Hypersonic weapons startup Castelion has raised US$350 million in series B funding led by Lightspeed Venture Partners and Altimeter Capital, valuing the company in the billions.

This new funding follows Castelion’s US$100 million series A round in January 2025, which consisted of US$70 million in equity and US$30 million in debt.

The company aims to advance the production of hypersonic missile systems, which are considered critical for national defense.

Founded by former SpaceX executives, Castelion is developing low-cost hypersonic missiles using rapid development and vertical integration strategies.

The company has secured US military grants and completed its first vehicle test in March 2025, advancing plans for scalable hypersonic production.

Castelion is part of the US Army’s 2026 budget under Project HX3, aiming to deliver a prototype by 2026 and begin producing the Blackbeard system by 2028.

🔗 Source: TechCrunch

🧠 Food for thought

1️⃣ Hypersonic weapons market represents a massive opportunity for startups challenging defense primes

The hypersonic weapons market that Castelion is entering represents substantial financial opportunity, valued at $7.12-8.35 billion in 2023/2024 and projected to grow to $18.94 billion by 2032, with a CAGR of approximately 10-11% 12.

The Pentagon has invested over $8 billion in hypersonic research since 2019, with projected annual spending reaching $5 billion by the mid-2020s, demonstrating the government’s commitment to developing these capabilities 34.

Traditional defense contractors have dominated this space, with Raytheon securing a $985 million contract for hypersonic cruise missiles in March 2023 1. However, venture capital is increasingly flowing to startups like Castelion to challenge incumbents.

This trend reflects broader Pentagon efforts to engage with startups, with over $500 million in venture capital invested in hypersonic technology startups in the past two years alone 5.

Castelion’s rapid funding progression—from $100 million Series A to $350 million Series B within months—demonstrates investor confidence in the company’s approach and the broader market opportunity in defense technology innovation.

2️⃣ The SpaceX model is reshaping defense technology development

Castelion’s approach explicitly mirrors the SpaceX playbook: “build quickly, test frequently, and vertically integrate to drive down costs,” representing a shift in how military technology is developed 6.