July 17, 2020

Aurora - Advanced Missile Warfare

Since I wrote the main tutorial series on missile warfare, I've continued to experiment with the options offered by C#, and have made a couple of discoveries that bear further examination.

The first has to do with the way fire controls allocate weapons in missile defense. In VB6, each FC would engage one and only one target, so I made sure that each missile defense turret had its own FC. This has changed in C#, so that now any weapons (or turrets) not used against one target will engage the next. This makes it a lot harder for an enemy to throw small salvoes at you and overwhelm your defenses that way. Harder, but not impossible. In a couple of cases, I've attempted to close with AMM ships, and they've thrown, say, 50 size 1 missiles at me in salvos of 5. My standard beam defense system in that game was a 2x5 gauss turret, and the hit rate was usually 90% or more. The problem was that each turret could really only take out 5 missiles with 10 shots, and often less if other systems took out a few in a salvo before the turret began to engage.

The obvious way to deal with this is to have more and smaller turrets, each of which (ideally) would kill one missile, completely eliminating overkill. So I switched from twin 6 HS gauss turrets to quad .5 HS gauss turrets. This allowed me to take advantage of several effects. First and most obviously, I have more turrets in the same space (about 6 times as many), and can split them up more effectively. Each of the new turrets fires 20 shots, and the hit rate is 8% of that of a full-size turret with the same FC, so I can expect each one to kill 1.5 or so incoming missiles. This minimizes overkill. Second, quad turrets have less tracking gear as a percentage of size than full-size gauss turrets, giving me a slight gain in efficiency. Third, it's not uncommon for the hit percentage of a gauss turret with a good crew and good FC to pass 100%, and the extra kills are picked up by the smaller turret instead of being wasted.

I was quite happy with this approach, right up until I started to play with missile ECM. I had been fighting a spoiler race, and had found that I was usually getting about 6 missiles (one salvo) from a batch of 72 through their defenses. I got an engine upgrade, and tried two types of missiles. Both had the same warheads, and one attempted to penetrate defenses with speed, the other with ECM. On the first salvo of the fast missiles, I got 20 through the defenses, a notable improvement over the earlier missiles, but nothing amazing. Then I tried the ECM missiles, and got all 72 through. I was momentarily stunned, but then it all made sense.

The issue ultimately comes down to the way that ECM interacts with cases where you have low hit probabilities. ECM is a flat penalty to hit, with each point of ECM not countered by ECCM reducing the chance to hit by 10%. So a full-size gauss cannon with a 90% hit chance will now have an 80% hit chance with one point of ECM, a half-size cannon will drop from 45% to 35%, and a minimum-size cannon will drop from 7.2% to 0. A constant to-hit penalty hits any defense based on low hit percentages and volume much harder than a system based on higher hit probabilities. My use of .5 HS gauss turrets is the epitome of this system, and they would be completely useless against any missile that has as much as a single point of net ECM. Other mass-based systems such as railgun batteries will also suffer badly, as will low-tech opponents more generally. In my test, the spoiler race had ECCM 2 vs my ECM 5 and my missiles were traveling at 2.5x the weapon tracking speed, so the to-hit chance was essentially zero after ECM.

This isn't to say that missile ECM is all-powerful. If the opponent has ECCM equal to the ECM level, it's worse than useless because it takes up space and increases the cost of the missile significantly. But an expensive missile that hits is better than a cheap missile that gets shot down. On the whole, it's a serious blow to railgun defenses, and a significant boost to anyone facing a lower-tech opponent.

My current plan going forward is to split the difference and fit my ships with 3 HS twin gauss turrets. This doubles my salvo-handling capacity relative to 6 HS gauss cannons, while also giving enough hit margin to function in an environment with a reasonably high level of ECM.


  1. July 18, 2020echo said...

    I'm struggling with this too, after going from Gauss rof 3 to 5. 50% size quads with 20 shots are almost always going to be overkill with a ~60% tactical/crew to-hit bonus.
    Ultimately I figured that wasteful overkill against weak enemies with slow, no-net-ecm missiles is more acceptable than underkill against a dangerous enemy.

    And yeah, the real loser is the railgun PPV station, but it'll be fine as long as no one tells the civilians.

    I'm currently dealing with an enemy that built dozens of AMM stations on his planet after I destroyed his fleet.
    Waves of 500 70kkms missiles made me retreat and tech up shields and Gauss, because shield-tanking on the edge of range seems like the only cost-effective answer to that.

    Finally, since putting eccm on AMMs is cost-prohibitive, do you think ECM has made them less effective at high tech levels?

  2. July 18, 2020bean said...

    It will make them somewhat less effective, but the straight to-hit penalty probably isn't as big of a deal if you've got good AMMs. Just push accuracy as high as you can and hope that they don't have that many more levels of ECM. One other alternative I've considered is building bigger AMM launchers (whatever size you can get the same ROF as your Size 1s) to give the capability for more effective AMMs if needed, even if you normally just use size 1 AMMs.

  3. July 21, 2020echo said...

    I just found out that for PD the multiplier bonuses (tactical, crew skill, etc) happen after the ECM deduction. It's the opposite for missiles for some reason...
    This makes low base accuracy even worse than I thought.

    BTW, you said the enemy had eccm2, but what was your ecm level?

  4. July 21, 2020bean said...

    There are definitely bits of Aurora that Steve slapped together and then never really messed with again, and I think EW is one of them. It's not first on my list of things I'd fix if I was king (the lack of a crew rotation system tops that list) but it does make things worse.

    My ECM was 5, which I thought I'd said, but I guess I forgot. It's been edited in.

  5. July 25, 2020Steve Walmsley said...

    I've been planning to overhaul electronic warfare for about 10 years and never quite seem to get around to it : )

    Once things have calmed down with C# and the focus is no longer bug-fixing, EW will be high on the list.

  6. July 25, 2020bean said...

    Woah! Steve has visited. I'm rather surprised you found us here, as I don't think any of this has been mentioned on the Aurora forums.

    I certainly look forward to the overhaul, and hope it wouldn't be as binary as it is now. Currently, an equal-generation ECCM system is a perfect counter for an ECM system, which seems kind of strange.

  7. July 25, 2020Steve Walmsley said...

    Yes, I will try to create something a little more involved when I do revisit EW.

    I came across your site by accident, but found all the content really interesting. I'm a naval history geek so what's not to like : )

  8. July 25, 2020bean said...

    I'm delighted to have you here. I was just extremely surprised to see you pop up. Welcome, and I hope you get a tenth as much enjoyment out of my hobby as I've gotten out of yours.

  9. August 05, 2020echo said...

    somebody got the (beam) accuracy formula, and it's very interesting.

    ( min( 1, tracking/(target speed)*(1+tracking bonus) ) * (PD range penalty) - ECM ) * (CIC bonus) * (crew bonus) * (1/2 of commanding officer's tactical bonus) * (gauss size penalty)

    Gauss doesn't seem to suffer as much from ecm as we thought. Perhaps their tracking or base accuracy was very low?

  10. August 05, 2020bean said...

    In the particular case where I discovered this, the missiles were something like 2.5x the enemy's tracking speed, so maximum hit chance was 0.4 anyway. If the range penalties are 0.75, then the hit chance after that is 0.3, and the ECM takes care of all of it. (Actually, I think it was closer to 3x than 2.5x of tracking speed, in which case it solves the problem entirely.)

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