Remembering that there's no possible way we could know how many years away a thing is; the numbers are clearly a guesstimate.
They're more of a rounded (hence the clustering at or away from given numbers) measure of the remaining 'effort' versus 'difficulty'. Very likely there is some absolute time required (experiments take time to run), but throwing more people (and more importantly, more resources to run experiments and gather data) at the problem /would/ get to an end result faster (though how much faster is open to debate; it's sort of like asking how much effort does it take to win a top 30th percentile prize from a lottery).
What's different this time (yeah, I know, I know) is that, if what they and EMC2 are separately claiming is true, it's gone from being a fundamental physics problem to relatively tractable engineering, with well-understood risks and timelines.
Compare this with ITER, where they still don't know what material some fairly critical components can even be theoretically made of. It's just night and day.
>Compare this with ITER, where they still don't know what material some fairly critical components can even be theoretically made of. It's just night and day.
the Skunk Works and EMC2 haven't even reached the stage where they would face the same issue of material - all of them would ultimately have to contain the same type of fast neutrons and there is no good known material to do it.
That's true as far as it goes, but it's not the problem I was actually thinking of.
The problem is related to how you get rid of the post-fusion products. ITER is designed with divertor plates in the floor to scoop off the fusion ash and shunt them outside the core. My understanding is that these plates have to be a) solid, and b) capable of withstanding contact with absurdly high temperature plasma. There are some candidate materials which are hypothesised to be able to stand up to temperatures somewhere near what's required, but to my knowledge (which admittedly might be out of date) nothing's actually known to be suitable.
The reason I don't think the neutron absorption issue is such a problem here or on Polywell is because with a smaller reactor, replacing the vessel when it stops working is a far less terrifying prospect, even if you have to do so every few months. And even this is far less insane than some of the proposals for how you might do commercial laser fusion. That's just bananas.
Beyond that, you actually want some fast neutrons from the reaction to give you a tritium source.
What part of the reactor degrades so quickly? Can't it be replaced continuously? Why isn't the shielding done with some non-degradable matter, like water or some oil?
As an example of the problem, anything made of metal will become brittle. For why this might be a problem, take a look at what's in the middle of the ITER toroid: you've got a stack of magnetic coils, which have to be physically braced against a colossal magnetic repulsion by a great big pre-stressed metal core.
I'm sure someone at ITER has done the maths and figured out how long that core can last under operation before it becomes too brittle to keep the coils together, but I wouldn't be at all surprised if that was one of the reasons why ITER isn't designed for long-term power generation.
If the shielding is made of matter, then the nuclei of the atoms in that matter will absorb neutrons and become radioactive. Clearly the solution is to make it out of the many materials which are not composed of matter.
There are still some serious basic physics issues to be worked out.
They dismiss the concerns of the scientific community. Why shouldn't they? They're getting rich off of the ignorance of generals and venture capitalists.
That's the standard issue joke. "Nuclear fusion has been just ten years away for the last fifty years"
It is so common as a joke I'm surprised the article didn't mention it.