An aircraft carrier is a floating airfield and has all the components which are required to store, maintain, fuel, arm, take off and land a fighter aircraft. Other aerial platforms like Airborne Early Warning Aircraft E-2D Advanced Hawkeye, helicopters, UAVs and rotary unmanned aerial vehicles can also operate from a suitably designed aircraft carrier. An aircraft carrier enables a naval force to project its power globally. Admiral Sir Mark Stanhope, former First Sea Lord and Chief of Naval Staff of the Royal Navy, has said that, “to put it simply, countries that aspire to strategic international influence have aircraft carriers”. Fixed wing aircraft flew in 1903 and the first flight from the deck of a US naval cruiser took place in 1910. This was followed by the development of seaplanes and seaplane tender support ships. The first designed aircraft carrier was by UK which began work on HMS Hermes in 1918 and which was commissioned in 1924. Japan began work on Hosho first purpose-built aircraft carrier in 1918 and commissioned it in December 1922. However they are costly to build, operate and maintain thus only a handful of countries have aircraft carriers or some version of it. An aircraft has to be heavily defended being a vulnerable strategic asset with part of the naval air fleet on board. Thus it is escorted and defended by destroyers, light cruisers and other powerful fast battle ships and has its own air defence which makes it strike the enemy in the most unlikely of places.

Aircraft carriers in the Second World War

Navies of US, UK and Japan had the maximum aircraft carriers during the Second World War. Each carrier of that period had over thousand sailors and upwards of 30 aircraft. The US Navy fielded 36 carriers, the Royal Navy 24, the French Navy had one obsolete carrier and the Imperial Japanese Navy about 23. The US navy used most of their carrier against the very powerful Japanese Navy in the Pacific that was arguably the most capable carrier force at the beginning of the war. The Allies lost 9 aircraft carriers during the war.

Size of an aircraft carrier

The fighter aircraft, interceptors and support aircraft are the main armament of a carrier. To put across simply, bigger the ship, bigger will be the hangar and flight deck which accommodates the air wing. Actual there is no direct relationship between the size of the carrier and the number of aircraft it can carry. The Chinese Navy’s aircraft carrier Liaoning displaces about sixtyfive thousand tons and carries twenty-six fixed-wing aircraft and twenty-four helicopters. USS George Washington, displaces a little more than one hundred thousand tons but can operate some eighty-five to ninety aircraft. US carriers have steam catapults which can launch heavier aircraft as compared to the ski jump. Heavier aircraft implies more fuel capacity and weapons thus improving their lethality and range. Larger carriers also allow the flexibility of a variety of mix of the aircraft, depending on the mission. On the other hand INS Vikramaditya has a displacement of 45,400 tons when loaded and can carry a maximum of 36 all type of aircrafts. However it is capable of carrying out the role for which it has been acquired. Thus size of an aircraft carrier should be tailor made for the role as a larger carrier escalates the cost astronomically.

Launching Systems

Deck is a mobile airfield, length of which will depend upon the distance required for the aircraft to take off. A longer deck means a bigger aircraft carrier which has its own problems. Thus there is always an endeavour to reduce the length of the deck. This can be done by Catapult Assisted Take- Off (CATO) or changing the direction of the thrust of the aircraft as in Vertical and/or Short Take-Off (V/STO). Details with pro and cons are given below:

