In between working on 3A2 and my current challenge entry I decided to pump out a quick rendition of what I view as one of the sillier submarines from the cold war. The USAF's MX carrying small submarine, one of the more grounded concepts out of the numerous proposals for basing the new MX Missile . Proposed in the early 80s with entry into service expected between 1992 and 1994, the basic concept was for a small diesel-electric submarine* carrying 4 missiles stored horizontally in steel canisters. On launch hatches would open and latches released. The canisters would then float to the surface where the missiles would then be launched.
Technical Details are rather sparse and I suspect little,if any real engineering work was done beyond basic sketches of the layout. Most of the work done seems to have focused on the pros/cons of basing the missile this way. Things like how it would affect missile accuracy, the vulnerability of the submarines to soviet attack, how many subs would need to be at sea at a time and where would the subs be based from.
Overall if you're thinking that this seems to be a worse version of Trident, you're not wrong. I suspect that this, along with many of the other proposed MX basing schemes was put forward in order to make some of the USAF's preferred option, multiple protective shelter and deep underground basing, more attractive by comparison. In the end, when the MX missile finally entered service as the Peacekeeper, the USAF eventually would ended up sticking the then missiles into old Titan II silos.
*Nuclear electric was considered an option, but diesel electric seems to have been the preferred choice.