shred sim

I have been tinkering with Open Rocket recently and it has been quite useful. However, it does not do any calculation of material or construction quality possibilities, right? I have not seen any way for it to indicate that, if I gave a balsa and TP roll enough force to hit mach three, that it would disintegrate.

Right now I am looking at a PML Mystic, 38 inch by 3 inch airframe, and trying to figure out what it would do with the higher end level two motors. PML catalog says it is designed for E-H impulse, and those fins look like they might rip right off with a big J motor! What do you suppose most manufacturers have in mind when they claim to be designing for an impulse range? Altitude, trackability, stability, strength, or what? I would imagine and hope for some combination, but who knows.

There is not a hobby level simulation program that does structural analysis. You need a lot more money for that.




Mark Koelsch
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There are some open source simulation programs that can do some structural analysis for you. But they are on a completely different level of complexity to use compared to open rocket. You need to have a pretty good understanding of the dynamics to properly simulate, otherwise you will just get garbage results. If your are a mechanical engineer it shouldn't be too bad to figure out. If not you will just have more studying to do.

There's flutter velocity estimators out there. Im sure that and a bit of engineering would get you close. Although a flight stress simulation software integrated with altitude simulation software would be great, it's no small feat. Of course you would also need quite a bit of plate theory for composites. I would kill for a simulation program that incorporated everything involved in flight. Maybe an openrocket add on?

Alex

Aksrockets said:

I would kill for a simulation program that incorporated everything involved in flight. Maybe an openrocket add on?

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You know, open rocket is open source. Download the source files and lets see it happen.

Isn't the PML mystic built with quantum tube? I understand QT doesn't have sufficient rigidity for mach+ flights.

Here is a fin flutter simulator: https://www.aerorocket.com/finsim.html

PML faq on airframe material: https://publicmissiles.com/pml/home/images/PMLAirframesFAQ.pdf

Xrain said:

You know, open rocket is open source. Download the source files and lets see it happen.

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+1 to that.

The "free" part of open source also means "freedom." You have the freedom to use the source code as you please and create new things with it. If you want it, you can make it.

so this is kind of an old post but man it would be cool if open rocket incorporated fin flutter simulations! they already have the flight data, the fin design, fin material, seems like a natural fit to also do flutter calculations...

Agreed

amell said:

Isn't the PML mystic built with quantum tube? I understand QT doesn't have sufficient rigidity for mach+ flights.

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That is right . . . so forget about mach+ flight with quantum tube.

hball55 said:

That is right . . . so forget about mach+ flight with quantum tube.

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I suspect it will work if the tube is glassed. Kurt

RKeller said:

so this is kind of an old post but man it would be cool if open rocket incorporated fin flutter simulations! they already have the flight data, the fin design, fin material, seems like a natural fit to also do flutter calculations...

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The other thing to remember is that the parameters for the materials "in" finsim may not match the material that one is using. For instances, I don't know how one would be able to simulate plywood fins that are fiberglassed in a 3 layers in the 1/3rd, 2/3rds, full span fashion with a 45 degree rotation of the fibers in the middle layer. Man, I wish somebody would carry good 1/8" 5 ply plywood. My last piece warped over the years. Kurt

Let's ask a question about materials. Specifically composites. If you create a fillet with say epoxy A. How do you account for variations in hardener/resin ratio, thoroughness of the mix, type of amendment, amount of amendment, orientation of the fibers, and amendment/epoxy ratio. Throw in variations in the quality of processing technique and you have a pretty complex thing to try and model.

I am not saying to not try. What I am saying is that this is not simple stuff to analyze/ simulate accurately. I think if you try to accomplish this you are into a lot more complication that you anticipate.

ksaves2 said:

I suspect it will work if the tube is glassed. Kurt

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Quantum tube is not supposed to be glassed and PML kits with standard QT airframes can and should be special ordered with phenolic airframes if you want to glass them. https://www.publicmissiles.com/images/PMLAirframesFAQ.pdf

Bob