Let’s say that you’ve devoted your entire adult life to developing a carbon-free way to power a household for a year on the fuel of a single glass of water, and that you’ve had moments, even years, when you were pretty sure you would succeed. Let’s say also that you’re not crazy. This is a reasonable description of many of the physicists working in the field of nuclear fusion. In order to reach this goal, they had to find a way to heat matter to temperatures hotter than the center of the sun, so hot that atoms essentially melt into a cloud of charged particles known as plasma; they did that. They had to conceive of and build containers that could hold those plasmas; they did that, too, by making “bottles” out of strong magnetic fields. When those magnetic bottles leaked—because, as one scientist explained, trying to contain plasma in a magnetic bottle is like trying to wrap a jelly in twine—they had to devise further ingenious solutions, and, again and again, they did. Over decades, in the pursuit of nuclear fusion, scientists and engineers built giant metal doughnuts and Gehryesque twisted coils, they “pinched” plasmas with lasers, and they constructed fusion devices in garages. For thirty-six years, they have been planning and building an experimental fusion device in Provence. And yet commercially viable nuclear-fusion energy has always remained just a bit farther on. As the White Queen, in “Through the Looking Glass,” said to Alice, it is never jam today, it is always jam tomorrow.
The accelerating climate crisis makes fusion’s elusiveness more than cutely maddening. Solar energy gets more efficient and affordable each year, but it’s not continuously available, and it still relies on gas power plants for distribution. The same is true for wind power. Conventional nuclear power has extremely well-known disadvantages. Carbon capture, which is like a toothbrush for the sky, is compelling, but after you capture a teraton or two of carbon there’s nowhere to put it. All these tools figure extensively in decarbonization plans laid out by groups like the Intergovernmental Panel on Climate Change, but, according to those plans, even when combined with one another the tools are insufficient. Fusion remains the great clean-energy dream—or, depending on whom you ask, pipe dream.
Fusion, theoretically, has no scarcity issues; our planet has enough of fusion’s primary fuels, heavy hydrogen and lithium, which are found in seawater, to last thirty million years. Fusion requires no major advances in batteries, it would be available on demand, it wouldn’t cause the next Fukushima, and it wouldn’t be too pricey—if only we could figure out all the “details.” (A joke I heard is that fusion operates according to the law of the “conservation of difficulty”: when one problem is solved, a new one of equal difficulty emerges to take its place.) The details are tremendously complex, and the people who work to figure them out have for years been dealing with their own scarcities—scarcities of funding and scarcities of faith. Fusion, as of now, has no place in the Green New Deal.
In 1976, the U.S. Energy Research and Development Administration published a study predicting how quickly nuclear fusion could become a reality, depending on how much money was invested in the field. For around nine billion a year in today’s dollars—described as the “Maximum Effective Effort”—it projected reaching fusion energy by 1990. The scale descended to about a billion dollars a year, which the study projected would lead to “Fusion Never.” “And that’s about what’s been spent,” the British physicist Steven Cowley told me. “Pretty close to the maximum amount you could spend in order to never get there.”
“To be honest, I was feeling pretty despondent,” Dennis Whyte, the fifty-seven-year-old director of the Plasma Science and Fusion Center, at M.I.T., said. “And I was seeing that despondency in the faces of my students, too.” It was 2013, and M.I.T.’s experimental fusion device had lost its Department of Energy funding, for no clearly stated reason. The field of nuclear fusion, as a whole, was still moving forward, but agonizingly slowly. iter, an enormous fusion device being built in southern France, in an international collaboration, was progressing—the schedule is for ITER to demonstrate net fusion energy in 2035, and the majority of plasma physicists have high confidence that it will work—but Whyte knew that it wasn’t going to deliver affordable energy to the public in his lifetime, and maybe not in his students’ lifetimes, either. “ITER is scientifically interesting. But it’s not economically interesting,” Whyte said. “I almost retired.”
Whyte is a gentle giant from Saskatchewan, Canada. “If you’ve ever been to the middle of nowhere, that’s where I grew up,” he told me. His family were farmers and electricians. By the time he was in the fifth grade, he knew he wanted to be a scientist, and in the eleventh grade he wrote a term paper on that wild idea which often appeared in science fiction—near-boundless energy generated by the fusing of two atoms, as happens in stars. “I remember getting that paper back, and my teacher saying, ‘Great job, but it’s too complicated.’ ” Whyte went on to major in engineering and physics at the University of Saskatchewan; for his Ph.D., he attended a new plasma-physics program at the University of Quebec, where he worked in a government-funded fusion lab. “I thought, Great: I’ll learn French and get to work on a tokamak,” he said, referring to the large doughnut-shaped machine whose design is commonly used for fusion devices. Later, Whyte took a job at a lab in San Diego. He intended to return home eventually, but in 1997 Canada cancelled its fusion program. “I was stranded in the U.S.,” he said.
At M.I.T., Whyte teaches an engineering-design class for graduate students which he organizes each year around a different practical problem in fusion. “I’ve always wanted to expose my students not only to the science questions but also to the technology questions,” he said. In 2008, he asked his students to design a device that would pump helium but not hydrogen—in most approaches to fusion, hydrogen is the fuel, and helium is, in effect, the ash. “Helium is one of the hardest things to pump in the periodic table, because it’s so inert,” Whyte said. The class came up with several very clever ideas. None of them was successful. “We’re still working on that one,” he said.
