Mating Airlocks to Cargo Hatches

[phavoc]

The five ton model is in the Robot Handbook, so blame @Geir.

How about a flatbed vehicle with a winch to pull them onto a tiltable flatbed? Toss in 9 arms to attach tiedowns and you're golden, right? This can handle up to 8 dtons of container (the largest standard size).

View attachment 5403

Pretty much describes tow trucks with beds (though, I suppose, you could describe a regular tow truck with it's "grappler" in the back that picks up the car and tows it.

If you've seen the PODS movers, they have a wheeled lift that picks up the pod and drops it wherever and also loads the truck with it. It has telescoping wheel/arms to lift up the container. It's ingenious ultra-low tech, as it uses chains under the pod for lifting instead of trying to have a fixed apparatus. It's somewhat similar to a Mi-Jack lifter seen at rail yards that is also on wheels and it straddles the rail car and the truck underneath it. It lifts up the container from the rail car and moves it over and drops it down on the trailer. For a starship it wouldn't work well since it can't get into the holds (and regular cargo ship container cranes also wouldn't work since they operate on a similar ideal. However, once you add in grav tech it becomes very easy to lift from the top and move it out. The only thing you'd need is sufficient vertical clearance for your lift mechanism in the hold. We already hand-wave a lot of that for ship deckplans, so I'm comfortable with the idea that sufficient, if minimal, space is there to make something like this work.

It's basic, simple and fixes all of your logistical move problems in one fell swoop.

 

[phavoc]

Nets and tow cables.

Probably have to follow terms and conditions of service, especially in regard to vacuum exposure.

Lack of atmospheric pressure probably would cause frozen pork bellies to explode.

Just one more kipper.

 

[phavoc]

Depressurisation of the cargo hold is only NEEDED if you don't have a cargo airlock and if you transfer cargo in open space. Depressurising is an option that can bring benefits (but also imposes disadvantages).

You don't need to depressurise if you load:
on a low port where the planet has an appropriate atmosphere
on a low port where the planet has a difficult atmosphere but a sealed docking bay
on a high port with a sealed docking bay
Those three conditions are pretty likely in the majority of cases in my opinion as those offer the quickest route for unprotected cargo and crew to transfer between ship and port.

The purpose of an airlock is so that you can move something into the non-ship atmosphere (be that vacuum or toxic atmosphere etc.) without exposing the entire ship to that non-ship atmosphere. If that is the situation then the thing being moved needs to be independently protected from the non-ship atmosphere once it gets out there. If you are moving standard containers that cannot withstand the non-ship atmosphere then you will not be connecting to a non-ship atmosphere and so you don't need an airlock.

If you are making a semi-permanent connection between two ship type atmospheres you don't need it to be an airlock, including if you dock with onto another ship while in space. The connection itself is the airlock (which is what I think the OP was suggesting).

Small Craft makes it clear that containers iiiiiin spaaaaace is a thing. They will be protected containers but to load them you just need to depressurise the cargo hold while you load them. If you want to repressurise afterward that is your option.

Since we don't seem to have any definitive information about the different types of container other than listing the types (which seem to be read across from real world ISO containers and extrapolated for space needs):
It could be that standard containers are not the most common in space transport and are limited to planetary use.
All space going freight might use airtight containers, the non-airtight ones are in use in benign atmospheric environments.
Containers may only spend a relatively short time in transit, not long enough to loose much air.
As you are paying by the DTon you probably want that container packed so full that there may not be much air in there anyway.
Temperature control is also an issue but this is true for many goods in benign atmospheres too, this could be cheaply achieved.

The cost of an airtight standard container might not be significantly higher than that of a non-airtight one. Standard containers could be one use (many real world ISO containers are). The cost is still low compared to the cost of the contained goods plus the cost of movement but that may be because we are wasteful of resources. Most real world ones are also exposed to a hostile environment (sea crossings) and salt corrosion and contamination from the contents might render them uneconomical to re-use . They are the padded envelopes of the shipping industry. Special purpose containers may cost more, but they also seem to be re-used. Overall the cost per use might actually be lower.

