Space Stations destroy themselves (flapping & spinning)

[mug17]

I'm relatively new to KSP only really playing it for the last few weeks. Mastered docking after doing the tutorial two times and started building my space station. But now for the third time the station started to destroy itself. In my first try I added several modules together. Only problem was low electricity so I added two service modules with more solar panels and batteries. After attaching, I deployed the masts with the solar panels. The station was stable, no wobble. I switched to the delivery rocket do deorbit it. But immediately the solar panels and their masts started to flap violently and the station began to spinn.

Here is one of the service modules in the VAB with masts and solar panels deployed:

 

Next try I it happened after deploying the first module and switching to the delivery rocket:

 

After that I suspected it might be a problem with the the hinges. So I put a central node and two service modules into orbit and dock them together, no problem.  I launched the a masts with solar panels with the next rocket, attached two masts to one service module using docking ports and switched back to my delivery rocked to attach the third when it happened again. The station started twisting and solar panels exploded.

Because the station is pretty small on the screenshots I also included a view in the VAB of the hole station except for the still connected rocket stage:

 

Does anybody know what is happening? Stations are stable when I control them, but self-destruct when I switch to a vessel nearby. It is pretty frustrating.

 

KSP 1.11, Windows 10, GOG

[Serenity]

11 hours ago, mug17 said:

Does anybody know what is happening? Stations are stable when I control them, but self-destruct when I switch to a vessel nearby. It is pretty frustrating.

If you are(and you should) use autostruts then heaviest cause krakens like yours.

Using only grandparent usually solves the problem, every time physics load, or you dock/undock, the heaviest part changes sometimes

and the game tries to re route the heaviest autostruts causing major problems.

Using anchor type is a very good solution, like having the heaviest part always in the main station but generally avoid using heaviest or root autostruts and you should be fine.

[mug17]

Thanks for the reply.
I don't fully understand what you mean. Is autostruts automatically active? I haven't seen any options in that regard. I simply put the parts together in the VAB.
Only after adding modules with solar cells on masts to the station did the problems appear. But my first station had a mast and solar cells on the first module and the problems only started after I added the forth and fifth module.

[OHara]

Autostruts are in an optional menu.  You can activate that option from the in-game pause menu, choosing settings then looking for 'Advanced Tweakables' to enable.  Then the autostrut options are in the right-click menu.

But since you have not used autostruts on this station, they are not likely the cause of your problem.  From your description, I suspect that the probe core is wobbling one way while the RCS jets are wobbling the opposite direction, so SAS controlled by the probe-core could drive the oscillation bigger.

Try turning off SAS before going into more complicated solutions.

I put a space station on KerbalX (link) that illustrates the wobble that can happen that I see.  You can try putting autostruts on the ends of its solar panel arms, if you want to experiment with the problems autostruts can cause.

[Kerbart]

The issue is purely hinges and solar panels. I've had the same problem. It even happens on the launch pad when you extend the panels and fold out the hinges. I solved it by "don't do that."

 

[swjr-swis]

I think it's the cubic octagonal struts, which appear to be abundantly used in these stations.

I recreated a similar space station with a 2.5m core and two of the above modules attached by Jr docking ports, and spent a good 15 mins swinging the hinged solar panels and RCS thrusters back and forth, locking and unlocking, enabling and disabling SAS and doing barrel rolls and pirouettes, then undocking the attached vessel and flying it back and forth around the station, docking and undocking and getting some distance away and flying near again. Nothing at all happened.

Then on the last flyby, the console suddenly got spammed with the following messages:
 

Warning: BoxColliders does not support negative scale or size.

The effective box size has been forced positive and is likely to give unexpected collision geometry.

If you absolutely need to  use negative scaling you can use the convex MeshCollider.
Scene hierarchy path "strutCube/model/cubestrut"

And the station got an epileptic seizure and shook itself apart.

Station craft file, for error reproduction tests: https://www.dropbox.com/s/kpw31nb76kuaeu0/0test0.craft?dl=0

Edited April 12, 2021 by swjr-swis
added screenshots and craft file

[OHara]

8 hours ago, swjr-swis said:

Station craft file, for error reproduction tests: https://www.dropbox.com/s/kpw31nb76kuaeu0/0test0.craft?dl=0

So in that case, it is the bug with lots of solar panels around a light part (link link).  I don't know what it is about solar panels that causes this problem so I don't know any direct way to avoid it.

KSP tries to make these cubes-struts physics-less but then encourages us to attach physics-full objects onto them, so in effect we have 10 solar panels all connected to the single hinge.  This problem does not appear on this craft if we turn off that 'physicsless' option, and let Unity simulate normal physics on the cube-struts
@PART[strutCube] {%PhysicsSignificance = 0 }

Another way to avoid the self-destructive wobbling, would be to put a line-strut from the outermost solar panels to the hinge, but this is awkward with the other panels in the way, so this leads us again to use those evil autostruts.  The usual incantation "Autostrut: Grandparent Part" on the outmost two pairs of panels.