Why is this not attachable for the purpose of a sub-assembly?

[guitarxe]

Made a little KEO Satellite, and want to save it as a sub-assembly so that I can then build a launcher and attach 3 or 4 of these to the launcher.

But when I try to drag it to the sub-assembly, it tells me that it is not attachable, even though it clearly has a free attach point at the top of the octagonal strut:

Edited September 22, 2014 by guitarxe
changing to answered

[juanml82]

The root part of your vessel has to have an attachable node to work as a subassembly.

This mod lets you change the root of the ship while building

http://forum.kerbalspaceprogram.com/threads/43208-0-24-Jul18-SelectRoot-Set-a-new-root-part-0-24-new-UI

If you change it to the octo strut, it should work. I've found that changing the root part a lot in the same design can lead to corruption in the .craft file.

Other idea when designing something to become a subassembly is to start it with a part that won't be part of the subassembly. In this case, instead of starting with the probe core, you start it with a docking port and you build below that. Then you move everything except the docking port as a subassembly and it will work.

[Thiagobs]

The root part of the assembly have to have free attachment points.. That is, the part that you click and drag.

I assume the boxy thing under the decoupler is your control pod, right (BoxSat mod maybe?). That part does not have any free attachment points.

Edit: Ninja'd

[Wooks]

It's the probe core, subassemblies can't contain pods as far as I know, (you are using a Probodyne QBE, right?). As proof try to save part of the ship as a subassembliy, select the lower part from the first battery, you will see it takes it.

Edited September 22, 2014 by Wooks

[Stargate525]

It's the probe core, subassemblies can't contain pods as far as I know. (You are using a Probodyne QBE, right)

No it's not. Subassemblies have no problem having probe cores or command pods.

[Wooks]

No it's not. Subassemblies have no problem having probe cores or command pods.

Try it, I just did, with the probe attached it gives the error, saving the subassembly without it doesn't. It's because part 0 can't be a probe.

As proof try to save part of the ship as a subassembly, select the lower part from the first battery, you will see it takes it.

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Edited September 22, 2014 by Wooks

[EdFred]

I have made plenty of sub assemblies with a second pod or probe. If I know I'm building a SA, I start with a probe core (or other available root part), build everything off that and then drag and save from part 1 - assuming root part is part 0.

[AlexinTokyo]

As a workaround, if you don't want to rebuild the whole thing, save the satellite minus the octo strut as a subassembly, then start a new craft, place an octo strut as the root part, attach the saved subassembly and then grab the (now root) octo strut and drag it over the old subassembly to overwrite it.

If you can't place an octo strut as root (I can't remember) then place any root part, attach an octo strut and then go from there.

[Wooks]

I have made plenty of sub assemblies with a second pod or probe. If I know I'm building a SA, I start with a probe core (or other available root part), build everything off that and then drag and save from part 1 - assuming root part is part 0.

That's correct, part 0 can't be a probe.

... If you can't place an octo strut as root (I can't remember) then place any root part, attach an octo strut and then go from there.

Excellent suggestion.

[EdFred]

Part 0 can be a probe, but part 0 can't be included with the SA. I just finished doing exactly that. Probe core(part0) -> Clamp Sr(1) --> 2ManCan(2) --> lots of other stuff. Grabbed the Clamp Sr and saved.

[Taki117]

That's correct, part 0 can't be a probe.

This is not true at all. Any part can be the root part of a subassembly. The only requirement that needs to be met is that the root part of the subassembly must have a free attach node. It is easiest to do this with a dummy root part (i.e if you are planning to place something with a decoupler you want your root part to be before the decoupler) but it is by no means a requirement.

EDIT: in the case of the OP, if you pull the strut and decoupler off the top of the probe (to free up that node) it will work.

Edited September 22, 2014 by Taki117

[Rhomphaia]

That's correct, part 0 can't be a probe.

Part 0 can be a probe, but part 0 can't be included with the SA.

Part 0 can be a probe, and part zero can be included with the SA, as long as part zero has a free attachment node.

In the example above delete the decoupler and octagonal strut from above the probe core and you can save the rest as a subassembly.

[guitarxe]

Ah, I see. Didn't know the root part had to have free attachable points. Thanks

[Eric S]

I realize that this has been said, but here's actual evidence supporting the claim that you can start with a probe core and make a subassembly starting with the probe core.

I built a 20 part probe stand alone in the VAB, starting with a probe core as the initial part, leaving the top node of the probe core open. I then dragged the entire craft off into the subassembly drop zone, which created a subassembly. I then created the bus craft that would deliver eight of the probes. I placed two symmetric bands of four docking ports around the craft, and then picked up the probe subassembly. I rotated the probe so that it would connect its top node to the docking port whereupon it connected and replicated to the other three ports. Feel free to replicate if you don't want to take my word for it.

So probe core or not probe core is irrelevant. It all comes down to having an open node on the root part (whether that root part was the first one placed or attached to something else).

[Wooks]

The more you know , mistery solved.

[AlexinTokyo]

I think (I'll need to test to be sure) that the problem lies with defining the root part of the subassembly.

If the subassembly you are trying to create contains the root part of of the ship under construction, the game attempts to maintain that part as the root part of the subassembly. If there are no open attachment nodes then this will, clearly, fail.

If the subassembly does not contain the root part of the ship under construction, the game will designate the selected part as the new root part of the subassembly. Since this must have been connected somewhere and disconnected in order to drag it over to the subassembly builder, this cannot fail, as there will always be an open attachment node.

So if you want to make a probe lander with a top-mounted docking port as a subassembly, you need to start with the docking port and build down.

[Sirrobert]

Try it, I just did, with the probe attached it gives the error, saving the subassembly without it doesn't. It's because part 0 can't be a probe.

As proof try to save part of the ship as a subassembly, select the lower part from the first battery, you will see it takes it.

http://imgur.com/a/ZHkJm

The difference is because part 0 now has an attatchment node. It has nothing to do with the fact if it's a probe or not.

To properly test this: Rebuild the ENTIRE craft, exactly the same, but now use one of the batterys as root. You still won't be able to save as sub assambly. The ONLY thing that matters is if the root part has an open attatchment node

[Montag]

Move your initial probe core to be on the other side of the Octostrut. Add a new probe core where the old one was. You should then be able to take the Octostrut on as a subassembly.