Repairs glitch
From Halopedia, the Halo wiki
The repairs glitch is a glitch that can happen in the twelfth Campaign level of Halo Wars. The glitch pushes players out through the invisible walls surrounding the UNSC Spirit of Fire.
Walkthrough[edit]
If you have Hawks, you can send them out of the wall with you. When you get to a certain distance, you will meet the Covenant destroyer. As Ensemble did not intend for the ship to be visible from this angle, only its plasma turrets can be seen. These batteries can be destroyed with Hawks.