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David Kirtley

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180

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2025-11-17

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2025-11-17

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1. “Large scale multinational, complex, huge systems. You want to actually take the smallest thing you can build that did accomplish the mission. In Infusion, there is a minimum size, but accomplishes the mission and then build it quickly and build whole teams around building it quickly and incentivize folks to move quickly, iterate and learn. And kind of 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. And 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 to make a large complex”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

2. “And so a lot of what I think about is how do we do those two things together. And a lot of that is scale. And a lot of that is thinking about, and not big scale. In fact, it's the opposite of that. It's small scale. It's how do you build a product that's mass producible that you can build quickly and learn quickly? And what I've found in my career at this is that they're actually the same thing and that the faster you can build a thing, the faster you can learn if that thing works, the faster you can now iterate on that and build the next thing. And so what I have spent my career building is teams of humans and a company that are builders that can build high technology things quickly. That if you want to do R&D, you don't want”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

3. “So, I think about this in a couple of ways. The need. We look to the world and we know the world needs clean, low-cost. Safe electricity. And just to meet our needs today, and not to even talk about the needs of tomorrow or the needs of AI or the growth that's probably coming, just to me today. And so, but fundamental to that is it has to be a product that people will buy. It has to be a generator that is making that electricity at low cost. And it's got to be soon.”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

4. “And so that's what 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. So if you make them really small and they don't produce electricity, and there is some minimum size diffusion. And that's really important. Fusion scientists and engineers don't see you'd ever have a fusion generator on the back of your DeLorean, for instance. The physics doesn't let that one happen. At least physics is, as we've understood for the last 100 or 200 years.”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

5. “How much concrete? How much concrete? How much steel? How much copper and aluminum? Different materials cost different amount. But at the end of the day, the cheapest function is the least amount of materials.”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

6. “Your goal is to manufacture a product for as low of 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.”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

7. “That gets to one of the other price that gets to money. So our goal is we want 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. And while it can be clean, it's not going to be deployed. And so that always has to be a part of why what the promise of fusion is that can be low cost. How do we know how much diffusion systems cost? It's a really great question. And a lot of it comes down to fundamental size, that you have to just build things. And so there's some really first principles, cost engineering you can do around power plants for fundamentally what do they cost, how much concrete went into it, fundamentally how big is it, and that if you're doing a good job of manufacturing.”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

8. “To those higher temperatures, we talked about B squared is in T. B squared is density times temperature. Well, for a given magnetic field, density and temperature are now inverse. 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, is if you can now recover energy at three times the energy efficiency at 80-some percent versus 30-some percent, and recover all your input energy, then now it's actually about the same size. Because for the same electricity output, not energy, it's not energy that we're worried about. It's electricity we're worried about. Electricity output, now you can actually build systems of similar size and similar energy. Only they're now at this much higher efficiency.”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

9. “Yeah, so we talked about how helium-3 is, so from the fusion physics point of view, we talked about 100 million degrees. That's the temperature that deuterium and tritium fusion works really well. And that's the temperature that traditional fusion folks have really focused on getting to. That's the threshold of 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. Yes fusion happens for helium deuterium and helium-3 at 100 million degrees, but it's not its optimal temperature. And 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. Temperatures hard. And so you have to push to even higher temperatures than you had before. And so that's one of the downsides. The other downside can be as you”

   2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

10. “Helium 3 is also stable, but it's not found commonly. Unfortunately, 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 so you have to make it. Or you have to go into space. And there's a whole nother thing about where do you get it? Do you get it from the moon? Jupiter has, it turns out massive amounts of helium-3. And so, but when you take deuterium and helium-3 and you fuse those together, you also get that helium particle, that alpha particle that we call that infusion. But instead of the neutron, you get a proton. And that proton is a charged particle. It's a helium, a hydrogen nucleus. That proton is now trapped in the magnetic field, pushes back, and you can extract that electricity. Now, there's 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.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

11. “But it doesn't push back on the magnetic field. So in one of these high beta systems, it's actually not a great fuel at all. And so 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. Now we talked about deuterium, heavy hydrogen. Well, helium-3, the nucleus is also called a helion. That's why we name the company that is light helium, which is a normal helium, which is what you find in a balloon. It's two protons, two neutrons. It's very stable and found commonly.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

