I have very little experience using either of these programs so I am looking for someone who would be willing to spend time creating a file I can read using Open Rocket. I am building a high power rocket for someone that is completely different and I’m not sure if either of these programs can model such a rocket. The attached image is the model I am almost done building. This is a 60” tall model and will be powered by a 38mm J motor. Its weight will be around 12 lbs. RTF. It would be great if it didn’t need any fins but I’m pretty sure I will need to add some fins; I’m planning on adding 5 removable fins. I could simply throw a couple pounds of lead in the nose and add big fins to the rear but it would be kind of nice if I had a better idea where the model should balance. The other thing I could do is make a smaller scale model but I’m running out of time before I need to deliver this model.
I will supply complete dimensions to the person who is willing to help me out on this.

Thanks

John Boren

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John,

There may be a Rocksim expert here who is willing to take this on (it's not me) but that's beyond the capabilities of Open Rocket as it exists now I think.

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Bernard Cawley
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BEC is right about the limitations of OpenRocket. It's almost outside the range of RockSim, too, with those odd-angle appendages at the top. I'd be happy to attempt a rough draft in RockSim, though. It's always worth a challenge.

60" tall, about 12 pounds loaded. 38mm "J" engine, with possible removable fins...

Is the length critical? Or can it be adjusted to improve appearance/performance?

I'm game for a challenge!

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Craig McGraw

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The model is pretty much built. I just need to know where to balance it and how much fin area it needs to be stable.

Does Rocksim have the ability to put cone shaped objects on the side of a center body. The 8 motors on top could be simple tubes with a blunt ends on them. Evan all the changes in diameters could be reduced to help making it easier to model.


John Boren

Sadly, no. RockSim cannot place tubes (or anything else, FTM) at odd angles to the centerline. I can, however, simulate these with "fins", or blocks of wood, cut to fit the profile and given a thickness to match the diameter. I can adjust the mass of the piece to that of the actual subassembly to get the balance right.

Subassemblies and Pods are a unique feature of RS, and it gives the program a lot of power. But it's not a "cure-all". I'm hoping Apogee will work something into a future release to allow such angled centerlines.

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Craig McGraw

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SAM 0044
AMA 352635

AutoCAD has no limitations and will even give you a CP for individual parts which can then be used to compute the overall CP, which can then be used in a facsimile in RockSim to compute performance. I would like to help, but my computer with AutoCad was lost, so if you want to assist with the price $4000 or so) for a new copy of Auto Cad, I'm sure I could assist with any and all calculations.

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Bernard J. Herman Ohio RLS

Starport Sagitta Rockets
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We're looking for a few good Catos, please tell us about any you may have had. Survey of Anecdotal Malfunctioning Engines or S.A.M.E.

A reasonably close approximation of the aerodynamic profile of this kind of design can be made with either program if you treat the appendages as fins. Model the fins thicker than normal fins, bu they don't have to be as thick as the appendages. The shape should match the profile of the appendage. You'll have to manually adjust the weight of the "fins" to match the appendages.

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Peter Olivola
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Craig has creating a file for me that appears to be doing the job really great. Thanks Craig.


The more I play with it running flght simulations with fins, without fins, with an added cone skirt in the rear taking the place of the fins, it's looking more and more like I may be better off not trying to add fins or a skirt to the rear of the model as long as I get the CG in the right spot.


John Boren

Since I asked and was given help by posting here I thought I would share a photo of the build. Thats a 2-liter pop bottle in the photo for size reference.


John Boren

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The rocket has an anime-spaceship look to it.

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