ANTI-SHIP MISSILES have changed the nature of naval warfare because small, fast attack craft and aircraft have the same lethal punch as large ships. In addition, anti-ship missiles increase the range of engagements, multiply the number of platforms capable of offensive operations and decrease the warning time available to defenders. Ships as small as the 3,500-ton Indian Navy Khukri corvette carry a powerful armament of 16 100km-range Kh-35 Uran anti-ship missiles. The Russian Kursk-class Antyey type 949A submarine is armed with 24 supersonic 500km-range anti-ship missiles.

In recent actions fixed and rotary-wing aircraft armed with anti-ship missiles have demonstrated operational advantages over ship, submarine and land-based systems because they allow greater employment flexibility and superior sensor range. Over 70 nations field anti-ship missiles and despite major investment in naval missile-defence systems, engagements overwhelmingly favour attackers. Dozens of warships and nearly 200 civilian vessels have been sunk or damaged by anti-ship missiles during the past 30 years, the largest percentage of successful ship strikes coming from aircraft. Some ships are known to have evaded missiles through the use of decoys, ECM and tactics but only a small number of missiles have been shot down.

Current missiles The Harpoon - over 6,000 sold to 24 customers - and Exocet - over 3,300 sold to 32 customers - are the most widely deployed western anti-ship missiles; Russian and Chinese variants of the obsolete Styx probably hold first place. Firms in over a dozen nations produce anti-ship missiles including the USA, France, Norway, the Peoples' Republic of China, Taiwan, Japan, Russia, Sweden and Italy being the largest producers.

Air-launched anti-ship missiles in service range from Russian nuclear armed supersonic missiles to Hellfires on helicopters. The Russian Zvezda Kh-31 is one of the most capable missiles in service. An advanced Mach 2 rocket ramjet with a range of 50-70km, it can be fired from MiG-29, Su-27, and now the F-4. Boeing and Zvezda have teamed-up to export the Kh-31 to the USN as a supersonic target. Russia also has a number of other highly capable airborne anti-ship missiles including the Raduga Kh-41 Moskit with a 135km range and supersonic performance.

The Soviet Union, unable to match the US and allied superiority in aircraft carriers and surface combatants, turned to fast attack craft armed with tactical anti-ship missiles with high- explosive warheads only, such as the P-15-27 (SS-2-N Styx) widely exported and produced in China. Some Russian fast-attack craft and Charlie II-class submarines were armed with the more advanced P-50 (SS-N-9 Siren). Russia still fields the widest array of anti-ship missiles, the 4,800kg P-500 Bazal (SS-N-12 Sandbox) and upgraded P-700 Granit (SS-N-19 Shipwreck) remain in service on major naval combatants. Another advanced Russian system is the supersonic Raduga 3M-80 (SS-N-22 Sunburn) that can hit targets up to a range of 120km and has Mach 2 at low altitude. It was fielded in 1984 on the Sovremenny-class destroyers, and supplied to China. The 3K-60 Uran that is similar to the US Harpoon, is replacing the Styx and other old systems. It has been exported to many nations including India and Algeria.

The only western system similar in capability to Russian strategic missiles was the US Navy UGM/RGM-109B Tomahawk anti-ship missiles (TASM). The subsonic TASM that could be fired from ships and submarines, had a Harpoon active radar seeker, an ESM system for target detection and four times the range and twice the warhead weight of the Harpoon. However, the Tomahawk ASM version was replaced on US ships in the 1990s by land-attack variants of the Tomahawk as mission requirements shifted.

In contrast to large Russian anti-ship missiles, most western navies opt for smaller subsonic systems such as Harpoon and Exocet. The Harpoon is a good example of modern, anti-ship missiles' evolution. Incorporation of new technology has enhanced tactical capability and mission performance allowing the system to grow to meet the threat. In 1995, the long Harpoon Block IG that featured an improved seeker and additional mission flexibility including the ability to re-attack a target if it were missed on the first pass, was introduced.

By 1990 the US Navy fielded the stand off land attack missile (SLAM) that combined the imaging infrared seeker from the Maverick missile, datalink from the Walleye glide bomb and Harpoon airframe, engine and warhead to create an air-launched, man-in-the-loop precision strike weapon.

