David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy | Lex Fridman Podcast #485

Let's start with the big picture. What is nuclear fusion, and maybe what is nuclear fission? Let's lay out the basics.

Fusion is what powers the universe. Fusion is what happens in stars, and it's where the vast amount of energy that we use today here on Earth comes from. It also powers plants. Those plants become oil, and that becomes fossil fuel that then powers the rest of human civilization for the last 100 years.

Fusion really underpins a lot of what has enabled us as humans to go forward. However, ironically, we don't do it actively here on Earth to make electricity yet. Fundamentally, what fusion is is taking the most common elements in the universe—hydrogen, lightweight isotopes of hydrogen, and helium—and fusing those together to make heavier elements.

In that process, as you combine atomic nuclei and form heavier nuclei, those nuclei are slightly lighter than the sum of the parts. That comes from a lot of the details of quantum mechanics and how those fundamental particles combine and interact. We also talk about the strong nuclear force that holds the atomic nuclei together as one of the fundamental forces involved in fusion.

But that mass defect—E=mc², as we know from Einstein—is also energy. In that process, a tremendous amount of energy is released. The actual reactions are more interesting than simply saying that it's a little bit lighter and, therefore, energy is released, but that's the fundamental process in fusion: bringing those lightweight atomic nuclei, those isotopes, together.

Fission is the exact opposite, where you're taking the heaviest elements in the universe: uranium, plutonium, and things that are so heavy and have so many internal protons and neutrons and electrons that they're barely held together at all. They're fundamentally unstable, or radioactive, and those elements are very close to falling apart.

If you take a uranium-235 or a plutonium-239 nucleus and add something new—usually a neutron, a subatomic particle that's uncharged—that unstable, very large nucleus will then break into pieces. It breaks into many pieces, a whole spectrum of pieces. If you add up all of those pieces, they also have slightly less mass than the initial uranium or plutonium did.

In that process, again, E=mc², a tremendous amount of energy is released. There's a very famous curve in atomic physics for fusion and fission, looking at the periodic table, going from the lightest elements, hydrogen, to the heaviest elements, uranium, plutonium, and others. Fusion happens up to iron.

Iron is the magical point in between, where lighter elements than iron fuse together, and heavier elements fission, or are fissile, and break apart and release energy. I think about that process in stars. Our star is fundamentally an early-stage star that's burning just hydrogen, but when it burns and does fusion, that hydrogen combines into helium.

Later-stage stars can then burn that helium and fuse it together to form even heavier elements and carbon. Those carbon atoms can fuse together and form heavier elements. That whole stellar process inspires us at Helion to think about what fusion fuels we might use—not just the simplest ones, but more advanced fusion fuels that we see in stars.

There are a million things I want to say. First, zooming out to the biggest possible picture, if you look across hundreds of millions or billions of years and all the, in my opinion, alien civilizations that are out there, they're likely going to be powered by fusion. Our advanced intelligent civilization is powered by fusion, in that the Sun is our power plant.

Then there's the physics. Again, very basic, but you said E=mc² a couple of times. Can you explain this equation?

E=mc² is a fundamental relationship that Einstein, a patent clerk, discovered. It unlocked an entire new realm of physics and engineering, and it has shown us, in atomic physics, what happens inside the nucleus. It unlocked our understanding of the universe and paved the way for many of the physics advancements that came after.

We think about mass as these particles, but in reality, at the same time, they're energy, and there's a direct quantitative relationship between how much energy is in all of that mass. In fact, all of the energy that is released in atomic reactions is E=mc². I think most people have heard of this and are used to it.

But also in chemistry and in chemical bonds, there is a change in mass. When you take hydrogen and oxygen and burn them and combine them into water, there's a change in mass. That change per atom and per molecule is actually so small that it's extremely hard to measure, but it's still there.

That's the energy that is released, and you can quantify that. We use units of electron volts as a unit of the energy in atomic processes or chemical processes.

Can you also speak to the different fuels that you mentioned, both on the fusion and fission side? Uranium and plutonium for fission, and then hydrogen isotopes for fusion?

For fission, uranium and plutonium—we don't make those nuclei. Those, right now for humanity, were made in the primordial universe through supernovae, the Big Bang, and the initial formation of the universe, where matter was created. We dig those up. We dig uranium and plutonium out of the ground.

In fact, we make most plutonium from uranium, and we can talk about how to enrich uranium if we want to go down that road. But that's how we get those elements and nuclei. For fusion materials, hydrogenic species, or hydrogen, are primordial in the universe. They're also among the most common things in the universe.

The suns and stars are made up of hydrogen and helium, and so the vast majority of atoms in the universe are still hydrogen.

So the basic fuel for fission is already in the ground, and the basic fuel for fusion is everywhere.

It is everywhere, and we particularly use a type of hydrogen called deuterium, which is a heavier isotope of hydrogen. Hydrogen is typically one proton and one electron, with an atomic mass of 1. Deuterium has an atomic mass of 2, which is a proton—a charged particle—and a neutron in its nucleus, which is an uncharged particle.

That's deuterium as the fuel. Deuterium is also found in all water on Earth—in the water I'm drinking right now. It's in my body. It's in Coca-Cola. It's everywhere. It's safe and clean, and it's one of those fundamental particles that was born in the cosmos.

We estimate that in seawater here on Earth, if we powered all of humanity's current use of electricity with fusion, we would have somewhere between 100 million years and 1 billion years of fuel in hydrogen and deuterium here on Earth.

And how is that stored, mostly?

Mostly, that's just in water. We call this heavy water, where you have the normal water that you're used to.

What we talk about and learn in school is H₂O, where there are 2 hydrogens and an oxygen in a molecule. Deuterium, or heavy water, is D₂O: 2 deuteriums and an oxygen. In reality, it's an interesting mix where you have some HDO, a mix of hydrogen and deuterium. You also have other hydrogen, but in chemistry and in chemical bonds, there is a change in mass.

On the fission side, uranium and plutonium for fission, and then hydrogen isotopes for fusion—in terms of fuel, is that correct to say?

That's correct to say at today's power level. I think what's interesting is the idea that, as we deploy the same power source that powers the universe here on Earth as humans, can we do more? Can we have access to much more electricity and much more energy, and do really interesting things with that? There are still large amounts—millions and millions of years of power—even at much higher output power levels for humanity.

Yeah, so the moment we start running out of hydrogen and helium, that means we're doing some pretty incredible things with our technology. That technology is probably going to allow us to propagate out into the universe and discover other sources, because you can also get it on other planets. Whatever planets have water, it looks more and more likely that a lot of them do. What an incredible future—out into the cosmos, nuclear power plants everywhere.

To linger on some of the technical stuff, you said strong nuclear force. So how exactly is the energy created? How does E = mc² work? How does the m go to the E in fusion?

In fusion, you take these lightweight isotopes like hydrogen and deuterium, and as you combine them and get them closer and closer together, some really interesting fundamental physics happens. First, these atomic nuclei are charged. They have an electric charge, and like charges repel. I think everybody is familiar with that: you take 2 positive charges and try to push them together, and the electromagnetic force between them repels them. You have a force that's actually pushing against them.

In fusion, you work to get your fuel very hot—very, very high temperatures, temperatures of 100 million degrees. Temperature really is kinetic energy; it's motion, it's velocity. These particles are moving so fast that, even though they're coming together and there's this repulsive electromagnetic force, they can still come close enough that another force comes into play, which is the strong force.

Once you get within a very close distance, on the order of the scale of those atomic nuclei—the tiniest thing you could imagine, and probably way smaller than that—these particles are attracted to each other, and they combine and fuse together. At that point, you create heavier atomic nuclei that have slightly less total mass in the system, and that mass becomes energy according to E = mc².

So, extremely high temperature and extremely high speed. Maybe that's one of the other differences between fusion and fission: just the amount of temperature required for the reactions. Is that accurate to say?

Yeah, and I think fundamentally, in a lot of ways, fusion is hard and fission is easy. Nuclear fission happens at room temperature. Uranium and plutonium are so likely to break apart already that simply adding one of these neutrons—one extra particle—will break them apart and release energy. If you have a lot of them together, it will create a chain reaction.

Fusion doesn't happen that way at all. Fusion is actually really hard to do. You have to overcome those electromagnetic forces to have a single fusion reaction happen. It takes things like what we have in our sun, where there is what is called gravitational confinement. Gravity—the mass of the fuel itself—is pulling toward the center of the sun, and it's pulling all that fuel together and holding and confining it such that it gets close enough and hot enough for long enough that fusion happens.

And then, if we're building fusion reactors, we have to figure out how to do that confinement without the huge size and gravity of the sun.

That's right. Obviously, the sun is vastly larger than Earth, so we can't use that same process here on Earth.

Yet. No, I'm just kidding. All right.

But we have other forces we get to use. We can use the electromagnetic force, which the sun doesn't get to do, to apply those forces.

I actually want to take a pause right there and point out a word. Historically, we've used the word “reactor” around fusion, but I don't think that's right. For me, we're really careful about this terminology. When we look at how that word is defined, and how the experts define it, it doesn't really apply to fusion.

The Nuclear Regulatory Commission, the NRC, defines it as—I have it right here—“A nuclear reactor is an apparatus other than an atomic weapon, designed or used to sustain nuclear fission in a self-supporting chain reaction.” There are 2 big parts to that: first, a fission reaction. Obviously, fusion is not that, and we've talked about why. But there's also the self-sustaining part. A reactor is self-sustaining: you take your hands off of it, and it keeps going. In fusion, that doesn't happen. We know because we have to do it every day, and it's really hard to do.

We actually use the word “generator,” because we don't talk about, for instance, a natural gas reactor. If you stop putting in fuel, it turns off. The same thing happens in fusion. We're pretty careful about making sure we talk about it as a generator, where you're putting in fuel and getting electricity out. When you stop putting in fuel, it just shuts off.

You can go even one step further and say, “What am I going to do with this fusion that powers the universe, and what does humanity want out of this?” What we want is electricity. We don't simply want a set of reactions, or even heat and energy. That's great, but what I really want is electricity.

We'll talk about the technical details. One of the big benefits of the linear design of the approach that you use is that you get to electricity directly as quickly as possible. Some of the other alternatives have an intermediate step. Those are technical details, but let me still linger on the difference between fusion and fission. What are some advantages, at a high level, of nuclear fusion as a source of energy?

Fundamentally, as a source of energy, in fusion you're taking these lightweight isotopes, bringing them together, and releasing energy. That energy is in the form of charged particles. It's already in the form of electricity. Fusion itself has electricity built into it without a lot of the steam or thermal-system requirements, and that's a really nice fundamental benefit of fusion itself.

Also, this reaction that's really hard to do turns itself off. You end up with fusion that is fundamentally safe, and that's really a key requirement of any industrial system: that it turns itself off and is safe. You turn the key off on your car, and you know it's going to turn off.

I guess the flip side of that, just stating the obvious, but it's nice to lay it out, is that for nuclear fission, it's a chain reaction, so it's hard to shut off. It works by boiling water into steam, which spins turbines and produces electricity. Can you talk through this process in a nuclear fission reactor?

In a nuclear fission reactor, you put enough of this fissile material—uranium or plutonium—together such that, as these unstable atoms crack open and break apart, they release heat. The component parts that the uranium breaks into are actually quite hot. It also releases neutrons, more of these uncharged particles.

If you do it right, this fissile material will be next to other fissile material, and that neutron will go and bombard another uranium nucleus, again opening it up and releasing more heat and more of these neutrons. That's how you have a self-supporting chain reaction, and that chain reaction then continues.

People design fission reactors so that you have just the right balance: enough neutrons are made for the reaction to continue, but not so many that it speeds up, because you don't want it to speed up.

And there's some kind of cooling mechanisms also? That's part of the art and the engineering of it?

At the same time, you want to make sure that the whole thing is in water, which is typically the cooling fluid. There are some more advanced fission reactors that have different cooling fluids, but water is typical. It absorbs both the heat and those extra neutrons.

And so you use the water and the fluid to extract the extra neutrons, and then run a steam turbine to do traditional electricity generation and output electricity through your steam turbine. You end up with complicated systems of flowing liquids and flowing water, balancing the heat.

A lot of fission reactor design comes from that thermal balance of keeping this reaction going, making sure it doesn't speed up, because that's an uncontrolled chain reaction, which you would not want, and balancing the cooling and the output of getting the water out of it.

So we should say that, for reasons you already laid out—and maybe you can speak to it a bit more—nuclear fusion is much safer. There's no chain reaction going on. You can just shut it off.

But it should also be said that, as far as I understand, the current fission nuclear reactors are also very safe. I think there's a perception that nuclear fission reactors are unsafe and dangerous. If you just look empirically at the statistics, the fear is not justified by the actual safety data. Can you just speak to that a little bit?

Yeah. We've been talking about the reaction processes themselves, but I think fundamentally, let's take a step back and look a little broader and say, “Let's look at what we care about,” which is the power plant making electricity. I look at this from a nuclear engineer's point of view. I spent a lot of years studying these systems.

