During the 1920s, a new threat to naval forces was demonstrated by the destruction of a battle ship from the air and amply proved the vulnerability of ships from air attack. The early air defence (AD) weapons were guns of varying calibres with limited ranges. Without the development of radars and other electro sensors, the battle space was limited up to the visual horizon which was about 24 km. Ships depended upon visual sighting, voice communications and ships were responsible for their own AD. During World War II, precision aerial bombing and torpedo attacks became more effective and posed a serious threat to the naval fleet. The advent of aerial search radar dramatically improved the AD environment. Carrier-based fighters now had more reaction time and thus could be timely launched to counter enemy air. The Japanese kamikaze attacks of 1944 caused a lot of destruction to the US Fleet and were the first truly guided missiles. This resulted in ships forming tightly grouped formations and deploying picket ships for early warning. This resulted in the concept of integrated air defence in depth. The AD system still suffered from poor communications, negligible available of target data, visual transmission, lack of gap free surveillance systems, analogue computers and long range guided missiles. This was compounded by the fact that air defence was to be provided from a moving platform which also had limited space.

The US Navy as usual led the technical evolution by incorporating surface-to-air missiles (SAMs) in the design stage of new classes of cruisers and destroyers by 1957. With the development in electronic sensors, deployment of 3–T SAMS and shift to carrier-based fighter jets, significantly improved AD capabilities and expanded the battle space to over 160 km. The AD tried to keep pace with advancements in air power. With the evolution of better sensors and weapons, targets could now be engaged far beyond the visual horizon. New command, control and coordination systems were required for naval AD forces. However, integration between the command and control, sensors and weapons was still lacking, resulting in long reaction times.

To overcome this integration gap, US Navy introduced the navy tactical data system (NTDS) in 1958, which is considered to be the world’s first shipboard tactical data system based on programmable computers. NTDS provided target location and identification, gathered from multiple sensors— a sort of data fusion. This information could be exchanged with other similar systems. AD tactics continued to evolve as AD systems embedded on ships became more effective. The AD emerged as a centralised control/decentralised execution systems. It was now possible to provide area AD from forces at sea or near land. This was the cold war era and the Soviets began deployment of a series of air and surface launched cruise missiles in the 1960s. This was followed by Badger C and Bear B/C long-range bombers equipped to fire supersonic, nuclearcapable AS–2 Kipper and AS–3 Kangaroo air to-surface missiles from ranges in excess of 160km. To counter this threat, US developed digital and other electronic technologies that affected almost every aspect of sensor, weapon and launcher design. 3–T missile moved into a dual-track Standard missile (SM) programme. Tartar became SM–1 (MR or medium range) and Terrier became SM–1 (ER or extended range). Responding to the threat of cruise missiles, SM had an improved autopilot, proximity fuze, longer range, better electronic countermeasures (ECM) and inertial navigation. In 1964, the airborne version of NTDS in the form of Northrop Grumman’s E–2A Hawkeye airborne early warning aircraft joined the fleet. It could perform all actions what the NTDS could do but with extended surveillance ranges which were beyond the ships radar horizon. Thus the carrier-based fighters and long-range SAMs became the first line of air defence. The US Navy also realised that with the extended air defence envelope over land, they could also support land forces in selected situations.

Theatre AD evolved during the Vietnam war which included AD tactics, fleet AD identification zone standing operating procedures to control the dense air surveillance and identification environment over the Gulf of Tonkin. Later on this helped in evolving procedures for the Gulf conflict. They were of a great help while conducting AD operations to track, identify, and safely transit thousands of flights over land and water. The aim was to have zero friendly casualties. Emergence of high speed sea skimming cruise missiles posed a great danger to the fleet. To counter this threat, US Navy started the development of Aegis shipboard weapon system in 1973. Five performance factors were used to evaluate its capabilities: reaction time, firepower, electronic countermeasures (ECMs) and environmental resistance, continuous availability, and gap free coverage. Aegis was introduced operationally in 1983. The centre of Lockheed Martin’s Aegis was the SPY–1 phased array radar, which provided automatic detection and fire control quality tracking for hundreds of targets simultaneously. Since APY-1 also guided the SM in flight thus a separate fire control radar was not required. The system also increased manifold in the number of simultaneous engagements. There have been three other recent developments in the US which has had a great impact on theatre AD. They are Cooperative Engagement Capability, Joint Tactical Information Distribution System and the proliferation of Tactical Ballistic Missiles.

Cooperative Engagement Capability (CEC). CES is a computer-based information exchange system that allows multiple cooperating units including ships, aircraft, and ground forces, to view the same tactical picture. Surface and aerial naval platforms thus share raw radar data at near real-time exchange rates. Cooperative engagement is the result of tactical computer networking based on major technological advancements in high speed computer processing and communications. Such a system would dramatically speed up operations and reduce reaction time which is a key element in AD operations. CEC-equipped forces can engage hostile targets which are not seen on their sensors. In the future, CEC will form a key pillar of the Naval Integrated Fire Control-Counter Air (NIFC-CA) capability, which will allow stealthy sensor platforms such as the F-35C Lightning II to act as forward observers and pass their information through the Northrop Grumman’s E-2D Advanced Hawkeye to less stealthy platforms such as Boeing F/A-18E/F Super Hornet.

Tactical Information Distribution System (JTIDS). JTIDS has been fielded by US for all its defence forces and is a high speed, secure, jam-resistant, voice and tactical data communications system over Link-16. It provides users with real-time position, status, special purpose and identification information on friendly, unknown and hostile tracks. JTIDS is the joint surveillance, warning, and command and control coordination network which is current and also for the future. Presently it is being developed and made by Data Link Solutions, a joint venture of BAE/Rockwell Collins company.

