It makes zero sense to build cargo or colonial module to be carried in commercial hangars, first of the commercial hangar is way bigger and very expensive for that purpose. You should use tugs to pull cargo or colony containers. But considering how cheap it is to build a yard with many slipways that can produce both cargo and colony ships it makes very little sense to do this. Both cargo and colony ships should practically never be idle anyway. Keeping some cargo containers around for your general tugs to pull around when you have some specific need can probably be smart, but as a general strategy it makes very little sense.

Using tugs to pull troop, supply, ordnance containers makes a bit more sense as you might not be using them all the time. The problem might be though that when you do need them you will need most if not all of them anyway so the gain might not be as high as you initially thought it would be. But still, using industry instead of a shipyard can sometimes be beneficial, especially when it is types that you will only build in limited numbers.

But using commercial carriers seem extremely inefficient versus using tugs due to the enormous overhead costs.

I only use commercial hangars as repair yards or for maintaining military ships with reloading facilities of box launchers, so they clearly fit well for fleet support vessels or pure repair yards. I quite often have specific fleet support vessels to work with escort flotillas. Fleet support ships to work with carriers for spare fighters and deploying small fast tankers for increased fighter striking ranges etc...

Industry are best utilised into building stations you are NOT building in huge quantities as yards usually can build things more efficiently, especially when you consider that yards can expand themselves once built. That is like a construction factory both producing something and building new factories at the same time. Or stations that are truly super large and building yards for them simply is not practical.

If your general support ships such as troop transports, ordnance and supply freighters are the same size and using the same general components then having one yard for them all is not a huge overhead cost either, the cost will be rather small to be honest. Sure you can use industry to build them in stations format and then use tugs to drag them around, it will be somewhat cheaper over time. It will cost you more officers though if that makes any difference to you, it actually might. But the amount of resources you save on this are so minor in comparison with everything else you build that I don't think it is worth the hassle of using tugs that way.

You still probably want to use dedicated fleet support vessels or assault ships as you want them with armour and CIWS and built for specific needs and with better more powerful engines than your more efficient general logistical support vessels.

Can you modularise weapons here and create ‘Q Ships’?

Haven’t tried yet, but assume you can put large military sensors on a cargo container and give that feature to a civilian freighter. . . ?

In a way yes, in a way no.  You can't make space stations military, so they will be "ships" for all considerations.  If they go over 1k they will need a bridge.  I'm away from Aurora atm, but this is a typical "missile pod" that I put into commercial hangers:

Missile Pod: 5,000 tons
Bridge, 2 Engineering Spaces, 50,000 liters of Fuel size 5 engine range 1 bn km

10 size 30 missile box launchers  (2 stage missiles total range 100 bn km, 5 Size 5 finals 25km/s with 9 str warheads)
MFC 110 bn km range)

Put 10 of those in a 100 kT "tender" with fuel, who drops and then bugs out.  They are small enough they rarely get targeted at range and BP is only 200-300 usually if they are lost.  Granted they have to return all the way to base or actual carrier to reload.  But those 500 missiles per tender which get added to the Alpha Strike means it is rare there is any return fire...

If it's docked with the mothership, then it can't do anything, and dropping an immobile weapons platform in the middle of a fight might not work out so well.

Though the idea of dropping out a 156.25Kt battlestation from a 500Kt megafreighter (size eyeballed off the assumption of 250Kt devoted to hangars) amuses me greatly. A certain video clip comes to mind. . .

Because many ships spend more time not performing the task they are designed to do and more time in transit. 

This is true.

Thus objectively being more efficient use of materials by having them be "paused" while "docked" in the container ship.

This, however, is rather not, at least for the only application we've been discussing in this thread. Each kiloton allocated to hangars on a container ship only gives you 625 tons of containers, which then incur further loss from the structure and crew requirements of the containers.

Let me give you a real world example. All my light transport ships are built on the same frame. They all displace 100Kt, go at 1000km/s with my current tech, and aim for roughly the same range.

Chungking-C Colony Ship: 77.5Kt of Cryogenic Transport for 310K meat popsicles.
Ghent-B Troop Transport: 75Kt of Troop Transport Bay for 75K in troops carried.
Aberdeen-D Freighter: 75K of Cargo Hold for 75K cargo capacity.

