Seven Nuclear Fusion Startups Making Clean Energy History

Letter from 2073: Fifty years ago, fusion energy was a ludicrous pipe dream. Now it powers everything. Dr. Tritium takes you back to the pioneers of nuclear prosperity

By Mark Bergen and Eric Roston

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Zap’s reactor uses neither lasers nor magnets, unlike those of most fusion startups. The reactor core is a long, narrow cylinder. Inside its vacuum chamber (below), an electric current strips hydrogen gas of its electrons, generating a high-energy plasma. It’s propelled downward through the chamber. The plasma cloud collapses into a column and is shot through with a current powerful enough to generate the magnetic field that confines and condenses it.

This company’s version of a tokamak looks like an apple core. It’s part of a spherical machine that uses something called a strong toroidal magnetic field—basically, a set of doughnut-shaped magnets. These magnets, working with some high-temperature superconductors, contain the plasma and harvest neutrons. The more compact device is cheaper and better at manipulating plasma than other models, Tokamak says.

Marvel is relying on a boatload of lasers. Short laser beams are stretched and compressed very quickly inside a chamber—a method called chirped pulse amplification—then shot into a reactor filled with Marvel’s fuel, a mixture of hydrogen and boron. Younger than its main rivals, Marvel hadn’t expanded beyond the lab by 2023. But the company had run more than 2,000 experiments and planned to open its first facility by the year’s end.

General built a giant, futuristic steam engine. The reaction process starts in a huge tank filled with liquid metal (lead and a little lithium) that’s spun around furiously to form a cavity. Then pistons pump in hydrogen plasma, heating it to more than 100 million degrees Celsius. The company runs tests using explosives. “Now,” says CEO Greg Twinney (below left), “we need to do this in a machine that can work repetitively—where we’re not blowing it up.” Michel Laberge (below right) is the chief science officer.

The company is working on two new machines. Da Vinci, planned for the early 2030s, is its commercial model that’s supposed to supply power to the grid. In the meantime, it’s also busy with spinoffs—a power company making EV charges go faster and last longer, and TAE Life Sciences, which puts its science to work treating complex cancers.

The renderings of this startup’s planned reactor resemble an enormous barbell (below). Tanks at either end heat up the fuel mixture, deuterium and helium-3, creating rings of plasma. These are then shot toward each other at speeds reaching a million miles an hour and compressed with magnets to spark a reaction. This method, called magneto-inertial fusion, will harness energy more efficiently than big tokamaks or steam cycles, says Scott Krisiloff, chief business officer at Helion.

Commonwealth Fusion Systems is a Massachusetts Institute of Technology spinoff. Its device started out as a project in professor Dennis Whyte’s fusion design class. It was refined in a formal paper in 2015, and Whyte became a company co-founder. CFS is building a magnetic confinement reactor. It’s a tokamak that co-founder and Chief Science Officer Brandon Sorbom describes as a doughnut-shaped magnet, with fields spiraling around its surface, like a barber’s pole wrapped into a doughnut.