Subassembly not working properly

[KateTheAwesome]

So I experimented around with designs, found a rocket that lifts pretty well and I now wanted to save the carrier part as a subassembly so I could just strap it to whatever payload I had.

However when I want to drag the lifter onto the Subassembly try it tells me that the part isn't attachable (It yells at me in all caps).

If I only try to save a single part of that lifter, say a fuel tank from the middle in the subassembly it works. What's the point of the sub assembly if parts need to have their bottom part free? I want to reuse lifters, not payloads -.-

This is what the whole thing looks like:

Thanks for any help in advance.

Cheers

[Johnno]

I haven't tried it much, but seems to work fine for me if I start with the initial part at the top and then build downward. So if you choose a decoupler as your first part and build the launcher below it as normal, then shift left-click your ship and drop it on the subassembly box. That way works for me anyway.

[KateTheAwesome]

Okay but that's just dumb...seriously, why would you design a system like that >_> I guess it'll save the time of rebuilding carrier stages but they specifically said in the "trailer" for 0.22 that saving landers would be part of the deal :/

[Smidge204]

AFAIK you can't "subassembly" the root node of the part tree, aka the very first part you started with. You need to rebuild your design so that you can detach it from something else (like a command pod), so then it'll know where it attaches.

That's my theory, anyway. Not in a position to try it myself at the moment.

=Smidge=

[700NitroXpress]

You can't use anything that starts out as a command module. So if it has an unmanned probe part or something like that on it, you have to grab what's under it. The core part can't be put into subassemblies.

[Kasuha]

There is a problem with the root part of the ship (the first part you placed in VAB, usually but not exclusively command module) - if you try to save as subassembly anything that contains it, you may have problems. I never had problems making a subassembly from anything I can pull off the ship and can leave "hanging in space" in its transparent form.

[numerobis]

You can't delete the root part either. I presume it's a user-annoying condition to save some (possibly a lot of) developer-annoying work. Workaround is to create your launcher under a pod you have no intention of using.

[Bengsch85]

Why doesn't the root part work? I use Select Root to change the part I want to attach with as the root part and save it as a subassembly then. And that includes command modules as root parts.

[Smidge204]

Okay, had a chance to experiment a bit.

This craft can be sub-assemblied in its entirety:

THIS craft cannot:

Can you spot the difference?

The root node - in this case a command module - has two attachment points. In the first screenshot, the top attachment point is available for connection and therefore valid as a subassembly. In the second screenshot, there are no open attachment points.

So the rule extrapolated from this: The part you click on and drag to the "Subassembly Drop Zone" area must have at least one unused attachment point to be valid. It does not matter if the collection of parts as a whole has any open connections - only the root part of the collection.

=Smidge=

[Kasuha]

Edit: ... nevermind ...

[SimXY]

http://forum.kerbalspaceprogram.com/threads/43208 helps a lot here.