The Nimitz-class supercarriers are a class of ten nuclear-powered aircraft carriers in
service with the United States Navy. The lead ship of the class is named for World War II
United States Pacific Fleet commander Fleet Admiral Chester W. Nimitz, the U.S. Navy's
last fleet admiral. With an overall length of 1,092 ft and full-load displacements of
over 100,000 long tons, they have been the largest warships built and in service, although
they are being eclipsed by the upcoming Gerald R. Ford-class aircraft carriers. Instead of
the gas turbines or diesel-electric systems used for propulsion on many modern warships,
the carriers use two A4W pressurized water reactors which drive four propeller shafts
and can produce a maximum speed of over 30 knots and maximum power of around 260,000 shp.
As a result of the use 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 between CVN-68 and CVN-77. All ten carriers were constructed by Newport
News Shipbuilding Company in Virginia. USS Nimitz, the lead ship of the class, was commissioned
on 3 May 1975, and USS George H.W. Bush, 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 consisting of up to around 90 aircraft is normally deployed
on board. After the retirement of the F-14 Tomcat, the air wings' strike fighters are
primarily F/A-18E and F/A-18F Super Hornets and F/A-18A+ and F/A-18C Hornets. In addition
to their aircraft, the vessels carry short-range defensive weaponry for anti-aircraft warfare
and missile defense.
Description The Nimitz-class carriers have an overall
length of 1,092 ft and a full-load displacement of about 100,000–104,000 long tons. They
have a beam at the waterline of 135 ft, and the maximum width of their flight decks is
251 ft 10 in to 257 ft 3 in. The ships' companies can number up to 3,200, not including
an air wing of 2,480. Design
The Nimitz-class aircraft carriers were ordered to supplement the aircraft carriers of the
Kitty Hawk class and Enterprise class, 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, in particular the Enterprise and Forrestal-class supercarriers,
although the arrangement of the ships 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,
this means that 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 Essex class 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, as they were used to send sorties
into the war and were therefore less subject to attack. As a result of this experience,
Nimitz carriers were designed with larger stores of aviation fuel and larger magazines
in relation to previous carriers, although this was partly as a result of increased space
available by the new design of the ships' propulsion systems.
A major purpose of the ships was initially to support the U.S. military during the Cold
War, and they were designed with capabilities for that role, including using nuclear power
instead of oil for greater endurance when deployed in blue water, and the ability to
make adjustments to the carriers' 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 USS Carl Vinson. As a
result, the ships and their aircraft are now able to participate in a wide range of operations,
which can include 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 which does not affect the ship's survivability
has been proposed. Construction
All ten Nimitz-class aircraft carriers were constructed between 1968 and 2006 at Newport
News Shipbuilding Company, in Newport News, Virginia, in the largest drydock in the western
hemisphere, dry dock 12, now 2,172 feet long after a recent expansion.
Since USS Theodore Roosevelt, the carriers were manufactured in modular construction.
This means that whole sections could be welded together with plumbing and electrical equipment
already fitted, improving efficiency. Using gantry cranes, the modules were lifted into
the dry dock and welded. In the case of the bow section, these can weigh over 1,500,000
pounds. 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, kept in separate compartments.
They power four propeller shafts and can produce a maximum speed of over 30 knots and maximum
power of 260,000 bhp. The reactors produce heat through nuclear fission which heats water.
This is then passed through four turbines which are shared by the two reactors. The
turbines power the four bronze propellers, each with a diameter of 25 feet and a weight
of 66,000 pounds. Behind these are the two rudders which are 29 feet high and 22 feet
long, and each weigh 110,000 pounds. The Nimitz-class ships constructed since USS Ronald Reagan
also have bulbous bows in order to improve speed and fuel efficiency by reducing hydrodynamic
drag. As a result of the use 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 three or four NATO RIM-7
Sea Sparrow missile launchers designed for defense against aircraft and anti-ship missiles
as well as either three or four 20 mm Phalanx CIWS missile defense cannon. USS Ronald Reagan
has none of these, having been built with the RIM-116 Rolling Airframe Missile system,
two of which have also been installed on USS Nimitz and USS George Washington. 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 2.5 in Kevlar armor over
vital spaces, and earlier ships have been retrofitted with it: Nimitz in 1983–1984,
Eisenhower from 1985–1987 and Vinson in 1989.
The other countermeasures the ships use are four Sippican SRBOC six-barrel MK36 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(V) electronic warfare 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 of this, as well as concerns over the safety of nuclear
power, the presence of a U.S. aircraft carrier in a foreign port has occasionally provoked
protest from local people, for example when USS Nimitz docked in Chennai, India, in 2007.
At that time, the Strike Group commander Rear Admiral John Terence Blake stated that: "The
U.S. policy is that we do not routinely deploy nuclear weapons on board Nimitz."
