5 Big Ideas for Making Fusion Power a Reality

Startups, universities, and major companies are vying to commercialize a nuclear fusion reactor

16 min read
General Fusion’s magnetized target reactor.

Fusion Vortex: General Fusion's magnetized target reactor injects pulses of plasma into a sphere filled with swirling molten lead and lithium.

Photo: General Fusion

The joke has been around almost as long as the dream: Nuclear fusion energy is 30 years away...and always will be. But now, more than 80 years after Australian physicist Mark Oliphant first observed deuterium atoms fusing and releasing dollops of energy, it may finally be time to update the punch line.

Over the past several years, more than two dozen research groups—impressively staffed and well-funded startups, university programs, and corporate projects—have achieved eye-opening advances in controlled nuclear fusion. They're building fusion reactors based on radically different designs that challenge the two mainstream approaches, which use either a huge, doughnut-shaped magnetic vessel called a tokamak or enormously powerful lasers.

What's more, some of these groups are predicting significant fusion milestones within the next five years, including reaching the breakeven point at which the energy produced surpasses the energy used to spark the reaction. That's shockingly soon, considering that the mainstream projects pursuing the conventional tokamak and laser-based approaches have been laboring for decades and spent billions of dollars without achieving breakeven.

In Cambridge, Mass., MIT-affiliated researchers at Commonwealth Fusion Systems say their latest reactor design is on track to exceed breakeven by 2025. In the United Kingdom, a University of Oxford spin-off called First Light Fusion claims it will demonstrate breakeven in 2024. And in Southern California, the startup TAE Technologies has issued a breathtakingly ambitious five-year timeline for commercialization of its fusion reactor.

Irrational exuberance? Maybe. Fusion research is among the most costly of endeavors, depending on high inflows of cash just to pay a lab's electricity bills. In the pursuit of funding, the temptation to overstate future achievements is strong. And past expectations of impending breakthroughs have repeatedly been dashed. What's changed now is that advances in high-speed computing, materials science, and modeling and simulation are helping to topple once-recalcitrant technical hurdles, and significant amounts of money are flowing into the field.

Some of the new fusion projects are putting the newest generation of supercomputers to work to better understand and tweak the behavior of the ultrahigh-temperature plasma in which hydrogen nuclei fuse to form helium. Others have reopened promising lines of inquiry that were shelved decades ago. Still others are exploiting new superconductors or hybridizing the mainstream concepts.

Despite their powerful tools and creative approaches, many of these new ventures will fail. But if just one succeeds in building a reactor capable of producing electricity economically, it could fundamentally transform the course of human civilization. In a fusion reaction, a single gram of the hydrogen isotopes that are most commonly used could theoretically yield the same energy as 11 metric tons of coal, with helium as the only lasting by-product.

As climate change accelerates and demand for electricity soars, nuclear fusion promises a zero-carbon, low-waste baseload source of power, one that is relatively clean and comes with no risk of meltdowns or weaponization. This tantalizing possibility has kept the fusion dream alive for decades. Could one of these scrappy startups finally succeed in making fusion a practical reality?

1. Magnetic-Confinement Fusion (MCF)

Illustration showing powerful electromagnetic fields confine and heat plasma inside a doughnut-shaped reactor. The Big Idea: Powerful electromagnetic fields confine and heat plasma inside a doughnut-shaped reactor called a tokamak, a Russian acronym for “toroidal chamber with axial magnetic field." Since the 1960s, more than 200 functional tokamaks have been built, and the plasma physics fundamentals are well established. The most ambitious of these is the US $25 billion ITER, now under construction in southern France. Reality Check: Scientists are a long way from achieving a self-sustaining reaction, and from preventing neutron activation from destroying the reactor's walls. Projects to Watch: Commonwealth Fusion Systems, Tokamak Energy Illustration: Chris Philpot

Not so long ago, the outlook for fusion power was pretty bleak, with two of the biggest projects seemingly stalled. In 2016, the U.S. Department of Energy admitted that its US $3.5 billion National Ignition Facility (NIF) had failed to meet its goal of using lasers to “ignite" a self-sustaining fusion reaction. A DOE report suggested [PDF] that NIF's research should shift from investigating laser-sparked ignition to determining whether such ignition is even possible.

