One anecdote is known: nuclear fusion will be in twenty years. Will always be in twenty years. This joke, now no longer funny, grew out of the optimism of scientists who, in the 1950s (and in every subsequent decade), believed that nuclear fusion was only 20 years away. Now this anecdote has been taken seriously by a startup - a native of MIT (Massachusetts Institute of Technology), a highly respected and famous institution: Commonwealth Fusion Technologies. The startup promises to launch a working nuclear fusion reactor in 15 years. Promises cheap, clean and unlimited energy that will solve all fossil fuel and climate change crises. So they say: "a potentially inexhaustible and carbon-free source of energy."
Only problem: we've heard this many times before. What's different this time?
Another famous cliché concerns the energy of fusion. The idea is simple: you put the sun in a bottle. All that remains is to build a bottle. The fusion energy powers the stars, but it requires incredibly hot and dense conditions for the plasma to work.
An enormous amount of energy can be released when two light nuclei fuse together: the deuterium-tritium fusion, which is carried out as part of the ITER experiment, emits 17.6 MeV per reaction, a million times more energy per molecule than you get from the explosion of TNT. But to release this energy, you need to overcome the powerful electrostatic repulsion between the nuclei, which are both positively charged. The strong interaction at short distances leads to a fusion that releases all this energy, but the nuclei must be brought very close - on femtometers. In stars, this happens by itself due to the colossal gravitational pressure on the material, but on Earth this is more difficult.
First you need to try to find materials that will survive after exposure to temperatures of hundreds of millions of degrees Celsius.
Plasma is made up of charged particles; matter and electrons are washed away. It can be held in place by a magnetic field that folds the plasma into a circle. Manipulations with the magnetic field also make it possible to compress this plasma. In the 1950s and 1960s, a whole generation of devices with exotic names appeared: Stellarator, Perhapsatron, Z-Pinch, designed for this. But the plasma they were trying to hold was unstable. Plasma itself generates electromagnetic fields, it can be described by a very complex theory of magnetohydrodynamics. Slight deviations or defects on the plasma surface quickly got out of control. In short, the devices didn't work as intended.
The Soviet Union developed a tokamak device that offered vastly improved performance. At the same time, a laser was invented, allowing for a new type of synthesis - synthesis with inertial confinement.
In this case, it is no longer necessary to hold the plasma burning in magnetic fields; it is necessary to compress it by an explosion using lasers in a short time. But experiments with inertial confinement also suffered from instabilities. They have been running since the 1970s and may one day get their way, but the biggest to date - the National Ignition Laboratory in Livermore, California - has never reached a break-even point where more energy will be produced than expended.
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Much of the hope is with ITER, the world's largest magnetic confinement fusion tokamak, which is still under construction.
The project developers hope to ignite the plasma within 20 minutes to generate 500 MW of power with a nominal input of 50 MW. Full fusion experiments are planned for 2035, but problems with international cooperation between the US, the USSR (then still), Japan and Europe led to long delays and budget stretching. The project is 12 years late and costs $ 13 billion. This is not uncommon for projects that require huge installations to be built.
According to the ITER plan, the first thermonuclear fusion reactor, which will operate as a power plant, igniting and supporting fusion, DEMO, should come into operation in 2040 or even 2050. In other words, nuclear fusion … will be in twenty years. There is a tendency to solve problems with instabilities by building more and more facilities. ITER will be larger than JET, and DEMO will be larger than ITER.
Over the years, many teams have challenged international collaboration with smaller designs. The question is not speed, but practicality. If it really takes billions of dollars and tens of years to build a fusion reactor, will it be worth it at all? Who will pay for the construction? Perhaps by the time a working tokamak is built, the combination of solar panels and new batteries will provide us with energy that will be cheaper than that made on the tokamak. Some projects - even the notorious "cold fusion" - turned out to be false or not working.
Others deserve more attention. Startups with new fusion reactor designs - or, in some cases, revised versions of older attempts.
Tri Alpha expects to collide clouds of plasma in a structure reminiscent of the Large Hadron Collider, and then hold the synthesizing plasma in a magnetic field long enough to break even and generate power. They managed to achieve the required temperatures and plasma confinement in a few milliseconds, and also raised more than $ 500 million in venture capital.
The Lockheed Martin Skunk Works, known for their secret projects, made a splash in 2013 by announcing that they were working on a compact, 100 MW fusion reactor the size of a jet engine. At that time, they stated that the prototype would be ready in five years. Of course, they did not disclose design details. In 2016, it was confirmed that the project is receiving funding, but many have already lost faith and gained skepticism.
And against the background of all this disgrace, MIT scientists burst into the ring. Bob Mumgaard, CEO of Commonwealth Fusion Energy, said: “We are committed to getting a workstation in time to combat climate change. We think the science, speed and scaling of the project will take fifteen years."
MIT's new project adheres to the tokamak design, as it has done in the past. The SPARC device is supposed to produce 100 MW of energy in 10 second confinement pulses. It has already been possible to obtain energy from pulses before, but the break-even point is what really attracts scientists.
A special sauce in this case is the new high-temperature superconducting magnets made of yttrium-barium-copper oxide. Considering that HTSM can create more powerful magnetic fields at the same temperature as conventional magnets, it can be possible to compress plasma with a lower input power, a lower magnetic device, and achieve synthesis conditions in a device that is 65 times smaller than ITER. That's the plan, anyway. They hope to create superconducting magnets in the next three years.
Scientists are optimistic: “Our strategy is to use conservative physics based on decades of work at MIT and elsewhere,” said Martin Greenwald, associate director of the Center for Plasma Science and Fusion at MIT. "If the SPARC achieves the expected performance, my instinct dictates that it can be scaled up to a real power plant."
There are many other projects and startups that similarly promise to bypass all kinds of tokamaks and international collaboration budgets. It is difficult to say whether any of them will find the secret ingredient for the synthesis, or whether ITER, with its weight in the scientific community and the support of countries, will win. It is still difficult to say when and if fusion will become the best source of energy. Synthesis is difficult. This is how history shows.
Ilya Khel