Electromagnetic Aircraft Launch System Informations

The Electromagnetic Aircraft Launch System (EMALS) is a type of aircraft launching system developed by General Atomics for the United States Navy. The system launches carrier-based aircraft by means of a catapult employing a linear induction motor rather than the conventional steam piston. EMALS was first installed on the United States Navys Gerald R. Ford-class aircraft carrier, USS Gerald R. Ford.

Its main advantage is that it accelerates aircraft more smoothly, putting less stress on their airframes. Compared to steam catapults, the EMALS also weighs less, is expected to cost less and require less maintenance, and can launch both heavier and lighter aircraft than a steam piston-driven system. It also reduces the carriers requirement of fresh water, thus reducing the demand for energy-intensive desalination.

China is reportedly developing a similar system.

Developed in the 1950s, steam catapults have proven exceptionally reliable. Carriers equipped with four steam catapults have been able to use at least one of them 99.5 percent of the time. However, there are a number of drawbacks. One group of Navy engineers wrote, "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. These control problems allow Nimitz-class aircraft carrier steam-powered catapults to launch heavy aircraft, but not aircraft as light as many UAVs.

A somewhat similar system to EMALS, Westinghouses electropult, was developed in 1946, but not deployed.

The EMALS uses a linear induction motor (LIM), which uses electric currents to generate magnetic fields that propel a carriage along a track to launch the aircraft. The EMALS consists of four main elements: The linear induction motor consists of a row of stator coils with the same function as the circular stator coils in a conventional induction motor. When energized, the motor accelerates the carriage along 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 kn (240 km/h; 150 mph).

During a launch, the induction motor requires a large surge of electric power that exceeds what the ships own continuous power source can provide. As of 1994[update], the EMALS energy-storage system design accommodates this by drawing power from the ship during its 45-second recharge period and storing the energy kinetically using the rotors of four disk alternators; the system then releases that energy (up to 484 MJ) in 2–3 seconds. Each rotor delivers up to 121 MJ (34 kWh) (approximately one gasoline gallon equivalent) and can be recharged within 45 seconds of a launch; this is faster than steam catapults. A maximum-performance launch using 121 MJ of energy from each disk alternator slows the rotors from 6400 rpm to 5205 rpm.

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 launch stresses on the planes airframe.

Aircraft Compatibility Testing (ACT) Phase 1 concluded in late 2011 following 134 launches (aircraft types comprising the F/A-18E Super Hornet, T-45C Goshawk, C-2A Greyhound, E-2D Advanced Hawkeye, and F-35C Lightning II) using the EMALS demonstrator installed at Naval Air Engineering Station Lakehurst. On completion of ACT 1, the system was reconfigured to be more representative of the actual ship configuration on board the USS Gerald R. Ford, which will use four catapults sharing several energy storage and power conversion subsystems.

ACT Phase 2 began on 25 June 2013 and concluded on 6 April 2014 after a further 310 launches (including launches of the Boeing EA-18G Growler and McDonnell Douglas F/A-18C Hornet, as well as another round of testing with aircraft types previously launched during Phase 1). In Phase 2 various carrier situations were simulated, including off-centre launches and planned system faults, to demonstrate that aircraft could meet end-speed and validate launch-critical reliability.

On 28 July 2017, Lt. Cmdr. Jamie "Coach" Struck of Air Test and Evaluation Squadron 23 (VX-23) performed the first EMALS catapult launch from USS Gerald R. Ford (CVN-78) in an F/A-18F Super Hornet.

Compared to steam catapults, EMALS weighs less, occupies less space, requires less maintenance and manpower, is more reliable, recharges quicker, and uses less energy. Steam catapults, which use about 1,350 lb (610 kg) of steam per launch, have extensive mechanical, pneumatic, and hydraulic subsystems. EMALS uses no steam, which makes it suitable for the Navys planned all-electric ships.

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. With up to 121 megajoules available, each one of the four disk alternators in the EMALS system can deliver 29 percent more energy than a steam catapults approximately 95 MJ. The EMALS, with their planned 90% power conversion efficiency, will also be more efficient than steam catapults, which achieve only a 5% efficiency.

In May 2017, President Donald Trump criticized EMALS during an interview with Time, saying that in comparison to traditional steam catapults, "the digital costs hundreds of millions of dollars more money and it’s no good."

President Trumps criticism echoes that of a highly critical 2018 report from the Pentagon, that emphasized that reliability of EMALS leaves much to be desired, and that the average rate of critical failures is nine times higher than the Navys threshold requirements.

In 2013, 201 of 1,967 test launches failed, more than 10 percent.

Factoring in the then-current state of the system, the most generous numbers available in 2013 showed that EMALS has an average “time between failure” rate of 1 in 240. In other words, one out of 240 launches fail.

According to a January 2014 report, "Based on expected reliability growth, the failure rate for the last reported Mean Cycles Between Critical Failure was five times higher than should have been expected. As of August 2014, the Navy has reported that over 3,017 launches have been conducted at the Lakehurst test site, but have not provided DOTandE with an update of failures. The Navy intends to provide DOTandE an update of failures in December 2014."

In the test configuration, EMALS could not launch fighter aircraft with external drop tanks mounted. "The Navy has developed fixes to correct these problems, but testing with manned aircraft to verify the fixes has been postponed to 2017".

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