Commercial Engine Size Ratio: What Am I Missing?

[Bryan Swartz (OP)]

For reference, I haven't played in a number of years but am returning to learn C# and excited about 2.2, trying to get up to speed before that hits. 

I've seen recommendations in multiple places for commercial ships to have engines at 40-50% of the ship's total size.   I don't understand why that's a good idea.  I'm designing an early-game freighter and what I'm looking at pushes me towards having engines in the 20-25% range, literally half of that suggestion.  Going higher than that, speed increase from adding additional engines approaches the cost increase from doing so.  At about 35%, the cost increase actually exceeds the speed increase in my design, and of course the ships have to spend at least some time loading and unloading even if I add extra cargo shuttle bays.  It seems to me that it would be better earlier than that point to have more freighters moving more cargo than to have larger, somewhat faster ones. 

Am I just wrong?  If so, why??

[Froggiest1982]

For reference, I haven't played in a number of years but am returning to learn C# and excited about 2.2, trying to get up to speed before that hits. 

I've seen recommendations in multiple places for commercial ships to have engines at 40-50% of the ship's total size.   I don't understand why that's a good idea.  I'm designing an early-game freighter and what I'm looking at pushes me towards having engines in the 20-25% range, literally half of that suggestion.  Going higher than that, speed increase from adding additional engines approaches the cost increase from doing so.  At about 35%, the cost increase actually exceeds the speed increase in my design, and of course the ships have to spend at least some time loading and unloading even if I add extra cargo shuttle bays.  It seems to me that it would be better earlier than that point to have more freighters moving more cargo than to have larger, somewhat faster ones. 

Am I just wrong?  If so, why??

In one of my previous posts that actually talked about something completely different, I highlighted how to me at some point the size of the transported cargo was more important than the actual speed at which it could be delivered, at least for long hauls. Now that was my case and not a rule, however, I can see how big empires do not necessarily need fast-moving cargo, which is more of a player need.

That brings me to the final point, It really depends on you, your setup, and what is your situation. Mostly this is what makes Aurora a great game. While there are universal solutions and hacks, it is very simple to either ignore them or, even better, accept that a functional design is more valuable than the perfect design in most cases. Now, a functional design is different from game to game due to the extreme RNG the game is subjected to.

[Pury]

I always stick with the 50% of total mass and 50% Power. For me it is mostly about two things:

1. If I'm using my own transport ships, usually timely delivery is very important to me. Faster ship will deliver the first batch of cargo 2x faster than if I had only 25% of mass dedicated to engines. And in cases where speedy delivery is not important, I use AI civilian ships as they do not need any fuel to operate.

2. Faster ships are safer. While bigger, cargo ships are allready big enough that they can be spoted from great distances. higher speed gives me more time to send reinforcement's to save the day.

Also for my design scaling down to 25% engine size does not bring any cost reductions. I can have 1 50% engine size or 2 25% engine size cargo ships, for practically the same cost. There are also other reasons for why you might want 50% engine mass, such ass:

Fuel savings. Bigger engines burn less fuel. although this applies some what differently depending on given ship design. for cargo ships it might be ~40% engine size.

If you have 50% engine mass, you will end up with overall fewer ship captains. For people that micromanage them for civilian ships it will translate to better overall performance thanks to bonuses.
If you use CIWS, bigger ships also benefit from them more. As they only protect the ship that takes the hits.

They are also faster to build while taking into account cargo transporting speed. For me it is 0.63 year for 25% mass and 0.95 year for 50% mass.

[Pury]

I always stick with the 50% of total mass and 50% Power. For me it is mostly about two things:

1. If I'm using my own transport ships, usually timely delivery is very important to me. Faster ship will deliver the first batch of cargo 2x faster than if I had only 25% of mass dedicated to engines. And in cases where speedy delivery is not important, I use AI civilian ships as they do not need any fuel to operate.

2. Faster ships are safer. While bigger, cargo ships are allready big enough that they can be spoted from great distances. higher speed gives me more time to send reinforcement's to save the day.

Also for my design scaling down to 25% engine size does not bring any cost reductions. I can have 1 50% engine size or 2 25% engine size cargo ships, for practically the same cost. There are also other reasons for why you might want 50% engine mass, such ass:

Fuel savings. Bigger engines burn less fuel. although this applies some what differently depending on given ship design. for cargo ships it might be ~40% engine size.

If you have 50% engine mass, you will end up with overall fewer ship captains. For people that micromanage them for civilian ships it will translate to better overall performance thanks to bonuses.
If you use CIWS, bigger ships also benefit from them more. As they only protect the ship that takes the hits.

They are also faster to build while taking into account cargo transporting speed. For me it is 0.63 year for 25% mass and 0.95 year for 50% mass.

Alsoooo more cargo trips mean more fuel (if diffrent engine design) and time spent in deep space. ticking down on maintenance.

(Edit)
Yet another advantage is that it is easier to create diffrent variants of the given design that can be produced from the same shipyard if 50% of mass is dedicated to the engines. As each change in modules (swapping Cargo for troop transports)will have lesser % impact on the cost overall. thus more wiggle room for changes.