• Catapult Assisted Take-Off But Arrested Recovery (CATOBAR). A steam-powered catapult provides the aircraft safe flying speed after which it uses its own power to fly. US employs this system. It is reported that China is trying to develop this system. This system is very costly as it requires complex machinery.
• Short take-off but arrested recovery (STOBAR). This depends on increasing the net lift on the aircraft. In this system the upward thrust is provided by a ski-jump located at the forward end of the flight deck. This is often combined with thrust vectoring by the aircraft.
• Short take-off vertical-landing (STOVL). STOVL on fixed wing aircraft is achieved by the use of thrust vectoring, which may also be combined with a ski-jump. Sea Harrier short take-off and vertical landing/vertical take-off and landing jet fighter, is an an example which India has employed for many decades. The Sea Harriers operated from INS Viraat for the last time on March 6, 2016. Use of STOVL enables aircraft to carry a larger payload as compared to VTOL but still requiring a short runway. Sea Harriers is technically a VTOL aircraft but are operated as STOVL aircraft for carrying additional fuel and armament. F-35B Lightning II has VTOL capability in test flights but is operationally STOVL.
• Vertical take-off and landing (VTOL). Aircraft are specifically designed for the purpose of using very high degrees of thrust vectoring. There are many examples of these including Sea Harrier, F-35B and Bell Boeing V-22 Osprey (tilt-rotor). Almost all carriers have arrested-recovery systems (AR, e.g. CATOBAR or STOBAR) to recover the aircraft. VTOL capable aircraft or helicopters can land without any assistance as they do not have to decelerate while landing.

Propulsion Systems

Nuclear. Nuclear marine propulsion can be provided to surface ships and submarines where the role envisaged is to provide almost unlimited and uninterrupted global reach without pause for refueling. It is a highly technical field with few nations having nuclear propulsion technology and is also costly. To explain in simple terms the nuclear plant provides heat for converting water into stream which powers the steam turbines and the turbo generators. This power is then used for propulsion through gear boxes. The plant is divided into two parts, one for the port and the other for the starboard side to cater for failure of one side. Sea water is pumped, desalinated and provided to generate steam. The heat is transferred through water to steam generators which have a temperature of about 250 to 300°C. As water vaporizes at 100°C at normal pressure, the system is pressurized to increase the boiling temperature of the water. This water is normally called feed water. US, Russian and British navies generally use steam turbine propulsion while France and China use turbines to generate electricity. The number of reactors vary depending upon the role like most of the US aircraft carriers have two reactors but USS Enterprise has eight. Charles de Gaulle of the French Navy also has two pressure water reactors. Nimitz class of US aircraft carriers like USS George H.W. Bush has two General Electric pressurised water reactors driving four turbines of 260,000hp (194MW) and four shafts. As a result of the use of nuclear power, these ships are capable of operating for over 20 years without refueling and the anticipated service life of over 50 years. They have a displacement of 101,600–106,300 tonnes.

Technology and cost comes in the way of late starters like India and China who want to design and construct their own aircraft carriers. Aircraft carrier aviation really does not depend that much on the carrier but the complex system of aviation operations which finally project power. US Navy has really a high standard in this field thus worth emulating.

Conventional. Turbines are normally used for propulsion and can be steam or gas. Aircraft carrier São Paulo of Brazil Navy carrier is powered by four Parsons steam turbines producing 126,000shp. Six Indret boilers provide steam for the main propulsion turbines. On-board power is generated by two turbo alternators and six 2,000kW diesel generators. It has a displacement of 32,000tonnes at full load. Cavour Aircraft carrier of the Italian Navy is a combination of gas turbine and gas (COGAG) propulsion. The four LM2500 gas turbines, developing 22,000kW each, are manufactured by FiatAvio of Turin under a licence agreement from General Electric (US). Aircraft carrier Giuseppe Garibaldi of the Italian Navy is powered by four FIAT-G. E LM 2500 gas turbines providing 82,000 hp and 6 × Diesel generators (9.360 KW) with a displacement is 13,850tonnes (loaded). INS Vikramditya has 8 turbo-pressurised boilers, 4 shafts, 4 geared steam turbines generating 180,000 horsepower (134,226 kW). It has a displacement of 45,400 tonnes( loaded).

