Before the Polaris missile was developed, the US Navy studied several approaches to using submarines to launch ballistic missiles. An early idea was taken directly from WWII Germany… store Jupiter IRBMs in special canisters, towed behind subs. These would be partially flooded whe  the subs got to the launch site; this would cause the canister to tip up 90 degrees. A few hours later, the liquid fueled Jupiter would be ready to launch. Additionally, there was some thought put into the idea of installing the Jupiter vertically within subs. But nobody much liked the idea of large liquid propellant missiles in submarines. So by April 1956 the idea then moved to solid propellant rockets designed to emulate the Jupiter, carrying the same payload on more or less the same trajectory. The missile would be fatter than the standard Jupiter, but also shorter. Still, at ten feet in diameter and 41 feet in length, it was a very large missile, and only four could be carried within the body of the sub and the greatly extended sail. Fortunately, within a few months the Polaris design came on the scene, a much smaller missile made possible by both a smaller warhead and higher energy density double-base solid propellant.

Lockheed illustration.