Station in orbit wobbling itself to death : physic bug?

[wibou]

Hi all

(Edited: Although the thread have been moved to "Support - Windows", I actually run KSP under Linux if that change anything)

I recently built a somewhat massive space station in high Minmus orbit. The goal was to use the station a refueling depot for vessels traveling farther in the Kerbol system.

However, I have a very big problem with the station: everynow and then, the station will wobble itself to death, litterally.

It's very annoying and I'm trying to find ways to fix this station or (at least) improve future stations.

Before anything else, yes I checked the following:

SAS is turned OFF.

ALL Reaction wheels are OFF.

ALL Pods and Modules torque are OFF.

The station is well outside (150km) of Minmus and so should no experiment any drag or weird proximity effects.

From what I can see, everytime the physic engine loads the station, I have about 50% chance to get a massive "wobble wave" that tears the station appart.

The "wave" might break everything appart suddently or it can build itself up slowly until it reaches breaking point.

It is especially annoying when I try to rendezvous with the station; I basically have to quickly save just before I pass the 2.5km mark and reload over and over until the station decide NOT to blows itself to pieces.

Here is the station:

Note that even if you see engines on the picture, the station is NOT meant to be moved. Those are what brought those tanks there; they will be ditched once their fuel tanks go dry from refueling others.

Granted, it might have been a dumb idea to hang those fuel tanks from girders but since there is very little forces going on, I believed it would hold on. And it does, when the physic engine decides not to go nuts.

Any tips?

Anything I could do to save that poor station?

Anything I should / should not do in the future to avoid such mess?

EDIT: Since the thread was moved to support, here are my specs:

Linux 64 bits (32 bits compatibility ON)

KSP Steam, version v0.90.0.0 Beta

I7 Quad 3.7Ghz

8 Gb RAM

NVIDIA Quadro K1000M (Nvidia drivers version 340.65)

Edited January 2, 2015 by Claw
Added system spec since it was moved to support section

[Claw]

So this is a bit of a known thing. Is this sort of a slow "wobble, wobble" buildup before it comes apart? Or is it pretty quick, within seconds, "wobble->shakes like crazy->BOOM" sort of thing? The faster one is usually a clipping problem while the first one is sometimes a different problem.

I can't say for certain what causes it, but the usual culprit is clipping (at least in the fast case). And it's usually when clipping a bunch of physicsless parts together. It's hard to tell from the picture if you have any of that going on.

I have also seen ships, similar in design to your station with girders and orange tanks, that exhibit the same sort of behavior. In that case, I was able to stop the wobbling by transferring some of the fuel around out of one of the orange tanks to change the mass distribution of the ship. Ultimately that orange tank (and it's mirror image) were undocked from the ship and sent adrift to prevent the problem completely.

See if any of that helps. Otherwise you can also try posting a save file and I will see what I can do.

Welcome to the forums!

Cheers,

~Claw

[gmiddlemass]

If it's any consolation my last station did exactly the same thing after flying it all the way out to Jool. It performed perfectly all the way there but as soon as I decoupled the drive section that transported it there the wobble started and the station blew itself apart about a minute later. I fixed it by adding a few struts in key areas where the wobble had started (after reloading and watching a few times to try and see where the problem lay). I did eventually get the original version stable but the extra struts seemed to sort out the problem out on re-launches of the same basic design.

Good luck and welcome to the forum.

[wibou]

Although I did experiment the "wobble->shakes like crazy->BOOM" case, it's mostly a "slow wobble build up" case. It usually needs about 10-15 seconds to break apart once I notice the initial wobble.

That said, I spend two hours experimenting with various configuration and putting the tank farther from each other (i.e. 2 on the central hub docks, 1 on the very top dock and 3 on the struts docks) make it become somewhat stable.

It still gets into "stupid wobble mode", just less often. I'd say it stays stable about 90% of the time so far (which is not that great when you think about it).

For what I can see, having more than 4 of those tanks on the same structure create a risk of the physic engine freaking out and start hallucinating force inside the structure.

I wonder if the bug is caused by the "Rockomax Jumbo-64" tank specifically, or if it has something to do with the raw mass of the structure...

I really hope it's not the weight, otherwise it will be hell to dock a ship to refuel.

gmiddlemass, did you had the problem with the same fuel tank or was it another part?

[gmiddlemass]

There were no orange tanks on my station (unless you count the one which I had just decoupled) but it was a six sided symmetry design like yours. Mine used the Mk2 crew cabin and some smaller tanks on each arm. The wobble started slow but built very rapidly till it exploded like you describe.

I've also experienced the problem when radially attaching boosters but not often and I can just revert to the assembly building to fix it. A few struts to tie the boosters together at the top and bottom always fixes it so I would suggest that's what is happening with your station too... The tanks are wobbling around the single fixing point, if you could strut them together it would probably sort it.

I've used 7 orange tanks before (6 attached radially round 1 central) with no problems using the biggest docking ports so it can deffinately be done.

[flekota]

Hi all

(Edited: Although the thread have been moved to "Support - Windows", I actually run KSP under Linux if that change anything)

I recently built a somewhat massive space station in high Minmus orbit. The goal was to use the station a refueling depot for vessels traveling farther in the Kerbol system.

However, I have a very big problem with the station: everynow and then, the station will wobble itself to death, litterally.

It's very annoying and I'm trying to find ways to fix this station or (at least) improve future stations.

Before anything else, yes I checked the following:

SAS is turned OFF.

ALL Reaction wheels are OFF.

ALL Pods and Modules torque are OFF.

The station is well outside (150km) of Minmus and so should no experiment any drag or weird proximity effects.

From what I can see, everytime the physic engine loads the station, I have about 50% chance to get a massive "wobble wave" that tears the station appart.

The "wave" might break everything appart suddently or it can build itself up slowly until it reaches breaking point.

It is especially annoying when I try to rendezvous with the station; I basically have to quickly save just before I pass the 2.5km mark and reload over and over until the station decide NOT to blows itself to pieces.

Here is the station:

http://s17.postimg.org/jufwo31pb/screenshot4.png

Note that even if you see engines on the picture, the station is NOT meant to be moved. Those are what brought those tanks there; they will be ditched once their fuel tanks go dry from refueling others.

Granted, it might have been a dumb idea to hang those fuel tanks from girders but since there is very little forces going on, I believed it would hold on. And it does, when the physic engine decides not to go nuts.

Any tips?

Anything I could do to save that poor station?

Anything I should / should not do in the future to avoid such mess?

EDIT: Since the thread was moved to support, here are my specs:

Linux 64 bits (32 bits compatibility ON)

KSP Steam, version v0.90.0.0 Beta

I7 Quad 3.7Ghz

8 Gb RAM

NVIDIA Quadro K1000M (Nvidia drivers version 340.65)

I'm having the same problem even with ship Iv had in orbit for months. Doesn't matter What they are built with or how. Just built a simple launcher and I used it a few time and on a certain launch it happen I did put more struts on it and it helped but get the same result from stopping the game and starting over again. I think this is something the Squad needs to look int I think is the Physical part of the game.