During the later part of the game just after you get the 3600 chip for SAM, you will have to fly in the space craft called the Inferno GX, now from this point you will have fly and ram in to an enemy in order to kill it, very simple just head straight towards it and knock it out the way and achievement unlocked. There are more than enough chances to get this so don't hold your breath too much.
Please refer to my video for more information.... and most importantly THUMB UP