Swiftsure Class Submarine - Design History

Design History

The Dreadnought, Valiant and Churchill classes all had a "whale-shaped hull", of "near-perfect streamlining giving maximum underwater efficiency". The hulls were of British design, "based on the pioneering work of the US Navy in Skipjack and Albacore." The hull of the Swiftsure was a different shape and maintained its diameter for a much greater length than previous classes. Compared with the Valiants the Swiftsures were 13 feet "shorter with a fuller form, with the fore-planes set further forward, with one less torpedo tube and with a deeper diving depth."

A second major change was in propulsion. Rather than the seven/nine-bladed propeller used by the previous classes, all but the first of the Swiftsure-class submarines used a shrouded pump-jet propulsor. The prototype propulsor had powered the Churchill. It is not clear why the Swiftsure was the only one of the class not fitted with a propulsor. The propulsor was perhaps as much as 50% more efficient than a propeller, producing the same speed at lower revolutions, thus reducing the noise signature. In addition all pipework connections to equipment on the main machinery raft had expansion/flexible coupling connections, which also reduced noise. The US Navy secured a licence to copy the main shaft flexible coupling arrangement in US-built submarines.