The mystery of the UFO is immediately revealed ...
It is the result of my test to use FreeCAD to develop a comptibile aircraft with FGFs. FreeCAD is convenient to use ... and exports Colada format that can be read with Blender and then export to .ac format.
Honestly it would be interesting to develop a direct export of FreeCAD to .ac (FreeCAD is written in Python), but my job now does not allow me to have time to develop it.
FreeCAD Unfortunately, like many other 3D CAD, it has difficulties to create double-curved surfaces. Is there a tool to do it, but its use is quite complex and only suitable for ship hulls. Maybe in the future someone will write other more suitable instruments.
FreeCAD for your information lends itself very well to design tools, engines, propellers, and many other details, including buildings. It lacks only the ability to export to .ac format without losing the generated object name.
The shape of UFOs have derived from books by Renato Vesco, as shown in that show covers below:
Renato Vesco was a ufologist Italian who lives in Genoa, graduated in an aviation school during World War II, he is immediately interested in ufology, and picked up a huge amount of material. In the 50 'of last century it suggested that UFOs were not of terrestrial origin, but made in England and Canada starting from German construction plans.
Currently the Vesco theory was not supported by the facts (Still, we wonder if the phenomenon of the UFO is real or not ...), but remained his drawings and perhaps even his dreams to build a machine that can function as a UFO as optimized for the flight from the 30 km altitude up.
In fact the UFO designed by Renato Vesco was a big vacuum cleaner, I think that could never fly, although he ordered the construction, I think in Sweden, a couple of models that do not know if they've ever flying.
I really like the shape and direction of an object derived from the technology available in the years 40-50. I think it would be nice to put a period instrument panel and try to simulate what could be the flight model of this strange and original aircraft.
Here there is a translation of an article by Renato Vesco in English:
http://www.sacred-texts.com/ufo/vesco.htm