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Further Reading

Visby

The Visby Class corvette is the first vessel in the world to have fully developed stealth technology, combined with high operational versatility. The outstanding stealth properties fundamentally change the ship's survivability and improve its mission effectiveness. Visby is a flexible surface combatant, designed for a wide range of roles: anti-surface warfare (ASuW), anti-submarine warfare (ASW), mine countermeasures (MCM), patrol and much more.

The Visby Project is the largest surface vessel project ever conducted by Kockums. The project, which has been in progress for more than a decade, has evolved steadily, attracting considerable attention for its stealth technology. The vessels are built in plastic laminate, a material that makes the ship very strong and resilient in relation to their weight. The material is one of the factors that gives the vessels very low signature levels, in terms of radar, magnetic and hydro-acoustic. This makes them difficult to detect on radar and infrared camera. At the same time the vessels can withstand shock effects very well and they can also take a big load.

The Visby corvettes are designed for inclusion in the new rapid-reaction force. Their stealth technology makes them difficult to detect with radar and other advanced forms of detection. Everything can be seen and heard from the bridge, while the vessel itself remains undetected, offering multiple tactical benefits. The vessel can also de-activate its stealth mode, if it wishes to demonstrate its presence, and then reactivate to 'vanish' again. The Swedish Navy has always operated in the littoral and is highly specialized in the necessary techniques. Of course, there are many littoral zones across the globe, through which exports and imports must be shipped from and to the world's large and growing ports. In a post 9/11 world, this is precisely where the threat lies. A well-planned terror attack could have devastating consequences.

There is considerable international interest in the Visby corvettes: open almost any international naval journal and the impact of the Visby-class ships is immediately apparent in many new naval designs. But so far, Sweden is the only country to have built a true stealth corvette. It is of course vital that Sweden exploit this lead. But one of the Swedish vessels must be fully operational with the Swedish Navy before export orders start arriving at Kockums, because a reference customer is crucial in securing an export order.

"In the Swedish Navy's operational environment, namely the littoral zone, the stealth-technology Visby-class corvettes are the right concept for the future. After final delivery and commissioning, these vessels will form the core of the Swedish Navy for years to come. And our stealth concept has already attracted considerable international attention," says Rear Admiral Anders Grenstad, Inspector General of the Royal Swedish Navy.

In 1986 the Swedish Defence Material Administration (FMV) initiated the development of a stealth test platform, HMS Smyge. It was launched in 1991 and used for testing stealth characteristics in all possible aspects. This formed the basis for the YS 2000 project - the Visby Class corvette.

Kockums has already built four of the Visby corvettes and delivered them to the customer, FMV (the Swedish Defence Matériel Administration), which conducted a program of trials and tests. The fifth of series, HMS Karlstad, was under construction in 2008. The Visby corvettes are designed to handle all types of naval mission, including mine clearance, antisubmarine warfare (ASW), surface combat, marine surveillance and the protection of commercial shipping.

HMS Helsingborg and HMS Härnösand were the first two corvettes in the Visby series delivered to the Swedish Armed Forces to be included in the organization and ready for missions. FMV handed over the two ships to the Armed Forces at a ceremony in Karlskrona on 16 December 2009. The two ships which are now handed over is equipped with over-water and underwater sensors and are in this version (version four) able to be operational in a number of national and international tasks. When the first Visby corvettes will be delivered in version five in 2012, there will be trained crews available. The ships have since been supplemented by including mine clearance systems, helicopter landing capability, anti-surface ship missile and additional stealth adaption.

The Visby is designed to minimize all signatures - optical and infrared signature, above water acoustic and hydroacoustic signature, underwater electrical potential and magnetic signature, pressure signature, radar cross section and actively emitted signals. The difference in detection range between an ordinary vessel and Visby creates a considerable zone where the Visby can see but not be seen.

The vessels has been equipped to bee able to cooperate with other parts of the Armed Forces that occur in the maritime area, such as the air force, coast guard, civil protection, customs, police and civilian shipping. The Visby corvettes will also be able to behave in particular as a good management of resources for long-term efforts at sea.

All missions are supported by CETRIS - the real-time command, control, communication, intelligence and interoperability system (C4I2). The system is modular and open, and allows for integration of future technologies, without expensive changes.

The Visby is designed for the installation of a surface-to-surface missile (SSM) system. On the Swedish version, eight SSM (RBS15 MkII) can be fully integrated into the hull and covered with smart rapid hatches.

The air defence system (ADS) is totally integrated, and it dynamically, automatically and simultaneously calculates and performs hard-kill as well as soft-kill engagements. The active part of the ADS consists of the Bofors 57 mm multi-purpose gun, with a new, stealth cupola designed as an integrated part of the hull structure. The Visby is designed for the installation of an air defence missile system (SAM), fully integrated into the aft part of the vessel. The ADS also includes the ESM and various electronic countermeasures.

The MCM system consists of a combination of extremely low signatures, sensors and weapons, and very high shock resistance. For detecting and classifying mines, the Visby uses ROVs (remotely operated vehicles).

A powerful sonar system is used to detect, locate, classify and supply real-time target data to the weapons. In addition, the sonar-equipped ROV-S can be launched for surveillance and classification of targets.

The Visby is equipped with wire-guided, homing 40 cm torpedoes. A submarine can also be attacked with an ROV-E or the brand-new 5" ASW multiple rocket system.

The hull is designed on stealth principles with large flat angled surfaces. Every feature that need not necessarily be located outside the hull has been built in or concealed under specially designed hatches. The gas turbine exhausts have been concealed in hidden outlets close to the water surface at the stern of the vessel.

The vessel is built of sandwich-construction carbon fibre reinforced plastic (CFRP). The material provides high strength and rigidity, low weight, good shock resistance, low radar signature and low magnetic signature.

The material dramatically reduces the structural weight (typically 50% of a conventional steel hull). This results in a higher payload carrying capability, higher speed or longer range.

The Visby is equipped with a combined diesel or gas (CODOG) turbine arrangement for high speeds and two diesel engines for low-speed. The engines are connected to two gearboxes, driving two waterjet propulsors. The engines provide a maximum speed of 15 knots for long duration and 35 knots for short duration. The ship has bowthrusters for harbour manoeuvring.