Nuclear Fusion
The Star in the Machine: Why Fusion Keeps Being 30 Years Away — Until Now
For seven decades, nuclear fusion has been the most tantalising promise in energy — always a generation away, always almost there — and something quietly shifted in December 2022.
The Idea
Fusion is the process that powers the sun: two light atomic nuclei — typically isotopes of hydrogen called deuterium and tritium — are forced together under extreme heat and pressure until they merge, releasing an enormous burst of energy. Unlike fission, which splits heavy atoms and produces long-lived radioactive waste, fusion's byproducts are relatively benign. The fuel is effectively inexhaustible — deuterium is extracted from seawater. The appeal is almost absurd in its scope. The hard part is containment. To fuse nuclei, you need to recreate stellar conditions — temperatures exceeding 100 million degrees Celsius, roughly six times hotter than the sun's core. Nothing solid can hold that. The leading approach uses powerful magnetic fields to suspend a plasma (a superheated gas of charged particles) in a doughnut-shaped vessel called a tokamak, keeping it from touching the walls. The challenge has always been energy balance: for most of fusion's history, every experiment has consumed far more energy than the plasma produced. The key metric is called ignition — the point where a fusion reaction generates more energy than was delivered to the fuel itself. For decades, no experiment reached it. The scientific consensus treated it as a real but stubbornly distant threshold. What changed is that two separate approaches — one government-funded, one private — crossed or approached that line within roughly a year of each other, suggesting the barrier is now an engineering problem rather than a physics mystery.
In the World
On December 5, 2022, scientists at the National Ignition Facility in Livermore, California, fired 192 laser beams at a small gold cylinder barely larger than a pencil eraser. Inside was a frozen pellet of deuterium-tritium fuel. The lasers delivered 2.05 megajoules of energy. The fusion reaction released 3.15 megajoules — the first time in history that a fusion experiment produced more energy from the fuel than the lasers deposited into it. Ignition, achieved. The caveat matters: the laser system itself consumed around 300 megajoules to fire those beams. So the overall energy equation still ran deeply negative. But that is an engineering constraint, not a physics one. The Livermore team demonstrated that the fundamental process works as theorised — that a small enough target, compressed precisely enough, will ignite and burn. Meanwhile, a private company called Commonwealth Fusion Systems, spun out of MIT, demonstrated a new class of high-temperature superconducting magnet in 2021 — one powerful enough to make a commercially viable tokamak physically compact rather than stadium-sized. Their SPARC reactor, under construction in Massachusetts, is designed to produce ten times the energy it consumes. The company has attracted hundreds of millions in investment, and several other well-funded private ventures — TAE Technologies, Helion, Zap Energy — are pursuing alternative approaches. The once-sleepy world of fusion research now looks, for the first time, like a genuine industry.
Why It Matters
The cliché about fusion — always thirty years away — was never really about physics. It was about funding cycles, institutional inertia, and the fact that incremental progress in a decades-long project is almost impossible to communicate to politicians or investors. What's different now is the entry of private capital, which moves faster and tolerates different kinds of risk, and a genuine materials breakthrough in superconducting magnets that changes the geometry of what's possible. None of this means fusion power stations are imminent. The most optimistic credible projections put grid-connected fusion in the 2030s, and sceptics note that 'most optimistic credible' has always proven generous. But the nature of the problem has shifted. Fusion has graduated from 'will this ever work?' to 'how fast can we build it?' — and that distinction is worth holding onto the next time you read a headline that frames it as perennial disappointment. If it works at scale, it doesn't just decarbonise the grid; it removes scarcity as the constraint on energy. That is a civilisational shift, not a clean-energy upgrade.
A Question to Ponder
If abundant, near-limitless energy became real within your lifetime, what problem that currently feels fixed or inevitable would you most want to see unlocked by it?
Get a new one of these every morning.
Start learning with Thinkable