.......:::::__FREE BOOM BOOM!__:::::.......
All of this is REAL! I don't care if you say it is or not, but this is real and GREAT! (HELPFUL)
In Delta Halo level, go to the fortress thing. On the top level (go up (only up) all the ramps that you can find) go to where there is or used to be a plasma turret and a sniper. There should be 1 covenant beam rifle at 100 energy. (This is crap compared to what's coming.)
Go to stand on (or beside) the destroyed turret. Stand there on the ledge facing the big cliff (that you didn't miss when you landed) and turn a perfect (90 degrees) right. There should be like a little ledge sticking out from the roof of the ruin. Jump on to it. Turn to face the ruin from which the ladge was sticking out on. Jump up. Turn right and you should see a ramp. Go up (who saw that coming?). You will see a body and a **.... drum roll... ... ... ...** FREE BOOM BOOM! (Rocket Launcher.)
This can be done before the phantoms come. There is also a little place to hide so is a great place to snipe from. You can blow off the phantom's guns, and kill them EASILY!