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Offline ISN (OP)

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Engineering spaces and maintenance storage
« on: June 26, 2021, 04:39:25 PM »
Inspired by recent posts in the Changes Discussion Thread, I decided to investigate more carefully the question of how much maintenance storage should be used (if any). I took a ship design from my current game and systematically varied the balance between engineering spaces and maintenance storage bays, keeping the same overall tonnage. The ship is 32,000 tons with Magneto-plasma level tech, 18 months of deployment time, a Max Repair of 504 MSP, and a wide variety of systems including missiles, particle beams, turrets, sensors, and a small 500 ton hangar. I added engineering spaces one at a time and filled in the rest of the tonnage with maintenance. The results are as follows:

Engineering tonnageMaint tonnageMaint LifeMSPIFR
501106.50.6911193113.80%
1001051.51.161077356.90%
150981.51.441020237.90%
200921.51.7973228.40%
250861.51.92926222.80%
300801.52.08879319.00%
350731.52.18822416.30%
400671.52.27775514.20%
450611.52.35728612.60%
500551.52.4681711.40%
550486.52.42629910.30%
600426.52.4458319.50%
650366.52.4353648.80%
700306.52.4148978.10%
750241.52.3543807.60%
800176.52.2738637.10%
850116.52.1933976.70%
90056.52.0829306.30%
95001.9624996.00%

These values will depend greatly on the details of your ship design -- its size, deployment time, Max Repair value, etc. But they suggest that if your only goal is to maximize deployment time, then an engineering:maintenance ratio of around 6:4 or 7:3 may be ideal, although using more engineering spaces doesn't hurt deployment time too much.

But of course maximizing deployment time is not the only goal one has when designing a ship. One issue to consider is the variance in your ship's maintenance life. While only using engineering spaces can give you a decent (although not optimal) nominal maintenance life, the rate at which you use MSP will have a very high variance: you might get lucky and have few failures, or you might get very unlucky, have several engine failures in a row, and run through all your MSP. Adding more MSP can help reduce this variance.

Another factor is the cost of MSP. While removing engineering spaces in favor of MSP storage can in some cases increase deployment time, over the lifetime of a ship the extra MSP usage can add up. The 2499 MSP of the all-engineering spaces design requires 249.9 Duranium and Gallicite and 124.95 Uridium, compared to 583.1 Duranium and Gallicite and 291.55 Uridium for a design with 12 engineering spaces (which gives the longest maintenance life) -- more than double the mineral usage. How much this ends up mattering will depend on the size of your fleet and how often it's out of port, but I think this can be substantial. (An engineering space requires 10 Duranium (plus more crew accommodations) compared to 1.5 Duranium and 1.5 Neutronium for a Maintenance Storage Bay of the same size, but I think over the lifetime of a ship these costs are much less than that of the MSP itself.)

What about weapon failures? The weapon failure rate is 1% as per the rules post. I added up the expected MSP usage from all my weapons assuming I empty the magazines and fire ten salvos with my beam weapons (this takes 150 seconds, the same amount of time it takes to empty the magazines). I got was the surprisingly low value of 153.7 MSP. This number will of course vary greatly depending on your ship design. For instance, if I replaced all missile launchers and magazines with particle beams this value would increase to 180.31 MSP. But this is still very small compared to the amount of MSP carried even by a ship with only engineering spaces, so it seems that weapon failures should not be a major concern. There are some caveats to this conclusion, though. One is again the issue of variance: while a 1% failure rate is very low, it means that the variance in MSP usage is fairly high. For instance, again using the all-particle beam design, there is a 12.4% probability of four or more weapon failures over the course of an engagement, requiring 379.6 MSP or more -- still not very much, but somewhat more substantial. Another factor to consider is that I've been running these numbers on a fairly large ship. A smaller ship will have fewer weapons but also fewer MSP, and I don't know how those will balance out.

There are probably lots of other factors that I've neglected here, and all of these numbers will depend greatly on your ship designs and on how they're used, but I've spent more than enough time on this already. I hope you find it useful! I know this is going to have a big impact on my ship designs going forwards.
 
