The 6DOF comment was NOT regarding Mars Direct. Never said it was. However, when I was at Pioneer we did a sizable number of wacky projects that DID require calculations requiring many degrees of freedom, from launch vehicle trajectory analysis (back when Pioneer meant Pioneer Rocketplane, before Zubrin got himself booted out) to air flows through ejector ramjets/scramjets to you name it. Many things in the real world are very, very complex and cannot be reasonably reduced to a single equation. But that doesn't stop some people from trying... therefore, sometimes you have to duck shrapnel.