Besides, If you use hollywood sized space all you have to do is
use the meters per second when it says miles per second and
then use 'common sense'...
I've been lying to you. Cinematic Spaceship rules do that. They give you the impression of scale and size that simply are not true. Things don't match up the way you think. For example, it seems pretty reasonable that starfighters can hug close to a dreadnought, and then spend a few rounds fighting off turrets as they fly to the back of the ship and then shoot it up. That makes sense, intuitively. It's also complete nonsense.
Let me show you what I mean.
Ships to Scale
Somewhat famously, I imagine, there's a website by Jeff Russel where he puts ships to scale. A very useful resource. I've used it to create the images below.
A starfighter is about SM +5, about 15 yards long, and about 7-8 times the size of a person. For a "person" I have Maria from Metropolis, and for a Starfighter, I have an X-wing. I apologize for the blurriness (I had to scale the x-wing up). But this is about what you expect: A fighter is about the size of, you know, a jet fighter. A person can figt in the cockpit and an engine is about as big as a person.
A corvette is about 50 yards long, or about 3 times the length of a fighter. The Serenity below is about 60 yards, putting it between an SM+9 corvette, like the Tiger, and an SM +8 corvette like the Dark Horse or the Taj Mahal.
I've removed Maria, but you can see where you could obviously put quite a few people inside, for example, the bridge of the Serenity. You can also see how it's much larger than a fighter, but not vastly larger. The Tie-Interceptor, by the way, is SM +4 and about 10 meters long. It's mostly wing: the bulk of the ship is that little ball, which is much smaller than the engines and the guns of the X-wing.
I'm going to skip capital ships and jump straight to dreadnoughts: An empire class dreandought is 500 yards long, ten times the length of a corvette like the Serenity. It's not actually nearly as big as a Star Destroyer (I used a ship from Farscape to represent the dreadnought), which is three times longer than an Empire-Class dreadnought. But still, you get an idea of the scale of a Dreadnought: If you sat it on the skylines of New York, it would be one of the tallest buildings there.
The dreadnought is clearly huge compared to a fighter, which would be but a few pixels down in the corner, a fraction of the size of the Serenity, which is already minute. So far so good... only ships in GURPS Spaceships (and likely space) move really fast. In my version of space combat, I've focused entirely on abstractions, but remember that the tactical mass combat system I used had 100-mile hexes. The Starhawk in that fight crossed 10 hexes in the first turn... in 20 seconds, it covered over a third of the continental US, and it did so incidentally, while trying to slow down.
If we used Boost Drives (a good idea, by the way), then the Starhawk would fly at around 40 miles per second. While it was hugging the Empire-Class dreadnought, assuming that the dreadnought was standing still, then during a 20-second turn, if the starhawk was going from one long end to the other, it would cross that distance in ~0.0075 seconds (back of the envelope calculations). Or, said differently, it would have to circle the dreadnought 2400 times per 20-second turn to stay close enough to "hug" it. Twenty-four hundred times! This would be eased a bit if we assume that the dreadnought is also moving at 40-miles per second, and the difference we concern ourself with is the speed at which they differ, so that one seems to be standing still compared to the other... but if we do that, then one ship, with 50gs of acceleration, can suddenly shift gears and be moving in a completely different direction (50gs is an acceleration of acceleration is around 500 meters per second per second. It would be like having a move of 500, where you could constantly add another 500 every turn. It looks like the picture to the right. Incidentally, it turns out you can survive these accelerations, though note that the starfighters accelerate 4 times a fast as this), which explains why remaining engaged is so futile in actual, realistic space combat... because it is futile. What I've done to create a workable space opera combat system is whimsically lie to you and use abstractions in the system to cover it up. Of course, you don't have to think too hard about how space combat should actually work... just realize that it would look nothing like my system. If players demand that it make sense, use the advice Ericthered gives above. At 40 meters per second, a fighter will take about 20 seconds to get around behind a dreadnought while hugging close to it.
The Scale of Infrastructure
One thing I've noticed playing Star Wars games, and watching Star Wars (especially the non-prequel games) is how much time characters spend running around inside the internal infrastructure of ships and stations. In Star Trek, characters regularly trod long hallways built for people, and occassionally crawl in "Jeffries tubes", but in Star Wars, they end up in grey, desloate corridors with walkways over titanic arrays of power cables or pipes or god knows what. I find the Star Wars approach entirely realistic.
