Using OpenRocket

Discussions about rockets, construction materials, adhesives, nozzles, nosecones and fin design.
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sebswift
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Joined: Tue Nov 01, 2016 6:57 am

Using OpenRocket

Post by sebswift »

Hey,

Wondering if anyone here has had good success using OpenRocket to model CM/CP work with water rockets?

I have been playing around with it and just wondered if anyone has already figured out some good tips and tricks for the modeling. I was going to model some water rockets by getting the outer shape correct (for CP) and then modeling all mass with overrides, component by component, with accurate center of mass positions. The control variable is going to be the fin design to adjust the CP in relation to CM.

For fins, I am just approximating the density by weighting a piece of 100mm x 100mm x 4mm piece of Corriflute to get the approximate density by volume (which is what I think OpenRocket uses for the fin CG points). For the fin glue, I weighed a typical test fillet to get a weight by linear mm then use a mass object at the axis of the rocket in line with fins.

For the water, I am adding mass volumes anchored at the bottom of the appropriate chambers with density of 1g/cm3 to match the water size. I expand the length of the mass to fit the actual amount of water and the diameter fits the inner diameter of the cylinder.

Tape weight is part of the cylinders since it does not change center of mass on a cylinder by cylinder basis.

Couplings are modeled as internal masses, centered between the bottles.

I use rail buttons so those are simulated with solid (filled in) launch lugs with appropriate mass and position on outer edge of rocket.

Nozzles are also mass objects. Payloads are simple mass objects.

I'm not finished so I don't have any results to share. Hoping for some tips or confirmation of the approach.

Cheers!
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rstaff3
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Re: Using OpenRocket

Post by rstaff3 »

It has been a while since I looked at it, but this Apogee article addresses water rockets in RockSim. https://www.apogeerockets.com/education ... ter219.pdf

Different software, but the concepts should translate.
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sebswift
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Joined: Tue Nov 01, 2016 6:57 am

Re: Using OpenRocket

Post by sebswift »

Thanks. Will check that article out!