There is one really big tip I don't think I've read anywhere....
That is, once you get your score to pass the level..go somewhere safe and don't shoot anything else unless you have to. It doesn't do a bit of good if you get 3000 on the first level or 20000...it's all the same and all you are doing is risking damage
The bigest problem with blast in space is that the first 10 levels are utterly boring and way too easy and the last 3 are way too hard.