Tug Concept

[sageryne]

Hi all,

I am working on a project and I came up with an idea for a tug/boarding 20-dTon launch. I think that tugs are a very useful and practical type of sub-craft that we don't typically see in Traveller games.

My concept is that the launch has engines far out of proportion to its size. To move a 100-dTon ship at 1G costs = 1% or 1-dTon. If you placed a 1-dTon manoeuvre drive on a 20-dTon launch it would go 5Gs (since 1-dTon engine = 5% of 20-dTons = 5G drive). The next thought I had was what if you put more than one of those engines on the launch?

The maximum gravitic manoeuvre drive at TL15 is 9G, so it is clear to me that you can't "stack" gravitic drives (i.e. a 20-dTon tug with 4-dTons of manoeuvre drive cannot go 20Gs). However, it seemed to me that 4 x 1-dTon drives could have a greater cumulative pushing power.

I have attached my design as a screen-shot.

It is expensive, but based on my logic above:

1. The tug alone could go 5Gs (quick response time to get to a ship in need of help).

2. The tug could push a 100-dTon ship at 3.33G (4-dTons of manoeuvre drive moving 100+20 = 120-dTons)

3. The tug could push a 400-dTon ship at 0.95G (4-dTons of manoeuvre drive moving 400+20 = 420-dTons)

4. The tug could push a 1000-dTon ship at 0.39G (4-dTons of manoeuvre drive moving 1000+20 = 1020-dTons)

My concept uses a forced linkage apparatus to connect to the ship. I visualized this as a large "pusher plate" that had an electromagnet in it for connecting with metallic hulls. It would also have grapples for connecting to non-metallic hulls and a tow cable.

I do envision these tugs as working in pairs (or more), like you see assisting ocean going vessels.

Thoughts?

- Kerry

 

[Spinward Flow]

I am working on a project and I came up with an idea for a tug/boarding 20-dTon launch. I think that tugs are a very useful and practical type of sub-craft that we don't typically see in Traveller games.

Tugs ARE very useful.
Unfortunately, CT didn't "implement" any rules for them all that well (beyond the Jump Tender concept).

The attachments that you've provided indicate that you are not working in a Classic Traveller (CT) context, but rather using one of the later editions. Could you please clarify which edition you wish to be theorycrafting in?

I say this because (CT) LBB5.80 requires a minimum of 2% of hull tonnage to achieve 1G using custom drives, which as you'll note is not the same as your 1% postulate in your OP (hence my desire for clarification).



Another point is that I'm of the opinion that if other craft "cost additional tonnage" for internal stowage, they should ALSO cost that additional tonnage when externally towed (to keep things "fair" and even between the two options).

Under CT, big craft are carried @ 110% of their "actual" tonnage ... so a 100 ton starship requires 110 tons of volume to be carried internally (and I would argue, also when towed externally). Therefore, you may want to re-examine your assumptions behind the following:

2. The tug could push a 100-dTon ship at 3.33G (4-dTons of manoeuvre drive moving 100+20 = 120-dTons)
3. The tug could push a 400-dTon ship at 0.95G (4-dTons of manoeuvre drive moving 400+20 = 420-dTons)
4. The tug could push a 1000-dTon ship at 0.39G (4-dTons of manoeuvre drive moving 1000+20 = 1020-dTons)

100*1.1+20 = 130 dTons
400*1.1+20 = 460 dTons
1000*1.1+20 = 1120 dTons

I'm NOT "well familiarized" with editions of Traveller after CT, so this may be a mooted point by how the edition of Traveller you're working with handles this point of design accounting.

 

[sageryne]

Hi Spinward Flow,

I am designed this ship using Mongoose High Guard 2022 Update.

I am not sure if I follow your logic for "cost additional tonnage." I assume with internal stowage this extra tonnage is to account for manoeuvre space around the sub-craft, connections, hatches etc. In the case of a tug, it is just pushing against the target vessel (with an electromagnet or grapples giving it purchase). There is no long term connection.

