When a shuttle lands, it cant attack the ground units, but they can attack it, Vehicles can attack any ship that lands, the damage that there main cannon does is the same, there is no change.
When a bomber is in orbit, ever 4 turns in land combat, it can attack, but only 1 every 4 turns, the
Damage: 100 (150 Land) is what you follow, you follow whats in the (Land) For bombing land targets.
When you have a building, such as an Ion Cannon, it can attack only space units though, but it can help in battle, like if a person has bombers in orbit, ifyou shoot an ion cannon at it, it cant attack for another 4 turns, and so on.