#485 – David Kirtley: Nuclear Fusion, Plasma Physics, and the Future of Energy
Lex Fridman Podcast
Lex Fridman
4.7 • 13K Ratings
🗓️ 17 November 2025
⏱️ 165 minutes
🧾️ Download transcript
Summary
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Transcript:
https://lexfridman.com/david-kirtley-transcript
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EPISODE LINKS:
David's X: https://x.com/dekirtley
David's LinkedIn: https://bit.ly/4qX0KXp
Helion: https://www.helionenergy.com/
Helion's YouTube: https://youtube.com/HelionEnergy
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OUTLINE:
(00:00) - Introduction
(03:00) - Sponsors, Comments, and Reflections
(11:35) - Nuclear fission vs fusion
(21:35) - Physics of E=mc^2
(26:50) - Is nuclear fusion safe?
(32:11) - Chernobyl
(38:38) - Geopolitics
(40:33) - Extreme scenarios
(47:28) - How nuclear fusion works
(1:20:20) - Extreme temperatures
(1:25:21) - Fusion control and simulation
(1:37:15) - Electricity from fusion
(2:11:20) - First fusion power plant in 2028
(2:18:13) - Energy needs of GPU clusters
(2:28:38) - Kardashev scale
(2:36:33) - Fermi Paradox
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Transcript
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| 0:00.0 | The following is a conversation with David Kirtley, a nuclear engineer, expert on nuclear fusion, |
| 0:05.9 | and the CEO of Helian Energy, a company working on building nuclear fusion reactors |
| 0:12.0 | and have made incredible progress in a short period of time that make it seem possible |
| 0:17.3 | like we could actually get there as a civilization. This is exciting, because nuclear fusion, |
| 0:24.0 | if achieved commercially, would solve most of our energy needs in a clean, safe way, providing virtually |
| 0:30.1 | unlimited clean electricity. The problem is that fusion is incredibly difficult to achieve. You need to |
| 0:36.7 | heat hydrogen to over 100 million degrees |
| 0:39.4 | Celsius and contain it long enough for atoms to fuse. That's why the joke in the past has been |
| 0:45.9 | that fusion is 30 years away and always will be. Just in case you're not familiar, let me clarify |
| 0:53.7 | the difference between nuclear fusion and nuclear fission. |
| 0:57.9 | By the way, I believe according to the excellent sample size, |
| 1:02.4 | subreddit post by PM Goodbeer on this, |
| 1:06.2 | the preferred pronunciation of the latter in U.S. is nuclear fission like vision, and in the UK and |
| 1:13.6 | other countries is nuclear fission like mission. I prefer the nuclear fission pronunciation |
| 1:21.8 | because America. So today's nuclear power plants use nuclear effusion. They split apart heavy uranium atoms to |
| 1:32.6 | release energy. Fusion does the opposite. It combines light hydrogen atoms together, the same reaction |
| 1:39.4 | that powers the sun and the stars. The result is that it's clean fuel from water, no long-lived radioactive waste, |
| 1:47.2 | inherently safe because a fusion reactor can't melt down. If something goes wrong, the reactor |
| 1:52.6 | simply stops. And there's no carbon emissions. On a more technical side, Healyne uses a different |
| 2:00.2 | approach to fusion than has traditionally been done. |
| 2:03.9 | Most fusion efforts have used Takamax, which are these giant donut-shaped magnetic containment chambers. |
| 2:10.3 | Helian uses pulsed magneto-inertial fusion. |
... |
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