Openrocket - parachutes resize themselves

[Dave S.]

I have been having a problem w/ Openrocket (using version 23.09).

My sim of a dual deploy rocket had been working just fine, but recently an issue has cropped up.

Whenever I exit and then reopen the file, the packed length of the chute changes. In fact it changes to a larger length such that the packed length is now long enough that it sticks out the back of the rocket. I can change the packed length back to something reasonable (~7 inches) to keep it inside the booster section, file save, and exit. When I open that same file, the packed length is again changed to say 21 inches or more.

This can happen with the main, the drogue, or both. What the heck?

This behavior is very odd, but I am thinking this may be a problem that has been encountered before?

 

[3stoogesrocketry]

I have been having a problem w/ Openrocket (using version 23.09).

My sim of a dual deploy rocket had been working just fine, but recently an issue has cropped up.

Whenever I exit and then reopen the file, the packed length of the chute changes. In fact it changes to a larger length such that the packed length is now long enough that it sticks out the back of the rocket. I can change the packed length back to something reasonable (~7 inches) to keep it inside the booster section, file save, and exit. When I open that same file, the packed length is again changed to say 21 inches or more.

This can happen with the main, the drogue, or both. What the heck?

This behavior is very odd, but I am thinking this may be a problem that has been encountered before?

This has happened to me a few times when I'm opening rocksim files in Open Rocket. I'm still trying to get most of my files back as when I updated BurnSim, almost all my OR files are unable to open.

 

[neil_w]

I have been having a problem w/ Openrocket (using version 23.09).

My sim of a dual deploy rocket had been working just fine, but recently an issue has cropped up.

Whenever I exit and then reopen the file, the packed length of the chute changes. In fact it changes to a larger length such that the packed length is now long enough that it sticks out the back of the rocket. I can change the packed length back to something reasonable (~7 inches) to keep it inside the booster section, file save, and exit. When I open that same file, the packed length is again changed to say 21 inches or more.

This can happen with the main, the drogue, or both. What the heck?

This behavior is very odd, but I am thinking this may be a problem that has been encountered before?

It is odd, and it certainly shouldn't be happening. Can you attach one of the files that has the drogue set short, and I'll see if it reproduces on my end. When you post it let me know exactly how long you have it set to.

This has happened to me a few times when I'm opening rocksim files in Open Rocket. I'm still trying to get most of my files back as when I updated BurnSim, almost all my OR files are unable to open.

Please define "unable to open", and please post one such file so I can try it out.

 

[bad_idea]

This behavior is very odd, but I am thinking this may be a problem that has been encountered before?

I've run into it when using preset chutes. I never had the time to do proper diagnosis and isolate reproducibility so never filed a bug on it. (For instance, as I do a lot of copying from one rocket to another, it's possible some of my chutes - or perhaps parts of the rocket they interact badly with - were originally built with dev branch builds two years ago, and I wouldn't want to file that as a bug without being sure it was a problem with new builds.) It's interesting that someone else is having the same problem, since I've never seen anyone else mention it.

 

[jmasterj]

I've seen it repeatedly; I'm sorry I e been too lazy to file a report. If still necessary on Wednesday I'll post one of my orks that it keeps happening to.

 

[MarsLander]

@neil_w Here is my L2 4x upscale EAC Viper rocksim file that does it every time. Projects the parachute way to the rear of the rocket. Not the exact problem of the OP (being a saved OR file), but the same behavior.

Hope it helps.

 

[Capt. Eric]

I have been having a problem w/ Openrocket (using version 23.09).

My sim of a dual deploy rocket had been working just fine, but recently an issue has cropped up.

Whenever I exit and then reopen the file, the packed length of the chute changes. In fact it changes to a larger length such that the packed length is now long enough that it sticks out the back of the rocket. I can change the packed length back to something reasonable (~7 inches) to keep it inside the booster section, file save, and exit. When I open that same file, the packed length is again changed to say 21 inches or more.

This can happen with the main, the drogue, or both. What the heck?

This behavior is very odd, but I am thinking this may be a problem that has been encountered before?

I see the same thing on many of my sims. Have not studied it to see what the common thread is. Annoying though.

 

[SiboVG]

@neil_w Here is my L2 4x upscale EAC Viper rocksim file that does it every time. Projects the parachute way to the rear of the rocket. Not the exact problem of the OP (being a saved OR file), but the same behavior.

Hope it helps.

Could you elaborate on this? The only strange thing I found is that the harness mass object is extremely long:


But the parachutes appear to look just fine? They're positioned just like RockSim.



Concerning the very long harness mass object, at first sight, OpenRocket appears to be doing its job. I reviewed the .rkt content and the length of the harness mass object is set to 10363.2 mm - which OpenRocket uses as the length for the harness object. No idea why that value is so high in the RockSim source though...


So, could you please elaborate on what OpenRocket is doing incorrectly?

 

[neil_w]

Same happens for me here as for Sibo (I would certainly hope and expect it would, but you never now).

 

[MarsLander]

So, could you please elaborate on what OpenRocket is doing incorrectly?

Let's separate the issues. The OP described a situation where his parachute got resized when saved and re-opened. Others chimed in that they have seen it also. At some point, someone asked for a file.

My issue as you show with the viper, may be a RS issue, I don't know. I posted it because I saw something different between the behavior of the two files that was a similar "resizing" the OP noted...something was sized unexpectedly (harness sticking outside the back of the rocket).

As to my file, I don't know how it got a "Length" like that. Here is how the mass object is setup:



I don't know how the "Calculated component mass" got entered/calculated. Note MASS OVERRIDE is on, and the 266g and 19.25" are what are used for the mass of this object in RS. I wouldn't expect the length to be shown as it is in OR.

