Imagine a world without fossil fuels, where humans can produce an emission-less, inexhaustible, and completely renewable source of energy. This is the utopian world of fusion energy. Not only does fusion have the potential to end the threat of global warming, but it can be supplied by earth’s most plentiful fuel source: water. It produces no toxic byproducts, only helium, which as TIME writer Lev Grossman puts it, “we can use to inflate the balloons for the massive party we’re going to have if it ever works.”

Fusion energy has long been known as the “holy grail of renewable energy,” but like the Holy Grail, it is elusive. The long-standing joke about fusion is that it is thirty years away, and always will be. Although the underlying concept of generating energy through nuclear fusion has been around since the 1930s, scientists have yet to achieve a fusion reactor that can produce more power than it requires to run.

The historical difficulties in attaining a viable fusion reactor are due to the immense logistical challenges associated with fusion reactions. In his 1995 Scientific American article on fusion, Harold Furth summarizes the challenges of fusion energy. In essence, fusion reactors attempt to recreate the reaction that occurs in our sun: a superheated, extremely dense ball of plasma, inside of which hydrogen atoms fuse to become helium, releasing vast quantities of energy. Making plasma in the first place is difficult; although 99% of the matter in our universe is plasma, according to Curt Suplee in The Plasma Universe, it’s difficult to make on earth. Getting it to the point where it can undergo fusion is more difficult by an order of magnitude.

The nature of fusion reactions creates three overwhelming challenges for scientists: generating plasma that is hot and dense enough to undergo fusion, containing the wildly energetic plasma, and efficiently collecting the energy that is released during fusion. So far, the lack of a robust solution to all three of these problems has prevented fusion reactors from producing net energy.

How have scientists attempted to solve these three problems in the past? Traditional fusion energy research has been centered on the tokamak. In his paper on tokamak design optimization, Tom Luce describes their operation. Tokamaks use a doughnut-shaped chamber (more formally known as a toroid) covered in powerful electromagnets to confine the plasma. The strong magnetic field inside of the toroid accelerates the plasma through a helical path, generating the heat and pressure necessary for fusion to take place. The thermal energy that is released creates steam, which powers turbines to generate electricity.

In a report on the history of tokamaks, Alan Azizov writes that by the 1990s, fusion research in tokamaks was widespread: the T-15 tokamak in the USSR, the J-60 in Japan, TFTR in the U.S, and the JET (Joint European Torus) in Europe. In 1997, the JET Fusion Reactor returned about 65% of its total input energy through fusion, the highest efficiency recorded at the time. However, Azizov concluded that tokamaks still needed a lot of improvement if they were to reach the break-even point, let alone produce a net gain of energy.

Five years before JET achieved its record-breaking performance, in an effort to create the world’s first tokamak fusion power plant, a joint force involving the U.S, Russia, Japan, China, South Korea, India, and the European Union began designing what would be the world’s largest tokamak reactor, called ITER (International Thermonuclear Experimental Reactor) in 1992. While ITER has potential to be the first fusion reactor to produce net energy – in fact, its designers claim that it will produce ten times the power it consumes – its progress has been slow. In his TIME article on the future of fusion energy, Lev Gross argues that the magnitude of the project, combined with the bureaucracy associated with the dozen or so participating countries, is responsible for pushing back its expected operational date from 2016 to sometime in 2027. He even regards this 2027 deadline with skepticism.

It turns out that missed deadlines are a recurring theme. Another U.S. government fusion project, Lawrence Livermore Lab’s National Ignition Facility, which uses high-powered lasers to initiate fusion reactions, was delayed by five years. The construction began in 1997, was supposed to be finished by 2004, but was delayed until late 2009. It wasn’t until 2012, fifteen years after the project’s start, that the facility was fully operational for testing.

