Fusion may be difficult but math and physics say we should be able to do it. Just because it's difficult and with a long time horizon doesn't mean you should throw it in the bin with "perpetual motion". (Cold Fusion however, you may throw in the bin)
Just saw a talk [0] where they talk about using lasers to create fusion. The current puck used to kick start the process costs $1M, (paraphrased) "it needs to cost 20 cents before Fusion is viable. But hey, we're in the research phase!"
From the point of view of an end user, it doesn't matter if a technology is not possible because it's physically impossible, or if it's so uncompetitive it's economically impossible. The net effect is the same: the technology is dead to them.
Wouldn’t go so far as never. I’m going to go out on a limb and say Fusion power on a space ship will be viable one day if humanity survives long enough.
Fusion is already working. Not well enough to be commercially viable, but it's already working. ITER will produce more energy than it will be using - albeit only enough usable energy to break even. It's not a matter of making it work anymore, it's only a matter of getting it to work well enough.
But maybe all we will ever need are solar panels, after all the sun is providing way enough energy as is... for now.
Let me be more precise (for you and for the people who downvoted me): fusion will never be cost effective. Ever. There is no conceivable material for the walls of a reactor that could withstand the neutron bombardment from the reaction. Maybe there’s some super-inexpensive way to replace the entire reactor core every 18 months... but I seriously doubt it.
We have an excellent material for fusion reactor walls. It's the highly-radioactive waste from a fission reactor.
The neutron bombardment makes the waste less radioactive.
With recycling and purification steps, we can direct the equipment to generate more of the isotopes we value and less of the isotopes that are undesirable.
What you wrote there is 100% absurd. The waste from fission power plants lacks the material properties necessary to form the walls of a fusion plant, and would be nightmarishly difficult to fabricate into anything even if it did.
There has been repeated talk of putting transuranic waste into fusion reactor blankets for destruction or breeding (so called fission-fusion hybrids) but these inherit all the negatives of fission and fusion reactors (the worst of both worlds) without any big advantages to compensate. And this would just be materially passively loaded in blankets, not essential structural elements (that, for one thing, cannot spring any significant leaks without ruining the plasma by allowing coolant into the vacuum vessel.)
That's what Lawrence Lidsky was saying fusion people should work on, in his (in)famous 1983 article "The Trouble with Fusion".
Then his PhD student Todd Rider shot down the very low neutron fuel cycles. D-3He remains possible, but that still produces neutrons, albeit fewer than DT (and requires mining bodies in space to get 3He).
Just saw a talk [0] where they talk about using lasers to create fusion. The current puck used to kick start the process costs $1M, (paraphrased) "it needs to cost 20 cents before Fusion is viable. But hey, we're in the research phase!"
[0] https://www.youtube.com/watch?v=hcGgaa2mFc4