tons

[kilemall]

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.

I think everything posted is pertinent, given that the source material can be confusing or interpreted differently.


In CT/HG you can have drop away fuel tanks, whole rule set for that.


The distributed hull with the attachable ships is a perfect model for external container hauling. Since fighters BRs and other craft can be hauled off and jumped, cargo containers IMO can too.


IMTU I make a distinction between cargo bay and external containers, by forcing any external mounted ones be built to starship hull standards and therefore more expensive. The ability to rapidly detach and attach containers would be appealing to a megacorps shipping line with tight turnaround usage of expensive high-jump 'container tenders'.

 

[BwapTED]

I think everything posted is pertinent, given that the source material can be confusing or interpreted differently.


In CT/HG you can have drop away fuel tanks, whole rule set for that.


The distributed hull with the attachable ships is a perfect model for external container hauling. Since fighters BRs and other craft can be hauled off and jumped, cargo containers IMO can too.


IMTU I make a distinction between cargo bay and external containers, by forcing any external mounted ones be built to starship hull standards and therefore more expensive. The ability to rapidly detach and attach containers would be appealing to a megacorps shipping line with tight turnaround usage of expensive high-jump 'container tenders'.

Cool beans.

I've given some thought to wilderness refueling from gas giants as a possible in-game explanation of the 'displacement' mentioned in 'mass displacement.'

I mean, the star-ship has to be displacing some fluid mass for the measurement of mass by volume of that fluid (seawater for real oceangoing vessels) to make any sense, right? Does the mass displacement thing refer to skimming gas giants?

Or is it an unspoken assumption that maritime shipbuilders cinched the early contracts for building star-ships, instead of aerospace firms?

The military, maybe? We do see that the 'Navy' is the space force.

'Mass displacement' is a weird anachronism? Nothing is actually being displaced, unlike a maritime ship in water, but the Space Navy still uses d-tons because it's traditional?

 

[kilemall]

You can make it mean whatever you want to culturally IYTU.


I was just settling what the UK space navy will be IMTU, my reference person that I put the decision to says 'Royal Space Corps'. So there it is, always good to have the background settled. Do whatever for tons.


Re: hydrogen or whatnot, I never felt disoriented or affected by all this hoohaw over fuel.



Before Traveller we played Imperium and it was clear from the tanker rules that there was such a thing as local refueling, and at Sirius as a major chokepoint there was not. Hence the need for the exotic tanker that harvested hydrogen fuel from Sirius itself.



Could have been water or hydrogen but some of those colonial systems likely don't have freestanding water, so hydrogen.

 

[infojunky]

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.

Sure Quote me here.....

Read through '77 Book 2 and '79 Book 5. Read both the text and the charts, then cross reference to AHL...

 

[BwapTED]

Sure Quote me here.....

Read through '77 Book 2 and '79 Book 5. Read both the text and the charts, then cross reference to AHL...

HE IS AMONG US!

DUH DOOOOOM DOOOOOM

 

[coliver988]

Cool beans....

The military, maybe? We do see that the 'Navy' is the space force.

'Mass displacement' is a weird anachronism? Nothing is actually being displaced, unlike a maritime ship in water, but the Space Navy still uses d-tons because it's traditional?

Well, we ARE talking Vilani here...

 

[dalthor]

I usually prefer Volume to mass, and that is generally what we used in our gaming group.

[ Begin side note, just because...

This originally led to some interesting discussions about a jump bubble - spherical, or a "field" surrounding the hull?

Greatly affected Cluster, Braced, Planetoid, and Unstreamlined hulls -- we had some truly bizarre custom designs, and the Lab ship was a VERY hotly debated issue.

We initially decided spherical, diameter 6 meters larger than the longest dimension of the ship. This led to unexpected side effects - a needle ship tended to misjump or fail to jump due to the amount of <whatever> that was mistakenly [or not so mistakenly] left within that diameter.

Of course, jump plates and jump grid (Lanthanum-wired hull) were discussed, too. It was determined that anything not "included" in that grid didn't go - the hull itself was fine, but antennae and similar "extrusions" tended to be left behind. This led to a LOT of deployables and/or folding items...and made for some truly fun designs, and very sleek hulls.

We then about a 3-meter field around the ship for the bubble; that seemed to work out better, and in the long run was the "goto" in our games. It meant the bubble might be oddly shaped, i.e. that you could still park stuff close to the ship, and yet still worked with funky hull shapes we designed.

Plates and grid were limited to a one-meter gap around the physical hull; could have extrusions, but they were more limited, and tended to fold against -- or into -- the hull when the ship jumped.

These days, we don't care so much; if the story requires too much "in the bubble" to jump, we go with it, and don't worry as much about the particulars.

end ]

 

[BwapTED]

Well, we ARE talking Vilani here...

Excellent point for the OTU!

If I do use volume-tonnage and not mass-tonnage I can call always them v-tons for volumic.
Or f-tons for fuel-tons.

