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Anti-Missile Tutorial

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Bobby dies in the end

Hello kids!

Today you will learn how to build your first anti-missile-missile, or A-M-M. It's great fun, and you'll need it because, as you know, space is full of naughty aliens and stuff like that.

But instead of jumping right into the details of engine magic and technobabble, let's look at an example of what can happen out there. Perhaps your first encounter is less awful, but the example is not unrealistic.

A Bad Day

Let's say you've already designed your first warship, Bobby the Battlecruiser! Bobby weighs 3,500 tons (i.e. displaces 3,500 m³ of vacuum or something) and has some early-tech engines, sensors, missiles, some odds and ends, and he makes you very proud.

Now Bobby is flying through the dark Orionis system when he suddenly meets a gang of nasty space aliens. Punks, really. And the first thing Bobby sees on his sensors looks more or less like this:

---------o 7x Size 8 Missile 20,000 km/s (x4) 592,000km

Seven missiles coming Bobby's way! This isn't good. But wait... do you see the (x4)? It's actually four salvos of seven anti-ship missiles (ASM) each. Twenty-eight minions of death on afterburners. What can poor Bobby do? Run? Hide? Fight? Cleverly talk his way out of this mess?

Sorry, kids. Really. But there is nothing you can do about it. Bobby is going to die horribly, in about twenty seconds.

Don't cry. Actually, Bobby's death is a good thing. It teaches you how dangerous space can be, and that you shouldn't call a 3,500-ton boat a cruiser. And let's face it: In all likelihood Bobby - the first warship you have built - was a terribly mis-designed rustbucket anyway. Good thing he's gone. Your next attempt will be much better prepared. And that's where AMMs come in.

Elements of a defence system

Before we get to the missiles, we need to take a look at sensors, launchers and magazines and what they do because that's what a lot of people get wrong.

Any AMM missile defense is a system where all components need to be work together. It has five parts:

  • An Active Grav Search Sensor (ASS) with a Resolution of 1. That's a pure missile warning sensor. It's not much use for anything else, but your big high-resolution search sensors will see missiles only when they already scratch the paint of your expensive ship. In theory you need only one warning sensor and it can be on any ship. All you need is somebody, somewhere to spot the missiles with an Active Sensor (not Thermal or EM sensors). All your ships now know where the incoming missiles are, even those in different taskgroups. In practice you might want to put at least a small warning sensor on most warships, just in case.
  • A missile fire control (FC), also Resolution 1. Each ship firing AMMs needs at least one of those. The ASS looks out for trouble, then the FC guides your anti-missiles to their targets.
  • A bunch of Size-1 launchers. Why are AMMs almost always Size 1 missiles? Because they don't need much Bang! or range or fancy extras. They need to be fast, really fast, and the launchers need to be fast as well. Size-2 launchers take twice as long to reload as Size-1, Size-3 need three times etc. Early reloading tech means a Size-1 salvo every 30 seconds.
  • A Magazine. Each launcher can store one missile, that's why adding eight Size-1 launchers to your ship design gives you a magazine capacity of eight (note: Magazine Capacity is measured in Missile Size Points, not number of missiles. Adding four Size-6 launchers gives you a capacity of 24). Now there will rarely be only one salvo of 28 ASMs to defend against. There might be five or ten or even more, depending on how deep the enemy's magazines are. Another reason to make your AMMs as small as possible, and that's Size-1 (you can't build anything smaller). Having
  • A Missile. You guessed that one, right?

Building the components

Let's look at Bobby's Bad Day and then build some example components. What design values you actually get depends on your actual tech levels, but your first early-tech AMM system might look something like this. I don't claim it's perfect or even pretty good, but it'll give you an idea how things need to work together.

  • A warning sensor, size 5 Hull Spaces (HS), or 250 tons. It says "Maximum Range vs 50 ton object (or larger): 2,880,000 km" but that's irrelevant. 50-ton is a mega-missile you'll hardly ever see. But our sensor can spot the Size-8 missiles at 576,000km. Make it bigger if you like, but that's 200 tons already. It all adds up.
  • A fire control with at least the same range. The FC can only target things the warning sensor can see (note that it's good practice to give the FC a little more range than the warning sensor because the enemy ships might sport an ECM system that reduces your FC's range by 10% per tech level). Let's make it 2 HS, or 50 tons. It could target Size-8 missiles at 691,000km - if the warning sensor could see them, which it can't.
  • Now the launchers. You know why Size-1 AMMs are so popular. Let's say you have researched some reloading tech and you rate of fire (ROF) is one salvo per 15 seconds. Each launcher weighs 50 tons (reduced-size launchers save weight but reload much slower, which is bad for AMMs). But how many do you need? That's a good question. It depends on your hit chance per missile (and that depends mostly on speed difference between AMM and ASM), how many ASMs you need to destroy and how fast you can reload. As a rule of thumb, you might plan on launching two AMMs per ASM. Your mileage may and will vary, but at least it's a starting point for planning.