The same year, the U.S. and several other governments began debating whether to pull their support from the International Thermonuclear Experimental Reactor (ITER). First proposed in 1985 and now under construction in southern France, ITER is the world's biggest fusion experiment. It is a type of tokamak, which uses magnetic forces to confine and isolate the ferociously hot, energetic plasma needed to initiate and sustain fusion. But the project has been plagued by delays and cost overruns that have quintupled its original $5 billion price tag and pushed its projected completion date to 2035. (And even if it makes that date, it could be decades after that before commercial plants based on the design are in operation.) The setbacks and enormous expense of NIF and ITER had the effect of draining not just money but also enthusiasm from the field.

Even as the government-backed megaprojects foundered, alternative fusion-energy research began to gain momentum. The hope of those pursuing these new efforts is that their novel and smaller-scale approaches can accelerate past the decades-long incremental slog. Investors are finally taking notice and pouring money into the field. Over the past five years, private capitalists have injected about $1.5 billion into small-scale fusion-energy companies. Among those who have made significant bets on fusion are Amazon's Jeff Bezos, Microsoft's Bill Gates, and venture capitalist Peter Thiel. A few major corporations, including Lockheed Martin, have launched their own small-fusion projects.

Jesse Treu, a Ph.D. physicist who spent much of his career investing in biotech and med-tech startups, says he realized in 2016 that “wonderful things were starting to happen in fusion energy, but funding wasn't catching up. It's clear that private equity and venture capital are part of the solution to develop this technology, which is clearly the best energy answer for the planet." He cofounded the Stellar Energy Foundation to connect fusion researchers with funding sources and to provide support and advocacy.

And public money has started to follow private: U.S. Department of Energy grant makers, who for decades funneled most nondefense fusion allocations to ITER, are now channeling some funding to projects at the fringes of mainstream research. The federal budget includes a $107 million increase for fusion projects in fiscal year 2020, including a research partnership program that allows small companies to conduct major experiments at the DOE's national laboratories.

The U.S. government's renewed interest stems in part from a perceived need to keep up with China, which recently restarted its fusion-energy program after a three-year moratorium. The Chinese government plans to switch on a new fusion reactor in Sichuan province this year. Meanwhile, the Chinese energy company ENN Energy Holdings has been investing in research programs abroad and is building a duplicate of Princeton Fusion Systems' compact reactor in central China, with help from top U.S. scientists.

“Now that it's looking like China will gobble up every idea the U.S. has failed to fund," says Matthew J. Moynihan, a nuclear engineer and fusion consultant to investors, “that's serving as a wake-up for the U.S. government."

2. Inertial-Confinement Fusion (ICF)

img The Big Idea: Powerful pulsed laser or ion beams (or other methods) compress a small fuel pellet to extremely high densities, and the resulting shock wave heats the plasma before it has time to dissipate. Reality Check: Forces exerted on the fuel pellet result in laser-plasma instabilities that produce high-energy electrons, which heat and scatter much of the fuel before it can fuse. In addition, the high cost and complexity of the laser drivers may make traditional approaches to ICF unsuitable for energy production. Projects to Watch: First Light Fusion, General Atomics Illustration: Chris Philpot

For all this activity and investment, fusion power remains as tough a problem as ever.

Unlike nuclear fission, in which a large, unstable nucleus is split into smaller elements, a fusion reaction occurs when the nuclei of a lightweight element, typically hydrogen, collide with enough force to fuse and form a heavier element. In the process, some of the mass is released and converted into energy, as laid out in Albert Einstein's famous formula: E = mc2.

There's an abundance of fusion energy in our universe—the sun and other stable stars are powered by thermonuclear fusion—but the task of triggering and controlling a self-sustaining fusion reaction and harnessing its power is arguably the most difficult engineering challenge humans have ever attempted.

To fuse hydrogen nuclei, earthbound reactor designers need to find ways to overcome the positively charged ions' mutual repulsion—the Coulomb force—and get them close enough to bind via what's known as the strong nuclear force. Most methods involve temperatures that are so high—several orders of magnitude hotter than the sun's core temperature of 15 million °C—that matter can exist only in the plasma state, in which electrons break free of their atomic nuclei and circulate freely in gaslike clouds.

But a high-energy-density plasma is notoriously unstable and difficult to control. It wriggles and writhes and attempts to break free, migrating to the edges of the field that contains it, where it quickly cools and dissipates. Most of the challenges surrounding fusion energy center around plasma: how to heat it, how to contain it, how to shape it and control it. The two mainstream approaches are magnetic confinement and inertial confinement. Magnetic-confinement reactors such as ITER attempt to hold the plasma steady within a tokamak, by means of powerful magnetic fields. Inertial-confinement approaches, such as NIF's, generally use lasers to compress and implode the plasma so quickly that it's held in place long enough for the reaction to get going.