 

[kilemall]

Here is another fun one to settle with the whole tonnage issue.


Will our ships float or sink in water?


Correct if I am wrong, but we should be able to settle that with knowing our dTonnage vs. our massTonnage and world G and atmosphere density, right?

 

[BwapTED]

Here is another fun one to settle with the whole tonnage issue.


Will our ships float or sink in water?


Correct if I am wrong, but we should be able to settle that with knowing our dTonnage vs. our massTonnage and world G and atmosphere density, right?

Several guys have suggested the ships would indeed float because of the fuel (or near- vacuum, if emptied) in the tanks and the air in the pressurized sections.

If you allow wilderness refueling from large bodies of water as well as from gas giants...

Naval d-tons may make more sense.

 

[BwapTED]

In 1977 rules, we don't know what the fuel used is, though hydrogen or helium of some sort seems possible, given you can get it from skimming a gas giant.


That's made quite clear a couple of years later.

Maybe the d-ton is used because the star-ship displaces x amount of hydrogen 'fuel' released to form the jump 'bubble'?

You have to watch that because overloading the bubble pops it. Misjump or no jump at all.

I'll have to go back and look at that JTAS article to see how Marc Miller explained jump.
I might be reinventing the wheel.


Or is the jump field stuff mostly explained in an OOP MegaTraveller book?

 

[aramis]

Several guys have suggested the ships would indeed float because of the fuel (or near- vacuum, if emptied) in the tanks and the air in the pressurized sections.

If you allow wilderness refueling from large bodies of water as well as from gas giants...

Naval d-tons may make more sense.

A Naval dT is directly linked to mass, as it's the water displacement of idealized seawater. It relates, in warships, to about 4 cubic meters of volume enclosed.

 

[BwapTED]

A Naval dT is directly linked to mass, as it's the water displacement of idealized seawater. It relates, in warships, to about 4 cubic meters of volume enclosed.

Right.

 

[GypsyComet]

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

No, sorry, it is not a mass unit. Top of Page 10 has the definition. Hulls are repeatedly referred to as having a "size", not a mass. The drive tables use "Mass" as an abbreviation for Mass Displacement, which is explained just below the table. For that usage to change mid-process would make no sense whatsoever.

While fuel is not explicitly defined in Book 2-77, it IS stated that unrefined fuel is skimmed from gas giants (page 9), which narrows the range of candidates considerably. The Technology table in Book 3 (Page 11) defined TL8 and above as using Fusion. At the time of writing, that really only meant hydrogen.

The argument that nautical displacement tons and Traveller 77's "mass displacement" are the same is missing the conversion factor inherent to the nautical unit: Boats gotta float. A nautical vessel that displaces X tons of water has an actual mass that is very close to that because the need to float converts the unit back to mass. Traveller's displacement ton is not the same thing. There is no flotation conversion to take "mass displacement" back to "mass".

*Traveller "mass displacement" is in fact a volume, and a volume only.
*The entire ship construction and economic system uses mass displacement, even when it says only "mass".
*Any other conclusion assumes a conversion that is never stated, clarified, or even hinted at.

 

[BwapTED]

No, sorry, it is not a mass unit. Top of Page 10 has the definition. Hulls are repeatedly referred to as having a "size", not a mass. The drive tables use "Mass" as an abbreviation for Mass Displacement, which is explained just below the table. For that usage to change mid-process would make no sense whatsoever.

While fuel is not explicitly defined in Book 2-77, it IS stated that unrefined fuel is skimmed from gas giants (page 9), which narrows the range of candidates considerably. The Technology table in Book 3 (Page 11) defined TL8 and above as using Fusion. At the time of writing, that really only meant hydrogen.

The argument that nautical displacement tons and Traveller 77's "mass displacement" are the same is missing the conversion factor inherent to the nautical unit: Boats gotta float. A nautical vessel that displaces X tons of water has an actual mass that is very close to that because the need to float converts the unit back to mass. Traveller's displacement ton is not the same thing. There is no flotation conversion to take "mass displacement" back to "mass".

*Traveller "mass displacement" is in fact a volume, and a volume only.
*The entire ship construction and economic system uses mass displacement, even when it says only "mass".
*Any other conclusion assumes a conversion that is never stated, clarified, or even hinted at.

That makes very little sense. Why wouldn't it just read 'volume'?

What is being displaced?

Or are you suggesting what I've suggested up thread--mass displacement derives from the physical requirements of skimming gas giants for fuel?

Note that page Book 2, page 43 clearly shows a ton as a weight/mass unit. It seems to be the metric tonne.
But it may be that these tons are not the same tons used in ship design. That would leave the referee to figure out the volumes of various cargoes. So, no, sorry, but the entire economic system does not use mass displacement.
Was that changed later?

A Naval dT is directly linked to mass, as it's the water displacement of idealized seawater. It relates, in warships, to about 4 cubic meters of volume enclosed.

This makes sense.

