THE West has some formidable missiles designed to sink warships. Three of the most deadly are America's Harpoon, France's Exocet and the Swedish RBS-15. These all fly close to the speed of sound for up to about 200km (124 miles) using precision-guidance systems to skim over land or water. This makes them difficult to detect. And even if they are spotted, the missiles can fly in unpredictable patterns, which makes it harder to shoot them down. They then punch a warhead, weighing as much as 200kg (440lbs), into a moving ship with devastating consequences.

Despite all this, missile defences can be effective. Shooting at missiles with rapid-firing guns, or anti-missile missiles, can bring them down. The incoming missile's electronics can also be scrambled with blasts of electromagnetic radiation, such as microwaves. And decoys can be fired to trick the missile's homing sensors and lure it away from the vessel under attack. But missile attacks on ships are rare, so it is difficult to know just how safe a ship really is—especially if an attacker launches a dozen or so missiles at once.

One particular anti-ship missile has become especially worrying for Western defence chiefs. This is because it is even more fearsome than anything NATO countries and their allies now use. The Russian-made missile is called the Club and it can carry bigger warheads farther than any anti-ship missile the West can launch.

As is the way of NATO nomenclature, the Club has been designated another name, the Sizzler. In some configurations the Sizzler can deliver about 450kg of explosives as far as 300km. It also carries out defensive manoeuvres—even curving around islands—and some lighter versions perform a unique, nasty trick: the warhead separates a few dozen kilometres away and then accelerates from almost the speed of sound to about three times as fast.

Sizzling targets

Tim Keating, an American vice-admiral, told the House Armed Services Committee early last year that America's ability to defeat the Sizzler was uncertain, not least because the military lacked an adequate dummy stand-in for testing defensive systems against such a fast missile. Now one is in the works. Dan McNamara, a manager with the US Navy group developing what is called the Multi-Stage Supersonic Target, says it will help defeat the “groundbreaking” Sizzler. The new missile is expected to be ready in 2014.

The Sizzler is the leading example of a growing class of supersonic cruise missiles designed by non-Western countries. Versions of it, and its competitors, can be launched from submarines, aircraft and vehicles. The Yakhont, a slightly slower Russian missile that also carries a heavy warhead, has been sold to countries including Indonesia and Vietnam. The BrahMos, a joint Indian and Russian upgrade of the Yakhont, comes even closer to matching the Sizzler's effectiveness.

These non-Western supersonic missiles are changing defence thinking. To begin with, uncertainty about ship “survivability” is increasing as missiles proliferate, says Steve Zaloga, a missile expert at Teal Group, an aerospace consultancy in Fairfax, Virginia. China and India already have Sizzlers and countries that have indicated interest in, or bought, the Sizzler or versions of it include Algeria, Syria, the United Arab Emirates and Vietnam. Some think Iran probably has Sizzlers too.

As a rule of thumb, to hit a well-defended modern warship a volley of more than ten subsonic missiles might be needed, according to an expert at Thales, a French defence contractor. How much deadlier might supersonic ones be? Sinking a warship, especially a big one, is unlikely with a single missile, whether supersonic or not. More probably, attackers would score a “mission kill” that limits a ship's ability to fight. In 2006 a subsonic missile fired by Lebanon's Hizbullah militia seriously damaged an Israeli corvette more than 15km offshore. Four sailors were killed.

Hizbullah's success highlights the so-called “asymmetric” element of anti-ship technologies: striking a warship can be far less expensive and complex than operating and defending one. According to Rafael, an Israeli defence contractor, a ship's protection gear often costs as much as its attack weaponry. Missiles are now the “poor man's way” of obtaining sea power, says Nathan Hughes, an analyst at STRATFOR, a consultancy in Austin, Texas.

Iran is one country gaining naval power without much in the way of sophisticated ships. It has large numbers of anti-ship missiles which can be launched from small, fast boats or batteries hidden ashore in buildings or trucks. Defence officials are troubled by the prospect of missiles that can be launched from civilian positions. A product designed by Concern Morinformsystem-AGAT, the Russian company behind the Sizzler, may heighten such fears. The firm now offers a four-missile launching package hidden inside a standard commercial shipping container. It could be transported on a ship, train or big lorry. Called the Club-K Container Missile System, it provides dangerous potential to rogue forces, says a Western arms-market consultant who has visited the manufacturer's facilities in Russia.

