Sunday, March 8, 2015

EMALS- Electro Magnetic Aircraft Launcing System

 An Excellent Represenation of EMAL launch

EMAL is the USS Gerald R Ford Aircraft Carrier

      With the new government keen on developing the relationship of India with the global power USA has help forge several hundred deals. The governments have adopted the new motto --- "Chalein Saath Saath: Forward Together We Go". The governments have stressed on bilateral ties in trade, commerce, banking, industries and military systems.

      The US-India military forces and command believes in freedom, democracy, and government by rule of law, and to increase security trough out the globe. These interests also include maintaining security and stability, defeating violent religious extremism and terrorism, preventing the spread of weapons of mass destruction and associated materials, data, and technologies, and protecting the free flow of commerce throughout the globe prospering every country.

         When the President of United States of America visited India many defence projects were cleared for co-produced. Defence Trade and Technology Initiative (DTTI) that was initiated in 2012, under which the US and India would work on co-development and co-manufacturing projects has been given renewed interest. Four "pathfinder projects" were identified during Obama's visit the four products to be co-produced are the Raven mini unmanned aerial vehicles (UAVs), "roll-on, roll-off" intelligence-gathering and reconnaissance modules for C-130J Super Hercules aircraft, mobile electric hybrid power sources, and chemical-biological warfare protection gear for soldiers.

A heavy E 2D Launch by EMAL , just a 50 mts enough

With US Navy unable to check the movement of Chinese ships has requested Indian Navy to join the efforts and has asked to stand out openly in the South China issue. Indian Navy has received substantially from the US counterpart. With India raring to be a ‘blue water’ force has been very keen on operating at least a “ three CBG (Carrier Battle Group) “ with one serving on the western and the other on the eastern water fronts. And another in docks for maintenance.  India has had experience with the CBG’s and has operated a two front CBG. The carriers operated by the Navy are of STOBAR (Short Take Off But Arrested Recovery) configuration. But with a STOBAR configuration launching heavier aircrafts could not be achieved. It is crucial to operate reconnaissance missions but this requires the ability to launch heavier aircrafts and this in turn requires using the CATOBAR (Catapult Assisted Take-Off But Arrested Recovery). Under the IAC (Indigenous Aircraft Carrier) plans the IAC-I was configured with a STOBAR launch system and the IAC-II is being planned to be configured with the CATOBAR systems. With CATOBAR systems being very hard to maintain the Navy has went with the latest EMALS system to assist launching heavier aircrafts off the carriers.

The Electromagnetic Aircraft Launch System (EMALS) is a system being developed by General Atomics for the United States Navy to be fitted on the newest Gerald R. Ford-class aircraft carriers. This system would effectively replace the old steam propelled catapult aircraft launch system on the old carriers. EMALS is a highly sophisticated system that is being fitted out on the Gerald class carriers. The system has passed all initial tests and the first land based prototype passed testing by June 2010. The current steam catapults being used in the CATOBAR system require about 615 kg/ 1,350 pounds of steam for each aircraft launch, and this steam in return produced from the nuclear reactor. To propel the catapult forward huge amount of hydraulics and steam is essential. Generation of this steam is an extremely demanding procedure and requires high amount of purified water be piped through the nuclear reactor. This involves very high maintenance. EMALS being a electric driven launch system has many advantages and mainly is a system that requires extremely less maintenance.

The EMALS is based on generation and utilization of electric current rather than the old practice of using steam.  The whole system works on the principle of Electromagnetic induction. 

The Projectile is anything a Launch system or a Bullet too

The major components of EMALS are –

  • Linear induction motor
  • Energy storage subsystem
  • Power conversion subsystem
  • Control Consoles

Program status

Linear induction motor                                                                                                

    Linear Induction motor is a motor that is used to achieve rectilinear motion rather than the traditional circular motors that is generated using a common electric motor.  A linear electric motor typically consists of a flat magnetic core with transverse slots which are often cut straight and with coils laid into slots, each phase gives an alternating polarity and so that the different phases physically overlap each other. In an induction motor the force is produced by linearly moving magnetic field acting on conductors in the field. Any conductor be it a loop, a coil or simply a piece of plate metal, that is placed in this field will have eddy currents induced in it thus creating an opposing magnetic field, in accordance with Lenz's law.

   When energized, the motor accelerates the carriage down the track and the carriage in turn takes the aircraft along and propels it off the deck. With the charge being inducted into the motor only the section of the coils surrounding the carriage is energized. With only the coils being energised the reactive losses is minimised to a very great extent. With the LIM EMALS can accelerate an aircraft of around 45000 kgs to about 240 km/h.

Energy storage subsystem

        To propel the carriage at the speed required the induction motor requires very large amount of electric power. The current required to attain this speed required production of current which is actually more than the power that can be obtained from the ship's own power source. The EMALS is therefore put with a energy-storage subsystem which draws power from the ship’s main power source and stores the procured energy kinetically on rotors armed with four disk alternators. This energy is then stored and the alternators running and the process repeats till the need for an aircrafts launch is felt. When the systems are activated for the launch of an aircraft the system releases the stored energy in a very short period of time as against the time required for production of steam in the traditional stem propelled catapults. Each rotor can easily store more than 100 mega joules of energy. To reduce the time betweens launch of each aircraft it the system has been configured to be recharged within 45 seconds of a launch which is way faster than steam catapults.

Power conversion subsystem

       With the energy produced with the help of the linear induction motor the produced energy is stored in Energy storage subsystem. After the energy is stored it is crucial for the same energy to be released when a launch is required. The basic function of the power conversion subsystem is to release the stored energy in the energy storage subsystems during launch; this is brought about by using a cycloconverter. A cycloconverter is used to covert a constant voltage, constant frequency AC waveform to another AC waveform of a lower frequency by synthesizing the output waveform from segments of the AC supply without an intermediate DC link. 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.

Control consoles

      It is crucial for the EMALS to be controlled and monitored constantly and it is also crucial to maintain a constant voltage for the LIM and to look make sure the launch of the aircrafts will be a uninterrupted process. This whole process is brought about by control units which are responsible for control through closed loop structure. And this in turn allows the operators to maintain a constant tow force that reduces the stress on a aircrafts airframe to a large extent.

         The IAC-II is in advanced stage of planning and is rumoured to be propelled by nuclear fuel. Also the carrier is being rumoured to be around 65000 tonnes which makes the IAC-II the heaviest Indian build ship. The main focus of a CBG is to extend the reach of the countries forces. But India has never been in the global race for projecting a control regime environment. Even after the carrier is inducted it’s area of operation may only be around the IOR or the EEZ. If the CBG is charged with the safeguarding of EEZ then reconnaissance is going to be a important part of the CBG’s daily routine. This requires the launch of heavier aircrafts like the E-2D Hawk eye that is to be part of the carrier’s air wing. This means the navy has to opt for a CATOBAR configuration. But with the EMALS being a very newly introduced system it has to be seen if the Navy command goes with the EMALS or opts to the more proven ‘ steam propelled’ catapults to launch these aircrafts.

Article By Karthik Kakoor

No comments:

Post a Comment