Savage Worlds has a Sci-Fi companion (hereafter, SW SFC)...
It has some passable (but cinematic rather than simulational) ship rules. their terminology is bloody annoying to anyone versed in the terminology of the US Navy before Korea. (A terminology which has been largely inherited into Traveller.)
THe size categories are interesting...
| Size Category | Ship types |
| World Killer | MegaDreadnoughts, Megacarriers, Colony Ships |
| Leviathan | Superdreadnoughts, Supercarriers, Settlement ships |
| Behemoth | Dreadnoughts, Invasion Carriers |
| Gargantuan | Battleships, Strike Carriers |
| Giant | Cruisers, Destroyers, Light Dreadnoughts, Troop Ships |
| Huge | Bulk freighters, Corvettes, Light Frigates |
| Large | Cutters, Scientific exploration vessels, small freighters |
| Medium | Bombers, Large shuttles, Scout Ships |
| Small | Fighters, Shuttles |
(Most Sci Fi authors use a late 19th C to WW2 derived model:
SD, DN, BB, BC, CA, CL, DD, FF, Corvette, Escort
or
BB, DN, BC, CA, CM, CL, DD, FF, Cutter
A few have used the US "Frigate = Light Cruiser except for the reporting to the appropriations committee."
It uses "Superstructure" in an odd way, as well.