Pure volumic tons makes no sense when the rules define tons as a measure of mass displacement. You can explain it as 'Vilani engineers wrote Book 2' but it still feels like a handwave to me.

But people should handwave as they please!

I do.

 

[mike wightman]

The trade rules make it explicit that the cargo ton is 1000kg.

Now in ship design you end up with a cargo hold of mass displacement 100t - it can carry a maximum of 100,000kg of cargo. That could be ten ATVs, twenty five air/rafts, 100tons of uranium fuel rods etc.

If you use the volume based displacement ton your cargo hold can take 1400 cubic metres of cargo - how much uranium is that by mass?

26,600 tons is how much - does that sound right? A 400dt merchant (rough estimate mass 4000 tons) can still maneuver at 1g even though it now has a loaded mass of 30,600 tons.

Note that in 81 edition, TTB and ST the same trade rules exist and cargo is still metric tons rather than displacement tons, even though the displacement ton is now defined in starship construction. So while your cargo bay is definitely 1400 cubic metres you can only carry 100 metric tons as the mass limit.

 

[BwapTED]

The trade rules make it explicit that the cargo ton is 1000kg.

Now in ship design you end up with a cargo hold of mass displacement 100t - it can carry a maximum of 100,000kg of cargo. That could be ten ATVs, twenty five air/rafts, 100tons of uranium fuel rods etc.

If you use the volume based displacement ton your cargo hold can take 1400 cubic metres of cargo - how much uranium is that by mass?

26,600 tons is how much - does that sound right? A 400dt merchant (rough estimate mass 4000 tons) can still maneuver at 1g even though it now has a loaded mass of 30,600 tons.

Note that in 81 edition, TTB and ST the same trade rules exist and cargo is still metric tons rather than displacement tons, even though the displacement ton is now defined in starship construction. So while your cargo bay is definitely 1400 cubic metres you can only carry 100 metric tons as the mass limit.

That's how it looks to me.


Cargo is measured in mass and also cannot exceed the volume of the hold.

 

[mike wightman]

When deck plans were needed back in the day they would be sketched out on the same paper used to map D&D dungeons. The good old 10' square. Make it a 10' cube and you have 1000 cubic feet.
That is approximately the equivalent of 2dt of liquid hydrogen fuel.

Better still is to use the 5' square that was often used for combat and you get 250 cubic feet, so two squares becomes 1dt of liquid hydrogen.

Now metrificate (not a real word) 5' square becomes the good old 1.5m square with a 3m ceiling, giving a 6.75 cubic metre 'square' - two of these make 13.5 which is pretty close to the 14 cubic metres that 1 ton of liquid hydrogen displaces.

Now since a jump ship has lots of fuel tankage you allocate lots of squares to fuel, but what is the density of a jump drive, a stateroom etc? Solution - handwave it.

A 4t stateroom becomes 8 deckplan squares, a 10t jumpdrive becomes 10 deckplan square etc.

Striker gave us a design system that required you to track mass and volume as separate parameters, and I can not be the only one who tried using Striker to build starships, but there are major issues.
Those issues would plague DGP when they tried to unify Striker and Ship construction and wouldn't be fixed until we got FF&S for TNE.

 

[mike wightman]

That's how it looks to me.


Cargo is measured in mass and also cannot exceed the volume of the hold.

The important thing is the cargo can not exceed the mass limit of the hold either.


100dt of cargo hold filled with 100 metric tons of water will allow you to make 11 tons of hydrogen.

A 100dt cargo hold filled with 1400 metric tons of water (the volume capacity of the hold) will allow you to make 155 metric tons of hydrogen, which means you are better off carrying water than additional fuel tankage

 

[GypsyComet]

The trade rules make it explicit that the cargo ton is 1000kg.

Not really. The explicit statement is only part of the break-bulk guidelines, which also suggest de-emphasizing the masses coming from the equipment section (which is not within ship econ).

The implication from this line of reasoning is that two ships, one built as a gun runner and the other as a bulk grain carrier, with otherwise identical construction characteristics, are going to have different sized cargo bays on a map. The size of these bays has no guidelines in the rules. None.

*Ship tons are always the same size, because ships only care about size, at least in CT.

That makes very little sense. Why wouldn't it just read 'volume'?

What is being displaced?

Or are you suggesting what I've suggested up thread--mass displacement derives from the physical requirements of skimming gas giants for fuel?

Not the physical requirements, but the physical characteristics. The fuel ton is the benchmark for the entire system, though that would not become clear until later: A mass displacement ton, later called just a displacement ton or dton, is defined as the volume occupied (ie. displaced) by one metric ton of fuel. Because the fuel is further defined as a form of cryogenic hydrogen, the volume of a dton is also defined numerically.

Pure volumic tons makes no sense when the rules define tons as a measure of mass displacement.

That just means you aren't understanding the units involved. This may be a side effect of referring only to CT77, a rule set written during the dawn of RPGs by a group of people that did not include an engineer or physical scientist.