Two parts of the Triplanetary setting required particular work in the design stage, given my plan to write military science-fiction. The first was the rank structure, which I described in a previous post, and the second was the fleet itself; the warships and auxiliaries that would make up the Triplanetary Fleet. That required working out the details of space warfare, something that should have been difficult but was made far simpler through the use of the Atomic Rockets website...which anyone writing science fiction that pretends to any level of accuracy really needs to visit.
I quickly decided that missiles and lasers would be the primary weapons; missiles certainly, and laser technology is improving to the point that they will certainly be viable weapons as well. Both weapons have advantages and flaws; missiles are extremely adaptable, able to switch from target to target, to home in on a target, but they take time to get there; that gives the enemy time to react, to unleash his countermeasures – which by this time means 'combat hacking', primarily. No stealth in space, remember! (Besides, combat hacking is kinda cool.) Lasers are huge. Alamo's array is a quarter-mile long, and has radiators a mile wide that have to be extended. It takes a lot of power, but it hits instantly – at least for the purposes of space warfare. The only defence is not to be there.
So that's attack. For defence, well, armour would have some merit but is heavy. A better strategy is to not be where the enemy is attacking, which means a lot of manoeuvrability. We're not talking ducking and weaving around asteroids here, we're talking moving to the left to dodge the laser blast. (Which means Han Solo really does know some manoeuvres!) The other primary factor will be electronic warfare. A great hacker could take over an enemy computer system; more realistically he'll be trying to screw up approaching missiles, set-off any auto-destruct, explode them early, send them off course...anything that works.
Starting with actual warships, I broke up the classifications into two types – those capable of FTL travel and those not. Now, the names of ship classes have varied wildly throughout history - we've seen the destroyer go from a torpedo boat to a major fleet asset in the course of a century, after all – so I was trying to work out what such ships would be called in the future, based on the roles they would be serving. My starting point – because it was the first thing I nailed down – was that there would be a 'battlecruiser' class.
In-system, there is going to be a need for a workhorse. A ship which has the job of holding that asteroid, protecting that space station, guarding that convoy. In modern parlance, the frigate does a lot of that sort of work, and it seemed a logical term for such a ship; such vessels would have to be stronger than classical frigates, however, because of the need to go toe-to-toe with larger ships, hence the frigate becomes an in-system warship – the in-system warship, though there are variations. I've already introduced the 'fast frigate', designed for speed rather than endurance, as an example.
When it comes to FTL, the job required will be two-fold. Ships that are effectively FTL-capable frigates for patrol work, for escort duty and the like, and others that are required to range far more widely, conducting long-range scouting missions, and more importantly, to attack convoys. We're talking the Graf Spee or the Emden here, vessels designed to go far and hit targets on their commander's discretion. Long-range action? Sounds like the cruiser to me, and there are two variations. One designed to operate with support, which doesn't need long-range as it will be working from a station or with a convoy, and that is the basic cruiser. The independent variant is, of course, the Battlecruiser. (At the start of the series, the Triplanetary Confederation is in the interesting position of only having Battlecruisers, a legacy of the war – constructing a cruiser class is an early element of the expansion of the fleet.)
At the halfway-house between warship and auxiliary is the carrier. I actually see fighters as a tool of fleet warfare very much as an interim measure, not something that necessarily lasts in the line, so long-term their role boils down to a movable space station, capable of holding orbital space with the assistance of a frigate or cruiser to provide the heavy support. That means it's going to look a lot like a space station with engines bolted onto the back; if the fighters are doing their job, then it doesn't need to go to war itself. This also means marines – yes, ultimately I see the 'Commando Carrier' as the only carrier class in deep-space service. It makes sense that they serve as troop transports as well, after all, they are designed to support large numbers of the auxiliary craft they require.
Given my assumption that fabricators analogous to our current 3D printers will provide an increasingly level of autonomy, I see auxiliaries coming in two primary types; tankers and tenders. The former will be critical, keeping ships supplied with fuel on long-range patrols, and likely also with the ability to mine and process fuel. It makes sense to provide that capability, but wouldn't necessarily be ubiquitous throughout the fleet. I can see 'Escort Tankers' and 'Expeditionary Tankers' being commissioned. Tenders, on the other hand, have two jobs – to move Frigates from one system to another, and to provide engineering support to damaged ships. Again, one ship to do both jobs is logical enough, given the expense of each ship.
What other classes might there be? Well, there might be call for a Battleship some day, a large cruiser-type designed to work with a fleet train, but massively armed with missile batteries and laser arrays. That would require serious opposition, though, and at present, it is not evident in the setting. Other auxiliary types such as hospital or even entertainment ships might be part of extended fleet trains, as well as fighter-repair craft, though I see that largely being done on the carriers themselves. All that is for the future, though...