Electromagnetic Aircraft Launch System

A drawing of the linear induction motor used in the EMALS.

The Electromagnetic Aircraft Launch System (EMALS) is a type of aircraft launching system currently under development 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 developed for the Navy's Gerald R. Ford-class aircraft carriers.

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.

China is reportedly developing a similar system.[1]

Design and development

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.[2] 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."[3] The steam system is massive, inefficient (4–6%),[4] 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, Westinghouse's electropult, was developed in 1946 but not deployed.[5]

Linear induction motor

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.[6] The EMALS consists of four main elements:[7] 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).[6]

Energy storage subsystem

During a launch, the induction motor requires a large surge of electric power that exceeds what the ship's own continuous power source can provide. As of 1994, 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.[8] 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.[6] A max launch using 121 MJ of energy from each disk alternator slows the rotors from 6400 rpm to 5205 rpm.[8][9]

Power conversion subsystem

During launch, the power conversion subsystem releases the stored energy from the disk alternators using a cycloconverter.[6] 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.[8]

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 launch stresses on the plane’s airframe.[6]

Program status

The Electromagnetic Aircraft Launch System at Naval Air Systems Command, Lakehurst, launching a United States Navy F/A-18E Super Hornet during a test on 18 December 2010

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.[10]

ACT Phase 2 began on 25 June 2013 and concluded on 6 April 2014 after a further 310 launches (including launches of the EA-18G Growler and 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.[10]

  • June 2014: The Navy completed EMALS prototype testing of 450 manned aircraft launches involving every fixed-wing carrier-borne aircraft type in the USN inventory at Joint Base McGuire–Dix–Lakehurst during two Aircraft Compatibility Testing (ACT) campaigns.
  • May 2015: First full speed shipboard tests conducted.[18]

Delivery and deployment

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.[19]

Advantages

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.[8] EMALS uses no steam, which makes it suitable for the Navy's planned all-electric ships.[20]

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.[20] 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 catapult's approximately 95 MJ.[8] The EMALS, with their planned 90% power conversion efficiency, will also be more efficient than steam catapults, which achieve only a 5% efficiency.[6]

Criticisms

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."[21][22][23][24]

Reliability

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.[25]

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 DOT&E with an update of failures. The Navy intends to provide DOT&E an update of failures in December 2014."[26]

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".[27]

In July 2017 the system was successfully tested at sea on the USS Gerald R. Ford.

Systems that use or will use electromagnetic aircraft launch systems

China

Rear Admiral Yin Zhuo of the People's Liberation Army Navy has said that China's next aircraft carrier will also have an electromagnetic aircraft launch system.[28] 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.[29][30]

According to a report in July 2017, the construction of the Type 002 aircraft carrier 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 002 aircraft carrier.[31][32]

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 001A. The launch system is conventionally powered through capacitance, thus eliminating the need to rely on the nuclear reactor for its power supply.[33][34][35]

India

The Indian Navy has shown an interest in installing EMALS for its planned CATOBAR supercarrier INS Vishal.[36][37][38][38] The Indian government has shown interest in producing the Electromagnetic Aircraft Launch System locally with the assistance of General Atomics.[39]

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 remaining on the runway for both takeoff and landing.[40]

Russia

Russia’s United Shipbuilding Corporation (USC) is developing new launch systems for warplanes based on aircraft carriers, USC President Alexei Rakhmanov told TASS on 4 July 2018.[41]

United Kingdom

Converteam UK were working on an electro-magnetic catapult (EMCAT) system for the Queen Elizabeth-class aircraft carrier.[42] 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 takeoff and landing aircraft using the UK-designed non-steam EMCAT catapults.[43][44]

In October 2010, the UK Government announced it would buy the F-35C, using a then-undecided CATOBAR system. A contract was signed in December 2011 with General Atomics of San Diego to develop EMALS for the Queen Elizabeth-class carriers.[42][45] 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.[46]

