The sun is running on nuclear fusion. Have you really never come across this fact? Or have you, but choose to deny it?
Oh a fact is it? So why has fusion not worked then?
There is something very wrong with the argument: "Fusion power has not yet worked on earth on an industrial scale, so the sun cannot be operating on fusion." I believe you realize that yourself. But anyway:
Creating sustained, stable plasma conditions which enable nuclear fusion is technically very difficult. Temperatures need to be
very high, so you can't simply confine the plasma with mechanical walls. The magnetic field geometries needed to confine the plasma are very complex, and the required field strengths are very high. Maintaining the high currents required to generate the magnetic fields is challenging, especially right next to the very hot plasma, where the temperatures are inconvenient for using superconductors.
It helps if you have an entire star to work with, at a scale where gravity can hold things together. Having enough space around you so that you can tolerate the occasional solar flare helps too...
Anyway, thank you again for your reply #689 above. It has clarified for me that you are really talking about a perpetuum mobile concept. If you can't even see the flaw with that core assumption, I'm afraid we don't need to take this discussion any further.