That's why you capture an asteroid... link at the end of the post. A million tons of rock is GREAT armor.

Traditional naval theory is that you can build a battery onshore 10x bigger than the one on a battleship. Things change when you are in space though. Missiles have to escape the gravity well. Lasers have to get through the atmosphere. Sure it's expensive to get up there, but if you have space superiority, you do have certain advantages.

Not with that attitude...