The Incongruity of Shipbuilding Time

[skoormit (OP)]

As you know, the class design window shows the build time of a class, which is how long it will take a shipyard to build one such ship (before any governor/sector shipbuilding bonuses).
As you also know, the build rate (in BP/year) is based on the size of the ship. Larger ships are built at a faster rate; expensive ships take longer than cheaper ships of the same size.

Notably, the build rate does not depend on the size of the yard. Building a small ship in a huge yard does not get the job done any faster than building it in a small yard.
Which makes sense. A shipyard of the required size has the workspace necessary to build the ship as quickly as physically possible. You can't build it any faster by putting more workspace around it--the amount of work that can be done at one time is limited by the volume and the surface area of the ship.

So, come, let me show you something interesting.

I have a basic large freighter design, the HaulerXL: a large cargo hold, 3 shuttle bays,  21 engines (size 100), 1 Very Large Fuel Storage, 15t of scanners, and the required other stuff (armor, bridge, cq, eng spaces).

HaulerXL:
Size: 235,740 t
Cost: 1,786.5 BP
Build Time (yrs): 0.5
Implied rate: 3573 BP/yr

Suppose I split this design into two pieces: a tractor and a trailer.
The trailer has the cargo hold and the shuttle bays. The tractor has everything else. Both have the required other stuff (armor, bridge, cq, eng spaces).

Trailer:
Size: 128,095 t
Cost: 532.4 BP
Build Time (yrs): 0.26
Implied rate: ~2048 BP/yr

It takes less time to build the trailer than the complete ship.
This is fine. Most of the cost is from the large, cheap cargo hold. Even though the build rate is lower, it gets done pretty fast.
It is consistent with the mechanics, and makes sense.

Tractor:
Size: 108,316 t
Cost: 1376 BP
Build Time (yrs): 0.77
Implied rate: ~1787 BP/yr

This guy is smaller than the trailer, so the build rate is lower. This is consistent with the mechanics.
It also takes much longer to build than the trailer. Okay, fine. It is not mostly empty space, as is the trailer. Small and expensive components take time to build. No problem.

But it also takes longer to build the Tractor than it takes to build the complete HaulerXL.
This...just does not compute. I can't wrap my head around an explanation.
How can it take less time to build a HaulerXL than it does to build a ship that is entirely a subset of the HaulerXL?
And remember, the size of the yard doesn't matter. A yard large enough to build the HaulerXL, which takes 0.5 years, will need 0.82 years to build a Tractor.

I'm not saying this needs to change. Just because I can't wrap my head around the implications of a given mechanic, does not mean the mechanic is broken.
Maybe game balance issues compel this logical oddity. Or maybe Steve will look at this example and decide to tweak the mechanics. I don't know, and I'm not arguing for one or the other; I defer to Steve's vision, experience, and preference.

But can anyone put my mind at ease and reconcile this apparent incongruity with a logical explanation?

[Zincat]

This looks indeed to be a quirk of the shipyard construction rate mechanics. And I do believe it needs some sort of addressing.
Maybe there actually is some sort of logical explanation, but I will admit my ignorance of the precise internal calculations of how shipyard works. So if there is one, I'm afraid I don't know it.
But I can give you a quasi-scientific explanation! Sort of! More roleplay than anything else 

If you divide components between high complexity (engines etc) and low complexity (hangars etc) ones, the tractor has the most "density" of high complexity ones.

- The trailer is mostly hangars. All low complexity stuff. It's an "easy" ship to build, all things considered. Just put the parts together, no need for anything else.
- The entire hauler is half and half, space wise. You can imagine that there are not many hard constraints on how it is built. Engines can be spaced, it's probably not that hard to assemble.
- The tractor instead is a very "dense" ships. It's full of complex components all crammed together one next to each other. There's not much space for anything else, heat exhausts and the like have to be placed very carefully because you have so many delicate components in a small space. So, it's a lot harder to assemble correctly without design problems, and thus takes longer to build.

I know I wrote it just for fun, but it actually makes SOME sense at least  The mechanic probably need addressing yes... but hey, I gave you sort of a reason for it 

EDIT: by the way, the shipyard probably does work in a way similar to this. I assume that the time required is a function of build cost and volume, some sort of ratio. So if you add parts that have large volume but low cost, the building time gets lower, because the ratio between build cost and volume changes.

[Jorgen_CAB]

The simplest way to view this is that it is in essence three completely different ships and built in different yards so there is a rather big overhead in engineering and administration surrounding the ships construction. In the bigger yard that slap all the stuff together there can be more multi tasking and there is less overall administration and the large hauler simply has to be viewed as a much less complex piece of equipment overall.

As mass in Aurora is volume rather that weight you might somehow appreciate the fact that it will logistically be easier to construct something really big in less time when you look at the pure volume of the ship being built.

