Star Wars Ship Mass and Density

[2046]

While working on an old unfinished page I'd forgotten about, I realized that I really needed a decent estimate of Star Destroyer mass. Despite not having much to really go on, I decided to make a guesstimate.

And hey, unless and until we get more information, it's as good as anything else:

So, let us assume that a Star Destroyer is 1600 meters in length. Now we need an estimate of their density. We have options here.

1. We can attempt to use the density of Star Trek vessels. Star Trek vessels like the Intrepid Class, for instance, have a density of over 1100 kg/m³. However, we know that the vessels are constructed of different materials and so on, so this is a somewhat dangerous assumption. There's also the fact that the Constitution Class ships had a far higher density of over 4300 kg/m³. However, given that the Intrepid can land as most Star Destroyer classes seem able to, the Intrepid density seems the safer (albeit still dangerous) assumption.

2. We can attempt to use the density of real-world spacecraft. This is also dangerous, of course, since real-world spacecraft are hardly military vessels. They are designed to allow people to get to space for a brief period of time, but can hardly be expected to withstand even a single hostile bullet or other decent-velocity impact.

Now, it happens that when Star Trek guru Rick Sternbach was designing the Intrepid Class for Star Trek: Voyager, he intentionally based their stated mass off of an estimate of the ship's volume, calculating the mass via a density derived from an estimate of the Apollo capsule command module. And indeed, the Intrepid density is within about 10-20% of that value, assuming the Intrepid model used on this site for the estimate is basically the same as his. However, the command module was basically just the crew compartment and heat shield for re-entry, a single part of the combined Command/Service Module (CSM), with the service module featuring the large engine bell and other machinery that enabled Earth-Moon transit.

Taking that combined vehicle which masses 30 tonnes and ballparking her volume based on her 4m diameter and 8m length (she's actually 11 meters, but between the rear engine bell and conical front section a 'shave' is not out of order for determining ballpark density), the CSM volume is 100m³ and her density is thus 298kg/m³.

That seems a bit light, so we can also compare to the space shuttle orbiter. Empty, a newer shuttle like Endeavour weighs about 70 tonnes, and she's about 105 tonnes when full. At about 37.25m long, 23.75m wide, and 17.25 meters tall, she's a big girl. Determining her density is a little bit of a trick, though, since much of her total empty mass . . . not to mention her width and height . . . is nothing more than wing surfaces. But since we're ballparking, we can simply take the fuselage as a cylinder and tack on a couple of extra meters for the eyeballed volume of the various atmospheric control surfaces.

So, per estimation from this site, we have the total length of 37.25 meters. A smidgen of that is the vertical stablizer (the tail fin), but we'll just roll with that figure. Given that the shuttle fuselage is roughly cylindrical, the height and width values of about 6 meters are sufficient for diameter (the crew area and payload bay are below six meters, the rear fuselage with the engines is over six). So if we ballpark a 40x6 cylinder, we come up with a total volume of 1130m³. Given her empty and full masses, the density ranges between 62 and 93kg/m³.

Well, now. It seems that Rick Sternbach's choice was rather on the heavy side, after all. The space shuttle tops out at around 100kg/m³, the Apollo CSM 300kg/m³, and the Apollo command module with heat shield by itself is near 1000kg/m³. And yet the Constitution Class still came in four times more dense than that, and about 40 times denser than the space shuttle!

So where should we attempt to put the Star Destroyers? Considering that large warships of the Clone Wars era seem to be largely hollow (e.g. the Venators with their extensive landing bay areas, the Malevolence with its massive open center railway areas, and so on), I hardly feel comfortable comparing it to an Intrepid Class ship that has very little empty space by comparison.

On the other hand, given the extensive use of simple steel even for external towers on the Death Star (per the ANH novelization), Coruscant buildings, and similar, it seems unlikely that durasteel or steelcrete will be superdense. After all, given that a natural stone on Yavin was so dense that no weapon was thought capable of penetrating it, we could be forgiven in believing that Star Wars ships are built strong but as light as possible.