Defensive technologies, of course, will also improve. Sofradir, a French remote-sensing defence contractor, plans to start making a “multichannel” missile-detection system later this year. (Early versions are already being tested by potential customers.) It integrates radar, infra-red and visible-light sensors into a single unit. Software can then better assess the quality of data from one channel by comparing it with data from the other two. Such sensing technology should make it easier to “lock onto” (and therefore shoot down) incoming supersonic missiles, especially when they tend to gain altitude to pinpoint a target before dropping down for a final sea-skimming approach, says Philippe Bensussan, Sofradir's chief executive.

From the deep

But there are also threats from below to deal with. The sinking in March of a South Korean frigate provides a further example of the asymmetric nature of anti-ship weapons: the evidence suggests that it was sunk by a torpedo fired from a North Korean “midget submarine” small enough to hide in shallow water, where it is hard to detect using sonar. North Korea is thought to have supplied such submarines to Iran.

Torpedoes can still be tricked, in many cases, with decoys that emit sound waves to mimic ships. But torpedoes, like missiles, are getting smarter. Their homing and guidance systems are improving. Many torpedoes, once fired, can be controlled via a long optical fibre that remains attached to the submarine to increase accuracy and prevent jamming. And some torpedoes will now circle back if they miss a target on the first pass. At Rafael, the Israeli defence contractor (and a maker of anti-torpedo countermeasures), a spokesman reckons that torpedo effectiveness has roughly doubled in the past decade, also in part because of work carried out in Russia.

Missiles are now the “poor man's way” of obtaining sea power

Torpedoes rarely travel faster than 100kph because water friction and turbulence could cause them to veer off course or suffer damage. But now speeds can be doubled or even tripled by “cavitating” torpedoes. The trick involves positioning a flat disk, smaller than a DVD, about 10cm in front of the torpedo's nose tip. At high speed the disc vaporises water, creating a steamy air bubble, called a cavity, which envelops the torpedo. This dramatically reduces water drag.

Cavitating torpedoes remain rare, not least because they are problematic. High speeds can make it hard to decipher the sonar signals used for guidance. Propulsion is provided by a rocket engine, rather than a propeller and rudder, which makes steering difficult: some cavitating torpedoes can travel only in a straight line. High pressures deep underwater pose further difficulties, and may have contributed to the sinking of Russia's Kursk submarine in 2000, killing all on board. (It sank after an explosion during the testing of a cavitating torpedo called Shkval, or Squall.) A German cavitating torpedo called the Barracuda is thought to be the fastest, but Russia's Shkval is sold more widely.

As ship vulnerability increases navies are buying more submarines, especially in Asia, says Ramli Nik, Malaysia's defence attaché to the United Nations until 2004. Malaysia will receive its second attack submarine by the end of the year, he says. Other countries plan to buy or build more. Australia expects to double its fleet of six; Indonesia aims to expand its fleet from two to 12 and Singapore expects to double its fleet of four. Vietnam has none but plans to have six by 2025. By then, China may have 70 attack submarines. Mr Nik thinks submarines provide the best naval defence platform. With modern remote-sensing kit, they can stealthily “get all the details” of warships, he adds.

Yet warship-building is far from declining. Naval budgets, broadly speaking, are growing because of a big shift in strategy caused in part by improved missile capabilities. Premvir Das, a former commander of India's Eastern Naval Command, says the availability of fast, powerful and accurate cruise missiles is encouraging forces to restructure so that they are better able to conduct, or support, land warfare from the sea. India, he says, will extend the range of its BrahMos missile “quite substantially” beyond its current 300km range.

Even more exotic new weapons could be just over the horizon. About five years ago Pentagon officials learned that Chinese engineers working on a government missile project appeared to have solved a difficult technical challenge involving manoeuvring with radar data. According to Eric McVadon, a retired American rear-admiral, some of his fellow defence officials began “running around with their hair on fire”. China was modifying a medium-range space-faring ballistic missile, the DF-21, so it could re-enter the atmosphere and nosedive, at about two kilometres a second, into a warship and detonate conventional explosives. The new missile could be ready for testing by 2012.

China's missile might be vulnerable, some experts say, to America's newest Aegis intercept missiles, which are launched from ships. But a different type of countermeasure could be even more effective. America and France are among a few countries developing powerful lasers to shoot down missiles. As a former American battle-group commander notes, a nuclear-powered aircraft-carrier generates enough electricity to power a small city, let alone a powerful laser. “Literally, that's ammunition,” he says: “directed energy” which can be delivered by laser. And no missile can travel as fast as light.