Electromagnetic Aircraft Launch System
The Electromagnetic Aircraft Launch System (EMALS) is a type of electromagnetic 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 lead ship of the , 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 carrier's requirement of fresh water, thus reducing the demand for energy-intensive desalination. 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% 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% useful work), and hard to control. These control problems allow steam-powered catapults to launch heavy aircraft, but not aircraft as light as many unmanned aerial vehicles. A system somewhat similar to EMALS, Westinghouse's electropult, was developed in 1946 but not deployed. The EMALS uses a linear induction motor (LIM), which uses alternating current (AC) 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.