Modern fission reactors, I believe, are engineered to be safe. They're engineered in ways where, as those reactions maybe speed up and those systems get hotter, they actually are built to expand and cool down passively and naturally. There are protection systems in place, and modern systems are quite safe from an engineering perspective.

I believe that we have figured out how to build nuclear fission reactors in a way where the engineering of the power plant is safe. I would say that I look back at the history of what we've built over time, and the challenge hasn't come from the engineering, actually. I believe the engineers have solved these problems.

The problem comes from humans, and the problem comes from other things around nuclear power. You have to enrich that uranium to put it in a plant. The plant's safe, but you had to enrich that uranium, and that is some of the problem.

Or a plant is designed to run for a certain number of decades safely, but do we run it longer than that? Those are where I think the real challenges happen: more with the humans around these systems than the engineering of the power plants themselves.

Well, I have to ask then: What do you think happened in Chernobyl? What lessons do we learn from the Chernobyl nuclear disaster, and maybe also the Three Mile Island and Fukushima accidents? I think you're suggesting that it has to do with the humans a bit.

So, with Chernobyl and Fukushima, I actually put Three Mile Island in a different category. In fact, some of the recent news in the last year is that we're going to be restarting Three Mile Island because there's such a need for clean baseload power. That's actually a very interesting other topic we should talk about: why and how we're doing that.

But going back to the accidents that did happen in both of those systems, you can point to the human failure rather than the engineering failures of those systems. In Fukushima specifically, there were multiple nuclear fission reactors on the same site that successfully kept running through the tsunami—totally successfully—and were only later shut down for more political reasons.

The oldest one, which had been on-site for a long period, and maybe too long—I think some experts have looked at this in the past—was where some of the problems actually happened. I look to that less as a failure of the engineering of the power plants and more as a failure of the humans around those systems.

We should be operating these plants as designed, and then I believe they're safe. That gets to some of the atomic weapons questions that I think are the other part around nuclear reactors and fission reactors that are concerning for me.

Can you speak to those? Maybe this is a good place to also lay out the difference between nuclear fission power plants and nuclear fission weapons, and maybe also nuclear fusion power plants and nuclear fusion weapons. What are the differences here?

Fusion power plants can't be used to make nuclear weapons. Fundamentally, the processes in fusion aren't the same processes that happen in nuclear bombs and nuclear weapons. It's actually one reason I started in fusion, and most of our team thinks about the mission of fusion—of delivering clean, safe electricity—is that it also can't be used to make weapons.

I think that's a little bit of a distinction from traditional nuclear fission reactors. While I totally believe, as a nuclear engineer, that we can build power plants now that are safe and aren't going to have reactions, they use a fuel—uranium and plutonium—that can be used to make nuclear weapons.

We know that if you take enough fissile material together—enough uranium and plutonium—and put it in a small volume, it will not just create a reaction, but it will create a supercritical reaction that will then continue and grow and release a tremendous amount of energy all at once. That is a bomb. That is a bad situation, and that is what we want to avoid.

A lot of the key is recognizing that, even though there are things called fusion bombs—the H-bomb, the hydrogen bomb—the hydrogen bomb has uranium in it. It's still a fission bomb.

Fundamentally, this works because you have a fission reaction, a primary, and that creates radiation that induces a fusion reaction with a small amount of fusion fuel that then boosts that uranium reaction again. Most of the energy—in fact, 90% of the energy in an H-bomb—is still from the uranium reactions themselves.

Yeah, I think people call it a nuclear fusion bomb, a hydrogen bomb, but really it's still a nuclear fission bomb. It's just that fusion is a part of the process to make it more powerful, but you still need, like you said, the uranium fuel. So it's not accurate to think of it as a fusion bomb, really.

And if you take away that fissile material—that nuclear fission reaction—the fusion reaction doesn't happen at all. In fact, researchers have over the decades tried to make an all-fusion bomb and been very unsuccessful at it. The physics and the engineering don't support it ever happening, with our understanding today.

The topic we're talking about is more broadly called proliferation. This is the creation of nuclear weapons in the world and the distribution of those weapons. Something we know as physicists and engineers is that fusion can't be used to make nuclear weapons. We know that, but that is not widely known.

Part of what we went out to do was work with the proliferation experts in the world—the people who work to prevent nuclear weapons from being made, created, and shared throughout the world—because we know the geopolitical challenges that happen.

We went to those proliferation experts, and we were worried they would have the same historical question: “Well, the word nuclear is in fusion, so therefore it must be related.” In fact, the total opposite happened. What they told us is, “Please, please go develop fusion power plants absolutely as fast as possible. The world needs this.”

The proliferation experts were telling us that otherwise people would start enriching uranium throughout the world, and we'd be building enriched-uranium power plants because we need electricity that's clean and baseload.

But in those processes, they'll be making fuel that could one day be used for atomic weapons. They were worried that the growth of enriched uranium—think about the centrifuges, and having a lot more centrifuges all over the world—would lead to more weapons, or at least the possibility of more weapons. And so they're pushing us as fast as possible: Go build fusion generators and get them deployed everywhere.

Not just in the United States, but all over the world, so that we're building fusion power and meeting humanity's needs—not this other thing. I was really pleasantly surprised. We've written a number of papers and worked with those communities on this: What does it mean? How is fusion power safe and unable to be used for nuclear weapons?

This might be interesting to ask on the geopolitics side of things. I have the chance to interview a few world leaders coming up. By way of advice, what questions should I ask world leaders to figure out the geopolitics of nuclear proliferation, nuclear weapons, nuclear fission power plants, and nuclear fusion power plants? What's the interesting, intricate complexity there that you could maybe speak to?

The question I would want to ask is: “What would you do if we could deliver for you low-cost, clean, industrial-scale—tens or hundreds of megawatts of fusion power that's low-cost, clean, baseload, and doesn't have the geopolitical consequences of uranium and plutonium, of fissile material? What would you do there? How would that change your view of the next 30 years?”

But there's also a lot of geopolitics connected to oil, natural gas, and other sources of energy, which I think are important in Saudi Arabia, in the Middle East, in Russia—I mean, all across the world. That's interesting too. Do you think that if everybody has nuclear fusion power plants, it alleviates some of the geopolitical tensions that have to do with energy and other energy sources?

I certainly do. The fuel is in seawater all over Earth. Everybody has deuterium, and everybody has it, so you can't have a monopoly on the fuel. No one can control the fuel, no one can turn off the fuel, and no one can cut a pipeline. That just cannot happen with fusion.

If we can deploy those plants quickly, then it decouples the ability of any one or any few countries to control energy.

Let's return to the basic question. We already mentioned it a little bit, but is nuclear fusion safe? The power plants that we're talking about—fusion power plants—are they safe?

Yes. Fusion power is fundamentally safe. The physics and the reactions of the fusion system itself mean you don't have runaways. We've talked about some of the human factors around power plants, power systems, and industrial-scale systems, and that's something that we build into the design of these systems from the beginning.

We look at how these systems might fail. In fact, we did this analysis for the Nuclear Regulatory Commission over the last few years, looking at how to regulate fusion power. As we're building the first fusion power plant, we need to make sure we're regulated safely, so we spent a lot of time doing the technical and political case in the United States for how to regulate fusion.

The analysis we did assumes you have a fusion power plant that's operating, and then, at any one time, a meteor strikes it. The whole thing is vaporized. What is the impact of that? This is worse than you could ever imagine an actual physical scenario, but let's start there. The answer is that you don't need to evacuate the populace near the fusion power plant.

One of the keys I come to when I think about this is the fuel. In a fusion generator, you're continuously feeding in this hydrogen, these deuterium fuels. At any one time in a Helion fusion system, and in most fusion systems, you have one second of fuel in that system.

What that means is that if you stop putting fuel into the system, fusion just stops. But it also means that if something really catastrophic happened, for whatever reason, all that fuel is not in the system. If you hit it with a meteor or do anything of that nature, fusion doesn't happen. That hydrogen, that heavy water, that deuterium just goes back into the environment safely and cleanly, without issue.

That's the fundamental safety mechanism of fusion. You can compare that with other types of power plants, such as an oil or coal power plant. You might have a large pile of coal that catches fire and burns. It's not catastrophic, but you have a large coal fire for a long time, releasing toxic fumes that you may have to deal with.

In a nuclear fission power plant, you may have several years of fuel sitting in the core. In that case, if something bad happened, you have all that potential energy for things to happen. But in fusion, you have literally one second of fuel at any time in the system. Having a tank of deuterium, which we have around all the time, can't do fusion by itself. It needs that complex system.

I love that there's a PowerPoint going on in a secret meeting about what happens if a meteor hits a fusion power plant. That's really interesting. What about the waste? What kind of waste is there for fusion power plants?

The fusion reaction itself is still fundamentally an atomic reaction. During this reaction, you do create ionizing radiation. You create X-rays, you create neutrons, and you create all these charged particles.

The charged particles themselves, for a fusion reaction, are all contained in the fusion system. The X-rays—similar to those in a dentist's office, although a lot more than that—are absorbed by the fusion system. The thing we do care about is the neutrons.

In a fusion system, we do have activation. During its operation, neutrons are made and leave, so we have to shield these fusion systems during their operation. This is very similar to—and, in fact, this was a lot of the work we did with—the Nuclear Regulatory Commission over the last several years.

There was a landmark agreement at the NRC that was codified into law last year, called the ADVANCE Act. It's really powerful because it says, for the very first time, how the U.S. government—leading the way on this, which I'm really proud of—will regulate fusion.

This gets into a little bit of the details. The way the Nuclear Regulatory Commission regulates nuclear things in the United States is through different sets of statutes. Nuclear reactors are regulated under something called Part 50. There's a lot of variety in the regulatory language around that, but most of it is designed to handle special nuclear materials, uranium and plutonium.

Fusion is not. Fusion is regulated under something called Part 30. Part 30 is how hospitals, particle accelerators, and other types of irradiators are regulated. As they're operating, you have very high-energy particles and ionizing radiation, and you have to protect operators from it. You have to shield them, so we build concrete shields.

If you came and visited Helion, you would see plastic, borated polyethylene and concrete shielding to protect operators and equipment from the fusion reactions while they're happening. Again, you turn them off, and those fusion reactions stop. That's really the key.

There's a funny story related to that. We've been building fusion systems that do fusion for a long time, and at some level, they got powerful enough and were doing enough fusion that we started building these shields and shielding them like a particle accelerator.

I went to the regulatory bodies that regulate Part 30. This was in Washington State; it's the Department of Health. I went to the Department of Health and said, “Here's an application for a fusion generator shielding permit as a particle accelerator.”

The very first question I was asked was, “Great. Where do the patients go?” The standard form had a patient, as in a hospital, the patient dose for the particle accelerator, and then the shielding. We talked all about the shielding and the operators, which is very similar for a Helion system. We said, “No, no patients at all. No one's inside this thing. Our goal is to generate electricity one day.” This was a lot of years ago.

We were able to work with the state agencies to license these fusion particle accelerators. We were, as far as we know, the first licensed fusion system ever as a particle accelerator. The first license we had was in 2020. Since then, we've gone on to license several of our fusion systems that we've built that do fusion, including both the shielding and some of the fuel processes.

At a high level, what are the different ways to build a nuclear fusion power plant? Can you explain what a tokamak is, what a stellarator is, and what the linear approach that Helion is using involves?

There are a number of ways to do fusion. Fundamentally, in all fusion approaches, you're trying to do the same physical process: take these lightweight isotopes, heat them up so that they can move at high velocity—over 100 million degrees—bring enough of them together, which we call density, so that you have reactions happening at a higher rate, and keep them together long enough that they're able to collide into each other, do fusion, and release energy.

That's the fundamental core. How you do that—how you bring those particles together and how you hold them together long enough—there's a wide range of technologies that, as humans, we've been exploring since the 1950s.

And I think about several main categories. If you look at the fusion funding out there, government funding in the world, private funding actually has quite a different profile, which is an interesting thing to talk about. But in public funding, in federal funding in the United States, there are 2 mainline programs called inertial fusion and magnetic fusion.

In inertial fusion, what you're trying to do is bring together and push together, by a variety of physical means, those particles. You push them together. The most common is called laser inertial fusion. Our colleagues at the National Ignition Facility did this really well and made world records in the last few years, demonstrating that you can do this at scale. You take very high-power lasers and pulse them together to combine them to do fusion for a pulse, for a very short period of time—nanoseconds, billionths of a second.

The other extreme—and you mentioned tokamaks and stellarators—stellarators are actually my favorite, so we'll talk about those. As a graduate student in fusion, the stellarator is the first thing you learn about because there's a mathematical solution for a stellarator that solves perfectly. You can write it out and solve it, and analytically, it's very simple. Building one is very hard. It's taken humanity a number of decades to be able to build stellarators, and we can do it now with the Wendelstein 7-X, which came online in the last few years and is the premier stellarator in the world.

