Nuclear-Powered Aircraft Carriers

This first nuclear-powered carrier for the US navy was commissioned in November 1961 as the USS Enterprise (CVAN-65), with the letter ‘N’ within the letter suffix designation code representing the fact that it was nuclear-powered. It was originally envisioned that the USS Enterprise would be the lead in a class of six ships.

The idea for a nuclear-powered carrier had been under consideration by the US navy since early 1949. By 1952 Secretary of the Navy Dan A. Kimball said that he hoped the next carrier would be nuclear-powered. The Atomic Energy Commission and the Department of Defense (DOD) jointly announced in 1954 plans ‘for the development of nuclear propulsion for large naval vessels’.

With nuclear-powered carriers, onboard reactors heat pressurized water and turn it into high-pressure steam. This high-pressure steam is then employed to power a ship’s main propulsion turbine engines, which are mechanical, turbine generators, and auxiliary machinery. It also provides the steam required by the ship’s catapults.

Unlike conventionally-powered carriers that must refuel every few thousand miles, nuclear-powered carriers have the ability to steam at high speed for up to a million miles. However, like conventionally-powered carriers, nuclear-powered carriers must still be replenished constantly with aviation fuel and ordnance for their aircraft plus food and other supplies for their crews.

As nuclear reactors produce a great deal of radiation, the areas of a ship in which they are located must be heavily shielded to protect the engineering crew. The level of training required among the engineering crew of nuclear-powered carriers is much higher than that of their conventionally-powered counterparts. Since nuclear reactors do not produce the exhaust gases of ships powered by fuel oil-fired boilers, nuclear-powered ships do not require stacks, which does free up a certain amount of room on a carrier’s island.

The First Nuclear-Powered US Navy Carrier

In 1956 Congress authorized the construction of the first nuclear-powered carrier. On 4 February 1958, at the same time the keel of the new ship was being laid down, Secretary of the Navy William B. Franke announced that it would be assigned the proud name Enterprise to perpetuate the famous Second World War Yorktown-class carrier USS Enterprise (CV-6) and its five naval predecessors.

This first nuclear-powered carrier for the US navy was commissioned in November 1961 as the USS Enterprise (CVAN-65), with the letter ‘N’ within the letter suffix designation code representing the fact that it was nuclear-powered. It was originally envisioned that the USS Enterprise would be the lead in a class of six ships.

The first commander of the USS Enterprise was Captain (later Vice Admiral) Vincent de Poix. In early 1962 he described some of the abilities of his new ship:

There are four rudders, one almost directly astern of each propeller. This provides excellent maneuverability at all speeds as well as tactical diameters in turns which compares with much smaller ships …

Her ability to launch a strike on the enemy from one position, recover, and launch another 24 hours later from an unpredictable position more than 800 miles away from her previous strike position will constantly be a factor in causing the enemy to utilize protective forces that could be deployed elsewhere.

If a show of force is required, Enterprise can be on distant station in a shorter period of time than any other ship in the fleet.

Ship Description

At the time it was built, the USS Enterprise was the largest ship ever constructed with a length of 1,123 feet and a full load displacement of 89,600 tons. The general shape and dimensions of the ship were based on the design of the Kitty Hawk-class carriers. The Enterprise typically carried 100 planes.

Like the previous Kitty Hawk class, the USS Enterprise had four steam-powered catapults and four deck-edge elevators. Its most distinctive external feature was the box-like design of the upper portion of its island, which had large flat-panel phased-array antennas mounted instead of the more conventional rotating radar antennas. The original radar design arrangement on the Enterprise was eventually removed and replaced by more conventional rotating radars.

During its many decades of service, the USS Enterprise went through a number of modernization programmes. In 1975 the US navy redesignated the letter suffix code for the ship from CVAN to CVN, when it received its own inventory of ASW aircraft.

Due to the cost of building the Enterprise, the US navy decided not to build any additional examples of the ship. It was inactivated in December 2012 because of the high cost of refuelling the eight nuclear reactors on board the ship. However, it will not be formally decommissioned until it is completely defuelled, which will take until 2015 or longer.

A comparison of Capital warships of the Twentieth Century.

Nimitz-Class Carriers

Despite some early problems with the USS Enterprise, mainly centred on its phased-array radar system, the Secretary of Defense and Congress were generally very pleased with its operational performance. This resulted in Congress authorizing the construction of a new, more affordable class of nuclear-powered carriers, designated the Nimitz class. They would be based around the design of the Kitty Hawk-class carriers, which in turn had been based on the cancelled USS United States (CVA-58).

The first ship in the Nimitz class was the USS Nimitz (CVAN-68) that was laid down in June 1968 but not commissioned until May 1975. This long gestation period pushed back the planned commissioning date of the follow-on Nimitz-class carriers, resulting in a dramatic increase in their cost. President Jimmy Carter responded to this additional expense by boldly suggesting that the US navy cancel the Nimitz class and build a class of smaller and more affordable carriers. As might be expected, the majority of the US navy’s senior leadership reacted very badly to the president’s view on what was best for the service and with its Congressional supporters overcame his objections. Congress would go on to authorize funding for the construction of additional Nimitz-class carriers.