United States

EMALS was designed for and into the Gerald R. Ford-class aircraft carrier.[47] A proposal to retrofit it into Nimitz-class 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."[48]

See also

References

  1. ↑ "An Electromagnetic Arms Race Has Begun: China Is Making Railguns Too". Popluar Science. 23 November 2015.
  2. ↑ Schank, John. Modernizing the U.S. Aircraft Carrier Fleet, p. 80.
  3. ↑ Doyle, Michael, Douglas Samuel, Thomas Conway, and Robert Klimowski. "Electromagnetic Aircraft Launch System - EMALS". Naval Air Engineering Station Lakehurst. 1 March. p. 1.
  4. ↑ Doyle, Michael, "Electromagnetic Aircraft Launch System - EMALS". p. 1.
  5. ↑ Excell, Jon. "October 1946 – Westinghouse unveils the Electropult". The Engineer. Retrieved 2017-06-30.
  6. 1 2 3 4 5 6 Schweber, Bill (2002-04-11). "How It Works" (PDF). EDN Magazine. Retrieved 2014-11-07.
  7. ↑ "Archived copy". Archived from the original on 10 February 2009. Retrieved 29 February 2008.
  8. 1 2 3 4 5 Doyle, Samuel & Conway, Klimowski (1994-04-15). "Electromagnetic Aircraft Launch System – EMALS" (PDF). Archived from the original (PDF) on 2004-10-25. Doyle, Samuel & Conway, Klimowski. "Electromagnetic Aircraft Launch System – EMALS" (PDF).
  9. ↑ Bender, Donald (May 2015). "Flywheels" (PDF). Sandia Report (SAND2015–3976): 21.
  10. 1 2 "Archived copy". Archived from the original on 28 October 2014. Retrieved 1 April 2015.
  11. ↑ "EMALS launches first Goshawk - NAVAIR - U.S. Navy Naval Air Systems Command - Navy and Marine Corps Aviation Research, Development, Acquisition, Test and Evaluation". Navair.navy.mil.
  12. ↑ "Photo release: EMALS successfully launches first Greyhound - NAVAIR - U.S. Navy Naval Air Systems Command - Navy and Marine Corps Aviation Research, Development, Acquisition, Test and Evaluation". Navair.navy.mil.
  13. ↑ "NAVAIR - U.S. Navy Naval Air Systems Command - Navy and Marine Corps Aviation Research, Development, Acquisition, Test and Evaluation". Navair.navy.mil.
  14. ↑ "USN undertakes first EMALS Hornet launch". Air Forces Monthly. No. 275. Key Publishing Ltd. March 2011. p. 18. ISSN 0955-7091.
  15. ↑ "Navy's new electromagnetic catapult 'real smooth'". Newbury Park Press. 28 September 2011. Retrieved 2011-10-04.
  16. ↑ "New carrier launch system tested". Security Industry. UPI. 3 October 2011. Retrieved 2011-10-04.
  17. ↑ "F-35C launches from emals".
  18. ↑ "Navy Announces Successful Test of Electromagnetic Catapult on CVN 78". Imperialvalleynews.com. PEO Carriers. 15 May 2015. Retrieved 16 May 2015.
  19. ↑ "Local man pilots first plane to land on U.S.S. Gerald Ford". Fox 8 Cleveland. 29 July 2017. Retrieved 2 August 2017.
  20. 1 2 Lowe, Christian. "Defense Tech: EMALS: Next Gen Catapult". Retrieved 2008-02-27.
  21. ↑ "Read Donald Trump's Interview With TIME on Being President". Time. Retrieved 2017-05-11.
  22. ↑ Times, Navy. "Navy should return to 'goddamned steam' on carrier, Trump says". Navy Times. Retrieved 26 June 2017.
  23. ↑ "'You have to be Albert Einstein to figure it out': Trump targets the Navy's new aircraft catapult". Washington Post. Retrieved 26 June 2017.
