Good question, but is this a good answer?

 

Even though it is New Year's Eve, this post will be about something else. It is going to be about nuclear fusion again...

There is no problem in achieving nuclear fusion. The problem is getting more energy out of the reaction than what is put into it. So, why is it so hard? That is what you call a "good question". A good question is one in which an answer is not so easy.

Allow me to speculate a bit. It takes a lot of energy to get to fusion in the first place. In order to produce a plasma, the electrons have to be driven off. This takes a lot of energy. In order to produce this much energy, it will take a lot of energy. That energy has a lot of losses associated with it in order to produce it. Imagine a really big internal combustion engine that requires a really big starter to get it moving. The principle is the same, but the magnitude necessary for a fusion device is much more difficult to achieve.

I like Bussard's Polywell concept because it doesn't confine positively charged hydrogen nuclei ( or protons), but uses electrons instead. Think about it. It takes a minute amount of matter, which electrons possess, to produce the electric equivalent of millions of degrees of thermal energy. Electrons are the negatively charged component of the electrically neutral atom. An electron masses at 1/2000th the mass of a corresponding proton or neutron. That is quite a difference in mass. Consequently, to contain it would require a lot less mass as well. Bussard's device is much more compact than the ITER approach, which takes a office building sized structure. A polywell device could be as small as a ordinary room.

In order to fuse two positively charged nuclei, it requires a force that is greater than the electrostatic repulsion to each nuclei. This explains the need for so much thermal input. The nuclei must be hot as the interior of the sun, and it has to be confined so that the atoms cannot repel each other, and thereby forcibly fused together. The fusion releases tremendous amount of energy that we'd all like to harness to run our contraptions. Not only hot, the plasma must be confined by some force. With the sun's mass, the enormous gravity well provides it. In lieu of this gravity well, another force must be utilized, since gravity is out, and that may well take a lot more energy.

Consequently, in order to achieve fusion, a way must be found that is much more energy efficient as well. The Focus Fusion device uses a characteristic of plasmas in order to achieve confinement. There is a phenomena called the "pinch", which is being employed. The "pinch" will enable the fusion. Focus Fusion is using a natural force, not unlike what gravity provides, in order to arrive at the desired conditions that will enable fusion. This is an economy as well, as the Focus Fusion device is also much smaller than a Tokomak device that ITER is employing in its fusion experiments.

But what about the success mentioned recently? These employ lasers. Light can exert pressure as well. Concentrated light, which is what laser are, will provide even more pressure. Therefore, a laser light in the form of a powerful laser device, will provide the necessary confinement so that fusion can occur. Light pressure doesn't produce much pressure. Concentrated light COULD. Evidently it does, since the experiment worked well enough to produce more energy than what it took to make the laser beam. The trouble seems to be what it takes to make a laser that powerful. Much more powerful lasers must be developed.

The Helion device is another possibility. It seems to use a combination of plasma and kinetic energy. The plasma is accelerated and smashed together. The device doesn't appear to be all that large. Perhaps it can work.

Since the devices use so much energy to produce the conditions, I'd speculate that this is a major reason why it is hard to produce net energy from a device. The devices must be smaller and more compact. Such a smaller device would minimize energy losses, or so I think. Just to maintain a large plasma in an office size building would require a lot more energy than in a device that is the size of a room. This would entail energy losses that have to be made up by the fusion reactions.

Besides the energy losses in producing the conditions for fusion, their are losses that occur from the conversion of fusion energy into electricity. These losses are the normal losses in producing energy, but there are others. There are Xrays that are produced from the nuclear reaction, for example. These losses have to be minimized as well. If all the losses can be minimized, a net energy device could then be feasible. There are those who say that they are close to acheiving that vision.

Are we really that close? That's another good question. If I were a betting man, the best bet would not be the laser device. But in the end, that may be the only one that could work. But it appears to be quite difficult to produce a laser that is powerful enough to do the job. In the end, the laser device may never produce a commercially viable process. As they say, time will tell.