So, just to complicate matters further, I do both size/function designation. The modern US Navy does it the same way. In actuality, ship naming conventions were not very static in historical navies.
Great example of this would be the age of sail. While ship types were defined by role, they we often designated by sailing rig. So, that would be like designating Aurora ships by engine type. Examples would be Barque, Brig, or Schooners.
Then you have the "class" system that arises in the 18th century. Ships of the line, as the Royal Navy rated them, were rated by decks, and number of guns. 1st Rate ships, were big ships, with mulitiple decks, and a large number of guns. As the times changed, 1st Rate ships, that were still in service, were down rated. The system got confusing, as ships less than 6th rate (still often called frigates), were "unrated" and generically called "sloops".
So in this case, my ships are broken out something like this;
Military
Fighter (pretty self explanatory), can be Light, Medium, or Heavy based on size and loadout.
FAC- short ranged, high speed, low endurance system based attack craft. Could be missile or gun armed
Gunboat- long ranged, longer duration small combatants (usually in the 1000 ton range, but have multi-month endurance)
CT- Corvette- Light patrol craft, system based, or lightweight long endurance warp point guards. Usually 5000 tons or less.
FF- Frigate- Patrol craft, generally smaller than destroyers, usually around 6,000 tons or so. Multi-role, designed for solo or small squadron ops, and cheap. Could be missile armed, but usually gun armed.
DD- Destroyer, fleet combatant, around 8,000 tons or so, gun armed. Single role ships.
DDG- Missile destroyer
ES- Escort- smaller destroyer sized or less anti-missile ships
CE- Escort cruiser, fleet escort, usually light cruiser sized or a bit larger
CL- Light cruiser, usually 9,000 tons or more, smallest capital ship for a fleet leader role
CA- Cruiser, gun armed, 12,000 tons or more
CG- Cruiser, missile armed, 12,000 tons or more
BC- Battlecruiser, could be either gun or missile armed, 15,000 to 18,000 tons. BC's are optimized for speed. I usually use these as the center of a gun fleet.
BB- Battleship, gun armed, 18,000 tons or so,
BBG- Battleship, missile armed, 18,000 tons and up
CVE- Escort carrier, usually a dedicated system defense or interdiction carrier. These are used to get some fighters into a system for long durations. Not for fleet use.
CVL- Light carrier, smaller than the usual fleet carrier, usually 1 to 2 squadrons, meant for smaller fleets or high speed fleets.
CV- Carrier, usually 4 to 5 squadrons, standard fleet carrier
CVH- Heavy carrier, 5 or more squadrons, major fleet combatant, usually command ship for the fleet, space control ship
CVA- Assault carrier, heavily armed and armored carrier meant to go in a warp point assault
In my case, patrol ships, or ships operating alone, tend to be multi-role capable. So, for example, my patrol frigates would be fast, gun armed, but have full sensors. Fleet warships are optimized for specific roles, and don't waste space on unnecessary systems.
As my ships change, the roles and designations may change as well. Especially as ships refit. I also tend to reclass ships as they are rolled out of main line service, and are not slated for refit.
