From a post to ALT.BOOKS.DAVID-WEBER dated October 18, 1998:

Missile pod launchers

    The pod launcher incorporates grav drivers which, while less powerful than those of a "standard" shipboard launcher, are still far from trivial. This is one reason for the pod's size. The shipboard broadside launcher has to kick a missile out through the widest part of a ship's wedge and is designed to do it very quickly while simultaneously spreading missiles which have wedges of their own that are around 10 klicks wide far enough apart to avoid wedge fratricide. One reason the pod is designed to be deployed astern of the firing ship is to get it outside the firing ship's wedge. That means that all it has to do is spread the missiles wide enough to prevent them from killing one another. This is done with a considerably weaker (lighter) grav driver which was originally developed by Sonja Hemphill & Co. in an attempt to produce a lighter box launcher for conventional LACs. They reasoned that since a LAC's wedge was so much narrower than a conventional warship's, a lower initial impetus would suffice. They were more or less correct, but only for LACs even smaller than the Shrike... where they quickly got into the problem that they had too small an egg shell to hold their hammer. Which is why the pod was developed instead of a new LAC with better box launchers. The grav drivers actually incorporated in the pod are primarily intended to kick the missiles out and spread them sufficiently for their onboard drives to cut in and take over. There is actually a somewhat longer delay between launch initiation and impeller ignition aboard these missiles than for standard launchers because they move much more slowly to clear the perimeters of one another's wedges before lighting off.