Double Docking

[MisterKerman]

I was just wondering if it's possible to dock 2 seperate craft together using 2 different docking ports on each craft simultaneously. (4 total) I don't think you could do it in older versions but I'm not sure which version it was when I last played and would prefer a knowledgeable person to save me some sleuthing if they would be so kind.

It seems like something that really ought to be in the game, but I could see how there would be control issues unless the detachment was assigned to an action group to "let go" at both points simultaneously. Either that or stagger the decoupling to delay until all connected ports have been told to decouple.

[bewing]

Yes, multiple docking ports have been able to dock simultaneously since back before version 1.0, I think. It hasn't changed.

 

[MisterKerman]

15 minutes ago, bewing said:

Yes, multiple docking ports have been able to dock simultaneously since back before version 1.0, I think. It hasn't changed.

 

Beautiful. I remember it not being an option since I last played so you just saved me looking through god knows how many changelogs. Thanks a bunch.

[Zhetaan]

@MisterKerman:

I believe that multi-docking has been available since docking ports were introduced.  They are the only stock way to build ring stations and branched stacks that reconnect, such as a bicoupler used to make a double stack of fuel tanks that then reconnect to a central stack with another bicoupler.  Multi-docking was once also a practical stock way to get (mostly) rigid connection between parts of longer assembled-in-orbit vessels, such as Grand Tour motherships and the like, before autostruts existed.  It is still the only stock way to get guaranteed alignment of station parts (I know several OCD KSP players who go into shivering fits over a two-degree misalignment of a station module).

I don't think it's ever been advertised as a feature; every vessel in KSP is built on a branching tree (hence the name root part) structure that doesn't allow crosslinks.  Everything in the tree has to have exactly one connective path back to the root part, which is why people who try the double-bicoupler trick I mentioned before, but without docking ports, end up very unpleasantly surprised when one leg wobbles into oblivion because it's not connected to anything.  Imagine what happens with quadcouplers: three legs are disconnected.  I believe that docking can get around this because the docked vessel has its own root part and thus its own tree; the two trees can see and link to one another, but each connected docking port is still at the end of its particular branch.

[MisterKerman]

On 7/20/2018 at 7:56 AM, Zhetaan said:

@MisterKerman:

I believe that multi-docking has been available since docking ports were introduced.

[snip]

Like, I'm glad it's possible and all, but you're sort of also blowing my mind here. I'm positive I've tried before and it simply wouldn't work. I would have bet a child that it never used to be possible.

It's probably a good thing I don't have kids...

Edited July 22, 2018 by Vanamonde

[StrandedonEarth]

I know I've done it pre-1.0, I think around 0.24 or so. But the alignment has to be perfect for it to work, which is why I used NavyFish docking alignment indicator when I did it.

[Vanamonde]

Mind the language, please. 

[Zhetaan]

On 7/20/2018 at 8:30 PM, MisterKerman said:

I'm positive I've tried before and it simply wouldn't work.

@StrandedonEarth is correct; you have to be very precise in your docking to make it work.  If one port acquires and docks while the other is rotated three degrees out of alignment, forget it.  You may be able to mod the docking ports for weaker magnets that activate when you are close enough to aligned that they help you rather than drag your parts into skewed orientations, but the only practicable solution is to become so skilled in your docking in the first place that you achieve simultaneous acquisition.  That's easier with docking mods but certainly possible in stock.

It's said that docking is one of the most difficult skills to learn in KSP.  Don't be surprised that multi-docking squares that level of difficulty, but don't let that intimidate you, either.  It's been done before, so you can do it, too.

Edited July 23, 2018 by Zhetaan

[farmerben]

It took me a while to become proficient at docking, but once I had it I immediately built and array of triple docked connectors to hold 9 big orange tanks together in a rectangle, in stock KSP.

This is a trick I don't always use anymore, but it sure makes things simpler:  Align the vessels normal and antinormal to the orbital plane, and lock them there with SAS.  Use side thrust to bring the target marker onto the normal marker, before approaching the target.

Make the final approach at about .2 m/s and multiple ports should go magnet crazy before any one connects.  If one fails to connect its pretty easy to back up, rotate, and come in again.  

Edited July 25, 2018 by farmerben

[ExtremeSquared]

In old versions, the joints weren't locked, but the second set of ports still provided strength through collision/attraction. Closed loops were impossible in general for a while.