I should say, all the different ways to do fusion just look so badass in terms of engineering: creating this containment, extremely high temperature, high density. Everything's moving super fast. Everything is happening super fast. It's just fascinating that humans are able to do it. There are certain things, accelerators, that do a little bit of that, but this is even cooler because you're generating energy that can power humanity with this machine.

Anyway, can you just speak a little bit more to the inertial and the magnetic fusion systems?

In a magnetic system, your goal is not to push together those particles as fast as possible. Your goal is to hold on to them for as long as possible. To do that, we use magnetic fields.

Let's take a step back. What is a magnetic field? In an electromagnet, there are a variety of ways to make a magnetic field. One of the most famous, I think everyone is familiar with, is Earth itself. Earth has what we call the magnetosphere, which is the magnetic protection that's generated by the core of the Earth. We have a magnetic field around the Earth, and that magnetic field protects us from particles coming from the galaxy—galactic cosmic rays and solar particles that would come to Earth.

When you run a compass, you see the magnetic field from the Earth. So we know it's happening. It's all over. But how we generate it with electric currents is a little bit different. We have a loop of wire, and the simplest way to think about it is literally a round loop. In that loop, you have electrons. You have electrical current that's running. When you have an electrical current in a wire—it’s some of Maxwell's equations that we discovered in the 1800s—it generates a magnetic field inside that wire.

When you look at fusion systems, you always have these big magnetic coils with large amounts of current. We don't run a little bit of current. In our systems, we have hundreds of mega amps of current. If you think about your house, you have your breaker box with 200 amps or maybe a 400-amp breaker box, and we run 100 million amps of electrical current. So, massive amounts of electrical current to be able to do this.

That magnetic field that's generated inside that magnetic coil has some really special properties, and we take advantage of those properties to do fusion. Some of those properties are not intuitive. So here's one of my favorites: when you have an electromagnetic field, you have this coil with electricity going around it and you have a magnetic field inside of it, and then you have a test particle—a charged particle, an electron or an ion. If you imagine generating this, I have a coil with electrons moving around it. But if I put one in the middle of it, in this magnetic field, some really interesting things happen.

That electron or that ion, that charged particle, is what's called magnetized. What magnetized means is that it's trapped on that field line. In fact, even more interesting is that it oscillates around that field line. The way I think about this is, if you think about the Earth's magnetosphere again, and you think about the charged particles—the aurora, the northern lights—that is a charged particle trapped in the Earth's magnetic field, going around the Earth's magnetic field.

In the same way, in fusion, we do the same thing here on Earth, but in a smaller configuration, where we trap these particles on magnetic fields, and they can go around and stay trapped to that magnetic field line.

How much of the physics at this scale is understood here—how these systems behave when you interact with a magnetic field in this way? Is this fundamentally now an engineering problem, or is there new physics to be discovered about how the system is behaving?

In fusion, the physics we're using is actually quite old. The fundamental electromagnetic physics is 1800s physics. The fundamental atomic physics is early-1900s physics. So the fundamental physics of how these work is very well understood. Putting them all together into a power plant, that's hard.

You can do the math. Every introductory graduate student does the math on a stellarator and says, "This is all I need to do. I just need to make a magnetic coil in this very complicated shape, and then fusion will happen." However, doing that in practice is actually quite challenging.

So maybe you could speak a little bit more about the stellarator and the tokamak. What's the difference between those two? They're both magnetic fusion systems? And then what does Helion do?

The tokamak and the stellarator are both magnetic systems. Their goal is to generate this magnetic field and hold on to the fusion fuel long enough. As I mentioned, these charged particles are trapped on the magnetic field. In fact, they're oscillating. We call that a gyro-orbit, which is the radius that they oscillate around in this magnetic field.

We've been talking about atomic physics, where everything is at the nanoscale. But gyro-orbits are not. Gyro-orbits for these fusion particles are measured in inches, so they're on a scale that we can see, measure, and understand really intuitively.

In a magnetic system, your goal is to simply trap as many of these particles as you can for long enough, and heat them so they're hot enough that they bang into each other. They collide enough that you're doing fusion, and you're doing enough fusion to overcome the rate at which you're losing those particles. That's what happens when you put particles in a magnetic field and try to hold on to them.

The challenge is that it's really hard to hold on to them long enough. These particles are moving around. They're moving at very high velocity—millions of miles per hour. They're colliding with each other, and they're getting knocked off and getting knocked away.

We've talked about inertial fusion, where you try to confine a fusion plasma by crushing it as fast as possible, and magnetic fusion, where you simply have a magnetic field and your goal is to hold on to it for as long as possible. But there's another way to do fusion, and in some ways, it's one of the earliest approaches for fusion that was successful.

As scientists and engineers, maybe we're not too creative with the terminology. We call the technique that Helion uses magneto-inertial fusion because it does a little bit of both. To understand that, we can actually go back in history a little bit and think about the evolution of some of these approaches to fusion.

From our perspective, we look at the technology that we use as being built on physics experiments that were very successful in the 1950s. In those systems, the earliest pioneers of fusion said, "I know. We understand the physics. We have to take these gases, heat them to 100 million degrees, and then confine them—push them together so that fusion happens." So, what is the best way to do that?

Some of the earliest programs were called theta pinch. Those programs used a linear topology because we knew how to build these magnets. It's called a solenoid, where you take a series of electric coils, run electrical current through them, and that generates a magnetic field. Great, so you have a magnetic field. Now you add your fusion particles. Okay, so you've added fusion particles to this solenoid.

Here's the challenge: those particles, as they're sitting in that magnetic field in this nice magnet, escape. They leave out the ends because there's nothing holding them in. Great, so that makes sense. And so that doesn't work.

Then the next approach was to say, "Well, one branch of fusion said, 'Okay, to solve that, why don't we take the solenoid and bend it around? Let's just make it a big donut. So as they're escaping, they go around and around in a circle.'"

Great. That's a great approach. And so one branch of fusion went down that direction, and that evolved into the stellarator and the tokamak—different ways of taking those solenoids and wrapping them around so that the plasmas go round and round in that magnetic field and are held, those charged particles are held, long enough that fusion happens.

But there's a different way to do it. The theta pinch was born in the 1950s from the idea: "Take this magnetic field and—oh, they're trying to escape. Great. Let's not let them escape. Let's close the bottle—"

Mm-hmm.

Let's close the ends. And so we make the magnetic field much stronger at the ends. This was called the mirror, and the idea was that the particles would bounce in between. That worked, and they got hotter and hotter and hotter.

But as you might imagine, as the pressure increased inside this mirror topology, this linear topology, the particle pressure tried to push back on the magnetic field. The particles were trying to escape. They were getting hotter and hotter, and just as hot gas in a balloon tries to get out the ends, you could not hold it tight enough at the ends to keep those particles in. In fact, the hottest ones were the ones that would escape.

Mm-hmm.

And so you do a good job of heating it, and they all leave out the ends. Okay? So then the next iteration said, "Why don't we just not try to hold onto it very long? Why don't we squeeze it?" Rather than just holding it constantly, let's now crush it.

So we built this solenoid, pinched the ends, and then crushed it. What I mean by crushing it is not actually crushing any magnets, changing the topology, or moving any parts, but just rapidly increasing the magnetic field. Going from a magnetic field that's just holding it to now taking all those particles—if you imagine they were streaming around together—and rapidly increasing the magnetic field so that those particles get closer and closer together.

So you increase the density, and now fusion starts to really happen. But they ended up hitting a technological limit. This is the part that I look back on, and I look at the pioneers. In 1958, there was some pioneering work done in California, at what later became Livermore Labs. There was also work done at other national labs. These were all federally funded programs to explore this theta-pinch topology: Can you just squeeze the plasma down fast enough and hard enough?

This was 1958. The transistor was sitting in the laboratory, and they were turning on millions of amps of electrical current. They were doing it—we haven't talked about the time scales—in millionths of a second: microseconds, megahertz speeds. This was in 1958: no transistor, no CPUs, and no electrical switches—none of the things that I take for granted every day.

They were able to show, at that time, the highest-performing fusion systems. They didn't get to 100 million degrees, not quite then, but they got to 50 million degrees. They were outperforming everything else in fusion, but they reached the technical limit where they just could not build it anymore.

So those pioneers went in a different direction, and they started down the laser-inertial path, saying, "We can't do these electromagnetic pinches, but now this new thing, the laser, has been invented. It turns on in nanoseconds. It's fast. It's interesting. Let's go down that path."

It takes a couple of decades to fast-forward to when researchers found that, with some of these theta pinches operated in a very specific way, something else happened—something new happened. Before, when they squeezed these plasmas very hard, just like squeezing a tube of toothpaste, they squirted out the ends. Now they didn't squirt out the ends. They actually pushed back. They stayed confined. They stayed trapped inside that linear topology. Even though the ends were open, the plasma didn't leave.

And so there were a large number of programs asking, "What is happening here?" This was an accidental discovery in plasma physics that something new was happening. What we discovered is now called the field-reversed configuration. There are numerous FRC, or field-reversed configuration, programs both at national labs and at private companies. There are actually a number of private companies now building field-reversed configurations.

They have some really unique properties, but fundamentally, talking about the main difference, I describe the solenoid as having magnetic fields throughout the center of that volume, with plasma trapped going back and forth. But some other things can happen, which is really interesting.

What they discovered early is that if they have a field going in one direction—the electrical current is going around the loop, and the plasma is going back and forth along this magnetic field line inside that solenoid, inside that theta pinch—but then they change the direction of the magnetic field, this is what we call field reversal. This is really the key: You start with the plasma going in one direction, and then, very rapidly, you change the direction. You change and reverse the direction of that field.

Something really interesting happens. The plasma—this fusion fuel, these charged particles trapped on the magnetic field lines and moving back and forth—you change the direction. What that means is that you're trying to take that electrical current and that magnetic field and reverse their direction, flip them, but they can't flip fast enough. The plasma is sitting there, and you can't move the particles.

What's really interesting is that, because the particles can't move but you've now flipped the direction of the magnetic field, you've inverted it. Something really unique happens: The plasma itself reconnects internally. Now what you're left with is an outside magnetic field, an electrical coil, and inside, the plasma—which before was moving along is now moving internally.

Rapidly reversing the magnetic field, the plasma self-organizes into a closed field. What? How?

It sounds wild.

Yeah. So, first of all, there are a million questions I have. One of them is: What's "rapidly"? What time scale are we talking about here?

Mm-hmm. You have to reverse the electrical current faster than a million-degree gas particle can move.

Okay.

We have to do it on the order of a millionth of a second.

Wow.

We have to do it in a millionth of a second.

Wow.

In practice, this is hard. We can only do it now because of semiconductor switching. We can move things; we can switch things. The transistor in every CPU in a computer switches at a gigahertz. That means that in a nanosecond, it's switching—in a billionth of a second.

We didn't have that in the 1950s, when these theta pinches were invented, but now we have the semiconductors to be able to do that.

The self-organizing plasma—can you just speak to that? What the heck is it doing? How do we discover, how do we understand, the self-organizing mechanism—the dynamics of the plasma that's able to contain itself?

What I like to do is use an analogy here. Once you've made it, it's actually somewhat straightforward to understand. Getting to it is tricky, and how they discovered it the first time is absolutely amazing. But once you've made it, it's a lot more straightforward to understand.

In a magnetic coil, when you have a round electrical coil, you have electrical current flowing in that coil. If you have another conductor—a metal inside that coil—this is called Lenz's law, in one of Maxwell's equations: As you have electrons and current flowing in that coil, an equal and opposite electrical current is induced in a piece of metal nearby.

This is the same thing that happens in a transformer, where you have a primary with electricity flowing in it and a secondary where electricity flows in exactly the opposite direction. We use this every day in our lives.

In this condition, you have a conductor—an electrical conductor where current can flow—and you have an electrical current flowing on the outside. Electrical current flows on the inside. I've described two pieces of metal. Now let's go one step further: That inner conductor is not a piece of metal anymore. It's one of these high-temperature gases, this plasma, these charged particles.

Now you have electrical current flowing in the plasma. This is really interesting. We talked about these charges moving back and forth. Moving electrical charges are current. So in every plasma condition we've talked about—the tokamak, the theta pinch, and the stellarator—there's electrical current flowing in the plasma.

But in the field-reversed configuration, you have a lot of electrical current flowing in the plasma—massive amounts of it. That's the key. You have the center core, where electrical current is flowing in this transformer, if you want to think about it: primary and secondary.

Here's the craziest part of it. This electrical current—how did I describe a magnet? An electromagnet is a loop that has electrical current flowing in it that generates a magnetic field. For a theta pinch, a mirror, and a tokamak, the plasma gets trapped in that magnetic field. But in an FRC, this electrical current is the plasma.

That plasma then generates its own magnetic field, and it's trapped on its own magnetic field.

That's fascinating.

And that's the key. In your tokamak, in your donut, in your stellarator—in your funky donut—you make the magnets and trap your plasma in them. In an FRC, you make the plasma, which makes the magnets, and it traps itself.

