[Spaceships] Ship sizes and other categories (cruiser, battleship etc.)?

[Ulzgoroth]

Originally Posted by vicky_molokh

Well, we know that SM+4 and +5 are fighters. Is it possible to work out the proportions from there?

Heck, we don't even know that. Going by length, the Fury interceptor in Battlefleet Gothic is SM+7 to SM+9. And class size drift is quite real, even insofar as the classes have consistent meanings between navies at all.

And of course in SF, the names can be all over the place. As noted, the B5 Earth Alliance navy considers uses 'destroyer' to refer to a huge primary combatant. But some other B5 navies seem to have destroyers that are fairly small light warships.

[Voren]

Originally Posted by vicky_molokh

Well, we know that SM+4 and +5 are fighters. Is it possible to work out the proportions from there?

Or ASATs, attack drones, AKVs, MAVs, etc, etc, etc...

Really, the terminology is all quite relative to the setting. One setting's heavy cruiser is another setting's Light Space Dominance Vehicle.

The real-world history of the term 'frigate' is the classic example of how relative this all is. Long range, independent patrol/raiding ship? Small convoy escort? Large nuclear powered guided missile ship? Whose frigate? When?

[Lord Azagthoth]

Ship size varies over time. Depending on the needs.

Ship class varies by nation. One nation sets the class name by the first ship that's built (aka USA, UFP) but another nation on function or even size.

You can use these systems for different races of your space campaign. One race uses the USA classes, and another race the Dutch naval classes.
Even in Sci-Fi/Fa they use one or another of these naming systems.

A good way to start is to know what the max ship SM is for a certain nation and start from there.

[SMilway]

i've found its usually more helpful to catergorise ships by the their function
E.g. in a modern navy, a destroyer is your primary surface combatant and air defense vessel, a frigate is your primary escort and ASW vessel, a carrier is for launching and recovering aircraft, a cruiser is a warship and primary long range combatant. these designations are all relative, and the fact that a frigate is traditionally smaller than a destroyer is moot.
you could easily have a cruiser that is much bigger than a battleship because it is designed to operate away from home for a long time on its own (original meaning of a cruiser) and it needs to carry more fuel/supplies/etc.

[David Johnston2]

Originally Posted by vicky_molokh

Greetings, all!

Anybody got a consistent categorization of spaceships based on size and function? IMO a actual class names are a more appropriate way to refer to ships in-character than by linear measurement or SM.

Thanks in advance!

Size is only important insofar as comparing ships to other ships that serve the same function. First someone will design a ship intended to operate on it's own for extended periods to, say, explore or attack enemy commerce. Such a ship could be any size and have a crew of 12 or 1200, but because of its function, it's called a "Cruiser" Then the SM smaller version of the design will be called a "Light Cruiser" and the SM higher will be called a "Battle Cruiser".

I've designed SM 10 fighters, defined as such because they had only one crewmember, short term life support, limited operating range, and rapidfire beam weapons.

[Tyneras]

This was touched on once, but I can't find the post, so I will take the text directly from my GURPS Useful Stuff file. This might or might not be what you are looking for, I'm not sure.

David L. Pulver wrote:

If you are building spaceships that behave like WWII naval ships, this is good. If you are building ones that behave like modern naval ships or modern airplanes, it's usually "one shot, one kill" so you may want to buy ECM and smaller batteries for survivability. For example, a major battery in a turret in the center or rear of the ship with the VERY RAPID FIRE option nicely represent a Phalanx-type gatling gun equivalent - good for stopping missiles.

