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Naval Anti-Surface Warfare: From Gun to Missile

Posted on 01 June 2013

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Warships target other warships withmerchantmen as the secondary target, and theweapon options for what is now called Anti-Surface Warfare (ASuW) are surprisingly broad

 

Since the 1960s the prime weapon for ASuW has been the missile both in the air-to-surface version, first used with spectacular success to sink the battleship Roma in 1943, and the surface-to-surface version whose value was demonstrated by the Egyptian Navy’s stand-off sinking of the Israeli destroyer Eilat in 1967. The latter was achieved with a first generation weapon still much used in Asia, the Russian P-15 Termit, better known by the NATO designation SS-N-2 ‘Styx’.

In its original version ‘Styx’ continues to be used by India, North Korea and Vietnam while China has produced an improved version HY-2 (CSS-N-3 ‘Seersucker’). All are characterised by a large launch weight (2.5 tonne) with simple autopilot guidance augmented by active radar (HY-2 can use an infra-red seeker) powered by a rocket motor fuelled by kerosene and nitric acid with a sub-sonic speed (Mach 0.9). They have a maximum range of some 21.5-43 nautical miles (40-80 kilometres), although HY-2 can reach 51 nautical miles (95 kilometres), but it is a crude, relatively dumb weapon, with a powerful (454 kilogramme) warhead while its corrosive fuel system requires careful maintenance.

The ‘Styx’ family are essentially ship-launched weapons, in major surface combatants such as destroyers and frigates as well as smaller ones such as corvettes and fast attack craft, but the second-generation of weapons are more versatile and can be used from ships, aircraft and even submarines. The most famous are Harpoon, used by eight Asian navies, and Exocet used by six Asian navies, but they have similar sub-sonic speeds and are more sophisticated.

Guidance is based upon inertial navigation systems which receive inputs of launch platform co-ordinates and approximate target co-ordinates and then use accelerometer motion sensors and gyroscopic rotation sensors to provide data to a computer which continuously calculates the location, direction and velocity of the missile and compares own location with that of the target. Within proximity to the target the missile activates its own radar to detect it and to control the terminal phase, this sensor having the ability to guide the weapon into either the horizontal or the vertical centre of the radar image.

These missiles also have a degree of intelligence approaching their target indirectly, turning at a predetermined way point or even way points, and at varying heights depending upon whether or not the mission requirement is for fuel efficiency, to achieve greater range or a covert approach, flying just above the waves to make them more difficult for the target’s radars to detect. Alternatively, the missiles can be pre-set to dive upon the target at a steep angle for greater lethality.

Because they are designed to strike the most vulnerable part of a ship both Harpoon and Exocet have smaller warheads than ‘Styx’; 221 and 165 kilogrammes respectively. The turbo-jet powered Harpoon had the longer range, up to 130 nautical miles (240 kilometres) compared with 38 nautical miles (70 kilometres) in the rocket-powered Exocet MM40 but Exocet Block 3 has a turbo-jet engine giving a range of 97 nautical miles (180 kilometres) with greater accuracy thanks to the incorporation of a Global Positions System (GPS) unit using satellite navigation inputs. Similar weapons are MBDA’s Otomat Mk 2 used by Bangladesh and Malaysia, the Russian 3M24 Uran (Uranium) selected by India and Vietnam and China’s YJ-83 or CSS-N-6 ‘Saccade’ whose export version is designated C-802 with version used by Bangladesh, China, Indonesia, Myanmar, Pakistan and Thailand. Asian-produced weapons are Japan’s Mitsubishi Heavy Industries Type 90 (SSM-1B) and South Korea’s LIG Nex1 Haeseong (Sea Star) or SSM-700K as well as Taiwan’s Hsiung Feng II (Brave Wind II).

