Castelion Closes $350 Million Series B to Mass Produce U.S. Hypersonic Weapons

Castelion, a cutting-edge defense technology company working to restore America's conventional deterrence capability, led by Bryon Hargis, Sean Pitt, Andrew Kreitz, and others, has secured $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 capital raise supports key technical and manufacturing milestones: integrating Blackbeard, the first hypersonic weapon developed by Castelion, with operational platforms used by the U.S. Army and U.S. Navy; constructing the company’s production and final-assembly facility, Project Ranger; and preparing for multi-service platform testing scheduled for 2026.

“Blackbeard helps close America’s hypersonic capability gap against China and Russia,” said Bryon Hargis, CEO and Co-Founder of Castelion. “This funding enables rapid development cycles, frequent testing, and production at strategically meaningful scale in real-world defense environments.”

The latest investment round enables Castelion to accelerate manufacturing capacity and workforce development across the United States:

Project Ranger: Tooling, commissioning, and production ramp at the 1,000-acre solid-rocket-motor manufacturing campus announced in November. The facility is designed to produce thousands of Blackbeard missiles per year and support hundreds of high-skilled industrial jobs in the region.

Test Cadence and Platform Integration: Advancement of a high-tempo test cadence through 2026, including progressively complex capability demonstrations and integration with operational launch platforms across multiple services.

Follow-on System Development: Parallel development and maturation of a second hypersonic product line, built on shared low-cost subsystem infrastructure to accelerate time-to-field and reduce production overhead.

“Castelion was founded by a special team of SpaceX alumni who, in just 2.5 years, advanced a clean-sheet hypersonic system from concept to more than 25 flight tests and major integration contracts,” said Erik Kriessmann, Partner at Altimeter Capital. “This round is being led because of the team’s record-time execution and to enable rapid scaling of one of the U.S. Department of War’s most critical capabilities: affordable, mass-produced hypersonics, growing from hundreds to thousands of missiles per year.”

“Castelion isn’t just building missiles; it is rebuilding America’s industrial depth,” said Connor Love, Partner at Lightspeed Venture Partners. “The team has demonstrated an unprecedented ability to move from blank-sheet design to hardware under test.”

“Lavrock Ventures invests in critical technologies that strengthen America’s national security, and Castelion is delivering exactly that,” said Alex Poulin, Partner at Lavrock. “Hypersonics only matter when produced at scale. The team understands this and is engineering a production-ready capability designed for real-world manufacturing and deployment.”

“Hypersonic weapons capacity will define great-power competition for generations,” said Katherine Boyle, General Partner at Andreessen Horowitz. “China recognized this early and deployed at scale. Castelion now leads America’s arsenal renewal with the speed, cost advantages, and high-volume production the nation requires.”

“Castelion is transforming the economics of the U.S. defense industrial base,” said Paul Kwan, Managing Director at General Catalyst. “Modern deterrence depends on hypersonic capability delivered at a pace, scale, and cost the United States has never achieved before.”

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 test campaign centers on low-cost, mass-producible architectures designed to replace systems historically manufactured in low volumes, at extreme cost, or on multi-year development timelines.

Castelion’s engineering and production model compresses design-to-launch cycles from years to months, while establishing the industrial base required for high-rate hypersonic missile production, moving the U.S. defense ecosystem away from boutique inventory and toward scalable, repeatable manufacturing capacity.