Future Aircraft Carriers

The US Navy currently has the world’s largest fleet of nuclear powered aircraft carriers, comprised of the Nimitz class and the upcoming Gerald R. Ford class super carriers. Apart from the size of their aircraft carrier fleet, US also leads in aircraft carrier technology, thus the current/ future role, design and technology sets the trend for nations to emulate for constructing their own aircraft carriers. Many naval analysts in the US are carrying out a review of the employability of aircraft carriers in view of the threat of longer-range, precision-guided anti-ship missiles and next-generation of hypersonic attack weapons. In addition to the missile threat, the heavy cost factor, threat, role and mid air refueling providing extended ranges to fighter aircraft, are also factors which leverage a look at the aircraft carrier’s design and survivability. It is likely that the future carriers will be equipped with greater high – tech sensors, improved ship defences, greater speed and maneuverability to avoid enemy fire and the deck designed to take on more number of UAVs. The size could be smaller for better maneuverability with on board UAVs, extended range precision weapons and anti missile defences. Such carriers will be able to deliver carrier-based unmanned capability to the fleet. Keeping these factors in view, the Ford Class Carriers have the flexibility of design to adapt to the future extremely high-threat environments. They should also a higher sortie generation rate and automation to reduce the manpower. These threats could be from the Chinese and Russian Navies. Chinese-built DF-21D missile is specially designed as a carrier-killer which can destroy targets at more than 1440 km thus preventing aircraft carriers to operate close to the coast. The unmanned MQ-25 Stingray is planned as a Super Hornet-sized Carrier-Based Aerial-Refueling System which will increase the strike range of carrier based fighter aircraft. It will be also be to provide limited ISR and relay communication and have a smaller radar signature as compared existing manned refueling aircraft. Inputs have been requested from Boeing, General Atomics, Lockheed Martin and Northrop Grumman and RFP is likely to be issued in 2017.

Aircraft carriers are always operate in carrier groups and are well with defended armed cruisers and destroyers. Technologies of these ships including sensors and weapons will also have to keep with the future threat.

Launching System

Electromagnetic Aircraft Launch System (EMALS). is under development by General Atomics for the US Navy’s latest aircraft carriers, contract for which was given in 1999. The EMALS system is a multi-megawatt electric power system involving generators, energy storage, power conversion, a 100,000 hp electric motor, and an advanced technology closed loop control system with built in performance monitoring. It is planned to replace the current steam catapult being used on all US aircraft carriers. The Gerald R. Ford is designated to be the first carrier to use EMALS. The advantages of EMAL are reduction of manning workload, thermal signature, topside weight and installed volume. It will also increase the launch capability and will also be able to launch UAVs.

Weapon Systems

Electro Magnetic(EM) Railgun. The EM Railgun uses high-power EM energy instead of explosive chemical propellants to fire a projectile farther and faster than any current gun. When fully weaponized, a Railgun will deliver hypervelocity projectiles on targets, at ranges far exceeding any of the current naval guns. It will be able to effectively intercept air threats, particularly anti-ship cruise missiles.

Naval Integrated Fire Control – Counter Air system (NIF-CA). US Navy is developing ship-based defensive weapons, electronic warfare systems, lasers and technologies able to identify and destroy approaching anti-ship cruise missile from ranges beyond the horizon. Example of this is currently deployed NIFC-CA which combines ship-based radar and fire control systems with an aerial sensor and dualmode SM-6 missile, to track and destroy approaching threats from over -the-horizon.

Laser Weapons. Laser weapon systems (LaWs) are highly accurate and low cost. Damage to the target will depend upon the power of the laser and the time it spends on the target. The US Navy has already deployed 30-kilowatt LaWs onboard the USS Ponce which has been used in the Persian Gulf. The more powerful the laser, the less time it needs to spend destroying the target thus the US Navy is planning 150kilowatt LaWs.