Like a real world tug, I see this vessel as being used to help guide larger vessels into place (docking ports and the like), or helping vessels that have lost power.

- Kerry

 

[McPerth]

ITTR there was one such design in a Challenge issue (I cannot now give you th exact number)...

It was for MT, but its concept could be used, even if numbers must be redone.

 

[sageryne]

Yes, that was the Hercules Space Tug from Challenge Issue 40, page 31-32.

It was a big ship, with a mass of 6700 tons (I am not sure what the displacement would be, stats aren't provided). It does say it could recover ships up to 50,000 tons and its maneuver was rated to 200,000 tons.

 

[Spinward Flow]

I am designed this ship using Mongoose High Guard 2022 Update.

Okay, I definitely do NOT own that, nor do I have access to it, so my concerns are probably invalidated by that fact.
Different edition, different rules, different paradigm for "how stuff works" (and all that jazz).
Similarities will remain, but important differences will overwhelm the legacy concerns of previous editions.

I am not sure if I follow your logic for "cost additional tonnage." I assume with internal stowage this extra tonnage is to account for manoeuvre space around the sub-craft, connections, hatches etc.

Kind of ... but it's not just that.

This will be easier if I provide you a snippet from (CT) LBB5.80, p32 relevant to why I brought that up.

Where you see the word "mass" just go ahead and substitute in dTons (this was later included in official CT errata).

My understanding is that Mongoose High Guard "sustains" this interpretation (broadly speaking), but with some different nuances available as options.

Point being that you can't put a 100 ton starship into a 100 ton cargo bay, you need a 110 ton cargo bay (or hangar) for the internal stowage of a 100 ton starship (or boat).

If you don't have such a rule, you can do things that are quite obviously silly ... such as having a 100 ton cargo box ... that you can stuff other (identical) 100 ton cargo boxes into (indefinitely), because a 100 ton cargo box can be filled up with a box that is itself 100 tons. So without any kind of "packing losses" going on, you could transport 10,000x 100 ton cargo boxes (total tonnage: 1 million tons) stacked nested inside a single 100 ton cargo box.

So to prevent that, there are "packing losses" going on (the 130% for small craft and 110% for big craft) when needing to put craft INTO other craft. Small craft don't suffer "packing losses" on parent craft 1000 tons or less, but big craft incur "packing losses" on ALL parent craft, regardless of parent craft tonnage.

Basically, internal hangar bays "can't be shrink wrapped" around big craft (100+ tons), was the precedent set by LBB5.80.

I take a "Sauce for the goose..." approach to the question of internal stowing vs external towing, to prevent any sort of bias in favor of one vs the other.

In the case of a tug, it is just pushing against the target vessel (with an electromagnet or grapples giving it purchase). There is no long term connection.

Even if there is no long term connection, there's going to be certain ... inefficiencies ... involved with applying (properly controlled) thrust to a temporary partner craft that you've externally docked with to provide tug services. The simplest way to represent that "needing to reserve extra maneuvering power to maintain control" is to (in effect) make the docking partner "bigger than they normally are" so as to account for the necessary maneuver control margin.

In a zero-G/free fall/orbital mechanics context, all of your thrust vector needs to pass through the center of mass. If your thrust vector doesn't pass through the center of mass, a portion of the thrust vector is going to cause pitch/yaw/roll moments that will just keep accelerating and getting bigger (until some sort of structural failure/breakdown occurs, not recommended). Therefore, when you're "towing" via external docking another craft (or even just a big net full of rocks!), you want to assume that you need more MARGIN available to you as the tug craft in order to sustain control of whatever maneuvers you are making. The way to represent that margin (so as to avoid errors that make a mess of things) is to "overestimate" the dTonnage of whatever you need to be towing.

Hence ... why computing as if big craft are 110% of their actual dTonnage while being towed externally makes a lot of sense, even if the other craft isn't "actually" that size/displacement.