12. “Side benefit that it turns out is actually maybe the tail that wags the dog is that not only do you at high efficiency get out any of the new fusion energy, which is great because that's what you want, make electricity from fusion, but you also get to recover all of that magnetic energy you put back into it. And that's the really powerful one. And that's something that folks have demonstrated over 95% efficiency, that you can put electricity in diffusion and then get that electricity back out. And 95% efficiency plus some very high efficiency, maybe 80%, maybe higher of all the fusion product electricity too. So now you're just 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, but also pushes you to other fuels. So we talked about how deuterium and tritium fuels make this neutron, which leaves the system to boil water, to run steam turbines.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

13. “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. And we're using fusion to make electricity. And so from my point of view, that should be the focus is how do we get to that. So that's the efficiency of that thermal energy that makes it out to electricity, what it is not a measure of how much energy you put into the system and what happens to that in terms of you started this campfire with a blowtorch. What about all that blowtorch energy? What are you getting for that? And so I think that's something that Hibeta is one more.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

14. “And so you use an piston engine, you used the motion of the piston, the pressure on it and the motion of it to do something useful. And in a piston engine, it's to turn a crankshaft and run a turn a crankshaft. Run wheels, or maybe even a piston engine to turn a crankshaft and run a generator and make electricity. In fact, you can do it pretty high efficiency in a generator using that method, using the expansion of that piston. And what we do is use the expansion of the magnetic field to extract that electricity. And we believe you can do it much, much higher efficiencies. In fact, there's been theoretical papers that show not 30 to 35 percent efficiency like a steam turbine can do, but 80% efficiency, 85% efficiency. Extract much more of the energy of the fuel in that process.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

15. “But what I think there's 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 electromagnetic force that's now compressing the fusion fuel, increasing in temperature, it's getting hotter, it's increasing in density fusion is happening. New fusion particles are being born, and those particles are not just stoking the flame. They're not just holding on the campfire, like in the tokamak, but they're doing another thing, which is really powerful, which is they're pushing back on the magnetic field. They're applying a pressure, that pressure induces a current. We can extract that electrical current. But it takes you into another direction. So your analogy of the campfire now breaks down. Because now the campfire is expanding. It's pushing back on something. And so now it's the analogy of the piston engine. As you move from the match, the campfire to now piston.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

16. “Heavy isotope of hydrogen where you have an extra neutron, and tritium is a very rare form of hydrogen. That's an unstable form. It's so rare. It's hard to get, where it has two neutrons and a proton. And when you fuse those together at very high temperatures at very high densities or high enough densities and very high temperatures, they make helium, which is a charged particle, which stays inside. Boil water to heat the water, and then at 30 35% efficiency, then convert that through a steam turbine into a cooling tower and cool off the fuel and extract electricity. And we know steam turbines, coal plants do this nuclear vision reactors do this. And so we know how to do that. And that's the traditional way of doing it.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

17. “Yeah, I like the analogy of The match in the campfire. And I hear that a lot in Fusion, where a lot of what steady fusion, think of Stellarador or Tokamak, is attempting to do is take a little bit of fuel, that match, and then add heat to ignite that match. And then put it with enough fuel and in the right conditions and hold on to it for a long time that it grows into a campfire, even if they do a good job of bonfire. It's creating a tremendous amount of energy in that steady system, burning fuel in the same place, generating some ash, generating a lot of heat in that reaction. And in a traditional tokamak or a stellarator, that's a lot of what you're doing is you're holding on to the heat as much as possible to keep that reaction going. And in that, the optimal fuel is called deuterium and tritium, where you have deuterium is a”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

18. “Is electromagnetic current and current running in a wire. And what that does is pushes current back in the wire. And so the plasma itself now pushes back on the magnetic field, pushing electrical current out of the system, and charging the capacitors where we started this whole process.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

19. “Increasing from one to five to ten, 20 to even higher magnetic fields. And as you do that, the plasma heats, you compress it, increasing the field and pressure. Fusion is now happening. New charged particles are being borne inside this system with a tremendous amount of heat and energy, but in charged particles. And this is where the beta really, really works in your advantage, is that just like magnetic pressure on the outside, magnetic pressure is in KT compresses the fuel and increasing pressure and temperature. When the pressure and temperature of the plasma increase in KT increases, it pushes back on the magnetic field, increasing the magnetic field on the outside of the plasma. And what that does is magnetic field”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

