Mother ships and wobbly docks

[RizzoTheRat]

My initial design for a science lander had it stood on top of a launch vehicle attached via a docking collar, so it could return to low Minimus orbit and refuel from the boosters remaining tank. However it appears docking collars are a bit too wobbly for this and combined with the fact that the collars don't snap to position meant I ended up with an off center payload and an unflyable wobbly rocket. With several struts on it was rigid enough but pulled to one side and my plan to reattach the booster stage for the flight home made Jeb feel seasick.

Mk 2 has a docking collar on the top of the nosecone and one on the side of the main tank, with the lander attatched to the booster by a normal decoupler ring. This is nice and stable but means I can't fly home on the booster as planned.

Is there an obvious trick I'm missing here for producing a rigid vessel that can split in to separate sections but dock back in the original positions?

Edited October 2, 2014 by RizzoTheRat

[Signo]

As far as I know the only way is to undock the nodes and rotate them (slowly) to the correct (as much as possible) position. In my experience chase camera might be helpful. If u want to "go mod" instead, the alignment docking camera (that was in the Lazor pack if I recall it correctly) is the tool. If the craft stays wobbly u could try Sr. docks for sensitive nodes.

If u post a screenshot I am sure that u will get plenty of different points of view.

[cantab]

Why did it end up off-centre? A symmetric lander with a stack-attached docking port shouldn't. Pictures would help.

[Epthelyn]

Why did it end up off-centre? A symmetric lander with a stack-attached docking port shouldn't. Pictures would help.

By the looks of it, the OP didn't manage to get the docking ports exactly centered when building the rocket - "the fact that the collars don't snap to position meant I ended up with an off center payload and an unflyable wobbly rocket".

Pictures would be useful; I've never encountered a problem with docking ports not centering when building a rocket.

[Wanderfound]

Sounds like you need the symmetry trick while building. To centre a docking port, engage symmetry. Wiggle the port about until the multiple ports overlap into a single image, then disengage symmetry and place.

Docking ports frequently need strut reinforcement for launch, but they should be fine after that so long as you don't throw multi-G thrust at them.

[smunisto]

Sounds like you need the symmetry trick while building. To centre a docking port, engage symmetry. Wiggle the port about until the multiple ports overlap into a single image, then disengage symmetry and place.

Docking ports frequently need strut reinforcement for launch, but they should be fine after that so long as you don't throw multi-G thrust at them.

Never had to use this. Ports have nodes, if being stack attached, so use those.

[Wanderfound]

Never had to use this. Ports have nodes, if being stack attached, so use those.

If the option is available, sure. But it doesn't always work: radially attachable parts (e.g. Standard Clamp-o-trons) generally don't snap to nodes. Non-radially attachable things (like the shielded ports) will, though.

The other option is to build from the port down: the port doesn't auto-snap to the stack node on a tank, but the tank will auto-snap to the node on the port.

[magnemoe]

As other say use struts then launching, stress later is much lower 0.3g rather than 3.

Use the large 2.5 meter ports for larger stuff, drag long stuff don't push it. This has the bonus that the bottom docking port can be used for an booster engine and perhaps with an drop tank during launch.

Turn of reaction wheels in docked parts with problems, sas will create extra forces here then it try to use all the wheels.

[cantab]

If the option is available, sure. But it doesn't always work: radially attachable parts (e.g. Standard Clamp-o-trons) generally don't snap to nodes. Non-radially attachable things (like the shielded ports) will, though.

If this is the issue, the clampotrons usually will snap to the stack node if you fiddle with the VAB camera right, so that you're looking at the attachee part sideways on. Alternatively, Editor Extensions can help by letting you disable radial attachment.

[RizzoTheRat]

Ok that's weird, just retried it how I had it set up before and it seems to be snapping to the centre point quite happily and not wobbling as badly. No idea what happened before. I've only got the standard and shielded Clamp-o-trons so far which are a bit narrow for the purpose but 3 struts to the main tank seems to do the trick.