Open Rocket Sims vs The Real world?

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Diggr

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I'm just getting back to LPR rockets after some 35 years of life screwing things up on the hobby front. I have a copy of OR and as I become more familiar with it I like it better and better. I also downloaded a copy of Rocksim, the free trial version, and while I liked that one as well it didn't strike me as offering enough more than OR to warrant dropping $125.00.

Now, I'm well aware that any sim short of the ones that NASA, et all use, will be only an approximation of real world. Have any of you experienced folks built rockets, simmed them in OR, and then compared the two data sets? If so, how well does the "theory" compare to the real world?

Thanks for any responses.

Diggr
 
I'm just getting back to LPR rockets after some 35 years of life screwing things up on the hobby front. I have a copy of OR and as I become more familiar with it I like it better and better. I also downloaded a copy of Rocksim, the free trial version, and while I liked that one as well it didn't strike me as offering enough more than OR to warrant dropping $125.00.

Now, I'm well aware that any sim short of the ones that NASA, et all use, will be only an approximation of real world. Have any of you experienced folks built rockets, simmed them in OR, and then compared the two data sets? If so, how well does the "theory" compare to the real world?

Thanks for any responses.

Diggr

They compare close enough, however the data given is only as good as what you put in. Exact weights and dimensions are a must for all components, also when setting up the sims make sure your locations sre accurate as well as launch rail lengths. Usually the sims are less than + or -10% difference between the sim and the data from my altimeters. Rocksim does pods and some other things that OR doesn't currently do. Another piece of free software that is worth getting is RasAeroII.
 
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I'm just getting back to LPR rockets after some 35 years of life screwing things up on the hobby front. I have a copy of OR and as I become more familiar with it I like it better and better. I also downloaded a copy of Rocksim, the free trial version, and while I liked that one as well it didn't strike me as offering enough more than OR to warrant dropping $125.00.

Now, I'm well aware that any sim short of the ones that NASA, et all use, will be only an approximation of real world. Have any of you experienced folks built rockets, simmed them in OR, and then compared the two data sets? If so, how well does the "theory" compare to the real world?

Thanks for any responses.

Diggr

I've always had very good correlation as well.

Additional "factors" include selecting the proper finish on the rocket, accuracy of the shape of the fin leading/trailing edges (is it REALLY airfoiled, or just kinda...), and manufacturing tolerance of AP motors can also be a big factor.
 
Trying simming in some different wind conditions, as well, unless you have a really good idea of what they will be on the day you launch.
 
Gentlemen,

You just made my day. :) I'm just about 70 so I've been around computers long enough to understand the whole concept of "Garbage In - Garbage Out" and how quickly one can put themselves in the weeds if you don't believe! I've got three kits in build at the moment and a long rest of the winter ahead. My goal is/was to model them as accurately as possible, as built, and then collect some data for comparison. It's nice to know that the simms are better than "Yeah, it will get off the ground, probably without killing you". :) So now I can move on, reasonably confident that I'm not blowing sunshne up my own ... Thanks guys.

Diggr
 
Just want to chime in here and reiterate: watch component weights (use the real ones!), watch finishes and fin airfoiling, and in general, unless you fly "naked" there will be a mass increment for paint. If all those are in the simulation (along with getting the RIGHT motor data) the results can be very close to measured data.
 
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