The major takeaway for me is that failure rate is proportional to the square of ship size, but inversely proportional to the (non-squared) engineering tonnage.
Meaning that if you double the ship size, you have to quadruple the engineering tonnage to keep the same AFR.

Sure, but the same is true of doubling the number of ships. Two ships with 100% AFRs have a total of a 200% AFR. Increased failure numbers with increased tonnage is the expected behaviour, not a particular function of a big-ship design philosophy.

For me, what this really drove home is that AFR targets should never be fixed numbers - they need to be tonnage-based.

Quote from: skoormit on April 23, 2020, 10:31:28 PM

Quote from: Alsadius on April 23, 2020, 05:40:44 PM

...
If a ship has any engineering spaces, the AFR is equal to [0.04%/engineering tonnage percentage*total tonnage].
...

This is the same as:  (Total HS ^ 2) / (Eng Tons)

(Keeping in mind that 1 HS = 50 tons.)

In your example, 9995Tons = 199.9HS.
So: 199.9^2 / 100 = 399.6001

Yup. There's a bunch of ways to show the math. I figured the formula that I used was the most useful in normal circumstances, but if there's something specific you want to look at, you can and should play with the math here.

The major takeaway for me is that failure rate is proportional to the square of ship size, but inversely proportional to the (non-squared) engineering tonnage.
Meaning that if you double the ship size, you have to quadruple the engineering tonnage to keep the same AFR.

Talking about shore leave.  Is there a separate order for that or is follow order needed? (for example survey ships shore leave)

There is no separate order, but overhaul usually takes longer and counts as leave time.

Quote from: Jorgen_CAB on April 23, 2020, 06:31:57 PM

Pretty good overview... ships actually have become a bit more expensive since VB6 version. I think the cost for paying total ship cost there was 20 years, but I could be wrong though.

It can be quite valuable to keep your maintenance life value to around 2-3 times the ships deployment time. Every time you retire the ship to port for resting the crew you also overhaul the ship. Also, the more engineering sections you have you also have a higher chance that you don't get any failures. If the ship have maintenance life of three times the deployment time there is a very good chance you get zero failures.

You also should consider not using maintenance storage on warships. You are way better of adding more maintenance facilities to reduce the chance of failure instead. Make sure to have supply ships close at hand instead.

I usually keep my maintenance life of ships in the range of 1.5-2.5 years for most regular warships that typically have between 6-12 month of deployment time. It is a fairly good trade off between space and economy in the long run. Engineering spaces will generally keep maintenance costs down. You also should consider and engineering station on larger ships as that will keep maintenance failure even further down, especially with a good officer in charge.

I like maint bays on warships, to a certain limited extent. I don't like relying on my (slower, undefended) supply ships keeping pace unless I have to, and spending 50 tons to get my MSP up is often a good investment. Doubly so if the ship needs to refill MSP for parasites, or if it has beams that can break in combat. Maint storage is often a better way to keep your beams firing than engineering spaces are, because your supply ships should really not be entering beam range, and the warships can't easily pull back to refill on MSP.

Maintenance bays do have some uses but overall they are not needed all that much. Engineering sections will both reduce the need for MSP and increase the MSP at the same time.

If you build a dedicated beam ship you "might" need some extra MSP, but even then it should be rare to run out of MSP in most cases. I think it mostly is for planetary bombardment purposes that you will run out of MSP that way. If the beam ship has a health overall maintenance life cycle it is less likely to drain its MSP on their way to the fight and have more MSP from the Engineering sections too.

You also can have relatively fast supply ships too, but I never really had much problem with my supply train anyway in Aurora when I needed them.

...
If a ship has any engineering spaces, the AFR is equal to [0.04%/engineering tonnage percentage*total tonnage].
...

This is the same as:  (Total HS ^ 2) / (Eng Tons)

(Keeping in mind that 1 HS = 50 tons.)

In your example, 9995Tons = 199.9HS.
So: 199.9^2 / 100 = 399.6001

Quote from: Alsadius on April 23, 2020, 05:40:44 PM

Technical note: I'm not 100% sure that the failure rate is based strictly on years the way I've implied - it's possible that months matter too, and a failure less likely in month 1 than it is in month 11. However, the formulas on the ship design screen seem to imply it's flat throughout each year.)

I suspect that maintenance failure rate is based on the ship maintenance clock, so it would increase every construction cycle rather than having big jumps every year.

Quote from: Alsadius on April 23, 2020, 05:40:44 PM

When an item is damaged in combat, the damaged ship cannot self-repair unless it has a Damage Control module. Even if it does, the repair cost is twice as high as the item's cost in BP.

When you say damage control module I assume you mean damage control rating, which is provided in small amounts by engineering spaces.

Migi is correct on both points.

Technical note: I'm not 100% sure that the failure rate is based strictly on years the way I've implied - it's possible that months matter too, and a failure less likely in month 1 than it is in month 11. However, the formulas on the ship design screen seem to imply it's flat throughout each year.)

I suspect that maintenance failure rate is based on the ship maintenance clock, so it would increase every construction cycle rather than having big jumps every year.

When an item is damaged in combat, the damaged ship cannot self-repair unless it has a Damage Control module. Even if it does, the repair cost is twice as high as the item's cost in BP.

When you say damage control module I assume you mean damage control rating, which is provided in small amounts by engineering spaces.

Pretty good overview... ships actually have become a bit more expensive since VB6 version. I think the cost for paying total ship cost there was 20 years, but I could be wrong though.

It can be quite valuable to keep your maintenance life value to around 2-3 times the ships deployment time. Every time you retire the ship to port for resting the crew you also overhaul the ship. Also, the more engineering sections you have you also have a higher chance that you don't get any failures. If the ship have maintenance life of three times the deployment time there is a very good chance you get zero failures.

You also should consider not using maintenance storage on warships. You are way better of adding more maintenance facilities to reduce the chance of failure instead. Make sure to have supply ships close at hand instead.

I usually keep my maintenance life of ships in the range of 1.5-2.5 years for most regular warships that typically have between 6-12 month of deployment time. It is a fairly good trade off between space and economy in the long run. Engineering spaces will generally keep maintenance costs down. You also should consider and engineering station on larger ships as that will keep maintenance failure even further down, especially with a good officer in charge.