Why isn’t nuclear fusion possible yet?
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It is. We’ve just been struggling to find a way to extract more energy from the reaction than we expend in starting/sustaining it.
That’s my understanding anyway. Anyone feel free to correct me if I’m mistaken.
It is possible. We do it all the time. The problem with nuclear fusion isn’t doing it, its doing it in a way that can generate power. Fusion generators require a lot of things to prevent them from just being a bomb. The reaction needs to be continuous and contained. Both of these things require a lot of energy which ends up using more energy than it generates.
We have figured out how to do nuclear fusion now for quite a number of decades. It just requires a lot of heat and pressure. The tricky bit is to make sure the facilities nearby survive the event. This is what we are working on now. The temperatures and pressures required to even start the fusion is so high that no known material know to man can withstand it. And the amount of energy that is produced in the fusion is too high for anything we know how to safely transport away. It is an extremely hard problem to solve.
Long story short, it is possible and has been done but it doesn’t return enough energy to break even; let alone produce energy. There’s a running joke that fusion will always be about 30 years away.
However there’s been recent developments (or a resurgence) in thorium salt reactors (fission) that have a SIGNIFICANTLY reduced risk of a melt down (no water cooling so no steam explosions)
The short answer is that it is; it’s just not yet possible to do on a large scale without putting more energy in than we get out.
The main problem is that, for nuclear fusion to happen, you have to make two atomic nuclei collide. They both have a positive charge, so they repel each other, like trying to make two magnetic north poles touch. This means the nuclei have to be moving very fast, which means the fusion material has to be at an extremely high temperature. That takes a lot of energy.
We now have the problem of confining the hot plasma. You can just put it in a big vat – even if the walls are made of something that won’t melt at that temperature, the plasma would cool down from touching them. So you have to use magnetic fields to confine it. That takes a lot of energy too.
The final problem is that atomic nuclei are tiny (100,000 times smaller than atoms), so unless the pressure is high, the chances of them actually colliding are small.
In the stars, these problems are solved by the weight of the star compressing its core, making its pressure and temperature increase until fusion can happen. But we simply can’t use that process on earth, because it requires too large a scale (and leaves the problem of how to contain the mini-star).
It is very possible.
Just look up at the sky and you will see nuclear fusion going on right there. It is how the Sun and Stars work.
We can also do it briefly here on earth in thermonuclear weapons.
We can also do it for slightly longer labs, but right now we are not yet at a point where we can keep it going and actually get more energy out of it than they put in.
The problem (one of the many, many problems) is that fusion usually happens at a the sort of temperatures that you get inside stars and that you need to use a lot of energy to heat things up to that level and keep that hot stuff contained.
Fusion at temperatures closer to what you have here on earth. So called “Cold Fusion” would be really cool to have but nobody quite knows if it is possible at all and how to do it if it is.
Fusion as a reaction is very much possible, it’s how must of the energy is produced in a Hydrogen bomb.
Fusion in a reactor has 3 problems:
1. Containment. It has to be contained in a magnetic bottle, which is difficult to make stable. Most reactors lose this stability after a few seconds or minutes. A useful reactor would require stability for days or hours.
2. Fuel cycle. There is a verity of fuels you could use, but for complicated reasons, the best is Deuterium Tritium. The Deuterium is easy enough to get out of water. Tritium needs to be bread from lithium using the neutrons from the DT reaction. This stage is extremely complicated. Also Tritium is really nasty shit. Nobody has ever added breaded blankets to a reactor.
3. Extracting energy. You may see headlines about fusion reaching “break even”, getting out as much energy as they put in. But this refers to a plasma physics value known as Q, and this break even refers to a Q of >1. You can’t build a useful reactor with a Q of 1.5, or 2, or 10. You’d need about 20. Because all the inefficiencies in both generating and extracting the energy are not included in Q. Nobody has generated a single watt of electrical energy from a fusion reactor. Nobody has ever added the generators.
technically its possible already, the issue is that is not feasable ot do at a useful scale.
atm we understand the theory and the conditions necessary ot reproduce it but we lack the tech and materials ot have a safe sustained reaction that didnt cost us more energy than it cna potentially generate.
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