[AR] Re: Dynamic stability in supersonic rockets
- From: Mike Caplinger <mc@xxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 16 Nov 2021 14:14:31 -0800
On 11/16/21 10:37 AM, William Claybaugh wrote:
If lateral acceleration is normal to the vehicle axis then it seems to
me that the curve in Drew’s data is exactly what I would expect for a
buildup of coning induced lateral acceleration leading to vehicle breakup.
I guess I'm not sure how coning is defined. What you say would be true
if the lateral accelerometer axis were always in the same orientation
relative to the spin axis, but is this what coning is?
At any rate, Plugger's flight certainly looks "wiggly" but I've had
failures like this that had no particular wiggle, at least as visible
from the ground. For what that's worth.
...I’d suggest that building the rocket so that it does not fail
structurally will show whether the coning is caused by the structural
failure or has some other underlying cause.
Good advice, but easier said than done, at least for me. :)
I've certainly always verified with RASAero II that my rockets have lots
of stability margin at velocity. I suspect there is something about
non-zero AoA and dynamic stability that puts more stress than expected
into the short section of airframe between the top of the motor and the
nose cone joint. Maybe that's related to poor spin balance, maybe not.
I've had it happen on lightweight rockets that simply didn't have enough
mass to be unbalanced very much (or so I thought.)
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