Some things need to be fixed.
First off, you have a pretty decent game here. There were a few things that I found to be a little annoying though.
One of the things was that the pieces of space rock are defined as a square, you don't need to hit into the rock part, you just need to hit on the edge of the defined image. Second it is tough when you beat a level to not die. Your momentum carried over from level to level so you will almost always die at the beginning on the next level. A simple way to fix this would be to make a simple "Good Job, do you wish to continue?" screen so that you can reset and have time to prepare for the next level.
Overall you have a pretty decent flash game. Keep up the good work and hopefully you will be able to improve this one. I rated it a 3/5 for now.