General Math Sucks: Cargo Containers

[AnotherDilbert]

1. Does propulsion depend on weight or volume?

FF&S explains it:

TNE FF&S, p69:
Thrust requirements are abstracted by tying thrust energy requirements to hull displacement rather than craft mass. This is an obvious abstraction, but one which is necessary for ease of design. Too many variables affect ship mass throughout the design process, and tying thrust to mass would require you to continually redesign and redesign to get a workable craft. In our opinion, the thrust-to-mass formula is a workable compromise, especially since spacecraft tend to have the same general density. The correction factor for very high mass-to-volume designs takes care of any important distortions.

In essence it's really mass, but we use volume instead for simplicity.

2. Can the floor handle the heavier interpretation?

There is presumably some limit, as with any engineering. Perhaps about 1 tonne/m³ is normal, with a bit of safety margin.

In other words, if you stuff your Free Trader full of lead, it will not lift off, but probably break apart...

 

[Rigel Stardin]

The lesson I learned from the Gazelle Study. You can mold anything into a 400 ton volume limit. Length, width and height can change (volume) but it still a 400 ton volume.

 

[Condottiere]

Probably would have to reassess fully armoured buffered planetoid monitors.

 

[Rigel Stardin]

in MTU, armor add weight it can also reduce volume as well.

 

[kilemall]

The original CT had it as 1000kg per freight ton, a figure that has still snuck in to the passenger high passage baggage rules even unto MgT rules.

So this conflation of weight and volume is literally old baggage.

 

[Spinward Flow]

Gravity can change in a cargo hold with gravity control, but mass won't.

I need to know the actual weight a container can carry for a story I'm writing.

14,000 liters or 1000kg per "ton" ... whichever comes first ... is the carrying capacity equivalency.
If you hit the mass limit before hitting the volume limit, the extraneous volume is simply considered "packing material" (LBB2.81, p48).

 

[Rigel Stardin]

Okay, a standard cargo container, 3m by 1.5m by 3m is almost the same as the real world counterpart.
A 3m by 3m by 3m cargo container is twice the size as a Standard and listed on wiki and carries 2 tons.
6m by 3m by 3m or 4 ton container is listed as carrying 4tons. Real World Counterpart, 5.8 by 2.4 by 2.5, weights 2 ton but carries 21,000 kg or 21 metric tons.
12m by 3m by 3m is listed as carrying 8 tons. Real World Counterpart, 12.2 by 2.4 by 2.5 weights 4 tons but carries 26,000 kg or approximately 26 metric tons.

"So there is a discrepancy between the real world and the game, big deal. Game trumps real world any day."
"But the game, figures out cargo space by volume. Okay."
"That 3m by 1.5m by 3m floor space is equal to 13.5 tons. So that means I can put a 12 ton object with those measurement are the same in that location right?"
"Er no, your confusing mass with volume. An object that size can only weigh 1,000 kg by the rules."
"But that Tracked Vehicle over there (Measurements 4.8m by 2.6m by 2.5m and weighs 12 tons) is fine."
"Yes it is."
"Sorry but that Tracked Vehicle weighs 12 ton and it fits into the space of a 4 Ton Cargo Container space..."

Does anyone else see the mental gymnastics, I have to go through?

 

[kilemall]

Maybe I missed it but didn’t see the classic Freelance article on dton posted-

Freelance Traveller - The Shipyard - What is Tonnage?

www.freelancetraveller.com

IMTU I assume the 5 ton and 10 ton freight lots correspond to standardized containers that are that size, and they are just a bit bigger then our TEU/FEUs. Not a problem for an interstellar society that can build to larger road widths and advanced grav tech worlds are flying their cargo around anyway.

Tons mean different things anyway in RL, just have to keep in mind which reference ton you are using.

For your purpose I would suggest using online material density per square meter sites/calculators. Then you can plug it into your volume space and Mcguffin your way through.

Here is one that lists almost anything you would want to bulk ship- figure out how many cubic meters your space is, plug in the kg for the item or the closest terrestrial equivalent and go.

Mass, Weight, Density or Specific Gravity of Bulk Materials

Mass, or density, of over 80 different Bulk Materials from bauxite to zinc ore

www.simetric.co.uk

 

[Rigel Stardin]

It's not as much about bringing the real world into the game as it is about keeping it simple and relatable. One thing I learned doing the research on Shipping Containers, size doesn't matter it the structural element that does. The weight carry by a 20' container is more than a 40' container, it's either by regulation or structural elements, maybe even the crane's standard capacity. Your brain cells tell you a shipping container twice as big should carry twice the cargo but, real life said it doesn't. In a game or story that doesn't involve fantasy, you keep to what your simple brain understand, so a 20' container weighs less than 40' container in the near or far future. It makes it believable to the reader and PC.

Second thing, back in my gaming days, there was always this constant argument about whether or not an ATV could fit into a 3 meter tall cargo bay. The measurement and weigh, I gave for the Track Vehicle I gave you are from an M113 APC used by several military's around the world including the US. I know for a fact, you would have to remove the 50 cal to fit it into an aircraft because of door restraints and bay height. Point is, a tracked ATV could fit if it wasn't fitted with a turret into a standard 3 meter but a wheeled ATV couldn't. That was either because of the sensor dome or turret.