400*1.1+20 = 460

Even if you're "only" moving around 400+20=420 tons of combined craft, for safety margin reasons it's better to compute things as if you need 460 tons of maneuvering "power" in order to safely control the acceleration vectors applied to your (docked) combined craft.



Hope that makes sense.

 

[sageryne]

Different systems aside, I can accept your argument that you need the additional reserve for manoeuvring.

However, in general, I don't think that makes much of a difference, because most of the time, tugs do not want to build up significant velocities in the ships they are moving (except perhaps if they are towing them a long distance). In shipyards and starports (high or low), I expect the speeds will be measured in tenths or hundredths of a G.

A little 20-dTon tug nudging a 50,000-dTon mega-freighter into a berth will only be able to generate 0.0073G. Still, given the huge amount of mass of such a displacement ship, you wouldn't want it going any faster than that.

- Kerry

 

[Spinward Flow]

However, in general, I don't think that makes much of a difference, because most of the time, tugs do not want to build up significant velocities in the ships they are moving (except perhaps if they are towing them a long distance). In shipyards and starports (high or low), I expect the speeds will be measured in tenths or hundredths of a G.

Then it depends on the use case application.

If you're looking for what amounts to a "harbor tug" that is only working at "extremely short ranges" to provide "harbor services" in and around the starport ... that's one thing.

If you're looking for what amounts to a "barge+tug" that is meant to undertake long hauls (think up/down the Mississippi River type stuff, which in this case would be interplanetary transfer orbits) then you're aiming for a very different use case and application.

Suffice it to say that if you're wanting to do "micro-G" accelerations at "within Mk 1 Eyeball visual range" of docking berths in and around a starport, that's going to look almost nothing like an interplanetary or interstellar "tug" type of craft.

 

[sageryne]

Then it depends on the use case application.

If you're looking for what amounts to a "harbor tug" that is only working at "extremely short ranges" to provide "harbor services" in and around the starport ... that's one thing.

If you're looking for what amounts to a "barge+tug" that is meant to undertake long hauls (think up/down the Mississippi River type stuff, which in this case would be interplanetary transfer orbits) then you're aiming for a very different use case and application.

Suffice it to say that if you're wanting to do "micro-G" accelerations at "within Mk 1 Eyeball visual range" of docking berths in and around a starport, that's going to look almost nothing like an interplanetary or interstellar "tug" type of craft.

Agreed.

Tugs are a broad classification of boats/ships, not one single type.

For the project I am working on, the "mothership" is a 1000-dTon salvage ship with 6G engines and a tow cable. In most cases, it will be doing the towing and these little 20-dTon tugs will just be guiding and providing some braking.

I could see a whole family of tugs: harbour tugs, barge tugs, salvage tugs, etc. They could range from tiny to huge in tonnage and push/pull capability depending on their use-case.

Then, there are the case of what I would call "jump tugs." These would be very specialised vessels designed to go out and bring back ship's whose jump drives had failed. I think there would be a cost-benefit analysis to do here. How often does this happen? How often would a jump tug be used. I am not sure what would be practical here, as you would have to bring the stricken vessel inside your jump field, so you might be limited to recovering smaller vessels. This would certainly be a rare and specialised vessel.

For recovering larger vessels, you might need some sort of travelling shipyard/dry dock which could go to the stricken vessel carrying the necessary replacement parts and repair the ship where it is (at least repairing it to the point where it could jump back to a proper shipyard).

All these "support vessels" are incredibly important, as it is usually cheaper to repair a damaged vessel than build a new one (as long as it isn't too badly damaged). Even with the badly damaged vessels, there would still likely be salvage vessels that could strip the ship of everything that could be reused leaving behind only the most damaged scrap. Even then, there would probably be scrappers that would pick up those leftover bits to melt down and reuse.

- Kerry

 

[whartung]

Also, you don't need large motors to be useful as a tug. .1 G of acceleration is a LOT. We're just spoiled by having free, high G power.

Tugs would operate in groups as well, you'd have several of them nudging the ships.