Air-launched missiles A number of specialised anti-ship missiles were fielded during the 1970s and 1980s that were designed to be fired from aircraft against ship targets. The rocket-powered German MBB AS34 Komoran armed the Tornado. This 30km range missile had a radar seeker and a 165kg warhead with a fragmentation pattern designed to be lethal to ships. The UK funded the development of the turbojet-powered Sea Eagle that armed its Tornado and Sea Harriers in the anti-ship role, more than 800 of these 110km-range missiles bought by the UK, Saudi Arabia and India are now being phased out of service.

Norway fielded an air-launched version of the infrared-guided Penguin anti-ship missile for its F-16A/B fighters and an improved version has been sold to arm US Navy SH-60 Seahawk helicopters. Israeli Phantoms and Skyhawks were armed with the Gabriel Mk 3, an active radar-seeking variant of the Israeli developed anti-ship missile. The AGM-65F/G Maverick air-to-ground missile has been fitted with a passive IR seeker and a 136kg blast warhead with delay-option fuse for use against ship targets. This 12km range missile can be carried by F/A-18s, P-3C MPA and helicopters.

Lightweight and relatively inexpensive anti-ship missiles developed by western companies include the British Sea Skua and AS15TT that use radar guidance, while the US Hellfire employs laser guidance. Although the range of these systems is only 10-20km and the warheads are small (10-30kg), they have proven to be effective in attacks on small naval vessels.

Upgraded second-generation anti-ship missiles can tackle almost any open-ocean conflict where an adversary is in open battle formation. Advanced mission planning systems and waypoint turns enable missiles to fly around islands or other obstructions to attack potential targets among known shipping. However, even advanced second-generation anti-ship missiles have limitations engaging vessels close to land and cannot hit ships at a pier nor threaten shore targets such as a missile or gun battery or radar site.

Littoral operations Following a shift in focus from open ocean to littoral or coastal operations, navies are calling for missile systems that can engage surface threats at sea and small vessels in congested coastal waters or even ships in port. And future systems must be able to deal with increasing levels of deception and active defences. To meet evolving tactical challenges missile producers are developing new systems to improve the capabilities of current models in the littoral arena and new-generation missiles with subsonic and supersonic performance are in advanced development.

The Boeing Harpoon Block II integrates a global positioning system (GPS) receiver developed for the loint direct attack munitions programme with modern inertial navigation systems to eliminate missile-position uncertainty. This allows for smaller seeker search patterns and helps to ensure that the designated target is found and struck. The new guidance system also facilitates the Harpoon Block II attacking vessels near the coast or at pier and for it to hit land targets with 10m accuracy.

The Saab RBS 15 Mk 3 also is undergoing a major upgrade that will enhance the weapon's anti-ship performance and allow for the future addition of GPS, a dual-mode seeker and two-way data link to enhance littoral and land- attack performance. A new version of the Exocet with turbojet power for longer range, a more capable seeker and reliability upgrades is now in development. The Kongsberg Aerospace NSM, developed in co-operation with Aerospatiale, is a subsonic turbojet-powered low-observability missile intended for launch from Norwegian frigates and fast attack craft. Designed as a replacement for the Penguin, this 450kg missile includes GPS and an advanced infrared seeker allowing for the attack of ship and land targets.

The future The 200km-range, ramjet-powered French-German Anti-Navire Futur (ANF) was to be the first western supersonic anti-ship missile. However, funding problems led to Germany's withdrawal from the programme that Aerospatiale is maintaining to prove the concept. Advancements in technology are leading to a new generation of missiles that will be faster, smarter and able to engage targets at sea and on land. The American Harpoon Block II, SLAM ER, plus Norwegian/French NSM and Swedish RBS 15 Mk 3 are examples of anti-ship missiles that have been upgraded and enhanced to expand their utility against multiple types of target.

It is expected that guidance systems using advanced computer technology will be able to detect and identify targets automatically. Several cruise missiles (SLAM ER and JASSM) already have this capability against land targets. Missiles are also expected to get much faster. Russian company NPO Mashinostroeniya has demonstrated an advanced supersonic Yakhont missile with a solid rocket booster and a liquid-fuel ramjet with a range of over 200km to replace the Sunburn in air and surface-launch variants. The USN and DARPA, with potential funding from the UK, have awarded several study contracts to meet the goal of rapidly developing and fielding a 2,000lb (907kg), 680-mile(1,100km) hypersonic (Mach 3.5-7) missile capable of launch from the F/A-18 E/F, F-35 JSF, ships and submarines to be fielded by 2015.