The Astute-class is the largest, most advanced and most powerful attack submarine ever operated by the Royal Navy, combining world-leading sensors, design and weaponry in a versatile vessel. The submarines are nuclear-propelled and fuelled by a nuclear reactor powerful enough to supply a city the size of Southampton. Its advanced technology means the submarines will never need to be refuelled. They employ the latest sonar technology, using the largest number of hydrophones ever fitted to a submarine. Linked with powerful onboard electronics these provide the submarines with outstanding sensitivity. The Astute submarines are armed with the latest versions of Spearfish heavy-weight torpedoes and Tomahawk land-attack cruise missiles.