Castelion, a defense technology company focused on restoring America's conventional deterrence capability, has raised $350 million in Series B financing. The round positions the company to address one of the Pentagon's top modernization priorities: producing hypersonic munitions at scale.
The funding will support several technical and manufacturing milestones. These include integrating Castelion's first hypersonic weapon, Blackbeard, with U.S. Army and Navy operational platforms. The company also plans to build its production and final-assembly facility, Project Ranger, and conduct multi-service platform testing in 2026.
Altimeter Capital and Lightspeed Venture Partners co-led the investment. They were joined by Lavrock Ventures, Andreessen Horowitz, General Catalyst, First In, Space VC, Cantos, BlueYard, Avenir, Champion Hill, and Interlagos.
"Blackbeard helps close America's hypersonic capability gap against China and Russia," said Bryon Hargis, CEO and Co-Founder of Castelion. "This funding lets us build fast, test often, and produce at volumes that matter in the real world."
Hypersonic weapons travel at speeds exceeding Mach 5 and can maneuver during flight, making them extremely difficult to intercept. Both China and Russia have invested heavily in these systems over the past decade, creating what defense experts describe as a capability gap with the United States.
Traditional defense contractors have struggled to produce hypersonic weapons affordably and at volume. Castelion's approach aims to change that by compressing design-to-launch cycles from years to months. The company has also built an industrial base designed for high-rate missile production rather than limited inventory.
"Hypersonic weapons capacity will shape great power competition for generations," said Katherine Boyle, General Partner at Andreessen Horowitz. "China recognized this a decade ago and deployed at scale. Castelion leads America's arsenal renewal with the speed, cost advantage, and volume at scaled production that our nation demands."
The investment enables Castelion to expand manufacturing and workforce development across the United States. A major portion will fund Project Ranger, a 1,000-acre solid rocket motor manufacturing campus in Sandoval County, New Mexico. The facility, announced in November, will be capable of producing thousands of Blackbeard missiles per year. It will also create hundreds of high-skilled industrial jobs in the region.
Additional funds will support an aggressive test schedule in 2026 with increasingly complex capability demonstrations. Castelion is also working on a second hypersonic product line that leverages shared low-cost subsystem infrastructure from Blackbeard's development.
In 2025, Castelion conducted more than 20 development flight tests. These validated weapon-critical subsystems including internally manufactured solid rocket motors, control actuation systems, flight computers, seekers, thermal protection materials, and mission software.
Each test campaign focuses on low-cost architectures that can be mass-produced. This replaces designs historically built in limited quantities, at extreme cost, or only over multi-year timelines.
"Castelion is transforming the economics of our defense industrial base," said Paul Kwan, Managing Director at General Catalyst. "Modern deterrence demands hypersonic capability at a pace, scale and cost that the U.S. has never seen."
Castelion was founded by former SpaceX engineers who brought their experience in rapid iteration and cost-efficient manufacturing to the defense sector. In just 2.5 years, the team took Blackbeard from concept to more than 25 flight tests and secured major integration contracts.
The company is headquartered in Torrance, California, with manufacturing operations in New Mexico, Texas, and California. Blackbeard is the first U.S. hypersonic system designed from the start for industrial-rate output and commercial unit cost.
"Castelion was founded by a special team of SpaceX alumni who, in just 2.5 years, took a clean-sheet hypersonic from concept to 25+ flight tests and major integration contracts," said Erik Kriessmann, Partner at Altimeter Capital. "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."
The investor roster reflects strong confidence in defense technology startups that can deliver real manufacturing capability, not just prototypes.
"Castelion isn't just building missiles; they're rebuilding America's industrial depth," said Connor Love, Partner at Lightspeed Venture Partners. "This team has proven they can move from blank sheet design to hardware under test faster than anyone thought possible."
Lavrock Ventures, which focuses on technologies that strengthen national security, was an early backer of the company.
"Lavrock invests in critical technologies that strengthen America's national security, and Castelion is doing exactly that," said Alex Poulin, Partner at Lavrock Ventures. "Hypersonics only matter if you can build them at scale. Castelion's team understands that, and they're engineering a production-ready capability designed for real-world manufacturing and deployment. We're proud to be early backers of a team focused on delivering capacity, not just concepts."
Altimeter Capital is a technology-focused investment firm that manages various funds in public and private markets. Lightspeed Venture Partners is a global multi-stage venture capital firm managing over $40 billion in assets. Lightspeed has been an early investor in companies including Anthropic, Glean, Mistral, Rubrik, Snap, and Wiz.
