Tug-docking engine modules radially

[RSwordsman]

My forum search turned up nothing so far. I have perfected normal straight-on docking with a tug craft for building ships in orbit. However, I am not confident in assembling pieces on the sides of the ship so they are in line with the rest of it.

It seems I need at least 2 connection points for each module to make sure it's straight. Easy enough to line docking ports up in the VAB with angle snap. But is there an efficient way to do this that doesn't involve an obscenely huge launch vehicle and putting my five-stack propulsion module up in one chunk? I can't seem to figure it out without putting unsightly RCS blocks all over everything.

EDIT: I just remembered what's essentially a "bar stool" design for the tug, with the main body serving as host to four long RCS-equipped limbs that reach down over the module to be maneuvered. I do have a semi-functional version or two of this, but would probably need a new one. Would this be my best bet?

Edited April 12, 2014 by RSwordsman

[cantab]

I'm not sure what you're asking here.

In terms of construction, if you want to dock two stacks parallel then this diagram shows what you need to accomplish:

crude_diagram by cantab314, on Flickr

There are two ways to do this. Simplest and most flexible would be to place the HubMax six-way connectors in the stacks. For a more streamlined option, take a fuel tank (or any stack that will be common between the core and all your likely boosters), attach docking ports radially near the top and bottom, and save it as a subassembly. Then always use that subassembly when you want the docking ports.

For the actual docking, it's a bit trickier than normal docking since you need to match orientation so that both docking ports connect at the same time. (If one connects first, the other will not dock even if it comes close.) But it's entirely doable.

[Epthelyn]

You don't need 2+ connectors to make it straight, it just makes it a lot easier because you can see what in-line is; you can, with a little patience and a balanced craft, dock perfectly in-line with a single docking port. As cantab said, it's just a normal docking but with an extra orientation, which is pretty tricky if you attempt the docking from a focus point parallel to the target piece.

However, it's much easier if you "control from here" on the docking port. Just line up the craft as you would for a normal docking but remain stationary (relative) a very short distance away and then rotate as necessary. Adding a few ASAS modules to whatever you're docking is amazingly helpful to lock the rotation once that's done, because unless you've perfectly balanced your RCS thrust you will have moved away and moving back might try to rotate again.

It takes a little practice, but 'normal' docking does too

[RSwordsman]

diagram

That's exactly what I'm asking. I can imagine it will be a bit tricky, but I should be able to do that much with the way you said, saving each module as a subassembly. As for the actual nuts and bolts of the tug design, do you recommend anything else as far as maneuvering goes? It's sort of hard to move an inert module sideways without putting ports on it (reaction wheel muscle or RCS outriggers are my other plans), and I'm trying to keep the excess parts to a minimum.

Edited April 12, 2014 by RSwordsman

[cantab]

Either add a third docking port to the radial boosters allowing a tug to shift them, or use a claw-equipped tug to do the same, or mount the manouvering equipment on decouplers or docking ports then jettison it afterwards.

[RSwordsman]

Either add a third docking port to the radial boosters allowing a tug to shift them, or use a claw-equipped tug to do the same, or mount the manouvering equipment on decouplers or docking ports then jettison it afterwards.

All good ideas. Come to think of it, the tugs I have in orbit right now were made before the update, so it would be wise to put up new ones with claws hehe. I've also thought of the decoupler idea but haven't gotten around to doing it. But I think I have enough information and emotional support XD Thanks for the replies.

[Pecan]

This tractor (tug) is has sufficient RCS fuel and liquid rockets to manoeuvre itself but not much else. It is designed to have fuel and more powerful engines, as well as the payload, docked beneath or on top of the outriggers, as the mission requires. Using this eliminates the shear forces on vertically-mounted docking ports (not that I know whether that would be significant ^^) and allows for easy fuel-load, thrust and push/pull adjustment.