Some within the US navy and the preceding President Gerald Ford administration had also believed that smaller non-nuclear-powered carriers might be a solution to the high cost of nuclear-powered vessels and had done various studies on the matter beginning in the 1970s. However, none ever came to fruition. These proposed smaller, non-nuclear-powered carriers went by different names: Sea Control Ship (SCS), mid-size carrier (CVV) and the VSTOL Support Ship (VSS), the acronym ‘VSTOL’ standing for Vertical/Short Take-Off and Landing.

Additional Nimitz-Class Carriers Authorized

The USS Nimitz was followed by the USS Dwight D. Eisenhower (CVAN-69). In June 1975 both ships were reclassified with the letter suffix designation code CVN as they had their own dedicated ASW aircraft, making them multi-mission carriers.

The following eight Nimitz-class carriers were assigned the letter suffix designation code CVN from their commissioning date: USS Carl Vinson (CVN-70), USS Theodore Roosevelt (CVN-71), USS Abraham Lincoln (CVN-72), USS George Washington (CVN-73), USS John C. Stennis (CVN-74), USS Harry S. Truman (CVN-75), USS Ronald Reagan (CVN-76) and USS George H.W. Bush (CVN-77). The last was commissioned in January 2009, thirty-four years after the first in its class. All ten Nimitz-class carriers continue in service to this day and remain the tip of the spear in America’s military projection around the globe.

Class Description

Nimitz-class carriers are twenty-four storeys high and require more than 900 miles of cable and wiring, 60,000 tons of structural steel and almost a million pounds of aluminium. The four bronze propellers that push them through the seas are 21 feet across and weigh 66,220 pounds each. There are nearly 30,000 light fixtures and 2,000 phones aboard a Nimitz-class carrier. A distillation plant produces 400,000 gallons of fresh water daily for each ship and its crew. That is enough for 2,000 suburban homes every day. The kitchens on board the ships prepare 18,150 meals per day.

The Nimitz-class carriers have an overall length of 1,094 feet with a full load displacement of almost 100,000 tons in the last units constructed. They can carry up to ninety planes in an emergency, with a typical number today being around fifty-six planes.

As with the previous Kitty Hawk class, the Nimitz-class carriers have four steam-powered catapults and four deck-edge elevators. Unlike the USS Enterprise (CVAN-65) that had eight A2W nuclear reactors, the Nimitz-class ships have only two of the latest-generation A4W nuclear reactors, the extra space being employed for many other purposes such as storage of aviation fuel and ordnance.

The Merits of Nuclear-Powered Carriers

The US navy preference for nuclear-powered carriers over their conventionally-powered equivalents was addressed in an August 1998 Government Accounting Office (GAO) report entitled ‘U.S. Navy Aircraft Carriers: Cost Effectiveness of Conventionally and Nuclear-Powered Carriers’. The following extract partly summarizes the GAO’s conclusions:

Each type of carrier offers certain advantages. For example, conventionally powered carriers spend less time in maintenance, and as a result, they can provide more forward presence coverage. By the same token, nuclear carriers can store larger quantities of aviation fuel and munitions and, as a result, are less dependent on at-sea replenishment. There was little difference in the operational effectiveness of nuclear and conventional carriers in the Persian Gulf War …

Pictured still in dry dock during its launching ceremony is the unfinished USS Gerald R. Ford (CVN-78). It is the first ship in the brand-new Gerald R. Ford class of supercarriers. It has a new bulbous lower bow section seen here that improves hull efficiency by adding buoyancy to the forward end of the ship. Total cost of the ship when completed is expected to be $14 billion. She was commissioned in 2017.

The second ship in the new Ford class of carriers will be the USS John F. Kennedy (CVN-79), seen here in model form. Construction of the vessel began in February 2011 and it is expected to be completed by 2020. The island on the Ford class of supercarriers will have only a single large foremast projecting out of the roof rather than the two separate masts seen on Nimitz-class carriers

Nimitz-Class Replacement Carrier

With the extremely long lead-in time between the authorization of a modern carrier and its commissioning, the US navy began thinking about the replacement for the Nimitz-class carriers as far back as the early 1990s. The first ship in this new proposed class of carriers would be a prototype referred to as the CVX.

In 1998 a US navy spokesman stated that the CVX prototype would be designed with a ‘clean sheet of paper’, suggesting that it would not be an evolutionary improvement over the previous Nimitz-class carriers but a revolutionary improvement with a dramatic rise in operational capabilities. Also implied was the fact that the CVX might not be nuclear-powered and would be more affordable and less costly to operate than the preceding Nimitz class.

