Late last week, in a rare sit-down before a small audience, this editor spent an hour with Sam Altman, the former president of Y Combinator and, since 2019, the CEO of OpenAI, the company he famously co-founded with Elon Musk and numerous others in 2015 to develop artificial intelligence for the “benefit of humanity.”

The crowd wanted to learn more about his plans for OpenAI, which has taken the world by storm in the last six weeks owing to the public release of its ChatGPT language model, a chatbot that has educators and others both dazzled and alarmed. (OpenAI’s DALL-E technology, which enables users to create digital images by simply describing what they envision, generated only slightly less buzz when it was released to the public earlier last year.)

Because Altman is also an active investor — one whose biggest return to date comes from the payments startup Stripe, he said at the event — we spent the first half of our time together focused on some of his most ambitious investments.

To learn about these, including a supersonic jet company and a startup that aims to help create babies from human skin cells, you might tune in for the 20-minute-long video below. (You’ll also hear Altman’s thoughts about Twitter under the stewardship of Elon Musk, and why Altman is “not super interested” in crypto or web3. “I love the spirit of the web3 people,” Altman said with a shrug. “But I don’t intuitively feel why we need it.)

We’ll feature more from that fuller conversation, including OpenAI, soon. In the meantime, below is an excerpt from our discussion about one of Altman’s biggest bets: a nuclear fusion company called Helion Energy that, like OpenAI, is aiming to turn a long-elusive promise — this one of abundant energy — into reality. The excerpt has been edited lightly for length and clarity.

What makes a Sam Altman deal?

I try to just do things that I’m interested in at this point. One of the things I have realized is, all of the companies I think I have added a lot of value to are the ones that I sort of like to think about in my free time on a hike or whatever, and then text the founders and say, ‘Hey, I have this idea for you.’ Every founder deserves an investor who is going to think about them while they’re hiking. And so I’ve tried to hold myself to the stuff that I really love, which tends to be the hard tech, [involving] years of R&D, [is] capital intensive, or is sort of risky research. But if it works, it really works.

One investment that’s particularly interesting is Helion Energy. You have been funding this company since 2015, but when it announced a $500 million round last year, including a $375 million check from you, I think that surprised people. There aren’t many people who can write a $375 million check.

Or, like, many people who would [invest it] in one risky fusion company.

Which have been your most successful investments to date?

I mean, probably on a multiples basis, definitely on a multiples basis: Stripe. Also I think that was, like, my second investment ever, so it seemed a lot easier. This was also a time when valuations were different; it was great. But, you know, I’ve been doing this for, like, 17 years, so there’ve been a lot of really good ones, and I’m super grateful to have been in Silicon Valley at what was such a magical time.

Helion is more than an investment to me. It’s the other thing beside OpenAI that I spend a lot of time on. I’m just super excited about what’s going to happen there.

Lawrence Livermore National Laboratory had a nuclear fusion breakthrough last month. (Using an approach involving giant lasers, its scientists announced the first fusion reaction in a laboratory setting that produced more energy than was used to start the reaction.) I wonder what you think of its approach, which is very different froms that of Helion (which is building a fusion machine that’s reportedly long and narrow and will use aluminum magnates to compress fuel, then expand it to get electricity out of it).

I’m super happy for them. I think it’s a very cool scientific result. As they themselves said, I don’t think it’ll be commercially relevant. And that’s what I’m excited about — not getting fusion to work in a lab, although that is cool, too, but building a system that will work at a super-low cost.

If you look at the previous energy transitions, if you can get the costs of a new form of energy down, it can take over everything else in a couple of decades. And then also a system where we can create enough energy and enough reliable energy, both in terms of the machines not breaking, and also not having the intermittency or the need for storage of solar or wind or something like that. If we can create enough for Earth in, like, 10 years — and I think that’s actually the hardest challenge that Helion faces as we sketch out what it takes operationally to do that, to replace all the current generative capacity on Earth with fusion and to do it really fast and to think about what it really means to build a factory that’s capable of putting out two of these machines a day for a decade —  that’s really hard but also a super fun problem.

So I’m very happy there’s a fusion race, I think that’s great. I’m also very happy solar and batteries are getting so cheap. But I think what will matter is who can deliver energy the cheapest and enough of it.

Why is Helion’s approach superior to what dozens of nations are working on in Southern France?

Yeah, well, that thing, Iter, I think probably will work, but to what I was just saying earlier, I think it will be commercially irrelevant. They also [themselves] think it’ll be commercially irrelevant.

The thing that is so exciting to me about Helion is that it’s a simple machine at an affordable cost and a reasonable size. There’s a bunch of different elements of it other than the giant [experimental machine being developed by these nations], but one that is very cool is that what comes out of the reaction is charged particles, not heat. Almost all other [alternatives], like a coal plant or natural gas plant or whatever, makes heat that drives a steam turbine. Helion makes charged particles that push back on the magnet and drive an electrical current down a wire. There’s no heat cycle at all. And so it can be a much simpler, much more efficient system.

I think is missed out of the whole discussion on fusion but [is] really great. It also means we don’t have to deal with much nuclear material. We don’t ever have dangerous waste or even a dangerous system. You could touch it pretty shortly after it turns off.

It’s building a big facility right now. Has it proven its thesis yet?

We’ll have more to share there shortly.