How do you calculate mass / tonnage from the ship's volume?
- Thread starter Sgt_G
- Start date
I think Masao
www.starfleet-museum.org
—had a write up in the GEC Quarterly that had some helpful information on that—-I can’t find it…rats
The Starfleet Museum - A Report by Masao Okazaki
www.starfleet-museum.org
I think you might want to read up on Displacement (ship).
To put it 'unsimply' - you have to know what the average density of that object would be... That would require knowing what materials are used and their properties and exactly how much of those materials are used etc......
So.....yeah.
So.....yeah.
Well hello there . . . welcome to my wheelhouse.
In the case of Star Trek starships, we have two canonical datapoints (at least pre-2009/2017). The first was Scotty's reference in "Mudd's Women" to the Enterprise being nearly a million gross tons. The second is Voyager's mass, stated twice, of 700,000 metric tonnes.
Thanks to the talented folks who have made 3-D starship models for free, plus the geniuses who've made volume estimation plugins and tools for 3-D modeling programs, it becomes possible to get volumes for both Enterprise 1701 and Voyager 74656, at which point you have vessel densities, densities applicable to other vessels.
The plugin I use basically just makes a ton of slices through the model, making numerous surfaces that have an area and an equal height between each. The beautiful part is that it shows you the results so you can confirm that all of those surfaces actually got made . . . models with holes, gaps, and certain other problems can thus be confirmed not to be underreported, and of course you can twist and turn the model to re-run it for verification. In the below, you're seeing a New Orleans with a ton of slices (and the tops and bottoms of the surfaces colored differently) in an area where it looked pretty good. There's also an upright Galaxy image and you can see where the nacelle pylon connections to the nacelles had some gaps, leading to failed slices and low reading.
Is my technique valid? Well, it seems to work pretty well. My Intrepid-based Galaxy mass is 6.5 million tonnes, but after my work came out I think five million might be visible on a TNG-R display . . . but then volume coefficient and volume by surface area and just plain size all also matter, along with other technical details. My estimates don't currently take all of that into account since it would be another layer (or layers) of wild-ass guessing . . . but one I'm considering given the TNG-R thing.
In any case, the wild-ass guessing works well enough that my Imperial Star Destroyer mass estimate from an older 2010 blog post is, as far as I know, still Star Wars canon.
So just going by Voyager and the Delta Flyer's apparent densities, I'd presume your ship ought to come in around 61,000 tonnes, give or take. There could be differences off this estimate . . . for instance, is it a boxy thing like a Raven-type or some sort of marvelously svelte and graceful bird? Is it a cargo hauler, or an armored small frigate, or some sort of speed queen? These give plenty of room to move up or down . . . oh, and design age, too.
In the case of Star Trek starships, we have two canonical datapoints (at least pre-2009/2017). The first was Scotty's reference in "Mudd's Women" to the Enterprise being nearly a million gross tons. The second is Voyager's mass, stated twice, of 700,000 metric tonnes.
Thanks to the talented folks who have made 3-D starship models for free, plus the geniuses who've made volume estimation plugins and tools for 3-D modeling programs, it becomes possible to get volumes for both Enterprise 1701 and Voyager 74656, at which point you have vessel densities, densities applicable to other vessels.
The plugin I use basically just makes a ton of slices through the model, making numerous surfaces that have an area and an equal height between each. The beautiful part is that it shows you the results so you can confirm that all of those surfaces actually got made . . . models with holes, gaps, and certain other problems can thus be confirmed not to be underreported, and of course you can twist and turn the model to re-run it for verification. In the below, you're seeing a New Orleans with a ton of slices (and the tops and bottoms of the surfaces colored differently) in an area where it looked pretty good. There's also an upright Galaxy image and you can see where the nacelle pylon connections to the nacelles had some gaps, leading to failed slices and low reading.
Is my technique valid? Well, it seems to work pretty well. My Intrepid-based Galaxy mass is 6.5 million tonnes, but after my work came out I think five million might be visible on a TNG-R display . . . but then volume coefficient and volume by surface area and just plain size all also matter, along with other technical details. My estimates don't currently take all of that into account since it would be another layer (or layers) of wild-ass guessing . . . but one I'm considering given the TNG-R thing.
In any case, the wild-ass guessing works well enough that my Imperial Star Destroyer mass estimate from an older 2010 blog post is, as far as I know, still Star Wars canon.
