Whoops! Mating Docking Ports in VAB = BOOM!?! (Decouple Node, not UnDock)

[JoeSchmuckatelli]

I don't know what I did - but I built a ship of fools (crew module + fuel &big engine) with a lander docked on the end.  Pod had a docking port, Lander had a docking port.  Flipped the lander in the VAB, mated the two docking ports and launched the ship.

Got my refueler up to them - went to undock the lander from the return ship... noticed something odd: no "UnDock" option - only 'Decouple Node'.  

Fun thing: the lander exploded.

Reloaded save.

The lander exploded.

Reloaded save

The lander shook itself madly and exploded.

...

 

So - what did I do wrong?

[Spricigo]

28 minutes ago, JoeSchmuckatelli said:

So - what did I do wrong?

Yes, you didn't provide a screenshot for us to see your design and try to spot the culprit. Without a screenshot, I see nothing wrong.

There is nothing wrong with "decoupler node" instead of "undock" option. That is just how it works, as a regular decoupler (hidden from the staging sequence by  default) until the first activation.

 

[bewing]

Check to see if you have parts autostrutted. Especially across the docking port (Root Node autostruts). That is the most common cause of explosions or shaking on docked craft. Turn off all the autostruts as fast as you can after you focus on the craft in orbit. (As spricigo said, "decouple node" is normal for your first undocking.)

[JoeSchmuckatelli]

4 hours ago, bewing said:

Check to see if you have parts autostrutted. Especially across the docking port (Root Node autostruts). That is the most common cause of explosions or shaking on docked craft. Turn off all the autostruts as fast as you can after you focus on the craft in orbit. (As spricigo said, "decouple node" is normal for your first undocking.)

Okay - that turned out to be the problem; there were some legacy struts from a previous build that did not get deleted.  They did not show up as cross-connecting; but when I reverted to a previous save and deleted the offending struts in the VAB - and launched, reached orbit,etc... I was able to undock and redock all my end stages.

So weird; I thought everything looked good before launching; the struts had to be the problem!