Propulsion Systems

Queen Elizabeth (QE) class of Royal navy’s aircraft carriers have the latest in conventional technology. QE class aircraft carriers have a planned displacement of approximately 65,000 tonnes, which may go up to70,000 tonnes in the future. The QE-class aircraft carriers have an integrated Rolls-Royce electric propulsion system. Rolls-Royce pioneered the use of aero-derivative gas turbines in marine propulsion, primarily for naval vessels. The MT30 Gas turbines that will power the QE class aircraft carriers are the most powerful in-service gas turbines in the world. Designed for the 21century navies, the MT30 integrates the very latest in gas turbine technology and is derived from the highly successful Trent engine programme. The propulsion system has two Marine Trent MT30 36 MW (48,000 hp) gas turbine generator units and four Wärtsilä diesel generator sets (two 9 MW or 12,000 hp and two 11 MW or 15,000 hp sets). The Trents and diesels are the largest ever supplied to the Royal Navy and jointly they feed the low-voltage electrical systems as well as four GE Power Conversion’s 20 MW Advanced Induction Motor electric propulsion motors which drive the twin fixed-pitch propellers.

USS Ford needs lots of electrical power to support future systems like EMAL, EM Rail Gun, advanced arresting gear, dual band radar and laser weapons thus it has four 26-megawatt generators, bringing a total of 104 megawatts to the ship. USS Ford can manage all this as its propulsion system is nuclear based. All future aircraft carriers who are going to equipped with modern systems, will need lots of electrical power which has to be catered for at the design stage.

China’s aircraft carriers

China’s first aircraft carrier Liaoning was originally built as a “heavy aircraft-carrying cruiser” for the Soviet Navy. It was laid down as the Riga and renamed the Varyag in 1990. A Chinese travel agency purchased the unfinished hull in 1998 and three years later the ship was towed from the Ukraine to China, where it underwent extensive modernization of its hull, radar, and electronics systems. It was commissioned into the PLAN in September 2012 as a training ship and after two months PLAN conducted its first carrier-based takeoff and landings. Liaoning displaces roughly 60,000 tonnes and its air wing consists of 24 Shenyang J-15 multirole fighters. It is reported that China plans to finally have four aircraft carriers as it was disclosed that China had acquired four sets of aircraft carrier landing systems from Russia. True to its plan, launching ceremony of China’s second aircraft carrier was held at the Dalian Shipyard of the China Shipbuilding Industry Corporation on April 26, 2017. The second aircraft carrier is being indigenously designed and built by China. China started working on it in November, 2013. At present, the main hull of this aircraft carrier has been completed and the main system devices including power supply have been installed in place.

India’s Indigenous Aircraft Carrier Project 71

India decided to design and make its own aircraft carriers thus was born Indigenous Aircraft Carrier (IAC) Project71. INS Vikrant is the first ship of the Vikrant class of aircraft carriers being built by Cochin Shipyard. Its launching system is STOBAR with a ski-jump and displaces about 40,000 tonnes. It is designed to take on MiG-29K and Indian Tejas fighter aircraft. In addition it can carry 10 Kamov Ka-31 or Westland Sea King helicopters for anti submarine warfare. It is powered by four GE LM2500+ gas turbines on two shafts, generating over 80 megawatts (110,000 hp) of power. It was launched in 2013 and expected to be commissioned in 2018. Apart from INS Vikrant there are plans to build the second carrier Vishal with a displacement of 65,000 tonnes and CATOBAR launching system with EMAL from US Finally India plans to have three air craft carriers.

Indo US Joint Working Group on Aircraft Carrier Technology Cooperation

This group has been formed to assist India in the design and construction of modern aircraft carriers. Indian Navy’s Controller of Warship Production & Acquisition represents India and US is represented by Programme Executive Officer, Aircraft Carriers US Navy. The Group meets periodically in India and US for discussions on providing modern aircraft technology to India. The meetings are also attended by other members as required. Providing of EMAL under the FMS is very much on the cards.

Technology and cost comes in the way of late starters like India and China who want to design and construct their own aircraft carriers. Aircraft carrier aviation really does not depend that much on the carrier but the complex system of aviation operations which finally project power. US Navy has really a high standard in this field thus worth emulating.