One of my criteria is keeping current deck plans valid.
Ship tonnage
- Thread starter Tobias
- Start date
mike wightman
SOC-14 10K
mass could be the m-drive limiting factor
volume of the jump field could be the jump drive factor
To do this we would need to know the volume of the various items we already know the tonnage of
volume of the jump field could be the jump drive factor
To do this we would need to know the volume of the various items we already know the tonnage of
| Component | Mass | Volume |
| bridge | 20tons | 100 cubic metres |
| computer | varies by model, 1 ton of computer | 4 cubic metres |
| fuel | 1 ton | 14 cubic metres |
| cargo | 1 ton | 1 cubic metre |
| stateroom | 4 ton | 56 cubic metres |
| low berth | 0.5 ton | 0.25 cubic metres |
| emergency low berth | 1 ton | 0.75 cubic metres |
| acceleration couch | 0.5 ton | 0.25 cubic metres |
| jump drive | varies by drive, every 3 tons of drive | 1 cubic metre |
| power plant | varies by drive, every 4 tons of drive | 1 cubic metre |
| maneuver drive | varies by drive, every 2 tons of drive | 1 cubic metre |
| hardpoint fire control | 1 ton | 1 cubic metre |
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It is good to do what you want with this, a lot of us have done so as well to get a more plausible feel to spacecraft.
several points here...
As the OP says
see that one dton of fuel would mean two metric tons of mass, and so 28 kl of volume
You didn't set a volume for staterooms nor for bridge. I guess they would be more voluminous than heavy, as people need space. I even have serious doubts a stateroom masses 4 metric tons, despite being also what MT (taht discriminated volume and mass) also gives...
mike wightman
SOC-14 10K
I've finished filling in the table now. I used MT and TNE to get an idea of how dense stuff is.
If you know the actual volume in cubic metres then how you define your "deckplan cube" is a matter of taste
This is just a first attempt, something to do while bored.
If you know the actual volume in cubic metres then how you define your "deckplan cube" is a matter of taste
This is just a first attempt, something to do while bored.
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mike wightman
SOC-14 10K
Ok, second version with volumes rounded to the "nearest 5"
| Component | Mass | Volume |
| bridge | 20tons | 100 cubic metres |
| computer | varies by model, 1 ton of computer | 5 cubic metres |
| 1 ton capacity of fuel tank | 1.5 tons (full), 0.5 tons (empty) | 15 cubic metres |
| cargo | 1 ton | 1 cubic metre |
| stateroom | 4 ton | 55 cubic metres |
| low berth | 0.5 ton | 0.25 cubic metres |
| emergency low berth | 1 ton | 0.75 cubic metres |
| acceleration couch | 0.5 ton | 0.25 cubic metres |
| jump drive | varies by drive, every 3 tons of drive | 1 cubic metre |
| power plant | varies by drive, every 4 tons of drive | 1 cubic metre |
| maneuver drive | varies by drive, every 2 tons of drive | 1 cubic metre |
| hardpoint fire control | 1 ton | 1 cubic metre |
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If it includes corridors and common spaces, and includes the walls, doors, etc. that go with them, I can see that. Even with fairly lightweight panelling the weight of that sort of stuff adds up fairly quickly. Add in the mass of the stateroom's share of communal kitchen and food storage facilities and I can total see it. The lack of most of the walls <insert Starship Troopers shower/barracks scene clip here> would be partial justification for bunks massing less per displacement ton than staterooms.
Sorry if I was to quick to answer
Your table shows what I meant. With the system suggested in the OP, a 20 dton cargo shuttle and a 20 dton fuel shuttle would both mass 40 tons, but assuming both have 75% as paload (so 15 dtons), the second one would have about 390 kl more than the first one, as each ton of hydrogen would need 14 kl, while each cargo one would only need 1 kl. So, the same hangar would not fit both, despite both being 20 dton...
mike wightman
SOC-14 10K
I'm not using dtons, I am using metric tons and cubic metres.
Your very response shows that it is, e.g. you think of hangar space as the limited, defining resource, you are unable to process the idea that "fuel" may be anything other than pure hydrogen and you fail to comprehend that the very point of this is to not make current deck plans obsolete.
Hangar space would not be the limiting factor. Subcraft mass would be. Hangars would be as large as the designed-for craft require.
Hydrogen compounds would not be a method of carrying pure hydrogen. They would be the "fuel" (probably better thought of as a jump "reaction mass".)
Current deck plans would not become obsolete. They would just be downscaled to 1x1 meter squares. Since this is just a guideline they would also not fall afoul of this undeniable fact: Current deck plans for almost all canonical CT ships, going by the volume paradigm, are wrong. Ranging from the >20% undersized Scout/Courier to the ~80% oversized Merc Cruiser.
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G. Kashkanun Anderson
SOC-13
Your assumption about the original rules is not correct.
Out of the 21 times that the term 'mass' appears in LBB '77 Book 2 in reference to starships*, it is directly linked with the term 'displacement' (as in 'mass displacement') 16 of those times. Of the other five times, four of them show up solo on tables (where it can be assumed that 'displacement' is omitted for lack of room), and the fifth time is specifically in reference to ship's cargo (where it points out that this does not affect maneuver drive performance).
In other words, every single time that the word 'mass' appears as a statement related to starships or spacecraft in the 1977 text, it is specifically done so to describe a unit of displacement, not mass.
