Simulating a Bohica’s Dead Ringer

So I finally figured out how to make an OpenRocket simulation of the Dead Ringer that may not be completely useless for flight simulation purposes.

OpenRocket file

OR can’t simulate this rocket as-is because it can’t handle drag stabilization or lack of fins, so it puts the CP up in the nose and says it’s completely unstable. You can override the CG and put it in front of the CP, but that seems kind of silly: the CG as calculated is presumably pretty accurate, while the CP is completely fictitious. But I’ve now learned about the trick of overriding the CP by adding a massless conical transition on the back of the rocket. I even made it vaguely flame colored:

Screen Shot 2013-11-06 at 1.57.46 PM


I adjusted the transition to put the CP in what seemed a reasonable place. Bohica said his 18 mm Dead Ringer was stable with 0.5 oz mass in the nose but unstable without; so is this model.

With that stabilization we can try some simulations. OR says this gets a whopping 64 feet off the ground on an A8-3. Draggy! The whole flight lasts only 6 seconds, and the recovery device (I put a chute in) deploys barely over 20 feet off the ground. For comparison, if you delete the rings (but keep the CO override) it sims to 183 feet.

In fact this is almost certainly too draggy. Bohica had a 13 mm Dead Ringer and he said it flew on a 1/2A. So OR is probably overestimating the drag.

Anyway, flights on a B6-2 and a C6-3 sim pretty well, with altitudes of 110 and 214 feet and deployment near apogee. We can probably regard these as worst case scenarios.



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