The difference in pressure between a standard atmosphere and absolute vacuum is 1 atmosphere. A beer bottle can withstand several atmospheres pressure and usually has a factor 3 safety margin. A bottle of beer left in a sealed but evacuated hold will be fine. In open space it might be irradiated if in sight of a radiating body and the contents boil to the point of bursting the container or alternatively if it isn't it will freeze and burst the container. It will also be subject to other forces (cosmic rays, micrometeors, non-gravity - best have a high gravity beer). If it was in a metal box with a decent thermal mass and proof against cosmic rays it could probably be transported though open space from the shuttle to the cargo bay of the receiving ship without too much trouble. I don't think a washing machine would care one jot.

Consider where these are going to and from. After unloading or while awaiting loading they might well sit in a container park for an extended period. If you are unloading/unloading somewhere with a non-benign environment standard containers must be stored inside. If they are protected containers you can stack them up outside (as many real world containers are). Internal storage space tends to cost a lot in an environment that needs it. The cost of building and maintaining a shelter, which needs to be as big as the peak DTonnage it will store plus extra for access, airlocks, equipment to maintain the environment etc. will likely far outweigh the additional cost of protecting some containers and you only need to protect the containers you use. If you store outside you only need enough airlock to handle one container at a time. It is likely the containers will be destined elsewhere than the port and will need to be protected for that part of the journey as well. The customer may be perfectly happy to pay extra shipping costs to have a protected container at the end point to reduce his own storage overhead. That protected container may end up forming a permanent part of a remote facility offsetting the additional cost the shipper will pass onto the customer.

Most of the cargos IMTU are also being moved in cutter modules and either being manoeuvred into holds as a unit or are clamped externally. As such the cargo bay pressure is largely irrelevant as the module itself ensures the correct atmosphere. Where individual cargos are loaded in space it will be via small utility pods and in sealed cargo containers. Loading at high ports and on inhospitable planets is conducted entirely in sealed docking bays. Only when smuggling does this become more interesting - as it should.

I agree with you about having to depressurize an entire hold if you are moving cargo in total deep space. In that case your containers would either be space-rated (making them much more expensive - especially if you were putting even low-G grav plating in them), or they'd need some other form of vacuum-proofing. I got around that myself with by coming up with a cheap polymer lining that is a one-use thing. The insides of a standard container are sprayed with a thin lining making it a vacuum-sealed environment. Once the doors are closed it's sealed, and when you open it you have to reapply it. It's meant to be a cheap way way to bridge the gap, and obviously not being reusable without re-applying means you can't 'cheat' and avoid the cost of space-rated containers. It's not like PC's try to min-max everything....

Cargo airlocks do make sense, but it's also an added expense and added tonnage to a ship. Small ships can't afford that (like a free trader), but a 10,000 dton ship could do so. Smaller ships might cheat their way through this by having multiple holds, each one sealed, and then cycle from the one that has the external hatch to the ones on the inside. It works, but not efficiently.

Container types should follow the existing model like you mentioned - you have the standard ones and then you have the seagoing ones. A sea going container is built of steel and is designed to be weather resistant and much stronger to protect the internal cargo from the harsh sea environment. They are also more expensive than the cheaper aluminum or even fabric-sided containers that only need to keep the weather out. The reason for that boils down to cost. No merchant is going to pay for things they don't absolutely need - that maxim has been in force for millenia and would continue onwards into the future (now, change the race and you may change that rule). One thing on re-use though - it varies based on the amount of cargo going back to the exporting country. The US is a net-importer of goods in containers and you will see many Asia-bound ships leave empty or with small container loads (as opposed to showing up with 10-15k TEUs worth of loaded ones). The reason for that, again, is cost. Sometimes its just cheaper to make a new one in China than for that container to make its' way back from being unloaded. Seems stupid, but it's just economics. Once the price/availability of steel goes back up it becomes more economical to ship them back empty. In space trade I don't see any empty containers going back for reuse (at least on starships). The economic model there doesn't work well with running empty (even though operational costs are basically fixed if at 0% or 100% full). I read somewhere of the 16(ish) million cargo containers out there, only about 6 million are actively used to transport sea cargo - the rest are repurposed to all kinds of other things - including regular ground transport. Which since they are steel makes perfect sense.

