Also, reportedly Soviet ballistic missiles were/are less accurate than US ones, so they compensated by having a bigger bang, in turn needing a bigger missile to launch it.
Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail.
> Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail.
The US used to have something like this in the Regulus, their intended launcher (the Grayback-class) essentially had hangars.
The great advantage of SLBMs is that the vertical mounting and a good enough launch sequence means you don't have to surface to launch: https://youtu.be/sUlXty69-Y8
Another solution would be to do what the North Korean missile subs, putting the missile tubes in the (lengthened) sail.