20. “Plasmas can last for hundreds or thousands of times the basic theory has shown that now you can have long enough lifetimes. So what that means is in a practical fusion system that there are lifetimes of these high beta pull systems between 100 microseconds and a few milliseconds, thousands of a second. And you hold on to it for a few thousandths of a second, you do fusion, and then you exhaust it. And so the whole process in this is we start with a magnetic field that fills the full chamber. You then inject fusion fuel, you ionize it, superheating it now to a nice cold 1 million degrees. But hot enough that you have charged particles, you have plasmas. You can then start increasing the magnetic field. You form a field reverse configuration and then rapidly increase the magnetic field further.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

21. “But then I said pulsed. And pulsed already implies shorter tau. And so that is in the fusion field the name of the game. Folks will have a very inertial fusion, will have a nanosecond tau, very short, but then very high pressure. They don't have magnetic fields, but very high pressure. And then in stellarators and tokamax, your goal is very long tau, but you'll have much lower density, and you can't really go too much in temperature, but they'll have much lower density. And so where we live in the post-magnetic or the magneto inertial fusion is in the middle, is in extremely high magnetic fields, increasing pressure as much as you can, and then keeping them around long enough. And so that gets to the tau. That gets to that energy confinement lifetime. And also, it gets to stability. And so this is the thing that this field reverse configuration, which has showed that we can build, that these”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

22. “And fusion reactions. And so that tells you you want to go to a maximum magnetic field as you can. Pull systems are really powerful. Pulse systems have showed when you do pulsed magnetic fields compared to a steady magnetic field. Researchers have shown over 100 Tesla magnetic fields, where in a steady system, people have showed in the 20, maybe high 20 Tesla systems. And if it's beta the 3.77 power, already you can see massive fusion power outputs by doing upholstered system.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

23. “Not yet, but we need to because that's really important. And so we can even talk even a little bit further about how fusion scales. And so infusion, the hotter you get the fuel, the more fusion you get. And we know that by increasing the magnetic field, b squared is in T, you increase density and temperature together more density, more temperatures, more fusion, plus more temperatures, even more fusion. And so what we see is that in these types of systems, a scaling very clearly, a magnetic field to the 3.75 power, or even in a lot of demonstrations, 3.77, that's specific. Scaling. That's a very strong scaling of fusion power output.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

24. “We call that tau, so N T in tau long enough that fusion happens and a lot of fusion happens more than any of the loss rates that are happening in Tau. And in beta, with b squared, you know already two of those parameters, NNT, are equal. And so that tells you right away the goal is to maximize magnetic field. Absolutely maximize magnetic field. And most folks in magnetic fusion, whether it's a tokamak or it's a theta pinch or it's an FRC, are attempting to do that, maximize the magnetic field. So we're all pushing to that. What's really nice in pulse systems is that we know how to do that. In fact, In a pulse system 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.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

25. “So, how much fusion do you get out in these systems? And that's really the right key question. So, we already talked about beta, that b squared the magnetic pressure is equal to NKT and being the density, t being temperature. And then we talked about fusion, where”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

26. “Of the things we're seeing in artificial intelligence and reinforced learning to be able to speed up that process. And so we're watching and starting to work on that now of can we now, rather than using it where we use it 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. But in fact, do it more real time, or you're now an operator can pull up what the AI or what the machine learning would have predicted it should have done, and then use that to understand what's happening in the actual programs and the actual generators themselves.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

27. “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, but let's look at the magnetic field topology. How do I design the magnet, the shape of the magnet? Exactly, the timing of the magnet, exactly. I have to trigger one magnet and the next magnet next to it and the next magnet next to it. How do I have that shape? And that design. And so that's where you're using those more advanced tools. Now, those, unfortunately, those are still too slow. And so those simulations may take a day or two to run. And so an operator right now does a lot of simulations ahead of time then collects data through their operations of the machines, making these field reverse configurations, going through parameter sweeps. And then the simulation team then goes back and looks at that data and compares it with simulations. I'm really excited about some.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