  24. ↑ "General Atomics mum on Trump's 'goddamned steam' criticism of new carrier catapult". The San Diego Union-Tribune. Retrieved 2017-06-30.
  25. ↑ "Director, Operational Test and Evaluation : FY 2013 Annual Report" (PDF). Dote.osd.mil. Retrieved 2017-06-30.
  26. ↑ Tyler Rogoway. "The Pentagon's 'Concurrency Myth' Is Now Available In Supercarrier Size". Foxtrotalpha.jalopnik.com. Retrieved 2017-06-30.
  27. ↑ O'Rourker, Ronald (May 18, 2017). "Navy Ford (CVN-78) Class Aircraft Carrier Program: Background and Issues for Congress" (PDF). Washington, D.C.: Congressional Research Service.
  28. ↑ "Chinese aircraft carrier should narrow the gap with its U.S. counterpart". english.peopledaily.com.cn. People's Daily. 18 October 2013. Retrieved 18 October 2013.
  29. ↑ "实验室中的中国电磁弹射器!高清图震撼人心! - 海军论坛 - 铁血社区". Bbs.tiexue.net (in Chinese). Retrieved 2017-06-30.
  30. ↑ "简氏:中国试飞改进型歼-15 或用于测试电磁弹射器_《参考消息》官方网站". Cankaoxiaoxi.com (in Chinese). Retrieved 2017-06-30.
  31. ↑ "China's Third Aircraft Carrier will be First to use Steam Catapults to Launch Aircraft". yibada. 12 Feb 2017.
  32. ↑ "China Explores Electromagnetic Carrier Launch System". AIN online. 6 July 2017.
  33. ↑ "Breakthrough to power most advanced jet launch system on China's second home-grown aircraft carrier". SCMP. 1 November 2017.
  34. ↑ "China's New Aircraft Carrier to Use Advanced Jet Launch System". The Diplomat. 1 November 2017.
  35. ↑ "China claims to have developed conventionally powered electromagnetic catapult". Jane's 360. 2 November 2017. Archived from the original on 11 November 2017. Retrieved 16 November 2017.
  36. ↑ "Indian Navy seeks EMALS system for second Vikrant-class aircraft carrier". Naval Technology. Retrieved 2017-06-30.
  37. ↑ "India plans a 65,000-tonne warship". The New Indian Express. 2012-08-06. Retrieved 2017-06-30.
  38. 1 2 Ankit Panda, The Diplomat. "This US Technology Could Give Indian Aircraft Carriers an Important Edge". The Diplomat. Retrieved 2017-06-30.
  39. ↑ defence secretary to visit India in May to push aircraft carrier technologies, The Times of India, 5 April 2015
  40. ↑ Rohacs, Daniel; Voskuijl, Mark; Rohacs, Jozsef; Schoustra, Rommert-Jan (2013). "Preliminary evaluation of the environmental impact related to aircraft take-off and landings supported with ground based (MAGLEV) power". Journal of Aerospace Operations (2): 161.
  41. ↑ "Russia developing new launch catapults for aircraft carriers". TASS. 4 July 2018. Retrieved 14 July 2018.
  42. 1 2 "Converteam develops catapult launch system for UK carriers" By Tim Fish, Jane's. 26 July 2010
  43. ↑ "Britain rethinks jump jet order". UPI.com. 12 August 2009. Retrieved 14 August 2009.
  44. ↑ Harding, Thomas (12 August 2009). "Defence jobs at risk". London: Telegraph.co. Retrieved 14 August 2009.
  45. ↑ "News Channel - Homepage - flightglobal.com". Flightglobal.com.
  46. ↑ "It's Official: UK to Fly F-35B JSFs". Defensetech.org. Retrieved 19 July 2012.
  47. ↑ "Archived copy". Archived from the original on 28 September 2012. Retrieved 11 September 2018.
  48. ↑ Schank, John. Modernizing the U.S. Aircraft Carrier Fleet: Accelerating CVN 21 Production Versus Mid-Life Refueling. Santa Monica: Rand Corporation, 2005. p. 76.

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