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On the verge of a fusion breakthrough?

14 September 2018

Great news, sustainable over-unity nuclear fusion reactors could be just 10 years away.

(big fat grin)

Haven't we heard that before?

Actually, I've heard that every decade since the very first man-made over-unity fusion reaction was generated back in the 1960s and I'm still waiting.

Of course the other "just ten years away" piece of technology was the flying car -- but we almost have those now so surely we must also "almost have" fusion reactors.

Well a clever bunch of scientists in the USA and Korea have been jointly working on the difficult issue of confining plasma using magnetic fields and they believe they've uncovered another missing piece of the puzzle.

According to this report from Science Daily, scientists have been successfully able to calculate all the factors associated with magnetic containment -- and that's a first, apparently.

As a result of this breakthrough, the scientists should be able to come up with a combination of electromagnets and clever software that will finally deliver the holy grail of successful containment and thus open the door to practical fusion reactors.

Or maybe not... only the next 10 years will tell.

When it comes to the way that these reactors are being designed, I actually wonder whether perhaps the real problem is that we're trying to create the wrong solution to the problem -- hence our record of abject failure for over half a century.

Trying to contain a plasma with magnetic fields is somewhat akin to trying to hold water in your hands with your fingers open. There are just too many holes and the water is very effective at finding its way through the gaps. Another analogy that springs to mind is "nailing jelly to a tree".

The problem is that there is too much positive feedback in the loop. There's no negative feedback (or self-stabilising) element to magnetic containment. The smallest deviation from the datum quickly grows and the more it grows, the faster it grows. This makes the task of containment (to date) impossible.

What's needed is a method of containment which, in and of itself, represents an equilibrium -- a state where deviations create their own corrective force.

Think of this like a long piece of metal pipe. Stand that pipe vertically and place a pivot point at the base and it will balance perfectly -- until the smallest puff of air, vibration or other force causes it to deviate slightly at the top. At that moment, the centre of mass will be displaced from the pivot point and the pipe will topple.

To maintain a balance, the bottom pivot must be constantly shifted, to place it directly under the centre of mass, every time that centre of mass changes. This is exactly how we balance a broom on our finger -- easy-peasy once you get the hang of it -- and this is how scientists are hoping magnetic confinement will (eventually) work. A super-fast computer will manipulate magnetic fields to (almost) instantly correct for any changes in the plasma flow.

Ah... but if the problem were only that simple. To understand how difficult magnetic confinement *really* is, imagine you have 100 brooms, all balanced on top of each other in a long line. Now try and balance that arrangement on your finger. Not so easy eh?

Now imagine a "positively stable" equivalent to our broomstick or length of pipe.

We get this by placing the pivot point at the top, so that the pipe hangs down vertically.

Now, any force that disturbs the pipe will (once again) cause the centre of mass to deviate from the pivot - but this time, gravity will provide a corrective force and the pipe will swing back to the vertical from its displaced position.

Now imagine those 100 broomsticks, all fastened together so that they hang vertically from a pivot point. No matter how much you disturb those broomsticks, they will all (eventually) return to the stable position from which they started -- all by themselves -- no corrective input required.

Clearly, a much better solution to the issue of plasma confinement would be to devise a system which has positive stability... a system where the plasma just wants to remain confined.

What would that look like?

Well it would probably look a lot like the sun -- a sphere, where the force of gravity provided the containment and where the inverse-square nature of that force provided the stabilising factor to control the plasma's position.

The sun does not look like a tokamak and I'm surprised that we're not learning directly from nature (as we have done with so much of our other technology) when it comes to creating stable plasma for the purposes of nuclear fusion.

But you know what?

I'm going to repeat what I've said on several occasions already...

Why the hell are we even trying to reinvent the wheel?

Why are we attempting to build something as expensive, difficult and potentially impractical as a fusion reactor, right here on planet earth?

Why do all this when nature has provided a ready-built fusion reactor just 85 million miles away?

We don't have to build it, maintain it, fuel it or worry about it (for a few billion more years) and every day, it dumps (on average) than 500W of energy every hour on every square metre of the planet's surface.

Sometimes the simplest (most obvious) solutions are the best. Aren't they?

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