Castelion Raises $350M Series B to Industrialize America’s Hypersonic Arsenal

Castelion, a Torrance-based defense technology company working to restore America’s conventional deterrence capability, has raised $350 million in Series B financing led by Altimeter Capital and Lightspeed Venture Partners, with participation from Lavrock Ventures, Andreessen Horowitz, General Catalyst, First In, Space VC, Cantos, BlueYard, Avenir, Champion Hill and Interlagos.

The funding supports the three-year-old company’s mission to directly advance a top Pentagon modernization priority to develop hypersonic munitions production at scale. They will support the company’s integration of its first hypersonic weapon, Blackbeard, with U.S. Army and U.S. Navy operational platforms. It will also be used to build a production and final-assembly facility, Project Ranger, a 1,000-acre solid rocket motor manufacturing campus announced in November. And fund multi-service platform testing in 2026.

“Blackbeard helps close America’s hypersonic capability gap against China and Russia,” said Bryon Hargis, chief executive and co-founder of Castelion, in a statement. “This funding lets us build fast, test often and produce at volumes that matter in the real world.”

In 2025, Castelion conducted more than 20 development flight tests, validating weapon-critical subsystems, including internally manufactured solid rocket motors, control actuation systems, flight computers, seekers, thermal protection materials and mission software. Each campaign focuses on low-cost, mass-producible architectures that replace designs historically built in low volumes, at extreme cost or only on multi-year timelines.

“Castelion was founded by a special team of SpaceX alumni who, in just 2.5 years, took a clean-sheet hypersonic from concept to more than 25 flight tests and major integration contracts,” said Erik Kriessmann, partner at Altimeter Capital, in a statement. “We’re leading this round because of what they’ve achieved in record time, and so they can rapidly scale production of one of the U.S. Department of War’s most critical capabilities: affordable, mass-produced hypersonics, from hundreds to thousands of missiles per year.”

Information for this article was sourced from Castelion.