Impulse Space, founded by SpaceX's first employee, has completed a $500 million Series D funding round, reaching a valuation of $4.26 billion.

On June 4, tech industry news outlet Tech Funding News reported that Tom Mueller—SpaceX’s first-ever employee—has founded space infrastructure firm Impulse Space, which has secured a $500 million Series D funding round. The round was co-led by 137 Ventures and BANNER VC, putting Impulse’s post-money valuation at $4.26 billion. With this financing, the company has now raised more than $1 billion in total capital. Founded in 2021, Impulse Space specializes in solving maneuvering challenges faced by spacecraft after launch. The company builds chemical propulsion systems for rapid trajectory adjustments, orbital transfers, and on-orbit operations. Its Mira Precision Maneuvering Spacecraft has already completed multiple successful missions, while the Helios high-energy upper stage is scheduled for its maiden flight in 2027. The Helios system is designed to quickly deliver payloads to geostationary Earth orbit (GEO), the Moon, and heliocentric orbits. Mueller, a former SpaceX veteran who led development of the Merlin engine for the Falcon 9 rocket and the Raptor engine for Starship, emphasized that Impulse Space is not just about building spacecraft—it’s about constructing the economic and technological engine to push humanity forward into space.