Odd open rocket results

[Old School Doug]

Here's an odd problem I've been having with Open Rocket sims. I decided to downsize a 2 stage Raptor to a 18mm motor config for an upcoming club launch (smallish field that won't support bigger motors) . When running a sim for B6-0/B6-6 motors I initially got a warning for a large angle of attack (115 degrees). I ran a sim with C6 motors and had no warnings. Closed up the file to do some grandson watching duties. Once done, I opened up the file and went to the sims again to see what I needed to do to correct the problem. Now I get no warning on the B motors and a 91 degree warning on the C motors. Nothing in the design nor the launch parameters had changed. Now for the kicker. I reran the sims, again with no changes, and the angle of attack warning for the C motor config was gone. I have no clue where to even begin troubleshooting this problem or if I should just ignore the warnings? Ideas??

 

[neil_w]

Took a quick look and... that is weird. Will dig into it as I have time. Gotta be an answer in there somewhere.

 

[neil_w]

OK, this one has me stumped. Will research and be back if and when I figure out anything.

 

[neil_w]

This is interesting:

In the new beta build, everything is fine. Also apogee estimates are down 11%-13%. I believe that is expected with the new version, many things are tweaked.

But what it says is, there's probably nothing wrong with your file; certainly I couldn't make the warnings go away. You are running into some minor bugs and edge cases that are fixed in the new version.

 

[Old School Doug]

Thanks for looking into the problem Neil. Is it safe to assume that OR 20.0x isn't available to the general public? I've not been able to find a download for it, although I haven't done an exhaustive search.

 

[neil_w]

Check your PMs.

 

[JoePfeiffer]

This is... weird. In 15.03 the angle of attack becomes very high near apogee, which is certainly not a surprise, but I thought there was a check in the code that didn't set the warning in that case (the worst angle of attack is actually showing up after apogee). In current unstable it's not showing it at all. So, my answer is ignore the warning.

Note that you can add extra plots to the graph in the plot/export dialog to try to figure out what's going on in the simulation (that's what I did looking at it), and you can also put all the data you want out in a spreadsheet.

The code is all at https://github.com/openrocket/openrocket
Current development is on the unstable branch.