So let's look at what killed BC Bobby 001!

7x Size-8 Missile 20,000 km/s (x4) 532,000km

These things travel 100,000km per five-second-turn, and that's not even very fancy high-tech. And if Bobby is flying towards them at 3,000 km/s when he spots them, the distance shrinks by 115,000 km per turn* (Bobby didn't spot them at maximum sensor range because positions are calculated only every five seconds). Everybody, brace for missile impact in about 25 seconds! Lucky you, your reload time is 15 seconds, so you have time to shoot twice. Now let's see: you want to launch 56 AMMs in two salvos, that makes 28 launchers. Oh, and you'd need two fire controls controlling 14 launchers each. One FC can target only one enemy salvo per AMM launch, and there are four of them.

  • Next, the magazine. 28 Size-1 launchers already give you 28 capacity. Add a size-15 magazine for another 240, depending on your tech and whether you want extra armor. That makes 268 missiles, or enough to fire nine times. If you fire two AMM salvos at each incoming ASM salvo, you'd better hope the aliens run out of missiles before they can fire their fifth salvo. If not, it's bye-bye Bobby.

Total mass is now:

1x Warning sensor 250 tons
2x Fire Controls 100 tons
28x Launcher 1400 tons
1x Magazine 750 tons

A total of 2500 tons for the AMM system alone. That's why Bobby dies - you can't put all that stuff in a 3,500-ton hull, unless you leave out minor extras like engines or fuel.

  • Finally, the Missile itself. First, let's see what warhead, fuel and maneuver ratings you need to put in so you'll know what's left for engines. You'll need to enter small fractions of whole numbers.
    • Enough Warhead Strength to get Damage 1 (note that some space punks have armored massiles that take more than one damage point to kill, but don't worry about that now; it's rare and you can't waste missile mass on bigger warheads now).
    • 0.01 points of fuel should be OK. Missiles need very little of it and you can't use any extra range above than what your warning sensor and fire control have.
    • Agility of about 0.2
    • That might leave about 0.4-0.6 for the engine, so close the missile window and design an engine of that size now. It should have your maximum Power Modifier. Forget about fuel efficiency.
    • Have your scientists research the engine. Go back to missile design and enter the values above, then add one of your new engines. Fiddle with Agility until you arrive at a missile of exactly 1 MSP (not 1.001 MSP because that requires a Size-2 launcher already).
    • Your actual tech determines what that'll get you, but hopefully your new AMM ist faster than the ASMs you want to shoot down, which is not too likely with early tech. Look at the hit chances for a target moving at 10,000 km/s. Your chances to hit a more advanced ASM from our Bad-Day example (20,000 km/s) are half of that. Your first AMM design probably won't get anywhere near the 50% hit chance we assumed above (we fire two AMMs per ASM), and even then the occasional straggler might get through. A Size-8 ASM will probably cause about 10 Damage and punch a hole through three layers of armor.

So even if Bobby had all those 2,500 tons of early-tech equipment, he would still die. But patient investments in engine tech (essential), missile warheads and agility will give you an AMM zipping through space at 36,000 km/s.

Using AMMs

See Ship Combat on how to set up your weapons. Also see Point Defense.

Notes

Why would you want more than one Fire Control? In the example above, four salvos (indicating four enemy ships firing at once) come Bobby's way. But each FC can fire at only one target. And although the 28 ASMs are all in the same place, that's four different targets.

Can sensors on your AMMs help? At higher tech levels, perhaps. For the time being, don't bother. Missiles with Active Sensors can automatically pick a new target if their original target is destroyed before they get there, but the new target must already be in range of their sensors or they self-destruct anyway. Look at the sensor range (again: Resolution 1) you can cram into a Size-1 missile.

Shouldn't you ever build Size-2 AMMs? Sure, give it a try. You might have a slow-firing, long-range defensive "umbrella" and a short-range one.

How many AMMs should your Ordnance Factories build? Really, only enough to equip the ships you build. You'll probably develop new tech long before your empire runs out of missiles and end up scrapping 9,800 of your 10,000 Hail Mary Mark 1.

A word about running away from missiles: If Bobby had turned around immediately, the missiles would have closed in at only 85,000 km per turn. Sometimes that can give you an extra chance to get off another salvo of AMMs. That's where Task Force Training comes in - well-trained crews can execute commands faster.

Contributors

Zook