The exorbitant cost of these government fusion projects is even more disheartening. The National Ignition Facility cost $5 billion, twice its original proposed budget. To put things in perspective, that’s more than the $4.4 billion construction cost of the Large Hadron Collider. ITER’s cost is even more appalling. According to Grossman, ITER’s budget has risen from $5 billion to $20 billion since 1992. The National Ignition Facility and ITER aren’t the only examples; these kinds of huge costs and missed deadlines have become characteristic of nearly all large-scale government fusion research.

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Today, however, the whole paradigm of fusion reactors is shifting, as startups are taking fusion research into their own hands.

In 2011, Lockheed Martin’s “Skunk Works” released plans for a revolutionary Compact Fusion Reactor called “T4.” Dr. Thomas McGuire, who holds a PhD in Aeronautical Engineering from MIT, leads the fusion reactor’s team. In an interview with Guy Norris of Aviation Week, McGuire explains that “I studied [fusion] in graduate school where, under a NASA study, I was charged with how we could get to Mars quickly.” While conducting his research as a graduate student, McGuire realized that there was very little literature on the use of fusion energy in space missions, so he decided to change that. Today, his research efforts have grown into the T4 reactor at Skunk Works.

In contrast to ITER, which will be over one hundred feet tall, and cost at least $20 billion, McGuire and his team aim to produce a 23’x43’ unit that will be transportable, cheap, and fully operational in less than 10 years. Like ITER, the T4 reactor is designed to achieve a ten-fold energy return, but at a fraction of ITER’s size and cost.

The T4 team claims that their reactor will be viable due to its novel design: it moves beyond the design constraints of traditional tokamaks and has a radically different approach to magnetic confinement of the plasma. The reaction chamber is a sphere, inside of which superconducting coils generate a magnetic field that compresses the plasma in the chamber’s center. This method of confinement eliminates the problem of most tokamaks, instability, which is caused by rapid spinning and oscillation as plasma whirls around in a helix. The Compact Fusion Reactor exploits the plasma’s own turbulent motion in order to contain it; as plasma shifts and tries to escape confinement, its own motion causes the magnetic force exerted on it to increase. This self-stabilizing phenomenon, which is largely due to the special configuration of electromagnets around T4’s reaction chamber, drastically improves the ability of the reactor to initiate and maintain a fusion reaction.

The T4 team also claims that their fusion reactor is so energy efficient that it can run on a mere 25 kilograms of hydrogen fuel per year. Someday, it might be used to power aircraft, ships, and even spacecraft, just as McGuire envisioned when he began the project.

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Some companies haven’t completely left behind the familiar doughnut shape of the tokamak, however. In the U.K., a company called Tokamak Energy has been innovating a spherical tokamak design since the early 2000s. While the reactor is technically still a toroid, the inner core is so small that the reactor is practically spherical. Growing out of Culham Laboratory, where the JET Reactor recorded its impressive 65% energy return in 1997, Tokamak Energy has been researching and building small spherical tokamaks. According to Lee Hibbert, who published a review on spherical tokamak design, these tokamaks have a higher theoretical efficiency than their traditional toroidal counterparts.

In 2015, Tokamak Energy demonstrated that their latest spherical tokamak, called ST25, could sustain continuous plasma in the reactor for 29 hours, breaking the previous world record of 5 hours by an unprecedented margin. According to Alan Sykes, the leader of Tokamak Energy’s team, what enables their reactor to perform so efficiently for an extended period of time are high-temperature superconducting magnets, which can handle much higher electric currents than standard electromagnets. This nascent technology has allowed Tokamak Energy to reduce the size of their reactors, simply because fewer electromagnets are needed for containment. Achieving a more compact design has not only allowed Tokomak Energy’s reactor to maintain plasma for a longer period of time, but also made energy collection more efficient.

While tokamak research remains promising, some companies have chosen to abandon the concept of the tokamak altogether, exploring novel designs for fusion reactors.

