Using multiple docking rings

[Dreamkruiser]

I am constructing a three ship vessel so I can complete 3 Duna contracts with one Duna window but I can't send up everything at once so I am assembling everything in orbit. I would like to attach multiple nuclear engine/fuel pods radially since linear doesn't make sense on a vessel that's 75 meters long... I would prefer to prefab these engine units using symmetry of 4 then decouple the center in orbit creating a donut then slip it over my Duna vessel. I have concerns about this working because I used 2 rings to attach two modules together on a different vessel and only one docked correctly and at a slight angle which is why I want to prefab this engine donut, to ensure all engines are parallel to each other. There lies the largest issue though, how do I get all 4 rings to connect and if impossible, how do I dock the engines 100% parallel to the main vessel. I also do not have a leveled engineer in case you wanted to bring that as an option. Thank you

[StrandedonEarth]

You don't say if you are on console or PC, and if the latter, if you use mods. If you can use mods, then there are two docking port alignment indicator mods available to help you get the rotation aligned perfectly. The first one just sits on the navball, and the other has it's own window with more info available. Either will work to help get twin docking ports aligned properly.

But if I read your post right, you're trying to dock into the center of a donut? I've never tried that so I don't know if that is possible or how easy it is. Or how hard it would be to even undock from a ring. You may be better off double-docking them separately, although more time consuming.

Good Luck!

[Snark]

22 hours ago, Dreamkruiser said:

I would like to attach multiple nuclear engine/fuel pods radially since linear doesn't make sense on a vessel that's 75 meters long... I would prefer to prefab these engine units using symmetry of 4 then decouple the center in orbit creating a donut then slip it over my Duna vessel. I have concerns about this working because I used 2 rings to attach two modules together on a different vessel and only one docked correctly and at a slight angle which is why I want to prefab this engine donut, to ensure all engines are parallel to each other.

Getting this to work perfectly is, in my experience, virtually impossible unless you use mods specifically dedicated to the task.  (For example, I've seen mods with docking-port parts that are designed to have "angle snap" built in, so that they're self-aligning.)

Another option, which saves you from the requirement of having to try to perfectly line everything up parallel with radial engine pods... what if you use linear ones, in the front?

That is, let's say you have some big long thing, and you want to attach multiple LV-N's to it.  Have a single docking port on the front of your big long thing.  Your "engine module" has a single docking port on the back, and then it has however-many LV-N engines you want, on pods that are mounted sticking way out to the side (e.g. using girders or wing connectors or something).  So the engines aren't pushing the long craft, but pulling it.

It works and is nicely stable, even if your long craft is "floppy" due to having multiple components docked one behind another, train-fashion.  And will work on arbitrarily long craft.

Just an alternate approach to the problem. 

[Kryxal]

7 hours ago, Snark said:

Getting this to work perfectly is, in my experience, virtually impossible unless you use mods specifically dedicated to the task.  (For example, I've seen mods with docking-port parts that are designed to have "angle snap" built in, so that they're self-aligning.)

Another option, which saves you from the requirement of having to try to perfectly line everything up parallel with radial engine pods... what if you use linear ones, in the front?

I used a similar design for a Jool-5 mothership, NERVs on outriggers and in the center a single orange tank with a senior port.  It meant I could attach whatever I needed to it.  As I recall, I set it up to have a couple of landers tucked in to be pulled as well...

[OHara]

On 4/5/2019 at 2:44 PM, Dreamkruiser said:

I would prefer to prefab these engine units using symmetry of 4 then decouple the center in orbit creating a donut then slip it over my Duna vessel. I have concerns about this working

You have reason for concern. Coupling the donut to the Duna vessel will be difficult.
Multiple docking ports do couple if they all align simultaneously, but only one is full-strength.  I do not enjoy using multiple docking ports that need to connect simultaneously. 

As Snark said, you can make a module that goes in-line, holding the radial engines, and put it wherever you like in a stack without adding too much to the length.  I made a picture.

It is also reasonable to dock your engines radially, with individual docking ports, and just not worry about the misalignment angle.  You will not lose too much in efficiency.

Or if you play on a PC, you can mod the game to make the docking ports snap their rotation angle.  This feature was built into KSP, but is not enabled, so the only mod needed is Module Manager and a *.cfg file somewhere in /GameData/ with the text in the spoiler below.    This, and many other minor modifications that players have suggested, are found in the thread here.

Spoiler

@PART[*]:HAS[@MODULE[ModuleDockingNode]:HAS[~snapOffset[]]] {
	@MODULE[ModuleDockingNode] {
		acquireForce = 0.5
		//acquireTorqueRoll = -0.2
		captureMinRollDot = 0.9998
		snapRotation = true
		snapOffset = 90
	}
}

 

 

Edited April 7, 2019 by OHara

[Dreamkruiser]

Thanks for the advice, and thank you OHara for putting up a pic. I realized shortly after asking, this would be an acceptable solution. Sorry it's been a few days but I've had to work on other contracts since these 3 are breaking the bank, I can't wait to put up a shot of this ridiculous vessel. One more concern about the same project, when I dock the two engine modules I'll be building, how do I ensure rigidity because docking rings flex a lot, like I said it's 75 meters long and when it's all assembled I'll have about 6 rings. I don't really want it "slithering" to Duna or succumb to the Kraken

[bewing]

Turn on "Advanced Tweakables" in your settings, then Autostruts or Rigid Attachment after you've docked.

 

[Dreamkruiser]

Autostruts work after VAB? Which setting would I use since they are in line with each other?