The craziest part of this, in my mind, is that we actually see this in nature all the time. If you look at the sun, we see solar flares.

In a solar flare, we've all seen the pictures of the photosphere of the sun and this large arc of plasma coming out. That plasma has electrical current flowing in it, and then we see this solar flare rip off of the sun. That solar flare can then flow throughout and continue into the solar system, and for a little while, anyway, it makes something called a plasmoid.

That plasmoid is, in fact, electrical current flowing in the plasma, generating a magnetic field and holding it for longer than it would otherwise. So, we've observed these for 100 years, and we've known about these plasmoids for a long time. Researchers have tried intentionally to make them, but fundamentally, that's what we do every day: make one of these self-organized, closed-field plasmas.

In a more controlled way, at this rapid rate of one-millionth of a second, and being able to make sure it's reliable, stable, and all that kind of stuff. So, by the way, how do you keep the thing stable?

And there's the hard part, because I just described a solar flare. Yes, we've seen the pictures of them, but we've also watched them, and they appear, fly away from the sun, and then go away. That's not what we want in fusion, right? We want to be able to control this. That's the hard part of the job.

So, that's what we've spent the last number of years learning how to do, ourselves and others, on these pulsed, closed-field FRC systems.

Hmm.

Let's first talk about how to make them, and then we'll talk about how to make them stable, because they're 2 different things, and we spend a lot of time on both.

So, we talked about timescales. You have to reverse the field. You have to change the electrical current in one-millionth of a second. So, how do you do that?

I've described this system as having a series of magnets. You have a magnetic field on the outside, and then on the inside of this, you have this donut, this FRC, that has its own electrical current. We didn't talk about this yet, but it has generated a magnetic field, and that magnetic field has pressure. This is the other thing that's really interesting.

We talked about how this theta pinch compresses a plasma. It applies pressure on the outside, but the plasma itself has pressure on the inside. It has both a particle pressure—the particles literally bouncing. Think about hot gas in a balloon: the particles expanding, the ideal gas law expanding and contracting inside a balloon. But they also have a magnetic pressure. The electromagnetism is pushing back.

I like to think about this as the motor in a Tesla. In your electric car, you have a motor, an electric motor, and what that motor has is a series of windings. You flow electrical current through those windings, in this case from a battery. You hit the gas, electricity flows from the battery into the motor, into those windings, and it generates an electromagnetic force. A Lorentz force is what it's technically called.

This electromagnetic force induces an electrical current on the armature, on the shaft. This is getting into the details, but in the armature of an electrical motor, that actually is what spins. The outside of a motor doesn't spin. You flow electrical current through it, and the inside spins. That electromagnetic force is what spins that armature.

In our case, we're inducing an electrical force in that electromagnet, and that's putting an electrical current, just like in the armature, into that plasma. We can use that force to do interesting things. That electromagnetic force can compress the fusion plasma. It can expand the fusion plasma.

But here's the problem: it's unstable. This is something you learn very early in your graduate work as a student in fusion. You learn about plasmas that are called high-beta plasmas.

I keep seeing this plasma-beta thing everywhere. What is this ratio of plasma field energy to confining magnetic field energy? Please explain.

Plasma beta is the ratio of the magnetic pressure to the particle pressure. What that fundamentally means is, I talked about how you have a magnetic field, and in that magnetic field, plasma is trapped on that magnetic field. But it's not very well trapped. It can escape. It can leave either down the ends—it can freely travel—or it can also travel across the magnetic field.

We have a term called plasma beta, which gives us an understanding of how well trapped that plasma is. As you apply a magnetic pressure, a magnetic field, to this plasma, it pushes back. Does it push back a little, or does it push back a lot?

For a field-reversed configuration, in one of our plasmas, beta is very close to 1. In fact, usually by definition, it's 1 at any point in the system. That means that every time I apply a magnetic force on this donut to compress it, the plasma particles on the inside push back.

What's really interesting is that you have an equation for magnetic pressure, which is B² over 2μ₀. The magnetic field squared is the external magnetic pressure. Any magnetic field anywhere generates this pressure. But the plasma particles themselves also have a pressure. This is the ideal gas law, and we use the definition n k T—density, Boltzmann constant, and temperature—for pressure.

In high beta, they're the same: B² over 2μ₀ is n k T. So, for a known magnetic field, I know what the density and temperature of the plasma are. Just to circle back to it, when we talked about fusion, we talked about it having to be hot enough and dense enough. That's n and T.

Now I have a very clear equation between magnetic field and the density and temperature of the fusion fuel, and that's really critical. All plasmas have some beta, some number. All fusion plasmas have some beta. The FRC has one of the highest betas: beta equal to 1.

However, what you also learn in school when you learn about beta for the first time is that high-beta plasmas are typically unstable. The good way to think about this is that a tokamak is an accelerator that is stable, because those plasmas that are going around in the donut—there's a force on that donut—but that plasma donut is very well held by all those magnetic fields, by all those magnetic coils. If it tried to move, it would be confined by those magnetic coils.

But in an FRC, it's unconfined. The plasma is confined, but the whole topology can do something that is called tilt. This whole plasma donut, because it's under pressure, can just turn over.

The way I think about this is that a motor is a good example. In the center of your motor, you have a spinning armature. You have this spinning magnet on the inside, and it is held by the main axis of the magnet. It can't go anywhere. We don't have that axis. We don't have any mechanical things inside these fusion systems. They're 100 million degrees. You can't put any mechanical things inside them, so we have nothing to hold onto it, and it's unstable.

So, when you learn about the FRC, that's the first thing you learn. It took us a number of years to learn about a parameter for how to make them stable, and that's pretty fundamental. But most people who've heard of an FRC haven't understood this really key fact.

We have a parameter we call S star over E. We're getting really into the physics weeds here, but—

Let's go.

It's really important, and the good analogy here is a top—literally, a top. You have a top spinning on your desk. You know that it'll spin for a little while and then fall over. It is unstable.

However, if you spin it fast enough—if you take a top and spin it fast enough, with enough angular momentum, enough angular inertia in that system—it'll stay upright, even though it wants to just fall over, even though it's unstable. We do the same thing in an FRC: if you can drive it fast enough, if you can add enough kinetic energy and inertia to the particles, it will stay stable.

However, you can do another really key thing. We are not limited now to having a very skinny top. We can actually make it much bigger. The good analogy here is that if you have a coin and you're spinning that coin, if you spin it faster and faster, it'll stay spinning longer. However, eventually it'll slow down and fall over.

But if you had a roll of duct tape—if you had something thicker and heavier and longer—and it's spinning around that same axis, it'll stay spinning even longer, both because of the inertia and because of the geometry.

So, we have this parameter called S star over E. S star is the hybrid kinetic parameter, which tells you how stable it is from that top point of view, and the E is the elongation, or how long it is.

Maybe fortuitously—thank you, nature—you gave us a win here, which is that how we make these in these long solenoids is naturally very, very long. We can build these with very long lengths, and if we can drive them fast enough and hard enough, and drive the ions to move at very high velocities, we can stabilize against those instabilities and hold them stable.

We now know we can design, with a given S star over E parameter, systems that can last for very long lifetimes. The theory of the systems we make says that they should last for a few microseconds at most. We and others in the field have been able to make them last for thousands of microseconds—thousands of times what the stability criteria, the basic criteria, would tell you.

So, we know now how to do this, and we design them with this built into them.

Can you explain a little bit more about the S star over E? Are you given that, or is that an emergent thing? At which stage is that the result or the requirement?

It's a great question. It is a requirement of the system. You must design it with this parameter in mind.

Got it.

The hard part is that you have to design it with S star over E being satisfied the whole time.

Right.

Here's the extra trick here.

S star over E is also a measure of temperature.

Oh boy.

Yep, it all comes back to temperature. The hotter you make them—the same thing, temperature as kinetic energy—the faster you're spinning. So if you take your top and spin it faster, it's more stable. But you've got to make it hot, and so here's the trick: How do you make something hot that's starting cold? It has to be hot by definition.

That's part of the challenge of what we do day to day: getting to these hot plasmas. The reason other people have tried to make FRCs and haven't been very successful is that they couldn't get it hot enough, fast enough. It fell over, it tilted, before it got hot.

And so we spend a lot of our electrical engineering—in some ways, Helion is more of an electrical engineering company than a fusion company some days—focusing on how to make the electronics fast enough to get it hot enough, soon enough, that you can keep it stable the whole time.

So you're trying to reach 100 million degrees. How do you get to that temperature fast? And, by the way, what can you say to help somebody like me understand what 100 million degrees is like? It seems insane. What does that world look like? I guess everything is moving very fast, as you said. You can't put anything mechanical in there.

A couple of key things happen. When gas is that hot, we talk about the states of matter. You have solids, like ice, where it's cold. The atoms are bound in a lattice structure together; they're held together. Then, in a liquid, you've broken a lot of that lattice structure. The atoms can move around and have some kinetic energy, but they're still pretty contained. They stay in the bowl.

Keep heating it, and now you're in a gas. These particles are free to move around, and they're bouncing off of each other all the time. You can keep heating it from there, and that's where we talk about some more phases of matter.

We can add a little bit more physics here. We talk about rarefied gases. When we think about most gases that humans interact with, they act like a fluid. What I mean by that is that they're colliding with each other so often that the particles at any one place—the air here—is roughly the same temperature as the air there. These particles are bouncing off of each other. If you put a really hot one right here, it would then cool enough that all the air would be roughly at the same temperature.

But you can be what is called rarefied, and this is like space. Now you have particles moving around, but they don't collide with each other very often. You can have one very high-energy particle and a very low-energy particle, and they may not even touch each other. Maybe occasionally they bang into each other, they collide, and then they transfer energy. That's what we call rarefied.

Then you can go even hotter than that. Now the actual atomic structure—which has a nucleus, consisting of a proton and a neutron, and an electron—gets so hot that the electron gets energized and then escapes, leaving the system. Now they're charged. You have a positive nucleus and a negative electron floating out, and that happens on the order of 10,000 degrees. That's way hotter than what we're used to.

But now we're going to go hotter. We're going to take this plasma and go even hotter. What does that mean? At that point, a lot of the way we think about temperature doesn't really apply. The idea that you have random motion of particles doesn't really apply, because now they're all individual particles moving at very high velocities. There really is a measurement of its velocity; it's really a measurement of how fast that particle is moving. That's how I think about temperature when you get to 100 million degrees.

It does some more complex things. If you have this high-energy particle moving at a high velocity and another one moving at a high velocity, they will come together, collide, and fuse. But other things will happen. You don't want to touch that high-velocity particle with any kind of material, because it will collide with that material, damage it, and usually blow off some chunks of it. So we don't do that. We keep those charged particles in a magnetic field, so they just bounce around and don't ever touch anything.

It's less about thinking of it in the way we normally think about hot and cold, and more about thinking about it from a velocity point of view.

So what we should be imagining is extremely fast-moving particles. What is it—1 million miles per hour? Is that accurate?

That's the right kind of order for these systems.

Crazy. So you're looking for them to collide. First of all, to get back to the original question, are there some interesting insights or tricks you could share about the complexity of getting them to that high temperature quickly?

If temperature is velocity, that means they're moving quickly over a given amount of space. Speed is distance divided by time. If you have a machine of a certain size and it's moving very fast, that tells you the time that the particle is moving from place to place in that machine.

In fact, if it's 1 million miles per hour, these are on the order of 100 kilometers per second. You can flip that around and say you're moving at meters per microsecond—feet per millionth of a second. That fundamentally tells you—and we've known this—as soon as you say, "I want to do fusion," you know you need to react to the universe in microseconds and be able to understand the system at that speed.

If you get it hotter, it goes even faster, and you have to go faster. That's how we think about the systems. We measure everything in microseconds, not in seconds. When you do fusion, it's pretty wild. It's literally a flash: fusion happens, and it's over. You start it, do a lot of fusion, recover energy from it, and then turn it off before the human eye can really respond.

And there's a computer managing all this. How do you even program these kinds of systems to do the switching? Is there some innovation required there?

I'm continuously amazed by what the pioneers in fusion were able to do before computers existed, because they had to control things at this scale. Maybe it was pretty hard, which is why we've been able to take what they did and build on it. Now we use modern gigahertz-scale computing to do this.

Even when I started my career, we talked about megahertz processors. Megahertz is microseconds. That's great; you're kind of at the border of fast enough, but you can't do computation at that speed if all it can do is respond in one microsecond. Now gigahertz means I can do 1,000 operations in that one microsecond, so I can do more useful things.

This is way too fast for any human to respond to, so we use what's called programmable logic. We program sequences into the fusion system to be able to do this reversal. We preprogram it, run a sequence, and then fusion happens.

We use a variety of sequence-programming languages. Some of the fusion codes are actually still written in Fortran. More and more of it is being run in Python. We do some Java, and then, because of the speed of this, there's a lot of assembly-language programming. We go right to the assembly level of the programmable-logic FPGAs and program those.