28. “Yeah, each of the different simulations we analyze and use it to design different parts of the machine. So at the MHD level where we have the spike, where we actually have the circuit model, now our design team uses this to design the circuitry. We're designing which capacitor to use, which switch to use, how many cables to use, literally to that level, how big of a cable to use. So as we're doing power plant designs right now, those are the tools we're using today, every day. The team is using.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

29. “Hybrid codes, we call them, particle and cell codes, now treat the ions as particles. And that lets us measure and simulate the behavior. I mentioned the stability criteria, S star over E, the top behavior. That behavior, we now need these more advanced codes to be able to simulate. And those are more modern. Those we've only been able to apply in practice for the last few years, actually, which is pretty fascinating, that the old stability rules were built off of testing empirical tests. Or now we can simulate that and we know why they work and how they work and we can do some predictions on them. And so that's really fascinating that we've been able to push those boundaries.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

30. “Drive the plasma physics model. And that's one level of simulation. We use that to do design work and then 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 and we think about the ions and we treat the ions as particles and we look at the ion behavior. And 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.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

31. “We have multiple codes at different levels because one of the main computational challenges is amazingly, even given all that we have been have built for fusion systems, computers are still not fast enough to measure, to simulate everything. And so we have a number of codes that we use. One, we call fluid codes, where you treat the ions, the electrons, all these fusion particles. You treat them as fluids, as gases, 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 and the electrical current and the switches. Well, we actually simulate the full thing, starting literally with the spice model. More of that electrical engineering, we start with the spice model and use that to”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

32. “How this typically works, at least in our systems, is that we will design a system with a combination of some numerical simulation tools that we've developed based off of decades and decades of amazing government programs, national lab programs developed these numerical codes. We use a kind of a code called an MHD Magnetohydrodynamic code. for the engineers out there who are used to CFD computational fluid dynamics. This is very similar. You take the same sets of equations actually and add the electromagnetic equations on top of those. And so you get magneto hydrodynamic.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

33. “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. And so 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 you're running long periods of time, you still have all computers doing both the triggering and the measuring of how they're performing real time the whole time.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

34. “And 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. So as these switches are conducting, they broadcast a signal that says, yes, I'm electrically conducting an optical signal, fiber optics, that come back to a central repository where we detect those signals. And so real time, we're monitoring all of this so that we know that these systems are behaving and operating at their optimal performance.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

35. “And then we trigger that and then let it go and measure fusion happening. But during that process have to be real-time recording and measuring 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. And so some of the pioneering things we've been able to do is that real time, you're monitoring all of these switches. You're watching who is triggering correctly, who is not triggering correctly. And if systems aren't working, you're shutting down this because you want to make sure that all the sequences are operating correctly. So some of the key diagnostics, it's actually pretty amazing that even early in my career, we didn't have a lot of fiber optics built into the system. And now it's absolutely essential. And so every one of these electrical switches.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

36. “To be able to both program, control, and then detect how they're operating. Do it all very fast. So, in a typical sequence, we will pre program, the operators will pre program a sequence, usually fed from a numerical simulation of expecting how the fusion system will 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 diffusion conditions.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

37. “The diagnostic systems is 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. And we need to know if it's working right. And so in one of these FRC or these pulsed magnetic systems, you won't have just one electrical switch. I 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, vectors systems we build now, tens of thousands of parallel electrical switches, all operating in harmony together. And so you need to be able to be build a system. And this is what we spend a lot of time with. And I made the joke, that in a lot of ways helions and electrical engineering company.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

38. “And though a lot is now more and more run in Python. And so we do a lot of Python. We do some Java. And then we also have because of the speed of this, it's a lot of assembly language programming. So we go right to the assembly level of the programmable logic FPGAs. And we program those. And so to be able 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 optic because the wires are just too slow. And so fiber optic, I can respond. I can send photons at the speed of light. And so those fiber optics can respond in nanoseconds. And then I trigger those fiber optics with programmable logic that we've programmed in the hardware assembly language.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

39. “Do this reversal. We pre program it and then we run a sequence, and then fusion happens. And so in this sequence, programming language, we use a variety of them. Some of the fusion codes are actually written in Fortran still.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

40. “So, I'm continuously amazed by what the pioneers in fusion were able to do before the computer existed, because they had to control things at this scale. But maybe it was pretty hard and why we've been able to take what they did and build on it, because now we use modern gigahertz scale computing to be able to do this. And so even when I started my career, we talked about like 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. But now gigahertz means I'm going to do a thousand operations in that one microsecond. So I can do more useful things. So we use mostly, this is way too fast for any human to respond to. So we use what's called programmable logic. So we program in sequences to the fusion system to be able to”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

