tons

[BwapTED]

Looking through Book 2 , 1977, I was reminded of something.
Tons in Book 2 are a measurement of mass.
Volume isn't mentioned.
Again: the ton used in Book 2 is a explicitly a measure of mass displacement.

It's like a real-world displacement ton.

The volume of seawater displaced by a ship can be used to calculate the weight of the naval vessel because we know how much a set volume of seawater weighs.
We also know the mass of the seawater.



It appears that this was changed later, in other books.

I'm told Striker has something to do with it.

I'll have to dig up Book 5, but it has tons as volume, no?

 

[BwapTED]

A guy in another forum tells me he thinks that tons as mass make more sense with the Azhanti High Lightning graphics and fluff.


I wonder about the implications of computer tonnage, using this rule.

 

[AnotherDilbert]

The Hull: Hulls are identified by their mass displacement, expressed in tons.

Displacement is specifically used to connect a volume to a mass.

One displacement ton is the volume that displaces one ton of a specified fluid.

Traditionally displacement is used because it is easier to calculate the volume of the submerged part of the ship, than it is to measure the total mass of the ship.

No such fluid is specified until LBB5'79:

3. Volume: When referring to starship tonnage, one ton equals 14 cubic meters; the volume of one ton of liquid hydrogen.

 

[BwapTED]

Yup.

So it's definitely a mass measurement, just like the real long ton/displacement ton.
It may just be plain old long tons/displacement tons, at 2240 lbs (in 1 g).


If the vessels carry massive amounts of liquid hydrogen as fuel (or for other uses) it makes sense to speak of the volume of fuel tanks in 'd tons.'
But the rest of the vessel isn't made of liquid hydrogen...

It seems like the shift from measuring mass to measuring volume was a deliberate choice. I suppose it made mapping the star-ships easier and thus supported ship boarding actions and similar scenes.

I don't own Striker. Does it have a grid-based combat system with a fixed area for squares? 1.5 meters?

 

[BwapTED]

Going the the original rules, then, we can compare Traveler vessels with real world vessels.

Of course the total mass of a vessel and its contents will be greater if it is loaded with cargo and has full fuel tanks.

Let's assume that the displacement tonnage in Book 2 refers to fully-outfitted, fueled ship, carrying a crew and as much mass in cargo as it can to safely make a jump.
(Remember, if using the original rules as written, jump's not volume related , but mass-related).




The old Space Shuttle weighed about 107 tons at maximum takeoff weight.

The newer Soyuz rockets weigh over 300 tons.
The Soyuz spacecraft is wee by comparison, of course, and only adds a few more tons of weight/mass.


Somebody else can carry on with this, but I think comparing to actual spacecraft makes a certain amount of sense.

One could also compare to other vehicles.

 

[kilemall]

Yup.

So it's definitely a mass measurement, like the real long ton/displacement ton.

Well. Sorta.


LBB2 sounded more like metric tons. LBB5 has weight and displacement, which allows for a standard for deck plans with X assumptions on floor to ceiling height and support tech behind the walls.


Given the large amount of space given over to fuel, especially with higher power use or jump, it's a logical measurement tool.



But most everything the ship uses or carries is going to be more dense and thus heavier per dTon then hydrogen.


You could say a 100-ton ship that has 30 tons of fuel thus weighs 30 tons plus the rest of the ship, but the rest of that ship is going to be power plants, cargo, bridges, electronics, etc.



Not to mention that the ship hull itself is at least some higher tech material denser then steel (I think most Travellers would be highly uncomfortable in a ship with current Terran light/thin skins).


Here is a ridiculously complete chart of weight per cubic meter in kgs. You should be able to extrapolate most anything from these two sites.



http://www.anval.net/downloads/bulk density chart.pdf
https://www.simetric.co.uk/si_materials.htm


Multiply x 14 and you have your weight of X cargo.


Remember, water is related to all this- 1000kg of water is 1 metric ton occupying 1 cubic meter. So a Traveller dTon of water would be 14 metric tons.


As you can see, several grains and light powders weigh less then water, platinum weighs 21x water, so actual weight would be variable by cargo or composition of ship components.



So the real question is how much load bearing are you assuming about your ship and it's capacity to hold and lift X weight into space?


Most people don't bother. Personally, I assume a limit to how much can be carried per dTon and it's empty space otherwise, and if total weight is less then your 'drama limit' it's not a factor.


