Thermionic converter (current source).

30 years ago I dealt with this topic in the former Soviet Union. Making garlands elements thermionic converter has been a very difficult and very expensive technology. For the manufacture of metal-ceramic packages it needed large equipment. Plasma spraying, electron beam welding, gasostatic pressing ... a some of nostalgia, a little dream, a little delirious ... :-( Completely crazy idea: 3D printing ... The assembly of the 10 elements in series as the fuel elements in a nuclear reactor. There are some simplifications ... right design ask to NASA. Uranus is no need to print here (it will "print" the another company :-)