The world’s only fusion experiment that actually gives back more energy than it takes in is now breaking its own records. According to TechCrunch, the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory recently pushed its fusion yield—first to 5.2 megajoules, and then to 8.6 megajoules—more than doubling the energy released in its historic shot in 2022.

That original breakthrough was the first time scientists had ever achieved “ignition”—a fusion reaction that generated more energy (3.15 megajoules) than the lasers put into the fuel (2.05 megajoules).

Importantly, that achievement does not take into account the amount of energy put into the system to power the reaction—essentially, 300 megajoules of energy from the plug in the wall. Nevertheless, the accomplishment indicated the tantalizing promise of nuclear fusion as a carbon-free, essentially limitless source of energy. Jill Hruby, the under secretary for nuclear security, summed it up as “the first tentative steps towards a clean energy source that could revolutionize the world.”

Fusion isn’t new—scientists have been chasing it for nearly a century. The problem has always been scale: It generally costs way more energy to trigger a fusion reaction than what comes out of said reaction. The NIF’s achievement changed that—for a moment, humanity replicated the energy source of stars and came out ahead.

The new surge in energy yield is a large jump for the experiment, though it’s still very far off from providing a sustainable clean energy source (consider the 300 megajoules necessary to power the 2022 experiment). And that’s to say nothing of building an actual fusion energy plant, and figuring out a way to produce fusion power at scale and integrate the budding technology into the world’s power grid.

The system works via inertial confinement fusion, using 192 laser beams to compress a diamond-coated pellet the size of a peppercorn—basically giving it a tiny, star-like explosion inside a golden cylinder. The laser blast occurs inside a 10-meter-wide vacuum chamber, heating the fuel to over 100 million degrees Fahrenheit and pressures hundreds of billion of times Earth’s atmosphere. The team repeated the trick in 2023, and by the recent report, it seems the experiment’s efficiency has only improved.

Experts still see big roadblocks for inertial confinement as a practical energy source. That’s why other teams are pursuing other means of fusion—namely magnetic confinement, which uses magnetic fields to hold plasma—to prove that pathway to clean energy. Other projects like ITER—a massive tokamak under construction in France—are attempting to generate record amounts of energy output, though they will never be part of the energy grid.

Still, fusion’s long-held reputation as a pipe dream—”always 30 years away”—might finally be changing. The engineering problems ensnaring the field are vast, but the substantial progress of NIF is an indication of the field’s momentum at a time when the world is in dire need of clean energy solutions at scale.