[Bryan Swartz (OP)]

I'm confused by a couple things. 

Alsoooo more cargo trips mean more fuel (if diffrent engine design) and time spent in deep space. ticking down on maintenance.

What's the relevance of maintenance for a commercial design?

1. If I'm using my own transport ships, usually timely delivery is very important to me. Faster ship will deliver the first batch of cargo 2x faster than if I had only 25% of mass dedicated to engines. And in cases where speedy delivery is not important, I use AI civilian ships as they do not need any fuel to operate.

Edit:  Seems to me in most cases getting more cargo there slower would be better than getting a smaller amount there faster. 

scaling down to 25% engine size does not bring any cost reductions. I can have 1 50% engine size or 2 25% engine size cargo ships, for practically the same cost.

Only after you've researched a fair ways into the game, I don't think this really applies to earlygame.  I.e., the design I'm looking at the question isn't 1 or 2 engines, but 6 or 8 or 15 or 20 or whatever of the largest ones I can build.  Same with the fuel savings, I can't make larger more fuel-efficient ones. 

They are also faster to build while taking into account cargo transporting speed. For me it is 0.63 year for 25% mass and 0.95 year for 50% mass.

That would also mean slower to build accounting for cargo volume.  I'm assuming that's something that isn't important to you? 

[Bryan Swartz (OP)]

It's sounding to me like this is coming down to something Froggiest1982 kind of said;  basically it just depends on your priorities.   Which I think is interesting and good if so, rather than there being a 'right' answer. 

[Pury]

What's the relevance of maintenance for a commercial design? .

If you are escorting them with military ships. Forgot to add this important part ;P.

Only after you've researched a fair ways into the game, I don't think this really applies to earlygame.  I.e., the design I'm looking at the question isn't 1 or 2 engines, but 6 or 8 or 15 or 20 or whatever of the largest ones I can build.  Same with the fuel savings, I can't make larger more fuel-efficient ones.   

I am talking about Ion engines with 0.6 fuel usage mod. which is considered early game technology (roughly!) I don't really move around before that (maybe 1 tech earlier) as you are waaay to likely to get yourself into fights that you can not win. I usually have Ions around ~30 years mark with good fuel consumption and decent size.

That would also mean slower to build accounting for cargo volume.  I'm assuming that's something that isn't important to you?

Well let me explain what I meant. If you have 1 shipyard, in 2 years it will produce ~2 50% engine size ships or ~3 25% engine size ships. If you take those ships and try to transport a cargo, the slower ones while being more numerous, are not numerous enough to overcome the speed advantage. So in the same period of time, they will transfer less cargo. The cargo volume itself is not that important for me. But how fast and efficiently can I move it around is.

[Pury]

It's sounding to me like this is coming down to something Froggiest1982 kind of said;  basically it just depends on your priorities.   Which I think is interesting and good if so, rather than there being a 'right' answer.

Practically yes. Both approaches have diffrent advantages. Depends on the player which ones he likes more.

Edit

Seems to me in most cases getting more cargo there slower would be better than getting a smaller amount there faster. 

Out of curiosity, can you give any examples? As I can't really think of any examples where it will be better to have deliveries in bigger chunks rather than smaller, but more frequent ones.

[Bryan Swartz (OP)]

I can't really think of any examples where it will be better to have deliveries in bigger chunks rather than smaller, but more frequent ones.

I think the disconnect is that I wasn't really viewing it that way.  I would say the chunks are the same but you get more frequent ones with the smaller freighter because you can have more of them.  Or if you have the same amount of ships, you're paying a lot more for the same volume of transport.  The larger, faster freighter may move twice as fast as the smaller one and only take 50% more build time, but it also takes more than twice the resources to build which means less of other things get built.

My brain is starting hurt with all the permutations here though, so probably best for me to think about something else for a while.     I definitely can see more of a case both ways, so I'd say you've made a partial sale. 

I usually have Ions around ~30 years mark with good fuel consumption and decent size.

Just a terminology thing then.  I definitely wouldn't call that earlygame. 

If you are escorting them with military ships. Forgot to add this important part ;P.

Makes sense.  I can't imagine escorting all my freighters with military ships.  I would think the cost of that would be exorbitant. 

[nuclearslurpee]

In practice, what matters for commercial ships is not size, speed, etc. but effective throughput. This means you need to factor in build cost, fuel usage, etc.

Consider a freighter with 25,000 tons cargo space and attendant necessities, let's say it costs 250 BP for all of this. Suppose I can put 25% of the total size as engines at whatever tech level, costing another 250 BP and a speed of 1,000 km/s for sake of example. Now say I double the engine size, costing yet another 250 BP, and I can achieve a speed of 1,600 km/s as my engines are now 40% of total size.

