Welcome back to my Aurora Tutorial. We're currently discussing combat, specifically warship design. Last time, I covered missile defense with beam weapons, but now it's time to shift to the system I usually base my defenses around: anti-missile missiles (AMMs). AMMs have benefits and drawbacks relative to beam defenses. On one hand, I've generally found them to perform better than beams and to be more effective, particularly in the face of a massed attack. They're also much easier to upgrade, as you can just swap in a new missile with improved performance. On the other hand, AMMs can get expensive, and the ships firing them have limited ammo capacity. If they run through their magazines before the enemy does, you're dead.
So what is an AMM? Like beam defense, AMM defense is a numbers game. You need the smallest feasible missile, fired at the highest possible rate, so the obvious result is a size-1 missile1 with a strength 1 warhead,2 optimized for the highest hit probability possible and with sufficient range to match the sensor/fire control combination you have planned. As such, you should probably design the electronics first. Missile fire controls are built in the same tab as active sensors, and have the same range characteristics. On average, a typical MFC has about the same range as a search sensor 3 times its size. I usually try for a size 3-4 sensor, and an MFC that either matches it in range or is a little bit better. I do this because I expect later missile defense ships to have better sensors, and a slightly oversized MFC lets the older ship take advantage of the extra range. So going back to the AMMs, a missile's hit probability is equal to (missile speed*maneuverability*0.1)/target speed. Maneuverability is based on how much space you've put into agility3 so you need to find a balance between spending space on the engine and spending it on agility.
Fortunately, someone has created software to automate this process, which can be found here, sparing you the need to mess around with a graphing calculator or build your own spreadsheet. Just plug in your tech levels, a size 1 warhead and the desired range4 and tell it to maximize accuracy. That's your standard AMM.
To use it, you need a ship. You already have the sensors and FC. Next up, we need launchers. A missile launcher has a rated size, and can fire any missile of that size or smaller. A typical launcher using base tech can fire a missile whose size in MSP is equal to its own size in HS, although there are options which increase reload time and drop the size of the launcher.5 The bigger the launcher, the slower it fires,6 so it's probably best to go with size 1 launchers. You may want to turn down the reload tech because the launch intervals must be some multiple of the 5-second increments. So if your maximum tech is 3-5, you'll get a 10-second interval, and the cheapest of those is with reload rate 3. You'll also need magazines. These are researched on the magazine screen, and I tend to just research a single size-1 magazine and use a bunch of them. Theoretically, larger ones can be slightly more efficient at higher tech levels, but I don't find it to be worthwhile.
Putting these together into a ship is relatively simple. You just need a search sensor, several fire controls (redundancy!), a bunch of missile launchers and as many magazines as you can fit aboard. Missile fire controls can only engage one target an increment, so if you have too many launchers per FC, you can end up with launchers sitting idle. How big of a problem this is depends on the ROF of the launchers, and how you set up your fire controls. If the incoming missiles are 6 to a salvo and you have 12 ROF 10 sec launchers, then you're fine. If you're firing 1v1,7 half will launch every 5 seconds, while 2v1 will fire all of them every 10 seconds. Things get more complicated with odd-size salvoes, or if you need to reengage, but the game does a pretty good job of figuring it out for you. One thing to note is that, as best I can tell, the C# version prioritizes the biggest salvo in range for targeting, instead of the closest. In general, I'd recommend going with between 4 and 8 launchers per FC, maybe more if you've got a low ROF.
The only other thing to pay attention to is magazine space. It's not too difficult to get enough launchers for all but the largest attacks, but a ship with empty magazines is useless. At a bare minimum, you need 1 HS of magazine for each launcher, but that gives a maximum of 20 shots/launcher. Particularly as you get faster-firing launchers, that's not really adequate, and you'll want to go for significantly larger magazines.
So now that we know how to use missiles to defend against missiles, it's time to use this knowledge to figure out how best to frustrate the enemy's defenses. Next time, we'll finally get to offensive missiles, and how best to use them.
1 The size of missiles is measured in MSP, which are 2.5 tons each. Ships are measured in HS, which are 50 tons each, so there's 20 MSP per HS. The game will let you build missiles and launchers with fractional sizes above 1, but not below 1. ⇑
2 All missiles are destroyed by even 1 point of damage. This didn't used to be true in VB6, but armored missiles were rare enough it was still worth taking the chance. ⇑
3 The actual formula for maneuverability is 10+(missile agility/missile size). ⇑
4 Unfortunately, C# Aurora doesn't have the feature in VB6 where it let you set the range your fire controls will engage at, so it's best to make sure the missile has the range to match the FC, or the fire control won't automatically use it until the incoming missile enters the AMM's range. For AMMs, the number to look at isn't the FC's top-end range, but the range it can detect a size-6 missile at. ⇑
5 These can be useful for offensive missiles (which I'll discuss later), but the whole point of AMMs is that you get multiple chances to fire at the incoming missiles, so they should be avoided for defensive missiles. ⇑
6 Fortunately, the model has been changed since VB6, where as size went up by N, so did reload interval, giving a harsh penalty to bigger launchers. The scaling is now with the square root of N, a much more reasonable value. ⇑
7 1 AMM per active incoming missile. The game will let you select how many AMMs you want to fire at each incoming missile on the ship combat tab of the Naval Organizations window. The correct one to select depends on your expected hit rate, how many launchers you have, and the chances of getting to reengage. Personally, I usually find 1v1 works pretty well, particularly if you have some beam defenses to catch the leakers, and it's the cheapest in terms of ammo. Yes, it will fire a second missile if the first one misses. ⇑
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This was officially the point where I had to take an aspirin and a nice sit down. Think it's time to crack open the online calculators and play around a bit.