The Scale of a Workspace
How large is a workspace? GURPS Spaceships doesn't really work with volumes, but we can make some order of magnitude estimates on the back of an envelop. The lengths given in GURPS Spaceships represent shapes that are longer than they are wide or tall, but a sphere would be less than half that size. So, let's estimate that a cube would be about half the given length, roughly. This allows us to calculate a volume: the cube of half the listed length. A single system is 1/20th of the ship, and thus takes up about 1/20th of this volume. Engine rooms provide a single work space for ships smaller than SM +10. If we look at the volume occupied by an Engine room (ships smaller than SM +10), what do I get?
I ran some numbers on an excel sheet, and what I came to about 50 cubic meters. If we laid that out as a single-story room, how much floor space would it have? Roughly 150 square feet. What does a 150-square-foot apartment look like?.
That's not very big. Of course, this varies: This is almost more space than en entire SM+5 ship even has, so obviously an engine room (and thus a workspace) in an SM+5 ship is smaller than in an SM +8 ship That said, we have an actual example of an Engine room in Firefly, as the Serenity is SM +8 to SM+9 (giving it between 1 and 2 workspaces). It looks like this:
Which, to me, looks pretty close to the picture above. This suggests that my numbers aren't too far off the mark.
The Scale of other systems
What about a habitat? Using the same spreadsheet, I come to the same size as a workspace, which makes sense: you could fit two people in that apartment pretty comfortably, four if you squeezed them together, and a single person living in an apartment twice that size is going to be quite comfortable.
What about armor? A ship is often dominated by its armor? Well, a battleship has armor that looks something like this:
An empire-class dreadnought is about 30 times larger than a battleship but it's also not nearly as well-armored, and it has highly advanced armor, so it might have armor about twice as thick as that. That means that the armor doesn't really occupy that much volume (which tracks with a pyramid article that suggests reducing the size of a spaceship if it's mostly armor). Habitats and fuel tanks and cargo space, etc, will almost certainly take up more volume than the armor does. Thus, floor plans that show a ship as mostly walkways instead of mostly armor aren't wrong: By weight, a ship might mostly be armor, but by volume it's probably mostly walkways.
Inside a Dreadnought
So what does an Empire-Class dreadnought look like, if you're crawling around inside of one?
The Empire-Class dreadnought is 500 yards long, so roughly 150 yards of its length is each facing (rear, center, front). More of the front is armor than the back or center, which can be explained by a tapering construction. It's central spine is dominated by a spinal cannon that is, of course, about 500 yards long. We could make it longer (say, 700 yards) by assuming that it's considerably longer than it is wide (which is reasonable). It also has 300 workspaces, which is about 1500 cubic yards of workspace, leaving a tube about 30-35 yards across and tall, or a tube (full of gun and machinery and safeties and breakers and etc) about 100 feet tall and 100 feet across, that extends for 700 yards, all to fire a single cannon. Most items (such as engine or star drives) will have similiar dimensions (though, obviously, will be shorter as they take up 1/3 of the ships length, rather than the whole thing). The workspaces themselves, work out to the equivalent of 300 150-square-foot apartments worth of hallways, consoles, store rooms, tool closets, etc.
If we break everything down into "150 square-foot apartment-sized rooms," then we find that Empire-class dreadnought has 2600 "rooms" in living space, 250 in "offices and facilities" (including a 100 "room" hospital), 3810 "rooms" in industrial space, workspaces or lifesupport, 550 "rooms" of cargo space, and 6000 rooms of "hangar," and 40 rooms worth of control stations.
- 45% of the open space on an empire-class dreadnought is the hangar bay
- 30% of the open space on an empire-class dreadnought is maintenance and industrial
- 20% of the open space on an empire-class dreadnought is living space (rooms and such)
- 4% of the open space on an empire-class dreadnought is cargo
- 1% of the open space on an empire-class dreadnought is miscellaneous hospitals, laboratories, offices, or the bridge, etc.
Moreover, most of this space is huge. You can fight a several thousand people into the 1/5 of the open-space that's meant for actual living. So Star Wars isn't too far off: most of your adventures in an Empire Class dreadnought (and probably in a capital ship as well) is in technical or industrial spaces, rather than corridors that connect to mess halls and gyms and holodecks and cabins.