5. SM+5 = 30 tons. A good-sized fighter. At 30 tons, this is the same mass as a fully-loaded F-15E or F-22 (both are 40 tons max takeoff).
SM+6 = 100 tons. I use this for heavy fighters. Note that a B-2 bomber is about 180 tons. This is the same mass a light patrol or torpedo boat.
SM+7 = 300 tons. I use this for small scout ships or a lvery light freighter like a Firefly or maybe a Millenium Falcon, although they might also be +8.
SM+8 = 1000 tons. This is about the same mass as a small corvette or frigate, or a typical tramp freighter.
SM+9 = 3000 tons. This is about average for frigate or destroyer today, or a large tramp freighter.
SM+10 = 10,000 tons. This is good for a modern-day cruiser warship or a large freighter.
SM+11 = 30,000 tons. This is equivalent to a modern heavy cruiser or a light battleship.
SM+12 = 100,000 tons. This is about equivalent to the largest aircraft carriers in use today.
SM+13 = 300,000 tons. This is equivalent to the largest oil supertankers in use. If you're a Traveller fan, the Azhanti High LIghtning is about this size.
SM+14 = 1,000,000 tons. Ten times the mass of the US Navy's biggest aircraft carrier, this is good for a big super dreadnought. It's also in the same range of mass of large SF space stations - "Babylon 5 - 500,000 tons of spinning steel..."
SM+15 = 3,000,000 tons. This is good for very large dreadnoughts or space stations.
You can extrapolate upward for even larger vessels, like some ships in star wars.

[Darekun]

For IC sizes, I'd just go with the tonnage. Spaceships are already referred to that way in some sci fi, and since mass matters so much in space(no drag to care about area, heat dissipation mainly by specialized structures, etc), it makes sense.

[IrishRover]

I'm going from a World War One/Two perspective here. Ship sizes grew rapidly through the late 19th/early 20th century, but the type was based on the ship's role. A modernized predreadnought in World War Two would still be a batleship, even if it's only the size of a large cruiser, because of its capabilities--somewhat slow, heavy armor, and big guns. It would likely thrash a modern cruiser--even if the cruiser was the same size--because it's better armored and with biger guns. But--the crusier could carry out cruiser missions, and the predreadnought couldn't. To me, mission is the important thing.

Incidently, "Batlecruiser" in scince fiction doesn't usually mean the same thing as in reality. A real world battlecruiser was as big--or bigger!--than a dreadnought of the same generation, with more speed, the same size (but possibly a bit fewer) guns, and lighter armor.

I'd say that you should, if using old earth terminology, look at what the ship is doing. If you aren't using naval terminology from long ago, "Destroyer" does suggest something that can obliterate anything in reach. (Destroyer originally was "torpedo boat destroyer," a ship that could eat torpedo boats for lunch.)

[Langy]

I'm going from a World War One/Two perspective here. Ship sizes grew rapidly through the late 19th/early 20th century, but the type was based on the ship's role. A modernized predreadnought in World War Two would still be a batleship, even if it's only the size of a large cruiser, because of its capabilities--somewhat slow, heavy armor, and big guns. It would likely thrash a modern cruiser--even if the cruiser was the same size--because it's better armored and with biger guns. But--the crusier could carry out cruiser missions, and the predreadnought couldn't. To me, mission is the important thing.

The modern cruiser would probably be able to destroy the old-style predreadnought in a single hit from much farther away from the predreadnought's weapons can fire - one of the many benefits of ship-to-ship missiles and higher technology.

[SuedodeuS]

The old Starships of the Galaxy (for the d20 Star Wars RPG) had three classifications: Starfighter, Space Transport, and Capital Ship. It was mostly based on length rather than mass, but these three map approximately to SM+2 (o.O) to SM+6, SM+6 to SM+10, and SM+10 up, respectively. This is based on the lengths - SotG also gave masses, but these tended to be rather low (the progression was SM+2 to SM+5, SM+6 to SM+7, and SM+7 up).

The Serenity RPG has some more classifications. Shuttles are halfway between SM+4 and SM+5, gunships are SM+5, transports range between SM+6 and SM+12, patrol boats are SM+9, cruisers are SM+15. Warships are noted as being somewhere between 100,000 and 1,000,000 tons, so somewhere between SM+13 and SM+15. The ships are classified primarily by role, sometimes with a nod to size (small transport, large transport, etc).

In general, I think classification by role, with a nod to size (either with a description like "large," or an approximate tonnage), is the way to go. For common designs, people probably won't refer to them by classification, but rather by the design - the Serenity is a medium transport (or a 3,000-ton transport), but a lot of people would just call it a Firefly-class.