There is a growing Asian interest in supersonic anti-ship missiles which have the advantage of reducing a target’s reaction times; indeed they can halve the effective range of close-in weapon systems. But their very velocity is the problem, and the reason they are not more widely used for they have less time for their radar processors to evaluate information from the sensor and allow the guidance system to react. Indeed it has been suggested they may be more vulnerable to electronic counter-measures than sub-sonic weapons which have sufficient fuel to re-acquire lost targets.

India uses both the Russian 3M80/3M82 Moskit (Mosquito) or SS-N-22 ‘Sunburn’  and the PJ-10 Brahmos, jointly developed with the Russians, while China also uses ‘Sunburn’ but only in Russian-built Sovremenny class destroyers. ‘Sunburn’ is capable of Mach 3, has a range of 65 nautical miles (120 kilometres) and carries a 320 kilogramme warhead while Brahmos is a Mach 2.8 ramjet-powered weapon with a range of 160 nautical miles (290 kilometres). Air and submarine-launched versions are under development and recent tests indicate the weapon now has a manoeuvring approach capability while Russia and India have recently agreed to develop hypersonic BrahMos 2 missile capable of flying at speeds of Mach 5-Mach 7. Taiwan has developed a supersonic weapon, Hsiung Feng III  for the Cheng Kung (Oliver Hazard Perry) class frigates. It is reported to have a range of 110 nautical miles (200 kilometres) a speed of Mach 2 and a 190 kilogramme warhead.

Shorter range weapons are a major requirement for navies which operate in archipelagos and use fast attack craft both for patrol purposes to restrict similar, hostile, craft and also to combat amphibious warfare threats. Taiwan was the first Asian country to develop weapons to operate in this threat scenario producing Hsiung Feng I as a development of the Israeli Gavriel (Gabrial) II, a rocket propelled weapon also acquired by Sri Lanka. This has semi-active radar and manual guidance, a 225 kilogramme warhead and a range of 20

nautical miles (36 kilometres). Indonesia announced last year it plans to acquire a class of 24 fast attack craft from PT Palindo Marine which will receive Chinese designed C-705 with turbo-jet propulsion. Indonesia is the launch customer for these weapons which have a 110 kilogramme warhead. It is worth noting that helicopters embarked on surface combatants such as frigates are sometimes equipped with short-range anti-ship missiles, such as the MBDA Sea Skua used by the Republic of Korea Navy, and these are primarily for small, high-value, targets.

Compared with the missile the gun may seem an anachronism in ASuW yet it remains a useful tool, especially against smaller targets and merchantmen. Indeed large calibre weapons have been used to disperse and drive back formations of Fast Inshore Attack Craft in the Gulf. The advantages of the gun are faster reaction times than any missile and greater versatility because it can also be used in the Naval Gun Support (NGS) to provide fire support for troops ashore and it also has an Anti-Air Warfare role, although this is limited especially in larger calibre weapons.

The most common larger calibre weapons are 76mm (3 inch), 100mm, 127mm (5 inch) and 130mm. The Oto Melara 76mm family is used by a dozen Asian navies while the Russian single barrel AK-176 and the twin barrel AK-276 by  India and Vietnam; the Russian 100mm AK-100 and the Chinese derivative the ENG-2 are used by five navies. The largest calibre weapons are 127mm by Oto Melara 127/54 (licence-built in South Korea as KD 127) used by two navies while the BAE Systems Mk 54 is used by six. The Chinese Navy uses twin-barrel SM-2 mountings. With ranges of  8.5 nautical miles (16 kilometres) for the Oto Melara 76/62 to 15 nautical miles (38 kilometres) these weapon mountings tend to be unmanned with below-deck magazine or magazines which feed high explosive, semi armour-piercing and multi-mode ammunition to the breech through a remotely controlled handling system. However, they are

relatively short ranged and would not normally be used in engagements with major surface combatants. They, too, are very versatile with an AAW role, and though their range reduces their effectiveness they can still protect against Unmanned Aerial Vehicles (UAV) and in-coming missiles.

