[tsimionescu]

There is a plausible route from a successful ITER to a practical reactor, the DEMO project. In principle, if ITER achieves its goals with its current technology, simply replacing the magnets with more modern ones would probably be enough to produce enough energy for a fusion plant.

The designs for actually capturing that energy, and for replenishing tritium, are a bigger hurdle, but there are plausible technical solutions.

Helion in contrast seems entirely a scam, promising and failing to deliver results year after year. Zap energy seems to at least not make false timeline promises, but it is trying out a much less proven concept in a direct commercial venture - not a promising way to do novel research.

Note that I am very skeptical that fusion power is a plausible economic approach to power generation, and do personally believe that all known approaches will fail to deliver a power plant that is economically viable. The amount of power that is plausible with all current approaches seems far too low to justify the immense engineering costs, and the benefit of abundant fuel is just not that impressive when you have solar and wind as alternatives.

[pfdietz]

DEMO has no chance of leading to anything practical; the power densities of the concepts are far too low and their sizes/costs far too large.

You yourself admit the economic problem, which is not separate from the notion of practicality.

[tsimionescu]

My contention is, DEMO might plausibly supply power to the grid 20 years from now, but will struggle to justify its economic cost (though would likely be kept around for some time with public spending).

Helion and Zap energy will more likely never be able to supply power to the grid at all for physics reasons, regardless of economics (assuming of course they don't entirely change course and move to a tokamak-like design).

[pfdietz]

Economics is an inherent part of practicality. Being able to provide power to the grid, but not economically, is not any better than not being able to provide power to the grid at all.

Helion and Zap have larger physics barriers, that's true. But the goal isn't to produce a pyrrhic victory and a power plant that "works" but can't compete. The goal is competitive energy out. I contend Helion and Zap are both more likely to reach that actual practical goal than DEMO.

[tsimionescu]

Agreed in principle. We clearly have different priors, but I think we agree on the general idea.

Basically, ITER/DEMO has a low chance of being economical even if it works physically. Helion and Zap have a higher chance of being economical if their approach works. I think we both agree on these points.

Where we differ is that I don't believe it's plausible that Helion or Zap's approach will work at all. But this is just a belief ultimately, I'm not basing it on any objective facts or anything like that.

[pfdietz]

On what do you base your feeling about Helion and Zap? Having examined the concepts in some detail, I have come to the opposite conclusion. Helion in particular has a combination of very clever ideas.

[devaiops9001]

Where I think Helion approach is missing something big is Helion attempts to "force" the plasma with magnets, contrast to Safire where the plasma forms self-containing magnetic fields. Plasma, like fire, which is a "cold plasma" in a way, is something found in nature. Leveraging plasma that has self-containing magnetic fields is "going with nature" rather than trying to run against it.

Suppose one were trying to take advantage of heat provided by fire, they would want to exploit how fire naturally behaves to get the benefit, rather than attempt to force fire to behave a certain way to get the benefit.