I worked my way through college at UPS loading the sem-trailers you see on the road. For manual loading of so many different packages we actually did take advantage of a LOT of space - but except for the training film where every box was of universal size and shape (which was NOT the reality!), "efficiently" loading the truck was building walls of packages that didn't shift or crush the ones underneath. We certainly weren't tall enough to reach the top, so basically the top 18-24" was left for loading bags of small packages (tossing them up there to be more precise). Speed was valued above all else because we had timelines we had to meet for loading the packages and to give time for them to get to the railyards or for drivers to pick them up to drive to their next hub destination. Since we never had to build loads for zero-G environments I can't say how well we might be able to adapt (or not) to it using the same principle that boxes are rarely going to magically fit together as seen on the training video.

Good stuff!

 

[Condottiere]

Cargo airlocks, or even passenger airlocks, cost, depends.

If you use the default, hundred kilostarbux per tonne.

But, you get all the standard features.

Or, you add an extra vacuum proof door in a corridor or cargo hold wall.

Since I don't recall ever mention of the costs of a vacuum pump and vacuum proof door, it could be essentially free.

 

[Terry Mixon]

I agree with you about having to depressurize an entire hold if you are moving cargo in total deep space. In that case your containers would either be space-rated (making them much more expensive - especially if you were putting even low-G grav plating in them), or they'd need some other form of vacuum-proofing. I got around that myself with by coming up with a cheap polymer lining that is a one-use thing. The insides of a standard container are sprayed with a thin lining making it a vacuum-sealed environment. Once the doors are closed it's sealed, and when you open it you have to reapply it. It's meant to be a cheap way way to bridge the gap, and obviously not being reusable without re-applying means you can't 'cheat' and avoid the cost of space-rated containers. It's not like PC's try to min-max everything....

Cargo airlocks do make sense, but it's also an added expense and added tonnage to a ship. Small ships can't afford that (like a free trader), but a 10,000 dton ship could do so. Smaller ships might cheat their way through this by having multiple holds, each one sealed, and then cycle from the one that has the external hatch to the ones on the inside. It works, but not efficiently.

Container types should follow the existing model like you mentioned - you have the standard ones and then you have the seagoing ones. A sea going container is built of steel and is designed to be weather resistant and much stronger to protect the internal cargo from the harsh sea environment. They are also more expensive than the cheaper aluminum or even fabric-sided containers that only need to keep the weather out. The reason for that boils down to cost. No merchant is going to pay for things they don't absolutely need - that maxim has been in force for millenia and would continue onwards into the future (now, change the race and you may change that rule). One thing on re-use though - it varies based on the amount of cargo going back to the exporting country. The US is a net-importer of goods in containers and you will see many Asia-bound ships leave empty or with small container loads (as opposed to showing up with 10-15k TEUs worth of loaded ones). The reason for that, again, is cost. Sometimes its just cheaper to make a new one in China than for that container to make its' way back from being unloaded. Seems stupid, but it's just economics. Once the price/availability of steel goes back up it becomes more economical to ship them back empty. In space trade I don't see any empty containers going back for reuse (at least on starships). The economic model there doesn't work well with running empty (even though operational costs are basically fixed if at 0% or 100% full). I read somewhere of the 16(ish) million cargo containers out there, only about 6 million are actively used to transport sea cargo - the rest are repurposed to all kinds of other things - including regular ground transport. Which since they are steel makes perfect sense.