To run one of these systems, we typically have a series of electrical switches that turn on this electrical current. Those are controlled via fiber optics because the wires are just too slow. With fiber optics, I can send photons at the speed of light, so those fiber optics can respond in nanoseconds. Then I trigger those fiber optics with programmable logic that we programmed in the hardware assembly language.

In terms of the sensors that are giving you information about the system—in terms of the diagnostics—at this time scale, what can you collect about the system such that you can respond at a similar time scale?

The diagnostic systems are really one of the keys to how we do this effectively, because you need to be able to tell the system, "We're going to trigger electrical current, and we're going to do it in a microsecond. We need to know if it's working right."

In one of these FRCs, or these pulsed magnetic systems, you won't have just one electrical switch. I've mentioned 100 mega-amps, 100 million amps of electrical current. Even the big transistors we use can only run at 30,000 amps, so you'll end up with tens of thousands. In fact, the systems we build now have tens of thousands of parallel electrical switches, all operating in harmony together.

You need to be able to build a system—and this is what we spend a lot of time on—to program, control, and then detect how those switches are operating, and do it all very fast. In a typical sequence, we preprogram it. The operators will preprogram a sequence, usually fed from a numerical simulation of how we expect the fusion system to perform.

We start with a set of calculations. We then pre-program all of these electrical switches to a certain sequence to be able to inject the fuel, reverse it, and then compress it up to fusion conditions. Then we trigger that, let it go, and measure fusion happening. But during that process, we have to be recording and measuring, in real time, all of the semiconductors and all of the switching in the system.

I'm not going to talk about measuring fusion diagnostics. That's a whole other thing, which we can talk about. This is just on the electrical control side. Some of the pioneering things we've been able to do are that, in real time, you're monitoring all of these switches. You're watching who is triggering correctly and who is not triggering correctly.

And if systems aren't working, you're shutting down the system because you want to make sure that all the sequences are operating correctly. Some of the key diagnostics are actually pretty amazing. Even early in my career, we didn't have a lot of fiber optics built into the system. Now it's absolutely essential. Every one of these electrical switches has fiber-optic signals going into it and fiber-optic signals coming out, so we understand how it's actually operating.

In real time, all of these systems are being monitored by more fiber optics. We call these Rogowski coils, but they're electromagnetic coils that are powered by the electrical current themselves. As the switches are conducting, they broadcast an optical signal that says, “Yes, I'm electrically conducting,” through fiber optics back to a central repository where we detect those signals. In real time, we're monitoring all of this so that we know these systems are behaving and operating at their optimal performance.

What's the role of numerical simulation in all of this? Ahead of time, how much numerical simulation are you doing to understand how the system is going to behave, how the different parameters all come together—the electrical system and how that all maps to the fusion that's actually generated?

Yeah. The operation of a fusion system is pretty fascinating because all of this happens on a time scale where human operators cannot really be involved. You have to have pre-programmed the majority—we call them shots. You're going to do a shot, and when you're operating them repetitively and running for long periods of time, you still have computers doing both the triggering and the measuring of how they're performing, in real time the whole time.

Typically, at least in our systems, we design a system with a combination of numerical simulation tools that we've developed based off of decades and decades of amazing government programs. National programs developed these numerical codes. We use a code called an MHD—magnetohydrodynamic—code. For the engineers out there who are used to CFD, computational fluid dynamics, this is very similar, where you take the same sets of equations and add electromagnetic equations on top of those. And so you get magnetohydrodynamics.

Are you simulating at the level of a particle? Are there some quantum mechanical aspects to this also? How low does it go?

Yeah, we have multiple codes at different levels, because one of the main computational challenges is that, amazingly, even given all that we have built, computers are still not fast enough to simulate everything for fusion systems. We have a number of codes that we use. One set we call fluid codes, where you treat the ions, the electrons, all these fusion particles as fluids, as gases, using the ideal gas law with electromagnetic forces.

In those, we can simulate not just the fusion fuel, which is important, but all of the electrical circuitry. We talked about capacitors and magnetic coils, the electrical current, and the switches. We actually simulate the full thing, starting literally with a SPICE model. That's more of the electrical engineering. We start with the SPICE model and use that to drive the plasma physics model, and that's one level of simulation.

We use that to do design work and also to try to understand how we think the machine will run. But then we go one level deeper, and we start thinking about particles. We think about the ions, treat the ions as particles, and look at the ion behavior. For that one, the computational resources are several orders of magnitude larger.

Luckily, a lot of the work in GPUs—the AI data center work—is directly applicable to those simulations. It's been able to speed up our work, which is pretty fascinating. That's a whole other tangent we can go down. Those hybrid codes, which we call particle-in-cell codes, now treat the ions as particles, and that lets us measure and simulate their behavior.

I mentioned the stability criteria, S-star over E, the tilt behavior. That behavior now requires these more advanced codes to be able to simulate, and those are more modern. We've only been able to apply them in practice for the last few years, which is pretty fascinating. The old stability rules were built off testing—empirical tests—whereas now we can simulate that, and we know why they work and how they work, and we can make some predictions about them. That's really fascinating, that we've been able to push those boundaries.

What are the different variables you're playing with? Are you still playing with topology? What are the different variables in play here?

Yeah. Each of the different simulations, we analyze and use them to design different parts of the machine. At the MHD level, where we have the SPICE and actually have the circuit model, our design team uses this to design the circuitry—which capacitor to use, which switch to use, how many cables to use, literally to that level, how big of a cable to use.

As we're doing power plant designs right now, those are the tools the team is using today, every day. Then you can go one level deeper and say, “Okay, let's use these more advanced computational tools about stability to say, ‘Okay, great, but I now know the circuitry. Let's look at the magnetic field topology. How do I design the magnet, the shape of the magnet exactly, and the timing of the magnet exactly? I have to trigger one magnet, and then the next magnet next to it, and then the next magnet next to it. How do I have that shape and that design?’”

That's where you're using those more advanced tools. Unfortunately, those are still too slow, so those simulations may take a day or two to run. An operator right now does a lot of simulations ahead of time, then collects data through their operations of the machines, making these field-reversed configurations and going through parameter sweeps. Then the simulation team goes back and looks at that data and compares it with simulations.

I'm really excited about some of the things we're seeing in artificial intelligence and reinforcement learning to be able to speed up that process. We're watching and starting to work on that now: Can we, rather than using it as we do today, where we do a simulation to design a machine or a test, run the test, and then over the next couple of days compare the testing with the simulation and use that to inform what we're going to run for the next set of tests, do it more in real time?

An operator could pull up what the AI or machine learning would have predicted it should have done, and then use that to understand what's happening in the actual plasmas, in the actual generators themselves.

All right. So there's a million questions there. First of all, how much understanding do we have about how many collisions happen? Can we get to fusion? How many collisions are there, and how does that map to the electricity? Maybe you can speak to the direct mapping to the electricity, which is one of the differences between this approach and the tokamak approach.

So how much fusion do you get out from these systems? That's really the right key question. We already talked about beta: B squared, the magnetic pressure, is equal to n k T, n being the density and T being temperature. Then we talked about fusion, where your goal for fusion is to get particles hot—high temperature—and get enough of them together—density.

Then you want to get them together long enough. We call that tau. So n, T, and tau—long enough that fusion happens, and a lot of fusion happens, more than any of the loss rates that are happening, nTτ. In beta, with B squared, you know already two of those parameters, n and T, are equal. That tells you right away the goal is to maximize magnetic field, absolutely maximize magnetic field.

Most folks in magnetic fusion, whether it's a tokamak, a theta pinch, or an FRC, are attempting to do that: maximize the magnetic field. We're all pushing toward that. What's really nice in pulsed systems is that we know how to do that.

In fact, researchers in pulsed magnetic fields have demonstrated over 100-tesla magnetic fields in pulsed magnets. That's much higher than you can get in a steady magnet, or what's been demonstrated so far.

Just a clarification question: Maximizing magnetic field is about the n and the T, the beta? So we're not talking about tau yet.

Not yet, but we need to, because that's really important. We can even talk a little further about how fusion scales. In fusion, the hotter you get the fuel, the more fusion you get. We know that by increasing the magnetic field—B squared is nT—you increase density and temperature together.

More density and more temperature mean more fusion, plus more temperature is even more fusion. What we see is that, in these types of systems, there's a very clear scaling of magnetic field to the 3.75 power, or even, in a lot of demonstrations, 3.77.

That specific scaling is a very strong scaling of fusion power output and fusion reactions. That tells you that you want to go to as high a magnetic field as you can. Pulsed systems are really powerful. Pulsed systems have shown that when you use pulsed magnetic fields compared to a steady magnetic field, researchers have achieved over 100-tesla magnetic fields. In a steady system, people have achieved 20, maybe high-20-tesla systems.

If it’s B to the 3.77 power, you can already see massive fusion power outputs by using a pulsed system. But then I said “pulsed,” and pulsed already implies a shorter tau.

That is the name of the game in the fusion field. In inertial fusion, you have a nanosecond tau. It’s very short, but then you have very high pressure. They don’t have magnetic fields, but they have very high pressure. In stellarators and tokamaks, the goal is a very long tau, but you’ll have much lower density, and you can’t really go too much higher in temperature. You have much lower density.

Where we live, in pulsed magnetic or magneto-inertial fusion, is in the middle: extremely high magnetic fields, increasing pressure as much as you can, and then keeping them around long enough. That gets to the tau. That gets to the energy-confinement lifetime, and it also gets to stability. This is what the field-reversed configuration has shown: We can build these plasmas, and they can last for hundreds or thousands of times longer than basic theory has shown. Now you can have long enough lifetimes.

What that means is that in a practical fusion system, the lifetimes of these high-beta pulsed systems are between 100 microseconds and a few milliseconds—thousandths of a second. You hold onto it for a few thousandths of a second, you do fusion, and then you exhaust it. The whole process starts with a magnetic field that fills the full chamber. You then inject fusion fuel and ionize it, superheating it to a nice, hot 1 million degrees—hot enough that you have charged particles, that you have plasmas.

You can then start increasing the magnetic field. You form a field-reversed configuration and then rapidly increase the magnetic field further, from 1 to 5 to 10 to 20 Tesla, to even higher magnetic fields. As you do that, the plasma heats. You compress it, increasing the field and pressure. Fusion is now happening. New charged particles are being born inside this system with a tremendous amount of heat and energy, but that energy is in charged particles.

This is where the beta really works to your advantage. Just like magnetic pressure on the outside, n k T compresses the fuel, increasing pressure and temperature. When the pressure and temperature of the plasma increase, n k T increases. It pushes back on the magnetic field, increasing the magnetic field on the outside of the plasma. What that does is create an electromagnetic current, like current running in a wire, and that pushes current back into the wire. The plasma itself now pushes back on the magnetic field, pushing electrical current out of the system and recharging the capacitors where we started this whole process.

All in a self-organizing way. I think it’s good to clarify how fusion usually generates energy, where this intermediate step of heating up water, then using the steam, is the thing that leads to electricity. The FRC method that you use leads directly to electricity. I was wondering if you could describe the difference between those two.

I like the analogy of the match and the campfire, and I hear that a lot in fusion. What steady fusion—think a stellarator or a tokamak—is attempting to do is take a little bit of fuel, that match, add heat to ignite that match, and then put it with enough fuel, in the right conditions, and hold onto it for a long time so that it grows into a campfire. Even if they do a good job, it becomes a bonfire.

It’s creating a tremendous amount of energy in that steady system: burning fuel in the same place, generating some ash, and generating a lot of heat in that reaction. In a traditional tokamak or stellarator, that’s a lot of what you’re doing. You’re holding onto the heat as much as possible to keep that reaction going.

The optimal fuel is called deuterium and tritium. Deuterium is a heavy isotope of hydrogen where you have an extra neutron, and tritium is a very rare form of hydrogen that’s unstable. It’s so rare that it’s hard to get. It has 2 neutrons and a proton. When you fuse those together at very high temperatures and high enough densities, they make helium, which is a charged particle. It stays inside the campfire, inside the tokamak, continuing to heat it and stoke the flames. It also makes a neutron, which leaves the system because it’s uncharged. It has no charge, and in that system, that’s actually ideal.

In a campfire, you have this reaction going, and you want to get the energy out of it. You want to use it, and you don’t want to just burn up all the fuel and do nothing. That’s not really valuable. What’s really valuable is to stand next to the campfire and get the heat, get what comes off of it. In a traditional fusion system, you use that to boil water, to heat the water, and then, at 30% to 35% efficiency, convert that through a steam turbine into a cooling tower, cool off the fluid, and extract electricity.

We know steam turbines. Coal plants do this. Nuclear fission reactors do this. We know how to do that, and that’s the traditional way of doing it. But I think there are other ways to do it with a pulsed magnetic system.

There’s one more thing you get to do because you have this high beta, where there’s an electric field and an electromagnetic force that’s now compressing the fusion fuel. It’s increasing in temperature. It’s getting hotter, increasing in density, and fusion is happening. New fusion particles are being born, and those particles are not just stoking the flame. They’re not just holding onto the campfire like in the tokamak. They’re doing another thing, which is really powerful: They’re pushing back on the magnetic field. They’re applying a pressure, and that pressure induces a current. We can extract that electrical current.

