Well that's a new bug...

[technion]

Hi,

Have a look here. This mothership had four radially mounted probes. Two have already left.

I decouple one and.. it takes the engine from an adjacent tank with it.

Well this I wasn't expecting.. with a gap from my probe, it actually thrusts when I run the engine.

Yep, if I quickload and launch the other probe instead, it just takes off without an engine.

Is there a hope in the world of fixing this?

[Snark]

Is it possible that this was a build-time issue in the VAB? One annoying thing that happens to me all the time in the VAB is that they have a feature that I never, ever use on purpose, which is to turn on "symmetry around parent part" rather than "symmetry around ship." It's toggled by F. It seems to come on all the time in symmetry x2 situations when I don't intend it, and hilarity ensues.

Is it possible that when you were placing these things, they somehow got attached to the same radial decoupler?

If you still have the .craft file from when you saved that ship, it might be interesting to take a look at the parts and see what the parenting looks like on those xenon fuel tanks-- for example, is it "correct" (i.e. each xenon tank is parented to its own radial decoupler), or munged (more than one tank parented to the same decoupler)?

Alternatively, if this is a runtime problem, what mods are you running? I assume you haven't done any manual tinkering with the .sfs file or you would have mentioned it?

[technion]

Mods:

Kerbal engineer

Kerbal alarm clock

It's a 99% vanilla install, and I haven't manually edited anything. I guess I can't rule out a build problem but I placed those probes with 4 x symmetry, and two of them launched just fine.

Craft file below:

https://lolware.net/kerbal/Probe delivery.craft

If you can advise how I check these issues you referred to I'd be happy to review and advise.

[technion]

Well for the record, SAS is entirely capable of holding a probe stable even when firing such an offset ion engine. I've basically gone and completed the rest of the mission, and poor pol never got a probe because it was engineless.

[cantab]

Yeah, I've found that sometimes in the VAB a part can appear to connect somewhere, but actually be attached to a different parent part I wasn't expected. When you hover over any part it and its children will be highlighted, and you can use that to check your craft's "topology".