Auto-strut and root part?

[strider3]

1. Once I have decided on which part will be the "root" part, should that root part have auto-strut disabled?

2. When putting together a space station, in orbit, will the root part (in this case a heavy part in the central stack) change as I attach the station's arms?

In trying to alleviate this stations death wobble, I am trying different auto-strutting techniques and I've run into another problem...station coming apart when docking arm #3 of 4. In the screenshot I have the octo-girder shown as the "root" (in the VAB, at least), the weldable Konstruction docking ports auto-strutted to the root. After docking an arm, I weld the ports and then set the auto-strut for the arms inner octo-girder to "root", and all other parts of the arm to "grandparent". This has worked fine for the first 2 arms. Now when I try to dock the 3rd arm, the station breaks up into 3 large pieces as soon as docking is complete (before "welding" the arm)...and I'm at a loss as to why. I've used these Konstruction weldable ports for station building in previous versions of KSP without having this issue (the death wobble has always been an issue  , thus the CS-R2 Portable Struts on the 2 attached arms). I'm wondering if my auto-strutting technique, in this case, is causing the break up on docking? I should also note that the station does not break up at the welded joints, necessarily.

Edited December 11, 2019 by strider3

[AHHans]

On 12/10/2019 at 11:20 PM, strider3 said:

1. Once I have decided on which part will be the "root" part, should that root part have auto-strut disabled?

AFAIK it doesn't really matter. I believe that "to root" and "to grandparent" just don't do anything on the root part, and I don't use "to heaviest" anyhow. For myself I usually just activate "to grandparent" on (nearly) all parts, including the root part.

On 12/10/2019 at 11:20 PM, strider3 said:

2. When putting together a space station, in orbit, will the root part (in this case a heavy part in the central stack) change as I attach the station's arms?

In general: yes! During docking the two crafts will become one craft with the new root part being the root part of one of the two original crafts. I don't know how the game chooses which of the two becomes the new root. I personally avoid using autostrut to root for that reason.

On 12/10/2019 at 11:20 PM, strider3 said:

Now when I try to dock the 3rd arm, the station breaks up into 3 large pieces as soon as docking is complete

Does this happen immediately upon docking, or does it wobble itself apart? Does the "F3" menu give any information on what happened?

What could have happened is that the "weldable" connections cause the game to treat the parts as different vessels for a moment before the mod kicks in and re-arranges the craft. If they move far enough apart during that moment then the mod cannot (or does not) "stick" them back together. Struts (regular an d auto-) will not connect parts of different vessels, so they don't help during that moment. Hmmm... actually they could cause the problem: if they held the other parts under tension (like a compressed spring) before the docking, then the release of that tension during them moment of non-connectedness could move the parts apart.

Some things you could try: Disable SAS during docking. Disable autostruts to root (or heaviest) during docking. Try the stock docking ports and not the modded ones. Don't attach the portable struts until all parts are assembled.

But in general: I don't use these mods and I haven't really encountered your problems, so I can only speculate!

[strider3]

23 hours ago, AHHans said:

AFAIK it doesn't really matter. I believe that "to root" and "to grandparent" just don't do anything on the root part, and I don't use "to heaviest" anyhow. For myself I usually just activate "to grandparent" on (nearly) all parts, including the root part.

In general: yes! During docking the two crafts will become one craft with the new root part being the root part of one of the two original crafts. I don't know how the game chooses which of the two becomes the new root. I personally avoid using autostrut to root for that reason.

Does this happen immediately upon docking, or does it wobble itself apart? Does the "F3" menu give any information on what happened?

What could have happened is that the "weldable" connections cause the game to treat the parts as different vessels for a moment before the mod kicks in and re-arranges the craft. If they move far enough apart during that moment then the mod cannot (or does not) "stick" them back together. Struts (regular an d auto-) will not connect parts of different vessels, so they don't help during that moment. Hmmm... actually they could cause the problem: if they held the other parts under tension (like a compressed spring) before the docking, then the release of that tension during them moment of non-connectedness could move the parts apart.

Some things you could try: Disable SAS during docking. Disable autostruts to root (or heaviest) during docking. Try the stock docking ports and not the modded ones. Don't attach the portable struts until all parts are assembled.

But in general: I don't use these mods and I haven't really encountered your problems, so I can only speculate!

This happens immediately upon docking, no wobble at all. I always disable SAS just before docking anything to the station (learned that the hard way on my firsts stations). I disabled auto-strut on the ports and only auto-strut after I've welded the ports, which, at least visually, makes them gone so I can auto-strut girder to girder. This has solved the breaking up on docking issue. The last issue I ran across was these weldable ports refusing to dock. Found that only one of the ports should have any torque in the "roll" setting (this attempts to align the 2 ports so that everything is "square"). If both have some roll torque...no bueno...they just bounce off.

So far, so good. Flying the last arm up now.

Thanks!