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Secrets of the stealth ship
A stealth ship - one invisible to enemy radar - may sound like the stuff of a James Bond film, but the maritime equivalent of the US air force B2 bomber is undergoing weapons installation at a naval shipyard in the south of Sweden.
According to the Swedish navy, the first of the Visby Class corvettes, which is currently sitting in the naval dockyard in Karlskrona, is a completely new type of warship: a frigate that is lighter and faster than a conventional ship and almost invisible to enemy detection. It is the largest vessel ever built from carbon fibre - a super-hard, lightweight plastic - which also marks a breakthrough in shipbuilding materials. The last time this happened - you could argue - was when Isambard Kingdom Brunel switched from wood to steel with the SS Great Britain in 1843.
Sounding more like an Ikea sofa than a warship of the future, the Visby is being primed to patrol Sweden's territorial waters and participate in joint operations within the EU and UN task forces. The ship, the first of five on order for the Royal Swedish Navy, will have a crew of 43 (including 16 conscripts) and will go into operation in January next year.
The Visby weighs approximately 600 tonnes, about half as much as a conventional corvette, and features a hangar for an Agusta-Westland helicopter, which can land on the upper deck and be retracted into the hull. The Visby's 57mm cannon also retracts so as to not to spoil the ship's radar signature. The Visby is designed for anti-submarine warfare and can sneak up on the enemy and plant anti-submarine mines without being seen.
The Royal Swedish Navy began searching for a material for a stealth ship in the immediate aftermath of the cold war.
"All of our exercises and training during the cold war period was a matter of stopping an enemy from the other side of the Baltic," says Lieutenant Commander Ulf Öberg of the Swedish navy. "All the Baltic states are now in the European Union and the Russian navy is not so much of a threat anymore. We no longer need the big ships."
The Swedes decided to switch from steel to plastic - two layers of carbon fibre filled with a PVC-like foam - in the search for a radar resistant material. By using a composite material, they found one that could dramatically reduce a ship's signature, making it not only less detectable by radar, but also less prone to enemy mines and other forms of electronic detection such as infrared. And if it is detected, the Visby should be quick enough to escape as it is only half as light as a conventional corvette.
Moreover, in searching for a radar-resistant material, the Swedes seem to have stumbled across a technology that could offer improved strength and rigidity, lower weight and better shock and flame resistance than steel. Kockums, the ship's builder, says ships made from carbon fibre enjoy lower running and maintenance costs and lower fuel consumption.
According to Kockums, the Visby costs roughly one and a half times more to build than a conventional corvette. But the shipbuilder argues that the Visby is a far more cost-efficient vessel over the long run
"Carbon fibre is not a cheap material - that's the trouble," admits Kjell Göthe, head of information at Kockums. "But if you look at the ship over the course of 30 years and you look at all the costs it is cheaper than a steel ship. The maintenance is nothing to talk about."
Carbon fibre is one of the toughest known materials - and that is why it is so expensive. It is so tough that Kockums had to develop the cutting technology to build the Visby. "We had diamonds in the beginning but they were destroyed after a very short time," says Göthe. "What we use now is an extremely high pressure water jet. I think it is a bit incredible but a water jet is better."
The Visby's stealth properties are not its only hi-tech component. The ship includes a command and control centre that uses a Windows NT operating system. The Swedes insist that this will not make the vessel vulnerable to hacker attacks, although the navy will not be drawn on the potential for the system - armed with hi-tech cannon and missiles - to crash. While the point-and-click system is popular with conscripts, the ship was fitted with a wooden ship's wheel at the insistence of senior officers. If Windows goes down, they will still be able to steer.
Racing yachts and patrol boats have been manufactured from composite materials before, but the Visby is the largest ship to be made from carbon fibre. It could be a little early to talk about new trends in shipbuilding as the Visby has only recently finished undergoing sea trials and won't be fully operational until January, but US shipbuilders including Lockheed Martin, General Dynamics Corp and Raytheon are also designing similar stealth ships for the Pentagon. The next generation of US destroyers, the DDX, is also reported to be built using composite materials and the Royal Navy is believed to be looking at carbon fibre as a potential shipbuilding material. If the Visby really does turn out to be more cost-efficient than a steel ship, some maritime analysts believe that it could be a matter of time before merchant vessels begin to be made from tough plastics.
"The use of composite materials is very exciting," says Stephen Saunders, editor of Jane's Fighting Ships. "There is no reason why ships should not be made of carbon fibre as long as they are up to the job. The fact that the Americans are using it in the superstructure in their next destroyers certainly points in that direction."
For now, the Visby is the lightest and fastest in its class. But is it the only one? Ominously, the Guinness Book of Records museum in Florida says there could be another, much larger stealth ship already out there. They just don't know how to find it.
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