That said, I figure Star Destroyer density probably falls somewhere in the 500-1000kg/m³ range.

Given a calculated volume of about 54,000,000m³ for Star Destroyers at 1600m length, and a density range of 500-1000kg/m³, the mass of a Star Destroyer should fall somewhere between 27,000,000,000 and 54,000,000,000 kilograms. That's 27 to 54 million metric tonnes.

If one wants a specific estimate, I'd guess a density of 750kg/m³ and an ISD mass of 40,000,000 tonnes.

Using this density figure elsewhere would give us the following masses:

Code: Select all

 
Vessel                    Mass in Kilograms     Mass in Tonnes (est.)
 DS1 (@120km):   678525000000000000                680 trillion 
 DS2 (@160km): 1608000000000000000            1.6 quadrillion 
 Super SD:                  9484425000000                  9.5 billion
 Home One:                  253978500000                 250 million
 Trade Fed:                 1520812500000                  1.5 billion
 Nebulon-B:                       138729000                    140,000
 Tantive IV:                        48564000                      50,000
 X-Wing:                                 20250                            20
 TIE:                                      11250                            11
 Imp. Shuttle:                        357750                           360
 Millennium Falcon:                2937750                         3000 

Actual figures could vary significantly, of course, and my rounding above was somewhat haphazard. I would say that this is especially the case with smaller vessels, but interestingly the X-Wing mass is almost identical to the empty mass of an F-14 Tomcat, which is only a meter shorter. Once missiles and fuel are added, though, an F-14 can mass 33 tonnes.Also, I don't have volume figures for the Venator or Acclamator. I'd guesstimate the former at 15 million tonnes and the latter around 8-10, but I really have no clue as to the proper value. This is just a complete pulled-from-the-posterior guess from memory.

[Mr. Oragahn]

I'd love seeing the volumetric figures, notably for the ISD. They'd actually help me a great deal for that little "paper" I'm assembling. All I found thus far was
here, where "RelentlessRouge" estimated the volume of an ISD at "203.01 million cubic meters".
Almost four times your figure.

[Mike DiCenso]

Oddly enough, there is very little in the way of mass figures for Star Wars ships. For the Millenium Falcon, the only figure given in the EU is the old Star Wars roleplaying game Sourcebooks, which cite a cargo capacity of 100 metric tons.

Weight seems to be a critical factor with SW ships as well based on the descriptions of the Invisible Hand's construction in the RoTS novelization. The only capital ship mass descriptions in the RoTS ICS and other sources list the Venators as having a 20,000 metric ton cargo capacity, and of course the now infamous 40,000 metric tons a second hypermatter fuel maximum consumption figure (this last figure is a bit suspect as we know from the EU Death Star novel that capital ships did not carry hypermatter reactors until the advent of the Type II ISDs).
-Mike

[2046]

That's because he's smoking crack. A 1600m x 800m x 225m box gives you 288,000,000 cubic meters, which is over but close to his figure. That would be a brick as tall as the main wedge (i.e. without the superstructure or bridge). If I were to eyeball the shape of an ISD and try to mash it down into a rectangle, I might choose 1600x500x150 or so, which would give me 120,000,000 cubic meters.

If I apply the pyramid volume formula, and go with the figures of 225x800 for the base and 1600m for the height, I end up with a volume of 96,000,000 cubic meters.

Hmm. Seems like my figure's running low somehow. So I may also be smoking crack. But his is worse. :-)

[Jedi Master Spock]

That's because he's smoking crack. A 1600m x 800m x 225m box gives you 288,000,000 cubic meters, which is over but close to his figure. That would be a brick as tall as the main wedge (i.e. without the superstructure or bridge). If I were to eyeball the shape of an ISD and try to mash it down into a rectangle, I might choose 1600x500x150 or so, which would give me 120,000,000 cubic meters.