Now... in some instances there might be some oddities as in this case, but that is because you are using a Tug. Now, from a game design perspective tugs are not meant to be used as a train hauling cargo modules around. First of all it would provide huge micromanagement as you would not be able to automate it and would have to deal with every shipment manually which likely would get tedious very fast. Therefore as a concept comparing them might not even be that meaningful to begin with, not saying you can do it as practical thought experiment.
But.. the reason in this case is that build-time is directly related to the ships cost and not it's size... if you break a freighter in two you get the more costly part in a smaller package. This will then translate to a longer build time by mechanical standards.

The only way you can rationalise this is that smaller volume ships simply are more complex to build in general. If you build the ship using more volume then there are more volume where the smaller more complex components can be fitted, so these components are scattered in a bigger overall volume which make it easier to construct the whole ship. Imagine the engines having a much larger volume to fit into and therefore easier to overall construct when they don't have to be strapped all together in a more overall compact area. At least that is one way to work backwards as a viable reason why it is faster to produce the whole ship than compressing all the expensive components in one tiny little package.

As  a final note... I would not look at your example as if you take a hacksaw and just pull off the cargo modules and that is how you get two separate "ships". All three examples are their own separate entities and everyone have its own engineering challenges some more difficult than the other.

[SevenOfCarina]

There's an easy explanation for this, at least in this case : the tractor+trailer combination (1906.4 BP) is more expensive than the freighter vessel (1786.5 BP), since the smaller vessels will need to dedicate more of their volume, proportionally, to armour protection. It's significant enough to notice here because armour is just so much more expensive compared to cheap, bulky cargo holds and the like.

You could think of it as an economy-of-scale advantage, if you want.

[Ulzgoroth]

I'm inclined to agree that this is a design issue.

Time to build a ship should depend on time to complete the ship's overall structure and time to install the last components inside the hull. The lower bound would be the maximum of the structural and component build times, the upper bound the sum, and I'd expect the ultimate result to usually be near the lower bound - building in a freefall shipyard means you don't need to wait for structural support before setting to work on components.


Oh! On the other hand, try this:

Aurora spaceships have their components crammed in together as tightly as possible to minimize surface area that needs armor. When you pack stuff in tightly like that, each component doesn't get to have a neat bounding box - small components get stuffed into the concavities of larger components and the cracks where they can't sit neatly side by side. Which means you've got to carefully sequence things so that you get all the bulky sub-components into the places where they need to go before you build other components that would block the access path. And when you're doing that, bulky but cheap components make your life easier, not harder - they mean large volumes of your ship that take so little time to complete that you can leave them for the last minute, thus providing easy access to work on all the other more labor-intensive portions with maximal efficiency.

[skoormit (OP)]

...smaller volume ships simply are more complex to build in general. If you build the ship using more volume then there are more volume where the smaller more complex components can be fitted, so these components are scattered in a bigger overall volume which make it easier to construct the whole ship. Imagine the engines having a much larger volume to fit into and therefore easier to overall construct when they don't have to be strapped all together in a more overall compact area.

Aurora spaceships have their components crammed in together as tightly as possible....
...bulky but cheap components make your life easier, not harder - they mean large volumes of your ship that take so little time to complete that you can leave them for the last minute, thus providing easy access to work on all the other more labor-intensive portions with maximal efficiency.

The tractor instead is a very "dense" ships. It's full of complex components all crammed together one next to each other. There's not much space for anything else, heat exhausts and the like have to be placed very carefully because you have so many delicate components in a small space. So, it's a lot harder to assemble correctly without design problems, and thus takes longer to build.

Thanks, guys. This is an explanation I can wrap my head around.
One way of putting it: compactness has a complexity cost, and complexity costs time.

Here's another way of reconciling it with my example:

As I originally imagined it, the HaulerXL was essentially just a big cargo hold on one side, and all the other components on the other side.
If I sawed the thing in half, it shouldn't take longer to build one side than it took to build the whole thing, no matter how one reasoned about surface space available for concurrent work tasks, etc.
However, that restriction is just the fault of my visualization of the ship's space. I'm using Earth analogues: a 16-wheeler, a freight train, a cargo jet, etc. These vehicles all, broadly speaking, have a large space for carrying stuff, and another space for the engines and whatnot.
But this type of broad spatial division need not be the case for a TN spacecraft.
Instead, think of the HaulerXL as, first, a sphere the size of the cargo space. Then add the other components, evenly spaced, around that sphere. The components are spread out, therefore design is simple and work is efficient. You could have one work crew installing each engine, say, and they wouldn't get in each other's way.
If you build those same components without that large volume around which to spread them, the design is complicated, and the work is less efficient. The work crews get in each other's way.

There's an easy explanation for this, at least in this case : the tractor+trailer combination (1906.4 BP) is more expensive than the freighter vessel (1786.5 BP), since the smaller vessels will need to dedicate more of their volume, proportionally, to armour protection. It's significant enough to notice here because armour is just so much more expensive compared to cheap, bulky cargo holds and the like.

That's fine as an explanation for why the Tractor plus Trailer costs more and takes longer to build in total.
But it is not sufficient to explain why the Tractor takes longer to build by itself than the HaulerXL. The Tractor has, by definition, no more of anything than does the HaulerXL. In fact, it has about 42% less armor.