The multipurpose aircraft carriers of the Nimitz class are the largest warships ever built that are in service. The USS Nimitz (CVN 68) is the leading unit of these "supercarriers"; her keel was laid down in June 1968, her hull was launched in May 1972 and she entered service in May 1975. The USS Nimitz is a nuclear-powered vessel; her propulsion plant comprises two nuclear reactors General Electric A4W/AIG, cooled by pressurized water, linked to four steam turbines able to provide 260000 horsepower, enough to propel the ship at speeds over 30 knots (almost 60 kilometers/hour).

The true advantage of nuclear propulsion is the huge increment in operational range, for the resupply of atomic fuel is only required at very large time intervals. In fact, the first supply of uranium bars was enough to navigate during 13 years, during which the USS Nimitz would travel a distance between 1.5 and 1.9 millions of kilometers without requiring to refuel. Or said with other words, a single series of uranium bars could provide the same energy than 11 millions of oil barrels (1.22 millions of tonnes). But, unlike the vessel, the crew and the aircraft onboard need to be fed daily, so the aircraft carrier has space for provisions and aviation fuel to supply during 15 days only.

Based on the theory that the best defense of the aircraft carrier are her aircraft, the USS Nimitz was fitted with a very limited armament: three octuple launchers for surface-to-air missiles Sea Sparrow, for air defense in a radius of about 14.6 kilometers, and three Vulcan Phalanx CIWS mountings with a six-barrel 20-millimeter cannon each, for antimissile defense at very close range. Apart from the active armament, the aircraft carrier is fitted with diverse radars and a bow sonar, electronic war devices and launchers for chaff or flares, to detect and divert incoming missiles and torpedoes.

The airborne air defense is formed by twenty F-14 Tomcat which, with their air-to-air missiles AIM-7 or AIM-54, provide combat air patrols (CAP) in a radius of up to 570 kilometers around the aircraft carrier (since the F-14 was retired from US Navy service in 2006 the F-18 took its role). While the F-14 perform their mission, the turboprop aircraft E-2C Hawkeye, fitted with a long-range search radar (AEW), explore the sky and the sea surface to detect any relevant activity. In case of contact, they would guide the patrolling F-14 to control the matter.

The air wing on the USS Nimitz also comprises a part of antisubmarine aircraft (ASW), this is, ten S-3A Viking, as well as six helicopters SH-3 Sea King for antisubmarine defense at close range (since the S-3A was retired from US Navy service in 2009 and the Sea King in 2006 other aircraft took their role). Both aircraft types are fitted with sonar devices for submarine detection and are able to launch self-guided torpedoes to the chosen targets.

To perform offensive actions, the USS Nimitz would make exclusive use of her aircraft. The attack squadron is formed by 40 aircraft: twenty A-6E Intruder and twenty F/A-18 Hornet. These latter are very adaptable aircraft, which can be used against land or sea targets. By contrast, the Intruder is a naval bomber, able to fly in the most adverse atmospheric conditions, and which can launch twenty-eight 226.8-kilogram bombs against targets located in a radius of 1670 kilometers around the aircraft carrier and then return.

The model A-6 comprises also an electronic warfare version (EW), the EA-6B Prowler, suitable to cause tactical electronic interferences, and a tanker version, the KA-6D (since the A-6 was retired from US Navy service in 1997 other aircraft took its diverse roles). The air wing on the USS Nimitz includes six Prowler and four KA-6D.

The following photograph, taken in 1997, shows all of the aforementioned aircraft parked in the flight deck. In the image are visible a total of 46 aircraft: eight F-14 Tomcat with retracted wings, twenty-four F/A-18 Hornet, three E-2C Hawkeye, five S-3A Viking, three helicopters and three A-6E Intruder. Note also the Sea Sparrow and the Vulcan Phalanx installed astern.

USS Nimitz aircraft carrier in 1997
About half of the aircraft onboard can be allocated in the hangar beneath the flight deck, using for the transfer one of the four elevators; the rest of the aircraft has to remain in the flight deck. Elevators have their shape adapted to that of the aircraft onboard and, with an area over 300 square meters and a lift power of 58500 kilograms, they are able to harbor two units on each transfer.

F/A-18 in aircraft carrier elevator
The required speed for take off is provided by steam catapults which, literally, throw the aircraft into the air. To land onboard, the aircraft must be hooked in one of the four arresting wires distributed across the landing area, maneuver not easy for an F-14, which during landing still advances with a speed of about 250 kilometers/hour. On the flight deck the personnel wears different colors to differentiate their diverse roles.

F-14 in aircraft carrier take-off
As 2016 goes by, and with the aircraft carriers of the Gerald R. Ford class in the horizon, the ten components of the Nimitz class still conform the aircraft carrier fleet of the United States Navy, over fourty years after the commissioning of the USS Nimitz. A number of upgrades have been effectuated in the electronics, the armament and the aircraft since then, but these aircraft carriers are still the best ones in the world and they will be serving for many years coming.