That takes you in another direction, so your analogy of the campfire now breaks down. The campfire is expanding. It’s pushing back on something. Now it’s the analogy of the piston engine. As you move from the match to the campfire to pistons, in a piston engine, you use the pressure and motion of the piston to do something useful. That’s to turn a crankshaft and run wheels, or maybe to turn a crankshaft and run a generator and make electricity.

You can do it at pretty high efficiency using that method. We use the expansion of the magnetic field to extract that electricity, and we believe you can do it at much, much higher efficiencies. In fact, there have been theoretical papers that show not 30% to 35% efficiency, like a steam turbine can do, but 80% to 85% efficiency, extracting much more of the energy of the fuel in that process.

Can you take a tiny tangent on the word “efficiency”? You said 30%, so it’s inefficient. That efficiency measure is how much of the energy is actually converted to electricity?

That measure is how much of the thermal energy that gets outside of the system is then converted into electricity, which is the thing we care about. We’re not in this to make fusion. We’re in this to make electricity. We’re using fusion to make electricity, and from my point of view, that should be the focus: How do we get to that? That’s the efficiency of the thermal energy that makes it out to electricity.

What it is not a measure of is how much energy you put into the system and what happens to that. You started this campfire with a blowtorch. What about all that blowtorch energy? What are you getting for that?

I think high beta is one more side benefit that it turns out is actually maybe the tail that wags the dog. Not only do you, at high efficiency, get out any of the new fusion energy—which is great, because that’s what you want: to make electricity from fusion—but you also get to recover all of that magnetic energy you put back into it. That’s the really powerful one.

Folks have demonstrated over 95% efficiency: You can put electricity into fusion and then get that electricity back out at 95% efficiency, plus a very high efficiency—maybe 80%, maybe higher—of all the fusion-product electricity, too. Now you’re making a tremendous amount of electricity in one of these systems, and that has all kinds of performance and engineering benefits that are really powerful.

It also pushes you toward other fuels. We talked about how deuterium and tritium fuels make this neutron, which leaves the system to boil water and run steam turbines, but it doesn’t push back on the magnetic field. In one of these high-beta systems, it’s actually not a great fuel at all. The other fuels that are out there are even more interesting, and one of the candidate fuels that’s really interesting is called deuterium and helium-3.

We talked about deuterium, heavy hydrogen. Helium-3’s nucleus is also called a helion. That’s why we named the company Helion. It’s light helium, which is... In normal helium, which is what you find in a balloon, there are 2 protons and 2 neutrons.

It's very stable and found commonly. Helium-3 is also stable, but it's not found commonly. Fortunately, it's lightweight, so it leaves. It literally leaves the atmosphere and goes into space. So we don't have a lot of it here on Earth, and you have to make it, or you have to go into space. There's a whole other question about where you get it: do you get it from the Moon? Jupiter has, it turns out, massive amounts of helium-3.

But when you take deuterium and helium-3 and fuse those together, you also get that helium particle, that alpha particle, as we call it in fusion. But instead of the neutron, you get a proton, and that proton is a charged particle. It's a hydrogen nucleus. That proton is now trapped in the magnetic field and pushes back, and you can extract that electricity.

Now, there are some prices to be paid for this helium-3 fuel. But for a high-beta system, like a pulsed magnetic fusion system, that's really the ideal fuel.

When you say “prices,” what are the prices? What shape do the prices take?

All kinds of shapes: physics, engineering, technical, and business costs. So, let's dive in.

From the fusion physics point of view, we talked about 100 million degrees. That's the temperature at which deuterium and tritium fusion works really well. That's the temperature that traditional fusion folks have really focused on getting to. That's the threshold. When you get to 100 million degrees, you're at the operating point of fusion, and you know it works, colloquially anyway.

Helium-3 requires higher temperatures. That's not enough. Fusion happens for deuterium and helium-3 at 100 million degrees, but it's not its optimal temperature. In fact, in a high-beta system, the optimal temperature is higher: 200, even sometimes 300 million degrees. So you have to get to even higher temperatures. Temperature is hard, and you have to push to even higher temperatures than you had before. That's one of the downsides.

The other downside can be that, as you get to those higher temperatures, we talked about B² = nT. B² is density times temperature. For a given magnetic field, density and temperature are now inverse. So as I increase temperature, density decreases. Now you have an issue: you may have fewer particles to do fusion, which means your fusion system has to get bigger than it was before.

So for the same reaction rates, a helium-3 system compared to deuterium-tritium has to operate at a higher temperature and be bigger. However, the flip side is that if you can now recover energy at 80-some percent—at 3 times the energy efficiency, 80-some percent versus 30-some percent—and recover all your input energy, then it's actually about the same size.

Because they have the same electricity output, not energy. It's not energy that we're worried about; it's electricity we're worried about. With the same electricity output, you can actually build systems of similar size and similar energy. Only now, they're at this much higher efficiency.

Got it. Can you say more about size? What are we talking about here? Why is size an important constraint?

That gets to one of the other prices. That gets to money. Our goal is to build clean, low-cost electricity and get it out in the world, but that means it needs to be low-cost. That's fundamental. If it's really expensive, no one's going to buy it. While it can be clean, it's not going to be deployed. So that always has to be a part of what the promise of fusion is: that it can be low-cost.

How do we know how much fusion systems cost? That's a really great question. A lot of it comes down to fundamental size: you have to just build things. There's some really first-principles cost engineering you can do around power plants. Fundamentally, what do they cost? How much concrete went into it? Fundamentally, how big is it?

If you're doing a good job of manufacturing, your goal is to manufacture a product for as low a cost as you can so you can sell it for as low a price as you can. It asymptotes to the material cost, because you never get cheaper than that.

Ah. So this, in some sense, some sort of first-principles sense, is how much concrete—

How—how—

—goes into building the power plant.

How much concrete, how much steel, how much copper and aluminum. Different materials cost different amounts, but at the end of the day, the cheapest function is the least amount of materials.

Wow. Okay.

We think a lot about that and how we can make these systems smaller so they can be developed at lower cost. Now, there's a flip side: you still need to produce electricity. If you make them really small and they don't produce electricity, and there is some minimum size to fusion, that's really important.

Fusion scientists and engineers don't see you ever having a fusion generator on the back of your DeLorean, for instance. The physics doesn't let that one happen, at least according to the physics as we've understood it for the last 100 or 200 years.

There are a lot of really interesting business questions here, because you're basically at the cutting edge of science, technology, physics, and engineering, trying to innovate into the future rapidly. How do you do that? The R&D here, the research alone, is a lot of money. What can you say about that? How do you be bold and fearless in pushing this technology into the future when so much is unknown and it costs so much to do the research?

I think about this in a couple of ways. One, the need. We look to the world and we know the world needs clean, low-cost, safe electricity. Just to meet our needs today, without even talking about the needs of tomorrow or the needs of AI or any of the growth that's probably coming, we need that electricity today.

Fundamental to that is that it has to be a product that people will buy. It has to be a generator that's making that electricity at low cost, and it's got to be soon. A lot of what I think about is how we do those two things together.

A lot of that is scale, and a lot of that is thinking about—not big scale. In fact, it's the opposite of that. It's small scale. It's how you build a product that's mass-producible, that you can build quickly and learn quickly. What I've found in my career is that they're actually the same thing: the faster you can build a thing, the faster you can learn if that thing works, and the faster you can iterate on it and build the next thing.

What I have spent my career building is teams of humans and a company that are builders, that can build high-technology things quickly. If you want to do R&D, you don't want large-scale, multinational, complex, huge systems. You want to take the smallest thing you can build that accomplishes the mission. In fusion, there is a minimum size, but you want to accomplish the mission, then build it quickly and build whole teams around building it quickly. You incentivize folks to move quickly, iterate, and learn.

The irony, I think, of one of the things that I've discovered is that by focusing on manufacturing, by focusing on low-cost, very rapid manufacturing, you actually get to do science faster. At the beginning of my career, I would never have guessed that. I would have thought the way to do science is to make a giant demonstration particle accelerator somewhere, that making a large, complex science experiment is the best way to do science.

What I've found is that actually, small, iterative—just building as fast as possible—gets you there faster, because you can learn, you can build, and you can iterate. You can solve the problems, and then you can learn the fundamental physics, learn the scaling, learn the FRC and the B to the 3.77 power, and learn those things way sooner than if you had just started on one mega-project and then waited decades to get to the answer.

There's a profound truth in that, something about the constraints of pushing for the simple, the low-cost, and the manufacturable. That pushes everything—the science, the innovation. In fact, you should maybe explain that you're, I believe, on the seventh prototype. This is insane. The rate of innovation here is insane.

Can you speak to all the different prototypes you went through and what it took to iterate rapidly? It might be really interesting for people to hear what you can say about the teams required to make that happen. What kind of people are required to make that happen at that fast rate? We're not talking about software here. We're talking about everything, the full stack, all the way down to the physics at 100 million degrees, at speeds of 1 million miles per hour. It's insane.

Anyway, how do you iterate the prototypes, and what kind of teams make it happen?

At Helion, we've built 7 systems. The first 6 were a series of prototypes that we built end-to-end, focused on scaling the process of making these field-reversed configurations, compressing them to thermonuclear fusion conditions, and demonstrating that you can do fusion, then increasing the scale, temperature, and energy.

The very first ones were named after beer. Actually, the most successful was the Inductive Plasmoid Accelerator, or IPA. It was the first system that showed the team could make these FRCs, hold on to them, and understand some of the stability and heating criteria.

Then we started increasing the field. Now, okay, great, we can hold on to one of these FRCs. We know how long and how to make them, but now can we squeeze them and start doing fusion—increasing the pressure and temperature?

What we noticed is that, machine after machine, we always used Starbucks. We were in Redmond, Washington, at the time, and Starbucks cups were sitting on top of the machine as a way to show the scale. They were too small to have a human really in the picture all the time, so the Starbucks cup was enough. Then we switched to Tall, Grande, Venti. The biggest one, Trenta, was the biggest system that came online in 2020.

That was a system that showed 100 million degrees and was the first system that did deuterium–helium-3 fusion. In fact, as far as we know, it was the only bulk deuterium–helium-3 fusion that had been done, and it also showed 100-million-degree fusion temperatures from an FRC.

Throughout that time, the earliest work was government-funded through government grants, SBIRs, and other types of government grants. Actually, the team involved me and the rest of the founding team, and we were really good at winning government programs and doing fundamental science while moving very quickly. There are a lot of ways to think about how to iterate and how to build quickly.

I want to talk about the teams first, and then we can talk about some of the technologies we use to do that. A lot of it is thinking about this: if your goal is to get the product—electricity—out to the world as soon as possible, then you should be looking at everything you do through that lens.

That means thinking about the materials you choose. At every turn, you want to choose commonly available materials. If you have to wait for the supply chain for an ultra-rare material, it’s going to take you a lot more time. Do everything you can to engineer a system that uses simple aluminum alloys and simple copper alloys.

If you have to use tungsten, and maybe you have to use tungsten in some of your systems, which is a hard-to-find alloy, make sure you’re using commonly available thicknesses of tungsten sheet. Those kinds of engineering analyses and thought processes happen at every step.

That’s how we built these systems, from IPA to Venti up to Trenta. We were always looking at, “How do we build systems that are easy to build and mass-produce?” The other thing that I don’t know I would have predicted early in my career is that by making 100 of a thing, you can actually make it faster than if you make 1 of a thing.

That’s because when you look at our fusion systems, we’ve talked about these big magnets. You could build 1 giant, complex, hard-to-make magnet that’s heavy, that you have to move around with a crane, and that requires very complex machining by ultra-rare CNCs. Or you could make that out of a composite of 100 smaller magnets.

Each of those magnets can now be made on a simple machine. Each of them can be picked up by a human; they’re light enough. They can be made, manufactured, and mass-produced. That’s what we did, and that was our whole design philosophy on these machines: at every turn, how do we go faster?

A classic example that I still push the team on to this day is thinking about how you move fast: eBay. We buy—and I don’t know that I’ve ever said this publicly—we spend a lot of time on eBay.

Oh boy, here we go. This is great.

You’ve got to move. Here’s an example. We use a vacuum pump because in these systems, you’ve got to pull out all the air. We use a vacuum pump called a turbomolecular vacuum pump.

This is a commodity. It’s used in a variety of particle accelerators and scientific applications. There are many of them. They’re robust, they last a long time, and they also have a very small supply chain.

If you want to buy a brand-new turbomolecular pump, you can, and you might wait 9 months for the manufacturer to make one for you and deliver it. But I can go today and get the same model that was made 10 years ago on eBay, right now.

However, it might not work. You don’t know how well it works or how clean it is, or any of those things. What we do is, you don’t go to eBay to save money—although it is cheaper. There are turbopumps sitting on eBay right now. Bring those in-house and test them.

