There is more information on about Building Defenses and using SpeedSim here.
This is a reprint of the post found here at the oGame Forums
There is a fair bit of debate over whether you should build defense or fleet and in what combo but if you are going to build a defense then this is what I have done.
Ignore missile launchers, cruisers get rapid fire to early and you need the metal to grow mines.
- Use missile launchers in the later defenses. Early on, cruisers can wipe them out easily. But once you hit the bigger fights, they are a cheap source of cannon fodder. 5 Missile Launchers per 1 small laser.
- Small Lasers become your cannon fodder (some ships get RF but they wont appear to early so it gives you a bit of time to get started)
- Build 1 Heavy Laser per 4 Small lasers. (Only bombers and death stars get RF so they become your anti RF midgame).
- Build 1 ion cannon per 12 Small lasers. (ion cannons have high shields which helps everything else survive)
- Build 1 Gauss Cannon per 30 small lasers (first big gun and useful vs cruisers and maybe low numbers of battleships, but will struggle vs destroyers)
- Build 1 Plasma Cannon per 100 small lasers (This is the weapon your going to rely on to fend off those war attacks where someone just wants to bash you rather than steal some cheap resources)
- Small shield after 20 Light lasers
- Large Shield after 100 small lasers
So by the time you hit 100 small lasers, you have:
- Small Shield
- Large Shield
- 25 Heavy Lasers
- 8 or 9 Ion Cannons
- 3 or 4 Gauss Cannons
- 1 Plasma Cannon
At this point, the odds of someone hitting the plasma cannon is 1:136 but it will be dishing out fatal damage steadily.
From what I can read no weapon will survive on its own in all situations. You need enough small stuff to make it unlikely that they will hit you big guns. Enough big guns to actually destroy their ships (rather than scratching all of them a little, but destroying none). Enough shields to prevent their damage from destroying you defenses to quickly. The combination will be different for everyone and will be affected by what you are facing.
Build them as well – when you consider interplanetary missiles a threat.
The whole point of a defense is to make it unprofitable for someone to attack. Low resources at home and enough defense to deter the attack. If you ever have to use it its probably not big enough. Silos 2 will give you 10 anti-ballistic missiles. I would think this is plenty for most of the game (except maybe later in a war. Anti-Ballistic Missiles are cheaper to build than Interplanetary ones.
A defense is a money sink. You need to keep adding to it as you produce more, but should never really need to use it. Its the attacks that look at you, say “to big/not worth it” and go elsewhere that you are really trying to catch. If you want to see what ratio you should use for mines vs defenses then read the article.
Another suggestion: If your going to use defenses then keep your resources low. Ship them away or spend them. It doesn’t really matter but dont leave large numbers lying around. It will just draw an attack that you cant defend against, and you will end up losing your defenses and your resources.
This does not take into account using fleets as defense. That is another topic for another day.
UPDATE: Added some advice on using Missile Launchers.