Finally, if you aren't aware of this article it goes into the whole thing, especially visualizing by wet water ships.


https://www.freelancetraveller.com/features/shipyard/tonnage.html

 

[BwapTED]

Yup to all of that and thanks for the article link!

I did more looking.

The Saturn rocket we used to get to the Moon seems to have weighed in at about 3K long tons.

 

[BwapTED]

IF it is mass, I think we just 'fixed' the computer size issue people have.

As many people have pointed out, the computer needs backups, cooling, tub-loads of shielding, etc. It's going to be big and heavy, anyway, at lower TLs.

Some guys still think computers take up too much space.


But with tons as mass and not as volume, the volume of the ship's computer can be much smaller than in post-1979 Traveller.

Note: Page 13, Book 2 1977
No listing for volume. Computers are given a mass.

I'm surprised I didn't fully realize all this earlier, but my mind was warped by seeing and playing later materials and editions before seeing the originals.

This also gets rid of planet cracking suicide runs with scoutships, I think.

More:

The New Space Launch system is supposed to weight something like five and a half million pounds. I'm not sure if that counts fuel.

But it comes out to roughly 2445 long tons.

 

[kilemall]

IF it is mass, I think we just 'fixed' the computer size issue people have.

As many people have pointed out, the computer needs backups, cooling, tub-loads of shielding, etc. It's going to be big and heavy, anyway, at lower TLs.

Some guys still think computers take up too much space.


But with tons as mass and not as volume, the volume of the ship's computer can be much smaller than in post-1979 Traveller.

Note: Page 13, Book 2 1977
No listing for volume. Computers are given a mass.

I'm surprised I didn't fully realize all this earlier, but my mind was warped by seeing and playing later materials and editions before seeing the originals.

Well, given the size of computers back then, even actual ship computers like the UYK-1, they were that displacement. Very few microcomputers in 1977, and most of those were on military craft.


The Saturn V computer was a ruggedized IBM 360 and quite large.


https://en.wikipedia.org/wiki/Saturn_V_Instrument_Unit

The UYK-7, a standard USN's shipboard computer of the era, was at least a dTon.


https://www.ithistory.org/db/hardware/sperry-rand/anuyk-7


The mainframe I first operated would probably work out to 3 dTons including storage.


I'm good with retroing in post-era explanations, mine tends more to a distributed networked computer spread through the ship that degrades slowly and is hard to kill, but I think the stats were literal intention at the time.

 

[BwapTED]

Right.

I'm trying hard to put later editions and materials out of my mind and look at the 1977 LBBs with fresh eyes.

Another thing...

Fuel.

If it is accounted by mass and not by volume, maybe it's not liquid hydrogen?

The strongest indicator for hydrogen in the early rules seems to be that bit about skimming gas giants.
Page 4

If not hydrogen, what else might it be?

EDIT Helium3?

 

[mike wightman]

Looking through 77 CT.

In the trade rules you will find that 1 ship ton is explicitly 1000kg.

Throughout the book fuel is mentioned, nowhere does it say what the fuel is...

And a couple of final things, the maneuver drive can be used for 288 'burns' - that's 28 hours of continuous thrust on a normal fuel load - and fuel hits in combat can eventually prevent you maneuvering, but you can still fire weapons, use the computer etc - batteries or is the power plant still in operation for electricity production?

Then there is no mention of artificial gravity or inertial compensation...

 

[AnotherDilbert]

So it's definitely a mass measurement, just like the real long ton/displacement ton.

Tonnage is consistently given as mass displacement, not mass.

Ton mass displacement is the volume displacing 1 ton of fluid, e.g. water.

Mass displacement is equal to total mass only for ships floating on fluid.

It may just be plain old long tons/displacement tons, at 2240 lbs (in 1 g).

Traveller is metric: 1 ton = 1000 kg. That is the real world unit used by most of the world.

I don't own Striker. Does it have a grid-based combat system with a fixed area for squares? 1.5 meters?

This has nothing to do with Striker: It was published later than the definition of 1 Dton = 14 m³ and it does not use a grid.

 

[AnotherDilbert]

Note: Page 13, Book 2 1977
No listing for volume. Computers are given a mass.

Yes, mass displacement:

Computer prices are given in millions of credits, and displacement required in tons.

 

[mike wightman]

Tonnage is consistently given as mass displacement, not mass.

Thing is it never defines what it means by mass displacement, for which you need to know the fluid you are immersing it in. Liquid hydrogen is the obvious choice if you look at the corpus of Traveller works, but in 77 CT we do not even know what fuel is, just that you can get it from gas giants.

