Not to add fuel to this silly discussion, but it seems any ship of sufficient speed (a Federation starship perhaps?) could just keep circling the Death Star, staying on the ''blind side'' away from the ''big gun'' and pound away with phasers, torpedoes etc. I just don't see the Death Star rotating anywhere near full impulse or sublight, not to mention light speed -- to keep a bead on anything long enough to fire at it.
Really bad defensive design that old Death Star had. Who the heck needs to waste time hitting the exhaust port?
''Destroy all you want. We'll build more.'' (the Death Star marketing tag-line).