Maybe only 1 of them meets the specifications you need, but guess what? You just got a pump in 2 weeks instead of 9 months. You got it, it’s in the door, it’s operational, it’s running, and you’re moving.

See, I love this. I love that kind of stuff. One of the only people I’ve really seen do that is Elon. He put together that cluster in Memphis in a matter of weeks, which is nothing like that has ever been done before. This eBay way is really the kind of thing that’s required to make that happen, as you shortcut the supply chain.

And everywhere you can, you still have to deliver the working product, right?

Right.

You cannot sacrifice the quality. But do you really need the shiny, brand-new one when the used one is going to do the job? We think about that across the board.

Do we take the best plasma diagnostic, the most sophisticated plasma diagnostic in the world, with an accuracy within 3%, when it’s going to take me 3 years and maybe a few million dollars to build? Or do I take a technology from 10 years ago that’s 5% accurate, that’s good enough, and that I can build in a month?

The answer for us at Helion, and for the team that we’ve put together, is that scrappy, “I just want to solve the problem. I don’t necessarily need the best solution, but let’s make it happen.” That’s something that we routinely do.

I think sometimes I have challenges with my academic colleagues on this, because we have a difference of opinion. That 3% is way better than 5%, so shouldn’t you do that? You’ll know your data better. But 5% is good enough.

Now, 50% would not be good enough, and so that technology wouldn’t have been applicable. Finding that middle ground is a hard thing to do, while never compromising on quality and safety. It has to work, and it has to be safe. But can you still go fast?

But in general, it’s about having a culture of pushing the rate of iterations here.

Mm-hmm. And building the team that wants to go build things. Everyone at Helion—or at least the vast majority of people at Helion—we hire engineers, scientists, technicians, and machinists who are hands-on builders.

The company at Helion is very weird for a fusion company. Today, we are 50% technicians, not scientists. We have a ton of scientists, because the science is critically important too, but they’re supported by a huge manufacturing company. Our goal is to build as fast as possible.

Some of the other things we try to do are vertically integrate. To your point on Elon Musk, this is one of the things he’s focused on at his companies: how do you bring inside the critical things that are going to drive timelines—the things you can’t just buy as a commodity product and get here soon—and make sure that you can build those quickly?

We’ve now done a number of key vertically integrated manufacturing lines at Helion. I think we may be the only fusion company with a conveyor belt. Actually, our second one just came online, where we literally have our production line manufacturing power supplies at Helion so that we can move at maximum velocity, rather than finding an external consultant or an external supplier to do those things.

Well, I love it. Builder-first company, and you’re also thinking about manufacturing throughout all of this. I’m looking at the photo of Trenta. It’s beautiful.

You can actually see 1 perfect example of what I’m talking about in this picture. On the end is a green structure made of green fiberglass. This is called G10. Ironically, one of the main structural elements we use is this G10 fiberglass material.

It’s the same thing that’s in PCB boards. It’s the same substrate that’s in every circuit board. We know it’s strong and good with electricity, except we get big pieces of it and machine them.

Even at the end, you can see the bolts halfway through. There are 9 bolts in the middle there. The standard piece of G10 was not big enough to fit the end of the machine, so we could have had 1 custom manufacturer manufacture a brand-new piece of a custom size, build a new mold and a new machine.

It would have taken—I don’t remember now, but usually these are about 6 to 12 months. Or I could go to a supplier and get something off the shelf, have that delivered in a week, and machine it with all the bolts in between.

In-house, we have a G10 machine shop that can machine the bolt holes to actually bolt those pieces together. That took extra engineering and having really clever and brilliant mechanical and structural engineers figure out how to do that while still meeting the needs of the fusion system.

Those are the kinds of teams we try to build at Helion: folks who want to really get their hands dirty, get hands-on, build things, and move quickly. Everywhere you can, without sacrificing quality or safety, take shortcuts. That’s the name of the game. We’ve got to get fusion online as soon as possible.

Yeah, this is really exciting and inspiring. I have to ask, then: what timeline do you think—for the first working nuclear fusion power plant out there? When do you think?

Yeah, so what we’ve been able to do is rapidly build and, every few years, bring a new fusion system online.

In 2023, we signed a deal with Microsoft to build a power plant for one of their data centers. This is a power plant that is plugged into the grid, generating electricity from fusion, with a very tough, ambitious timeline of 2028 for the first electrons from that power plant.

And that power plant will be powering a data center.

That power plant will be powering the grid that the data center is plugged into. We can get into the details of how the power grid works, but yes, Microsoft will be buying the power from that power plant.

Props to Microsoft for creating a hard deadline. I love it.

They are. It is daily that we think about that deadline. We had been working with them on and off through all of those machines, through Grande, Venti, and Trenta. They had seen us build, hit milestones, show that we can do fusion, scale up by orders of magnitude, and then access these advanced fusion fuels. They had seen all of those things and seen the manufacturing we built.

We’re already building the manufacturing to support that power plant. We’re doing that today. We started 2 years ago on the work around siting and interconnects: How do you plug fusion in? What does it look like? How do you site it? What are the environmental consequences? Who’s going to regulate it? All of those things.

We’ve spent a lot of time already, and we’re on our way. It’s going to be hard. No joke about it. This is tough, and it’s something that I think about every day.

I’m sure you’ve had a bunch of people, probably still, tell you that this is a pipe dream, that this is impossible. Are there days that you and the team think that this is indeed impossible? Then you wake up the next day and you’re like, “All right, we’re going to do it anyway”?

That’s the thought process. That’s the mentality: We’re going to do it anyway. Let’s go do it. The world needs it. There’s no physics reason this can’t be done. Now it’s a question of how fast can you build it, and can you engineer it to be as efficient as it needs to be? Those are engineering and manufacturing challenges that are ridiculously hard, so do not undersell that. But that’s the goal, and that’s what we get up every day thinking about.

This is something I was actually just thinking about and talking with some of my team about in the last few days. We certainly have people who say, “No, this can never be done.” We had that before. We had that at the very beginning, when I wanted to merge these plasmas together, and folks said, “Nope, that can never happen.” We went off and did it.

Then there was, “You can’t compress an FRC because it’s unstable.” In fact, I still hear that: “FRCs are unstable.” I say, “Yes, I know. Now let me introduce you to S* over E, and 20 years of studies on what we know about that and how we can combat that.” We’ve been able to show, through lots of skepticism, that we can still build and iterate.

There are things I don’t know. Let’s just be totally honest. As we’re going to build these things, we’re going to find new hard problems. If we’re not doing our job, if we’re not discovering new hard problems, we probably didn’t push hard enough. We probably didn’t push fast enough. I think that’s really critical: that we build the team and do the hiring to make sure that everybody is doing their job.

That doesn’t mean it’s not a hard challenge to keep folks motivated. Helion is now over 500 people, but when we built Trenta, we were 50 people.

Okay.

Now there are over 300 people working at Helion who didn’t see us build a system from a computer model, bring it online, and do fusion with it. But even already for Polaris, there are lots of people who started for our seventh-generation system. When we were running Trenta and doing fusion, they were able to see that, see the measurements, and know we were doing fusion. Yet this next machine was just a simulation.

Seeing that get built, seeing that come together, it’s awe-inspiring for folks. I’ll tell you, the first time that it comes online and flashes pink and you see that fusion glow, it’s awe-inspiring. It’s awe-inspiring.

I love that.

I’ve—

The fusion glow, yeah.

Everybody changes their Windows desktop backgrounds to the fusion background, the plasma glow.

So how can you actually see it?

To get access to it, we have windows. We have small windows all the way around that we look into with cameras, spectroscopy, lasers, and other kinds of scientific diagnostics that we use to measure. You see the light emission through that.

But it’s also very bright. The actual vacuum vessels themselves that we use are ceramic. There are some versions made of silicon and oxygen, typically quartz, but there are also some other sintered materials. It’s so bright that the light can shine through those materials.

What you see is not the light of fusion. When fusion is happening, thermonuclear fusion is so hot that the light is in the X-ray spectrum, and the human eye can’t see that. But your ice-cold, one-million-degree plasma, when you’re just getting started, is emitting photons and light in a range that humans can see. You see that bright purple, fuchsia color.

If you’re doing actual cameras, would this be extremely high-speed cameras, that kind of thing?

We have high-speed ones and low-speed ones. The traditional SLR cameras, which are the ones that represent the right color, catch only the integrated light, the flash. They can’t see the plasma forming, accelerating, or compressing. They just see all of it integrated into one bright flash.

The high-speed cameras can see that. We can use them to actually measure it. In fact, we put special filters on them to measure different wavelengths of light, so we can tell: Is it the hydrogen? Is it the helium? Is it the helium-3? Who’s emitting the light? When are they emitting? What particles are emitting the light, and when?

By using those advanced diagnostics, we can now take movies of it, though it’s not as great as just seeing that flash.

It’s beautiful, right, that human beings are able to create something like that. It’s truly beautiful. Just out of curiosity, are there some interesting intricacies connecting a nuclear fusion power plant to the power grid? Are there constraints related to the old-school nature of the power grid in the United States? How do you get from the nuclear fusion power plant to a computer with some GPUs? How do we make that connection, or is that a trivial thing?

None of this is trivial. But there are, I think, simple ways, and there are some really interesting engineering ways to do this.

From the fundamental basics, as we’re doing fusion, we push back on the magnetic field. We recharge the capacitors that the electricity started from. That electricity then sits on a capacitor at high-voltage DC, which is steady. At that point, it’s reasonably easy to make 60-hertz power, to make traditional AC power. It’s the same way you can take electricity in a battery, use an inverter, and invert that to AC power. Large-scale grid inverters, we know how to do pretty well.

One of the unique things about a pulsed version of this is that, because it’s pulsed at a repetition rate between 1 and 10 times a second, we can adjust the power output. As the grid needs more power, we can dial it up and down. We’ve been able to demonstrate that with our fusion systems.

With the smaller plasma systems, we’ve gone from zero, from off, all the way to 100 times a second and shown that we can do 100-hertz operation. In fact, that system ran for over 1 billion operations. It just ran steadily all day long.

So each individual pulse is independent in some sense?

Each individual pulse is different. You put in your fuel, do fusion, exhaust it through those pumps from eBay, and then you have the power output and electricity output.

Wow.

There are probably some more clever ways to do this. When we founded Helion, the goal was to build low-cost baseload electricity. What we started to see, working with Microsoft and others, is that data centers are going to be one of the biggest power needs in the future. We know that’s coming.

What’s really unique is that power in this form is direct recovery. It’s not the steam-turbine part; it’s direct electricity, which is already DC and steady, which is what computers really want anyway. Are there really unique ways to take the DC power sitting on this capacitor and, rather than going AC to the grid and having all these transmission losses, just go direct DC to the data center? Can you plug right in?

That’s what some of my team is looking at now: Can you do that direct DC conversion at super-high efficiencies and run those GPUs directly? That would be really powerful if we could figure out how to do it. Those are some of the ways that fusion and data centers might uniquely couple together.

There’s a whole cooling part to it, too. Most of my cooling is cooling semiconductors and cooling power switching, just like a data center. There are a lot of interesting engineering ways that we can bring those two together.

So, a deeper integration between the power plant and the thing that it’s powering. It does seem like, quite possibly, the future will need a lot of energy for compute, for AI-related applications. If you look out into the future—10, 20, or 50 years from now—do you see nuclear fusion as something that powers these gigantic data centers with millions of GPUs? Basically, the surface of the Earth covered in compute and nuclear fusion power plants?

Maybe that’s 100 years out.

So when I talk to AI experts, they talk pretty routinely about the power needs for AI. In fact, in the same way that, in manufacturing, the cost of any one thing asymptotes to the raw material, for AI, the cost of computation asymptotes to the cost of power—to the cost of electricity. Even more, that electricity is concentrated. It’s in that AI data center, that brain where all the power is, and you really want a lot of high-energy density.

So it seems like, taking those two facts, there’s a really nice match between fusion, which is baseload, high-energy-density, and can be sited most places, and a data center, which is going to have high energy requirements in a local location, and large amounts of it. There have been predictions recently from energy institutes that suggest we will have growth that, rather than 2% growth per year in electricity, may be 4% or 6% growth in electricity due to data center use. I think that is probably wildly underestimating where we’re moving.

Oh, man.

And so the idea that AI can grow human cognition and our ability to solve problems—we can’t let it be limited by power. I’m going to push as hard as I can so that that’s not the limit.

Do you ever think about 2050 or something like that? I know you’re focused on a few years out, just getting a fusion power plant working. But do you ever think about the even longer-term future? By what year do you think there’ll be over 1,000 nuclear fusion power plants?

So I tell the team that if we demonstrate fusion one time and that’s it, then we failed. But that’s not enough. The universe is powered by fusion. Humans need to be harnessing this, and can harness this, for our society, for the good of society, for the good of technology.

That’s something that we push toward. In fact, it’s baked into how we design these machines. Coils are mass-produced. Capacitors are mass-produced, and we make them all. All across the board, we’re thinking not about what the next system is going to be, but about making sure we’re building the manufacturing and the infrastructure to build all those systems.

