There's 4 chapters left, but Chapter 13 is really short and 14 is just the credits :V
Aw, that's a shame. Then again, I still have Episode 1 and Episode 2... :3
Woah wait a minute, how on earth did you get that far without knowing that? The gunship usually shoots down your rockets instantly unless you go in some crazy pattern.
Well, shoot so that the rocket, if it actually went a straight line, will hit the ship if it continues it's movement like that. It will probably miss anyways, but I think I made at least one or two hits that way.
If you are under fire, dive for cover. If you are safe, look for where the dropship might be. Continue this until the rocket explodes, no mater where this will be. This will cause the rocket to move around the sky in an erratic pattern like a sattelite who downed a crate of Jack Daniel's. The majority of the rockets will miss or be shot down, but eventually some will hit.
While it will take way too long, you will take only little damage (unless the rocket hits the ground next to you, but that's what medkits are for) and you have infinite ammo anyways. BV