This was Britain's first nuclear powered submarine.
'Fleet Submarine' (SSN).
The contract to build Dreadnought was given to Vickers who was by far the most experienced submarine builder for the Royal Navy, Dreadnought being the 281st submarine to be built at Barrow. The building of the reactor was placed with Rolls Royce.
An agreement was struck between Earl Mountbatten and the Americans to purchase a complete nuclear power plant including the reactor, from the Americans after the development of the reactor at Dounreay had proved to be too slow.
The plant would be of the same type as used in USS Skipjack this meant in reality that the front half of Dreadnought would be British and the after part would be wholly American. Dreadnought retained diesel engines, snort mast and batteries as an auxiliary power for manoeuvring on the surface and for short passages.
Geared steam turbines, one shaft.
Emergency drive batteries and electric motor.