Efficient space only freighter design

4 dTon staterooms include corridors, galleys, common areas, life support, and so forth -- they represent all 'the living space for the crew and passengers'; so the three dTons allocated on deck plans reflect that.
Yeah, but in most ship designs there is about a ton of common space allocated per stateroom in addition. The extra ton is usually assumed to be access corridors, which is similar to either a passage between rows of containers or at least enough space to actually flip Tetris shapes around.

But that's just my opinion - since there is already a 'standard', why not make a 5-dton container a TEU and call it good.
so if we look at my basis, 500 tons, as the standard 'large freighter/mega freighter' block, its specifically broken into 2 tons high (6m) 5 tons wide (15m) and 50 tons long (75m)

The idea here is to easily take 5 and 10 ton lots, or multiples of those, and combine them. The assumption is that a single 10 ton lot is 3x3x15m (2x10 squares), and a 5 ton lot is half that (3x3x7.5, 2x5 squares) These are then easy to maneuver and ship in any starport (even a small one), or cargo vessel (like a pinnace or something else, that is presumably not a square, but is streamlined, and therefore long and thin) that needs to move it from the high port to the planet.

Strictly, we should make them slightly less than 3 meters, but i'm rounding for the sake of ease of use in maps and ship design, rather than worrying about that exact match to a real TEU.

Then, the standard chunk used by those freighters is 4 of those (2000 tons) stacked in a square (2 blocks high, 2 blocks wide, total of 12mx30mx75m).
yup, i always assume the other ton of stateroom is for corridor+walls with lifesupport hidden in them (and common area is for actual common area)
I made a bit of a mistake earlier -- I said we could round a 1024 dTon 24m x 24m x 24m cube down to 1000 dTons and call it good. That is not quite right; even though an interstellar empire of the 52nd century might not care much about the standard sizes of sea-freight containers on a primitive, balkanized, back-water world from several thousand years in the past -- there is something a bit more solid in play here. That solid bit is the dTon -- the volume taken up by 1000 kg of cryogenic liquid hydrogen jump fuel. The game already rounds this down from the musical and easy to remember true value of 14.286 m^3 to 13.5 m^3 -- because the latter is easier to draw as 1.5m cubes.

1000 dTons of fuel that you feed to your drive is 14386 m^3, not 13500 m^3; and short-changing your J-drive seldom goes well. So what accounts for the difference? Fudge, mostly. A plus or minus 10% difference between deck-plans and actual specs is often considered 'good enough', and sometimes reasonable folks agree plus or minus 20% is okay, too. I tend to make the up the difference in spacing between decks, of simply under-floor and over-ceiling space -- and a 1.5m deep, 3m wide, 3.175 m tall space is pretty close to the correct volume of a dTon. So decks are more than 3m, and 3m tall (or even 3.15m tall) containers shouldn't have any trouble in areas designed for them -- especially not in double-high cargo decks like the Subsidized Merchant.

So given a 14296 m^3 cube -- or 14500 m^3 cube to include a little waste space for gaps and such between containers -- how big is that? With a base footprint of 24m by 24m, a 1000 dTon stack is 24.8m tall; while a 14500m^3 stack is 25.17m tall. Given this is an eight containers wide by eight containers tall stack, the containers would be 3.1m tall (with 60 cm overhead clearance) for the 1000dTon stack, and 3.15m tall (with 20 cm extra overhead clearance) for the 14500m^3 stack.

If we are going to round a value down, we should avoid rounding down a value with has already been rounded down; that way layeth Von Neuman's catastrophe, and madness.
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An interesting thread which I seem to have spent far too much time thinking about :)

Whilst I like Geir's idea of the 5 and 10dT containers as they match the trade and spec lots, I prefer J.L. Brown's 4, 6 and 8dT for a couple of reasons.

The first is that they are close to the 20, 30 and 40 footers we have today.

The second is the mostly aesthetic. I like the idea of taking a 3x3x3 cube and doubling it's length to get a 4dT container, then doubling that length to get an 8dT. You can create "sticks" of containers clamped together which follow the same ratios (and also allow access to both ends of each container without having to break anything apart). For example a 4x2 stick of 6m containers follows the 1x1x2 ratios of the 6m container. (This is 32dT so with a bit of handwaving I'd say a modular cutter could move this stick instead of the standard 30dT cutter module). Making an 8x2 64dT stick follows the ratios of the 12m container (1x1x4).