USS Nimitz aircraft carrier in 2009
USS Nimitz aircraft carrier in 2012
USS Theodore Roosevelt aircraft carrier

The USS Nimitz in detail

The 3rd May 1975, the USS Nimitz entered service with the United States Navy, being the second aircraft carrier in the world fitted with nuclear propulsion. At the same time she was the largest warship in existance, surpassing the USS Enterprise, which was precisely the first aircraft carrier powered by nuclear energy. The construction cost of the USS Nimitz reached 1881 millions of dollars. The assembly of the diverse components, not counting the design nor the production time, occupied about 40 millions of hours/person.

With a complement of around 6000 persons, a library, a supermarket and her own radio and television stations, the USS Nimitz is truly a floating city, and one gifted with exceptional warlike power, integrated by an air wing of around 90 aircraft, among which are always present some of the most modern models in existance. Of the 6000 persons onboard about 60 percent belongs to the ship's crew and the rest to the air wing. Inside such a ship there are about 3400 rooms of every type (offices, salons, cabins, storages, etc...), all of them gifted with air conditioning. For the large population onboard, every day the kitchens prepare about 18000 meals and 2000 cubic meters of salt water are potabilized.

With an overal length of 332.8 meters and a maximum beam of 76.8 meters, the USS Nimitz has a standard displacement over 91000 tonnes and a flight deck with an area of about 18200 square meters. There is such a multitude of systems onboard the ship, and of such complexity, that if all the manuals required to operate them were stacked together, they would form a column over 170 meters tall. These systems require so much energy that the power plant has capacity to provide electric energy for a city of 100000 habitants. The network of electric cables of every type onboard would measure, if put in line each one of them, more than 1500 kilometers. And there are more than 30000 lightpoints and 2000 telephones onboard.

When the aircraft carrier is operating, the operations post is not the command bridge, located on the isle and therefore too exposed, but the Combat Information Center (CIC) located deep inside the hull. This room contains every electronic device required to fight against an "invisible" enemy located beyond the horizon, while being protected from the effects of nuclear, biological and chemical warfare (NBC). The electronic equipment onboard the USS Nimitz includes the air surveillance radar SPS-49 with a range of 457 kilometers and the three-dimensional radar SPS-48 with a range of 402 kilometers. She also has radars for surface surveillance and navigation, and for controlling the aircraft and the launching of surface-to-air missiles.

USS Nimitz aircraft carrier cutaway

1 - Mk 29 BPDMS missile launcher :: 2 - Protected aft position :: 3 - Rudder :: 4 - Propeller :: 5 - Crane :: 6 - Crew accommodation :: 7 - Control stores aft :: 8 - Crew tables :: 9 - Crane control center :: 10 - Engine room :: 11 - Storage control :: 12 - Crew :: 13 - Linking corridor :: 14 - Storage of diverse materials :: 15 - Engine room :: 16 - Generators room :: 17 - Elevators :: 18 - Pantry :: 19 - Aviation storage :: 20 - Access to propeller shafts :: 21 - Spare parts for aircraft :: 22 - Aviation personnel :: 23 - Aviation personnel tables :: 24 - Generators control :: 25 - Fuel for aircraft :: 26 - Boats :: 27 - Air surveillance radar SPS-49 :: 28 - Command bridge position lights :: 29 - Tacan :: 30 - Secondary surface exploration radar :: 31 - Air surveillance and missile tracking radar :: 32 - Surface exploration radar SPS-10 :: 33 - 3D air surveillance radar SPS-48 :: 34 - Main flight control :: 35 - Navigation bridge :: 36 - Ship command center :: 37 - Flight control center :: 38 - Breakdown and safety control center :: 39 - Aviation personnel :: 40 - Radar control center :: 41 - Nuclear propulsion equipment :: 42 - False bottom :: 43 - Crew accommodation :: 44 - Spare parts for machinery:: 45 - Engine room :: 46 - Hangar :: 47 - Sonar control center :: 48 - Air conditioning facilities :: 49 - Meeting rooms for breakdown and safety control group :: 50 - Pantry :: 51 - Spare parts and ammunition for aircraft :: 52 - Deck and reserves control :: 53 - Take-off control :: 54 - Firewall door :: 55 - Crew resting area :: 56 - Catapult engine room :: 57 - Workshops :: 58 - Rooms for breakdown control meetings and crew accommodation :: 59 - Spare parts for aircraft and reparations :: 60 - Ammunition depots :: 61 - Sonar device :: 62 - Catapult protection and recovery :: 63 - Liferafts :: 64 :: Radio antennas

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