Washington startup Helion Energy says its seventh-gen Polaris prototype will be the world's first fusion generator to demonstrate net electricity production, as early as 2024, and it's roped in a record-breaking funding round to get it built and running.

The Series E funding round was led by long-term investor Sam Altman, former president of Y Combinator and current CEO of OpenAI, who has now taken on an executive chairman role at Helion. Others involved include PayPal co-founder Peter Thiel, through his Mithril Capital company, former eBay president Jeff Skoll, through his Capricorn Investment Group, and Facebook co-founder Dustin Moskovitz.

The raise brings in a record US$500 million now, with an "opportunity for an additional US$1.7 billion dollars tied to Helion reaching key performance milestones." The money will be used to complete the Polaris facility currently under construction in Everett, Washington.

Polaris will expand on the impressive achievements of Helion's sixth-gen "Trenta" prototype, built in 2020, which has completed more than 10,000 high-power pulses, and has run "nearly every day" for more than 16 months. Earlier this year, Trenta managed to demonstrate a temperature over 100 million degrees Celsius, which is significant, since it's around the point at which there's enough thermal energy to create large amounts of fusion.