So we had a call from the White House a number of years ago for the Bold Decadal Study in Fusion. It was Helion and a variety of other companies from the fusion industry. It’s pretty awesome to be able to say there’s a fusion industry now. It’s not just a one-off thing, or a fusion experiment, or somebody with a prototype. There’s an industry. Helion has competitors. That’s great.

I’ve never heard anyone so excited to have competitors, but yes, that’s a serious thing. That’s a real possibility.

The goal was not just to demonstrate fusion in the next decade, but to meaningfully deploy it and start to answer this question: We have 4,000 gigawatts of installed fossil fuel capacity. How do we start replacing that with fusion in a meaningful way?

And how do we get to not just making a generator every few years? We want a factory, a gigafactory, with these fusion generators rolling off the line—one a month, one a week, one a day. That’s the kind of plan that I task my supply chain team with. How do you do this? How do we actually go build this?

How do we go build a gigafactory so we can have 50-megawatt generators coming off the line, being deployed on a truck, and then driving off the factory floor every day? It’s a tough challenge. I see what others have been able to do in rockets and electric vehicles, turning around huge factories. We know this can be done, and so for fusion, the call is there, and the market is there too. If you can get electricity generators cheap enough, then it’s worth doing.

Yeah. All of this is really exciting and inspiring, what you’re doing. Obviously, the world needs it. The more cheap energy we have of this kind that we described—clean and not constrained to geographic locations—the more it alleviates geopolitical tension. Second of all, it enables a lot of the technological breakthroughs on the AI side, on all the different things that we use compute for. It’s really, really exciting. So, yeah, I hope there are millions of them in the coming decades.

If we can get to that, if we can get to making a generator a day, you’re no longer talking about hundreds a year, and you’re deploying them. Deploying them is also hard at this scale. How do you go and deploy power plants and generators at this scale and do it quickly?

Interestingly, data centers are a nicer challenge in that way, because we wouldn’t build one 50-megawatt system and have to go build a site for it. We’d build a site and put 100 of them on that site and have large amounts of power for that large data center. In some ways, that’s actually a chicken-and-egg problem: How do you go deploy hundreds or thousands of fusion generators?

Data centers are an interesting application where, very immediately, you need a lot of power in a very small area. You can go do that. What does that mean? It means I’m going to need more than 2 conveyor belts, that’s for sure.

Yeah. Well, manufacturing is really hard. But like you said, the fascinating thing is that, as you’re doing it, you figure out all the other things—the science and the physics and everything. Innovation is accelerated when you have to manufacture at scale. It’s actually fascinating to watch. You see that in the space industry as well.

When do we humans get to Kardashev Type I civilization status? And when do we get to Kardashev Type II?

The Kardashev scale: a Kardashev Type I civilization is when humans are either catching or generating as much power as what’s incident on Earth from the Sun. Type II is the next big one, where you’re catching as much energy from all the way around the Sun—massive amounts of energy. A lot of times, people talk about it as incident, as in you had solar panels the size of the entire planet blocking all of the Sun.

But I think, really, you should be thinking about it as: What can we generate? What can we make here on Earth? What we know is that we’re only a fraction right now of Kardashev Type I, and we’ve got some work to do. There aren’t a lot of technologies that can get there, just from the point of view of the fuel. But if, as some research says, there’s 100 million to 1 billion years of fusion fuel on Earth, we have room to go, and that’s at today’s use. At 100 times today’s use, we still have tons of fuel. Let’s go do it.

And what does that unlock? What does it unlock to have power 100 times the output that we have here on Earth right now? I think that’s pretty transformational. Do we have those huge AI data centers? Do we have brains that can now think at rapid speeds and innovate? I think that’s a pretty powerful future.

Yeah, I can just imagine a giant AI brain and rockets constantly shipping more and more humans out into space, colonizing space, and expanding out into the universe. Obviously, there’s a lot to be concerned about. Technology in itself is always a double-edged sword.

There’s always a concern that we humans, with the power we create, will also destroy ourselves in obvious ways and less obvious ways. I’ve been spending a lot of time in nature, and you become distinctly aware that there’s something truly special about the simplicity and balance achieved by nature. In some sense, we disturb that balance by creating sophisticated technologies. But in another sense, we’re building something in the spirit of nature that’s more and more beautiful and allows us humans to flourish in a richer and richer way. So, a double-edged sword.

I think a lot about what vast amounts of low-cost energy, low-cost electricity enable, and how that works with nature. If you have power—and this is one of the reasons we love fusion—it’s energy-dense. A 50-megawatt facility, we believe, fits in a 27,000-square-foot building, on the order of an acre, for 50 megawatts. Compare that to solar, which would be 2,000 acres, at least in Seattle.

What you can do there is transformational. A lot of folks talk about desalination and clean water, so that we can be in places where there’s not a lot of water, and those things. I actually think about food, ironically: How much of the Earth’s surface that used to be nature is now farmland? We need it. We’re going to grow food because humans need to eat, and that’s really critical, but it’s about 5 feet tall all over the Earth.

Why can’t you do it at 500 feet? Why can’t you build a building where you’re actually growing plants at high food densities, so that we can eat and we can exist and coexist in a way that’s energy-dense and rich?

You mentioned actually going to space. How do we go to space now? We take methane fuels or hydrogen fuels, burn them, and launch a rocket. There are all kinds of cool beam-powered rocket technologies that I looked at early in my career, where you can beam microwaves, and so you have a microwave craft that doesn’t have to burn any fuel.

If you have really dense, really good power on Earth, you can beam it to that microwave craft. It can now use electricity as its rocket fuel. There are some really powerful, interesting things you can do. It gets even more enabling in deep space, but even just launching from Earth.

I think it opens up things we don’t really even think about, but it’s just been theorized: “Wow, if I had massive amounts of power in a small place that is low-cost, this is what it could do.” But I’m excited by what it can unlock that we can think about now, and even more by what we can’t think about or don’t know yet.

Since you mentioned propulsion, is there some interesting possible use of nuclear fusion in propulsion, whether it's getting off Earth or going into deep space?

That's how I got into fusion: thinking about that intersection of energy and space travel. When you're in the solar system, around Earth's orbit, collecting the Sun's energy makes a lot of sense. It's there. It's free. When you're in space, you get a lot more of it because the atmosphere isn't blocking it. That's why spacecraft run on solar panels.

But if you want to go further out, the Sun's irradiance falls off as r squared, radius squared. It's a long way out there. It doesn't take very long before there's not a lot of energy from the Sun. You have to bring it with you, and in space, mass is expensive. Mass is hard. That's the rocket equation. Being able to bring high-energy-density fuel is really exciting, and that's what fusion enables.

But here's one of the challenges: If you make electricity from fusion using a steam cycle, you now need something cool. You get hot water, and you have to be able to cool it. In space, there's nothing to cool it with. There's no working fluid to cool off of. A lot of the steam-based systems in fusion don't make sense for space.

That's where some of this direct energy and energy efficiency matters. It actually comes to some of the origin story of the team that founded Helion. Before spinning off Helion to focus only on fusion, we worked on a mix of things: advanced materials, rocket propulsion, fusion, fusion rockets, fusion materials—all of those things.

Nice.

One thing that people in the aerospace field, especially if you're in deep space, know is that you can't waste anything. Every watt of electricity you make, you better use, because it was expensive to get it, or to get the solar panel. Every joule of heat, every watt of heat you make, you have to reject with a radiator, and it's super expensive and heavy.

You build in space as efficiently as possible. You recirculate your water and your air, and all of those things. You're efficient. That's something we brought into thinking about fusion energy efficiency: If my goal is to make the product, what's the product? The product is electricity. Don't waste any of it.

Recover every watt you can by recovering electricity directly. Recover all the electricity from the fusion process as efficiently as you can. You end up with, just like in space, systems that are smaller, have higher performance, and can deliver more, whatever the mission is. In our case, the mission is electricity.

When you look out there at the stars, I'm really confused by what's going on, because I think there are for sure thousands, if not millions, of advanced alien civilizations out there. I'm really confused why we have not, in a definitive way, met any of them.

So, continuing the pothead questions, what energy source do you think they're using? If what I'm saying is true, that there are alien civilizations out there, do you think it's pretty certain that, in order to expand out into the cosmos, they would be using nuclear fusion?

It's hard to imagine anything else. Where does energy in the universe come from? It comes from fusion. It comes from stars, and we know that that's the process.

Whether they're harnessing the star itself—Kardashev Type II—or bringing fusion along because they want to go somewhere and visit, I think that's pretty likely. You bring up the Fermi paradox: How come we don't see alien civilizations?

Even if there's an infinitesimally small chance that there is life on any one planet, and infinitesimally small that life grows into intelligent life, there are, however, almost infinite planets around infinite stars in our galaxy that have been around for vastly longer than we've been around.

But we don't see it. I think that's a question that many scientists and everyone have wrestled with over the years.

I'm very scared by the implications of that. The scary thing is that, to the point that we made earlier, as we become more and more technologically advanced, we end up destroying ourselves. There could be things we unlock, like nuclear weapons, but plus-plus—new things that happen as you develop super-advanced systems that have close to a 100% probability of destroying ourselves, of destroying any intelligent being.

The kind of intelligent being that's ambitious enough to keep innovating will eventually destroy itself. That will be one explanation. That's scary. That should be a sobering thought. That's at least an inspiring, sobering thought: Be careful with the stuff we create.

But I also just look at humans. We create dangerous stuff and then figure out, sometimes almost at the last minute, how not to destroy ourselves. We're good with deadlines. And we're good at surviving.

I mean, life as we know it on Earth seems to find a way, and intelligent life as we know it—human life—seems to find a way. We do a lot of painful things along the way, but in the end, we somehow survive. It's interesting. There's something in the human spirit that allows us to survive.

So I have a lot of optimism that the super-powerful technologies we create will eventually lead to us still surviving for thousands of years. But then, why are the aliens not here, though? So maybe it's also possible that it's really difficult to traverse space. Maybe it really is that difficult. The physics makes it not easy. There's a lot of space, and it's just hard to travel.

As I have gone further and further in building fusion systems that work, I've become more optimistic around the Fermi paradox specifically. There are several of them. I think you're referring to something called the Great Filter: Something happens that filters out life.

The dark forest is another philosophy around, sure, it's out there, but everybody's hiding because they don't want to be noticed. But I think about something else, actually. The philosophy that I've always loved—and I'm going to pronounce this wrong, so I apologize—is Matrioshka brains.

It's that civilizations get so advanced, and they focus not on expanding physically, expanding in space, and expanding their reach by planting flags in new places, but on growing their cognition, growing their ability to think. They grow their brain. They grow their intellect.

I feel like in the last few years, we've seen a massive trend that maybe this is the thing that happens, and that we do grow our intellect, and we grow the intellect of the species through AI and advanced tools. As a society, we can just get smart enough that we don't need to go plant those flags everywhere.

The Matrioshka brain is a Dyson sphere where a civilization has covered the entire Sun in essentially solar panels, or collects its light in some way, and uses all of that power to power intelligence, to power computers, and to power brains.

I think we're a ways away from that, but maybe AI and fusion together get you along that path sooner. I'm excited by that outcome of the Fermi paradox. At that point, those civilizations have a star that you can't find anymore because it's all covered, and they're there thinking and growing their intellects rather than actually having to physically expand.

Yeah. Exploring and expanding in the realm of cognition and consciousness versus in the realm of space and time, as we, 21st-century colonizer humans, think. Maybe 22nd-century humans will be thinking fundamentally differently.

That's a beautiful vision of the future. Speaking of beauty, you've been doing a lot of really interesting things in a lot of interesting disciplines. What, to you—and this is a ridiculous question—is the most beautiful idea in physics and nuclear engineering, in nuclear fusion and power plants? What ideas, when you just step back, are you in awe of?

I'm continuously in awe that it works. I know that sounds a little silly to say, but the more that I learned in my career about the balance of exactly the right temperatures where life works, exactly the right balance between the electromagnetic force and the strong force, those are things that it's hard to imagine are accidental.

We talk about how beautiful nature is, but then you look at what each of the leaves on the tree really is, and each of the cells, and each of the atoms, and the quantum substructure of that atom, and I'm just amazed that all the pieces come together.

We humans are somehow able to find that perfect balance where it just works.

Just works. Last minute sometimes, but it does work.

The kind of deadlines you're operating under and the group of brilliant people you're working with just stresses me out, but it excites me. So I'm deeply grateful that you're doing this work. You're one of the people building an exciting future.

Thank you for doing that, and thank you so much for talking today.

Thank you very much. It's been fun.

Thanks for listening to this conversation with David Kirtley. To support this podcast, please check out our sponsors in the description where you can also find links to contact me, ask questions, give feedback and so on. And now, let me leave you with some words from the great John F. Kennedy. "We choose to do these things, not because they are easy, but because they are hard." Thank you for listening, and hope to see you next time.