Carrier air wing
In order for a carrier to deploy, it must embark one of ten Carrier Air Wings. The carriers
can accommodate a maximum of 130 F/A-18 Hornets or 85–90 aircraft of different types, but
current numbers are typically 64 aircraft. Although the air wings are integrated with
the operation of the carriers they are deployed to, they are nevertheless regarded as a separate
entity. As well as the aircrew, the air wings are also made up of support personnel involved
in roles including maintenance, aircraft and ordnance handling and emergency procedures.
Each person on the flight deck wears color-coded clothing to make their role easily identifiable.
A typical carrier air wing can include 12–14 F/A-18E or F Super Hornets as strike fighters;
two squadrons of 10–12 F/A-18C Hornets, with one of these often provided by the U.S.
Marine Corps, also as strike fighters; 4–6 EA-6B Prowlers for electronic warfare; 4–6
E-2C Hawkeyes used for airborne early warning; C-2 Greyhounds used for logistics; and a Helicopter
Antisubmarine Squadron of 6–8 SH-60F & HH-60H Seahawks. Aircraft that have previously operated
from Nimitz-class carriers include F-4 Phantoms, RA-5C Vigilantes, RF-8G Crusaders, F-14 Tomcats,
S-3 Vikings, A-7 Corsair II and A-6E Intruder aircraft.
Flight deck and aircraft facilities
The flight deck is angled at nine degrees, which allows for aircraft to be launched and
recovered simultaneously. This angle of the flight deck was reduced slightly in relation
to previous carriers, as the current design improves the air flow around the carrier.
Four steam catapults are used to launch fixed-wing aircraft, and four arrestor wires are used
for recovery. The two newest carriers, Ronald Reagan and George H.W. Bush, only have three
arrestor wires each, as the fourth was used infrequently on earlier ships and was therefore
deemed unnecessary. This CATOBAR arrangement allows for faster launching and recovery as
well as a much wider range of aircraft that can be used on board compared with smaller
aircraft carriers, most of which use a simpler STOVL arrangement without catapults or arrestor
wires. The ship's aircraft operations are controlled by the air boss from Primary Flight
Control or Pri-Fly. Four large elevators transport aircraft between the flight deck and the hangars
below. These hangars are divided into three bays by thick steel doors that are designed
to restrict the spread of fire. Strike groups
When an aircraft carrier deploys, it takes a Strike Group, made up of several other warships
and supply vessels which allow the operation to be carried out. The armament of the Nimitz
class is made up only of short range defensive weapons, used as a last line of defense against
enemy missiles and aircraft. The other vessels in the Strike Group provide additional capabilities,
such as long range Tomahawk missiles or the Aegis Combat System, and also protect the
carrier from attack. A typical Strike Group may include, in addition to an aircraft carrier:
up to six surface combatants, including frigates, guided missile cruisers and guided missile
destroyers; one or two attack submarines; and an ammunition, oiler, and supply ship
of Military Sealift Command to provide logistical support. The precise structure and numbers
of each type of ship can vary between groups depending on the objectives of the deployment.
Design differences within the class While the designs of the final seven ships
are slightly different from those of the earlier ships, the U.S. Navy considers all ten carriers
as a single class. When the older carriers come in for Refueling and Complex Overhaul,
their nuclear power plants are refueled and they are upgraded to the standards of the
later carriers. Other modifications may be performed to update the ships' equipment.
The ships were initially classified only as attack carriers but have been constructed
with anti-submarine capabilities since USS Carl Vinson. These improvements include better
radar systems and facilities which enable the ships to operate aircraft in a more effective
anti-submarine role, including the fitting of common undersea picture technology which
uses sonar to allow for better assessment of the threat from submarines. The changes
included better support for S-3 Viking ASW patrol planes and SH-60F Seahawk helicopters
with dipping sonar systems.
USS Theodore Roosevelt and later carriers have slight structural differences from the
earlier Nimitz carriers such as improved protection for ordnance stored in their magazines. Other
improvements include upgraded flight deck ballistic protection, first installed on USS
George Washington, and the high-strength low-alloy steel used for constructing ships starting
with USS John C. Stennis. More recently, older ships have had their flight decks upgraded
with a non-slip material fitted on new-build ships, to improve safety for both crew members
and aircraft. The final carrier of the class, USS George
H.W. Bush, was designed as a "transition ship" from the Nimitz class to the replacement Gerald
R. Ford class. Bush incorporates new technologies including improved propeller and bulbous bow
designs, a reduced radar signature and electronic and environmental upgrades. As a result, the
ship's cost was $6.2 billion, higher than that of the earlier Nimitz-class ships which
each cost around $4.5 billion. To lower costs, some new technologies and design features
were also incorporated into the USS Ronald Reagan, the previous carrier, including a
redesigned island. Ships in class
The United States Navy lists the following ten ships in the Nimitz class:
Service history 1975–1989
One of the first major operations in which the ships were involved was Operation Eagle
Claw launched by USS Nimitz in 1980 after she had deployed to the Indian Ocean in response
to the taking of hostages in the U.S. embassy in Tehran. Although initially part of the
U.S. Atlantic Fleet, Eisenhower relieved Nimitz in this operation after her service in the
Mediterranean Sea. Nimitz conducted a Freedom of Navigation exercise alongside the aircraft
carrier USS Forrestal in August 1981 in the Gulf of Sidra, near Libya. During this exercise,
two of the ship's F-14 Tomcats shot down two Libyan aircraft in what became known as the
Gulf of Sidra incident. In 1987, Vinson participated in the first U.S. carrier deployment in the
Bering Sea, and Nimitz provided security during the 1988 Olympic Games in Seoul.
