For the past 70 years, scientists have been working towards unlocking viable nuclear fusion technology. But what is the holdup? Clearly the science “works” because stars exist. Why can’t modern technology generate a stable, commercially viable fusion reaction? From my perspective, there are likely only three scenarios impeding a nuclear fusion industry.
Is it a matter of materials engineering technology, where we simply cannot fashion the machinery/ equipment capable of handing the intense temperatures associated with fusion?
Do we not have the right mixture of fuels, precursors, and “catalysts” to trigger a stable reaction?
Or does the tech actually work fine and flawlessly, but it is just extremely cost prohibitive to set up a fusion reactor when a coal/oil/gas power plant already exists and investing capital refuses to fund fusion projects?
In: Engineering
It’s extremely expensive to build and run fusion reactors. Using lasers to confine matter until its dense enough to fuse or using magnets to do the same is really hard and the machines to do so are very expensive. The fuel is also pretty expensive.
It’s really just a cost issue. Mimicking the conditions in a stellar core in a controlled and consistent manner on Earth just isn’t very easy.
Just look at the expense, size, and complexity of the NIF.
Fusion happens when two small atoms (like hydrogen) are pushed _so close_ together that nuclear attractive forces take over and they fuse into a larger element, releasing some energy in the process.
For a fusion reaction to naturally become self-sustaining, it needs to be _massive_. The size of a star. At that size, the gravity of the star is enough to pull the hydrogen atoms close enough together to get fusion to occur.
Naturally, we can’t build something the size of a star on Earth. So for us to get the atoms close enough together to undergo fusion, we have to use incredibly strong magnetic fields or powerful lasers. That takes a ton of energy – so much so that what we get _out_ of the reaction is less than the energy it takes to make it happen.
Every year we get a little bit closer – we figure out how to generate the fields using less energy and we figure out how to extract more energy from the reaction. We just haven’t gotten to the point yet where the net production is positive.
It needs to produce more energy than it consumes- safely, reliably, and consistently.
Then, that excess energy harvested needs to be worth the financial cost.
The sun is terrible at fusion.
The avrage power per cubic meter in the core of the sun is 276W/m^3. A human have a volume of around 1/10 m^3 and we use on average around 100W to stay alive. So you produce heat at a power rate of around 1000W/m^3 ot 10x the sun by volume. A pile of manour that decompose generate around the same power as the sun.
This is by volume, if you look at is by mass the dencty of the core is around 150x the density if water, humans are close to water density. So by mass you generate around 15 000 time more heat the the core of the sun. The temperature in the core is around 15 000 kelvin
The fusion only happen in the core not the top layers.
To do this the sun need the gravity of all it mass, that is around 330 000 earth masses. So fusion is easy of you have the amount of mass of the sun but the power density is very low.
For a fusion reactor to produce power we need many time the power density of the sun. To get a higher rate of fusion we do not use Hydrogen-1 like most of solar fusion but Hydrogen-2 (deuterium) and Hydrogen-3 (tritium) The temperature need to be a lot higher, designs aim to have temperature of 100 million kelvin.
Add to this the reaction has to happen on earth in a vacume cointaing, the material can just touch the walls. So you need magnetic contaimnet to keep it in the middle. This require a lot of electrical power.The sun manage this by there is barley anything around that can be heated and decrease the solar temperature.
The result in no reactor have manage for long time operation to generate more thermal energy then it needed to keep int running. More energy have been produce for short time but it is not enough in additional energy or in time to make it a viable power source.
So controlled fusion in a reactor that generate more energy the is needed to run it is hard. If controlled is not a requirement then we know how to do it. A thermonuclaal bomb (hydrogen bomb) is just that. The sun is more like bombs then reactore, it is the enormous mass and produced gravity of the sun that keep the material in place. We can do that.
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