Astro mission[U3]

Oh no! Astro surfer McDummy in danger! Couple of asteroids flying on him! Oh no! This is because evil pirate ErrBotus got asteroid cannon!

Commander, it's your duty to defend him. We giving you newest star fortress with missile launcher equipped. But they aren't homing. Your mission is to defend astro surfer from asteroids.
These asteroids are filled with nexus17, unique power mineral. If you gather at least 20 of nexus17 tons, we will be able to shoot that pirate with our laser cannon. End transmission.

Controls: f to shoot(automated launcher, hold it). Slider to aim.
You have only one missile. But! Your base can make new for cost of 50 points of score.
Your target is to destroy pirate and gather as many resources(score) as you can(every asteroid contains near 20 tons of nexus17).
Post here your highscores, comment,suggest.
Editing close during contest.