Really, I don't.
Over several weekends-when there was fuck all in terms of movies, TV, etc, etc, etc, about eight years ago (I checked my purchase receipt), I picked up a copy of the GURPS Vehicle Builder for GURPS Vehicles. This was back in the days of GURPS 3rd Edition Revised, when there wasn't so much fear about superscience technology and the game had math out the ears.
Anyways, I was playing around with the Vehicle Builder and eventually...I built a starship frigate.
It was a TL 10 frigate, all reactionless drives with a hyperdrive. It had vectored thrust and was streamlined and could take off and land from a planet, and could carry enough passengers to count as carrying a reinforced platoon of Marines. Spinal particle beam cannon, backed up by four 350mm missile tubes, four light xaser cannons, and six point defense xasers.
From this ship, which I eventually named the Adams-class frigate, I started to work out...a fleet structure.
I told you I had no life.
Anyways, eventually, I built a fleet. Then, I built another. I built a third. And a fourth.
And then, the hard drive on my Windows XP machine decided to cut it's own metaphysical belly open and I lost all the ships (most of my backups were photos-long story).
So, that idea died.
Until about a few days ago, when I read a review on GURPS Spaceships for GURPS 4th Edition. And, found on an old, old, OLD flash drive the concept notes for the ships I'd built. Sadly, not the ships themselves (which I might have to do again), but the notes were interesting.
The first part of the notes (in condensed form)-
- The game universe was built around pretty much bog-standard GURPS tech progression, starting off at TL 10. Hyperdrives and reactionless thrusters were the norm. The history I had worked out had gone up to about TL 12 and about 300 or so years (which isn't that long in a human society where longevity treatments can give lifespans of up to 150+ years).
- The major power blocs are the Concordiat (human, several alien races), the Kaa Imperium (Kaa and slaves), the Engai Moot (Engai territory), and several small "pocket vest" kingdoms. All the alien races came from GURPS Aliens.
- There had been a LOT of jockeying for territory and power between the Concordiat and the Imperium. By the time TL 10 came around, there had been three "frontier wars", and the ships built in the game had fought the fourth.
- The Kaa Imperium is mostly TL 9, except in drives, stealth (TL 11), and some other technologies.
- Ship hulls were the "classic" progression for FTL hulls-corvette, frigate, destroyer, light cruiser, heavy cruiser, battle cruiser, battle ship, dreadnought, super-dreadnought and finally monitors.
- The Concordiat had essentially a two-tier Navy during the TL 10 era-Patrol Fleet which didn't have anything bigger than a battleship, and Battle Fleet, which went all the way up to monitors.
- All Fleet ships-from the smallest to the largest-are "1/1" capable at a minimum-able to do 1G in acceleration, and l light year a day in FTL.
- Patrol Fleet ships tended to be more lightly armed, but had more space for small Marine detachments, LARGE medical bays, and anything smaller than a heavy cruiser could land and take off from Earth by itself.
- Battle Fleet was the reverse. Destroyers and smaller could land on planets, but they tended to carry more weapons and heavier weapons.
- No space fighters. Battle riders-warships that didn't have FTL-were used, but the survival ability of a fighter was non-existent in this universe. Concordiat battle riders were all sentient AI drones (fifteen years of service meant full citizenship and paying off their creation costs), Kaa battle riders were what filled the destroyer-and-smaller niches in their fleet, and had biological crews.
- Weapons-the Concordiat was built around spinal particle beam cannons and missiles, with xasers (x-ray laser) cannons as backups. Concordiat ships had three sizes of missiles-350mm, 500mm, and 750mm. At TL 10, the warhead commonly used was a HUGE HEAT round, followed by a nuclear weapon. By TL 11, nukes were common (and, I would have built every single nuclear missile as a bomb-pumped weapon, but the Vehicle Builder tended to choke on that). I built the missiles as vehicles themselves-power cells with a small nuclear power unit so the missiles could be used as mines if needed.
Point-defense was provided by a small xaser cannon that had UNGODLY rate of fire...
- Concordiat ships of heavy cruiser and larger mounted particle beam cannons on turrets, as well. The heavy cruiser mounted essentially the frigate's spinal particle beam cannon, and it went up from there. As well, ships that were battleship and larger mounted turret-mounted missile launchers for 350mm missiles as anti-battle rider weapons.
- Battle riders had a dedicated tender/carrier ship in the Concordiat Navy, and were also carried by ships of dreadnought or larger in eight-ship groups. They were also docked in huge numbers at anchorages (a term used by the Fleet for orbital elevators that were almost common on every major Concordiat world) for planetary defense.
- There was a dedicated Marine transport that could haul a single reinforced Marine Expeditionary Unit, and drop it with transports in a single drop. Built the shuttles (three-a squad-sized lander/gunship, a company-sized lander, and a vehicle transport), tanks, AFVs, powered armor...
- And, then, we got into quirks...a good example was the Joshua-class battleship, which was built around a TL 10 Heavy Advanced framework (most other Concordiat ships were built on Heavy Very Expensive frames). Why? They had partially gone through the first flight run of the ship back when ships were built with TL 9 reactionless drives for low-thrust operations and pulse fusion engines for high-maneuverability combat. TL 10 drives surprised everyone and they retrofitted the Joshua-class with the new drives.
When the Joshua-class was retired, the Engai bought the hulls, stripped them down to the framework, and built their own warships on top of them. In fact, they pretty much built their own TL 13 version of the ship a few decades later.