41. “And be able to understand the system in that speed. And if you get it hotter, it goes even faster. And you have to go faster. And so we look at those and that's how we think about the systems. We measure everything in microseconds, not in seconds. And so when you do fusion, it's pretty wild. It's literally a flash. Fusion happens. And it's over. You start it. You do a lot of fusion. You recover energy from it. And then you turn it off before the human eye can really respond.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

42. “So, if temperature is velocity That means they're moving quickly over a given amount of space. Speed is distance divided by time. And so if you have a machine of a certain size and it's moving very fast, that tells you the time that that particle is moving from place to place in that machine. And, in fact, if it's a million miles per hour, these are on the order of 100 kilometers per second, which you can flip that around and you can say you're moving at meters per microsecond. So, feet per millionth of a second. And so 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.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

43. “You have this high energy particle, which is why we like fusion, is moving at high velocity, and there's another one moving at high velocity. They will come together, they will collide, and they will 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 that material, and usually blow off some chunks of that material. So we don't do that. We keep those charged particles in a magnetic field. So they just bounce around and they don't ever touch anything. And that's really important. And so it's less thinking about it from the way we normally think about hot and cold and more thinking about it from a velocity point of view.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

44. “This plasma and go even hotter, and 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 these random motion of particles, because now they're all individual particles, moving at very high velocity. So what it really is a measurement of is velocity. It's really a measurement of how fast is that particle moving. And that's how I really think about temperature.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

45. “Is the air here that 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 is roughly on the same temperature. But you can be what is called rified. And this is like space. This is where now you have particles moving around, but they don't collide with each other very often. And so you can have one very, very high energy particle and very cold energy particle, and they may not even touch each other, but maybe occasionally they bang into each other, they collide, and then they transfer energy. And that's where we call rarefied. And then you can go even hotter than that. And that's where now the actual atomic states, which has the nucleus, which is a proton and a neutron, and an electron gets so hot that electron gets energized and then escapes, leaves the system. And 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. So way hotter than what we're used to. But now we're going to go hotter.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

46. “Yeah, so a couple of key things happen. So, when gas is that hot, we talk about the states of matter. You have solids where ice, it's cold, the atoms are now bound in a lattice structure together. They're held together. And then liquid, you've broken a lot of that lattice structure. They can move around. They have some kinetic energy, but they're still pretty contained. They stay in the bowl. Keep heating it. Now you're in gas. And now these particles are free to move around. They're moving around. They're bouncing off of each other all the time. And 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. So when we think about most gases that humans interact with, they act like a fluid. And what I mean by that is that they're colliding with each other so often that the particles at any one place here, the air is roughly the same temperature.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

47. “So, if you take your top and you spin it faster, it's more stable, but you got to make it hot. And so here's the trick. How do you make something hot that's starting cold? And it has to be hot by definition. And so that's part of the challenge of what we do day to day is getting to these hot plasmas and where people have other people have tried to make FRCs and not been very successful. It's because they couldn't get it hot enough fast enough. Is 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 be able to get it hot enough soon enough that you can keep it stable the whole time.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

48. “It's a great question. So it is a requirement of the system that you must design it with this parameter in mind. The hard part is you have to design it with S star over E being satisfied the whole time. And here's the extra trick here. S star over E is also a measure of temperature. And it all comes back to temperature. The hotter you make them is the same thing temperature is kinetic energy is the faster you're spending.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

49. “We can design these for very long lives. The theory of the systems we make say that they should last for a few microseconds at most us and others in the field have been able to make them last for thousands of microseconds, thousands of times what the basic criteria would tell you. And so we know now how to do this. And so we just designed them with this built into them.”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source

50. “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. And 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, which is the elongation of how long it is. And so maybe fortuitously, thank you, Nature, gave us a win here, which is that how we make these in these long solenoids is naturally very, very long. And so we can build these with a 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. And so we now know we can design with a given S star over e per”

    2025-11-17 · Lex Fridman Podcast · #485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy · IDENTIFIED FROM THE TRANSCRIPT · source