1990–2000
The two most significant deployments the Nimitz class was involved in during the 1990s were
the Gulf War and its aftermath, and Operation Southern Watch in southern Iraq. All active
vessels were engaged in both of these to some extent, with Operation Southern Watch continuing
until 2003. However, most carriers in operation in Operation Desert Shield and Operation Desert
Storm played supporting roles, with only Roosevelt playing an active part in combat operations.
Throughout the 1990s and more recently, Nimitz-class carriers have been deployed as part of humanitarian
missions. While deployed in the Gulf War, Lincoln was diverted to the Indian Ocean to
participate alongside 22 other ships in Operation Fiery Vigil, evacuating civilians following
the eruption of Mt. Pinatubo on Luzon Island in the Philippines. In October 1993, Lincoln
deployed to Somalia to assist UN humanitarian operations there, spending four weeks flying
patrols over the area around Mogadishu while supporting U.S. troops during Operation Restore
Hope. The same ship also participated in Operation Vigilant Sentinel in the Persian Gulf in 1995.
Roosevelt flew patrols in support of the Kurds over northern Iraq as part of Operation Provide
Comfort in 1991. In 1996, George Washington played a peacekeeping role in Operation Decisive
Endeavor in Bosnia and Herzegovina. In 1999, Roosevelt was called to the Ionian Sea to
support Operation Allied Force alongside other NATO militaries.
2001–present
Harry S. Truman's maiden deployment was in November 2000. The carrier's air wing flew
869 combat sorties in support of Operation Southern Watch, including a strike on Iraqi
air defense sites on 16 February 2001, in response to Iraqi surface-to-air missile fire
against United Nations coalition forces.
After the 11 September attacks, Carl Vinson and Theodore Roosevelt were among the first
warships to participate in Operation Enduring Freedom in Afghanistan. Carl Vinson sailed
towards the Persian Gulf intending to support Operation Southern Watch in July 2001. This
changed in response to the attacks, and the ship changed course to travel towards the
North Arabian Sea, where she launched the first airstrikes in support of the operation
on 7 October 2001. Following the attacks, John C. Stennis and George Washington participated
in Operation Noble Eagle, carrying out homeland security operations off the West Coast of
the United States. All active ships have been involved to some extent in Iraq and Afghanistan
since that time. This included the invasion in 2003, as well as providing subsequent support
for Operation Iraqi Freedom since then. The carriers have also provided aid after
natural disasters; in 2005, Abraham Lincoln supported Operation Unified Assistance in
Indonesia after the December 2004 tsunami, and Truman provided aid after Hurricane Katrina
later in 2005. The Reagan Carrier Strike Group performed humanitarian assistance and disaster
relief operations in the Philippines in June 2008 after Typhoon Fengshen, which killed
hundreds from the central island regions and the main island of Luzon. In January 2010
Vinson operated off Haiti, providing aid and drinking water to earthquake survivors as
part of the U.S. led Operation Unified Response, alongside other major warships and hospital
ship Comfort. In 2013, the USS Nimitz and other Nimitz class carriers are near Syria.
Refueling Complex Overhaul In order to refuel their nuclear power plants,
the carriers each undergo a Refueling Complex Overhaul once in their service lives. This
is also the most substantial overhaul the ships undergo while in service and involves
bringing the vessels' equipment up to the standards of the newest ships. The ship is
placed in dry dock, and essential maintenance is carried out including painting of the hull
below the waterline and replacement of electrical and mechanical components such as valves.
