Just to clear up a few misconceptions that may have crept in:
David Weber, alas, has done me no favors by convincing much of the SF-reading world that the standard interstellar badass is the dreadnought.
And, yes, you may remember me saying “it sure would be nice to build nothing except dreadnoughts [for ships-of-the-plane]” back when we discussed ship types, but what I did not say is that if they did, they wouldn’t be dreadnoughts. They’d be battleships, because the modal ship classes for engaging in big set-piece space battles are always designated as battleships. Says so right in the name. Battle. Ship.
Or, to put it another way, there are a lot fewer dreadnoughts than there are battleships. (And a lot more cruisers than there are battleships, for that matter, because most missions don’t have any major fleet engagements in them. But that’s another story, already told.) This is principally for economic reasons: when you examine the requirements for a ship of the plane, the battleship sits right at the bang/buck sweet spot, so that’s what you build.
A dreadnought (and to an even greater extent, a superdreadnought) has four virtues, which is why they’re built at all:
- It benefits in internal space from volume increasing faster than surface area, which makes it a convenient class to carry extra stuff, from complete flagship suites through shipyard-class repair facilities for its cohorts and prisoner-of-war blocks to all that is required for the many, many specialized variants on the books.
- It can afford a hell of a lot of extra armoring, so you are significantly less likely to get your admiral shot off and your fleet coordination suffering if you give him a DN to ride around in.
- It can mount a Really Big Gun of the kind you’ll rarely need to use, but you might miss if you didn’t have any of in your plane of battle.
- It’s bloody terrifying. When naval architects are told to draw up plans for a DN or SD, the unspoken requirement is that it dominate the battlespace like Conan the Barbarian at a convention of preadolescent pacifists: it dreads nothing, and everything dreads it.
So there aren’t all that many in service, relatively speaking. There don’t have to be – say, speaking non-canonically and off the back of the envelope, eight squadrons in the Capital Fleet (mostly in the Sixth Flotilla, which is the IN’s heavy-hitting force), four squadrons in Home Fleet, two for Field Fleet Spinward (which borders on the Seam), and one for each of the other field fleets: say, 228 in total, not counting specialist classes and the reserve.
You can assume at least four times that in BBs.