But if all you have is 77 LBB:2 then tonnage is actual metric mass - we don't know anything about volumes or densities, this is made clear in the trade chapter.

 

[Ulsyus]

Is all of this linked not just through Stirker but more so through Snapshot? That was the original game focused on ship-boarding actions wasn't it? Hence the need to clarify the mass-to-volume issue for the purpose of having deckplans to use for the game.

 

[mike wightman]

Once the decision that liquid hydrogen fuel then for a typical jump equipped craft its fuel tanks are going to be 14 cubic metres per ton. This is roughly 500 cubic feet which maps rather nicely to deck=plan squares, call each half inch 1.5 m and give ceiling height of 3m and you get the magic two squares on the deck plan are equal to one displacement ton.

At a stroke this gives you a lot of area to map your ship components to but it comes at the price of not knowing what the mass of the ship is.

 

[kilemall]

Once the decision that liquid hydrogen fuel then for a typical jump equipped craft its fuel tanks are going to be 14 cubic metres per ton. This is roughly 500 cubic feet which maps rather nicely to deck=plan squares, call each half inch 1.5 m and give ceiling height of 3m and you get the magic two squares on the deck plan are equal to one displacement ton.

At a stroke this gives you a lot of area to map your ship components to but it comes at the price of not knowing what the mass of the ship is.

Which gets us back to my question, how much load bearing can any given part of a ship take in terms of density per dTon, and if you do come up with a figure what is the real lift capacity of our Mdrives, particularly in 1G+?
Answer the first question, you can spitball an 'empty'/'loaded' weight, then figure what the M-drive could/should do.


I like having an upper figure so players that load up that big Iridium strike with ore spilling into the hallways may have to throw something else overboard to take off.


Arguments could include a temporary liftoff doubling of M-drives (my take) or that an all-gravitic M-drive neutralizes gravity then provides a push/thrust.
But either way, that's not a casual weight we are pushing.


For starters, we could assume that a normal density of a loaded ship is the weight of water and our volume dton stands, the relative lightness of hydrogen fuel is counterbalanced by the weight of the hull itself plus the heavy machinery that constitutes engineering, weapons, etc.

So 100-dton is 1400 metric tons, 200 dton is 2800 metric tons, etc.

One could also argue that there is enough empty space in terms of hallways, staterooms, workspaces and other access material and a lot of cargo is less dense then water such that the value is 10 metric tons per dTon.
That would certainly be simpler- 100 dton 1000 metric tons, 200 dton 2000 metric tons, etc.
Then you can start getting a feel for doing things like how heavy a Seeker could be with ore on board that has a density 10x greater then water, actually having water in your fuel tanks as some suggest, etc.

Start to answer these, particularly with what granularity and game effect you want, and you can settle on what YTU standards are.

 

[BwapTED]

Looking through 77 CT.

In the trade rules you will find that 1 ship ton is explicitly 1000kg.

Throughout the book fuel is mentioned, nowhere does it say what the fuel is...

And a couple of final things, the maneuver drive can be used for 288 'burns' - that's 28 hours of continuous thrust on a normal fuel load - and fuel hits in combat can eventually prevent you maneuvering, but you can still fire weapons, use the computer etc - batteries or is the power plant still in operation for electricity production?

Then there is no mention of artificial gravity or inertial compensation...

Aha-you are right.

That shotgun example.
So many kilograms per ton.

It mentions weight.

 

[BwapTED]

Yes, mass displacement:

In the real world a displacement ton is a measurement of mass/weight(yes, I know the difference, but we are using it for ships on Earth). Displacement of seawater the the way it is calculated.

https://en.wikipedia.org/wiki/Displacement_(ship)


https://en.wikipedia.org/wiki/Long_ton

Traveller seems to have shifted the rules from displacement tons (mass measured by displacement) to something like gross tonnage (total volume).

 

[BwapTED]

RE volume


I notice that everything needs to fit inside the hull, including cargo. That's strange but it may have to do with the way jump works. I think that actually was addressed in some later source. JTA s24 Mega Traveller? Otherwise I'd think that you would use drop away or collapsible fuel pods and modular cargo containers that could attach to the outside of the ship.

This thread topic ended up divided between two threads because I posed a hypothetical on the 'crashing ships as weapons' thread.

If the mods like, I can delete or move some posts.