacement of over, the Nimitz-class ships were the largest warships built and in service until entered the fleet in 2017.
Instead of the gas turbines or diesel–electric systems used for propulsion on many modern warships, the carriers use two A4W nuclear pressurized water reactors. The reactors produce steam to drive steam turbines which drive four propeller shafts and can produce a maximum speed of over and a maximum power of around. As a result 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 from CVN-68 to CVN-77.
All ten carriers were constructed by Newport News Shipbuilding Company in Virginia., the lead ship of the class, was commissioned on 3 May 1975, and, 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 comprising around 64 aircraft is normally deployed on board. The air wings' strike fighters are primarily F/A-18E and F/A-18F Super Hornets. In addition to their aircraft, the vessels carry short-range defensive weaponry for anti-aircraft warfare and missile defense.
The unit cost was about US$8.5 billion in FY 2012 dollars, equal to US$ billion in.
Description
The Nimitz-class aircraft carriers have a length of overall and at the waterline, with a beam of overall and at the waterline; the individual ships have slight variations in their dimensions. They were initially designed with a full-load displacement of and a draft of, but the ships would be delivered several thousand tons heavier, particularly for later members of the class. As the vessels were overhauled and installed more equipment, loaded displacement would climb to exceed. For example, currently displaces at full load. The ships' nominal complement comprises: 3,000–3,200; 1,500 ; and 500.Design
The Nimitz-class aircraft carriers were ordered to supplement the aircraft carriers of the,, and es, 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, particularly the Enterprise and supercarriers, although the arrangement of the vessels 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, 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 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; they were used to send sorties into the war and were, therefore, less subject to attack. As a result of this experience, Nimitz-class carriers were designed with larger stores of aviation fuel and larger magazines compared to previous carriers, although this was partly a result of increased space available by the new design of the ships' propulsion systems.
A major purpose of the carriers was initially to support the U.S. military during the Cold War. They were designed with capabilities for that role, including using nuclear power instead of oil for greater endurance and the ability to adjust their 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. As a result, the ships and their aircraft can participate in a wide range of operations, including 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 that does not affect the ship's survivability has been proposed.
Construction
All ten Nimitz-class carriers were constructed between 1968 and 2006 at Newport News Shipbuilding in Newport News, Virginia. The first three units of the class were erected in Dry Dock 11, the other seven ships were constructed in the largest dry dock in the western hemisphere, Dry Dock 12, now long after a recent expansion.Beginning with, the aircraft carriers were manufactured with modular construction. This means that whole sections could be welded together with plumbing and electrical equipment already fitted, improving efficiency. The modules were lifted into the dry dock using gantry cranes and welded. In the case of the bow sections, these can weigh over. 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, housed in separate compartments. The reactors produce heat through nuclear fission, which heats water to produce steam. This is then passed through four turbines, which are shared by the two reactors. A gearbox transmits power to four propeller shafts, producing a maximum speed of over and maximum power of. The turbines power the four bronze propellers, each with a diameter of and a weight of. Behind these are the two rudders, which are high and long, and each weighs.The Nimitz-class ships constructed since also have bulbous bows to improve speed and fuel efficiency by reducing wave-making resistance. As a result 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 two or three RIM-7 Sea Sparrow or RIM-162 Evolved SeaSparrow Missile Mk 29 missile launchers designed for defense against aircraft and anti-ship missiles, as well as either three or four 20 mm Phalanx CIWS.USS Ronald Reagan has none of these, having been built with the Mk 49 Guided Missile Launching Systems for RIM-116 Rolling Airframe Missiles, two of which have also been installed on and. 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 Kevlar armor over vital spaces, and earlier ships have been retrofitted with it: Nimitz in 1983–1984, Dwight D. Eisenhower from 1985 to 1987 and Carl Vinson in 1989.
The ships' other countermeasures are four Sippican SRBOC six-barrel Mk 36 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 jamming 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, the presence of a U.S. aircraft carrier in a foreign port has occasionally provoked protest from local people, for example, when Nimitz visited Chennai, India, in 2007. At that time, the Strike Group commander Rear Admiral John Terence Blake stated, "The U.S. policy is that we do not routinely deploy nuclear weapons on board Nimitz."
In May 2013, George H. W. Bush conducted the first carrier-borne end-to-end at-sea test of the Surface Ship Torpedo Defense System. The SSTDS combined the passive detection of the Torpedo Warning System that finds, classifies, and tracks torpedoes with the hard-kill capability of a Countermeasure Anti-Torpedo, an encapsulated miniature torpedo designed to locate, home in on, and destroy hostile torpedoes. This was to increase protection against wake-homing torpedoes like the Type 53 that do not respond to acoustic decoys. The pieces of the SSTDS were engineered to locate and destroy incoming torpedoes in a matter of seconds; each system included one TWS and 8 CATs. Initial operational capability was planned for 2019, and all aircraft carriers were to be outfitted by 2035. The Navy suspended work on the project in September 2018 due to poor reliability of the components; hardware, already installed on five carriers, is to be removed by 2023.