By Alex Kimani • Scientists have been working on nuclear fusion technology since the 1950s • The latest wave of infusion of cash into fusion startups has already exceeded the $1.9 billion in total that was previously announced Theoretically, two lone nuclear reactors running on small pellets could power the entire planet, safely and cleanly. That’s the promise of nuclear fusion. So, why are we still relying on fossil fuels? What’s stopping us from building these reactors everywhere? After all, scientists have been working on nuclear fusion technology since the 1950s and have always been optimistic that the final breakthrough is not far away. Yet, milestones have fallen time and again and now the running joke is that a practical nuclear fusion power plant could still be decades away. Well, several startups have been setting up shop to battle the kinky laws of physics that have so far prevented nuclear fusion from becoming a practical source of energy on our planet. But none has managed to inspire as much investor enthusiasm as Commonwealth Fusion Systems. The Massachusetts-based fusion startup has just snagged more than $1.8 billion in the largest private investment for nuclear fusion yet from a plethora of big-name investors, including Microsoft Corp. (NASDAQ:MSFT) co-founder Bill Gates, George Soros via his Soros Fund Management LLC and venture capitalist John Doerr. Commonwealth Fusion System is in good company. On Nov. 5, Helion Energy announced that it had raised $500 million in its latest fundraising round, making it the second-largest-ever single fundraising round for a private fusion firm. Helion has a chance to surpass Commonwealth Fusion System since its latest round of funding includes an additional $1.7 billion tied to certain performance milestones. Meanwhile, Canada’s General Fusion this week closed a $130 million fundraising round that was oversubscribed, the company’s Chief Executive Christofer Mowry has revealed. General Fusion plans to launch a larger fundraising effort next year. The latest wave of infusion of cash into fusion startups has already exceeded the $1.9 billion in total that was previously announced, according to data tracked by the Fusion Industry Association and the U.K. Atomic Energy Authority. “It’s a sign of the industry growing up,” Mr. Mowry has told the Wall Street Journal. Various fusion companies are pursuing different designs for fusion reactors, though the majority rely on fusion that takes place in plasma, a hot charged gas. Back in September, Commonwealth Fusion successfully tested the most powerful fusion magnet of its kind on Earth that would hold and compress the plasma. Commonwealth Fusion Systems is collaborating with MIT to build their fusion reactor. The team has planned a fusion experiment they have dubbed called Sparc, which is about 1/65th the volume of the International Thermonuclear Experimental Reactor (ITER). The experimental reactor will generate about 100MW of heat energy in pulses of about 10 seconds–bursts big enough to power a small city. The team anticipates that the output will be more than twice the power used to heat the plasma, thus overcoming the biggest technical hurdle in the field: positive net energy from fusion. The Sparc team has set an ambitious target to have the reactor running in about 15 years. But why have scientists so far failed at replicating a natural process that powers the stars in our universe? Extreme Challenge Turns out that the conditions necessary for nuclear fusion to take place present an extreme challenge for us earthlings. Fusion works on the basic concept of forging lighter elements into heavier ones. When two hydrogen atoms are smashed together hard enough, they fuse to form helium. The new atom is less massive than the sum of its parts, with the balance converted to energy in the E=MC2 mass-energy equivalence. Ok, that’s a bit simplistic since hydrogen atoms do not fuse together directly but rather in a multi-step reaction. Anyway, the long and short of it is that nuclear fusion produces net energy only at extreme temperatures–in the order of hundreds of millions of degrees celsius. That’s hotter than the sun’s core, and far too hot for any known material on earth to withstand. To get around this quagmire, scientists use powerful magnetic fields to contain the hot plasma and prevent it from coming into contact with the walls of the nuclear reactor. That consumes insane amounts of energy. Stars have it easy in this regard because their immense mass and powerful gravitational fields hold everything together. For instance, the sun is 333,000 times the mass of the Earth, with gravity about 27.9 times that of Earth. Unfortunately, every fusion experiment so far has been energy negative, taking in more energy than it generates, thus making it useless as a form of electricity generation. Getting the initial fusion reaction is not a problem–keeping it going is, not to mention that building nuclear reactors takes some extremely sophisticated feats of engineering, and the last word has not been said. International Megaproject But now, scientists are confident that they are close to building a nuclear reactor that will produce more energy than it consumes. The Saint-Paul-les-Durance, France-based upcoming International Thermonuclear Experimental Reactor (ITER) is the world’s largest fusion reaction facility that aims to develop commercially viable fusion reactors. Funded by six nations, including the US, Russia, China, Japan, South Korea, and India, ITER plans to build the world’s largest tokamak fusion device, a donut-shaped cage that will produce 500 ME of thermal fusion energy. The device will cost ~$24 billion, with a delivery date set at 2035. The giant machine–the biggest fusion machine ever built– will weigh in at an impressive 23,000 tonnes and will be housed in a building 60 meters high. So, what’s different this time around? Scientists have successfully developed a new superconducting material–essentially a steel tape coated with yttrium-barium-copper oxide, or YBCO, which allows them to build smaller and more powerful magnets. This lowers the energy required to get the fusion reaction off the ground. According to Fusion for Energy–the EU’s joint undertaking for ITER–18 niobium-tin superconducting magnets aka toroidal field coils will be used to contain the 150 million degrees celsius plasma. The powerful magnets will generate a powerful magnetic field equal to 11.8 tesla, or a million times stronger than the earth’s magnetic field. Europe will manufacture 10 of the toroidal field coils, with Japan manufacturing nine. However, it will be another decade before a full-scale demonstration power plant will be built using lessons learned from ITER. The industrial fusion power plants will thereafter be connected to the grid. The ITER site construction is nearly 80% complete as we speak.