Before you go in to the military base make sure you have lots of mines
Once you get to the hanger go to where the big door is, this is where the tank droid comes out. Place 5 mines in a half circle around the door. I used average sonic mines. The place another mine right in front of the door. When you activate the reactor, the tank droid comes out and walks right into the mines. After I did that, The droid had literaly no health left. Hope this helps.