Stock rotating turret help

[Sheiss]

Hey guys,

I haven't been on this forum in ages, decided I would return to KSP to try fix a ship which I got stuck on years ago because of some kraken-like issues. Alas, I got stuck again! I'm not sure where else to turn so I hope you guys are able to help:

I'm building a stock spaceship with a rotating turret. I've gotten the turret to work quite nicely, but whenever I leave and re-enter the session on the ship with the turret, the turret goes flying as soon as I undock it from the ship.

The axle of the turret is created by two rings of Cubic Octagonal Struts around Z-200 Rechargeable Battery banks with an FL-T100 in between to stop the axle from sliding up or down (see screenshot below). It uses an Advanced Grabbing unit to dock the turret with the ship for flight and time-warping. The grabbing unit works perfectly if I don't dock the turret to the ship when leaving a session and load straight back in. The problem with this is the turret then drifts from the ship if I timewarp in another session. Docking the two together prior to leaving the session results in the aforementioned kraken-like disintegration.

If you want to see what I'm talking about, you can get the craft file at: https://www.dropbox.com/sh/u947i804lhyt8aa/AABrxuIIYthtM4u1m4NsmFaxa?dl=0

You'll find the turret slot in the middle of the ship. There's a decoupler along the side of the turret (which is currently just Remote Guidance Unit) that initially connects it to the ship that you'll need to detach once in flight (you can see the decoupler on the right side of the screenshot below). You'll find the grabbing unit below the turret which you can arm to connect the turret to the ship. I then usually timewarp to get the decoupler to float out from inside the ship. You'll obviously need to cheat the ship to orbit to test this as I haven't included a launcher.

I've also tried a variation with a Clamp-o-tron Shielded Docking Port instead of the grabbing unit, but with this I can only seem to dock and undock it once, then it refuses to reconnect the turret.

Thanks for reading, looking very much forward to your responses!

 

[OHara]

I think the only solution (for what people call 'kraken-tech' bearings) is to make the re-joining so easy that you can do it anytime you switch craft.

I built a similar bearing for https://kerbalx.com/OHara/Tough-Twin-Electro-Prop, with the spherical collider of the grabbing unit serving as part of the bearing.  There is a mod 'Collide-o-scope' (link) that outlines the shapes used as colliders by the physics engine, which helps line things up correctly.  On one end of the moving part, a cage of thermometers surrounds the grabbing unit; on the other end an antenna sits inside a cage of RCS ports.

Normal docking ports need to back away a few meters before the re-activate their magnets and auto-engage features.  Quitessa used shielded docking ports for their re-dockable bearing at https://kerbalx.com/quitessa/Fully-Redockable-Bearing (which uses parts from the Making History mod).

[Sheiss]

On 4/13/2020 at 3:47 AM, OHara said:

I think the only solution (for what people call 'kraken-tech' bearings) is to make the re-joining so easy that you can do it anytime you switch craft.

I built a similar bearing for https://kerbalx.com/OHara/Tough-Twin-Electro-Prop, with the spherical collider of the grabbing unit serving as part of the bearing.  There is a mod 'Collide-o-scope' (link) that outlines the shapes used as colliders by the physics engine, which helps line things up correctly.  On one end of the moving part, a cage of thermometers surrounds the grabbing unit; on the other end an antenna sits inside a cage of RCS ports.

Normal docking ports need to back away a few meters before the re-activate their magnets and auto-engage features.  Quitessa used shielded docking ports for their re-dockable bearing at https://kerbalx.com/quitessa/Fully-Redockable-Bearing (which uses parts from the Making History mod).

 

Thanks so much OHara. I've taken quite a thorough look at your craft and fiddled a bit with mine on Collide-o-scope, but am still not quite sure why yours doesn't spontaneously disassemble when disarming the grabbing unit after reloading into the session. I also tried replicating your rotor as the basis of my turret, but I am unable to translate things like the RCS port cage far enough away. Is there some trick I'm missing?

Also, apologies that the craft file was modded. I thought I removed the Mechjeb unit, but apparently not. I've created a bare minimum Turret Test craft file that is definitely mod-free for you to look at: https://www.dropbox.com/sh/u947i804lhyt8aa/AABrxuIIYthtM4u1m4NsmFaxa?dl=0

It seems that whenever my rotor Krakens-out its the internal Cubic Octagonal Strut and lower Z-200 battery that go flying.

[OHara]

On 4/14/2020 at 2:39 PM, Sheiss said:

I am unable to translate things like the RCS port cage far enough away. Is there some trick I'm missing?

Hold left-shift while you drag a part, in order to drag it further.  For some reason KSP hides that trick well.

Somehow, after a quicksave/quickload (or going to another ship and back) with your Turret Test, when I next release the claw, the one cube tucked inside the small battery, that was meant to be part of the rotating section, is left behind with the static section.  So the physics engine acts as if a collision had violently pushed that cube inside the battery, and tries to elastically spring back.

The only way I saw what was happening was by noticing which parts of the debris were connected to each other.  (Mythos's stand-alone utility flags an error on the persistent file when your craft is loaded, about that cube not being connected properly to its parent, but not on the craft file itself.) 

I have never seen a problem like that before.  I hope that if you partially disassemble and reassemble the craft, whatever problem sneaked in there will not come back.  I suspect you were extremely unlucky to find a glitch in the craft data structures.

Edited April 19, 2020 by OHara
link to Mythos' thread