I believe if you rotate the ship quickly while firing it will create a death spiral destroying asteroids and the alien ship.
LOL
To kill the rogue spaceship(I am assuming it is probably the Argelians) you have to cruise at light speed around the entire universe and as soon as you reenter you shoot in the general direction.
The Argelians aren't the most intelligent beings. They will drive the ship right into the blast. As a side note. That's 100 points.