I want to make a Radial Decoupler the Root Part of a Subassembly

[Phanixis]

I am trying to launch a subassembly from a spaceplane bay and I want to make a radial decoupler on the side of the subassembly the root part, so I can just load the subassembly and snap it to the bottom of the space plane bay. But I can never select the radial decoupler as the second root part, only the first root part, and the second root part is the only one that seems to connect the subassembly to the rest of the ship (I have no idea why there are two root parts, only the second selection seems to do anything). Any help in this regard would be greatly appreciated.

Thanks.

[Snark]

I think you're basically out of luck-- KSP specifically disallows radial-attach parts as the root of anything. (That's why, when you go to the VAB or SPH to make a new craft, all the radial pieces are grayed out before you place anything, and if you mouse over them it gives a little warning message about how it can't be the first piece.)

[SchweinAero]

You could try doing this:

1) While editing the subassembly, attach something like a girder to the radial decoupler.

2) Select the girder as the root.

3) Save the subassembly.

4) Load your spaceplane.

5) Attach your subassembly to the plane, onto any unused stack node, by the girder root.

6) Grab the rest of the subassembly by the decoupler and attach radially where needed.

7) Delete the girder.

Edit: Subassemblies must leave the root behind. But this will work fine with the Merge function.

Edited July 10, 2015 by SchweinAero

[Sharpy]

Actually, a subassembly should NOT contain a root part.

Attach any (dummy) part to the decoupler and set it as root. Then detach the whole vessel with the grider from the dummy part and drag it into the subassembly drop area to save it.

[Kryxal]

I pulled a booster with separatron and radial decoupler from a rocket and just dropped it in the subassembly area ... it's easy enough.

[Red Iron Crown]

You could try doing this:

1) While editing the subassembly, attach something like a girder to the radial decoupler.

2) Select the girder as the root.

3) Save the subassembly.

4) Load your spaceplane.

5) Attach your subassembly to the plane, onto any unused stack node, by the girder root.

6) Grab the rest of the subassembly by the decoupler and attach radially where needed.

7) Delete the girder.

This technique works very well in my experience.

Actually, a subassembly should NOT contain a root part.

All subassemblies have their own root parts, and that's the only part by which it can be attached.

[Sharpy]

OTOH you can't save the segment of vessel that contains its root part as subassembly. You must detach a segment from the root part - and the attachment point (the part you detach it by) becomes the root of the subassembly.

So, if you build a subassembly from scratch, with nothing else in the VAB, you need to add dummy part to the attachment point and set it as root, before saving the rest.