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Monday, 26 September 2016

EMALS (Electro Magnetic Aircraft Launching System) – The Future Technology Part 1

Launching a new triweekly series " The Future Technology Series " . In the first part i will take you through an basic overview and operational details of the modern catapult system of the giant aircraft carriers.
 EMALS (Electro Magnetic Aircraft Launching System) – The Future Technology

INTRODUCTION-
As we all know an aircraft carrier holds a matter of prime importance for a navy. The aircraft carriers serves as the military base of a nation, they are used to project power in remote land, where it is really a difficult task to set up a land based military base. Only a few of the nations can afford and maintain such giant ships. They house several number of aircrafts and personals who works 24*7 round the year to protect the world against hostile forces. U.S.A, U.K., Brazil, India, France, Russia, Japan, China, Spain and a few other’s navies only have such lethal vessels.

USS Nimitz (world’s largest aircraft carrier) size comparison
(Courtsey: www.wikipedia.org)


 Today the U.S.A has a total of 19 aircraft carriers, out of which 10 are supercarriers, they have more than 100,000 tons of displacement and 9 are amphibious assault vessels which are small compared to the supercarriers and used to launch only helicopters and VTOL aircrafts.

Now when the carriers have to launch an aircraft the procedure is not simple as it involves in launching an aircraft from land based runaway, where the aircraft taxi to run away and simply increases its thrust and take off. In case of the aircraft carriers it’s really a complex process with use of steam catapults (Used by the U.S.A., France and Brazil). The use of catapult gives these navies an edge over the other navies because they can launch the aircraft with greater payloads which includes more armament and fuel which is a necessity in combat and recon operations. The basic physics tells us that to produce lift the aircraft carrier can sail towards the direction of wind and more is the airflow over the wing the less is the minimum take off speed for the aircraft. But practically every time it’s not possible and feasible. Day by day the increased payload involving in naval aircraft operations can’t be done without the help of a simple device i.e. CATAPULT.
THE CATAPULT-
The catapult is a device installed in the flight deck and is attached to gear (forward) of the aircraft to be launched consisting of a piston attached to a cylinder (which is really very large). To propel the catapult several methods can be used. During early 20th century when first aircraft carriers came they operated with the help of spring catapults. They were not really successful but fortunately man found a way to launch aircrafts from the ships for the first time. But as soon as the world war came the Research and Development towards improving and modernising took place, years of hard work and advancement of technologically resulted in the development of steam catapults.


Structure and working of steam catapult in aircraft carrier
(Courtsey: www.googleimages.com)


The basic principle of steam catapult is that the catapult is attached to the nose gear of the aircraft to be launched, the catapult being connected to the pistol which is further connected to the cylinder. There are 2 cylinders which are charged with steam and the piston is in compressed position. It is really very complex and time consuming process to charge the cylinders to appropriate level of required steam pressure. The aircrafts engines also run to  along with catapults and produces thrust. Behind the aircraft the jet blast deflector also known as blast fence is raised up with the help of hydraulics and they act as a safety device which redirects high energy coming from exhausts of the aircraft and thus saves from potential injury and damage to other structure and installations on board. The crew checks up if everything is right and the aircraft is ready to launch, the catapult officer who is responsible with all these tasks then releases the pistons, which were previously in holdback position. After they were released a very large amount of force now drives the aircraft along with the help of thrust produced by the aircraft itself and the aircraft finally takes off.


Position of catapult in an aircraft carrier
(Courtsey: www.quora.com)

But operating the steam catapult involves lot of fresh water which is obtained by desalination of sea water. Lot of maintenance is also required to keep them operating even during adverse conditions to keep them operating. Not only this they significantly affect the cost during construction and maintenance. Significant time is also required to recharge them with steam. One of major adversary faced by the aircrafts are lot of stress in its airframe, the solution to all these problem is solved by the development of the “EMALS System”

The Revolutionary Solution -EMALS System
But with the changing time and the development it was felt to replace the catapult with the EMALS system. Years of research by the U.S.A. and developed by the American company “General Atomics” the EMALS system is now ready to be launched along with the new generation of lethal aircraft carriers USS Gerald R. Ford, which will replace the USS Enterprise after 51 years of her decorated service. This aircraft carrier unlike the conventional aircraft carriers is equipped with EMALS or Electro Magnetic Aircraft Launching System. The EMALS system launches the aircraft using a linear motor drive rather than the conventional Steam Catapult piston-cylinder drive.
Computer Generated 3-D structure of linear induction motor in EMALS
(Courtsey: www.wikipedia.org)

WORKING OF EMALS System-
The electromagnetic aircraft launching system consists of the catapult attached to a very high electrically driven linear induction motor. The induction motor is made of two 300-foot-long stationary beams, or stators, spaced a couple of inches apart and a 20-foot-long carriage, that is sandwiched between the two beams and can slide back and forth along their lengths.
The beams are made up of lot of segment . Along the spaces of the beams there lies the wiring which helps to run the whole system and is one of the prominent component of EMALS. The computer system programmed onboard the vessel selectively switches on the segments of the beam which generates an electromagnetic force along the carriage (catapult) . Thus Magnetic effect is the principle of operation for this system.
The aircraft launching takes place in the same manner as in the steam catapult after that. Only the difference is that 0 amount of steam is used and all is magnetically driven modern generation system.


EMALS system in the USS GERALD R. FORD
(Courtsey: USA Department Of Defence)

Advantages of EMALS System
Research studies shows that the EMALS system is much better and efficient due to the following reasons, which are as follows-
1.       EMALS system are much more lighter compared to the steam catapult systems, this helps the aircraft carrier to be loaded with other important stuffs required during its sailing period.
2.       As it occupies less space also this will help in creating room for the serving personals and aircrafts stationed in the carrier.
3.       Studies shown that they have 5% more operating efficiency compared to the steam catapult systems and delivers can supply with 121 mega joules of force which is 29% more than the older steam catapult’s 95 mega joules of force only.
4.       Less manpower, maintenance is required to operate the EMALS.
5.        The future ships planned by the US, Indian and Chinese navy will be equipped with this technology and thus will be more electrical ships rather than the current ones, as the EMALS system requires a large amount of electric power to operate. Overall it will improve the ship, because the replacement of the steam catapults will help to free a significant space and will create room for energy efficient vessels.
6.       They will prove to very helpful to launch the future aircrafts which are heavier compared to current ones and will be having more payload compared to the current ones.
7.       An electromagnetic catapult can launch an aircraft every 45 seconds.



Testing of the EMALS system using a dummy model for the first time
(Courtsey: US Depatment Of Defence)


No doubt the EMALS systems uses a huge amount of power, to solve this problem the ships will be fitted with high powered rotors, during the operation the system will draw power from the stored systems and the generators too, thus the dual system power supply will help it. There will be large power drop on board the ship but the during the interval of 42 seconds of launching another aircraft , there will be complete recovery of power.
Thanks
Ayonavo Biswas
                                                                                                                                        


  

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