Worth a Shot

Teams at The Moonshot Factory have been exploring radical new approaches in energy for more than a decade—from smart grids, to sea fuel, to long duration energy storage. In today’s episode of The Moonshot Podcast, we reveal our latest effort in this space: Project Blixt, a moonshot to create a low-cost, simple and reliable fusion reactor. While ultimately we determined that the approach we were testing won’t work, we made some interesting discoveries that we hope will help inform future nuclear fusion and plasma research. Read on to learn more about our research and experiments.

The promise of fusion

Fusion is the process of joining lightweight atoms together. It powers all the stars, including our sun, and for nearly a century, it has held promise as a potential source of cheap, plentiful, on-demand clean energy. The primary fuel for fusion is deuterium, a special type of hydrogen that’s present in all water on earth–we have enough deuterium to power humanity’s energy needs for billions of years. Unlike nuclear fission, fusion does not produce any long-lived radioactive waste, can’t lead to a runaway melt down, and can’t be used to build weapons.

As demand for energy skyrockets, nuclear fusion is, in theory, an ideal solution. But fusion is not an easy reaction to force: squeezing hydrogen atoms together requires a combination of tremendously high pressure and temperature. Researchers have been working since the 1940s to find a stable, controlled way to fuse atoms that releases more energy than it took to make the reaction happen.

Revisiting the Z-pinch mystery

For the last few years, my team and I have been exploring whether it’s possible to create fusion energy using the Z-pinch approach. Inspired by the way energy flows through a lightning rod, the Z-pinch technique we explored involves sending a huge pulse of current through a frozen wire of hydrogen as thin as a human hair. That current does two things: first, it heats the hydrogen so much it turns into plasma, which wants to rapidly expand. And second, the current forms its own magnetic field, which squeezes down on that plasma. If those two forces could be held in balance long enough, scientists hypothesize that the plasma could reach the temperatures and pressures required to make a controlled, harvestable fusion reaction.

The nuclear fusion community mostly abandoned the Z-pinch approach decades ago, after the majority of experiments demonstrated the plasma was unstable, falling apart before it could reach fusion relevant conditions. However, a number of experiments run by researchers at Los Alamos National Lab and the Naval Research Lab back in the 80s and 90s showed curious outcomes: the plasma appeared to remain stable for a much longer period of time than predicted, staying confined like a wire or a column. But these anomalous results were not repeated by later experiments, and this discrepancy has remained a mystery in the field of fusion research for nearly four decades.

When our team came across this work, we realized that advances in diagnostic tools meant that this approach could be revisited, and possibly understood, for a tiny fraction of the cost of exploring most other fusion techniques. Since the initial Z-pinch research took place, electronic measurement equipment is much faster, cameras can take more detailed imagery of plasma at incredibly high speeds, and we have a range of simulation and computation tools that simply didn’t exist back then. So we decided to team up with John Sethian and Bertie Robson, the scientists who conducted some of the original frozen fiber Z-pinch work, to see if we could replicate their anomalous experiments using today’s advanced technologies and get to the bottom of those lingering questions.

The reward-risk ratio of moonshots

When taking moonshots at X, we aim for pursuits that have a high reward-to-risk ratio, and where we can learn quickly at a reasonable cost. From the start, we recognized that exploring the Z-pinch approach to creating affordable, scalable nuclear fusion was a scientific risk—data and theory to support this hypothesis was limited—but the upside for humanity would be very high.

What’s more, due to the overall simplicity of the design, the risk on the engineering side was low. If we could find a set of conditions where the plasma stayed stable, the subsequent engineering work would have been much easier than many other approaches being explored around the world, which meant we’d be able to scale up to power plants relatively quickly and inexpensively. We also knew we could pursue this long-shot idea at low cost with just a handful of people.

Under the guidance of seasoned scientific advisors from national labs and universities, our team first set out to disprove the Z-pinch hypothesis using simulations. When the initial simulations were inconclusive, it was time to test the hypothesis in the real world. We engineered and constructed a setup for conducting experiments inside a 64,000 square foot airplane hangar in Alameda, California. The team took great care in the design of this system to ensure we could operate safely without risk to people or the environment—monitoring later verified that our year of experiments had the same exposure risk as eating a few bananas or flying in an airplane for about ten minutes.

The extreme temperatures, speeds, and forces of the materials traveling through our equipment were both staggering and humbling. The hydrogen wire started at 4.5 degrees Kelvin in its solid state (roughly -452 degrees Fahrenheit), the electric pulse sent through it reached hundreds of thousands of amps and hundreds of thousands of volts, the plasma ultimately heated to several times hotter than the surface of the sun, the system of over 12,000 components had to be controlled and data measured down to nanosecond resolution (one-billionth of a second), and each experiment took place in the time it takes light to travel less than 100 feet.

Our machine enabled us to ask and answer key questions about the frozen-fiber Z-pinch. We were able to take 175 successful plasma shots with good data, and conducted roughly 800 experiments, which ultimately demonstrated that this approach would be untenable for scaling to a nuclear fusion power plant. Our modern tools revealed that the plasma became unstable at a micro scale early on, and even though the initial frozen core did help stabilize things briefly, there wasn’t a path to keep the plasma confined long enough to produce net energy.

Based on our experiments, we believe that the anomalous results from the 80s and 90s were partially due to the fact that the diagnostic technologies at that time couldn’t measure instabilities at such a precise level of detail. Our experimental results also informed the simulation work, and ultimately, we were able to get a fairly close agreement between the theory and data, furthering our understanding and confidence in our decision.

Sharing what we've learned with the world

As I shared in today’s episode of The Moonshot Podcast, after running hundreds of experiments, we’ve decided to wind down. While it’s disappointing to discontinue a project, I’m very proud of this team for working on a smart longshot with passion, running efficient experiments to learn quickly, and for ending it when the data showed us there wasn’t a path forward. 

During our investigation, we observed the plasma behaving in some surprising ways that we believe the scientific community may want to understand further, so we’ll be publishing a detailed account of our research and the data from our work in the coming year. In the meantime, photography of our rig and experiments will be on display next month in Alameda at the In Plain Site Photography Festival. Please drop by if you’d like to learn more or chat with our team.