Help with dockig

[Trakt]

Hi, I need some help with docking. I assembled a space station in Kerbin orbit, but now I'd like to tow it to a Munar orbit. The problem is, I can't seem to get my towboat to dock with the station: I get the docking ports within a meter, but the magnetic clamps don't seem to kick in. However, when I rightclick on the port and choose to decouple the node the magnets suddenly work and the station becomes the prud owner of a new probe core. What am I doing wrong?

Pictures of try #63:

https://drive.google.com/drive/folders/0Bzx5rWa7zB_rRUw5dXFMRktIaEE

I'm only using Scatterer, Kerbal Alarm Clock and KER.

Thanks!

[Magzimum]

It is my experience that the heavier the ship, the better aligned the docking ports need to be. In your pictures, the docking ports are close enough, but they are quite a few degrees off the perfect alignment. 

Try to align them better when you approach. I also struggled a lot with this, but I found out that the trick that made it easier for me was to put RCS evenly distributed around the center of mass - that allows you to use the IJKL keys to translate the ship. Then you can just align the ships (e.g. turn both to 'normal' or 'antinormal'), and translate it until the docking ports are on the same line. My recommendation is to do this one axis at a time (first only JL keys, until that's aligned, then IK keys until they too are aligned, then some fine-tuning - again one axis at a time - if necessary). After you achieve that, it is just a matter of moving forward. 

I am not sure I understood your comment about what happens when you decouple - do you mean that you decouple a small part of the larger tug, which then suddenly docks without problem? That would be in line with what I suggest: that smaller part is a LOT lighter, and the docking ports can pull that into alignment. 

[edit] Obviously, when RCS is not distributed around the CoM, you can still translate, but that will also cause a rotation on the ship. This rotation can then be prevented by just putting a lot of reaction wheels on the ship. But that is really just a medicine for a problem that you can easily avoid. 

Edited October 23, 2016 by Magzimum
adding another comment

[Hydrothermalventclam]

I agree, it looks like your docking ports are not aligned well.  On smaller ships, this is not as important, because the magnets can pull your ships into the right orientation, but with larger ships you have to be super exact.

[Trakt]

Thanks for the replies, but they don't even engage when they actually touch, without an angle (I put some better pics up). Tried to disassemble the station, dock with a small (5ton) module first, but it still didn't budge. I'll do some tests to see if it's a problem with the design (I think I read somewhere that clipping issues can make the ports not think they're on top of the rocket), but if it persists, I might deorbit the lot and assemble a new station already in position.

[Speadge]

8 minutes ago, Trakt said:

Thanks for the replies, but they don't even engage when they actually touch, without an angle (I put some better pics up). Tried to disassemble the station, dock with a small (5ton) module first, but it still didn't budge. I'll do some tests to see if it's a problem with the design (I think I read somewhere that clipping issues can make the ports not think they're on top of the rocket), but if it persists, I might deorbit the lot and assemble a new station already in position.

u could try to check the save-files if the docking-ports are "bricked" somehow - this could happen in some situations.

When they are all unassigned to a counterpart, all that could cause the problems is bad maneuvering
Edit: and try to disable SAS when u are sure that they are perfectly touching. SAS might cancel any magnetic forces acting on your ship

Edited October 23, 2016 by Speadge

[DD_bwest]

do both ships have pilots and or SAS?    i always just make sure both have it, so they can point at eachother for you.    I've noticed that if you engage SAS on one and switch to the other, the first ship will keep aiming at the target like you told it, unless you switch back to it, and it will revert to stability assist.

if they both point at eahother, the alignment is never off..

 

and as mentioned just above,   when you are that close, like in the photo ending 11009_1    turn off your sas and rcs, they can fight the docking claps.

[Trakt]

Finally found the problem (that was an afternoon well spent ). There was a part underneath the port that clipped slightly through, making it think it was somewhere in the middle of the ship.

So, yeah, I learned another thing I shouldn't do, but at least this time there was no Jeb stuck in a deorbiting command pod without a parachute

Thanks for the help, my docking game got a lot of practice today.