electromagnetic aircraft launch system

7/14/2019 Electromagnetic Aircraft Launch System

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CONTENT

1. Introduction

2. Characteristics

3. Major sub systems

4. Advantages

5. Applications



1. Introduction

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.

Electromagnetic Aircraft Launch System (EMALS) is a complete launchsystem designed to replace the existing steam catapult currently being

used on aircraft carriers. The USS Gerald R. Ford, the first ship of the

CVN-21 Future Aircraft Carrier Class, will use electromagnetic launch

systems.



2. Services

EMALS provides:

Reduced Manning Workload

Reduced Thermal Signature

Increased Launch Availability

Reduced Topside Weight

Reduced Installed Volume

Launch capability for unmanned aerial vehicles

The EMALS system is a multimegawatt electric power system involving

generators, energy storage, power conversion, a 100,000 hp electric

motor, and an advanced technology closed loop control system with

diagnostic health monitoring. In addition to building the power

conversion and motor equipment, GA provides the power system

integration and logistics support for this state-of-the-art power electronic

system.



3. Major Sub systems

The EMALS consists of six major subsystems:

Prime Power Interface

This system provides the interconnect with the ship's electrical

distribution system and delivers power to drive the energy storage

generators.

Launch Motor

Developed in a linear induction motor configuration, the launch

motor is a compact, modular, integrated flight-deck structure that

converts electrical current into the electromagnetic forces to

accelerate the aircraft along the launch stroke. The motor design will

tolerate the range of conditions experienced in the flight-deck

environment and operating scenarios. A simple moving shuttle will

interface with the aircraft in the same manner as the existing

catapults. After the aircraft launches, the electric current in the motor

will reverse to brake the shuttle to a complete halt without the use of

a water brake.

Power Conversion Electronics



The power conversion electronics derive power from the energy

stored and convert this power to a traveling wave of energy of the

appropriate voltage and current to drive the shuttle along the launch

stroke. Based on solid-state technology GA uses in its line of

commercial power equipment, the power electronics are packaged as

compact modules in cabinets that are located below deck.

Launch ControlThe EMALS uses a state-of-the-art system to control the current into

the launch motor in real time. More precise endspeeds are achievable

over a wider range of aircraft types and weights over those of steam

catapults. The smoother acceleration may extend the lifetime of the

aircraft. High reliability and a system architecture with inherent

redundancy is achieved by use of commercial off-the-shelf

components where possible. Modularity is emphasized to ease

installation and maintenance — important factors in life cycle

planning.

Energy Storage

The required energy for a launch is drawn from the energy storage

devices during each two- to three-second launch. The energy storage



devices are recharged from ship’s power between launches. In March

2008, the program celebrated a milestone with the successful

completion of factory acceptance testing of the motor generator

component of the EMALS energy storage subsystem (ESS). Four

additional ESS systems will be built to support development testing

at the NAES Lakehurst, N.J., culminating in aircraft launches at the

test site.

Energy Distribution System

This system delivers the energy from the power conversion system to

the launch motor and comprises cables, disconnects, and

terminations.

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, 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 alaunch, 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 theLIM, 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

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.

Program status

The Electromagnetic Aircraft Launch System at Naval Air Systems

Command, Lakehurst, launching a United States Navy/A-18E Super

Hornet during a test on 18 December 2010

1 – 2 June 2010: Successful launch of a T-45 Goshawk at Naval Air

Engineering Station Lakehurst.[5]

9 – 10 June 2010: Successful launch of a C-2 Greyhound at Naval Air

Engineering Station Lakehurst.[6]

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.

http://en.wikipedia.org/wiki/Electromagnetic_Aircraft_Launch_System#cite_note-5










4. 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.

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 willalso be more efficient than the 5-percent efficiency of steam 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.



5.Applications

Systems to use EMALS

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 F-

35B for the CTOL F-35C model, which would have meant 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

F-35C, using a then-undecided CATOBAR system. A contract was

signed in December 2011 with the General Atomics Company of SanDiego to develop EMALS for the Queen Elizabeth-class

carriers. However, in May 2012, the UK Government reversed its

decision after the projected costs rose to double the original estimate and

delivery moved back to 2023, cancelling the F-35C option and reverting

to its original decision to buy the STOVL F-35B.

electromagnetic aircraft launch system

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