One such company, Tri Alpha Energy, has been secretly developing a type of fusion reactor called the “Colliding Beam Fusion Reactor.” In 1997, its founders, Norman Rostoker, Michl W. Binderbauer, and Hendrik J. Monkhorst, released a research report on the principles behind the reactor. By 2010, they had begun testing their first reactor, called C-2. Despite earning over $10 million in funding for their project, the company kept its work hidden to protect proprietary information. Until recently, they did not even have a website. However, in 2012, Tri Alpha began to release information about their fusion research over the previous decade.

By 2015, their next generation C-2U reactor could sustain plasma at an unfathomable 10 million degrees Celsius for 5 milliseconds (for fusion reactors, this is actually considered a large timespan). For reference, our sun’s surface temperature is a mere 5,505 degrees Celsius. The only way the C-2U reactor can withstand plasma at such mind-boggling temperatures is by suspending the plasma inside of a magnetic field, so that it never comes into contact with the reactor’s walls.

There are several interesting ways in which Tri Alpha’s C-2U reactor departs from the traditional designs for fusion reactors. Rostoker and his team at Tri Alpha describe in a paper on their Colliding Beam Fusion Reactor that, while almost every other fusion reactor uses a mixture of deuterium and radioactive tritium (two isotopes of hydrogen), Tri Alpha fuels their reactor with deuterium and Boron-11. Reactions between deuterium and tritium eject tons of neutrons as a byproduct, which have a troublesome tendency to degrade materials and make them radioactive. This is why Tri Alpha uses Boron-11 instead – it is inherently more stable, and does not produce neutrons during fusion. The caveat is that Boron-11 requires higher temperatures to undergo fusion. This is why Tri Alpha had to design a reactor that could heat plasma up to 10 million degrees.

Secondly, the way the C-2U initiates fusion is radically different from the familiar tokamak. C-2U is a Colliding Beam Fusion Reactor, which creates two small rings of plasma, called plasmoids, at each end of a long chamber, then slams them together at high speeds in the middle. Interestingly, the little plasmoids don’t require giant, energy-thirsty electromagnets to keep them contained. The plasmoids naturally rotate, producing their own magnetic fields. These magnetic fields contain the plasma, mitigating some of the instability in plasma that plagues tokamaks.

Finally, the C-2U captures fusion energy much differently than its predecessors. In addition to capturing thermal energy with steam turbines, the C-2U has a unique energy-collection device called an inverse cyclotron. Fast-moving alpha particles that are produced by the fusion reaction spin through the cyclotron, inducing an electric current that can be captured and stored as power.

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Tri Alpha isn’t the only company that’s been trying to smash plasma together to create fusion. In Redmond, Washington, a company called Helion Energy is building a reactor that is conceptually similar to the C-2U. Their reactor, simply known as the “Fusion Engine,” has a long linear chamber like that of the C-2U, and it also produces fusion by slamming together little plasmoids at high speeds. However, it has an interesting twist: it’s designed to run continuously, functioning like a power plant.

Chief Science Officer John Slough, who is also a professor at the University of Washington in the Plasma Dynamics Lab, describes the theory behind the Fusion Engine in a paper published in April of 2011. In the Fusion Engine, strong electromagnets pulse once per second, accelerating two helium-deuterium plasmoids to well over one million miles per hour by the time they collide in the center of the chamber. Once the plasmoids join in the center of the reactor, electromagnets compress them another time to a temperature above one-hundred million degrees Celsius. At this point fusion occurs, and deuterium atoms from the plasmoids fuse into helium atoms. Some of the energy that is released, along with the helium atoms that are produced in the reaction, is fed back into the next cycle of the reactor a second later. Once the Fusion Engine has started up, it no longer needs an external power supply to keep it running. Helion claims that their reactor is capable of returning eight times its input power.

The team at Helion is currently seeking $35 million in funding to build a break-even prototype of their Fusion Engine in 2016. So far they’ve raised $10.9 million. If all goes to plan, after demonstrating their break-even reactor in 2016, they will begin work on a commercial reactor capable of producing 50 Megawatts of power by 2022.