Because of the large time periods between the ships' constructions, the armament and
designs of the newer ships are more modern than those of the older ships. In RCOH, the
older ships are refitted to the standards of the newer ships, which can include major
upgrades to the flight deck, aircraft catapults and combat systems as well as other upgrades
such as improved radar systems, although precise details can vary significantly between the
ships. The improvements normally take around four years to complete. The RCOH for USS Theodore
Roosevelt, which began in 2009, will reportedly cost US$2.4 billion. Planned Incremental
Availability is a similar procedure, although it is less substantial and does not involve
refueling of the nuclear power plants. Symbolic and diplomatic roles
Because of their status as the largest warships in the U.S. Navy, the deployment of an aircraft
carrier can fulfill a symbolic role, not just in terms of a deterrent to an enemy, but often
as a diplomatic tool, in strengthening relations with allies and potential allies. The latter
of these functions can take place either as a single visit to a country, in which senior
naval officers are allowed to observe the operating of the carrier and to interact with
its senior officers, or as part of an international task force. This can be in combat operations,
such as Operation Allied Force in 1999, or other deployments involving training, such
as RIMPAC. In addition, carriers have participated in international Maritime Security Operations,
combating piracy in the Persian Gulf and off the coast of Somalia.
Accidents and incidents As on most large warships, there have been
several incidents involving the death or injury of one or more crew members, although most
have involved freak accidents or failures, such as a man overboard as a result of poor
weather. One of the highest-profile incidents was on 26 May 1981, when an EA-6B Prowler
crashed on the flight deck of Nimitz, killing 14 crewmen and injuring 45 others. Forensic
testing of the personnel involved showed that several tested positive for marijuana. While
this was not in itself found to have directly caused the crash, the findings of the investigation
provoked the introduction of mandatory drug testing of all service personnel.
In cases of ditched aircraft, pilots have been able to eject safely in several cases.
However, fatal aircraft crashes have occurred; in 1994, Lt. Kara Hultgreen, the first female
F-14 Tomcat pilot, was killed while attempting to land on board Abraham Lincoln during a
training exercise. Fires have also caused damage to the ships;
in May 2008, while rotating through to her new homeport at Yokosuka Naval Base in Yokosuka,
Japan, George Washington suffered a serious fire which cost $70 million in repairs, injured
37 sailors and led to the ship undergoing three months of repairs at San Diego; this
led to it having to miss the 2008 RIMPAC exercises and delayed the final withdrawal from service
of USS Kitty Hawk. The fire was caused by unauthorized smoking in an area near improperly
stored flammable refrigerant. Future
Nimitz-class carriers were designed to have a 50-year service life. At the end of the
service life, ships will be decommissioned. This process will first take place on Nimitz
and is estimated to cost from $750 to $900 million. This compares with an estimate of $53 million
for a conventionally powered carrier. Most of the difference in cost is attributed to
the deactivation of the nuclear power plants and safe removal of radioactive material and
other contaminated equipment. A new class of carriers, the Gerald R. Ford class, is
being constructed to replace previous vessels after decommissioning. Ten of these are expected,
and the first will enter service in 2016 to replace the previous USS Enterprise. Most
of the rest of these new carriers are to replace the oldest Nimitz ships as they reach the
end of their service lives. The new carriers will have a similar design to George H.W.
Bush and technological and structural improvements. See also
Gerald R. Ford class aircraft carrier List of aircraft carriers
List of naval ship classes in service List of aircraft carrier classes of the United
States Navy Modern US Navy carrier air operations
Naval aviation Aircraft Carrier
Notes Footnotes
Citations
References Friedman, Norman. U.S. Aircraft Carriers:
An Illustrated Design History. Annapolis, Maryland: Naval Institute Press. ISBN 978-0-87021-739-5.
Lambeth, Benjamin. American Carrier Air Power at the Dawn of a New Century. Santa Monica,
California: RAND Corporation. ISBN 978-0-8330-3842-5. Polmar, Norman. The Naval Institute Guide
to the Ships and Aircraft of the U.S. Fleet. Annapolis, Maryland: Naval Institute Press.
ISBN 978-1-59114-685-8. Stevens, Ted. Navy Aircraft Carriers: Cost-effectiveness
of Conventionally and Nuclear-powered Carriers: Report to Congressional Requesters. Washington,
D.C.: Government Accountability Office. ISBN 1-4289-7664-7. Wertheim, Eric. The Naval Institute Guide
to Combat Fleets of the World: Their Ships, Aircraft and Systems. Annapolis, Maryland:
Naval Institute Press. ISBN 978-1-59114-955-2. Further reading
Schank, John F.; Mark V. Arena; Denis Rushworth; John Birkler; James Chiesa. Refueling and
Complex Overhaul of the USS Nimitz: Lessons for the Future. Santa Monica, California:
Rand Corporation. ISBN 0-8330-3288-7. Retrieved 2010-12-04.
External links U.S. Navy website
Discovery channel video Naval Vessel Register page for USS Nimitz
Busting the speed myth of USS Enterprise and Nimitz-class nuclear-powered supercarrier,
a special report by NavWeaps.Com CVN-68 Nimitz-class Modernization – GlobalSecurity.org