Using 12m containers gives you a 32-box stick (8x4 256dT) or 64-box stick (16x4 512dT).

If you're OK with only being ale to access one end of each container then blocks of 2x2x2 could be use as the basis of the sticks, which then gets into serious tonnages being moved.

Once you're at that level it might be better to use larger 6x6x12m containers (32dT) and 6x6x24m (64dT) which could be built into similar sticks:
12m containers; 4x2 stick = 256dT. 8x2 stick = 512dT
24m containers; 8x4 stick = 2048dT. 16x4 stick = 4098dT

Basically I like the idea of sticks of containers following the same ratios as the containers themselves, and also being able to access each container when it's not aboard ship.
When I was toying with a container article I thought you'd see 2, 3 and 5 ton containers in tramps and for small scale shipments to in system colonies and stations and in tramp freighters like a free trader. They are small enough to hold cargo that you would expect these types of ships to specialize in.

10 ton would be a natural standard for large freighters hauling the bulk of the cargo for major routes. Why? It makes a lot of sense and standardization is the name of the game when it comes to containers.

I don't see large ships moving irregular containers since your process is built around storing like items. And your loading and unloading equipment is built for standard sizes. Things to consider are how you will move the containers once they get to a destination (but not their final one). You need your trucks (grav or wheeled) to be able to take standard sized loads as well.

Not to say you won't see different sizes, but like today you have 20 and 44ft as the standard for ocean going (up from 40) today. For road you see 40, 48 and 53 as the norm (but keep in mind your rail stacks are 40 and 48), with 24 as the standard for double (or triple bottoms, depending on state). Anything smaller has its own mechanisms or is loaded on a flatbed.

As far as looking sets of containers together.. that is an unknown I'd think. To make that work you would have to drastically increase materials and structural strength. Once you load them up (around 80k lbs today) you have to be careful about moving and load/unload them as if you make a mistake you rip/crush them. Even empties have a max height you ate supposed to stack before they collapse. And the goal is to make them strong enough to meet the requirements but also cheap enough. Generally you don't get both - even in the magic of the 52nd century. And merchants are always going to err on the side of cheap. Only governments and militaries will invest in excess, and only because they are generally not profit driven.
I am somewhat less optimistic about freight haulers settling on decimalization from end to end; factors of ten are great until you need to divide them by numbers of other than two or five. The example of current standards for cargo container sizes is illustrative -- two or three for sea-freight, three or four more for road-freight, and another two for rail-freight. Just agreeing on a consistent width and height is a win, because at least the containers can be stacked together; but I think there are going to be different sizes in use for exactly the same reasons we see different sizes in use today -- different carriers or regions will have different needs, capabilities, or preferences.

I am not super-stressed about the material strength of freight containers (or the joins between them), because gravitic technology is prevalent and widespread -- and when the entire volume of a container is rendered essentially zero-weight (or even slightly negative weight) then material strength is almost irrelevant. Even so, just TL 9 materials are going to be fantastically better than what we have today -- and 'Imperial Standard' is TL 12, with primitive-but-serviceable stuff being TL 10. Today we are stacking containers up to around nine containers high; my off hand eight-stack example seems a bit unambitious for a high TL container.
Yeah, the different sizes of containers were driven by profits, but also because of roads. You couldn't drive longer trailers till laws changed to allow them on the road. 20 and 40 ruled the seas for a long time, till they were allowed to get bigger.

Even with better materials it's still a question of cheap. And gravitics doesn't change load factors unless you make them stronger (the container). Not every world will have gravitics (many will still have wheeled trucks and trailers). And weight is still a factor for anything ground-based. Gravitics is great, but not cheap.

I wonder what a mi-jack using gravitics would cost? I'd think at least the cost of an air/faft, if not more since it has to lift a lot more mass.
i'm not worried about the fact that 10 is a silly number to use. i agree its silly, but the rules are based around 5 and 10 ton lots, so i'd rather make those work. yes i want efficiency, but i want efficiency that works with the game rules (same reason why we assume 3m x 3m x 1.5m, regardless of what makes more sense).
An all-steel sea-freight container is a wonder; steel was small-batch and of inconsistent quality from before the Roman republic until the early 1800's. A roll of sheet-steel of absolutely consistent steel is a staggering display of our technological prowess. Benjamin Franklin lived in an era where the aluminum in a single disposable can of drink would be a priceless treasure. To us, TL 9 & 10 materials will be amazing, wondrous, and expensive -- but they will be humdrum, every-day commodities in a TL 10 economy.