If I apply the pyramid volume formula, and go with the figures of 225x800 for the base and 1600m for the height, I end up with a volume of 96,000,000 cubic meters.

Hmm. Seems like my figure's running low somehow. So I may also be smoking crack. But his is worse. :-)

That would be because you just calc'd for a pyramid with a square base. Instead, we have a diamond base with width and height measured from its points rather than across its edges, which is half the area, and hence half the volume.

A 1600m long pyramid with a diamond base inscribed inside a 900x280m rectangle would easily contain everything except the bridge tower, and have some room to spare at 67 million cubic meters. Given the fact that the ISD is not a perfect triangle from above, but actually a diamond of sorts (chopping off the largest corners) and much of the aft end within that diamond is further cut into by the empty space around the ion engines, your original estimate is probably dead on the money.

Luke's X-Wing slowly sinks into the swamp on Dagobah - very slowly - so it's probably pretty close to 1 gram/cc. Similarly, anything that acts like a submarine should be not too far from 1 gram/cc, like the Gungan Bongo - it probably takes on ballast in order to get there, but it shouldn't be too far off to start with. If we could, by any chance, see a ship making a water landing without sinking to the bottom, that would give us a very good idea as to its density.

FWIW, averaging the guesses made in the fanfic debate thread gave 24 million tons for the Venator.

[Mike DiCenso]

Just checked RelentlessRouge's numbers, and did an over-estimate by assuming a maximum dimension of 1,600 (L) x 853 (W) x 503 (H), and using a solid rectangular block for the ISD, which would be a stupendeously ridiculous 686,784,128 cubic meters. That's the about the absolute maximum volume or more than 3.3 times his number. I have no idea where he sources his scaling of an ISD from. Could be anywhere to be honest. Using the pyramid formula of (1/3) * (base area) * height for the ISD main hull I get 122,832,000 m^3. Again this assumes it is a solid pyramid, and can be brough lower by subtracting the two hanger bay spaces and the side trenches as well as the trench notches and the space around the large engine nozzles, which is probably why your CGI model low-balls the number.
-Mike

[Mike DiCenso]

Using JMS' having for the diamond shaped base, I get a new number of 61,426,500 meters cubed. So the hull number isn't too far off. Knocking downwards for the variables, I can easily see an ISD main hull with around 50 million meters cubed.
-Mike

[Mr. Oragahn]

Weight seems to be a critical factor with SW ships as well based on the descriptions of the Invisible Hand's construction in the RoTS novelization. The only capital ship mass descriptions in the RoTS ICS and other sources list the Venators as having a 20,000 metric ton cargo capacity, and of course the now infamous 40,000 metric tons a second hypermatter fuel maximum consumption figure (this last figure is a bit suspect as we know from the EU Death Star novel that capital ships did not carry hypermatter reactors until the advent of the Type II ISDs).
-Mike

The ICS figure is only there to legitimate the teratons per second, no more, no less. This figure is more than suspect in light of the material picked from WEG's supplement Black Ice.

That's because he's smoking crack. A 1600m x 800m x 225m box gives you 288,000,000 cubic meters, which is over but close to his figure. That would be a brick as tall as the main wedge (i.e. without the superstructure or bridge). If I were to eyeball the shape of an ISD and try to mash it down into a rectangle, I might choose 1600x500x150 or so, which would give me 120,000,000 cubic meters.

If I apply the pyramid volume formula, and go with the figures of 225x800 for the base and 1600m for the height, I end up with a volume of 96,000,000 cubic meters.

Hmm. Seems like my figure's running low somehow. So I may also be smoking crack. But his is worse. :-)

That would be because you just calc'd for a pyramid with a square base. Instead, we have a diamond base with width and height measured from its points rather than across its edges, which is half the area, and hence half the volume.

