Tuesday, November 11, 2008

Dyna-Soar stability resolved

I figured out why my X-20 Dyna-Soar Titan was unstable. Actually, I knew why immediately - the CP/CG rlationship was out of whack. So, the real question was why I didn't get it right. When I modeled it in RockSim, I first added a set of 4 fins per the Nike-style fin can. When I realized it needed more fin area and installed the clear fins, I went back and added 2 more fins to the model. These were just added in addition to the original set. After all, that's what I did in the real world. But, in the real world, the smaller fins that are abutted to clear fins essentially do nothing. Not so in RockSim! RockSim considers both sets so the model was over optimistic. Time for just a bit of added nose weight.