Star Wars: Empire at War Preview

Most planet invasions take two steps. The first is to crush any forces orbiting the target planet. This could mean anything from a few X-Wing fighters to a huge armada of warships, bombers, fighters and space stations. Most planets will indeed have a space station that will be more difficult the more upgraded it's become. Space battles take place on a flat plane (this isn't Homeworld) and therefore the designers have taken to planting asteroid fields and gas clouds in the space environment to make things more interesting. Large ships can't pass through asteroid fields without being damaged and the energy clouds can knock out shields or disable unit abilities.