There are some who believe that energy gain from fusion will always be just out of reach, a mirage on the horizon that humanity is doomed to pursue forever in vain. However, the promise of limitless clean energy is difficult to ignore. It’s an elusive prize that attracts some of science and engineering’s brightest minds, not to mention vast sums of investment. But as billions are spent in the search for energy’s Holy Grail, UK startup First Light Fusion is aiming to crack the code on a shoestring, and do so within just a few short years.
In theoretical terms, the basic science behind fusion is relatively straightforward. Hydrogen isotopes (deuterium and tritium) are forced together to form helium, expelling vast amounts of neutron energy as they fuse. While the physics may be simple, creating the conditions for the reaction to occur is anything but. It’s the same process that powers stars, where enormous temperatures and pressures are at work. Replicating those conditions on Earth is a huge challenge, and one that has spawned massively complex machines such as ITER (International Thermonuclear Experimental Reactor) in France and the Wendelstein 7-X stellarator in Germany.
Those two engineering marvels use giant magnets to keep superheated hydrogen plasma confined in reactors. However, this is not the only way to achieve fusion. Scaling down, inertial confinement creates the extreme temperatures and pressures required in a tiny pellet, forcing outer layers inward so that fusion is achieved in the very centre of a miniscule target.
“Instead of there being this big external force of these huge magnets which are holding the plasma together, for inertial fusion there’s not any external force holding the plasma together,” explained Nicholas Hawker, co-founder and CTO of First Light Fusion.
“It’s held together by its own inertia. So, it just can’t get out of its own way fast enough. If you imagine the bit of plasma in the middle, it can’t release its pressure until the bit next to it has released its pressure, and that can’t be released until the one on the outside has.”
The very centre of the pellet remains confined for just long enough that the temperature, pressure and density create the requisite conditions for fusion. Enormous amounts of energy are focused on a tiny target, usually in the form of a high-powered laser. This is the method used by the National Ignition Facility (NIF) in California, the world’s leading exponent of inertial confinement. First Light is taking a slightly different route, however, using hypervelocity projectiles to collapse targets in very specific ways.
In comparison with the vastly complex machines required for magnetic fusion, First Light’s equipment is relatively simple. Its current experiments use two-stage gas guns and electromagnetic propulsion to achieve projectile speeds of around 8 kilometres per second. At its Oxford HQ, the company is working on Machine 3, a high-voltage pulsed power device that will deliver the equivalent of around 500 lightning strikes. Similar to a railgun, it will use electromagnetism to fire projectiles at around 20km/s.
“The cost per joule of energy is one of the most critical elements for fusion, and using Machine 3 to launch the projectile is 1,000 times cheaper, per joule of energy, than using a laser,” said Hawker.
While the engineering is certainly impressive, the real complexity – and the key intellectual property – comes in the form of First Light’s advanced fuel targets, designed to maximise fusion efficiency. Inspiration for the confinement process came courtesy of the pistol shrimp, a crustacean that clicks its claw to produce a shockwave which stuns its prey and causes the surrounding water to cavitate. The air and vapour inside these cavities is heated as they implode, causing a plasma to form. Apart from supernovas, it’s the only known example of inertial confinement in the universe.
“This was the starting point for my PhD, to take this phenomena, boil it down and understand it,” said Hawker, who completed his doctorate at Oxford in 2012.
The pistol shrimp’s shockwaves are replicated at First Light using hypervelocity projectiles, with the geometries inside the target dictating how the cavities collapse. As the science and understanding of the target design improves, so too will the efficiency of the reaction.
“The complexity is in the target,” said Hawker. “We try to keep the machines simple and finesse the target with a very high-quality understanding of the physics and dynamics of what’s happening inside that target.”
“By changing this target design and having this idea of the projectile, potentially we get to a much simpler, much cheaper, technology. The whole point of First Light right now is to find the target design that actually is going to work.”
During a presentation at the company HQ, Hawker narrated an animation of the sole target design made public so far. Instead of a single cavity, the animation showed three, with two larger cavities directing energy into a smaller one as they collapsed into it, encouraging higher temperatures to be produced. Using advanced hydrodynamic simulation, the company is able to iterate target designs extremely quickly. This agile approach – taking as little as six weeks in some case – is where its competitive advantage comes in, according to Hawker.
“We did 17 products last year on advanced target designs, so it gets more and more painful that we can only show one publicly,” he said.
“Our vision for the business is that we keep working on the target design. It’s where the trade secret is. It’s the most valuable part of the IP. And we think it’s something that a startup can actually be world-leading at. We have a rapid iteration cycle, agile team… and we think this is an advantage that we can defend.”
Sir David King, former chief scientific advisor to the government, is the most recent addition to that team, joining in April 2018. The advisory board also includes Nobel Prize-winning physicist Steven Chu, with further pedigree coming in the shape of COO Gianluca Pisanello, an F1 veteran of 14 years and former chief engineer of Manor Racing.
Having recently secured £23m in funding, the company is well on its way to getting Machine 3 up and running, hoping to have it commissioned by the end of the year. First fusion is planned for 2019, with energy gain – the promised land of fusion – tentatively targeted for 2024.
If gain can be achieved, the plan is to partner with third parties with the engineering capability to develop power plants, ideally in the 200-300MW range. But rather than replace wind and solar, Hawker sees fusion working in tandem with renewables, more likely to replace the gas-fired plants that currently provide flexible baseload.
“What fusion can deliver is baseload power,” he said. “And what we think our technology is going to be able to do is address a need for flexible baseload. If you have existing nuclear, basically it’s always on, and you might not want it to be always on. You would rather it flexed in response to what the solar output is.”
“We’re not saying we don’t need renewables, that we don’t need solar and wind. We do. We should be building all of that. But energy is not generated from a single technology.”