1.12 decoupling docking ports?

[jimmymcgoochie]

In the middle of a mission I've suddenly realised that a key piece of hardware- an ion-powered space tug- is attached to the mothership by a small docking port which is surface attached. The Ion Space Tug was attached as a subassembly in the VAB when the mothership was launched but now it can't be decoupled, undocked or otherwise detached; the undock button does nothing and there's no option to decouple in the PAW or via action groups.

Is there a way to get this docking port to let go, or do I need to resort to dubious save hacking to either forcibly detach it or else destroy the docking port and fix it afterwards via EVA construction?

[king of nowhere]

6 hours ago, jimmymcgoochie said:

In the middle of a mission I've suddenly realised that a key piece of hardware- an ion-powered space tug- is attached to the mothership by a small docking port which is surface attached. The Ion Space Tug was attached as a subassembly in the VAB when the mothership was launched but now it can't be decoupled, undocked or otherwise detached; the undock button does nothing and there's no option to decouple in the PAW or via action groups.

Is there a way to get this docking port to let go, or do I need to resort to dubious save hacking to either forcibly detach it or else destroy the docking port and fix it afterwards via EVA construction?

I have bad news and good news.

the bad new is, it's a know bug, and indeed there is nothing to be done, except hacking the save.

the good news is, it's a predictable and reliable hack, and somebody made a tool for it.

check this kml editor, it can edit save files in many ways, and it does fix broken docking ports.

I never checked its other functionalities, but I did use it to save my own mission when I had this bug myself, and I can attest that it is reliable, it works just fine, and it does not mess up anything else.

 

Also, if you destroy the docking port with the intent of fixing it later with eva construction, there is a good chance that breaking a broken docking port will crash the game.

[18Watt]

I’ve had that happen to me, and always in circumstances similar to what you described.  I suspect that when attaching subassemblies radially (surface attach) that sometimes I have managed to get the wrong part attached, or somehow clipped two parts together which prevents the decoupler from working.

In any case, as @king of nowhere said, there is not a good way to fix the issue in stock KSP.  I ended up separating the two ships using the object thrower to blow up enough parts that the ships were no longer attached.  That is far from a good solution.

The editor @king of nowhere suggested might be worth a try.  Although if you managed to somehow attach parts like I did that may not fix your problem- because in my case the docking ports worked fine already, the problem was that the girders behind them were actually the parts which were attached, not the ports like I had intended.

I now do a test of radially attached subassemblies on the launchpad, to make sure they separate as intended.  Good luck!

[Superfluous J]

Another option is the mod Kaboom. Using it you can in-game destroy a single part. If you do that to one of the 2 docking ports, that will effectively decouple your probe from the ship. Of course, you'll lose the port on the ship or the probe (depending on which you destroy) so it may take some creative mission restructuring to get around it. But as far as fixing the problem, I've found it to be a very easy option to use.

 

[Geonovast]

The "Set Primary Docking Node" button in the PAW was supposed to help combat this bug.   I've seen pretty mixed reports about it working.

[jimmymcgoochie]

To clarify:

The problem docking port is NOT attached to another docking port. It's attached directly to another part (an NFLV 5m cargo bay) on the top node (the end that docks to other docking ports).

[jimmymcgoochie]

Good news- after much save file hacking using KML (and a few gratuitous explosions) I finally freed the stuck docking port by setting it to 4000 degrees Kelvin and blowing it up, then replacing it with a new part which I copied from another part of the same mission and then fixed with a bit of EVA construction.

After all that effort, actually landing on Eve should be a doddle, right?