Single or multiple levels of turrets?

[erick]

There seems to be conflicting information about this out there.

For example this guide:

https://nemstar.webs.com/Astro_Empires_ ... guides.htm

Says:

Defenses work best in multiple levels.

While this:

http://espacesociety.org/astro-empires/ ... nse-guide/

Says:

Build the highest turret you have researched to the quantity necessary to satisfy your economic defense needs, but at least 2. Disband all lesser turrets.

Do not group turrets. Weaker turrets provide substantially less protection as the base economy increases.

What's the current wisdom about this? Is it more of a matter of economics or is multiple levels actually weaker than a single one? Let's say we have these two configurations:

Ion 15 + Photon 10
Photon 15

The first one has 32x3 + 64x2 = 224 power/armor and 3x2 + 2x6 = 18 shield.

The second one has 3x64 = 192 power/armor and 3x6 = 18 shield.

Is the first one still inferior, other than taking up space that could be used elsewhere? Or (I suppose) does it depend on the attacker's fleet?

And, if its optimal to keep a single level and I'm striving to 3 (15/15) of each one, would you disband the previous turrets one by one as you build new ones or dump all three at once (or, well, in three hours) when the new ones have finished? Or earlier (say, when reaching 2 on the stronger turrets)?

[Wlerin]

The main reason not to mix turrets is because it's a waste of Area, Energy, and Population. That said the specific example you give is also bad for another reason. Let's see if I can explain why.

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First, Shields don't stack, they reduce incoming damage by a fixed amount.
Second, during combat, ships don't attack every target equally, they focus most of their power on those targets they can do the most damage to.
Third, after combat resolves, the percentage remaining value of your defenses is determined, and all turrets are then set to that same percentage.

Let us suppose a fleet of Fighters attacks a base with 15 Ion Turrets and 10 Photon Turrets.
Both Defender and Attacker have the same Technologies:
14 Armour and 14 Laser
6 Shielding
Some insignificant amount of Ion and Photon tech (irrelevant for this explanation).

The Ion Turrets will have 2.6 Shields, the Photon Turrets 7.8.
The Fighters have 3.4 Power.

As a result, each Fighter does 0.834 (3.4-2.6 + 3.4*0.01) damage to the Ion Turrets, and only 0.034 damage to the Photon Turrets. Because the Fighters can deal so much more damage to the ITs, roughly 95%[1] of their power will target the Ion Turrets, with only ~5% being wasted on the Photons. This means the attacker only needs to bring a little more than enough to one-shot the Ion Turrets on their own in order to knock them down to 0%.

For simplicity's sake, let's say the Attacker brought the Ion Turrets to 0 but the Photons weren't scratched.
Total Value: 15*256 + 10*1024 = 14080
Remaining: 0*256 + 10*1024 = 10240
Percentage: 10240/14080 = 72.7%

After the battle resolved, the defenses would be set to 72.7%. Even though the Photons were "unscratched" during the battle, after equalisation, they would only have 7.27 units left. Technically, this does result in the defenses having more power left to damage the attacker in round 2, but it also means those Photon Turrets, which would otherwise require a massive Fighter swarm to take down, are suddenly vulnerable to much smaller (and sneakier) swarms.

But this effect is only really a problem when the two turret types are a) close in value, and b) the cheaper one is vulnerable to a highly efficient unit while the other, more expensive one isn't. Basically, this means only Plasma + Ion and Ion + Photon are bad combos.

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[1] (0.834/(0.834+0.034)=0.96, but it's not quite that simple)

[erick]

Thank you very much, that's in fact a great explanation!