It was a slow death  as the idea gradually formed, but all the models have to be redone in Blender.  Manely, Freecad is strictly designed for structures rather than visuals, so it can't export normals or do UV unwrapping.  There are objects which Freecad uses to draw the GUI & those objects contain normals, but those aren't accessible by the mesh exporters.  

RCS thrusters, air lock, & smoother grid fins are still needed.  Blender's working thickness tool should greatly improve the quality.  A better strategy is creating just an engine nozzle for testing.

 There is a script which tries to export a mesh with normals from a corresponding part https://raw.githubusercontent.com/andreasBihlmaier/FreeCAD/master/export_obj_with_normals.FCMacro
It requires hiding all but the 1 part & selecting it.  It's too slow & doesn't accept meshes as input.

Lions just aren't fascinated by the process of making a game.