Making commercial fusion a reality: An Interview with Proxima Fusion’s Francesco Sciortino 

HTGF portfolio company Proxima Fusion recently raised €130 million in Series A funding to bring commercial fusion energy closer to reality.

We sat down with CEO and Co-founder Francesco Sciortino to discuss what this milestone means for the team, the promise of their Stellaris reactor, their journey from research to startup, the potential impact of their “Alpha” demonstration system, and his advice for other deep-tech founders facing major challenges. 

Congratulations on your successful funding round! What does this milestone mean for you as a team, and how will it affect your future goals? 

This means that we have the validation of both our approach and the team we have built. Working with the Max Planck Society in Germany and our simulation-driven engineering approach have proven successful. 

We have moved faster than we thought was possible, delivering the Stellaris design and magnet technology in the lab. We have now secured financing to go full steam ahead with our hardware milestones. We are now the largest stellarator-based fusion company on the planet. We have raised as much money as all our stellarator competitors combined. We now have no excuse but to deliver. 

Can you walk us through the technological foundation behind your approach with Stellaris? 

So, the general category of devices that we work on is magnetic confinement fusion. This includes both tokamaks and stellarators, but also other subcategories. I have a background in tokamak physics. Tokamaks are the most conventional of the magnetic confinement fusion approaches. They are magnet systems that look like doughnuts, where you try to confine hot, ionized matter in helically twisting magnetic fields. 

Stellarators are very similar. In fact, you could say that a tokamak is a special type of stellarator. However, for the longest time, stellarators were blocked on the physics side. But in 2022, the Wendelstein 7-X stellarator at the Max Planck Society in Germany met its major design targets, and we now know that stellarators can be built and that we can design new stellarators to be power plants rather than just science experiments. Proxima Fusion spun out of the Max Planck in early 2023, to bring stellarators to commercialization. As stellarators have been getting more and more attention, there are now eight stellarator companies worldwide. 

How is Proxima Fusion’s approach different from others in the fusion space, and what are you ultimately aiming to achieve? 

All of these stellarator startups are still relatively small compared to the largest tokamak company in the world: Commonwealth Fusion Systems, or CFS for short. CFS has raised more than $2 billion, and they are very good at what they are doing. They are trying to build a tokamak that makes energy with the same kind of superconducting magnet technology that Proxima is working on. We agree on lots of things between tokamaks and stellarators. The physics basis is the same, but the biggest difference is that well-designed stellarators can work in continuous operation, and they can be completely stable.

That is the moon shot within the moon shot we are making with Proxima. Our goal is not to design something that creates energy for a short time, just a fancy flash of light powered by fusion. Instead, we are actually trying to build a power plant.

There are around 60 fusion companies right now, companies that actually aim to make reactors, and out of these, approx. 10 fusion startups have raised €100 million or more. We are now in a race to build the net energy device on our path to the first fusion power plant in the world. Let’s see who succeeds!  

What was the journey from research to independent startup like? What were the most important insights that you and your team gained along the way? 

We started out as physicists researching tokamaks and stellarators. Our co-founder Martin Kubie has a background in mechanical engineering and has worked at Google X. Spinning out from the Max Planck Institute for Plasma Physics, we had to adapt and create a new way of working with a more engineering-centric perspective and a greater focus on simulation in order to enable faster iteration. Iteration speed is everything. You cannot iterate on building a whole stellarator, it is too big, so you cannot iterate on full scale hardware integration, but you can integrate on the large system in software. To do so, you have to work on a fusion concept that is experimentally validated. Otherwise, if you do not trust your models, then you can iterate as fast as you want, but they are going to be continuously wrong. For us, the enabler was to recognize that stellarators now have a much more mature physics basis than just a few years ago.  

As a spin-off from Max Planck Society, we have always been big believers in public-private partnerships and the importance of working together. It is not necessarily simple. We are two very different organizations, but the important thing has always been the mission-driven mindset and finding the common ground to get this thing to lift off at all. And I think something we Europeans still need to hone is the ability to increasingly translate theoretical research into operations into practical engineering. 

We learned that hiring is very hard, but also the most important thing: Finding the right people is everything. The quality of the founding team is a big indicator of what is to come. But the only thing that really matters is whether you know how to hire people better than yourself, and that we have arguably done well. Perhaps that is the one thing that was not quite clear in the very early days, but somehow, we have picked up speed very quickly. 

Your demonstration system “Alpha” is planned to start operations in 2031 and then produce more energy than it consumes. Why is it such a critical step toward commercial fusion energy? 

The demonstration system that we call Alpha is an energy-producing device. The process of the stars down on Earth. It is a demonstration and not a power plant yet, but Alpha is designed to be the last thing we will ever need to build before we construct a power plant. 

We believe it is the right kind of device for a fusion power plant, which is operating continuously and is fully stable. That is the sweet sauce of Proxima: If we get Alpha done, Proxima might be one of the most valuable companies on the planet. But that is proportional to the value of the market and it is generally related to the need for clean, safe and abundant energy. The reason why we have been chasing fusion for a good part of 70 years is that there is fundamentally nothing else quite like it. We are talking about burning heavy forms of hydrogen on a nuclear level, so joining light nuclei, heavy forms of hydrogen, not like uranium, plutonium and so on. They are at opposite ends of the periodic table. We are at the simplest part of the periodic table. Most of the universe is made up of hydrogen. The fuel is nearly infinite.  

How could fusion energy — and Alpha in particular — impact the planet, society, and the way we think about energy? 

One bottle of this heavy hydrogen fuel could power Munich for a week. Just one spoonful of this fuel is equivalent to 13 tons of coal. This is certain, this is not a theory. We can do this at a small scale in the lab. We know that the sun is burning in this way. This is simply how the universe is powered. The question is: can we make it cheap enough? And can we build these power plants fast enough? That is what will determine the future. It is not a physics proof of principle. What we need is an engineering and commercial proof of principle.  

Germany is facing an energy crisis, and Europe is facing a technology sovereignty crisis. There has never really been a better time to think about this massive scaling of fusion systems similar to the way France scaled their energy system around fission in the 1970s. If we want fusion to account for 20–30% of the world’s energy production, and we need to act quickly to have an impact on the climate over the next few decades, then we need to consider how to build 1,000 power plants fast. That means we need to think of a system that can scale. 

What advice would you give to other deep-tech founders tackling major technological challenges? 

No egos allowed, you need a mission-first mindset. You need to be fully aware of why you are dedicating so much of your life to something. We could all be doing things that pay better or allow more free time. We are here out of choice and the mission is worth a significant chunk of your life, so this must be clear to the founders. 

Thanks so much for the interesting insights!