Editing Swiftsure-class submarine (section)

==Design history==
The {{HMS|Dreadnought|S101|2}}, {{sclass|Valiant|submarine|5}} and {{sclass|Churchill|submarine|5}} classes all had a [[Teardrop hull|"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 {{sclass|Skipjack|submarine|5}} and {{USS|Albacore|AGSS-569|2}}."<ref>Blackman, Raymond VB, ''Jane's Fighting Ships, 1966–67'', pub Sampson Low Marston & Co Ltd, 1966, p. 279.</ref> The hull of the ''Swiftsure'' class was a different shape and maintained its diameter for a much greater length than previous classes.<ref name=Janes1982p546Cost/> Compared with the ''Valiant''s the ''Swiftsure''s were {{convert|13|ft|m|abbr=on}}<ref name=Hoolp184>Hool, Jack, and Nutter, Keith, ''Damned Un-English Machines, a history of Barrow-built submarines'', pub Tempus, 2003, {{ISBN|0-7524-2781-4}} pages 181–4.</ref> "shorter with a fuller form, with the fore-planes set further forward, with one less torpedo tube and with a deeper diving depth."<ref name=Janes1982p546Cost/>

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.<ref name=Hoolp184/> The prototype propulsor had powered {{HMS|Churchill|S46|2}}.<ref>Hool, Jack, and Nutter, Keith, ''Damned Un-English Machines, a history of Barrow-built submarines'', pub Tempus, 2003, {{ISBN|0-7524-2781-4}} page 180.</ref> It is not clear why {{HMS|Swiftsure|S126|2}} was the only one of the class not fitted with a propulsor.<ref name=Hoolp184/> 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.<ref name=Hoolp184/>