My brain has fits when, in a ship's description 'cargo hold can carry a wheeled ATV' this was back in the day when I had only LLB to rely on. I was also in the military and knew such details. Which brings me to the next glaring issue with cargo bays in general. If not stated in the description of the ship, the Ship's Cargo Bay has a height of 3 Meters. Those 3m by 3m by 3m cargo containers would never fit unless you modified the ship or is there some unwritten rule I don't know about that explains this?

That doesn't bode well for the owner of a Scout who just landed a contract to move a 3m by 3m by 3m container. Because everyone should be aware a door is smaller than the opening. Put it in space and you have seals to worry about as well. So you can use 3 by 3 by 3 to describe the Cargo Container but not the actual dimensions because of reason already stated. It has to be smaller than the opening.

Enter the real world once again, I assume the contain is slightly smaller. Looking over the Shipping Container graphs, I notice they are all 2.5 meters tall. Makes sense. Standardization allow global markets to thrive and would make sense on a galactic scale as well. But now, I've reduced the cargo container by half a meter. This is what sent me down the rabbit hole. You could kept the Length and Width in most cases but the Height has to change. That changes the cargo weight inside, I also noticed interior measurements were different from the exterior by .2 meters. Makes sense as well. Again, it changes the cargo weight. And here we are.

Getting the information about Gurp's cargo container helps me because it sets a standard I can follow from an in game source. Which is 445 kg of cargo per cubic meter. So I can say a 3 by 3 by 3 measurements are:

Exterior: 3m by 3m by 2.7m.
Interior: 2.8m by 2.8 by 2.5 or 19.6 cubic meters

so we end up with 8,722 kg or 8.7 metric tons of cargo.

I'm really debating on change the 3m width because some cargo containers need to fit though a cargo bay door without scratching the paint.

 

[Condottiere]

1. I think it's going to be regional and corporation based standards for containerization.

2. It's possible that the Imperium will impose a top down standard(s), if only for the military and Imperium institutions.

3. Other cultures/civilizations have different measurements.

4. The Vargr have doggy bags.

 

[kilemall]

I don’t worry about the ceilings so much as I figure containers get attached top and bottom.

I wasn’t pushing the 3x3x3 as any kind of standard, the article is helpful for visualization.

2.5m height 2.5m width 11.5m length for 5 dtons and the same with 23m length for 10 dtons. That’s predicated on some fudge factor with 14 cubic meters, I’d let that cover the tare volume and what is left for cargo is 13.5 cubic meters per ton.

As mentioned before by others, whatever the strength is of the container whether the LBB5 numbers or others, if you are factoring weight as a limit then there will be waste volume space. This happens now with material loaded on RL shipping containers- heavy things like furniture wood or feed grain.

Good example is rail cars that carry iron ore or fracking sand/cement are much shorter because the limiting factor is load per axle and the cargo is very dense.

So for a cargo scenario counting the kgs, it should matter quite a bit as to what is loaded and of course you don’t want those loads sloshing around.

As for space worthy, I just go with starship hull per dton cost for external/vacuum ops containers and 10% the cost for must be pressurized cheap containers.

More on all the variables I went into for containers as a side hustle/merchant complication mechanic in this thread, no point in duplicating-

https://www.travellerrpg.com/index.php?threads/my-tc-universe.34302/page-3#post-508352

The referenced one gets into differing cargos, payoffs to handle, the following one gets into container rules.

 

[mike wightman]

The Imperium imposes the standards for every member world in both civilian and military parameters.

Vargr are not and never have been dogs, as MWM himself has pointed out in one of his short stories it is a racist trope used by Imperials.

 

[Condottiere]

I suspect that goods shipped through Imperium controlled starports do have to adhere to the standards the Imperium imposes.

However, megacorporations within their own networks can write their own standards, and regionally, as long as their standards fall within Imperium ones, they can set additional ones.

 

[mike wightman]

Outside the Imperium you can do whatever you can get away with, within the Imperium you follow their rules or else...

 

[tjoneslo]

The Office of Calendar Compliance would like to have a discussion with you about your non-standard cargo containers.

 

[Condottiere]

That seems rather inefficient, especially if the containers in question stay within your own network.

There being no recourse if other interstellar shipping companies refuse to accept them.

 

[mike wightman]

"I'm very sorry but that cargo container you have brought from Arglebargle is 2mm longer than Imperial regulations allow. We will be impounding all non-regulation containers and selling their contents at auction"

 

[Rigel Stardin]

"Sorry, you container does not conform to ISU-900b. Besides that, your container cannot be secured to the deck using Imperium Stardard Clamping mechanisms in the floor of our cargo hold. You're just going to have to find another shipper or buy one of our containers."

 

[Condottiere]

Matryoshka doll.

I think a kilotonne container was mentioned, and undoubtedly there are larger, and you'll need to subcontainerize those, ad infinitum.

 

[mike wightman]

And hey presto you have invented a market for shipping and selling shipping containers - wonder who makes them?