Magnetic-confinement fusion stalled, according to Dr. Whyte, because to get more power (and efficiency) we need stronger fields. To get stronger fields we needed bigger magnets. To support bigger magnets one needs bigger structures. Big magnets and big structures will absorb more magnetic and neutron flux; that increases maintenance frequency, complexity and cost.

Better superconductors let us get stronger fields without bigger magnets. That changes the cost function.

[1] https://youtu.be/KkpqA8yG9T4?t=18m3s

I guess iron based superconductors are a relatively new and hot area of research.

https://en.wikipedia.org/wiki/Iron-based_superconductor

"Fusion energy is 20 years away and always will be."

This shows how much damage a superficial catchy meme can do if it manages to slip in and override more nuanced and informed thinking. It's why I distrust catchy sloganish rules in other fields too, such as "premature optimization is the root of all evil" (leads to erooM's law in software) or "never roll your own cryptography" (discourages people from learning about how to create secure systems), etc.

Recently in this case means mid 1980s. Is the ITER design really that old that they could not make use of YBCO superconductors?

https://en.wikipedia.org/wiki/Superconducting_wire#Coated_su...

http://en.wikipedia.org/wiki/Bismuth_strontium_calcium_coppe...

More generally, the demountable coils suggests that designs could be made where the magnets are replaceable with some degree of economy.

How can it "produce more energy out than energy in"? I don't know if I am not aware of what you mean by that, but that doesn't seem possible?

Doing so in a way that produces sufficient energy to sustain the fusion reaction without creating an uncontrolled reaction ("boom") is the trick that always seems to be 30 years away.

Uh, no, not really, a run away fusion reaction has never really been a concern. In fact, that's one of the biggest advantages of a fusion reactor vs. a fission reactor. Fission is a self-sustaining reaction, once it starts you have to work to stop it (via injecting a mediator to interfere in the fission reaction), where as fusion requires constant energy input in order to maintain the reaction. The part that "always seems to be 30 years away", is achieving a fusion reaction that produces more energy than it takes to maintain (allowing some of the output energy to be siphoned off to maintain the reaction). There have been a number of techniques attempted to achieve this with the holy grail being so called "cold" fusion, where cold is defined in this context as something less than the surface temperature of the sun. It sounds like the ultimate solution to the problem though is simply better magnets, not cold fusion at all.

Assuming this pans out, the real thing needed to make this viable as something other than a novelty is how much more efficient the reaction can be made. After all, if the output energy is just barely over the input energy you'd need to scale out to ridiculous extremes to produce enough usable energy, but if it's a significant amount higher then that makes more modest size plants viable.

Seems a little low, though I suppose 1L is only 1/5th of a gram of helium. I still might be missing something, too.

This superconductor breakthrough also seems relevant to Stellarators such as Germany's new(ish) Wendelstein 7x: https://en.wikipedia.org/wiki/Wendelstein_7-X