Despite the 1998 pronouncement by the US navy on what they visualized for the CVX prototype, the funding necessary for the implementation of the revolutionary ship never materialized. Instead, in 2001 the new Secretary of Defense, Donald Rumsfeld, proposed that a prototype carrier be built as an evolutionary improvement over the previous Nimitz-class carriers and be labelled as CVX-1. It would be followed into production by the building of a more revolutionary improved Nimitz-class carrier designated the CVX-2.

The US navy then decided to merge the concept of the CVX-1 and CVX-2 into a single ship initially referred to as the CVN-21, with the numbers in the designation code representing the twenty-first century. Building of the new carrier, named the Gerald R. Ford and given the designation code CVN-78, began in 2007 with a commissioning date of 2017. As indicated by the ship’s letter suffix designation code, the Gerald R. Ford is nuclear-powered.

The intended replacement for the ‘legacy’ McDonnell Douglas F/A-18 Hornet, and to complement the Boeing F/A-18 Super Hornet on the Nimitz and Ford class of carriers, is the Lockheed Martin F-35C multi-mission aircraft seen here. The single-engine, single-seat F-35C is a variant of the standard F-35, originally known as the Joint Strike Fighter (JSF), and has stealth features. It first entered service with the US navy in 2013 and may represent the last generation of manned carrier aircraft employed by the service.

On the horizon for use on the Nimitz and Ford class of carriers are unmanned combat aerial vehicles, the possible future of carrier aviation. Pictured on the flight deck of a Nimitz-class carrier is a tailless Northrop Grumman demonstration drone, designated the X-47B. It was successfully launched and recovered from Nimitz-class supercarriers in 2013. It has a wing span of 62 feet and two weapon bays, plus stealth features.

Carrier Description

The PCU (Pre-Commissioning Unit) Gerald R. Ford is 1,106 feet long and when commissioned it is estimated that it will have a full load displacement of over 100,000 tons. It will carry approximately seventy-five aircraft that will be launched by four catapults. Aircraft will be moved between the flight deck and hangar deck by three deck-edge elevators instead of the four on the previous Nimitz-class carriers.

The island on the Gerald R. Ford is smaller and located further aft than seen on the previous Nimitz-class carriers. To increase the number of missions (sorties) that the ship’s aircraft can perform and at the same time reduce the number of personnel needed, a great deal of automation was incorporated into the carrier’s final design.

From the Naval Sea System Command comes this passage describing the reasons why the new Ford class of carriers will be more cost-effective than the previous Nimitz class:

Each ship in the new class will save more than $4 billion in total ownership costs during its 50-year service life, compared to the Nimitz-class. The CVN 78 is designed to operate effectively with nearly 700 fewer crew members than a CVN 68-class ship. Improvements in the ship design will allow the embarked air wing to operate with approximately 400 fewer personnel. New technologies and ship design features are expected to reduce watch standing and maintenance workload for the crew … The Gerald R. Ford class is designed to maximize the striking power of the embarked carrier air wing. The ship’s systems and configuration are optimized to maximize the sortie generation rate (SGR) of attached strike aircraft, resulting in a 33 per cent increase in SGR over the Nimitz class. The ship’s configuration and electrical generating plant are designed to accommodate new systems, including direct energy weapons, during its 50-year service life.

The Gerald R. Ford will be fitted with an Electromagnetic Aircraft Launch System (EMALS) when commissioned, in place of the steam-powered catapults currently employed on the Nimitz-class carriers. The advantages provided by installing the EMALS on the Gerald R. Ford, according to the US navy, are numerous. These include a reduction in size and weight, plus requiring less maintenance and therefore fewer personnel to operate. According to the programme manager for the EMALS, it will be able:

to launch today’s current air wing as well as all future carrier aircraft platforms in the U.S. Navy’s inventory through 2030 with reduced wind-over-the-deck requirements when compared to steam catapults, and additional capability for aircraft growth during the 50-year life of a carrier.

To supplement the EMALS on the Gerald R. Ford it will also be fitted with the new Advanced Arresting Gear (AAG). This employs an electric motor-based system in place of the existing hydraulic arresting gear system. It has been stated by the US navy that the AAG will be much more reliable than the existing arresting gear system. It is planned to eventually upgrade the Nimitz-class carriers with the AAG.

The last two Nimitz-class carriers, the USS Ronald Reagan and USS George H.W. Bush were fitted with a new Advanced Recovery Control (ARC) system which is digitally controlled. This was in contrast to the previous Mk. 7 mechanically-controlled arresting gear system fitted to the first eight Nimitz-class carriers commissioned.

Two other carriers in what is now referred to as the Gerald R. Ford or Ford class have also been authorized: the John F. Kennedy (CVN-79) and the Enterprise (CVN-80). Construction on the John F. Kennedy began in 2011, with construction of the Enterprise scheduled to begin in 2018. Current plans call for eventually building seven more Ford-class carriers to replace the ten existing Nimitz-class carriers on a one-for-one basis. It is anticipated that the last Nimitz-class carrier will be decommissioned in 2058.

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