Understanding the Breakthrough in Nuclear Fusion Energy and the Challenges Ahead

Some of the world’s richest investors have piled into startups targeting one of the biggest and toughest challenges in science: nuclear fusion. Long seen as the ultimate prize in the quest for clean and abundant energy, fusion is the process that fuels the sun, where a crushing gravitational force smashes atoms together and unleashes their energy. In late 2022, researchers celebrated a long-sought scientific milestone, a sign of progress in a field full of vexing technological challenges and skepticism about near-term prospects.

On Dec. 5, scientists at the Lawrence Livermore National Laboratory in California focused the world’s most powerful laser on a peppercorn-size diamond capsule filled with hydrogen. The beams delivered 2.05 megajoules of energy, triggering a reaction that fused the hydrogen into helium and released 3.15 megajoules. The difference, a little more than a megajoule, is roughly the amount of energy released by a hand grenade. The result, known as net energy gain (meaning more energy out than in), was an accomplishment that scientists had been pursuing for decades. It suggested that the core physics of controlled fusion had been cracked, creating the possibility of a process to produce cheap, carbon-free electricity. On the other hand, multiple efforts to replicate the results at the same lab have failed.