Hope that helps, happy to add any more if I can...

 

[SiboVG]

Let's separate the issues. The OP described a situation where his parachute got resized when saved and re-opened. Others chimed in that they have seen it also. At some point, someone asked for a file.

My issue as you show with the viper, may be a RS issue, I don't know. I posted it because I saw something different between the behavior of the two files that was a similar "resizing" the OP noted...something was sized unexpectedly (harness sticking outside the back of the rocket).

As to my file, I don't know how it got a "Length" like that. Here is how the mass object is setup:

View attachment 621735

I don't know how the "Calculated component mass" got entered/calculated. Note MASS OVERRIDE is on, and the 266g and 19.25" are what are used for the mass of this object in RS. I wouldn't expect the length to be shown as it is in OR.

Hope that helps, happy to add any more if I can...

Yeah, RockSim is a bit odd in terms of defining packed dimensions for mass objects/recovery objects. As far as I can tell there's no way to adjust the dimensions of a mass object in RockSim. However, it does save a length and diameter in its .rkt file. So I guess that at some point, RockSim used a bogus number for the harness MO length, which OpenRocket then correctly imports.

OP's problem does sound like a real OR problem, so if @Dave S., @bad_idea or @jmasterj could post a .ork file and steps to reproduce the bug that'd be great . Because everything's working nominally for me...

 

[jmasterj]

I should have taken an initial screenshot, but here's what the main is supposed to look like (I just fixed the packed length). Look at the drogue, though, which is clearly longer than intended. Immediately after taking this screenshot, I hit OK on this dialog, saved the sim, and closed it.




Upon re-opening (and every subsequent time I re-open this file), this is what I get. Note the main has grown longer by a factor of slightly more than 4x. The drogue probably did something similar, but I didn't record that the first time.



The data in the .ork reflects the saved info from the first screenshot (I assume the storage units are meters), which makes sense:

<parachute> <name>Main - Rocketman Std Parabolic Parachute [Cd .97]</name> <id>4fd416c5-4377-423f-8449-282e1572499e</id> <preset type="PARACHUTE" manufacturer="Rocketman" partno="LS-12" digest="19bb7da53fae3b7f50541b58b41d32c0"/> <axialoffset method="top">0.45719999999999955</axialoffset> <position type="top">0.45719999999999955</position> <overridemass>0.4819418927</overridemass> <overridesubcomponentsmass>false</overridesubcomponentsmass> <packedlength>0.4064</packedlength> <packedradius>0.0635</packedradius> <radialposition>0.0</radialposition> <radialdirection>0.0</radialdirection> <cd>0.97</cd> <material type="surface" density="0.035653924">Ripstop nylon, ultra lightweight, 2 mil</material> <deployevent>altitude</deployevent> <deployaltitude>182.88</deployaltitude> <deploydelay>0.0</deploydelay> <diameter>3.6576</diameter> <linecount>4</linecount> <linelength>3.6576</linelength> <linematerial type="line" density="6.56168E-4">Spectra #200 [Round 1.5 mm, 1/16 in]</linematerial> </parachute>

Both the main and the drogue are predefined parachutes, which may matter.

The debug log has a bunch of repetitive output from TubeFinSetCalc.java but nothing else that might explain this issue.

@SiboVG or @neil_w, please let me know if there's anything else you'd like from me. I am a software developer who wishes he had time to help with OpenRocket (but doesn't). If there's any technical instructions you need to give me, I have a shot at following them.

 

[neil_w]

Interesting. I'm looking at the drogue and it shows up like this in the ORK file:


Packed length is .687m = 27in, which is still crazy. What packed length did you have the drogue set to?

When it loads it ends up at 244in, which is even crazier. Thanks for the file, that is very helpful.

 

[jmasterj]

Interesting. I'm looking at the drogue and it shows up like this in the ORK file:
View attachment 621742

Packed length is .687m = 27in, which is still crazy. What packed length did you have the drogue set to?

When it loads it ends up at 244in, which is even crazier. Thanks for the file, that is very helpful.

Unfortunately I don't know what the drogue was supposed to be, because I didn't look at the .ork before I corrected the main and resaved.

 

[SiboVG]

Thanks for the info @jmasterj! I've found a bug in the code and patched it. This issue only occurs when saving files that use preset parachutes. If you want to bypass this bug, you can change one of the parachute parameters, e.g. 'Number of lines' from 4 to 3 and then restore it to 4. This will clear the preset and bypass the bug.

 

[Dave S.]

I am the original poster. Sorry but I have not been able to reply sooner due to the holidays.

This file did start life as a RocSim file, before I converted it to OpenRocket and edited the heck out of it.

The simulation is of a dual deployment rocket, so there is a drogue and a main parachute. Both parachutes are ones I am getting from the parts library database. Here is the info on them:

#1 main:

parts library = CFC-048-N
packed diameter = 3 inches
packed length = 30.375 inches, changed it to 6 inches
automatic = no (box is unchecked)

#2 drogue:

parts library = CFC-024-N
packed diameter = 3 inches
packed length = 29.773 inches, changed it to 6 inches
automatic = no (box is unchecked)


I have not looked at this file in a week of more. When I opened it a few minutes ago, both the drogue and main were changed to obvious errors (29.773 and 30.375 inches respectively). I Changed both lengths to 6 inches, and did a file-safe-as to a newly created Open Rocket file. I opened it and saw that the packed length of both of them had been changed. That is the file I have attached to this post.


I have seen this before on a couple other files, but was never able to figure out what was going wrong. Any assistance would be greatly appreciated.

 

[Dave S.]

Ooops - It looks like someone has already figured out the bug and a work-around fix.


Fantastic!