Orbital assembly of multi-probe interplanetary ships

[Vat]

Came back to KSP a few days ago (combo of uni and GTAV) and started working on something I'd been meaning to do for a while - put an interplanetary transfer platform into orbit, and then launch four landers to rendezvous and dock with the platform.

Worked out issues with resetting the staging, and then decided to move the now load platform to a higher orbit (from 80k to just over 500k, mostly for warping for potential alignments but also to get an idea of how the platform performed loaded) - problem is, I'd docked the landers perpendicular to the long axis of the platform so the moment thrust was applied they proceeded to bounce around. Not enough to break the docks, mind you, but enough to get a good oscillation going and eventually lead to the entire platform spinning. The landers are at the end of long struts, so any movement is going to be pretty leveraged, and whilst the boosters are in a similar configuration (basically an X shape) they're inside the landers which is doubtless worsening things.

I'm having a think about redesigning the platform, but was wondering what other people had done on this front.

One thought that came to mind was to dock the landers from underneath, so they're in line with the axis of the main platform. I could try sitting them closer to the central axis, but that will make docking trickier. I could also try docking them from the side, so they're closer to the central axis, but again they will move under thrust. Double docking ports also came to mind, but I suspect they'd be a catastrophic PITA to build and dock with.

The landers themselves are fairly weighty and could probably do with some weight off. I was thinking of sitting the main platform somewhere off Jool and sending the landers in, so there would need to be capability of doing that. I might send a regular one probe mission to Jool to about where I was thinking and seeing what I could get away with lander-wise.

[Alexandicity]

I'm looking to do something similar myself soon so I'll be watching for replies here!

Two ideas I've seen tossed around before:

* Put your thrust at the front of your platform (so it "pulls" the assembly). Apparently this is more stable or something?

* If the oscillation is definitely coming from the docking ports, use triple-docks and/or quantum struts (mod); both of these give rigidity.

Maybe someone else has hands-on experience with these can comment?

[Seret]

Can you post a screenshot?

[Captain Sierra]

Tow configuration. Two things are happening.

1) Your center of mass is dangerously close to the center of thrust, perhaps even behind it, causing engine gimballing to worsen the oscillation rather than correct it (gimballing has yet to have support for above CoM).

2) Your docking arms are flexible and have heavy landers, which is resulting in a very wide distribution of mass. The sligtest offset from flexing multiplies quickly.

The solution I use here is a puller configuration. I stack my landers inline with each other (or close to center on docking hub if former is impossible) and have multiple engines mounted on girders to pull the payload. Note that you need to disable gimballing or else there is a chance of the craft destroying itself.

[Vat]

Thanks - hadn't considered a tow configuration, but that sounds like a good solution, and easy to implement without redoing the launch vehicle from scratch. I'll have a play and let you know how I get on, and put up some shots.