Impulse Space secures $500M at $4.26B valuation for orbital tugs

Impulse Space, the orbital transfer vehicle startup founded by Tom Mueller, has closed a $500 million Series D funding round that pushes its valuation to $4.26 billion. The investment was co-led by 137 Ventures and Banner VC, with existing backers such as Peter Thiel’s Founders Fund and Linse Capital also participating. This latest raise brings the company’s total funding to roughly $1 billion since its 2021 inception, following a $300 million Series C just last year.

Mueller is no ordinary entrepreneur. As SpaceX’s first employee, he engineered the Merlin and Raptor engines that power every Falcon 9 and Starship launch. While SpaceX itself hurtles toward what could be the largest IPO in history, with a projected $1.8 trillion public valuation, the company Mueller founded after his departure now stands at $4.26 billion on its own merits.

Orbital transfer vehicles, often called space tugs, address a critical gap in the satellite deployment process. Rockets deliver payloads to standard orbits, but satellites must often use their own propulsion to reach precise final positions. That consumes fuel meant for station-keeping, shortening operational lifespans. Impulse Space’s Mira craft has flown three missions, the latest in November 2025, deploying satellites, hosting payloads, and maneuvering within orbits. By providing a flexible, repositionable transfer vehicle, Impulse adds reliability to a chain where a single failure can destroy hundreds of millions in hardware.

The company’s larger Helios vehicle, still in development, targets heavier payloads destined for geostationary orbit and beyond. Impulse plans to offer rideshare missions to that high orbit starting in 2027, allowing multiple satellite operators to share costs rather than booking dedicated launches.

A major driver of Impulse’s valuation is its defense work. The startup is collaborating with Anduril Industries on prototypes for space-based interceptors under President Trump’s Golden Dome missile defense shield. This layered system aims to protect the US from ballistic missile and hypersonic attacks. It demands spacecraft capable of rapid, precise orbital maneuvers, a strength of Impulse’s propulsion systems. Defense contracts offer predictable, long-term revenue streams that commercial satellite customers rarely match. The Golden Dome program alone is expected to generate tens of billions in procurement over the next decade. Impulse has disclosed “hundreds of millions of dollars in customer contracts,” and defense work could soon become its largest revenue category.

Scaling up rapidly, Impulse now employs 500 people, with roughly 200 open positions. The workforce has more than doubled in the past year. New offices in Washington, DC, and Boulder, Colorado signal a growing focus on government and defense clients. The $500 million raise will fund team expansion, manufacturing capacity, and development of propulsion systems tailored for long-distance transport, landing, and orbital repositioning.

Impulse builds its own propulsion technology rather than relying on third-party engines. This vertical integration, similar to what Mueller helped establish at SpaceX, allows the company to optimize vehicles for different missions and avoid supply chain bottlenecks that can cause years-long lead times for specialized space hardware.

The $4.26 billion valuation reflects a broader bet that the space economy requires a dedicated infrastructure layer between launch and operations. SpaceX dominates launch. Satellite operators like Starlink, Amazon’s Kuiper, and smaller constellations build applications. Impulse targets the logistics of getting hardware to the right place in orbit efficiently. If the analogy holds, Impulse is building the trucking and logistics network for space. The $1 billion raised in five years, Founders Fund backing, SpaceX pedigree, and Golden Dome contract all suggest investors see Impulse as essential infrastructure for both commercial and military space operations. Whether the space economy grows fast enough to justify a $4.26 billion valuation for a company with three completed missions is the bet the Series D investors are making.