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CVN-68 Nimitz-class - Design

Aircraft carriers are the largest combatant ships in the world. They are huge floating cities, carrying thousands of sailors and aircraft, each vessel with more military power than many nations. Frequently the adoption of a new aircraft by naval aviation required the installation a specific ship alteration, more commonly referred to as a SHIPALT, to allow it to operate aboard the existing carrier fleet. Developments such as nuclear power, angled decks, advanced steam catapults, fresnel lenses, water cooled jet blast deflectors, and automatic carrier landing systems, are but some of the changes that shaped the "super carrier" concept that culminated with the design and construction of NIMITZ (CVN 68).

The general arrangement of these ships is similar to the previous Kitty Hawk class with respect to flight deck, hangar, elevators, and island structure, e.g., the island is aft of the Number 1 and 2 elevators, with the Number 4 elevator on the port side aft of the angled deck and opposite the Number 3 elevator. The angled deck is canted to port at 93'. The general excellence of the Nimitz design precluded major changes to later ships in the class. CVN-71 and subsequent ships incorporate improved magazine protection; CVN-73 and later ships feature improved topside ballistic protection; CVN-74 and later ships are constructed with HSLA-100 steel.

The NIMITZ-class carriers are a floating airport, capable of launching as many as four aircraft a minute. The ship's four catapults and four arresting gear engines enable her to launch and recover aircraft rapidly and simultaneously. The ships carry seven different types of aircraft with a total complement of more than 80 planes. During flight operations, the flight deck of 4.5 acres is a scene of intense activity, with crew, aircraft and other equipment functioning as a well-rehearsed and carefully choreographed team to ensure both efficiency and safety.

Four aircraft elevators, each the size of two average city lots, bring the aircraft to the flight deck from the hangars below. Small tractors spot the planes on the flight deck. Aviation fuel is pumped up from tanks below, and bombs and rockets are brought up from the magazines. Powerful steam catapults (affectionately known as "Fat Cats") can accelerate 37-ton jets from zero to a safe flight speed of up to 180 miles per hour in about 300 feet and in less than three seconds. The weight of each aircraft determines the amount of thrust provided by the catapult.

Nimitz class aircraft carriers possess an inherent list to starboard that their list control systems (LCS) are typically unable to correct while under Combat Load Conditions. Any inherent list imposes operational constraints on the ship, particularly when the carrier has embarked a full air-wing and full fuel loading (CombatLoad Condition). As a result, it has become necessary to use fresh water ballast in a number of inner bottom voids and damage control voids to augment the LCS. Maintaining liquid ballast in damage control [DC] voids is unacceptable, as it reduces the design counter flooding capability of the ship, and thus reduces ship survivability.

From operational experience, it would be safe to say that there is an inherent starboard list under full fuel load (or virtually full) with the airwing embarked and no flight operations being conducted on most Nimitz class carriers. When all the planes are stacked on the starboard side and the ship has just been refueled, the LCS is unable to level the deck. This is when it has become necessary for some carriers to use fresh water ballast in a number of inner bottom voids and damage control (DC) voids to correct the adverse list condition. But from a ship survivability standpoint, and as their name implies, DC voids are not an acceptable list control measure under normal operating conditions.

When landing, pilots use a system of lenses to guide the aircraft "down the slope," the correct glide path for landing. The four arresting wires, each consisting of two-inch thick wire cables connected to hydraulic rams below decks, drag landing aircraft going as fast as 150 miles per hour to a stop in less than 400 feet. High in the island, seven stories above the flight deck, the "Air Boss" and his staff coordinate the entire operation, which is carefully monitored from the flight deck level as well as by the Captain on the ship's bridge. The various functions of the flight deck crew are identified by the colors 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.

The NIMITZ-class self-defense measures include: missiles, guns, and electronic warfare. The NATO Sea Sparrow Missile System is comprised of two launchers with eight missiles each. Sea Sparrow is a radar-guided, short-to-medium range missile capable of engaging aircraft and cruise missiles. NIMITZ-class also has Close-In Weapon System mounts for short range defense against aircraft or missiles. Each mount has its own search and track radar, and a six-barrel, 20-millimeter Gatling gun capable of firing 3,000 rounds per minute.

The carrier's two nuclear reactors give her virtually unlimited range and endurance and a top speed in excess of 30 knots. Eight steam turbine generators each produce 8,000 kilowatts of electrical power, enough to serve a small city. The ship has enough electrical generating power to supply electricity to a city of 100,000. The ships normally carrys enough food and supplies to operate for 90 days. Four distilling units enable NIMITZ-class engineers to make over 400,000 gallons of fresh water from seawater a day, for use by the propulsion plants, catapults and crew. The ship carries approximately 3 million gallons of fuel for her aircraft and escorts, and enough weapons and stores for extended operations without replenishment.

These ships have extensive repair capabilities, including a fully equipped Aircraft Intermediate Maintenance Department, a micro-miniature electronics repair shop, and numerous ship repair shops. Keeping a NIMITZ-class carrier ready at all times requires repair shops to maintain machinery and aircraft, heavy duty tailor shops to repair parachutes and other survival gear, and electronic ships that keep communication, navigation and avionics equipment in good condition. NIMITZ-class carriers boast all the amenities that would be found in any American city with a comparable population, including a post office with its own ZIP code, TV and radio stations, a newspaper, a fire department, a library, a hospital, a general store, two barbershops and much more.

Every ship is slightly different. The ships are so large and have such a high procurement cost that only one is built at a time. It takes an average of five years to build one carrier, and in that time, modernizations, upgrades, and improvements are introduced into the design. As such, the ships are constantly changing and evolving, all within the same skin designed in the late 1960's.

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Page last modified: 07-02-2016 19:42:03 ZULU