Altman’s $3.7 Billion Fusion Startup Leaves Scientists Puzzled

Sam Altman, the billionaire chief executive officer of OpenAI, is staking a sizable chunk of his personal wealth on a startup chasing the holy grail of nuclear fusion – the elusive, theoretically limitless clean-energy source that, he says, is key to an artificial intelligence-enabled future.

While other billionaires, including Jeff Bezos, Bill Gates and George Soros, have backed fusion ventures, Altman has made his largest personal investment in Helion Energy, which stands out for its audacious timeline. It plans to open the world’s first fusion power plant by 2028 and to supply Microsoft Corp. with energy from it soon ...