Key Fusion Energy Milestones

  • 1920 British astronomer Arthur Eddington theorizes that the sun and other stars are powered by the fusion of hydrogen atoms. 1934 Australian physicist Mark Oliphant observes atoms fusing and emitting energy in his University of Cambridge laboratory. 1958 Los Alamos researchers demonstrate the first controlled thermonuclear fusion. 1958 The first tokamak, the Soviet Union's T-1, begins operation. 1974 KMS Fusion, a private-sector company, fires an array of lasers at a deuterium-tritium pellet, achieving the first successful laser-induced fusion. 1985 Mikhail Gorbachev and Ronald Reagan agree to a joint collaboration on fusion research, which leads to the ITER experiment. 1995 Princeton Plasma Physics Laboratory's tokamak achieves a record plasma temperature of 510 million °C. 1997 The Joint European Torus (JET) reactor in England outputs 16 megawatts of fusion power, still the world record. 2013 Construction begins on ITER, in southern France. 2013 National Ignition Facility (NIF) implosion yields more energy than the energy absorbed by the fuel. 2019 Construction of ITER is two-thirds complete. It is expected to produce 10 times the input energy.

Scientists have long thought that bigger is better when it comes to creating stable and energy-dense plasma fields. But with recent advances in supercomputing and complex modeling, researchers are unraveling more of the mysteries underlying plasma behavior and developing new tricks for handling it without huge, complex machinery.

Among the researchers at the forefront of this work is physicist C. Wendell Horton Jr. of the University of Texas Institute of Fusion Studies. He uses the university's Stampede supercomputer to build simulations of plasma flow and turbulence inside magnetic-confinement reactors. “We're making calculations that were impossible just a few years ago and modeling data about plasma in three dimensions and in time," Horton says. “Now we can see what's happening with much more nuance and detail than we would get with analytic theories and even the most advanced probes and diagnostic measurements. That's giving us a more holistic picture of what's needed to improve reactor design."

Horton's findings have informed the design of large-scale experiments such as ITER, as well as small-scale projects. “The problem with ITER is that no matter how well they get the plasma to behave, they haven't figured out how to get the reaction to self-sustain," he says. “It's still going to burn out in a matter of minutes, and that's obviously not solving the energy problem." He and other researchers believe that some of the small-scale efforts are much closer to achieving a steady-state reaction that could generate baseload electricity.

Among the most mature of the fusion startups is California-based TAE Technologies (formerly Tri Alpha Energy), which launched in 1998.

The TAE reactor is designed to make use of what's called a field-reversed configuration (FRC) to create a swirling ring of plasma that contains itself in its own magnetic field. (Princeton Fusion Systems' design is also an FRC.) Instead of using deuterium and tritium—the hydrogen-isotope blend that fuels most fusion reactors—the TAE reactor injects beams of high-energy neutral hydrogen particles into hydrogen-boron fuel, forcing a reaction that produces alpha particles (ionized helium nuclei). Heat generated in the containment vessel caused by the deposit of soft X-ray energy will be converted into electricity using a conventional thermal conversion system, which heats water into steam to drive a turbine.

Hydrogen-boron fusion is aneutronic, meaning that the primary reaction does not produce damaging neutron radiation. The drawback is that burning the fuel requires extraordinary temperatures, as high as 3 billion °C. “When you're that hot, the electrons are radiating like crazy," says William Dorland, a physics professor at the University of Maryland. “They're going to cool off the plasma faster than you can heat it." Although FRC machines seem to be less prone to plasma instabilities than some other magnetic-confinement methods, no one has yet demonstrated an FRC reactor that can create a stable plasma.

TAE cofounder and CEO Michl Binderbauer says the company's latest machine, dubbed Norman (in honor of company cofounder Norman Rostoker), is achieving “significant improvements in plasma containment and stability over the previous-generation machine." What's driving the improvements are advances in artificial intelligence and machine learning, enabled by a cutting-edge algorithm developed by Google called Optometrist. TAE adapted the algorithm in partnership with Google to analyze the plasma-behavior data and home in on the combination of variables that will create the most ideal conditions for fusion. The researchers described it in a Nature paper published in 2017.

“We're doing things we could have never done 10 years ago, and that's driving faster and faster cycles of learning," says Binderbauer.