Also, the first two issues of JTAS (both of which predate HG '79) have deckplans, and they pretty clearly go along with the hydrogen displacement paradigm.
*There are three other appearances of the word in the book, but they are all associated with planetary mass.
Well, OK, but: if 'ton' already exists as a unit of weight and/or mass, then what do you think the 'd' is supposed to stand for?
mike wightman
SOC-14 10K
The trade section of LBB:2 describes a ship ton as 1000kg by mass.
"When determining the contents of a cargo, the players and referee must be
certain to correlate the established price of goods with the cost per ton. For example,
the base price of a shotgun is Cr150, while a ton of firearms as trade goods
has a base price of Cr30,OOO. A strict weight extension of the shotgun (3.75 kg per
shotgun) would indicate 266 shotguns. Extension should be instead based on
price, with weight as a limiting factor. Thus one ton of shotguns would contain 200
guns, at Cr150 each. The extra weight can be considered packing and crates. Similar
calculations should be made to keep prices in line on other trade goods."
"When determining the contents of a cargo, the players and referee must be
certain to correlate the established price of goods with the cost per ton. For example,
the base price of a shotgun is Cr150, while a ton of firearms as trade goods
has a base price of Cr30,OOO. A strict weight extension of the shotgun (3.75 kg per
shotgun) would indicate 266 shotguns. Extension should be instead based on
price, with weight as a limiting factor. Thus one ton of shotguns would contain 200
guns, at Cr150 each. The extra weight can be considered packing and crates. Similar
calculations should be made to keep prices in line on other trade goods."
Displacement of what?
Displacement of oceangoing ships is a measurement of weight (which is proportional but not identical to mass). And for LBB77, the matter is quite clear when you consider subcraft. An ATV explicity weighs 10 tons and takes 10 tons of ship, for example.
Crunch them: They do not. Neither do Judges Guild's 1979-published deckplans.
Dry, double, design, designation. Take your pick. Not like we don't have various types of 'tons' in historical seagoing ships.
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The snag here is that small craft's volumes determine how large (and thus how massive) the hangars need to be. Now, that can be handwaved with averaged out volumes per tonnes of craft, but that's just transferring the handwaving from mass to volume. I don't think one is better than the other, just different.
Actually, displacement does measure mass (indirectly - what it's really measuring is volume) - how much fluid a vessel displaces does not change with variations in gravity.
Sure, but as hangars are fixed in their volumes (unless a major refit is done), volume is more important than mass for them...
In traveller fuel is hydrogen because power comes from fusion plants, and if water or amonia may be used for fusion, I've never heard it (but I'm not a physics expert, so I might be wrong).
I've never read about jump reaction mass in Traveller, and all exlanations of jump I've read talk about lots of power (again, by fusion), so, unless I missed some source, you're talking about a quite strong change of paradigm...
Well, I'm afraid they would, as the volume (that is what maps show) of many components would vary (e.g., if we use water as fuel at equivalent tonnage, fuel tanks would now become 14 times what is needed)
I cannot discuss this point... While ITTR rules say you can be happy if your maps are within a 10% error margin, they don't seem to have applied to themselves...
I cannot talk about LBB2 '77, as I don' even think it reached Barcelona, and so I have never seen it, but latter versions all used this definition (the exact quote taken from TTB).
And so?
It's true the buoyancy force will be equivalent to the weight of the volume of fluid displaced, and so be affected by gravity, but so will the mass of the immersed body, so cancelling each other, and making buoyancy mass (weight) dependent, gravity being irrelevant, as Rupert says.
Yes, I understand, and that's why I said
See I discriminated both and taled about 1 dt (as TObias defined in the OP) would mean 2 tons (metric) before talking about the volume changes it would mean...
Agreed.
To give an example, with the OP suggestion, the veteran modular cutter (50 dtons in Traveller rules) would have quite a different tonnage depending on its use, and so, if wanting to keep it as a multi function craft and always fill in the ship's hangar, would have to be defined as "variable displacement" (as I guess most ships would, as their mass would depend on its use, at least if the mass used for displacement is the loaded one)
a.) Just to reiterate, they would not, because I'd redefine fuel as compounds (and tonnage to include fuel storage) not keep hydrogen as fuel with water as a carrier.
b.) Fuel volume is completely wrong in all official CT deckplans anyway. Example from Supp7: Scout is supposed to be 40% fuel, is actually 13-18%, depending on whether you take its (likely wrong) official dimensions or measure out the deckplans yourself.
I'll just put it differenty once more before I write this off:
a.) Mass-based tonnage
In theory, CT strictly defines a volume-based tonnage for ships and their components and then designs deckplans according to that tonnage.
In practice, CT defines a something-based tonnage and then arbitrarily designs deckplans connected to that tonnage only by extremely loose guidelines.
This idea simply brings the practice in line with the theory more, and the obvious angle for that is a mass-based tonnage (which also makes more sense wrt ship performance).
b.) Making ships smaller
This is a matter of preference, but I think I've spelled out my (IMTU) reasons for doing that fairly well. If you like larger, more comfy ships better, more power to you, but simply to make that clear: This is a separate point from a.)
P.S.: For fun, take the "typical humans" depicted in Supp7 and compare their size to the grid square.
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