Rocksim 9 has tools built-in to model strap-on boosters. If you have Rocksim 7 or 8, there are ways to trick it into simulating them. Allen -------------------------------------------------------------------- Allen H. Farrington 818-653-2284 web: http://www.allenfarrington.org On Aug 10, 2011, at 11:29 AM, Kurt Gugisberg wrote: > Richard, > > The strap-ons will add some drag stability (base drag) as well as an area > equivalent to fins or a larger airframe area. Knowing just how to factor > that in is the tricky part. I think you can fudge it into rocsim somehow. > > Kurt > -----Original Message----- > From: Richard Dierking > Sent: Aug 10, 2011 10:34 AM > To: roc-chat@xxxxxxxxxxxxx > Subject: [roc-chat] Stability of a rocket with strap-on boosters > > I'm considering the size and shape of the 3 fins for my Delta II 7925-10L. > It's a 4" core transition to 5" on top with 9 strap-ons, each approximately > 1.5" dia (BT-60 tube). total height is 65". I don't want it to be a > high-velocity rocket and I'll be using a J135 for the core, six F-30's > strap-ons 0.5 sec after launch, shed those, then airstart three G's strap-ons > then shed the last three strap-ons. > > For the 3 fins, I'm using 3/16" thick abrasion resistant polycarbonate that > by my estimate has a stiffness similar to 1/8" birch. The fins are > through-the-wall and fiberglassed to the 54mm engine mount. I'm thinking to > configure the fins as clipped deltas to avoid busting a tip during landing. > Since the rocket has 9 strap-ons, seems to me this would add stability during > launch (like tube fins). Am I wrong thinking this? I would like to keep the > fins on the small size. > > Please advise and thank you, > Richard Dierking > > -- ROC-Chat mailing list roc-chat@xxxxxxxxxxxxx > //www.freelists.org/list/roc-chat -- ROC-Chat mailing list roc-chat@xxxxxxxxxxxxx //www.freelists.org/list/roc-chat