Hi LOTRJ - first I'll take a look at combining the dome and engine.

The problem seems to be at this juncture:



If you zoom in there a ways you can see the edges kind of stray a little ways away from the axis line:



Something is going wonky there with the edges and intersecting surfaces all coming to a nexus there.

One other thing to add to the list of tricks is to give Trim a try if the booleans fail, and in this case it seems to work.

Try these steps:

1 - select both the dome top part and the engine platform.

2 - run Edit/Trim.

3 - The prompt in Trim will say "Select cutting objecdts or Done for mutual trim". In this case you want to do a mutual trim where each object is acting as both a cutter and also being cut itself. So right-click or push "Done" now.

4 - It will crunch for a few seconds and then a new prompt appears: "Select pieces to remove or push Done to keep all". But in this case it is easier to pick the pieces to keep rather than the pieces to remove. So go to the option for Mode: and switch it to Mode: Keep. Now click on the visible part of the dome and the visible part of the platform to select those fragments, and right-click or push "Done".

5 - Now the internal parts have been discarded, so you can now select the Dome piece (which is not a solid right now, it is an open set of surfaces that touch the other engine piece), and then the engine piece, and use Edit/Join to glue those pieces into a solid.


That should give you a good dome + engine result, basically those steps are using Trim + Join to do what Boolean Union is supposed to do automatically, but something in the booleans is getting confused with that one juncture point.

Please let me know if that gets you a good first part combined, I'll now take a look at combining in the saucer.

- Michael