So for 500 BP I can get a freighter that moves 25,000 tons of cargo at 1000 km/s, or for 750 BP I can get a freighter that moves 25,000 tons of cargo at 1600 km/s. If you assess the throughput per BP you will see that the latter freighter is a bit more efficient for the cost, so far this supports the argument for a larger engine fraction. However, there are several complications:

• Engines cost gallicite, and gallicite is often a precious resource and highly valuable. Not all minerals are created equally.
• This math depends on engine cost relative to the cost of everything else - cargo bays, shuttle bays, etc. don't change in cost over time but engines do. If your engine block costs you 500 BP for 25% of the total mass instead of 250 BP, the above math will work out (slightly) in favor of the first freighter. Therefore it depends on your tech level.
• We also have the opportunity to build a bigger freighter in terms of cargo space rather than engines. Suppose it would cost us 100 BP to double the cargo space in the example above. For 750 BP I could get a freighter moving 25,000 tons of cargo at 1600 km/s, or for 600 BP I could move 50,000 tons of cargo at approximately 570 km/s. In that case, the faster freighter is still a bit more efficient. However, if the baseline engine block costs 500 BP instead of 250, the higher-capacity design starts to pull ahead - but again, the difference is not very large.

In many cases which are of practical relevance, the difference in throughput efficiency (per build point) is not very great, perhaps a 10% difference between different options. When you get to higher tech levels with high engine powers and small minimum EP modifiers, then the analysis can shake out that certain approaches will be much better than others at least on paper. For example, the effect of the EP modifier on engine cost when it is below 100% is (EP modifier)^2, which means a 40% Ion Engine is going to be cheaper than a 50% NGC Engine of the same total engine power. I did not analyze the EP modifier effect above but it becomes very important.

Add to this, you will have strategic and operational concerns beyond pure economic efficiency, for example a freighter with 10% efficiency engines might be the most cost-effective, but if you need to deliver 10 million people to a system 6 transits away to establish a naval base before the aliens come then such a slow freighter will not be suitable for the task. Consider also the value of building multiple ship classes from a single shipyard; the math looks very different for a colony ship, since cryogenic modules cost an order of magnitude more than cargo bays for the same tonnage. In a vacuum, a faster colony ship is quite likely to be the most efficient design, but that means your freighter class must be much more expensive if you want to build it from the same yard.

So the tl;dr version is this: there are a wide range of commercial ship designs which are viable and arguably optimal under different conditions. In practice, you will probably have far more pressing considerations than getting the most efficient possible freighter, colony ship, etc. My advice is to prefer what is simple and easy, because it will work well enough for your needs, and then look into making changes as the situation evolves in-game. In Aurora there is rarely a true optimum so why worry about finding it? 

[Ultimoos]

I've never put much thought in to my civilian ship designs. I just have light freighters that are faster with about 30-35% engines. I have medium freighters with 20-25% engines and than there are heavy things that have 10-15% engines.

[Navalgazer420XX]

Analyzing this with a model was beyond me, so I made a spreadsheet to guess and check the performance of different freighter designs on a number of route lengths.   

There's a sweet spot for speed that maximizes total throughput per mineral spent for a given trip.    This changes depending on distance: an Earth-Luna freighter can be slow because it spends most of its time un/loading, and a 100bkm route requires a faster ship.    It's also higher for colony ships: the greater Merc+Dur cost of Cryo vs Cargo holds justifies a faster ship to maximize the throughput per mineral spent, because expensive components are wasted by moving them slower.       
You can throw a spreadsheet like this together in 20 minutes if you want to brute force the problem rather than come up with an elegant mathematical solution.   

There's also the Value of Time or VoT cost of cargo that's not doing anything while in transit.    This is much harder to analyze, because there are so many different cargo types.    An easy brute force answer would be to set up two identical mining worlds an equal distance from earth, and ship automated mines to them with a fast and slow freighter.    The ratio of minerals produced by the fast world vs the slow world in a given time is the VoT saved by the faster freighter.   

Now that commercial traffic potentially requires guarding, there's also the cost of escorts.    If you are guarding a regular shipping route with stationary bases, cargo speed doesn't matter.    For individually escorting long distance convoys, a slow freighter or tugged station will increase the MSP and opportunity costs of escort.   

Since all these extra factors push in the direction of faster cargo ships, I think a throughput-maximized freighter will be too slow for all but the shortest routes (planet-moon, in-system mining cyclers, etc.    ).    Adding in the player micro-management frustration that's the actual limiting factor of aurora playthroughs, I'd say freighters should be much faster than the naive optimum.     

IMO the biggest factor is that researching the <50% power modifiers is a trap, as all your civilian ships will start using slower engines for no benefit (unless this changed in recent versions).    If you're going to use sub-50% engines, SM-delete the research after designing the component.   

(If anyone knows why I'm getting un-editable triple-spacing after each period, please let me know how to fix it!)

[kyonkundenwa]

(If anyone knows why I'm getting un-editable triple-spacing after each period, please let me know how to fix it!)

The forum adds them automatically to break spam links. It goes away once you have enough posts. You also can't post files/images yet I think, but you probably just haven't noticed.