I worked my way through college at UPS loading the sem-trailers you see on the road. For manual loading of so many different packages we actually did take advantage of a LOT of space - but except for the training film where every box was of universal size and shape (which was NOT the reality!), "efficiently" loading the truck was building walls of packages that didn't shift or crush the ones underneath. We certainly weren't tall enough to reach the top, so basically the top 18-24" was left for loading bags of small packages (tossing them up there to be more precise). Speed was valued above all else because we had timelines we had to meet for loading the packages and to give time for them to get to the railyards or for drivers to pick them up to drive to their next hub destination. Since we never had to build loads for zero-G environments I can't say how well we might be able to adapt (or not) to it using the same principle that boxes are rarely going to magically fit together as seen on the training video.

Good stuff!

Getting around the need for a cargo airlock on the ship was why I made the extendable cargo airlock. It works well for pods where the location of the cargo hatches could be standardized but I’d imagine it would be less effective for a ship where it might be more random.

 

[Terry Mixon]

As the section where the containers speaks of loading the various sizes into ships, it follows that the intent was for the most common (standard) container being the most used in ships. The SOM isn’t talking about planetary shipping. It’s in space.

That said, this is Traveller. If you don’t like the standard being unpressurized and want to have no air in your cargo holds, do that. This is aimed at folks that don’t have that outcome already decided.

 

[Terry Mixon]

Actually, my calculations came up with a forty foot container being five tonnes.

The 8 ton is 9.84 feet tall and wide and 39.37 feet long. Here are the container sizes.

 

[Condottiere]

70/11.56 = 6.055363321799308

6.055363321799308/2.28 = 2.655861106052328

 

[Sigtrygg]

Something is very wrong with the maths for that container illustration.

The capacity is listed as 67.3 m³, and yet the internal dimensions given 2.25 x 2.28 x 11.56 = 59.3 m³

 

[Condottiere]

Luckily, there are hundreds, if not thousands, of entries on the internet to doublecheck dimensions.

I decided to standardize on the forty footer, since it's the smallest hull size.

Exact dimensions can vary, to something that you can easily slip in in a given cargo hold, to some ergonomic standard.

I have something smaller at two tonnes, that would take up four squares.

 

[swordtart]

I agree with you about having to depressurize an entire hold if you are moving cargo in total deep space. In that case your containers would either be space-rated (making them much more expensive - especially if you were putting even low-G grav plating in them), or they'd need some other form of vacuum-proofing. I got around that myself with by coming up with a cheap polymer lining that is a one-use thing. The insides of a standard container are sprayed with a thin lining making it a vacuum-sealed environment. Once the doors are closed it's sealed, and when you open it you have to reapply it. It's meant to be a cheap way way to bridge the gap, and obviously not being reusable without re-applying means you can't 'cheat' and avoid the cost of space-rated containers. It's not like PC's try to min-max everything....

You could combine this with the packing solution. If your liner was a flat bag (or rather 6 linked flat bags each covering a face of the container) make of super strong flexible polymer, you could put it between your cargo and the walls of the container. When you are loaded you inflate it and it acts like an inflatable cast and fills the gaps between the cargo and the sides of the container. Only the bag needs to be airtight as it fills any remaining space and would also seal any gaps in the container (like fothering a ship). When it comes to unloading you just depressurise the bags.

The air gap would provide a degree of temperature buffering. The contents would still loose heat but the temperature gradient between hull and cargo would be more shallow (especially if the bag were covered with a metallic film to act as a radiant barrier).

This would either be cheap and need regular replacement as it would not resist sheer pressure well or more expensive and robust. It would be a business decision which would be more appropriate depending on the anticipated use case.

A space worthy container might have a more robust version as part of its construction with expanding walls to fill any air space but this top-tier solution would obviously cost more. Something for the mega corps perhaps.

 

[Condottiere]

 

[swordtart]

I had a car battery shipped in a box that was about 2" wider in all dimensions. The packing was genius, a bin bag filled with expanding foam. The foam provided rigidity and stopped even such a heavy object from shifting and the bin bag protected the battery from the foam. It lifted out easily leaving a perfectly clean box ready for recycling. The only problem was the expanding foam is an issue environmentally as it is single use, hence my suggestion that in the future we'll have solved the problem using inflatables.

Packing you cargo pod with space hoppers as an austerity work around would be ironic.

 

[Condottiere]

You can recycle the air.