Finally, there needs to be a mechanic for towing. Tugs are great for pushing, but it's much safer to tow over long distances. I'd have to assume their's mounting eyes or hooks to which cables can be attached.

The real trick there is you'd have one (or more) tugs towing the ship, but then, toward the end, they'd have to either turn around to stop the ship, or have other tugs coming in for the decelerating phase. I don't see a hard connection being practical for a large ship. So, it will take some coordination. Tug pilots should be at least Pilot-2 I would think due to all the tricky maneuvers.

 

[Spinward Flow]

Tugs are a broad classification of boats/ships, not one single type.

For the project I am working on, the "mothership" is a 1000-dTon salvage ship with 6G engines and a tow cable. In most cases, it will be doing the towing and these little 20-dTon tugs will just be guiding and providing some braking.

I'm doing something similar with my own design research project, but I'm doing it in the context of CT (LBB2.81, LBB5.80 and of course, LBB A5 and CT Beltstrike as my foundations). Additionally, I'm doing it as an exercise in a modular container commercial merchant starship application. That means external towing under both maneuver and jump drive applications.

I'm currently trying to "square the circle" on a set of design parameters that can have "backwards compatibility" to J2+2 "long trader" in a TL=9 standard drives (LBB2) formulation, but which can be "evolved" upwards into a J3+2 "clipper" version by TL=10.

Needless to say, there are a LOT of moving parts (starting with settling on a scaling for the modular containers the whole concept is built around). I keep going back and forth between 16 ton, 20 ton, 24 ton and 30 ton boxes (configuration: 4, close structure) for the modular containers themselves.

The whole thing is a starship+small craft setup, where the small craft is basically a fighter (so the starship can be unarmed but screened by the small craft) and the small craft serves double duty as a logistics marshaling/sky crane lifter for the modular container boxes both on world surfaces and in orbit. That way, the modular containers can be moved outside/inside the hull of the starship, which then allows the starship (with its internal hangar bay) to operate as an orbital shuttle for moving modular container boxes between world surface (under atmosphere) and orbit.

Current designs are weighing in around TL=9 D/D/D drives @ ~280 tons ... leaving 120 tons of external load capacity remaining while retaining J2/2G drive performance. The TL=10 "clipper" version is going to have either E/E/E drives or F/F/F drives and be somewhere close in tonnage with J3/3G drive performance. Maximum combined tonnage (@ J1/1G drive performance) would therefore either be 800 ton (D/D/D) or 1000 tons (E/E/E or F/F/F). I'm still analyzing alternatives and trying to make something that "works" as broadly as possible for the widest range of potential applications (including, of course, Adventure Class Starship potential).

One side effect of doing things that way is that I need the starship and the small craft to be able to operate independently of each other, which means I need 2 pilots (for starters) ... unlike how things are done with the Subsidized Merchant and its 20 ton Launch (where you've only got 1 pilot for 2 craft on the crew roster).

I could see a whole family of tugs: harbour tugs, barge tugs, salvage tugs, etc.

The thing is ... if you're talking about space operations, there aren't that many varieties needed. Your main variables are going to be:

• Operational range/endurance
• External load capacity
• Drive performance (unencumbered and under maximum external load)

"Harbor" tugs are going to be SHORT range affairs, the equivalent to a shunting yard locomotive. I would even argue that such craft ought to be remotely operated "robotic" drone craft (no life support onboard needed) with an operator sitting in an office space somewhere in the starport (probably controlling multiple tug drones simultaneously with extensive computer assistance?).

Barge tugs are where you get into the longer range/endurance options ... starting with interplanetary and reaching up into the interstellar. There's plenty of precedent for interstellar tugs (usually called Jump Tenders) and are the reason why Battle Riders are even an option for naval forces. The thing is, barge tugs "need barges" to move ... so there's going to be a design pressure on "standardizing" the barges (or modular containers, if you like) that the barge tug is meant to be mobilizing. So ideally speaking, you want to start with defining the (unpowered) barges and then get into working up what the tugs that will be moving those barges looks like.

