HMS Audacious (S122)

HMS Audacious is the fourth Astute-class nuclear-powered fleet submarine of the Royal Navy. Several previous vessels of the Royal Navy have borne the name. Long lead items for her construction were ordered on 28 August 2006 although the actual order was not placed until 21 May 2007. She was nearly halfway through her build programme.

Some aspects of the later Astute class submarines will be different from boats 1-3, mostly related to the combat system—primarily the command, navigation and sonar systems. This is the first Royal Navy submarine which uses a shared computer environment for the different systems, common consoles and cabinets, and commercial "off-the-shelf" hardware and software, to reduce costs and improve maintainability. These changes have been back-fitted to boat 3, Artful; the eventual aim is to back-fit the "Common Combat System" to HMS Astute and Ambush, and progressively to the rest of the Royal Navy submarine fleet.

Nuclear power
Audacious's nuclear reactor will not need to be refuelled during the boat's 25-year service. Since the submarine can replenish her air supply and purify water under way and while submerged, she will be able to circumnavigate the planet without resurfacing. The main limitation on the submarine's dived endurance will be due to consumable supplies, including the three months' supply of food carried for the 98 officers and ratings.

Weapons
Audacious will carry a mix of 38 weapons in six 21-inch (533 mm) torpedo tubes;
 * BGM-109 Tomahawk Block IV cruise missiles. Range of 1350 nmi.
 * Spearfish torpedoes.