Cargo Weight/size isn't being done right...or I'm wrong

Balfuset790 · Jul 17, 2015

As a fan of a tabletop RPG by the name of Traveller which some people may be aware of I always consider the 'ton' in this context to be a displacement ton as opposed to a ton as a measurement of weight.

Obviously, displacement tonnage is a measurement used in actual naval measureements today, representing the amount of water displaced by a ships mass, but in this context, and in the RPG Traveller, a displacement ton is a volume of 14 cubic metres, or there about, which is a sufficiently sized cargo container to hold one metric ton of liquid hydrogen fuel.

Regardless, dispalcement tonnage is a measurement of volume rather than mass, and that seems to work more reasonably, especially when weight is meaningless in a microgravity environment

Robert Maynard · Jul 17, 2015

Balfuset790 said:
Regardless, dispalcement tonnage is a measurement of volume rather than mass, and that seems to work more reasonably, especially when weight is meaningless in a microgravity environment

If by weight you mean mass, it is entirely meaningful when one starts to think about moving the ship or turning it (without ripping it apart)....

Balfuset790 · Jul 17, 2015

Robert Maynard said:
If by weight you mean mass, it is entirely meaningful when one starts to think about moving the ship or turning it (without ripping it apart)....

No I mean weight. Weight being a function of mass and gravitational force. Mass always has meaning, regardless of ambient gravity, as it's a scalar measurement rather than a vectored measurement.

Robert Maynard · Jul 17, 2015

Balfuset790 said:
No I mean weight. Weight being a function of mass and gravitational force. Mass always has meaning, regardless of ambient gravity, as it's a scalar measurement rather than a vectored measurement.

Indeed. And given that thrusters apply forces to our ships, too much mass in the wrong places could be a very bad thing....

Vyvian · Jul 17, 2015

jacozilla said:
Well FD is using metric tons in fuel scooping - it rates the scoop based on max inflow, say 0.18 T/s - and then in your hud when you are scooping it will show a rate of 180 / s which would be exactly right if it is metric tons (0.18 T/s = 180 kg/s)

I think the container ship analogy is the best fit. Modern container ships all have a tonnage capacity to be sure, but no one counts or refers to shipping in that way - they rate both the ship as well as the cargo hauled in terms of #containers or standardized TEU

So instead of referring to the shipping tonnage, it's just this Panamax ship is rated at 10,000 TEU cargo ability, or this ULCV even bigger than a panamax is 14,000 TEU

So I figure it's not that a ton isn't a ton, or mass and weight are being confused, it's just the labels for our ships are wrong / misleading.

Our ship that says has max cargo of 100 tons is basically saying 100 TEU - you can part fill it, you can fully fill it to max capacity, but you pay the same shipping rate as it takes the pallet position of a container. Given orbital stations, and example of modern shipping - getting the goods to the dock is the easy part. Unloading all that crap is the logistical nightmare.

So what we probably don't see is our ships dock at a station and then some standardized robo hauler pulls up to pickup and pull whatever standardizd cargo pallet the FD universe uses.

the only kink I can think of in this line of reasoning is that for small volume, heavy mass items like gold, I don't see why people wouldn't fill the damn container to the max and therefore ship more 'tonnage' of gold unless mass was the primary penalty, in which case then no single 'tonnage' rating applies - it would have to be a different value based on whatever good you are shipping, as a combo of both mass and volume needed.

Robert Maynard said:
Presumably this isn't permitted because the safe working load of the framework that canisters are locked into in the cargo bay is the empty mass of the canister plus 1,000kg of cargo.

lien_leposh said:
Likewise, the forklift trucks, etc on the surface of planets might be standardised for the canister size and max mass of 1000kg + canister...

Does this make me a Tory* politician? I'm making things up to justify my warped view of reality?

*other political parties also available.

All of this is why it makes sense to me that all the cargo canisters are 1 ton. Though in fact it seems we are purchasing 1 ton of goods minus the weight of the canister, so possibly around 750kg of the goods.

@jacozilla: The max weight allowed for a 40ft shipping container, and please correct me if I'm wrong, is 30,480kg. If you can fill it with Gold and its combined weight is this or less then you can ship it for the same cost as any other container. Hate to think what the insurance quote on this would be.

So basically the E: D system is exactly what we see on Earth today. A standardised container size with a max weight for easy loading, unloading and storage.

It's just that in E: D, every container is filled until it reaches its max weight, no matter what goods are in it. So grain canisters would be full, while gold canisters would be mostly empty, but both canisters are made identical to make mechanical handling easy.

Slopey said:
How very random, and at the risk of being off topic, they reconditioned his mind, then after that broke down, convicted him on fabricated charges of child abuse, packed him off to the penal colony Cygnus Alpha, where he subsequently escaped, then caused the Federation no end of trouble, attempted to destroy their command and control complex but changed his mind and the aliens destroyed it anyway, then vansihed to end up on Gauda Prime as a bounty hunter where he was shot by his best mate Avon.