The next year, something happened that Whyte credits with restoring his interest in fusion. “I had passed my colleague Leslie in the hall, and he was holding a bundle of what looked like the spoolings of a cassette tape,” he said. It was a relatively new material: ribbons of high-temperature superconductor. Superconductors are materials that offer little to no resistance to the flow of electricity; for this reason, they make ideally efficient electromagnets, and magnets are the key component in tokamaks. A high-temperature superconductor—well, it opened up new possibilities, in the way that the vulcanization of rubber opened up possibilities in the mid-nineteenth century. The superconductor material that Whyte’s colleague was holding could in theory make a much more effective magnet than had ever existed, resulting in a significantly smaller and cheaper fusion device. “Every time you double a magnetic field, the volume of the plasma required to produce the same amount of power goes down by a factor of sixteen,” Whyte explained. Fusion happens when a contained plasma is heated to more than a hundred million degrees. Whyte asked his class to use this new material to design a compact fusion power plant of at least five hundred megawatts, enough to power a small city: “I was not sure what we would find with H.T.S., but I knew it would be innovative.”
The physicists Bob Mumgaard, Dan Brunner, and Zach Hartwig were in that class. The power plant that they came up with was in most respects familiar. At its center would be a doughnut-shaped tokamak, not unlike the type that Whyte had worked with as a graduate student. They named their design Vulcan. In the next iteration of the class, those ideas evolved into a design called ARC, for “affordable, robust, and compact.” (This also happens to be the name of the personal fusion device of the billionaire industrialist Tony Stark, in the “Iron Man” movies.) ARC would use an ordinary salt to translate its heat onto an electrical grid. It would be modular, for easy maintenance. It would not be able to recycle its own fuel. It was a “good enough” machine. But the use of H.T.S. magnets made it about the size of a conventional power plant—a tenth the size of ITER.
Physicists from both classes later formed a group that modified the arc design. The new model was two-thirds the size and intended to be ready as soon as possible—SPARC. SPARC would be the prototype that demonstrated the concept; ARC would be a long-lasting power plant capable of delivering affordable energy to the grid.
There were real reasons for skepticism. H.T.S. is fragile—it remained to be seen if it could even be made into a hardy magnet, and, if it could, how well that magnet would endure bombardment by charged particles. Plus, H.T.S. was not yet commercially available at sufficient scale and performance. “But those were engineering barriers, not scientific barriers,” Whyte said. “That class really changed my mind about where we were in fusion.”
Fusion scientists often speak of waiting for a “Kitty Hawk moment,” though they argue about what would constitute one. Only in retrospect do we view the Wright brothers’ Flyer as the essential breakthrough in manned flight. Hot-air balloons had already achieved flight, of a kind; gliders were around, too, though they couldn’t take off or land without a catapult or a leap. One of the Wright brothers’ first manned flights lasted less than a minute—was that flight? An A.P. reporter said, of that event, “Fifty-seven seconds, hey? If it had been fifty-seven minutes, then it might have been a news item.”
Our sun is a fusion engine. So are all the stars.
But we discovered that fusion powered the stars only about a hundred years ago, when the British physicist Arthur Eddington put together two pieces of knowledge into what was seen at the time as a wild surmise. The facts he combined were that the sun is made up mostly of hydrogen, with some helium, and that E=mc2.
Eddington noticed that four hydrogen atoms weigh a tiny bit more than one helium atom. If four hydrogen nuclei somehow fuse together, in a series of steps, and form helium, then a little bit of mass must be “lost” in the process. And if one takes seriously that most famous of equations, then that little bit of mass becomes a lot of energy—as much energy as that amount of mass multiplied by the speed of light, squared. To give a sense of this ratio: If you converted a baseball into pure energy, you could power New York City for about two weeks. Maybe that process—hydrogen crashing into hydrogen and forming helium, giving off an extraordinary amount of energy in the process—was how the sun and all the stars burned so bright and so long. Eddington, in a paper laying out this theory, closed with an unusual take on the story of Daedalus and his son Icarus. Eddington argued in defense of Icarus, saying it was better to fly too high, and in doing so see where a scientific idea begins to fail, than it was to be cautious and not try to fly high at all.
When most people think of nuclear energy, they are thinking not of fusion but of fission. Fission is when an atom—most commonly uranium or plutonium—breaks in two. Fission generates waste that remains radioactive for tens of thousands of years; in contrast, the little bit of waste that fusion generates remains radioactive for only a few decades. Fission is pretty powerful, as evidenced by atomic bombs; fusion is much, much more powerful. (In 1952, a fusion bomb, known as the H-bomb, was tested, though it has never been used in warfare; it worked by using a fission bomb to set off a giant uncontrolled fusion reaction. One of the fathers of the H-bomb, Edward Teller, an aggrieved Shakespearean villain in most tellings, had other incautious ideas, such as using fusion bombs to dig canals or make diamonds.) The process of fusion sounds dangerous to a layperson—a sun in a magnetic bottle?—but it is easier to extinguish than a match.
