A great idea for US navy aircraft carriers. An aircraft carrier is a warship with a full-length flight deck and facilities for carrying, arming, deploying, rescuing and recovering aircraft, acting as a seagoing airbase. It is typically the capital ship of a fleet, as it allows a naval force to project airpower worldwide without having to depend on local bases for staging aircraft operations, and is extremely expensive to build and important to protect.
The Electromagnetic Aircraft Launch System (EMALS) is a system under development by the United States Navy to launch carrier-based aircraft from catapults using a linear motor drive instead of conventional steam pistons. This technology reduces stress on airframes because they can be accelerated more gradually to takeoff speed than with steam-powered catapults.
Other advantages includes lower system weight, cost, and maintenance; the ability to launch both heavier and lighter aircraft than conventional systems; and lower requirements for fresh water, reducing the need for energy-intensive desalination.
Design and development
The EMALS is being developed by General Atomics for the U.S. Navy’s newest Gerald R. Ford-class aircraft carriers.
In June 2010, the land-based prototype of the system passed initial tests, with the first aircraft launch from the system taking place at the end of 2010.
Linear induction motor
The EMALS uses a linear induction motor (LIM), which uses electric currents to generate magnetic fields that propel a carriage down a track to launch the aircraft. The EMALS consists of four main elements: The linear induction motor consists of a row of stator coils that have the function of a conventional motor’s armature. When energized, the motor accelerates the carriage down the track. Only the section of the coils surrounding the carriage is energized at any given time, thereby minimizing reactive losses. The EMALS’ 300-foot (91 m) LIM will accelerate a 100,000-pound (45,000 kg) aircraft to 130 knots (240 km/h).
Energy storage subsystem
The induction motor requires a large amount of electric energy in just a few seconds—more than the ship’s own power source can provide. The EMALS energy-storage subsystem draws power from the ship and stores it kinetically on rotors of four disk alternators. Each rotor can store more than 100 megajoules, and can be recharged within 45 seconds of a launch, faster than steam catapults.
Power conversion subsystem
During launch, the power conversion subsystem releases the stored energy from the disk alternators 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 any given moment.
Operators control the power through a closed loop system. Hall effect sensors on the track monitor its operation, allowing the system to ensure that it provides the desired acceleration. The closed loop system allows the EMALS to maintain a constant tow force, which helps reduce the launch stresses on the plane’s airframe.
Compared to steam catapults, EMALS weighs less, occupies less space, requires less maintenance and manpower, is more reliable, and uses less energy. Steam catapults, which use about 614 kilograms of steam per launch, have extensive mechanical, pneumatic, and hydraulic subsystems. EMALS uses no steam, which makes it suitable for the Navy’s planned all-electric ships. The EMALS could be more easily incorporated into a ramp.
Compared to steam catapults, EMALS can control the launch performance with greater precision, allowing it to launch more kinds of aircraft, from heavy fighter jets to light unmanned aircraft. EMALS can also deliver 29 percent more energy than steam’s approximately 95 megajoules, increasing the output to 122 megajoules. The EMALS will also be more efficient than the 5-percent efficiency of steam catapults.
The Electromagnetic Aircraft Launch System at Naval Air Systems Command, Lakehurst, launching a United States Navy F/A-18E Super Hornet during a test on 18 December 20101–2 June 2010: Successful launch of a T-45 Goshawk at Naval Air Engineering Station Lakehurst.
9–10 June 2010: Successful launch of a C-2 Greyhound at Naval Air Engineering Station Lakehurst.
18 December 2010: Successful launch of a F/A-18E Super Hornet at Naval Air Engineering Station Lakehurst.
27 September 2011: Successful launch of an E-2D Advanced Hawkeye at Naval Air Engineering Station Lakehurst.
18 November 2011: Successful launch of a F-35C Lightning II.
EMALS is a design feature of the Ford-class carrier.
Converteam UK were working on an electro-magnetic catapult (EMCAT) system for the Queen Elizabeth-class aircraft carrier. In August 2009, speculation mounted that the UK may drop the STOVL