A 1600m long pyramid with a diamond base inscribed inside a 900x280m rectangle would easily contain everything except the bridge tower, and have some room to spare at 67 million cubic meters. Given the fact that the ISD is not a perfect triangle from above, but actually a diamond of sorts (chopping off the largest corners) and much of the aft end within that diamond is further cut into by the empty space around the ion engines, your original estimate is probably dead on the money.

Yes, the bridge tower's volume can easily be compensated by the receded engines area and the main ventral bay, unless you booleaned their volumes out of the diamond-based pyramid volume.
So I'll probably go with Robert's figure. I'm also terribly lazy here, to be honest. :)

[2046]

That would be because you just calc'd for a pyramid with a square base. Instead, we have a diamond base with width and height measured from its points rather than across its edges, which is half the area, and hence half the volume.

I will not post when in a hurry to leave.
I will not post when in a hurry to leave.
I will not post when in a hurry to leave.
I will not post when in a hurry to leave.
I will not . . .

[2046]

Luke's X-Wing slowly sinks into the swamp on Dagobah - very slowly - so it's probably pretty close to 1 gram/cc.

The X-Wing sinks all of the sudden, actually . . . it sat on the ground beneath the not-terribly-deep water from the time of landing until the middle of the stone-stacking exercise. Then R2 freaks because all of the sudden the thing is almost submerged.

Presumably the ground beneath both it and the water gave way somehow, since not only did it sink all of the sudden but also turn by about 30 degrees, as well, given the apparent orientation of the guns versus the ship's prior orientation (with the big tree nearby as a guide). Perhaps the thing that tried to eat R2 had an underwater lair that collapsed? Who knows.

But in any case, I'd say that's more a test of the ground pressure of the lake bottom.

[2046]

Also, regarding the Venator, if we play "Honey I Shrunk the Warship" and simply drop an ISD down to 1100 meters from 1600 (i.e. ignoring the structure differences between the Venator and Imperial), then the Venator would come out to 17.2 million cubic meters, with a mass therefrom of 13 million tonnes . . . pretty close to my posterior-derived value.

But, I think the Venator is probably overestimated using that method. The Acclamator is somewhat better for such, in my opinion. So, by the same method, an Acclamator (which is shorter than I misremembered, at 752 meters) would come out to 5.5 million cubic meters and 4 million tonnes. (I'm iffy on the mass, given that the bloody thing is mostly hollow, but the volume is probably not too embarrassingly far off.)

But again, the numbers in this post are only slightly better than posterior figures.

[2046]

I'm getting north of 80 million for the ISD on a SketchUp model that appears to be good for the purpose.

I'm gonna have to get hardcore on these and doublecheck what's what.

[Mr. Oragahn]

In the Clone Wars cartoon, there was an episode with Acclamators floating on a sea.

I wonder if there's been a TCWS episode with something similar occurring.

[2046]

Not at all, I'm afraid.

[2046]

Okay folks . . . dunno what was up with the old LightWave stuff or the model previously used, but the ISD was wrong.

It looks like I am going to be replacing the value of ~54 million with a new value of ~75.5 million in a coming update, a 40% boost. Too much more accuracy won't be possible, given the ISD's excessive detailing, general lack of published reference photos of good quality, and model proportion variations.

(The correct proportions for an ISD of the main type seen (e.g. the Avenger model) if assuming 1609 meters length is a width of 821 meters and a rearmost primary dagger hull height of 202 meters, give or take a couple of meters. I haven't worried about the entire height of the ship so I don't have that value handy.)

Ideally I would have a better ISD model (they're often made super-sloppy), but this was the one I could get to function with the least amount of headache (which was still a lot). It is not perfectly representative of the TESB ship, and I've tried to account for that by eyeball in my scaling. A future update may revise the value slightly.

I've also corrected the Venator and Acclamator values upward (turns out they were also off, but due to the SketchUp plugin being way more finicky on model quality than I initially thought).