Docking ports just will not connect

[Dungas Kerman]

Hello,

 

I'm trying to dock my Laythe lander with the mothership on a 100km stable orbit around Kerbin. 

 

I've tried 6-7 times (different saves, not docking attempts, those are in the 100s by now) and they just will not connect. I have no idea what is going wrong.

The alignment is perfect,

The ports are correctly positioned and the same size,

I've tried different approach speeds but nothing works,

I tried backing off 100m and trying again,

I tried rebuilding the docking port (interstage node on a fairing),

I tried turning on SAS on one vehicle and both vehicles,

I tried saving and starting from either launch,

I tried crashing the lander and launching another,

Neither vessel was previously docked to anything,

...

The most infuriating thing is that when I clicked through the docking port options I saw there was an "undock" option, which is weird because it's not docked to anything but ok. When I clicked it the upper part of the docking port fell off, bounced of my spaceship and then DOCKED ITSELF TO THE LANDER PORT.

 

Anyone got any ideas? I'm all out.

 

[18Watt]

Screenshots would  be helpful.

The fact that when you clicked ‘undock’ the docking port fell off indicates that you have installed at least one docking port backwards.  It’s difficult to know without screenshots though.  

[swjr-swis]

2 hours ago, Dungas Kerman said:

when I clicked through the docking port options I saw there was an "undock" option

This is a dead giveaway for the root cause: this means that the docking port has been attached to the ship by its front docking node, instead of the back one. Since that front node is not free to use, it won't dock.

 

2 hours ago, Dungas Kerman said:

I tried rebuilding the docking port (interstage node on a fairing)

And this is the second part of the puzzle. Fairing interstage nodes always come in pairs, almost overlapping, pointing opposite of each other. Add to that a part that also has its front and back nodes very close to each other, like a docking port, and it's very easy to get those attached incorrectly. Always check and double-check in such cases.

You may still be able to correct this in flight with EVA construction, if there's not too much clipping involved. otherwise back to the VAB/SPH and reconnect them properly before launching again.

[Dungas Kerman]

I did not know that. Thanks for the explanation  

I'll try the EVA construction thingie and if it doesn't work I'll just crash it all and start anew

[18Watt]

On 7/4/2022 at 6:19 PM, swjr-swis said:

Fairing interstage nodes always come in pairs, almost overlapping, pointing opposite of each other. Add to that a part that also has its front and back nodes very close to each other, like a docking port, and it's very easy to get those attached incorrectly.

Ah yes, I knew the fairing was another piece of the puzzle, but couldn’t remember why.  Good catch!