Visby Class Corvette
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 represents "stealth all the way" which we at Saab/Kockums define as: Genuine Holistic Stealth - GHOST®
HULL DESIGN - ATTENTION TO EVERY DETAIL
Flat surfaces and concealed equipment reduce radar signature to a minimum. 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.
Stealth technology (more formally called Low Observable Technology) aims at minimizing a vessel’s transmitted and reflected energies – heat, light, sound, electric potential, and electromagnetic radiation – to deny an opponent the opportunity to locate, identify, track, and attack it.
Stealth technology makes full use of aggressive architecture, controlled reflection and absorption, colour variation, machinery isolation, ordnance concealment, shielding, and electronic countermeasures (jamming or false imaging) to mask a vessel’s very existence.
We tend to think of stealth as a relatively new idea – developed for modern aircraft such as the B-2 bomber introduced in 1988. In truth, stealth is an instinctive human practice that appeared early in history. Millennia ago, “hunter-gatherers” wore facial and body paint, feathers, tree branches, animal skins, or anything else to help them fade into the background and not alarm foe or animals they sought.
The Visby is equipped with myriad machines and systems ready to fulfill her missions, one of which is mine countermeasures. For this, Visby has active and passive sensors that detect, classify, and home-in on mines. A remote-controlled Double-Eagle Mk III underwater vehicle (ROV-S) is guided well ahead, at appropriate depth, where high-resolution sonar and television cameras identify and locate mines long before the vessel reaches them.
The mines are then destroyed by an expendable Atlas Elektronik Seafox ROV-E. (Visby is also equipped with mine rails, mine-launching gear, and computer capability to set minefields and register mine locations.) The navigation system takes input data from the log, gyro, and Global Positioning System (GPS) satellites, and computes an extremely accurate plot.
At slow speed, the automated diesel propulsion, guided by more precise Differential GPS, closely follows a preset track or – by dynamic positioning with waterjets and thruster – holds the vessel stationary for mine work. The automation minimizes human error and reduces crew workload, improving safety.
The main submarine detection sensor is a Hydroscience Technologies passive Towed Array Sonar (TAS) with hydrophones. It is towed up to 1 000 meters astern to avoid turbulence or interference from the ship, and can also detect surface vessels running beyond the range of Visby’s radar.
For anti-submarine work, Visby also uses a towed dual-frequency Variable-Depth Sonar (VDS). Once the TAS detects a submarine, VDS fixes its position and aims selected weapons at it. A hull-mounted sonar helps classify submarines or detect mines. If the target is lying on the seabed, the ROV-S can also identify it. A Hydra multi-sonar suite from General Dynamics Canada integrates data from the towed-array, variable-depth, and hull-mounted sonars, and data from the ROVs.
An Underwater Environmental Monitoring system supports the Hydra in mission planning. Visby corvettes are equipped with several anti-submarine weapon systems, beginning with four fixed.
[via - saabgroup]
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