> why did early attempts at production of fusion power fail to work out
Largely due to unrealistic assumptions on the part of the researchers involved.
Are you familiar with the Lawson criterion? Probably. Are you familiar with WHY he wrote it? Probably not.
He wrote it because he was tired of seeing everyone in the field making utterly ridiculous estimates about performance. There are countless experiments where basic math suggested the system would not work, but they went ahead and built it anyway without bothering to check first. Google "astron". There was so much belief in the ultimate success that no one listened when someone said there were issues.
And that's in spite of one of those people being Teller himself. In 1953 he gave an impromptu talk about stability in magnetic confinement and how he felt that it was a *very* difficult problem and no one was really thinking about it seriously. So, of course, everyone went off and thought about it seriously, right? No, they went off and wrote hand-waving statements about why their particular machine didn't apply, which then failed in precisely the way he predicted.
Lawson was equally tired of this. He sat down to put real numbers to the problem. He started by considering the power input and outputs needed to have the reactor produce net energy, and then worked to find the conditions needed to make that happen. His paper, which you can read here:
(and it's very easy to read, so go ahead and do it) concludes "Even with the most optimistic possible assumptions it is evident that the conditions for the operation of a useful thermonuclear reactor are very severe". In case you don't recognize it, that's British humor: he's saying its almost impossible and everyone needs to stop and think seriously.
So, of course, no one did. They simply waved their hands some more and came up with reasons why they could reach these numbers, and the money kept coming. And coming, and coming. We're *sixty years later* now, Lawson has been dead almost a decade, and we're still trying. In that time we invented the IC, the internet, went to the moon, etc. At what point do you realize no one cares any more? Nuclear cars seemed like a good idea at one time too.
Enough already! The power companies have said they're not interested, how much money do we have to spend to change that?