While the 76mm gun is often used in fast attack craft small surface combatants of this type as well as patrol boats have alternative gun systems for the ASuW role, as well as for ship self protection especially in harbours or restricted waterways against FIAC or suicide type threats. The most popular calibre weapons are 30-40mm because they have high sustained firing rates; 650-700 rd/min for Oerlikon 30mm and 300 rd/min for Bofors 40mmL/70, as well as longer ranges up to 3.2 nautical miles (6 kilometres) for an Oerlikon (with extended range ammunition) and 6.75 nautical mile (12.5 kilometres) for the Bofors. One of the most unusual Asian gun mountings is the Indian Ordnance Factory’s CRN-91 Sarath based upon the turret of the Russian-designed BMP-2 infantry combat vehicle with 30mm gun. It has been navalised for the Indian Navy and Coast Guard in patrol boats as well as the Magar class tank landing ships.

The older weapons are manned but there is a tendency towards unmanned mountings with Oto Melara producing the widest range in both with single and twin calibre mountings in use with half-a-dozen navies while 40mm mountings have been made in South Korea and Singapore. Bofors enhanced their

weapon through the 3P (Prefragmented, Programmable Proximity) rounds which may be set to impact, post-impact or proximity settings before being fired. BAE Systems Weapon Systems and Support are completing development of the Bofors 40mm Mark 4 gun system which incorporates technology from the Mark 3 (bought by Brazil and Japan) as well as weapons used in the CV90 infantry combat vehicle. The objective is to cut the weight, cost and volume of the Mark 3 mounting by at least 40 per cent so that it could fit into smaller vessels to broaden the market.

The mounting is available with remote and manual control and weighs 2.3 tonnes unloaded compared with 4 tonnes for the Mark 3 and it is only 1.99 metres high and 2.14 metres wide. It is deck-mounted with 70-round reloadable magazine in the 1.845 metre diameter mounting ring to augment the 30 rounds in the mounting. The 70 calibre weapon can fire 300 rounds/minute up to 6.75 nautical miles (12.5 kilometres) and should be available to customers early in 2014 and the company plan to offer packages with electro-optical directors.

There is a growing tendency towards mountings which are compatible with several guns. One is Rafael’s Typhoon which can carry seven different models, and with on-mount electro-optics is produced by BAE Systems in the United States as the US Navy’s Mk 38 Mod 1 (unmanned) and Mod 2 (unmanned) with 25mm Bushmaster gun. Typhoon is used by six Asian navies. BAE Systems Land and Armaments, which produces the mounting under licence, revealed at Euronaval in October a mock-up of a Mod 3 version with 25mm or 30mm Mark 44 Bushmaster II. The mounting, with on-board electro-optical director as in Mod 2, is being developed in anticipation of a requirement for a 30mm gun to equip the Littoral Combat Ship with a formal requirement anticipated this year. The elevating mass and most of the barrel are fully enclosed with a shaped housing and, compared with the 1.04 tonnes unloaded weight of the Mod 2, the new mounting, which will also be marketed for export and can accept coaxial machinegun, will have unloaded weights of 1.35 tonnes with 30mm gun and 1.28 tonnes with 25mm. The Oto Melara Model 504 Marlin, for example, accepts 30mm and 25mm weapons as does MSI’s Seahawk family, and the AAW capability of the latter is enhanced with short-range Thales LML  surface-to-air missiles.

Remotely operated and stabilised mountings, such as Nexter’s Narwhal 20mm gun family and MSI-Defence Systems’ Seahawk 20 are becoming available to provide even greater versatility. Narwhal has a mass of 350-400 kilogrammes, an on-mount director with optional laser rangefinder and plans for 25mm and 30mm versions. Seahawk has been developed for the retrofit market and while based upon the Denel G12 20mm it can take any 20mm weapon allowing the continued use of stocks of 20mm x 139 ammunition.

While the gun’s importance in ASuW is much smaller than it was it still remains important with the smaller calibre weapons also being valuable in the field of EEZ protection where collateral damage can be politically unacceptable.

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