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Old 06-10-2009, 06:19 PM
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Pyro Pro Pyro Pro is offline
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Default Buggy design?

Thought I'd just post this to see if anyone can get it working. For some reason, when I sim this, the rocket will appear to fly normally, but then I'll suddenly get "nan" for all simulation values, and the simulation will continue executing indefinitely. Because of this, I can't load a 2D flight profile, but I can look at the graphs of the simulation, which appear fairly normal (though, altitude is a bit lower than I'd expect, acceleration seems to be jumping around wildly towards the end of the burn, as well as the Cd, which starts off in a normal range, but starts rapidly pinging between ~0.5 and 2.5 towards the end of the first second of flight).

Ideas?

I simulated the tank tubes with non-ejectable pods for authenticity. I could redo the design with them as inside tubes, which would probably be more stable, program-wise, but... why shouldn't I be able to use pods

I also have a 3-stage version of this design (I've reduced it to a single stage due to time constraints on building the real thing), and it did virtually the same thing.
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File Type: rkt 1-227 Saturn 1B SA-205.rkt (126.4 KB, 83 views)
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Old 06-10-2009, 09:13 PM
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Nope, inside tubes don't help either...

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File Type: rkt 1-227 Saturn 1B SA-205 IT.rkt (116.9 KB, 71 views)
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  #3  
Old 06-10-2009, 10:03 PM
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CPMcGraw CPMcGraw is offline
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David,

I've been getting a bunch of designs that create a nan (not a number) condition recently. I sent Tim a message awhile back, but the suggestion was to check for any "Custom" material entries...

This is a bug in RS9, and it is probably related to the pods feature, because I never recall having nan on any RS8 design. Look for material entries with "Custom" material.
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Old 06-10-2009, 10:44 PM
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Quote:
Originally Posted by CPMcGraw
David,

I've been getting a bunch of designs that create a nan (not a number) condition recently. I sent Tim a message awhile back, but the suggestion was to check for any "Custom" material entries...

This is a bug in RS9, and it is probably related to the pods feature, because I never recall having nan on any RS8 design. Look for material entries with "Custom" material.

Craig,

I've been getting the same thing and I'm not using the pods feature. I do have some "custom" parts. I downloaded 9.0.5f80 but no improvement.

I've also been getting a weird condition where if I try to hit a button in construction windows I get an error beep, and nothing happens. If I put the cursor off the window, click, and then come back to Rocksim and click the button it works fine. I've been using Rocksim since version 4, when I used it on a Mac using Virtual PC, and I've never had anything like this.

I'm also getting a freeze if I run an optimal mass sim and try to look at the graph.

I'm running Rocksim on the latest version iMac running system 10.5.7.
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Old 06-10-2009, 11:55 PM
blindeye2 blindeye2 is offline
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Default Suspect AT10-3 motor data

I was able to run simulations for all the available motor configurations except for the AT10.
I would speculate that something in the data is causing a numerical instablility in the solution. I do not know the detailS of the soulution method used within ROCKSIM.
This is not an uncommon problem in transient numerical solutions.
Hope I was of some help.
Bob
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  #6  
Old 06-11-2009, 12:31 AM
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Quote:
Originally Posted by Gus
Craig,

I've been getting the same thing and I'm not using the pods feature. I do have some "custom" parts. I downloaded 9.0.5f80 but no improvement.

I've also been getting a weird condition where if I try to hit a button in construction windows I get an error beep, and nothing happens. If I put the cursor off the window, click, and then come back to Rocksim and click the button it works fine. I've been using Rocksim since version 4, when I used it on a Mac using Virtual PC, and I've never had anything like this.

I'm also getting a freeze if I run an optimal mass sim and try to look at the graph.

I'm running Rocksim on the latest version iMac running system 10.5.7.


I've noticed one additional problem, when running RS9 on my laptop (4-yr-old Toshiba Satellite, XP Home). The program freezes when I try to edit the plot points of any fin using the mouse pad. If I edit the points in the X-Y table grid, it works OK. If I try to drag a plot point with the pad, the program quits responding, requiring a 'three finger salute' to break the ice.

No, RockSim is not perfect and has a long way to go in a couple of major areas. On the 'nan' issue, everyone here who has encountered this should send a note to Tim. I think he already has an idea where the problem might be, but obviously he has not found it for sure. He mentioned something about having seen the problem come up before, but that it was intermittent. I've had it happen on about a dozen designs since starting with RS9, which made me think it had to be something associated with a 9-centric feature.

Bob's observation about having it happen with one motor out of several is a new twist on what I've seen. Usually, once I start seeing the 'nan' runs, it keeps doing 'nan' until I make serious changes to the file, or try running the file on another computer. Using another computer sometimes works, sometimes doesn't. No immediate pattern.

All of my 'nan' runs to this point have been designs that used pods. If designs with no pods are also seeing 'nan', then the problem is much deeper in the core code.
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