Salvage tugs, along with search & rescue, aren't really going to be highly specialized "unique" designs built from the docking ports on inwards for a specific purpose. Instead they're going to be "lightly modified" variants of existing craft. If you've got a craft with an external load capacity (and thus, capable of towing external loads), you've got the makings of a salvage/search & rescue tug. Kind of like how (surplus) Type-S Scout/Couriers can be modified into Type-J Seekers for the role of prospector. One big difference between the salvage mission and the search & rescue mission is going to be ... TIME. With a salvage situation, you're looking at an already dead hulk with (presumably) no survivors onboard, so there's no real "rush" (aside from getting paid!) to complete operations. With search & rescue, time is the enemy ... the longer it takes to reach a distress call, the worse the chances of survival get, so higher (unencumbered) drive performance for quicker response times are preferred.

Then, there are the case of what I would call "jump tugs." These would be very specialised vessels designed to go out and bring back ship's whose jump drives had failed. I think there would be a cost-benefit analysis to do here. How often does this happen? How often would a jump tug be used. I am not sure what would be practical here, as you would have to bring the stricken vessel inside your jump field, so you might be limited to recovering smaller vessels. This would certainly be a rare and specialised vessel.

If you're thinking in terms of pure salvage, then yes ... rare occurrence.
If you're thinking in terms of modularized container transport starship which normally is hauling cargoes around, but which in a pinch can be used as an interstellar tug for salvage opportunities ... perhaps not rare at all.

Kind of like how a lot of ground vehicles have tow hitches, even if they aren't always being used.

For recovering larger vessels, you might need some sort of travelling shipyard/dry dock which could go to the stricken vessel carrying the necessary replacement parts and repair the ship where it is (at least repairing it to the point where it could jump back to a proper shipyard).

Depends on how BIG of a "larger vessel" you're talking about.
Battleships (200k+ tons) are basically going to need a Jump Tender (basically a tug) to mobilize them back to a shipyard for repairs.

 

[sageryne]

Hi Spinward Flow,

It sounds like you and I have a lot of thoughts in common!

One of the ships I designed for my own campaign is essentially the cargo version of the jump tender. Mine is big. The "mothership" is 12,000-dTon ship with the capability of jump-2 for 40,000-dTons. It carries fourteen 2000-dTon cargo "riders." Each of them is a simple cube with the ABSOLUTE minimum of equipment necessary to move at 1G. Of the 2000-dTons, 1800 is cargo, and just 200 is equipment (manoeuvre drive, power plant, fuel, bridge, computer, fuel bladder, fuel scoop, fuel processor and three double cabins). The cargo is in the form of 450 x 4-dTon cargo containers. The idea is that some of the cargo riders goes down to the starport and get unloaded/loaded with cargo. Other cargo riders go to the gas giant or ocean and fill with unrefined fuel. The bladder converts the empty cargo bay into a fuel tank. The fuel is refined at a slow pace.

The mothership jumps to the planet's 100 diameter limit. There, the cargo riders going to the planet detach. "Tanker" cargo riders attach and refuel the mothership, then detach again, and any outgoing cargo riders attach. Everything comes to the mothership. When it is refuelled and the cargo riders are attached it jumps out.

The cargo riders are simple sub-light-only cubes, not that expensive. The main capital cost is in the mothership. All the logistics are done with the cargo riders. The mothership rarely stops moving for more than a day.

Of course, this only works on very high volume routes with a lot of trade.

I am doing these designs in Mongoose High Guard 2022 Update, so I am not sure if it is all that useful to you in CT, but I am happy to share my designs if you are interested.

- Kerry

 

[Spinward Flow]

Of the 2000-dTons, 1800 is cargo, and just 200 is equipment (manoeuvre drive, power plant, fuel, bridge, computer, fuel bladder, fuel scoop, fuel processor and three double cabins).

Whut.

Um ... yeah.
You're definitely not working with CT.

