Capital Ship Weaponry
- Thread starter phavoc
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Tonnage and displacement tons for nautical ships has absolutely no direct relationship with Traveller tons.
Repeat - Tonnage and displacement tons for nautical ships has absolutely no direct relationship with Traveller tons.
They are in fact completely different measures - and displacement tons for nautical ships refers to displacement of water - which is dependent on mass and shape! It describes the volume of water displaced - and its definition varies widely, though 2.83 cubic meters might be the closest conservative equivalence (though, because of shape and water density, it can take higher values).
Further, there are loaded and unloaded displacement tonnages for nautical ships (because of mass and varying shape as waterline changes).
MGT tons is a lot simpler - its just volume of space (related to hydrogen volume of a given mass).
To calculate the MGT tons equivalent for the Yamoto would require actual dimensions of the ship - and cannot be derived or even well estimated from traditional nautical displacement tonnage.
Note also, that most dimensions only provide the height in terms of the water line - not to the deckline. And, other than barges and some freighters, the shape is so far removed from a 'box' that calculus would need to be used to come close to the actual volume.
All-in-all, it is rather useless to compare MGT spaceships, in almost any way, to nautical ships!
Submarines - given their typical shapes can be easily estimated (and submerged displacement tons could be used if one knows what type of tons and assumed water density were used).
A better comparison would be to skyscrapers! (And, for most, it would be a better visual comparison to size and far easier to calculate).
Repeat - Tonnage and displacement tons for nautical ships has absolutely no direct relationship with Traveller tons.
They are in fact completely different measures - and displacement tons for nautical ships refers to displacement of water - which is dependent on mass and shape! It describes the volume of water displaced - and its definition varies widely, though 2.83 cubic meters might be the closest conservative equivalence (though, because of shape and water density, it can take higher values).
Further, there are loaded and unloaded displacement tonnages for nautical ships (because of mass and varying shape as waterline changes).
MGT tons is a lot simpler - its just volume of space (related to hydrogen volume of a given mass).
To calculate the MGT tons equivalent for the Yamoto would require actual dimensions of the ship - and cannot be derived or even well estimated from traditional nautical displacement tonnage.
Note also, that most dimensions only provide the height in terms of the water line - not to the deckline. And, other than barges and some freighters, the shape is so far removed from a 'box' that calculus would need to be used to come close to the actual volume.
All-in-all, it is rather useless to compare MGT spaceships, in almost any way, to nautical ships!
Submarines - given their typical shapes can be easily estimated (and submerged displacement tons could be used if one knows what type of tons and assumed water density were used).
A better comparison would be to skyscrapers! (And, for most, it would be a better visual comparison to size and far easier to calculate).
According to Wikipedia the Yamato had dimensions of approximatelycbrunish said:
263 meters x 37 meters x 11 meters.
If it were a rectangular box, it would have a volume of about 107,000
cubic meters.
Since a Traveller dton has approximately 14 cubic meters, this would
be a little more than 7,600 dtons, but due to its shape the Yamato was
probably much closer to about 2/3 of it, which would be 5,000 dtons (a
very rough estimate).
As rust says - that is a very rough estimate.
The 11m is draft - not overall, deck, nor average height.
The draft is measured from the waterline (unloaded/or certain load) to the bottom (keel) of the vessel. It varies from bow to stern (mean is probably given), with load, water density (esp. salt versus fresh), and even speed.
This leaves quite a bit unmeasured (everything above the waterline).
In addition, looking at the profile - the superstructure is pretty substantial (as are the guns!).
Again - most ships are hard to even come close to guessing (this one might be 4000-7500 tons - quite a range) there volume.
The 11m is draft - not overall, deck, nor average height.
The draft is measured from the waterline (unloaded/or certain load) to the bottom (keel) of the vessel. It varies from bow to stern (mean is probably given), with load, water density (esp. salt versus fresh), and even speed.
This leaves quite a bit unmeasured (everything above the waterline).
In addition, looking at the profile - the superstructure is pretty substantial (as are the guns!).
Again - most ships are hard to even come close to guessing (this one might be 4000-7500 tons - quite a range) there volume.
Here is an old graph that I put together awhile ago comparing modern warship hydrostatic displacement (in metric tons) to enclosed internal volume (that I took from a variety of technical papers). Over time I also aded data for submarines, mine counter measures vessels, a couple landing ships, and estimates that I had put together for three WWI era battleships. While I'm guessing that WWII era ships may be a little different from any of these curves I suspect that if you had enough data points you could probably put togther a rough curve to relate volume to displacement for them too.
From the graph, a modern ship has about 3.39 cubic meters of internal volume per ton of displacment (eg, a 5000 tons destroyer will have about 16,950 cubic meters internal volume). In Traveller terms if 14 cubic meters equals one dTon then a 5000 ton modern destroyer equates to about a 1210 dton starship (in terms of volume). Or in other words there are about 4.13 tons per dton for a modern warship.
Although a WWII ship may not follow the same curve, a modern 69,250 ton warship would equate to roughly 16,800 dtons. Using the WWI curve instead you would get about 10,380 dtons. Or in other words, based on the very limited sampl I have there might be about 6.67 tons per dton for the WWI era battleships that I have an estimate for. I wouldn't be surprised if the Yamato ended up somewhere in between (perhaps a little closer to the modern line than the WWI estimate).
Anyway, just some additional info.
Regards
PF
From the graph, a modern ship has about 3.39 cubic meters of internal volume per ton of displacment (eg, a 5000 tons destroyer will have about 16,950 cubic meters internal volume). In Traveller terms if 14 cubic meters equals one dTon then a 5000 ton modern destroyer equates to about a 1210 dton starship (in terms of volume). Or in other words there are about 4.13 tons per dton for a modern warship.
Although a WWII ship may not follow the same curve, a modern 69,250 ton warship would equate to roughly 16,800 dtons. Using the WWI curve instead you would get about 10,380 dtons. Or in other words, based on the very limited sampl I have there might be about 6.67 tons per dton for the WWI era battleships that I have an estimate for. I wouldn't be surprised if the Yamato ended up somewhere in between (perhaps a little closer to the modern line than the WWI estimate).
Anyway, just some additional info.
Regards
PF
