Hypersonic weapons startup Castelion is raising a $350 million Series B round, led by Lightspeed Venture Partners and Altimeter Capital, according to sources and documents reviewed by TechCrunch.
The deal, which values the company in the billions, is expected to close within weeks, following a signed term sheet.
From Stealth to Scale
Founded by ex-SpaceX executives, Castelion exited stealth in late 2023 with an ambitious goal: to revolutionize the production of hypersonic missile systems. The company has quickly gained momentum, securing grants from agencies including the U.S. Air Force Research Laboratory and Naval Air Systems Command.
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SpaceX-Style Approach to Defense
Echoing SpaceX’s strategy, Castelion focuses on rapid development, frequent testing, and vertical integration to drive down costs. The startup completed its first test of a hypersonic vehicle in the Mojave Desert this March and is working toward scalable, low-cost deployment.
Backing from the U.S. Army
Castelion appears in the Army’s 2026 budget under “Project HX3,” with a $25 million request to support its Blackbeard Ground Launch (GL) system. The goal is to develop an affordable hypersonic missile with roughly 80% of the performance of current long-range systems, but at a lower cost.
Roadmap to 2028 Deployment
The contract, pending President Trump’s signature, includes two phases: a prototype demo in early 2026 and delivery of 10 additional units in 2027. If successful, full-scale delivery could begin as early as 2028.
Competing with Industry Giants
With continued success, Castelion could challenge legacy aerospace players like Lockheed Martin, Raytheon, and Northrop Grumman. Its ability to produce cost-effective hypersonic weapons may reshape the defense landscape—and secure major government contracts in the process.
