Docking / Undocking Issue - Why ???

[LordFerret]

Ok, I made a part for my space station. I fashioned it after something I'd seen someone else do. Why does it not work for me? After launch, in orbit, I went to release the part from the triple-dock, and the docks fell apart. Am I missing something here?

https://picasaweb.google.com/lh/photo/hM4ltIjt5rGE_u83fzXeL6LAf-j_PeS7XmiuyE5WpdU?feat=directlink

Edited August 4, 2014 by LordFerret
tried to fix image post issue

[Master Tao]

You are missing something, and it is totally not obvious. It took me a minute to figure it out, and I've been poking around in the craft file structure since the first week I started playing KSP.

Just to double check, is this how you assembled your docking ports in the VAB?

• placed a tricoupler
  
• added docking ports in 3x symmetry
  
• added docking ports to those in 3x symmetry onto those
  
• placed a tricoupler onto the second set of docking ports
  

The problem here is that in KSP when you're placing a part, it can only attach to one other part. In other words, adding 3 docking ports is fine – that's 3 ports that each attach to one part, which happens to be the same tricoupler. For the second set of docking ports, that's fine, too – 3 ports, each attaching to 1 docking port (all different ports). It breaks down when you add the second tricoupler – the tricoupler can only attach to one docking port, so the game picks one; the other two are only attached to the opposing docking port, not the new tricoupler.

The only way to make that work is to launch the station pieces as separate crafts, then dock them in orbit. You could also replace the three docking ports with a larger port. Or you could just skip the docking ports entirely, since clearly you can get the whole assembly into orbit at once.

[Master Tao]

Actually, there are a couple of ways to make this work as one craft:

1. Build the second tricoupler & docking port assembly and put it in a subassembly, then attach it to the first set.

2. Don't use symmetry. Start by placing one port on the first tricoupler, then another port facing it. Add the second tricoupler to that port, then add the two remaining ports to the second tricoupler. Pull the tricoupler off (two of the docking ports will come with it) and place the remaining two docking ports on the first tricoupler. Finally, replace the second tricoupler.

Neither of these methods will let you have multiple attachment points until you redock in orbit like you'd planned, but they will at least let you get it to orbit in one go.

[LordFerret]

Yes, the piece I put up was fairly large, which is why I tried the tricoupler thing for 'strength'. Yes, I constructed it just as you described. I'll suppose the dual-coupler would have the same problem then (another idea I'd been toying with). I don't have the larger docking ports available yet (career mode). I'll have to work on that.

Thanks, I'll play with those suggestions.

[allmhuran]

If you want a detailed description of how to do what it is you're trying to do, check out this quick tutorial. It's nominally about making "engine clusters" but it's really a tutorial on how to go about creating multiple docking port connections in the VAB:

http://forum.kerbalspaceprogram.com/threads/43621-How-to-have-engine-clusters-in-upper-stages?p=558242#post558242