I've included quotes from the post above precisely because I disagree with some of what's said, and I'd like to give context as to why and how and what I'm thinking in doing so. That said, I want to stress that this is ultimately just different preferences in ship design and naval doctrine. One of the great things about Aurora's design granularity is that it does allow and accomodate deep differences like this.
That... is a lot of AMMs and a lot of launchers. What do your magazines look like? Would also be curious about the profile of the missile you're using.
I tend to agree, but that might not be a bad thing. At ion, with some basic parity assumptions, your S4 missiles should be going
about 14-18kkm/s. This means that with the same assumed tech, your AMMs should get
about 20% hit chance on them. Similarly with enemy missiles at the same tech. This means you need 5 AMMs per missile in the enemy salvo if you rely solely on AMMs for missile defense. Put another way, with 50 AMM launchers you can expect to kill 10 missiles per enemy salvo, assuming salvos are large enough. Given your magazine depth, you can expect to do this 41 (actually 40.6) times.
In other words, in your theoretical combat tour, you think you may need to intercept 206 enemy missiles with your AMMs per AMM cruiser you field. Whether that's true or not depends on your particular game of Aurora. (How the enemies have developed their offensive doctrines, how long this cruiser spends in active warfronts between resupplies, whether this is intended to be your primary anti-missile defense or not, etc.)
Compared to the gauss cannon, I find that 10cm and 12cm railguns are superior at low and mid tech-levels as anti-warhead and general-purpose weapons. Just preference.
Railguns are fairly clearly superior to gauss in a PD role at this tech level. Your escort cruiser is moving at 5kkm/s; with parity assumptions (reactor tech, etc.) and max crew grade bonus, against missiles moving 20kkm/s your expected shootdowns/HS is 0.32 (or 1.34 per gun, counting crew and reactor space).
With gauss at rough parity (ion-level), your expected shootdowns/HS is 0.4592, or 144% of a railgun. Better, right? Yes, but getting gauss turrets to parity in research takes 29k RP, whereas you can build these railguns straight from a transNewtonian start. Imagine what you could do with an extra 29k RP. Here's one: have magneto-plasma engines already. (I'm not counting component research time, either, since it's basically negligible. But that, too, is more expensive for gauss turrets.) On top of that, these gauss turrets are more than 144% of the BP cost of a railgun, much more. (I don't have exact numbers on that because I don't have Aurora with me and the wiki is unhelpful in this regard.)
I also think that your active sensor missile detection ranges are just a little short. You have a lot of launchers, but the reload time is long. Time and distance are your friends. For that, you need detection. Understandably, this is a bigger problem at low tech levels.
Putting numbers on this, with a detection range of 1.8mkm, enemy missiles travelling 20kkm/s will be detected for 90 seconds. This gives you time for 1 initial and 4 follow-up salvos, which funnily enough is exactly the ratio you probably want with your AMMs being ion. So that's probably fine.
Except that's the PD sensor on your escort cruiser; the AMM sensor on your AMM escort goes to 10mkm. I doubt you have any AMMs capable of that range, and if you do you probably shouldn't, for the reasons just mentioned. (You could instead invest in speed and agility to improve hit chance.) Again with simple parity assumptions, an AMM with 10mkm range has a 20.2% chance to hit, and you'd better hope it moves first because it's actually slower than the target missile. At 5mkm you get 21.4%, and at 2mkm you get 21.8%. 0.4% might not seem like much, but it will save you a lot of gallicite in the long run. Plus, a smaller AMM range means a smaller PD sensor means savings on an expensive component and more HS to dedicate to something else, like engines (see below).
In my opinion 5000 km/sec is WAY too fast for Ion tech, especially with that 1.5x engine power multiplier thrown in. As Iranon here on the forms once told me, if you devote 40% tonnage or less to engines while keeping the power mod at around x.8, that's a much more efficient setup, generally speaking. Yes, your ships will be slower as a result, and fighting Precursors will therefore be tricky. But once you start salvaging those delicious Precursor wrecks, your engine tech will start getting to where you really want it to be.
This is the bit with which I disagree the most. In my opinion, 5kkm/s is about right at ion tech, maybe slightly fast for missile ships. But for beam combatants, you want that higher - 6kkm/s at least. After all, you want to close with the enemy, and closing time is all about the delta in your speeds. Smaller delta, even if you're faster, and the enemy gets more time to shoot you in which you can't respond.
Further, and even more important (for all ships), having the speed advantage allows you to dictate the engagement. Don't want to fight? You don't have to if you can run away. Want to fight but he doesn't? Too bad; you get to decide.
Even further, speed acts as armour. If you're faster, the enemy has a linearly proportional decrease in his ability to hit you with any weapon. If you're
much faster, you're also
much harder to hit.
Even further than that, for beamships, speed acts as weapons (up to your BFC tracking speed). If you're too slow, you take a penalty to hit even if the enemy decides to close with you.
Finally, for PD, more spent on the engine means your railgun PD (which you're using, right?) is more effective. It all hangs together. So how do we get those numbers up?
Right now you have 2 S50 engines and 25 HS of fuel. In passing, I note you also have almost 35% of your ship devoted to propulsion. Your fuel:engine ratio is a nice simple 0.25, and you've sprung for 0.6 fuel conservation tech.
Moving up to a 0.4 propulsion ratio with 0.4 fuel:engine, you can get 3 S34 engines (biggest that fit evenly in the provided space) which would send your ships along at a nice 5610km/s with the same range, or (as I would prefer) 5100km/s with nearly 20bkm range. Alternatively, with the same propulsion budget but dropping your fuel:engine ratio to 0.2, you get 5400km/s at your chosen range, along with a significantly more fuel-friendly 3 S40 engines with 1.35 power modifier. (This would use 66.4% of the fuel.) All for a modest 19 more HS.
Where can you save the HS in your designs? It's up to you, but I'd:
- Strip some armour from your Achilles. Down to 5 is probably fine; I like to make missile and PD ships thin-skinned at ion, so I'd settle on 3. Can't kill what they can't catch.
- Too, drop the turreted laser. This is a PD ship with lasers to finish off cripples; you're dedicating too much to your secondary mission. That spinal will be fine, especially with the extra speed.
- Consider losing one of your PD BFCs; you're not going to effectively engage 3 salvos anyway.
- For Patroclus, drop the active sensor and restrict your MFC down to the range of the active sensor on the Achilles. They never go anywhere separately anyway, for fear of the former being killed by the dreaded Hector class.
- Ajax can lose some magazine depth. With 45 launchers, you have 10 full salvos. (Good job on the even number; that can be a pain.) Maybe go down to 8, and if you need staying power with such a short deployment time, include a collier in your tail.
That is not to say that your designs wouldn't be effective in combat. I'm sure they'd get the job done. But if you started off with the default 500 million population, the sheer fuel consumption for operating a whole group of such vessels would have to be a severe hard limit upon their actual operation. Edit: To clarify, I don't just mean that your ships, or even your tankers would easily run out of fuel. I mean that your Empire would run out of fuel.
It's true that military ships being too fuel-hungry is a big problem, especially if you play like I do where speed is king. But hopefully I've shown how to tighten that up a little, here. Too, population isn't your only source of fuel. Unless you're under serious pressure from outside, you have no real business getting a fully-fledged military up and running before you have harvesters chewing away at the local gas giants.