3. Magnetized Target Fusion (MTF)

img The Big Idea: Sometimes called magneto-inertial fusion (MIF), this hybrid approach uses magnetic fields to confine a lower-density plasma (as in magnetic-confinement fusion), which is then heated and compressed using an inertial-confinement method such as lasers or pistons (as in inertial-confinement fusion). Reality Check: Scientists have yet to increase the plasma density to a working level and keep it there long enough for a significant fraction of the fuel mass to fuse. Projects to Watch: General Fusion, HyperJet Fusion, Magneto-Inertial Fusion Technologies Illustration: Chris Philpot

Advanced computing is also breathing new life into promising lines of inquiry that were abandoned years ago due to budget cuts or technical roadblocks. General Fusion, based near Vancouver, was founded by Canadian plasma physicist Michel Laberge. He quit a lucrative job developing laser printers to pursue an approach called magnetized target fusion (MTF). The company has attracted more than $200 million, including investments from Jeff Bezos and the governments of Canada and Malaysia.

General Fusion's design combines features of magnetic-confinement and inertial-confinement fusion. It injects pulses of magnetically confined plasma fuel into a sphere filled with a vortex of molten lead and lithium. Pistons surrounding the reactor drive shock waves toward the center, compressing the fuel and forcing the particles into a fusion reaction. The resulting heat is absorbed in the liquid metal and used to produce steam to spin a turbine and generate electricity.

“You can think of it in some ways as the opposite of a tokamak," says Laberge. “Tokamaks work with a big plasma field that's [relatively] low density. We're trying to make a mini-size plasma that's extremely high density, by squashing it in with the shock waves. Because the field is so dense and small, we only need to keep it together for a millisecond for it to react."

In the 1970s, the U.S. Naval Research Laboratory experimented with a piston system to trigger nuclear fusion. Those experiments failed, due in large part to an inability to precisely control the timing of the shock waves. Laberge's team has developed advanced algorithms and highly precise control systems to fine-tune the speed and timing of the shock waves and compression.

“In those experiments in the 1970s, the problem was symmetry," says Laberge. “We've now achieved the accuracy and force we need, so that part's solved."

4. Field-Reversed Configuration (FRC)

img The Big Idea: An FRC reactor contains plasma in its own magnetic field by inducing a toroidal electric current inside a cylindrical plasma. Compared to the direction of an externally applied magnetic field, the axial field inside the reactor is reversed by eddy currents in the plasma. TAE Technologies' reactor (pictured) uses plasma guns to accelerate two plasmas into each other and then heats them with particle beams. Reality Check: Although FRC machines are less prone to instabilities than are some other magnetic-confinement methods, no lab has yet demonstrated a working FRC reactor that can create a sufficiently dense and stable plasma. Projects to Watch: Helion Energy, Princeton Fusion Systems, TAE Technologies Illustration: Chris Philpot

Using liquid metal could solve another of fusion energy's primary challenges: Neutron radiation erodes a reactor's walls, which must be replaced frequently and disposed of as low-level radioactive waste. The liquid metal protects the solid outer wall from damage. There's some irradiation of the liquid metal, but there's no need to regularly replace it, and so the reactor doesn't produce a steady stream of low-level waste.

General Fusion's newest reactor, which generated plasma for the first time in late 2018, is the centerpiece of a facility that Laberge says will demonstrate an end-to-end capability to produce electricity from nuclear fusion. “Now that we've successfully created a stable, long-lived plasma, we can see that we have a viable path toward having the plasma generate more energy than it consumes," he says. “In terms of commercialization, our timeline is now a matter of years, not decades."

Virginia-based HyperJet Fusion Corp. has an approach similar to General Fusion's, but instead of pistons, some 600 plasma guns fire jets of plasma into the reactor. The merging of the jets forms a plasma shell, or liner, which then implodes and ignites a magnetized target plasma. The system doesn't need a heating system to bring the fuel to fusion temperatures, says HyperJet CEO and chief scientist F. Douglas Witherspoon. “The imploding plasma liner contains the target plasma and provides the energy to elevate the temperature to fusion conditions. And because we're using a much higher-density plasma than a magnetic-confinement system would, it reduces the size of the fusing plasma from meter scale to centimeter scale."

Witherspoon says the advantage of the HyperJet approach over tokamaks is that it doesn't require expensive superconducting magnets to generate the enormous magnetic fields needed to confine the fusion-burning plasma.

