Magnetic Docking Port

[Mr Shifty]

Curious if anyone knows a way to add a docking port to a vessel that's already in orbit. KAS has those cool magnetic winch attachments. Can those be used for docking? What I'd like to do is move one of my station components from where it is to another location on my station using a tug. But there's currently no place to attach the tug. I use and love mods, so a mod solution is just fine.

Edited August 31, 2013 by Mr Shifty

[Geschosskopf]

The only things that KAS can use for docking (as in transferring fuel between ships) are the connector ports. If the ship does not already have one installed, you'll have to use the dismountable port. So, you build a ship with a winch and a dismountable port somewhere a Kerbal can reach it. The Kerbal goes EVA, grabs the dismountable port, flies over to the other ship, and attaches the dismountable port to it. Then he flies back, grabs the winch cable, returns to the other ship, and connects the cable to the dismountable port.

[Geschosskopf]

Whoops, misread your question. You want a tow truck, not docking for the usual reasons.

OK, I'm assuming that if the module can come loose from the station to be moved, it's got 1 docking port. Thus, if you put a tug on that to move it, you have no docking port left to reattach it to the station. Is that correct?

In this case, you CAN use KAS to solve the problem. It would go something like this:

1. Send up a new module that will dock to the port you want the module to be at. This new module has a KAS winch on the other end and carries at least 1 dismountable port.

2. EVA a Kerbal and have him attach the dismountable port to a convenient spot on the module to be moved.

3. Uncouple the module to be moved and move either it or the station itself far enough away to squeeze a tug in between them.

4. Dock the tug to the loose module and move it over near the module with the winch. Get it VERY close to its intended position and oriented the correct way so you don't have to move it very far or pull it in any direction but straight towards the winch. Otherwise things will go rather badly.

5. EVA a Kerbal and have him attach the winch cable to the dismountable port on the loose module.

6. Reel in the winch. If the module moves straight in to the winch without having to rotate or translate, then all should be well. The winch will lock up solid and you'll be totally docked for all intents and purposes. Then you can undock the tug and have the module's docking port sticking out for later use.

Now, if this module totally lacks docking ports at all, 1st there's the question of how you'll detach it anyway. But assuming it's on a separator or something, then the problem is a little more interesting. You'll still need a new winch module as above, and still need to put a dismountable port on the loose module. But in this case, you'll have to maneuver the loose module into position via a careful combination of reeling in the winch and pushing it with an EVA Kerbal. If you just reel in the winch, the module will move in a direct line to the winch, smashing into whatever's in it's path. And then, when it gets to the winch, it will be moving in the wrong direction to lock up so will swing around wildly, either smashing into something or breaking the winch off. So, push a little with the Kerbal, pull a bit with the winch, repeat, until the module is holding still right in front of the winch and will move straight in at it to lock up.

[Mr Shifty]

You want a tow truck, not docking for the usual reasons...<snip>

Wow, thanks! That's a perfect step-by-step. I'll give that a try later.

EDIT: For some reason, my rep-giving button isn't working, but I'd like to send some your way.

[Geschosskopf]

EDIT: For some reason, my rep-giving button isn't working, but I'd like to send some your way.

Wow, you're one of my KSP heroes so this is a big compliment. And it's the thought that counts anyway .

I should also add that you should always F5 before connecting the winch cable. Sometimes, but not always, connecting the KAS cable to a port in docked mode causes a phantom force to be applied to the ship on 1 or both ends of the cable. It's like the cable is pulling inwards on both ships like it's a rubber band, but something else is keeping them from moving towards each other, so what you get is a severe torque that rotates the 1 or both ships somewhat towards each other. And this condition doesn't go away when you detach the cable, so your ship(s) is pretty much hosed after that.

Fortunately, there's a prophylactic measure you can apply to avoid this. What you want to do is create a lot of slack in the cable. You will not see this slack in the game--the cable is always drawn as a straight line from winch to port--but you can tell it's there by comparing the target range icon to the length of the cable displayed at the top of the winch's right-click menu. In general, the ways to achieve slack (if you don't belong to the Church of the SubGenius) are as follows:

1. Unless you tweak the files, the cable is 50m long. So make sure your ships are way less than 50m apart. I like about 5m separation myself .

2. Release (not extend, not eject) the winch cable before the Kerbal grabs the end of it. In space, this sometimes means you'll have to go chase down the end of the cable before you can grab it but usually it doesn't go very far so no big deal. Sometimes in space the cable goes shooting off like you ejected it so if you have to grab the cable prior to releasing it. But if so, be sure to release the cable after you grab the end, so the Kerbal moving the end is pulling out slack instead of building up tension.

2. Once you get close enough to the target to connect the cable, stop and extend the cable another 5-10m or so just to be doubly sure you've got beaucoup slack.

3. Connect the cable in UNDOCKED mode, then disconnect and grab it again.

4. Connect the cable in DOCKED mode and hope for the best .

Edited August 31, 2013 by Geschosskopf

[Mr Shifty]

Wow, you're one of my KSP heroes so this is a big compliment. And it's the thought that counts anyway .

Wow, I'm flattered! Thanks for the further tips. I'll let you know how it goes.