An electromagnetic catapult, also called EMALS ("electromagnetic aircraft launch system") after the specific US system, is a type of aircraft launching system. Currently, only the United States and China have successfully developed it, and it is installed on the ''Gerald R. Ford''-class aircraft carriers and the Chinese aircraft carrier ''Fujian''. The system launches carrier-based aircraft by means of a catapult employing a

linear induction motor A linear induction motor (LIM) is an alternating current (AC), asynchronous linear motor that works by the same general principles as other induction motors but is typically designed to directly produce motion in a straight line. Characteristica ...

rather than the conventional steam piston. The advantage of the electromagnetic catapult is that it is safer and more reliable because the acceleration process is more uniform and less damaging to the structure of the aircraft compared to the steam catapult. 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 for fresh water, thus reducing the demand for energy-intensive desalination.

History

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 at 99.5% of the time. However, several drawbacks. One group of Navy engineers wrote: "The foremost deficiency is that the catapult operates without

feedback control Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled c ...

. With no feedback, there often occurs large transients in tow forces 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 steam-powered catapults to launch heavy aircraft, but not aircraft as light as many

unmanned aerial vehicle An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without any human pilot, crew, or passengers on board. UAVs are a component of an unmanned aircraft system (UAS), which includes adding a ground-based controll ...

General Atomics General Atomics is an American energy and defense corporation headquartered in San Diego, California, specializing in research and technology development. This includes physics research in support of nuclear fission and nuclear fusion energy. Th ...

Electromagnetic Systems (GA-EMS) developed the first operational modern electromagnetic catapult, named Electromagnetic Aircraft Launch System (EMALS), for the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

. The system was installed on USS ''Gerald R. Ford'' aircraft carrier, replacing traditional

steam catapult An aircraft catapult is a device used to allow aircraft to take off from a very limited amount of space, such as the deck of a vessel, but can also be installed on land-based runways in rare cases. It is now most commonly used on aircraft carrier ...

s. This innovation eliminates the traditional requirement to generate and store steam, freeing up considerable area below deck. With the EMALS, ''Gerald R. Ford'' can accomplish 25% more aircraft launches per day than the ''Nimitz'' class and requires 25% fewer crew members. The EMALS uses a

(LIM), which uses

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

(AC) to generate magnetic fields that propel a carriage along a track to launch the aircraft. A system somewhat similar to EMALS, Westinghouse's ''electropult'', was developed in 1946 but not deployed. China developed an electromagnetic catapult system in the 2000s for aircraft carriers, but with a different technical approach. Chinese adopted a medium-voltage,

direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or eve ...

(DC) power transmission system, instead of the alternating current catapult system that United States developed.

Systems under development

The concept of a ground carriage is intended for civilian use and takes the idea of an electromagnetic aircraft launch system one step further, with the entire

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for takeoff or landing. For aircraft it is generally needed for both. It was also formerly called ''alighting gear'' by some manufacturers, such as the Glenn L. Martin ...

remaining on the

runway According to the International Civil Aviation Organization (ICAO), a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface (often asphalt, concre ...

for both

takeoff Takeoff is the phase of flight in which an aerospace vehicle leaves the ground and becomes airborne. For aircraft traveling vertically, this is known as liftoff. For aircraft that take off horizontally, this usually involves starting with a ...

and

landing Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing", "touchdown" or ...

China

Rear Admiral

Yin Zhuo Yin may refer to: *the dark force in the yin and yang from traditional Chinese philosophy and medicine * Yīn (surname) (), a Chinese surname *Yǐn (surname) (), a Chinese surname *Shang dynasty, also known as the Yin dynasty **Yinxu or Yin, the ...

of the

Chinese Navy The People's Liberation Army Navy (PLAN; ), also known as the People's Navy, Chinese Navy, or PLA Navy, is the maritime service branch of the People's Liberation Army. The PLAN traces its lineage to naval units fighting during the Chine ...

has said that China's next aircraft carrier will also have an electromagnetic aircraft launch system. Multiple prototypes have been spotted by the media in 2012, and aircraft capable of electromagnetic launching are undergoing testing at a Chinese Navy research facility. According to a report in July 2017, the construction of the

Type 003 aircraft carrier ''Fujian'' (18; ), named after Fujian province, is the first of the Type 003 class aircraft carrier (NATO/ OSD Fujian-class CV), and is currently fitting out. Built for the People's Liberation Army Navy (PLAN), ''Fujian'' was launched on 17 J ...

has been rescheduled in order to choose between a steam or electromagnetic catapult and the latest competition results shows that the electromagnetic launchers will be used in the Type 003 aircraft carrier. China's military chief claims a breakthrough in electromagnetic launch systems for aircraft carriers has been made, and will utilize such a system in the third aircraft carrier that China will build after Type 002. The launch system is powered by fossil fuel via generators and capacitors. The design on the Type 003 carrier is being led by Rear Admiral Ma Weiming. China's electromagnetic catapult has been installed on its third aircraft carrier, the aircraft carrier ''Fujian''.

Russia

Russia's

United Shipbuilding Corporation , romanized_name = , former_name = , type = State owned enterprise , traded_as = , industry = Shipbuilding, Defense industry , genre = , fate = , predecessor = , successor = , founded = , founder = , defunc ...

(USC) is developing new launch systems for warplanes based on aircraft carriers, USC President Alexei Rakhmanov told

TASS The Russian News Agency TASS (russian: Информацио́нное аге́нтство Росси́и ТАСС, translit=Informatsionnoye agentstvo Rossii, or Information agency of Russia), abbreviated TASS (russian: ТАСС, label=none) ...

on 4 July 2018.

United States

EMALS was designed for and into the . A proposal to retrofit it into carriers was rejected. John Schank said: "The biggest problems facing the ''Nimitz'' class are the limited electrical power generation capability and the upgrade-driven increase in ship weight and erosion of the center-of-gravity margin needed to maintain ship stability."

Ships with electromagnetic catapult

United States

Gerald R. Ford-class aircraft carrier (in service)

China

Chinese aircraft carrier Fujian ''Fujian'' (18; ), named after Fujian province, is the first of the Type 003 class aircraft carrier (NATO/ OSD Fujian-class CV), and is currently fitting out. Built for the People's Liberation Army Navy (PLAN), ''Fujian'' was launched on 17 ...

(outfitting)

Type 076 landing helicopter dock The Type 076 landing helicopter dock is a class of planned Chinese amphibious assault ship. Compared to the Type 075, the Type 076 is expected to have an electromagnetic aircraft catapult and arresting gear for operating fixed-wing aircraft, like ...

(planned) Type 004 aircraft carrier (planned)