Current steam catapults use about 615 kg/ 1,350 pounds of steam for each aircraft launch, which is usually delivered by piping it from the nuclear reactor. Now add the required hydraulics and oils, the water required to brake the catapult, and associated pumps, motors, and control systems. The result is a large, heavy, maintenance-intensive system that operates without feedback control; and its sudden shocks affect airframe lifespans for carrier-based aircraft. The Aircraft carrier will have two A1B nuclear reactors for 600 MW of power.
EMALS (Electro-Magnetic Aircraft Launch System) uses an approach analogous to an electro-magnetic rail gun, in order to accelerate the shuttle that holds the aircraft. That approach provides a smoother launch, while offering up to 30% more launch energy potential to cope with heavier fighters. It also has far lower space and maintenance requirements, because it dispenses with most of the steam catapult’s piping, pumps, motors, control systems, etc. It also offers ancillary benefits, like the ability to embed diagnostic systems.
The challenge is scaling a relatively new technology to handle the required weights and power. EMALS motor generator weighs over 80,000 pounds, and is 13.5 feet long, almost 11 feet wide and almost 7 feet tall. It’s designed to deliver up to 60 megajoules of electricity, and 60 megawatts at its peak. In the 3 seconds it takes to launch a Navy aircraft, that amount of power could handle 12,000 homes. This motor generator is part of a suite of equipment called the Energy Storage Subsystem, which includes the motor generator, the generator control tower and the stored energy exciter power supply. The new Gerald R. Ford Class carriers will require 12 of each.
Control problems with the old steam launch 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 Force is a restriction on operations that cannot continue into the next generation of aircraft carriers. The Electromagnetic Aircraft Launching System provides solutions to all these problems.
The first full size test motor generator for the Navy’s Electromagnetic Aircraft Launch System (EMALS) was assembled, and finished its 30 days of factory acceptance testing at Kato Engineering’s plant in Mankato, MN on April 11, 2008. 5 units are being manufactured under General Atomics’ Systems Development & Demonstration contract. One is slated for component level testing, and 4 will be installed and used for system level testing at the Lakehurst, N.J., EMALS catapult site.
Four Main Sub-systems
* Linear induction motor
The linear induction motor (LIM) is the main component of the EMALS. It consists of a row of stator coils that, when energized, accelerate the carriage (equivalent to a conventional motor’s rotor) down the track. Only the section of the stator coils surrounding the carriage is energized at any given time, minimizing reactive losses. The EMALS will use a 300 ft (91 m) long LIM capable of launching a 100,000 lb (45,000 kg) aircraft to 130 knots (240 km/h).
* Energy storage subsystem
To power the LIM, the EMALS requires a large amount of electric energy to be used in a short amount of time. The ship’s power source cannot provide this much immediate energy, so the energy-storage subsystem accumulates power from the ship and stores it kinetically on rotors of four disk alternators. Each rotor can store more than 100 MJ, and can be recharged within 45 seconds of a launch.
* Power conversion subsystem
At the time of launch, the power conversion subsystem releases the stored energy from the disk alternators in a controlled manner by using a cycloconverter. The cycloconverter provides a controlled rising frequency and voltage to the LIM, energizing only the small portion of stator coils that affect the launch carriage at each instant in time.
* Control consoles
The power used by the EMALS is controlled through a closed loop system to give the operators complete control over the system’s performance. A number of Hall effect sensors positioned on the track provide feedback to the control consoles, allowing the system to monitor itself and ensure that it provides the desired acceleration. The closed loop control system allows the EMALS to maintain a constant tow force, which helps reduce the launch stresses on the plane’s airframe
Other New Technology for the New Aircraft Carrier
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 life improvements.
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.
The Dual Band Radar works by combining the X-Band AN/SPY-3 Multi-Function Radar with the S-Band Volume Search Radar.
New defense systems, such as laser guns, dynamic armor, and tracking systems will require more power and the Gerald Ford Aircraft has been designed for easy integration of new laser and rail gun and other advanced systems as they become available.
The new A1B reactor will generate about 300MW (three times as much as the current A4W reactor), which is about 420,000 horsepower.
2005 RAND document on the plan to modernize the US Navy
-High-Energy Liquid Laser Area Defense System (Hellads), a US Defense Advanced Research Projects Agency program set to produce refridgerator sized 150 Kilowatt lasers for about 2013
-Navy has multi-megawatt lasers funded for over $160 million in a five year program started in 2008
– Navy’s goal of developing a tactical 64-megajoule ship-mounted railgun weapon.
– BAE Systems has delivered a functional, 32-megajoule Electro-Magnetic Laboratory Rail Gun (32-MJ LRG) to the U.S. Naval Surface Warfare Center in Dahlgren, Va. in
At full capability, the rail gun will be able to fire a a 40-pound projectile more than 200 nautical miles at a muzzle velocity of mach seven and impacting its target at mach five. In contrast, the current Navy gun, MK 45 five-inch gun, has a range of nearly 13 miles. The high velocity projectile will destroy its targets due to its kinetic energy rather than with conventional explosives.
-2012 field trials
-The program’s goal is to demonstrate a full capability, integrated railgun prototype by 2016-2018
-Defense Industry analysts believe it will take longer than navy goals to get railguns. They think it will take until 2020-2024 to integrate railguns into navy ships.
Free Electron Lasers (FEL)
The FEL is a unique, electrically powered device that offers the potential for high average power, essentially unlimited run time with good beam quality and operation at a wavelength of the designer’s choosing. It functions by extracting kinetic energy from a relativistic, free (unbound) electron beam (ebeam) and converting it to electromagnetic (EM) radiation. The EM radiation is achieved by passing the ebeam
through an alternating magnetic field in a device called an “undulator” or “wiggler”. The spatially periodic wiggler magnetic field induces transverse force on the electrons causing them to produce EM radiation in the forward direction of the ebeam.
FEL oscillators and amplifiers have been demonstrated to produce an electrically driven, powerful source of wavelength selectable, coherent EM radiation.
Current plans for the FEL include largescale development under an ONR Code 35 Innovative Naval Prototype (INP) Program planned to begin in FY 2010. To achieve the longterm goal with respect to a FEL for the “next navy”, the major nearterm focus areas are:
1. Development of a 100kW, preferably upgradeable, FEL with a working wavelength that can range between 1.00 and 2.20 micrometer depending on the atmospheric conditions.
2. A MW (megawatt) class beam control system to integrate with the FEL. The FEL offers technically challenging control issues for both electron and photon beams in the laser systems of interest.