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Design and
development
The Nimitz-class aircraft carrier has been an integral part of United States
power projection strategy since Nimitz was first commissioned. Displacing
approximately 100,000 tons when fully loaded, a Nimitz-class carrier is
capable of steaming faster than thirty knots, self-sustaining for up to
ninety days, and launching aircraft to strike targets hundreds of miles away.
The endurance of this class can be exemplified by USS Theodore Roosevelt,
which spent 159 days underway in support of Operation Enduring Freedom
without the need to be refueled or visit a port.
Over the lifespan of the class many new technologies have been successfully
integrated into the design of this vessel. However, with the technical
advances made in the past decade the ability of the US Navy to make
improvements to this class of ship has been limited by hard constraints. “The
biggest problems facing the Nimitz-class are the limited electrical power
generation capability and the upgrade-driven increase in ship weight and
erosion of the center of gravity margin needed to maintain ship stability.”
With these constraints in mind the Navy developed what was initially known as
the "CVN-21" program, which ultimately evolved into CVN-78, Gerald
R. Ford. Improvements were made through developing technologies and more
efficient design. Major design changes include a larger flight deck,
improvements in weapons and material handling, a new propulsion plant design
that requires fewer personnel to operate and maintain, and a new smaller
island that has been pushed aft. Technological advances in the field of
electromagnetics have led to the development of an Electromagnetic Aircraft
Launching System, (EMALS), and an Advanced Arresting Gear, (AAG). An
integrated warfare system has been developed to support flexibility in
adapting the infrastructure of the ship to future mission roles. The new Dual
Band Radar (DBR) combines S-band and X-band radar in a single system. With
new design and technology the Ford will have a 25% increase in sortie
generation, threefold increase in electrical generating capacity, increased
operational availability, and a number of quality of life improvements.
Requirements for a higher sortie rate of around 160 exits a day with surges
to a maximum of 220 sorties a day in times of crisis and intense air warfare
activity, has led to design changes in the flight deck, which enable greater
aircraft launch capabilities.
Flight deck
Changes to the flight deck are the most visible of the differences between the
Nimitz and Gerald R. Ford classes. Several sections have been added to the
layout of Nimitz's flight deck to improve aircraft handling, storage, and
flow. Catapult number four on the Nimitz class cannot launch fully loaded
aircraft because of a deficiency of wing clearance along the edge of the
flight deck. CVN-78 will have no catapult specific restrictions on launching
aircraft. The design changes to the flight deck are instrumental in the
maximization of sortie generation.
The flow of weapons to the aircraft stops on the flight deck has been
upgraded to accommodate for the higher sortie rates. The ship carries a store
of missiles and cannon rounds for fighter aircraft, bombs and air-to-surface
missiles for strike aircraft, and torpedoes and depth charges for
anti-submarine warfare aircraft.
Another major change; a smaller, redesigned island will be pushed further
back relative to the older classes of carriers. Moving the island creates
deck space for a centralized re-arming and re-fueling location. This reduces
the number of times that an aircraft will have to be moved after landing
before it can be launched again. Fewer aircraft movements require, in turn,
fewer deck hands to accomplish them, reducing the size of the ship's crew. A
similar benefit is realized from altering the path and procedures for weapons
movement by redshirts from storage to flight deck means that weapons are
moved from storage to the flight deck; the new ship can support a higher
sortie rate than the Nimitz class ship while using fewer crew members than
the Nimitz requires. On Nimitz-class carriers the time that it takes to
launch a plane after it has landed is defined by the time necessary to
re-arm. To minimize this time, ordnance will be moved by robotic devices from
storage areas to the centralized re-arming location via re-located weapons
elevators. The new path that ordnance follows does not cross any areas of
aircraft movement, thereby reducing traffic problems in the hangars and on
the flight deck. According to Rear Admiral Dennis M. Dwyer these changes will
make it possible to re-arm the airplanes in "minutes instead of
hours."
Power generation
The propulsion and power plant of the Nimitz-class carriers was designed in
the 1960s. Technological capabilities of that time did not require the same
quantity of electrical power that modern technologies do. "New
technologies added to the Nimitz-class ships have generated increased demands
for electricity; the current base load leaves little margin to meet expanding
demands for power." Increasing the capability of the U.S. Navy to
improve the technological level of the carrier fleet required a larger
capacity power system.
