“I think the world is going to want a tremendous amount of compute. And there are a couple things that are hard about that. Energy is the hardest part. Building data centers is also hard. How do you solve the energy puzzle? Fusion. That’s what I believe.”
-Sam Altman on the Lex Fridman podcast
Fusion has been this amorphous promise that’s always seemed like its been ten years out. But what is fusion? And why is now any different from fifty years ago?
What is fusion?
It’s the underlying process that powers the universe.
As its name implies, it’s about fusing two elements with lighter mass together to make an element with heavier mass, and in the process, energy and heat is released.
Most fusion in the universe happens in the center of stars, where intense gravitational pressure and heats fuses two hydrogen atoms together to create helium.
But How Does it Work?
The fusion process begins when two protons fuse together because of intense pressure and heat.
This leads to the creation of deuterium, an isotope of hydrogen.
Then, deuterium combines with another proton to form helium-3.
Finally, two of these helium-3 nuclei collide to produce helium-4 and release two extra protons in the process.
The energy released during these fusion reactions is what powers the Sun and sustains its brightness.
So to recap, four hydrogen nuclei are converted into one helium nucleus during this fusion process, with a significant amount of energy being released due to difference in mass between the reactant (hydrogen) and the product (helium).
Why do we care?
The energy that is released through the fusion process could be harnessed to create a safe, carbon free, and nearly limitless source of energy.
Limitless in that the hydrogen fuel is abundant in nature and a successful fusion reaction would be self sustaining without the need for an external heating source.
Carbon free in that the fusion reaction does not produce carbon, and the waste generated would be low level radioactive materials, which pose a much lower risk to the environment than fission waste.
Safe in that fusion is basically the opposite of nuclear fission, and there is no chance it could spin out of control.
Nuclear Fission relies on super heavy elements such as Uranium 235. When Uranium 235 is bombarded by neutrons, it creates the unstable Uranium 236, which splits, releases energy, and starts a chain reaction.
To be clear, fission is not all that dangerous in and of itself either, and we should be utilizing it more as part of our future energy mix. But fission does rely on a chain reaction to produce energy that, if left unchecked, could get out of control.
Fusion, in contrast, relies on fusing super light elements together, rather than splitting heavy elements apart. An unconstrained chain reaction is not possible, because if the necessary conditions for fusion to occur are disturbed (pressure and extreme heat), then the fusion reaction will stop.
This benefit is also why fusion is an incredibly hard problem to solve. In order to perpetuate a fusion reaction, there needs to be both:
Heat: extremely high temperatures exceeding 100 million degrees Celsius are required.
Confinement: The sun creates confinement through its intense gravitational field. But on Earth we have two options:
Magnetic confinement fusion (MCF)
Inertial confinement fusion (ICF)
Magnetic Confinement
Experimental research on plasma heating in donut shaped systems began in 1951 at the Kurchatov Institute in the Soviet Union. It progressed from early devices made of glass, porcelain, and metal to the operation of the first tokamak, T-1, in 1958.
Today, the tokamak design is considered to be the most reliable way to create a fusion reactor. The design has been extensively studied and refined over the years, making it one of the most promising approaches for achieving controlled thermonuclear fusion for energy production.
Projects like the International Thermonuclear Experimental Reactor (ITER), the world's largest tokamak, is under construction today in France.
And SPARC, from Commonwealth Fusion is under construction in Massachusetts. They both seek to provide the “Kitty Hawk” moment for fusion by creating a successful, self-sustaining fusion reaction.
This condition is known in fusion circles as Q > 1.
The condition of Q = 1, when the reaction provides the same amount of energy as it consumes, is referred to as scientific breakeven.
Most fusion reactions release at least some of their energy in a form that cannot be captured (due to entropy), so a system at Q = 1 will cool without external heating.
Therefore, a self-sustaining fusion reaction is not expected until at least Q ≈ 5.
If we can create Q >1 conditions inside a tokamak, we can remove the need for external heating.
Under these conditions, the reaction would become self-sustaining, a state known as ignition. Once a reaction reaches ignition, it could self perpetuate, like the Sun, so long as the conditions of pressure and heat are not disturbed.
We would achieve this condition by super heating hydrogen gas into the phase of matter known as “plasma” while confining it magnetically inside the donut shaped tokamak. The challenge, of course, would be maintaining the temperature and confinement required to achieve and perpetuate the fusion reaction.
Inertial Confinement Fusion (ICF)
At the National Ignition Facility (NIF) in California, 192 laser beams and 1.8 megajoules of energy is shot into a few cubic millimeters in a fraction of a second, creating conditions for fusion to occur.
Basically, it involves super heating the outer layer of a tiny sphere with intense laser energy, causing the sphere to implode and squeeze the fuel inside.
In December 2022, scientists at NIF achieved a historic milestone by conducting the first controlled fusion experiment in history to reach fusion ignition.
While not a practical way to create a fusion generator, the results at NIF show that it’s possible to create the conditions necessary for fusion to occur on Earth, given the right circumstances.
Helion’s Unique Approach
Helion uses a Field-Reversed Configuration (FRC) design to form a self-contained structure where the plasma and its associated magnetic field are entirely self-contained within the device.
The FRC shape is characterized by a closed magnetic design.
This differs from other fusion confinement concepts like tokamaks or stellarators where the magnetic field lines connect to external structures.
This enables Helion to accelerate, compress, and heat the plasma efficiently without needing to reach fusion ignition, directly recapturing electricity from the plasma for power generation.
What’s Next?
The race is on to create a Q > 1 outcome and achieve a self sustained, fusion ignition.
Commonwealth Fusion raised more than $1.8 billion in Series B funding to advance the commercialization of fusion energy, as announced in November 2021. Their goal is to provide commercially viable fusion energy by 2025.
Helion raised $500 million in funding, with Sam Altman leading the funding round by investing $375 million. Other investors include LinkedIn founder Reid Hoffman and Dustin Moskovitz, a Facebook co-founder.
ITER, the International Thermonuclear Experimental Reactor in France, is more interested in proving the scientific and technical viability of fusion as a new energy source. ITER is funded and run by seven member parties: China, the European Union, India, Japan, Russia, South Korea, and the United States.
The total construction costs for ITER up to 2025, including in-kind contributions, were estimated to be $65 billion by the U.S. Department of Energy.
The European Union contributes significantly to ITER, with a total budget of €5.61 billion allocated for the period of 2021-2027.
Conclusion
While fusion is an exciting part of the energy equation, its only one piece of the puzzle.
I expect there to be a robust energy mix that allows us to continue to scale our technology, including fossil fuels, nuclear fission, and solar arrays with peaker plants.
But a breakthrough in fusion could be the missing piece we need to help address the needs posed by data centers, crypto mining, and electric cars.
Fusion is the most exciting piece of the energy puzzle in my opinion. It’s intuitive in that its how stars perpetually retain their light and heat. It’s safe, clean, limitless, and could unlock a whole new epoch for humanity.
The future is fusion.
Thanks Matthew! Once again, you have answered one of those nagging questions I've been meaning to learn about. And, as always, your explanation is wonderfully clear. Thank you.
I'd love to read more about the tokamaks being built in France and the US. Other than the official websites, do you have any suggestions?