RockSim vs OpenRocket
- Thread starter Kruegon
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jmattingly13
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Are there any mass discrepancies or non-standard geometries involved?
I just created a thread on this topic last night https://www.rocketryforum.com/showt...lt-differences-between-OpenRocket-and-RockSim
If you read the responses, some more helpful than others, it looks like the more experienced guys are not surprised in the least to the point that some don't put too much weight on what the two simulators have to say as far as results.
If you read the responses, some more helpful than others, it looks like the more experienced guys are not surprised in the least to the point that some don't put too much weight on what the two simulators have to say as far as results.
Kruegon
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None. They sim out to the same dimensions. Same weight. Same everything. I'll be home in an hour. I can upload the rkt and ork files if you want a peek at them. Also might not hurt to get a second opinion on the build out.
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More information needed.
700 ft is what percentage of apogee? If it is 700 out of 7000, then don't worry about. That's normal.
Subsonic or supersonic?
Is the motor data the same? Not just "H128" or whatever. Is every thrust vs. time point the same?
etc.
Kruegon
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Subsonic. AeroTech I285R. 685 ft/s in RockSim, 654 ft/s in open Rocket. The exact same thrustcurve .eng file was loaded into both programs. I have made them as identical as the programs allow.
The rocket itself is exactly identical.
Apogee is 3439 ft in RockSim, 2762 ft in OpenRocket. 677 ft difference. That's almost exactly 20% less in OpenRocket than in RockSim.
So, I'm open to theories about the difference.
View attachment Estes #3217 Vagabond 3.0 54mm Upscale.rkt
View attachment Estes #3217 Vagabond 3.0 54mm Upscale.ork
Also check surface finishes....Rocksim defaults to polished, OpenRocket is more conservative.
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Probably the drag model, then.
This correlation/simulation stuff can drive you mad. Sometimes you have to say screw it and just go fly the damn rocket.
jmattingly13
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If you want to find out for sure, come on up to an MC2/HARA launch this summer in Manchester, TN, and stick an altimeter in it. It's only a few hours drive, the field can definitely handle either of those apogees, and, of course, rockets.
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