Electromagnetic Aircraft Launch System
Encyclopedia
| EMALS | |
 |
|
| End Speed | 28–103 m/s |
| Max Peak-to-Mean Tow Force Ratio | 1.05 |
| Launch Energy | 122 MJ |
| Cycle Time | 45 seconds |
| System Weight | < 225,000 kg |
| System Volume | < 425 m³ |
| Endspeed Variation | |
The Electromagnetic Aircraft Launch System, (commonly EMALS) is a system under development by the United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
to launch carrier-based aircraft from catapults
Aircraft catapult
An aircraft catapult is a device used to launch aircraft from ships—in particular aircraft carriers—as a form of assisted take off. It consists of a track built into the flight deck, below which is a large piston or shuttle that is attached through the track to the nose gear of the aircraft, or in...
using a linear motor
Linear motor
A linear motor is an electric motor that has had its stator and rotor "unrolled" so that instead of producing a torque it produces a linear force along its length...
drive instead of conventional steam pistons. This technology reduces stress on airframes because they can be accelerated more gradually to takeoff speed than steam-powered catapults.
Other advantages includes lower system weight, cost, and maintenance; the ability to launch 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 AtomicsGeneral Atomics
General Atomics is a nuclear physics and defense contractor headquartered in San Diego, California. General Atomics’ research into fission and fusion matured into competencies in related technologies, allowing the company to expand into other fields of research...
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 motorLinear induction motor
A linear induction motor is an AC asynchronous linear motor that works by the same general principles as other induction motors but which has been designed to directly produce motion in a straight line....
(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
Stator
The stator is the stationary part of a rotor system, found in an electric generator, electric motor and biological rotors.Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the...
coils that have the function of a conventional motor’s rotor. 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, minimizing reactive losses. The EMALS' 300 feet (91.4 m) LIM will accelerate a 100000 pounds (45,359.2 kg) aircraft to 130 knots (254.8 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. EMALS' energy-storage subsystem draws power from the ship and stores it kinetically on rotors of four disk alternatorAlternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...
s. 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 cycloconverterCycloconverter
A cycloconverter or a cycloinverter converts an AC waveform, such as the mains supply, to another AC waveform of a lower frequency, synthesizing the output waveform from segments of the AC supply without an intermediate direct-current link . They are most commonly used in three-phase...
. 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.
Control consoles
Operators control the power through a closed loop system. Hall effectHall effect
The Hall effect is the production of a voltage difference across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current...
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.
Program status
- 18 December 2010: Successful launch of a F/A-18E Super Hornet at Naval Air Engineering Station LakehurstNaval Air Engineering Station LakehurstJB MDL Lakehurst is a United States Navy base located approximately south-southeast of Trenton, New Jersey. Lakehurst is under the jurisdiction of the Naval Air Systems Command...
.
- June 1-2 2010: Successful launch of a T-45 GoshawkT-45 Goshawk|-Avionics:Data from naval-technology.com *Smiths Industries, Ltd. AN/USN-2 Standard Attitude Heading and Reference System . Later replaced by the BAE/Marconi AN/ASN-180 Navigation Guidance System ....
at Naval Air Engineering Station LakehurstNaval Air Engineering Station LakehurstJB MDL Lakehurst is a United States Navy base located approximately south-southeast of Trenton, New Jersey. Lakehurst is under the jurisdiction of the Naval Air Systems Command...
.
- June 9-10 2010: Successful launch of a C-2 Greyhound at Naval Air Engineering Station LakehurstNaval Air Engineering Station LakehurstJB MDL Lakehurst is a United States Navy base located approximately south-southeast of Trenton, New Jersey. Lakehurst is under the jurisdiction of the Naval Air Systems Command...
.
- 27 September 2011: Successful launch of a E-2D Advanced Hawkeye at Naval Air Engineering Station LakehurstNaval Air Engineering Station LakehurstJB MDL Lakehurst is a United States Navy base located approximately south-southeast of Trenton, New Jersey. Lakehurst is under the jurisdiction of the Naval Air Systems Command...
.
Advantages
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, which would reduce the aircraft’s takeoff speed and consequently the launch energy required.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 be more efficient than the 5-percent efficiency of steam catapults.
Systems to use EMALS
EMALS is a design feature of the Ford class carrier.Converteam
Converteam
Converteam was an electrical engineering company based in France, and a former division of Alstom. It is now part of General Electric-History:...
UK is working on a electro-magnetic catapult (EMCAT) system for the Queen Elizabeth class aircraft carrier. In August 2009, speculation mounted that the UK may drop the STOVL F-35B for the CTOL F-35C model, which would mean the carriers being built to operate conventional (CV) take off and landing aircraft utilizing the UK-designed non-steam EMCAT catapults.
In October 2010, the UK Government announced it had opted to buy the future F-35C stealth fighter to fly off its carriers, using an undecided CATOBAR
CATOBAR
CATOBAR is a system used for the launch and recovery of aircraft from the deck of an aircraft carrier...
system.
See also
- Naval aviationNaval aviationNaval aviation is the application of manned military air power by navies, including ships that embark fixed-wing aircraft or helicopters. In contrast, maritime aviation is the operation of aircraft in a maritime role under the command of non-naval forces such as the former RAF Coastal Command or a...
- Modern United States Navy carrier air operations
- CoilgunCoilgunA coilgun is a type of projectile accelerator that consists of one or more coils used as electromagnets in the configuration of a synchronous linear motor which accelerate a magnetic projectile to high velocity...
- Mass driverMass driverA mass driver or electromagnetic catapult is a proposed method of non-rocket spacelaunch which would use a linear motor to accelerate and catapult payloads up to high speeds. All existing and contemplated mass drivers use coils of wire energized by electricity to make electromagnets. Sequential...
External links
- "Electromagnetic Aircraft Launch System - EMALS", GlobalSecurity.org