Wenchow Container Ship: 72Kt of Commercial Hangar deck for 45K capacity for containers.
  Containers are built as close to 5k as possible.
 Cryo loadout: 43.2Kt (9x4.8Kt) of Cryogenic Transport for 172.8K meat popsicles. 55.7% of the dedicated ship.
 Troop loadout: 43.2Kt (9x4.8Kt) of Troop Transport bay for 43.2K of troops. 57.6% of the dedicated ship.
 Cargo loadout: 40.5Kt (9x4.5Kt) of Cargo Hold for  40.5Kt cargo carried. 54% of the dedicated ship.
In each case, the dedicated ship is much better at doing the one job it can do than the modular conveyor.  (The fact that there's no hold smaller than 500t hurts the cargo variant quite a bit.)

And as far as minerals go, in tons of TN mineral per:
Wenchow, hull: 6596.9
  Cryo Container: 316.3
  Barracks Container: 137.3
  Cargo Container: 38.7

Chungking-C: 4391.9
Ghent-B: 3036.9
Aberdeen-D: 1606.9

Wenchow + 9x Cryo Container: 9443.6
  Wenchow + 9x Barracks Container: 7832.6
  Wenchow + 9x Cargo Container: 6945.2
  Wenchow + 9x each: 11027.6

A single Wenchow with the option to carry any of the three loadouts costs you 122% as much minerals as buying one of each dedicated ship.

So, let's look at those numbers a few different ways:
Wenchow Cryo vs Chungking-C:
  2.15x cost per hull.
  3.86x cost per colonist carried.

Wenchow Barracks vs Ghent-B:
  2.28x cost per hull.
  3.96x cost per ton of troops.

Wenchow Cargo vs Aberdeen-D:
  4.3x cost per hull.
  7.9x cost per ton of cargo.

Wenchow + all container loadouts vs Chunking-C+Ghent-B+Aberdeen-D:
 1.22x cost of buying all three dedicated ships.
 

For ship types that are going to be running all the time, like your colonial transports, using Modular Conveyors is very clearly not worth it. For pure cargo hauling, even if it's going to sit idle a decent portion of the time, you're still probably better off building dedicated ships. But covering your needs for troopships/supply ships/colliers, there's clearly a place for Modular Conveyors, as you can meet your peak demand for those types of ship without having to keep a bunch of idle hulls around, or dedicate multiple shipyards to their production.

Purpose built ships give you efficiency. Modular ships give you flexibility. There's room for both in your merchant marine.

1k ton is the traditional size for containers in AuroraVB due to not needing a bridge.

This strikes me as very much a false economy, at least now under C#. (I dunno what particular ship design quirks under VB6 made it make sense to do that.)

The bigger you build your containers, the less efficiency you lose, though you're giving up flexibility. Building out a single container that fills the Modular Conveyor is the most efficient thing you can do, if you a) don't need to ever carry split loads and b) Don't need to ever use ships of a smaller hangar size as container ships.

A 45K Heavy Cargo container, for example, can dedicate 99.17% of it's displacement to cargo holds, compared to 97.15% for the 5K version. It's not going to shift the efficiency numbers in favor of modular over dedicated, but it's something to consider. You also, and I didn't even think about this until now, save a lot on mineral cost for the containers. Again, not enough to make a big dent in the mineral cost per ton of cargo carried, but it's a thing to think about.

Because many ships spend more time not performing the task they are designed to do and more time in transit.  Thus objectively being more efficient use of materials by having them be "paused" while "docked" in the container ship.

Quote from: Pedroig on May 10, 2020, 10:54:11 PM

Except it takes 1/10th the time and cost to build commercial versus military.

That's irrelevant to a comparison between a commercial container ship and a commercial ship that dedicates the same space directly to whatever it's designed to haul, so I'm not sure what you're trying to say here.

Except a commercial container ship can "contain" military components without becoming military, a commercial ship cannot.

How do you load/unload these? Can you just give a load/unload command and it uses the docked capacity or do you have to launch the container for loading and (more importantly) then dock them again?

Except it takes 1/10th the time and cost to build commercial versus military.