I listen to tons of spacey music but I'll try to restrain myself... (ugh, apparently I can't post links so I gave Youtube search phrases)
Eve Online has a brilliant 6-hour ambient electronic soundtrack in OGG format. If you don't own the game you can often buy it for $5. The soundtrack alone is worth this even if you never play the game. (search Youtube for "EVE Online soundtrack"
French synth is ideal for exploration and mining. (search Youtube for "Jean Michel Jarre Oxygene" or "Moderne Mercenaire Solitaire")
Psytrance is great for combat (search Youtube for "Pleiadians Maia" or other artists like Growly Mad Scientists, Green Nuns of the Revolution, Salakavala)
Buttoning my lip here before I go on an epic ramble but I've got a zillion more recommendations if you're interested.