Active sonar uses the reflection of sound emitted from the search equipment to detect submarines. It has been used since WWII by surface ships, submarines and aircraft (via dropped buoys and helicopter "dipping" arrays), but it reveals the emitter's position, and is susceptible to counter-measures.

As early as World War I, it was realized that the optimal shape for withstanding pressure conflicted with the optimal shape for seakeeping and minimal drag at the surface, and construction difficulties further complicated the problem. This was solved either by a compromise shape, or by using two layered hulls: the internal strength hull for withstanding pressure, and an external fairing for hydrodynamic shape. Until the end of World War II, most submarines had an additional partial casing on the top, bow and stern, built of thinner metal, which was flooded when submerged. Germany went further with the Type XXI, a general predecessor of modern submarines, in which the pressure hull was fully enclosed inside the light hull, but optimized for submerged navigation, unlike earlier designs that were optimized for surface operation.An obvious way to configure the control surfaces at the stern of a submarine is to use vertical planes to control yaw and horizontal planes to control pitch, which gives them the shape of a cross when seen from astern of the vessel. In this configuration, which long remained the dominant one, the horizontal planes are used to control the trim and depth and the vertical planes to control sideways maneuvers, like the rudder of a surface ship. The Astute-class are capable of circumnavigating the globe while submerged, producing their own oxygen and drinking water to sustain the crews on arduous and lengthy deployments.

It requires an additional component in the form of a dedicated generator. Since the electric motor is always used to drive the propeller it can no longer step in to take on generator service as well. Missing Titanic submersible: Maps, graphics show last location, depth and design Who is on the passenger list of the submersible? This contract is for a truly transformative submarine training solution and builds on the success that we have had to date in transforming the Royal Navy’s training and learning solutions. After loading Tomahawk missiles – just one part of the Astute-class’s powerful armoury alongside the Spearfish heavyweight torpedo – in Gibraltar, Audacious sailed into the Mediterranean and completed exercises with NATO allies, including training with Greek, Turkish and United States allies. Making sure all equipment is ready for long-term action is vital before Audacious stepped off on operations.

USS Gurnard conducted three Polar Exercises: 1976 (with US actor Charlton Heston aboard); 1984 joint operations with USS Pintado; and 1990 joint exercises with USS Seahorse. [55]