I am not sure I understand the claim that containers need to be stronger, and that gravitics 'does not change the load factor'. It seems to me that if a container is strong enough to support its' own mass (and the mass of its' contents, plus whatever extra external loads from stacking, etc) in the local native gravity field, then using gravitics to reduce local gravity on the container & contents is absolutely within all realistic safety margins.

As to the cost and availability of gravitics, this is something the current MgT2e heavily hand-waves -- but building a 4.5m^2 space of decking in a ship or space station is 50 kCr, but that reduces to 25 kCr if built without artificial gravity (and, by implication, inertial compensators). That leads to a cost per square meter of 5556 Cr, which never drops by TL although the capabilities do get better. Or maybe we could do this as a volume calculation, with 1852 Cr per m^3 being the cost. 'Central Supply Catalog Update 2023' page 11 gives us the rules for Retro-Tech -- generally, things get cheaper at TLs higher than when they are introduced. TL 9 'compensate for up to 1G' technology (which is an electronic device) is cheaper (926 Cr/m^3) at TL 10, TL 11 (463 Cr/m^3) and TL 12 (231.5 Cr/m^3) -- even if High Guard does not reflect that.
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Anyone else have thoughts on how much cargo a 12k ton freighter (J2) should have?
Also, what are tboughts on giving radiation shielding (or any other armour type) to generic freighters?
I've never bothered to build a large freighter or optimize one. But most existing large merchant ships have about 50% cargo at J2.

Ships have a certain amount of radiation shielding intrinsically. That's more than enough if they aren't flying into unusual radiation spikes or getting shot with military grade weapons. Would a hardened bridge and doubled rad protection be useful sometimes? Sure. Is it likely bean counters are going to pay Cr25k per ton for it? Not unless forced to.
I think first some caveats:

1) containers are going to be the top choice of moving cargo. Its efficient and allows for it to move from warehouse to warehouse before you have to crack the seals. So that's just like containers today (also allows them to be on truck and rail, or their 52nd century equivalent).

2) containers will be standard size. Large freight lines will most likely standardize on 5 and 10dton sized ones. They are well sized to move most items and are a good match as we've seen from terrestrial modern equivalents.

3) smaller freighters would handle the 5 ton ones, and maybe for smaller locations you'd get as small as 3 dton. That's reasonable sized to allow smaller ships to easily handle them.

4) space docks are going to have limited space to allow a ship to remove cargo if they need to get containers at the back. A good load master will load it in the order it would come off, but new cargo to be loaded can potentially fill up any spaces you just removed. So how to be able to access older cargo as you make your route (assuming you aren't point to point)?

5) stations will have limited surface space to allow for physical docks. So ship forms that are longer than they are wider, and load from the nose seem the best suited for space-only loads.

Right now the most efficient design I'm coming up with is a ship that stores containers in a rotary like mechanism, with the cargo in the outer rim and the center where crew, engineering and fuel are stored. Think of it like a ferris wheel, except cargo containers instead of people pods. Since traveller only counts internal hull displacement, the fact that you have a large circular portion with empty space in the middle, you don't lose any displacement volume to such a design - just what you have enclosed in the hull area.

1} I agree that containerization is going to be the top choice (for non-bulk cargoes) for big players in cargo handling. The 'do not need to break the seals outside a warehouse' aspect is pretty important; and it means that cargo-handling equipment can be designed to standardized specifications to handle containers, or groups of containers.

2} I agree that containers will be in a small number of standard sizes; and probably will only differ in one dimension to maximize compatibility. I tend to think 3m x 3m containers make sense; other folk might have different visions for their own TU.

3} Small ships will handle small containers, if they handle containers at all; more often the player-scale ships are picking up scraps (left behind by the big fish) that are not containerized for various reasons. A tramp free trader is more likely to pick up palletized or crated cargo.

4} A load-master will obviously try to arrange cargo aboard such that the cargo next to the loading/unloading hatch is tagged to be unloaded at the next port. Big cargo ships will be able to manipulate their own cargo inside their cargo bays -- but full bays leave no room for shuffling things around. The solution might be to load the cargo as cubes, where any cube can take the place of any other, and moving any cube creates a space for another cube to move into. Think of a 'Mystic Square' or '15 puzzle' style cargo arrangement. https://en.wikipedia.org/wiki/15_Puzzle Once all of the Cargo is properly arranged, the last vacant space (the 'Magic Cube') may be filled in with cargo going to the very next port.