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Another novel fusion-reactor concept comes from Canada-based General Fusion, which was founded in 2002 by Michel Laberge. In a TED Talk, Laberge comments that:

When I started [General Fusion] in 2002, I knew I couldn’t fight with the big labs; they had much more resources than me. I had to find a solution that was cheaper and faster. Magnetic and laser fusion reactors have shown that fusion can be done. However, as a power plant, I don’t think they are very good… The people who made these reactors focused only on the fusion reaction, and collecting the energy was just an afterthought.

Laberge and his team have built their design so that it can function as a power plant, running continuously and collecting the energy that is produced as efficiently as possible. They call their reactor a Magnetized Target Reactor. In an article analyzing the performance of Magnetized Target Reactions, Michael Lindstrom, a PhD in Applied Mathematics, explains how these kinds of reactors achieve fusion. Inside of General Fusion’s Magnetized Target Reactor, plasma is injected into a spinning vortex of molten lead and lithium, and rapidly compressed by an array of pistons surrounding the spherical reaction chamber.

220 of these pneumatically controlled pistons ram the surface of the sphere at 200 miles per hour, sending an acoustic shockwave through the mix of molten metal and plasma. Due to the rapid succession of piston punches, and their powerful shockwaves, the molten lead and plasma mixture reaches fusion conditions. As an added bonus, the molten lead absorbs a lot of the heat from the fusion reaction, protecting the steel reaction chamber and making the reactor more robust. There are no complex electromagnets involved; the fusion is driven entirely by the mechanical operation of the pistons.

There are several key advantages of General Fusion’s Magnetized Target Reactor. The high-speed movement of the pistons is powered by compressed air, which is safe, reliable, and cheap compared to the massive electric pulses needed to power the electromagnets in most tokamaks. Because the piston array in General Fusion’s reactor is driven by compressed air, the reactor can be operated at 1% the cost of competing fusion reactors, almost all of which rely on costly electromagnetic systems. Should General Fusion’s reactor work, it will be the most cost-effective fusion reactor to operate, and will make traditional tokamaks irrelevant.

Ironically, fusion reactors have seen frustratingly slow progress over the last eighty years but have the potential to change the future of our planet almost instantaneously. It is this tantalizing possibility of a breakthrough that has kept fusion research going for decade after decade.

Now, however, the quest for fusion is largely powered by necessity. Faced with the threat of global warming, and the painfully slow progress of projects like ITER, entrepreneurs are taking on the challenges of fusion themselves, with their sights set on a future of sustainable energy.

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With so many startups getting involved in fusion energy, and tackling the historical problems of fusion energy from every imaginable angle, the prospect of achieving a net energy gain from fusion reactors in the next decade has gone from doubtful to plausible. Now, the question isn’t whether or not we will attain fusion energy, but who will be the first to do it? Fusion companies claim that their reactors can do the incredible – reaching temperatures a thousand times hotter than our sun, crashing balls of plasma together at millions of miles per hour – but can they translate their claims into reality?

 

Further Reading

Furth, Harold. “Fusion.” Scientific American. 174-76 (1995). Print.

Grossman, Lev. “Startup Companies Are Rebooting the Quest for Clean Energy’s Holy Grail: Fusion.” TIME 2 Nov. 2015, 186th ed. Print.

Laberge, Michel. “How synchronized hammer strikes could generate fusion.” TED. March 2014. Lecture.

Hamilton, Tyler. “A New Approach to Fusion.” MIT Technology Review. MIT, 31 July 2009. Web. 09 Nov. 2015.

Clery, Daniel. “Secretive Fusion Company Makes Reactor Breakthrough.” Science (2015): n. pag. IAAA. Web.

Norris, Guy. “Fusion Frontier.” Aviation Week & Space Technology 176.37 (2014): 42-44. BartonPlus. Web.

Waldrop, Mitchell M. “Plasma Physics: The Fusion Upstarts.” Nature 511.7510 (2014): 398-400. BartonPlus. Web.