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Offline nuclearslurpee

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Re: Engineering spaces and maintenance storage
« Reply #1 on: June 26, 2021, 05:02:26 PM »
Excellent post, I always approve of thought-out mechanics posts as they are useful and generate valuable discussions.  :)

Another factor is the cost of MSP. While removing engineering spaces in favor of MSP storage can in some cases increase deployment time, over the lifetime of a ship the extra MSP usage can add up. The 2499 MSP of the all-engineering spaces design requires 249.9 Duranium and Gallicite and 124.95 Uridium, compared to 583.1 Duranium and Gallicite and 291.55 Uridium for a design with 12 engineering spaces (which gives the longest maintenance life) -- more than double the mineral usage. How much this ends up mattering will depend on the size of your fleet and how often it's out of port, but I think this can be substantial. (An engineering space requires 10 Duranium (plus more crew accommodations) compared to 1.5 Duranium and 1.5 Neutronium for a Maintenance Storage Bay of the same size, but I think over the lifetime of a ship these costs are much less than that of the MSP itself.)

This is an important factor. A ship will typically have a total lifetime on the order of decades, thus you want to look at is the total MSP divided by maint life as this gives a rough estimate of the MSP consumption per year (lifetime average). Multiplying by the expected service lifetime gives an estimate of total MSP needed, which will generally tend to imply that a mostly Engineering Spaces doctrine is generally better. However, there is a complication because ships do not spend their entire service life away from maintenance facilities, so in a 20-year service life they may only be "at sea" for 4-5 years. And they may not necessarily use all the MSPs at the estimated average rate, for example if I have a 3-year maint life but overhaul every 18 months the MSP usage of the ship will be much lower.

Quote
What about weapon failures? The weapon failure rate is 1% as per the rules post. I added up the expected MSP usage from all my weapons assuming I empty the magazines and fire ten salvos with my beam weapons (this takes 150 seconds, the same amount of time it takes to empty the magazines). I got was the surprisingly low value of 153.7 MSP. This number will of course vary greatly depending on your ship design. For instance, if I replaced all missile launchers and magazines with particle beams this value would increase to 180.31 MSP. But this is still very small compared to the amount of MSP carried even by a ship with only engineering spaces, so it seems that weapon failures should not be a major concern. There are some caveats to this conclusion, though. One is again the issue of variance: while a 1% failure rate is very low, it means that the variance in MSP usage is fairly high. For instance, again using the all-particle beam design, there is a 12.4% probability of four or more weapon failures over the course of an engagement, requiring 379.6 MSP or more -- still not very much, but somewhat more substantial. Another factor to consider is that I've been running these numbers on a fairly large ship. A smaller ship will have fewer weapons but also fewer MSP, and I don't know how those will balance out.

How we define "engagement" is quite variable...for example, a railgun brawling fleet will end a battle in 2 minutes or less, so firing their weapons about ten times is a good estimate. However, a particle beam or spinal laser sniping fleet may take much longer and fire many more shots due to the low accuracy at extreme ranges. In my AAR campaign these kinds of beam sniping engagements can take 10s of minutes easily. MSP usage in a battle can thus easily climb up into the 1000s of MSP for a moderately-sized ship in this circumstance.

It is also worth considering that the MSP usage will deduct from a ship's effective maintenance life, so if I have a ship with a 2-year maint life and 2,500 MSPs and I use 500 MSPs in a battle, my effective maint life will drop... not linearly, but by a few months surely. Because of this I think it is better to design first for the desired maint life/failure rate depending which metric you want to use, then add MSP bays to resupply the weapons for what you estimate is a typical engagement.
 
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Offline Bremen

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Re: Engineering spaces and maintenance storage
« Reply #2 on: June 26, 2021, 05:27:03 PM »
But of course maximizing deployment time is not the only goal one has when designing a ship. One issue to consider is the variance in your ship's maintenance life. While only using engineering spaces can give you a decent (although not optimal) nominal maintenance life, the rate at which you use MSP will have a very high variance: you might get lucky and have few failures, or you might get very unlucky, have several engine failures in a row, and run through all your MSP. Adding more MSP can help reduce this variance.

In addition to the number of failures, the type of failure also matters a lot. A ship that keeps having life support or AMM launcher failures won't use much MSP, but if it keeps rolling a very large engine or shield generator as a failure it could use them up quick. So that's another reason why maintenance storage could reduce the variance (statistically, anyways).

Quote
Another factor is the cost of MSP. While removing engineering spaces in favor of MSP storage can in some cases increase deployment time, over the lifetime of a ship the extra MSP usage can add up. The 2499 MSP of the all-engineering spaces design requires 249.9 Duranium and Gallicite and 124.95 Uridium, compared to 583.1 Duranium and Gallicite and 291.55 Uridium for a design with 12 engineering spaces (which gives the longest maintenance life) -- more than double the mineral usage. How much this ends up mattering will depend on the size of your fleet and how often it's out of port, but I think this can be substantial. (An engineering space requires 10 Duranium (plus more crew accommodations) compared to 1.5 Duranium and 1.5 Neutronium for a Maintenance Storage Bay of the same size, but I think over the lifetime of a ship these costs are much less than that of the MSP itself.)