Tokamaks themselves are also getting a reboot, thanks to the use of different superconducting materials that could make magnetic confinement more viable. MIT spin-off Commonwealth Fusion Systems is employing yttrium-barium-copper oxide (YBCO), a high-temperature superconductor, in the magnets on its Sparc reactor.

Commonwealth cofounder Martin Greenwald, who is also the deputy director of MIT's Plasma Science and Fusion Center, calculates that the Sparc reactor's YBCO magnets will be able to generate a field of about 21 teslas at their surface and 12 T at the center of the plasma, roughly doubling the field strength of tokamak magnets made of niobium-tin. Stronger magnetic fields produce a stronger confining force on the charged particles in the plasma, improving insulation and enabling a much smaller, cheaper, and potentially better performing fusion device.

“If you can double the magnetic field and cut the size of the device in half, with identical performance, that will be a game changer," Greenwald says.

Indeed, one advantage of the newer, small-scale fusion projects is that they can concentrate on the novel aspects of their designs, while taking advantage of decades of hard-won knowledge about the fundamentals of fusion science. As Greenwald puts it, “We think we can get to commercial deployment of fusion power plants faster by accepting the conventional physics basis developed around the ITER experiment and focusing on our collaborations between physicists and magnet engineers who have been setting records for decades."

5. Stellarator

img The Big Idea: The stellarator's spiraling ribbon shape produces high-density plasma that's symmetrical and more stable than a tokamak's, allowing the reactor to run for long periods of time. Reality Check: The stellarator's challenging geometry makes it complicated to build and extremely sensitive to imperfect conditions. Project to Watch: Wendelstein 7-X at Max Planck Institute for Plasma Physics Illustration: Chris Philpot

Some promising startups, though, aren't content to accept the conventional wisdom, and they're tackling the underlying physics of fusion in new ways. One of the more radical approaches is that of First Light Fusion. The British company intends to produce fusion using an inertial-confinement reactor design inspired by a very noisy crustacean.

The pistol shrimp's defining feature is its oversize pistol-like claw, which it uses to stun prey. After drawing back the “hammer" part of its claw, the shrimp snaps it against the opposite side of the claw, creating a rapid pressure change that produces vapor-filled voids in the water called cavitation bubbles. As these bubbles collapse, shock waves pulse through the water at 25 meters per second, enough to take out small marine animals.

“The shrimp just wants to use the pressure wave to stun its prey," says Nicholas Hawker, First Light's cofounder and CEO. “It doesn't care that as the cavity implodes, the vapor inside is compressed so forcefully that it causes plasma to form—or that it has created the Earth's only example of inertial-confinement fusion." The plasma reaches temperatures of over 4,700 °C, and it creates a 218-decibel bang.

Hawker focused on the pistol shrimp's extraordinary claw in his doctoral dissertation at the University of Oxford, and he began studying whether it might be possible to mimic and scale up the shrimp's physiology to spark a fusion reaction that could produce electricity.

After raising £25 million (about $33 million) and teaming up with international engineering group Mott MacDonald, First Light is building an ICF reactor in which the “claw" consists of a metal disk-shaped projectile and a cube with a cavity filled with deuterium-tritium fuel. The projectile's impact creates shock waves, which produce cavitation bubbles in the fuel. As the bubbles collapse, the fuel within them is compressed long enough and forcefully enough to fuse.

Hawker says First Light hopes to initiate its first fusion reaction this year and to demonstrate net energy gain by 2024. But he acknowledges that those achievements won't be enough. “Fusion energy doesn't just need to be scientifically feasible," he says. “It needs to be commercially viable."

No one believes it will be easy, but the extraordinary challenge of fusion energy—not to mention the pressing need—is part of the attraction for the many scientists and engineers who've recently been drawn to the field. And increasingly, they have the resources to finance their work.

“This notion that you hear about fusion being another 30 or 40 or 50 years away is wrong," says TAE's Binderbauer, whose company has raised more than $600 million. “We're going to see commercialization of this technology in time frames of a half decade."

Veteran fusion researchers such as Dorland and Horton tend to have a more tempered outlook. They worry that grand promises that fall short may undercut public and investor support, as has happened in the past. Any claims of commercialization within the decade “are just not true," says Dorland. “We're still a lot more than one breakthrough away from having a pathway to fusion power."

What few will argue with, though, is the dire need for nuclear fusion in the near future.

“I think it's not going too far to say that fusion is having its Kitty Hawk moment," says MIT's Greenwald. “We don't have a 747 jet, but we're flying."

This article appears in the February 2020 print issue as “5 Big Ideas for Fusion Power."

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