That's about it.

That is about it.

LeetNoob · Jul 17, 2015

Jet Fusion said:
What you can still do in your imagination (please don't one-shot me for using this word) is pretend it's a metric tonne which makes it a volume again instead of a weight.

What? A metric ton or tonne is 1000Kg's, as apposed to a ton which is 907Kg's.
A metric ton is still weight, not volume.

To OP, I brought this up a long time ago actually. You're right, a ton of Gold takes much less space than a ton of Aluminium (by a factor of about 7). But ship transport space is measured in tons instead of volume. Doesn't make sense.

LeetNoob · Jul 17, 2015

Balfuset790 said:
No I mean weight. Weight being a function of mass and gravitational force. Mass always has meaning, regardless of ambient gravity, as it's a scalar measurement rather than a vectored measurement.

so theres a question, when we buy a ton, are we buying a ton of weight on Earth's gravity level or a ton of weight at the 0.1 gravity in the space stations.

Even on Earth, stuff weighs different.

Location	Latitude	m/s²
Equator	0°	9.7803
Sydney	33°52′ S	9.7968
Aberdeen	57°9′ N	9.8168
North Pole	90° N	9.8322

Archgeek · Jul 17, 2015

LeetNoob: The rest of the thread, you should read it.

It makes plenty of sense that space transport's measured in tons and our (standarized by the old GalCorp over a century ago) chromalloy cannisters all mass exactly 1 of 'em -- it was long ago deemed the best solution to sacrifice the ability to carry more of a denser cargo by filling cans up completely for the reliabilty of cans that always massed a single tonne. Far better to lose out transporting several hundred tonnes of lead in a can than to have cargo regularly lost due to stress-related hull breaches or pilots crashing due to wildly fluctuating flight models.

And there's no question of weight, as metric tonnes measure mass, not weight. Two equal masses weigh exactly the same in the same gravity field, and even in different gravity fields have the exact same effect on a ship's inertia and thus flight characteristics.

TL;DR : weight doesn't matter, we're talking mass. Cargo cans were standardized for safety reasons a very long time before the game's events.

Vyvian · Jul 17, 2015

Out of interest, does anyone know what sort of volume would be required for 1 ton of any of the tradable commodities.

How big does a container need to be to hold 1 ton of Grain?

I understand that things like Hydrogen fuel would be hard to determine without knowing a storage pressure, or pesticides without a chemical fomula.

Just wondering how big a container would have to be to be able to hold 1 ton of any tradable commodity in the universe.

If we can work this out we might be able to determine a rough weight for the actual storage container. Of course once we have this we will have to downscale it, as it's weight will have to be subtracted from the the 1 ton base weight.

Robert Maynard · Jul 17, 2015

Vyvian said:
How big does a container need to be to hold 1 ton of Grain?

A quick google puts the density of grain at approximately 0.72te/m³, so approximately 1.4m³.

Hootmon · Jul 17, 2015

Tun definition, a large cask for holding liquids, especially wine, ale, or beer.

Roycie · Jul 17, 2015

If we're going to get Technical, we need Darth Ender in here to set us straight.

(https://forums.frontier.co.uk/showthread.php?t=163810)

LeetNoob · Jul 17, 2015

Roycie said:
If we're going to get Technical, we need Darth Ender in here to set us straight.

(https://forums.frontier.co.uk/showthread.php?t=163810)

He's completely wrong in that thread.

LeetNoob · Jul 17, 2015

Archgeek said:
LeetNoob: The rest of the thread, you should read it.

It makes plenty of sense that space transport's measured in tons and our (standarized by the old GalCorp over a century ago) chromalloy cannisters all mass exactly 1 of 'em -- it was long ago deemed the best solution to sacrifice the ability to carry more of a denser cargo by filling cans up completely for the reliabilty of cans that always massed a single tonne. Far better to lose out transporting several hundred tonnes of lead in a can than to have cargo regularly lost due to stress-related hull breaches or pilots crashing due to wildly fluctuating flight models.

And there's no question of weight, as metric tonnes measure mass, not weight. Two equal masses weigh exactly the same in the same gravity field, and even in different gravity fields have the exact same effect on a ship's inertia and thus flight characteristics.

TL;DR : weight doesn't matter, we're talking mass. Cargo cans were standardized for safety reasons a very long time before the game's events.

First, I was having a bit of fun, commander serious.
second, that's a long way of saying, we don't fill the cans all the way to the top except for the very least dense commodity, because, shut up, that's why.

A ton is measurement of weight, not mass.

"In modern scientific usage, weight and mass are fundamentally different quantities: mass is an "extrinsic" (extensive) property of matter, whereas weight is a force that results from the action of gravity on matter:"

some more stuff

"Mass is not the same as weight, even though we often calculate an object's mass by measuring its weight with a spring scale instead of comparing it to known masses. An object on the Moon would weigh less than it would on Earth because of the lower gravity, but it would still have the same mass."

the rest of the wiki article, you should read it,