Mach 1+ Simulation Software

Hello,

Can anyone recommend a good software for simulating transonic and supersonic flight? I understand that RASAero can manage it but I recently found some information which caused me to doubt this (found on this thread, #22). As well, last I checked, OpenRocket warns against using it to simulate supersonic behavior. Are there any programs out there (preferably free) that can give good quality predictions?

thanks

I still use a combo of Rocksim and Rasaero. I think the issue/anomaly you are referencing is just that- an anomaly. The flyer may have not have accurate sim info in the program, or perhaps he designed his rocket without enough stability margin. The cp moves and the calculations are an approximation based on your inputs. If the inputs are not accurate that can cause issues. If motor performance is different than the design you can have issues. Frankly, if you are designing for minimum static stability and hi Mach you are asking for trouble as you are leaving no margin for error. My thought is that based on the above you should not design for less than a static margin of less than 2 to give yourself a little wiggle room.


Mark Koelsch
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As a participant in the other thread:

RASAero is very accurate altitude-wise. It can be too optimistic for stability. I don't believe it is an anomaly, because the inputs for Bare Necessities were absolutely accurate, and it supposedly always had >2 calibers of static margin according to RASAero.

OpenRocket doesn't offer drag models for the various fin profiles that RASAero does, but with regards to stability it seems to be spot-on. The same rocket as mentioned above was predicted to go unstable at the same point that it did.

I recommend using both, each one for its own strong suit.

Just a guess, but it's probably a good idea to design your rocket to pass the stability criteria in both programs.


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I guess I'll probably stick with the OpenRocket/RASAero combination.

Thanks!

The reality is that these programs are all approximations. To be really accurate on Cp probably would take a CFD type program. A fair amount more complicated. I believe there are open source CFD programs available, and I started to look at a couple but I do not have the time to really dig into them.


Mark Koelsch
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markkoelsch said:

The reality is that these programs are all approximations. To be really accurate on Cp probably would take a CFD type program. A fair amount more complicated. I believe there are open source CFD programs available, and I started to look at a couple but I do not have the time to really dig into them.

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The reason why I wanted to find some open source rocket simulators was more for the verification of a system that myself and my colleagues are creating. The system will be a Simulink block diagram which will use Cp and drag information which is generated using ANSYS. We just needed something like openrocket or RASAero to make sure our simulations were creating results in the correct range.

If you have links to the opensource CFD programs, I'd be happy to try them out.

Thanks!

Openfoam


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I haven't used this yet, but it's worth looking into.
https://www.aerorocket.com/hyperx.html

Alex

Aksrockets said:

I haven't used this yet, but it's worth looking into.
https://www.aerorocket.com/hyperx.html

Alex

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Alex, Aerorocket products are no
longer for sale. I think he might provide them under certain circstances though.


Mark Koelsch
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markkoelsch said:

Alex, Aerorocket products are no longer for sale. I think he might provide them under certain circstances though.

Click to expand...

On the website, it says that they will donate their products to student groups. I'll try emailing them to see if this offer still stands.

Neilw said:

On the website, it says that they will donate their products to student groups. I'll try emailing them to see if this offer still stands.

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Read here to see what happened to the last guy.

Buckeye said:

Read here to see what happened to the last guy.

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hmmm...

Thanks for the heads up. I'll proceed with caution.