The ten Nimitz class carriers are the largest warships in the world by displacement and are identified by consecutive hull numbers starting with CVN 68 where the letters CV denote the type of ship (aircraft carrier), N denotes nuclear powered propulsion and the number, e.g. 69, means that it is the 69th aircraft carrier commissioned by the US Navy.
The Nimitz class carriers normally operate as the centrepiece of a Carrier Strike Group (CSG), under the command of a flag officer embarked on the carrier, comprising the carrier itself and four to six other ships including guided missile cruisers, destroyers, frigates, submarines and replenishment ships. Forward deployment of these Carrier Strike Groups is a visible demonstration of America's global ability to project power providing deterrence and the ability to respond rapidly in the event of a crisis.
These 100,000+ ton ships, with an airwing of approximately 72 aircraft operating from a 4.5 acre flight deck, are floating airports able to launch as many as four aircraft per minute to protect the battle group or other friendly shipping; conduct attacks against enemy aircraft, surface ships, submarines and land targets; provide air support to land forces; or implement a sea / air blockade. They can both launch and recover aircraft simultaneously.
Each ship is equipped with four steam catapults, which can accelerate a 37 ton jet from zero to 180 mph in less than 3 seconds over a distance of 300 feet, and four arresting wires each connected to individual arresting gear engines, which can drag landing aircraft traveling at up to 150 mph to a stop in less than 400 feet. They have four deck edge elevators to transfer aircraft between the flight deck and hangar spaces below and use small tractors to move the aircraft around and position "spot" them on the flight deck.
During flight operations the flight deck is an intense scene of carefully choreographed and highly rehearsed activity coordinated by the "Air Boss" and his staff from high in the "island" superstructure. The various functions of the flight deck crew are identified by the colours they wear - yellow for officers and aircraft directors; purple for fuel handlers; green for catapult and arresting gear crews; blue for tractor drivers; brown for chock and chain runners; and red for crash and salvage teams and the ordnance handlers.
Each ship carries enough weapons and stores for extended periods of operations of up to 90 days without replenishment including approximately 3 million gallons of fuel for their aircraft and escorts. They also have extensive repair capabilities including fully equipped aircraft maintenance workshops, electronics repair workshops, ship repair workshops, and specialist tailor shops to repair and maintain parachutes and other survival equipment.
The Nimitz class carrier's two nuclear reactors provide virtually unlimited range and endurance with a top speed in excess of 30 knots. The eight steam turbine generators each produce 8,000 kilowatts of electrical power, enough to supply a city of 100,000, and the four distilling units produce over 400,000 gallons of fresh water per day for use by the propulsion plants, catapults and crew. The ships boast all the amenities that would be found in any American city with a comparable population including a general store, two barbershops, a newspaper, TV and radio stations, a library, a fire department, a hospital, and a post office with its own ZIP code.
All of the Nimitz class carriers have been built by Northrup Grumman Newports News and are generally estimated to have useful operating lives of 50 years. While construction differences between the first three ships (Nimitz, Eisenhower and Vinson) and the latter seven (from Theodore Roosevelt on), sometimes lead the latter ships to be called Theodore Roosevelt class carriers the US Navy considers them to all be in one class and as the earlier ships undergo their scheduled 33 month "mid-life" Refueling & Complex Overhaul (RCOH), starting with USS Nimitz in 1998, they are being upgraded to the standards of the later ships. The planned RCOH schedule means that for the next thirty years, with the exception of a four year window, there will always be one Nimitz class carrier in a shipyard undergoing refueling and overhaul.
The lead ship of the class, USS Nimitz (CVN 68), was commissioned in 1975 while the tenth and last of the class, USS George H W Bush (CVN-77), was commissioned on 10 January 2009. The last two ships, USS Ronald Reagan (CVN 76) and USS George H W Bush (CVN 77), are "transition" ships, incorporating new technologies and designs to improve efficiency and reduce crew requirements, on the road to the next generation CVNX / CVN 21 designated as the Ford Class.