I am not sure if it is all that useful to you in CT

I'm guessing it's not.
I'm working in a different design paradigm and my mission use case isn't overlapping nearly enough for cross-pollination to work properly.

The foundational concept notions are similar, but you're talking "big stuff" that's really Large Crew/Big Corporate type of things. I'm looking at more of the penny ante Free Trader/Tramp Merchant low end commercial speculator end of things (1000 combined tons and under), which is a VERY different market segment. So the scaling is radically different between us, which makes a huge difference.

For one thing, I'm working in the TL=9-10 realm.
Sounds like you're probably working in the TL=12+ realm, which will also make a huge difference.

 

[sageryne]

Whut.

Um ... yeah.
You're definitely not working with CT.

I'm guessing it's not.
I'm working in a different design paradigm and my mission use case isn't overlapping nearly enough for cross-pollination to work properly.

The foundational concept notions are similar, but you're talking "big stuff" that's really Large Crew/Big Corporate type of things. I'm looking at more of the penny ante Free Trader/Tramp Merchant low end commercial speculator end of things (1000 combined tons and under), which is a VERY different market segment. So the scaling is radically different between us, which makes a huge difference.

For one thing, I'm working in the TL=9-10 realm.
Sounds like you're probably working in the TL=12+ realm, which will also make a huge difference.

Unfortunate, but understandable.

Yes, I have designed this as big corporate commercial ship, on the real world container ship scale of things. Shockingly, although my ship is 6,300 TEU (twenty-foot-equivalent-units), in the real world, there are ultra-large container vessels with a capacity of 18,000 TEUs. Maersk has 31 of these monsters and they are just one shipping company.

Triple E-class container ship - Wikipedia

en.wikipedia.org

COSCO has six of the even bigger Universal class container ships capable of carrying 21,237 TEU.

https://en.wikipedia.org/wiki/Universe-class_container_ship

My concept is built on these large vessels moving from hub world to hub world. Once at the hubs, the goods would be broken down into smaller lots and distributed by the free/tramp freighters.

I am also working at TL-14 (huge corporate vessels built in the best shipyards).

Classic Traveller ship design and Mongoose High Guard have diverged for sure.

Still, I am glad to hear you are working on that sort of a project.

- Kerry

 

[Spinward Flow]

I am also working at TL-14 (huge corporate vessels built in the best shipyards).

Not sure of which location (sector) you plan to be working in, but if it's somewhere on Travellermap, you can use the search function to locate all the type A starports in a sector at various TLs.

For example, the Spinward Marches can be searched using the following (copy/paste to see for yourself):

• in:spinward uwp:a??????-9
  • 1 starport
• in:spinward uwp:a??????-A
  • 8 starports
• in:spinward uwp:a??????-B
  • 15 starports
• in:spinward uwp:a??????-C
  • 13 starports
• in:spinward uwp:a??????-D
  • 8 starports
• in:spinward uwp:a??????-E
  • 2 starports
• in:spinward uwp:a??????-F
  • 4 starports

These are all of the locations capable of constructing starships (type A starport) at TL=9-F.
There will be additional location capable of offering annual overhaul maintenance (type A-B starports) but they won't be capable of constructing starships.

My point being that @ TL=14, a sector like the Spinward Marches will only have 2+4=6 starports capable of constructing TL=14 starships.
By contrast, if you need to construct a TL=10 starship, there are 8+15+13+8+2+4=50 starports capable of constructing TL=10 starships.

Now, if you're working in the megacorp segment of the market, those kinds of "logistical limitations" might not be all that limiting (since your megacorp will OWN the shipyards where construction and maintenance work will get done) ... but if those shipyard locations are "inconveniently located" on the map (all on one side or clustered in a corner) then that's going to have impacts on how far your "big boys can go" each year before needing to turn around and head back to their home port in time for tea in time for their annual overhaul maintenance.