The initial cost shouldn't be ignored, but it's worth noting that (IIRC) you get any remaining MSP back when you scrap a ship, so in theory it's more like the cost is locked up while you use the ship instead of it actually increasing the cost. Unless, of course, it gets blown up.

This is an important factor. A ship will typically have a total lifetime on the order of decades, thus you want to look at is the total MSP divided by maint life as this gives a rough estimate of the MSP consumption per year (lifetime average). Multiplying by the expected service lifetime gives an estimate of total MSP needed, which will generally tend to imply that a mostly Engineering Spaces doctrine is generally better. However, there is a complication because ships do not spend their entire service life away from maintenance facilities, so in a 20-year service life they may only be "at sea" for 4-5 years. And they may not necessarily use all the MSPs at the estimated average rate, for example if I have a 3-year maint life but overhaul every 18 months the MSP usage of the ship will be much lower.

Because the costs of being at port or on a mission are different, that actually suggests advantages for different roles. A ship that mainly sits at a fleet base, or in a hangar, until it's needed might benefit more from a 7/3 mix, while something like a patrol ship that guards a jump point or a group of fuel harvesters might want more engineering spaces since they'd reduce the ongoing cost of MSP.
« Last Edit: June 26, 2021, 05:28:42 PM by Bremen »
 
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Offline ISN (OP)

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Re: Engineering spaces and maintenance storage
« Reply #3 on: June 26, 2021, 05:35:01 PM »
How we define "engagement" is quite variable...for example, a railgun brawling fleet will end a battle in 2 minutes or less, so firing their weapons about ten times is a good estimate. However, a particle beam or spinal laser sniping fleet may take much longer and fire many more shots due to the low accuracy at extreme ranges. In my AAR campaign these kinds of beam sniping engagements can take 10s of minutes easily. MSP usage in a battle can thus easily climb up into the 1000s of MSP for a moderately-sized ship in this circumstance.

This is a very good point, and helps square the low numbers I got with the fact that I've definitely experienced maintenance shortages in combat. I'm likely underestimating how many salvos long engagements can take.

Because the costs of being at port or on a mission are different, that actually suggests advantages for different roles. A ship that mainly sits at a fleet base until it's needed might benefit more from a 7/3 mix, while something like a patrol ship that guards a jump point or a group of fuel harvesters might want more engineering spaces since they'd reduce the ongoing cost of MSP.

Yeah, I'm curious how all these numbers change when looking at ships designed for long-term patrol or picket duty. While you're right that the MSP cost can add up, I've experienced problems with high variance in MSP usage for my patrol craft. I have distinct memories from my previous game of picket ships running out of MSP while other ships in the same fleet had barely gone through any, which prompted me to increase the maintenance storage/engineering ratio considerably in my designs.
 

Offline Bremen

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Re: Engineering spaces and maintenance storage
« Reply #4 on: June 26, 2021, 05:52:42 PM »
Yeah, I'm curious how all these numbers change when looking at ships designed for long-term patrol or picket duty. While you're right that the MSP cost can add up, I've experienced problems with high variance in MSP usage for my patrol craft. I have distinct memories from my previous game of picket ships running out of MSP while other ships in the same fleet had barely gone through any, which prompted me to increase the maintenance storage/engineering ratio considerably in my designs.

This actually makes me wonder if the best fit for long term patrols might be engineering space heavy ships with a MSP tender (which can be civilian I believe?). Lots of engineering spaces mean they'll go through MSP slowly, while the tender can greatly increase deployment lengths while all but eliminating the variance.
 

Offline Jorgen_CAB

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Re: Engineering spaces and maintenance storage
« Reply #5 on: June 26, 2021, 06:07:28 PM »
This is not a simple answer in my opinion because what ever you do you will need to make some sort of concessions.

Do you want a ship that is reliable and consume little MSP but at the expense of more mass for engineering or do you want your ships to start consuming MSP as soon as they leave port but able to fit more weapons on them?!?

I guess the role of the ship will have to determine how they are designed and the amount of MSP you can afford to spend for maintenance failures.

As ships maintenance failures go up the longer they stay out of port you should try to estimate the "normal" mission time ships are deployed and make some judgment based on that. If you can reduce the MSP spent on failures for most ships on most missions you will save yourself allot of resources in the long run. But burning resources for the occasional long missions should be something you can survive and streamlining your ships to fit more mission tonnage probably will pay off in the end.
« Last Edit: June 27, 2021, 03:28:34 PM by Jorgen_CAB »