Helion, the fusion startup with backing from Sam Altman, closed a $465 million Series G on Thursday, pushing its valuation to $15.5 billion. The round, led by Thrive Capital, brings total funding to $1.5 billion. Proceeds are earmarked for Orion, Helion’s first commercial power plant, which it aims to deliver to Microsoft by 2028—an aggressive timeline for an industry still years from grid-scale deployment.

Helion’s architecture sets it apart. Most fusion designs—whether magnetic confinement or laser-based—use steam turbines to convert heat into electricity. Helion instead extracts energy directly from the reactor’s magnetic fields. When plasma expands after fusion, it pushes against those fields, inducing current in the magnets—analogous to regenerative braking in an EV. This direct-drive approach could boost plant efficiency significantly, but it relies on physics that remains largely unvalidated in peer-reviewed literature. CEO David Kirtley has publicly dismissed the need for academic publication, arguing that empirical results from Helion’s devices will speak for themselves. Many fusion physicists remain unconvinced.

The raise is part of a broader capital surge in fusion. Focused Energy ($240M), Thea Energy ($100M), Inertia Energy ($450M), and Type One Energy ($250M) all announced rounds in recent months. Investors are betting on fusion’s promise of near-limitless, always-on power—particularly attractive for AI data centers—despite most companies projecting commercial plants no earlier than the mid-2030s. The payoff is enormous if costs drop, but the timeline remains the sector’s biggest engineering risk.

Source: TechCrunch