Future is fusion? The quest to build a star on Earth

The quest for fusion energy – the clean, potentially limitless source that could end mankind’s power woes – is at least a century old. Now, a handful of startups say we are closer than ever to making it happen. In the next few years, these companies say, their fusion machines will produce more energy than they take to run. Soon after, they will start generating electricity for factories, data centers, steel mills and more.
Big-name investors, including Bill Gates, Jeff Bezos, Vinod Khosla and Sam Altman, have staked hundreds of millions of dollars on this. Yet, closer than ever does not necessarily mean close. Fusion’s history is a graveyard of missed deadlines and thwarted milestones. The sunny view is startups moving more quickly than govt labs ever could.
Creating a working star on Earth might sound flat-out impossible, had scientists not already gone so far toward doing it. First you need to heat a puff of gas to over 100 million degrees Celsius. This makes the gas so hot that the electrons are ripped free from their atoms. So hot that the gas enters plasma state of matter.
With enough heat, the atoms start to fuse. Make your plasma hold onto this heat for long enough, and at high enough pressure, and more energy comes out than you put in to heat it up. Fusion is the opposite of the fission process that powers today’s nuclear plants. Atoms don’t split; they weld together. The basic fuel isn’t uranium, but hydrogen extracted from seawater. There’s no threat of runaway reactions, and the radioactive waste it leaves behind is less dangerous. Making it happen, and controlling it, is just much, much trickier.
Plasma wriggles and squirms like a snake of superhot Jell-O, so you have to hold it steady, otherwise it could melt your equipment. Or it might just fall apart. Inside the Sun, gravity holds the plasma together. On Earth, people use superstrong magnets or lasers. By this point maybe you’ve done it: Atoms are fusing, high-energy particles are blasting out of the plasma. Your machine has to survive the pummeling. But it also has to put the energy to work, producing electricity, keeping the reaction going, all without disturbing your plasma.
At the innermost sanctum of Commonwealth Fusion Systems‘ enormous new building in the Massachusetts countryside, in a room as airy and grand as a temple, a colossal machine will soon be placed at the altar. In a circle around its core will sit 18 giant magnets, each powerful enough to hoist an aircraft carrier. When the machine is turned on, the magnetic forces within will be as strong as 10 heavy rockets lifting off from Earth. Only in the fusion industry would this be considered a compact machine, yet that’s what it is: a small but souped-up version of a tokamak, the doughnut-shaped fusion device that scientists have built scores of since the 1960s. (“Tokamak” is a Russian acronym.)
If there’s a big fish in the commercial fusion pond, Commonwealth is it. Since its founding in 2018, the company has raised over $2 billion. Commonwealth is aiming for SPARC, its demonstration machine, to produce net energy “in a commercially relevant way” in 2027. Its next machine, ARC, is the one it says will generate electricity for paying customers, in the early 2030s.
The biggest tokamak being built anywhere on Earth, a multinational project in France called ITER, is on track to cost tens of billions of dollars and won’t be ready for experiments until the mid-2030s.
But most of today’s startups aren’t following ITER and Commonwealth models. They think they can do fusion more cheaply and easily using other types of machines.
Type One Energy and Thea Energy are working on stellarators, which are similar to tokamaks but twisted and complexly rippled, like a doughnut as imagined by Salvador Dali. Realta Fusion is building a reactor that the company’s co-founder, Cary Forest, calls “Tootsie Roll shaped”: a cylinder with magnets at both ends.
In an office park near Seattle, Zap Energy is making fusion devices in which filaments of plasma are, yes, zapped with electricity. Less than a mile away, Helion Energy is working on a fusion machine that shoots two rings of plasma at each other. Helion aims to generate electricity for Microsoft in 2028.
What worries researchers is how much some fusion startups are promising, and how soon. Even if pilot plants are successful, there’s still more to do before those will be ready to meet a serious share of the globe’s electricity needs, said Steven Cowley, director of the Princeton Plasma Physics Laboratory.