5} High-ports will have limited volume for mucking about with cargo, so ships will be loading and unloading as close as practical to the warehouse -- sometimes directly into a warehouse. The ship will nose into the dock & immediately unload the block nearest the door; which will create enough space to manipulate the remaining cargo to reach whatever else needs to come out. Any 'partial' blocks will be combined as much as possible; sometimes empty containers can be used to complete a block if it only a little short; any cargo which does not make up a reasonable portion of a block will be left for spot-market carriers.

I am envisioning a mega-freighter with one to three stacks, of 2 or 3 (each quite long) parallel lines, of cubes. The cube next to the hatch is the 'magic cube' -- first unloaded (then cargo shuffled) and last (after cargo shuffling) loaded.
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Anyone else have thoughts on how much cargo a 12k ton freighter (J2) should have?
Also, what are tboughts on giving radiation shielding (or any other armour type) to generic freighters?
I have been playing with Arkathan's excellent 'Excel ship design sheet'; even with some sub-optimal choices I am about 7300 dTons. Here is a Google Sheets version: https://docs.google.com/spreadsheets/d/1yHTjsnvEOxp4FNVQbCw7QXYzYbOpSKQQC3j4YrZNWQg/edit?usp=sharing

This has enough fuel to jump 1 - 7 parsecs; any unused fuel space is used for cargo. About 55 dTons is 'tetris cargo', but the rest is (notionally, at least) is twenty nine 250 dTon cubes -- with ten dTon containers, this is a stack 5 wide & 5 tall. This is arranged as four rows of seven, with one extra cube in the back on the bottom, port side row -- opposite the end where the 'size five' cargo hatch (handles a 5x5 cube) is. There is no access or inspection space; but the back of the rear cube can be accessed in-flight with patience and athletic wriggling -- it is sometimes loaded backwards (with the doors of the containers facing the aft of the ship) if there are any crew-consumables carried. There are no ship's vehicles, but there is some space for a few middle passengers.
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Hi all,

I am coming to this conversation a bit late, but it has stimulated a lot of thought on my part. I started a separate thread on modules.

Thanks to several other great posters, I refined my idea which I think is relevant here.

The concept of self-loading container-containers. Allow me to explain.

You build a large jump-capable Cargo-Tender (like the Battle Tender). You put the jump drives and passenger staterooms in this "core." I designed a 4000-dTon version that can carry six 1000-dTon Cargo Riders.

You build a large sub-light only ship (I chose 1000 dTon). Equip it with the absolute MINIMUM needed to get to orbit. Build it a convenient shape without a lot of wasted space. I call it a Cargo-Rider. You fill that ship with cargo at the starport or wherever you like. This means you can do things like remove the entire roof and load it from the top if you want.

When the Cargo-Tender arrives, the six Cargo-Riders detach and fly down to the starport to be unloaded.

I designed fuel tanker versions of the Cargo-Rider. They can fly up to the tender and refuel it in orbit.

The fresh, full, out-bound Cargo-Rider can be waiting on the ground or even in orbit. As soon as the tender is refuelled and the tankers detach, the out-bound Cargo-Riders can attach to the Cargo-Tender. Cargo can be turned around in just a few hours.

The ship can carry up to 1128 x 5-dTon cargo containers in 1G / 1 atmosphere shirt sleeve comfort.

It could also carry up to 5700 dTons of bulk cargo (grain, ore, etc), or 5640 dTons of fuel (also with the capability to scoop and purify it during the 7 day jump).

This idea scales easily. The Hadrian Class Battle Rider is 50,000 dTons. It is theoretically possible to have similar sized Cargo-Riders.

You just need pairs of worlds that need that volume of cargo. Considering that here on Earth, there are dozens of container ships carrying 18,270 TEU.* That is the equivalent to 51,811 dTons of cargo. That is 9.2 times the volume of cargo in my proposed Cargo-Tender with six Cargo-Riders (carrying containers).

* TEU = Twenty Foot Equivalent Unit shipping container = 2.44m x 2.59m x 6.058m = 2.839 dTon (assuming 13.5m3 per dTon).

Looking at the volume of trade on Earth, imagine a high population world with ten times the Earth's population. You would need hundreds or thousands of ships like this per day.

Just a few thoughts.