A sideline consideration is that if you've got "the bestest high tech" and your nifty starship suffers some sort of breakdown (mishap, pirate attack, blind/dumb bad luck, whatever) far away from any "necessary tech" support infrastructure, you could put your "big beautiful starship" into a parking orbit for a VERY LONG TIME before a communication can be sent back to a supply hub to order a replacement part that will then need to be shipped out to enable repairs (one of those, "we don't make stuff like that 'round these parts" kinds of situations). Can you say, "interstellar supply chain disruption" ...?

REALLY high tech makes things work "so much nicer" on the design spreadsheet at the naval architect's office, but REALLY high tech stuff can wind up being a liability in actual operation out in the field, due to logistical tail issues thanks to where stuff is on the sector map. In a lot of cases, it can actually wind up being more economical to design starships to a lower tech level standard that "gets the job done" in order to have a wider industrial supply base that can support the technologies needed for the class.

 

[spank]

I just saw something like this a couple days ago,
I just cant' remember where.
I can even picture the illustration.
It's going to drive me nuts.

 

[sageryne]

Hi Spinward Flow,

My campaign is set along the Third Imperium / Solomani Confederation border. There are a fair number of TL-14 worlds in the Confederation.

One of the changes I have made for my own campaign is that I have renamed Transstar (the Solomani megacorporation owned by the Solomani Party) to FedEx.

It is mainly because of these pictures. Someone scratch built a model of a huge container spaceship. Once I saw it, I totally locked in to the idea of FedEx still existing in the 57th century and them being the dominant shipping company of the Solomani Confederation.

- Kerry

 

[spank]

Reminds me of the "Flying Brick" concept I'm working on.
Modular 100 Dton units that can be stacked to make a ship.
Not nearly as polished as what you've got.

 

[spank]

Interestingly a shipping container comes closes to being Traveller standard.
A 20 footer is 6.058 meters, which is just slightly overlength for 4 dTons,

The Length/Width are a little under the 3.0 Meters that would fill a dTon.

Unfortunate, but understandable.

Yes, I have designed this as big corporate commercial ship, on the real world container ship scale of things. Shockingly, although my ship is 6,300 TEU (twenty-foot-equivalent-units), in the real world, there are ultra-large container vessels with a capacity of 18,000 TEUs. Maersk has 31 of these monsters and they are just one shipping company.

Triple E-class container ship - Wikipedia

en.wikipedia.org

COSCO has six of the even bigger Universal class container ships capable of carrying 21,237 TEU.

https://en.wikipedia.org/wiki/Universe-class_container_ship

My concept is built on these large vessels moving from hub world to hub world. Once at the hubs, the goods would be broken down into smaller lots and distributed by the free/tramp freighters.

I am also working at TL-14 (huge corporate vessels built in the best shipyards).

Classic Traveller ship design and Mongoose High Guard have diverged for sure.

Still, I am glad to hear you are working on that sort of a project.

- Kerry

 

[Spinward Flow]

I have renamed Transstar (the Solomani megacorporation owned by the Solomani Party to FedEx.

I still prefer the name ... FedUps.
There was a merger at some point before the Interstellar Wars with the Ziru Sirka 'n' stuff ...

It is mainly because of these pictures.

That's some very nice 3D printing you've got going on there.
It's also a completely practical planform ... doing everything as "boxes" that get pushed along by the tug/tender at the rear.

Another (obvious) form factor styling for a tug+barge(s)=freighter type of form factor would be what was seen in Babylon 5, where there's a "central spine" rail with the drives and controls in it and have standard cargo boxes running along each side.

A 20 footer is 6.058 meters, which is just slightly overlength for 4 dTons

Yeah, but if I can't fit a single occupancy stateroom (4 tons) or an air/raft (4 tons) into one, what good is it?
Although I'm pretty sure you can fit a model/2fib (4 tons) into one ... if you HAD TO ...

To be fair, the TEU is a modular container intended for road/rail/ship multi-modal transport at the bottom of a 1G gravity well ... so ... y'know ... different priorities than bulk transport to the stars, I guess.