I have a tall/thin rocket with a fineness (aka aspect ratio or length to diameter ratio) of ~26 (80” long 3.1” diameter). As currently configured, it has a stability margin of 3.7/14.6% in OpenRocket.
I am trying to answer the age-old question is if this rocket is over-stable. The only “rule of thumb” I have heard for tall/thin rockets is 8%-18%. At 14.6%, I am roughly at the center of the range but I don’t know if that means anything. I’m simulating at various wind speeds looking at angle of attack, side profiles, and lateral orientations but am having a hard time understanding what it all means.
As an aside, I see that Rocksim has a flight profile function that claims to show what the flight looks like but I don’t trust Rocksim as it seriously overstates stability if using straight Barroman and even more so when using its own CP equations. In another case, for example, OpenRocket shows CP at 40.8” and RockSim (Barroman) is 42.1 and RockSim (Rocksim method) shows 44.5. Weight and CG come out the same in RockSim and OpenRocket, so I believe the models are correct in each program.
So how do I use OpenRocket to check the results of specific stability, i.e. answer the question if the rocket is over-stable (at various wind speeds)?
I am trying to answer the age-old question is if this rocket is over-stable. The only “rule of thumb” I have heard for tall/thin rockets is 8%-18%. At 14.6%, I am roughly at the center of the range but I don’t know if that means anything. I’m simulating at various wind speeds looking at angle of attack, side profiles, and lateral orientations but am having a hard time understanding what it all means.
As an aside, I see that Rocksim has a flight profile function that claims to show what the flight looks like but I don’t trust Rocksim as it seriously overstates stability if using straight Barroman and even more so when using its own CP equations. In another case, for example, OpenRocket shows CP at 40.8” and RockSim (Barroman) is 42.1 and RockSim (Rocksim method) shows 44.5. Weight and CG come out the same in RockSim and OpenRocket, so I believe the models are correct in each program.
So how do I use OpenRocket to check the results of specific stability, i.e. answer the question if the rocket is over-stable (at various wind speeds)?
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