HELION ENERGY

Founded in 2013 by David Kirtley, a nuclear engineer who had been working on fusion concepts since grad school. Helion went through Y Combinator in 2014 — one of the most unusual YC companies ever, given that most YC startups are building apps, not fusion reactors.

The company spent years in relative obscurity, iterating on its plasma accelerator prototypes. The breakthrough moment came when Sam Altman, then president of YC and later CEO of OpenAI, became personally convinced that Helion's approach was the real deal and wrote a $375 million personal check — one of the largest individual investments in a private company ever.

Helion is building a fusion power plant that generates electricity directly from fusion reactions — no steam turbines, no intermediate steps. Their approach uses a pulsed non-ignition fusion system, which basically means they smash plasma together at insane speeds, capture the energy from the expanding magnetic field, and convert it directly to electricity.

If it works, the fuel is effectively limitless — they use deuterium and helium-3, which can be produced from water.

Polaris (7th-gen fusion prototype), Direct energy capture system, Deuterium-Helium-3 fuel cycle

Helion's strategy is to skip the traditional fusion path (build a reactor, prove it works, then find customers) and go straight to commercial commitments. They signed a power purchase agreement with Microsoft in 2023 — the first-ever commercial fusion PPA — promising to deliver 50+ megawatts by 2028.

This creates external pressure to deliver, but also proves there is real demand waiting.

Fusion has been "30 years away" for the last 70 years. The physics is brutally hard — you need to create and contain plasma hotter than the sun, and every previous attempt has consumed more energy than it produced.

Helion claims their 6th prototype achieved 100 million degrees Celsius in 2021. The 7th prototype, Polaris, is supposed to demonstrate net electricity by 2024.

Critics say the timeline is wildly ambitious.

Sam Altman (personal investment, $375M), OpenAI CEO backing, Capricorn Investment Group, Mithril Capital, Y Combinator