• With the promise of fusion on full display after a U.S. lab achieved “ignition” late last year, fusion companies are raising capital to bring this next-gen green energy to life.
  • Magnetic confinement reactors, such as tokamaks and stellarators, are the leading fusion concept, and are designed to contain super-hot plasma long enough to sustain fusion reactions.
  • Although tokamaks are more abundant and easier to build, the company Type One Fusion just received millions to bring its stellarator reactor to market.

Fusion reactors come in all shapes and sizes, but can mostly be separated into three groups, defined by how they contain the super-hot plasma needed to combine lighter nuclei into heavier ones.

The first is gravitational reactors (a.k.a. stars), which are impossible to recreate on Earth. The second group is inertial reactors, which essentially fire a bunch of lasers at a small pellet and contain the resulting fusion reaction by sheer inertia for only 100 trillionths of a second. This is the concept that finally achieved ignition last December. But it’s the third group—magnetic reactors—that’s arguably the most promising.

Magnetic confinement fusion uses superconducting magnets to contain hot plasma long enough for a fusion reaction to take place. These magnets are absolutely critical, as they keep the plasma from touching any of the other materials in the reactor, and no known material can withstand the over-100-million-degrees-Celsius temperatures required for fusion. But even this kind of fusion divides into a further two camps: tokamaks and stellarators.

While tokamaks are seen by many (including the U.S. Department of Energy) as the leading concept of commercial fusion, stellarators are a bit of an underdog. But they have a few benefits over their popular competitor. Now, stellarators are entering the commercial realm as fusion company Type One Energy—which combines expertise from the Max Planck Institute for Plasma Physics and MIT—received $29 million to bring its stellarator technology out of the lab and into reality.

“Fusion is the ultimate energy source, and its successful commercialization will be a huge leap towards achieving clean and abundant energy for everyone,” Carmichael Roberts, from the Bill Gates-backed Breakthrough Energy Ventures, says in a press release. “Advances in stellarator science, including Type One Energy’s ability to execute a stellarator development project, provide the basis for a very exciting and promising path to practical fusion on the grid in the coming decades.”

Stellarators can be described as cousins of tokamaks, with one key difference. Tokamaks—like the upcoming ITER, for example—use superconducting coils and a central solenoid, while also running an electric current through the plasma itself. Stellarators, on the other hand, do away with a plasma-based current, and instead use a series of twisting superconducting magnets to control the plasma.

Because this twisting configuration is so complicated to build, there are six times more tokamak reactors than stellarators. However, according to the International Atomic Energy Agency (IAEA), stellarators like the Wendelstein 7-X in Germany are better at containing plasma, whereas tokamaks excel at keeping plasma hot.

Although tokamaks are seen as an easier machine to construct, advanced computing has made the creation of stellarators a bit easier. The precise twisting construction of the Wendelstein 7-X was optimally designed by a supercomputer, for example. But according to the Department of Energy, the large bore wire coils needed for these machines still need to be manufactured with millimeter accuracy, which can be an extreme challenge.

The stellarator is also not the only fusion concept getting the startup treatment. Following the success of the National Ignition Facility’s fusion test in December 2022, companies have began investigating ways to turn inertial confinement fusion into a green energy revolution. Tokamaks also have more than their fair share of commercial interest.

Type One Energy says it plans to create a stellarator test bed for examining the fidelity of the company’s models while working toward a working Fusion Power Plant, though the company hasn’t provided a specific timeline. For now, it appears that stellarators will get a shot at bringing their strange “twist” on fusion power to the masses. But like so many universities, institutes, and companies working in fusion energy, Type One Energy likely has a long road ahead.

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Darren Orf

Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.