Okay this has been bugging me for a while and I apologize for the vagueness of what I am about to describe..
I can't entirely remember what I played this game on, something is telling me it was PC as it seams a bit too control intensive for original Xbox. The game consists of vast landscapes and goals you must achieve. You are in this form of futuristic spaceship/hovership, it doesn't actually fly it hovers. You have a heads up display that feeds you all your info, i don't believe you can see outside the ship. Anyway you can construct bases at certain designated locations, you can construct buildings to build units which you can send in to battle and you can construct defenses for your base. One of the things i specifically remember is a defense turret designed to stop missile attacks, it was called the 'Patriot' turret, had a strange round-ish front to it, like a gattling gun. There were two main factions, one looked human-based due to ship/unit designs, the other quite alien..I recall use of a lot of black and red for the alien faction.
Hope somebody remembers this as it's driving me crazy and the only thing i remember is the damn turret! Any help is appreciated

this is circa early 2000's.