The new A1B reactor plant is a smaller, more efficient, design that provides
approximately three times the electrical power of the Nimitz-class A4W
reactor plant. The modernization of the plant led to a higher core energy
density, lower demands for pumping power, a simpler construction, and the use
of modern electronic controls and displays. These changes resulted in a two
thirds reduction of watch standing requirements and a significant decrease of
required maintenance.
A larger power output is a major component to the integrated warfare system.
Engineers took extra steps to ensure that integrating unforeseen technological
advances onto a Gerald R. Ford-class aircraft carrier would be possible. The
Nimitz class will be an integral component of the fleet for a total of nearly
ninety years. One lesson learned from that is for a ship design to be
successful over the course of a century requires a great deal of foresight
and flexibility. Integrating new technologies with the Nimitz class is
becoming more difficult to do without any negative consequences. To bring the
Gerald R. Ford class into dominance during the next century of naval warfare
requires that the class be capable of seamlessly upgrading to more advanced
systems.
Launch systems
The Nimitz-class aircraft carriers use steam-powered catapults to launch
aircraft. Steam catapults were developed in the 1950s and have been
exceptionally reliable. For over fifty years at least one of the four
catapults has been able to launch an aircraft 99.5% of the time. However,
there are a number of drawbacks. “The foremost deficiency is that the
catapult operates without feedback control. With no feedback, there often
occurs large transients in tow force that can damage or reduce the life of
the airframe.” The steam system is massive, inefficient (4–6%), and hard to
control.
Control problems with the system results in minimum and maximum weight
limits. The minimum weight limit is above the weight of all UAVs. An
inability to launch the latest additions to the Naval Air Forces is a
restriction on operations that cannot continue into the next generation of
aircraft carriers. The Electromagnetic Aircraft Launch System provides
solutions to all these problems. An electromagnetic system is more efficient,
smaller, lighter, more powerful, and easier to control. Increased control
means that EMALS will be able to launch both heavier and lighter aircraft
than the steam catapult. Also, the use of a controlled force will reduce the
stress on airframes, resulting in less maintenance and a longer lifetime for
the airframe. Unfortunately the power limitations for the Nimitz class make
the installation of the recently developed EMALS impossible.
Electromagnetics will also be used in the new Advanced Arresting Gear system.
The current system relies on hydraulics to slow and stop a landing aircraft.
While effective, as demonstrated by more than fifty years of implementation,
the AAG system offers a number of improvements. The current system is unable
to capture UAVs without damaging them due to extreme stresses on the
airframe. UAVs do not have the necessary mass to drive the large hydraulic piston
used to trap heavier manned planes. By using electromagnetics the energy
absorption is controlled by a turbo-electric engine. This makes the trap
smoother and reduces shock on airframes. Even though the system will look the
same on the flight deck it will be more flexible, safe, reliable, and require
less maintenance and manning.
Communications
Another new addition to Gerald R. Ford class is an integrated search &
tracking radar system. The Dual-band radar is being developed for both the
DDG 1000 Zumwalt class of guided missile destroyers and the Gerald R. Ford
class of aircraft carriers. The island can be kept smaller by replacing six
to ten radar antennas with a single six-faced radar. The DBR works by
combining the X-Band AN/SPY-3 Multi-Function Radar with the S-Band Volume
Search Radar. The three faces dedicated to the X-band radar are responsible
for low altitude tracking and target illumination, while the other three
faces dedicated to the S-band are responsible for target search and tracking regardless
of weather. “Operating simultaneously over two electromagnetic frequency
ranges, the DBR marks the first time this functionality has been achieved
using two frequencies coordinated by a single resource manager.” This new
system has no moving parts, therefore minimizing maintenance and manning
requirements for operation.
Possible upgrades
Each new technology and design feature integrated into the Ford-class
aircraft carrier improves sortie generation, manning requirements, and
operational capabilities. Preparing for the future is a trademark of Gerald
R. Ford. New defense systems, such as free electron laser directed-energy
weapons, dynamic armor, and tracking systems will require more power. “Only
half of the electrical power-generation capability on CVN 78 is needed to run
currently planned systems, including EMALS. CVN 78 will thus have the power
reserves that the Nimitz class lacks to run lasers and dynamic armor.” The
addition of new technologies, power systems, design layout, and better control
systems results in an increased sortie rate of 25% over the Nimitz class and
a 25% reduction in manpower required to operate.
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