Shaking apart, IN orbit!

[Steelsunoa]

So, I have built a circular re-fueling ring that has obtained a circular orbit at 250k. I assumed getting into obit would be my biggest challenge, but it turns out I was wrong. After I separate the last stage, leaving the ring without any engines or maneuvering ability other than RCS, the craft will slowly start shaking until it eventually explodes. This occurs whether RCS or SAS is engaged or not, and did not happen when I originally separated the engines. I had time to admire it and take a quick screenshot, but now when I go back it will inevitably destroy itself. Luckily I have an auto-save file of the craft prior to separating the engine, so I will hopefully be able to dock a small living section to try to maintain stability.

Anyway, I was just curious if this has happened to anyone else or if you can tell me any reason this may be happening.

http://imgur.com/a/Ss0SK#0

Edited August 31, 2015 by Steelsunoa

[Pecan]

Part clipping would be my prime suspect.

[Fearless Son]

My first thought is, "Do you have something clipping?" Because a ring like this has to have some non-standard attachment points somewhere. I am wondering if what is happening is there is a bit of a "bounce" happening from clipped parts trying to separate, and it is introducing a harmonic physics response. That is, as it tries to bounce apart, it pushes the parts next to it, which then try to snap back against it, which then makes it bounce harder, etc. It would be a little physics glitch that would turn a minor force into a major one, given enough time.

The aerodynamic and thrust forces might have been enough to overwhelm the harmonic forces while it was on ascent to orbit, but once it was parked and idle, well...

[Steelsunoa]

This was my first thought as well, but I checked the craft file in the VAB. I attempted to avoid any clipping, the ring is just four quarter circles that technically don't ever touch at the four intersecting points. I kept them stable with the "spokes" and failed to use any struts that did not originate from the center of the circle.

So I just disabled all of the torque and this seems to have solved my problem. The "Advanced Inline Stabilizer" it seems is the culprit here! Perhaps the placement of them, one on each end, was causing some strange rocking motion as it attempted to stabilize the craft. Phew! Thanks for everyone's input though!

- - - Updated - - -

Fearless Son, great word choice by the way...this concept lead me to start looking at the Advanced Inline Stabilizers. I think the "bounce" was happening due to the lack of lateral struts across the circle. So the four sections had small downward arc since they are not perfectly center on the fuel tank. Without the stabilizing action though they seem to sit together just fine. Thanks again!

[Claw]

The SAS was probably wobbling enough that it sent the vibrations out of synch with the control position.

The big contributor to this is the fact that there are no cross-struts (that I can see) after you ditch the engine and tank. So the whole ring is unstable cross-axial (across the flat plane of the ring). I'm happy for you that turning off SAS fixes it. Sometimes the rigid bodies will still feedback on themselves. So you probably have plenty of structure perpendicular to the station axis, just needs some cross-axis.

Looks pretty sweet too.

Cheers,

-Claw

Edited August 31, 2015 by Claw

[Steelsunoa]

Thanks Claw!

I had the cross-struts, but I took them away for aesthetic reasons lol. The engine tank, and it's struts, were the only things keeping it from shaking itself apart before, exactly!

[Wallygator]

That looks really cool!

But couldn't you have one big tank in the middle instead of the ring?

If the answer is just asthetics then that's ok too.

Nice work regardless.

[mrclucks]

Try time warping and untimewarping quickly. If it continues afterwards then its a structural problem

[Steelsunoa]

Thanks Wally! It is by no means "practical" lol, I just wanted a re-fueling ring in LKO for fun. I had a more elaborate design prior to the changes in aerodynamics, maybe one day I'll re-launch that over-engineered monster. Ultimately though, my plan is to get Terok Nor (DS9) into orbit!!

Just for fun...I added some old pics to that album.

[Vanamonde]

You mean like this?