The proposal starts from the engineering difficulty of guaranteeing continuous deterrent patrols with only three boats. A five-hull class would normally keep three in the ballistic-missile role and two fitted as SSGNs with removable cruise-missile modules. If an SSBN were damaged or unavailable, one of the conventional boats could be converted back to sustain the patrol cycle. Common hulls would also preserve construction continuity while yielding a separate long-range strike force.
Notable Point · 4:57:40-4:59:26
A five-boat British SSBN and SSGN force
Five common submarines, with two carrying removable cruise-missile inserts, could preserve deterrent availability while adding conventional strike capacity.