So just going by Voyager and the Delta Flyer's apparent densities, I'd presume your ship ought to come in around 61,000 tonnes, give or take. There could be differences off this estimate . . . for instance, is it a boxy thing like a Raven-type or some sort of marvelously svelte and graceful bird? Is it a cargo hauler, or an armored small frigate, or some sort of speed queen? These give plenty of room to move up or down . . . oh, and design age, too.
This is the ship in question:
Note: Artwork is mine, but the design is based off SFB, so this is a Derivative Copyright by ADB.
When I asked the AI bots if a ratio of 1:1 tonnes per meter-cubed was right, they gave me about six different answers ranging from 0.1 tonne / m^3 base of the ISS to "0.9 - 1.2" t/m^3, with a lengthy explanation about ocean ships measured with the Panama Canal standard of one ton (not tonne) per 100 cubic feet (2.83 cubic meters), which works out to 0.32 tonne / m^3. It went downhill when I asked about how it's calculated in most game systems (e.g., Traveler). At that point, I gave up and came here to ask if there's a "Trek" answer.
Note: Artwork is mine, but the design is based off SFB, so this is a Derivative Copyright by ADB.
When I asked the AI bots if a ratio of 1:1 tonnes per meter-cubed was right, they gave me about six different answers ranging from 0.1 tonne / m^3 base of the ISS to "0.9 - 1.2" t/m^3, with a lengthy explanation about ocean ships measured with the Panama Canal standard of one ton (not tonne) per 100 cubic feet (2.83 cubic meters), which works out to 0.32 tonne / m^3. It went downhill when I asked about how it's calculated in most game systems (e.g., Traveler). At that point, I gave up and came here to ask if there's a "Trek" answer.
Well, you can see more of my old thinking here:
Something closer to the Constitution density would seem applicable, given the apparent vintage. That's 4000kg/m³ instead of an Intrepid's 1200, or about 200,000 tonnes.
That said, there's lots of room to wiggle numbers if that one is displeasing, there are lots of possibilities and counterindications. But, in your case, I would say:
1. Your vessel is boxier than a Connie so wouldn't have as much extra outer hull or as much structural support need for the volume obtained.
2. Your vessel is smaller than a Connie so should be able to be as strong a structure (i.e. if Apollo grabbed it and shook) with less spaceframe mass. (Bernd has a good write-up on this: https://www.ex-astris-scientia.org/articles/scaling.htm )
3. The Connie is about one quarter nacelle, which is a lot compared to most other Trek ships. Eyeballing it, your police cruiser is similar (albeit with a smaller deflector, so I would guess it is capable of good dash speeds over sustained velocity). So, I wouldn't tend to go too low, based on the notion that nacelles tend to be denser than the rest.
It's all fictional, but I would definitely stay above 100,000, and would tend toward the mid-to-high 100s, unless there's some consideration to the contrary.
After all, Starfleet is using tritanium bulkheads and solid duranium panels all through the ship corridors even in the 24th Century, per "Where Silence Has Lease" and "A Matter of Perspective", so it isn't like these jokers seem to be going too far out of their way to avoid weight.
Something closer to the Constitution density would seem applicable, given the apparent vintage. That's 4000kg/m³ instead of an Intrepid's 1200, or about 200,000 tonnes.
That said, there's lots of room to wiggle numbers if that one is displeasing, there are lots of possibilities and counterindications. But, in your case, I would say:
1. Your vessel is boxier than a Connie so wouldn't have as much extra outer hull or as much structural support need for the volume obtained.
2. Your vessel is smaller than a Connie so should be able to be as strong a structure (i.e. if Apollo grabbed it and shook) with less spaceframe mass. (Bernd has a good write-up on this: https://www.ex-astris-scientia.org/articles/scaling.htm )
3. The Connie is about one quarter nacelle, which is a lot compared to most other Trek ships. Eyeballing it, your police cruiser is similar (albeit with a smaller deflector, so I would guess it is capable of good dash speeds over sustained velocity). So, I wouldn't tend to go too low, based on the notion that nacelles tend to be denser than the rest.
It's all fictional, but I would definitely stay above 100,000, and would tend toward the mid-to-high 100s, unless there's some consideration to the contrary.
After all, Starfleet is using tritanium bulkheads and solid duranium panels all through the ship corridors even in the 24th Century, per "Where Silence Has Lease" and "A Matter of Perspective", so it isn't like these jokers seem to be going too far out of their way to avoid weight.
