Electromagnetic Aircraft Launch System

The Electromagnetic Aircraft Launch System (EMALS) is a system under development by the United States Navy to launch carrier-based aircraft from an aircraft catapult using a linear motor drive instead of the conventional steam piston drive. The main advantage is that this system allows for a more graded acceleration, inducing less stress on the aircraft's airframe.

Other advantages include lower system weight, with a projected lower cost and decreased maintenance requirements. The design includes the ability to launch aircraft that are heavier or lighter than the conventional system can accommodate. In addition, the system requires far less fresh water, reducing the need for energy-intensive desalination.

Steam catapults were developed in the 1950s and have been exceptionally reliable. For over 50 years, at least one of the four catapults has been able to launch an aircraft 99.5% 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 steam-powered catapults to launch heavy aircraft, but not aircraft as light as many UAVs, which is an unacceptable limit for a 21st-century platform.

The EMALS is being developed by General Atomics for the U.S. Navy's newest aircraft carriers. A somewhat similar system, Westinghouse's electropult, had been 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 that have the function of a conventional motor’s armature. 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).

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