Tactical Ballistic Missiles (TBMs). Widespread proliferation of TBMs is one of the most challenging air defence threats. During the Gulf War, the tactical and strategic effect of TBMs clearly emerged and defence against anti-ship cruise missile became of paramount importance. To counter this threat, the US Navy is further building on SM and the Aegis weapon system. With counter TBM threat in place, ships at sea will enable own forces to enter and operate in a hostile battlefield.

The combination CEC, JTIDS and varying ranges of SAMs provide an effective Fleet AD. It will be an important enabler for successful littoral operations.

Structure of Theatre Fleet AD

Generally all modern naval AD forces follow a layered defence in echelons, depending upon the range of weapons they possess. Such a system also provides depth to the air defence. This is necessary as ingredients of the air threat like UAVs, stealth fighters and TBMs are very dangerous platforms, capable of sneaking past into any AD system. The fourth echelon is ECMs which encompasses all the three layers. An example of Theatre Fleet AD based on three layers is given below. US follows this pattern.

First layer. This is also called point AD as it is based on short-range weapons and is the last arrow left in the quiver of Theatre AD. This includes close in weapon systems (CIWS) weapons including other ship board guns like 40mm L/70. One the popular CIWS is Raytheon’s Phalanx^® which is a rapid-fire, computer-controlled, radarguided gun system, designed to defeat anti-ship missiles and other close-in air and surface threats. It’s a land-based version is part of the US Army’s Counter Rocket, Artillery and Mortar systems. The radar of CIWS also provides early warning of air attacks.

Second layer. It consists of short-range SAMs which are have a <50 km range. Examples are Russian 9M330-Tor (range 12 km), Raytheon’s Sea Sparrow (range 19 km), MBDA Aster 15 (more than 30 km), and MBDA Sea Wolf (range 10 km). The vertical launched missiles have an advantage of occupying less space which is critical for ship board systems.

Third layer. This is quintessential theatre SAM AD with a range between 300 and 400 km. Examples are Raytheon’s Standard Missile VI is a key component in the US Navy’s Naval Integrated Fire Control – Counter Air (NIFC-CA), Russian systems are 48N6 (range 250 km, 40N6 (range 400 km) and MBDA Aster 30 (range more than 100 km).

ECCM. An important function of all AD systems is ECM which includes jamming of radar seeker heads and the use of chaff and decoys to miss- guide the missile from the target.

AD Management Systems. As brought out earlier all the above layers are integrated with an effective battle management system.

Indian Perspective

The Indian Navy (IN) ships have suitable AD guns and missiles which are more akin to point defence but future plans are to equip the Indian Navy with longer range missiles. Details are given in succeeding paragraphs.

AK-630. It is of Russian origin and is a fully automatic naval CIWS based on a six-barreled 30mm Gatling gun. The guns primary role is defence against anti-ship missiles and other precision guided weapons but it can also be employed against fixed- or rotary-wing aircraft, ships and other small craft, coastal targets, and floating mines. It has a range of 4 km.

Kashtan. Kashtan is a modern CIWS naval air defence gun-missile system deployed by the Russian Navy. Generally it is deployed as a combined gun and missile system to provide defence against anti-ship missiles, anti-radar missiles and guided bombs. The system can also be employed against fixed- or rotary-wing aircraft or surface vessels or targets on shore. Range is from 500 to 8,000 m.

Shtil-1. Shtil is a ship-based derivative of the proven Buk-M1 SAM system. It is a medium-range SAM system designed to engage multiple targets simultaneously. It can engage supersonic aircraft and antiship missiles flying at a maximum speed of Mach 2.5 and has a range more than 40 km. Dolgoprudniy Scientific and Production Plant was the developing agency.

Barak 1. Rafael’s Barak 1 is a supersonic, vertically launched, short-range AD system, with an operational range of about 10 km.

Future Developments

Barak-NG. During 2007 India’s DRDO and Israel’s IAI had signed a joint venture development contract for the development of a next-generation of Barak SAM. It has been designated many names like Barak SAM, Barak 8, Barak NG (next-generation), longrange SAM (LRSAM) and medium-range SAM (MRSAM). It is to be employed by the Army, Navy and the Air Force. The Navy’s Barak-NG/LR-SAM project is aimed to give India’s naval defences a much longer reach, with the intention of eventually making it India’s primary naval SAM. It is planned to have a range of 60-70 km due to a dual-pulse solid rocket motor whose second ‘pulse’ fires as the missile approaches its target. This ensures that the missile isn’t just coasting in the final stages, giving it more than one chance at a fast, manoeuvring target. The missile’s most important feature is its active seeker. In December 2015 the Indian Navy successfully test-fired Barak-8 long range surface to air missile from INS Kolkata on the Western Seaboard. DRDO has also flight-tested successfully 3 MR-SAM systems at Integrated Test Range in Chandipur, Odisha during June 30–July 1, 2016. MR-SAM can detect incoming enemy aircraft at 100-km distance and destroy them at ranges up to 70 km.

Conclusion

The ability to quickly develop and maintain an accurate air surveillance picture, coordinate defence-in-depth with available AD resources and provide a highly lethal response have been critical to naval operations for over many decades. Theatre AD for the naval fleet is thus an essential element for survivability and one of fundamental missions of any navy. It evolved both technically and tactically following World War II to counter the threat to friendly forces posed by manned aircraft, anti-ship missiles, seaskimming cruise missiles and TBMs.