OR stability calculations?

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valley

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Hi, bit of an odd question perhaps: can Open Rocket be used to calculate the stability of a rocket-like shape in free fall? Does the Barrowman equation, which I assume it uses, still apply?

To explain- I'm involved in the design of a free-fall ice-drift probe, which whilst NOT a rocket, is somewhat rocket-shaped, and I need to assess its stability in the free fall phase prior to parachute deployment.

I realise OR wasn't really designed for this! Is there a better (free) software tool for the job?

Any thoughts welcome :)

Thanks in advance.

V.
 
I can't speak to OR, or any other program's ability to calculate stability, but you can always perform a swing test. You attach a line to the CG, then spin it over your head and see if it points into the direction of the swing, if it does, it's stable. If it cartwheels, it isn't, and you can add weight to the nose to try to correct it.

Here's a little primer on the subject.
 
Thanks K'Tesh. I guess the swing test is an option :) As the 'rocket' is about 6ft long, I was hoping to find a way to do this by simulation. But hey, i guess sometimes the low-tech approach is the way to go... Whatever gets the job done!

V.
 
Sure OR can tell you the position of the CP. That should be about all you need. Barrowman's equations apply provided you are operating within its assumptions - low angle of attack, generally long tubular shape with some transitions and fins, fewer than 8 fins, etc.

If you're willing to crack into some java code, OR could simulate the free fall as well.

Kevin
 
One rocket of mine, OR seemed to predict accurately that it would come down sideways. However it also showed it drifting sidewise a LOT even with no wind, like some glider. Adding a few ounces of nose weight caused it to show less much drift and higher ground hit velocity. Some combinations looked like a roller coaster. This was before adding chute of course. It may have presumed the nose cone popping at apogee vs. in practice it started coming down sidewise before that, after tailstand if straight up.

So, MAYBE ;)
 
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