TL;DR

Impulse Space raised $500 million in a Series D at a $4.26 billion valuation, bringing total funding to $1 billion. Founded by SpaceX’s first employee Tom Mueller, the company builds “space tugs” for orbital transfer and is working with Anduril on Trump’s Golden Dome missile defence shield.

Impulse Space, the orbital transfer vehicle startup founded by Tom Mueller, has raised $500 million in a Series D round that values the company at $4.26 billion. The round was co-led by 137 Ventures and Banner VC, with participation from existing investors including Peter Thiel’s Founders Fund and Linse Capital. The company has now raised roughly $1 billion since its founding in 2021, including a $300 million Series C just one year ago.

Mueller is not a typical startup founder. He was SpaceX’s first employee and the propulsion engineer who led the development of the Merlin and Raptor engines that power every Falcon 9 and Starship flight. As SpaceX prepares for the largest IPO in history, the company Mueller helped build from a warehouse in El Segundo is heading toward a $1.8 trillion public valuation. The company he founded after leaving is now worth $4.26 billion on its own.

What space tugs do

Rockets get satellites into space. But getting a satellite into the precise orbit it needs to operate is a separate, often expensive problem. Most launch vehicles deposit payloads into a standard low Earth orbit or transfer orbit, and the satellite then uses its own propulsion to reach its final destination. That process burns fuel the satellite could otherwise use for station-keeping over its operational lifetime, reducing its useful lifespan.

Impulse Space builds vehicles that solve this by acting as orbital taxis. The company’s Mira craft has flown three missions, with the most recent launching in November 2025. Mira can deploy satellites, host payloads, and manoeuvre within orbits. In an industry where a single launch failure can destroy hundreds of millions of dollars in hardware, having a manoeuvrable transfer vehicle that can precisely position payloads adds a layer of flexibility and reliability to the deployment chain.

The larger Helios vehicle, currently under development, is designed to move heavier payloads from low Earth orbit to geostationary orbit and beyond. Impulse plans to begin rideshare missions to geostationary orbit using Helios in 2027, offering a service that would let multiple satellite operators share the cost of reaching high orbits rather than booking dedicated launches.

The defence angle

Impulse Space is also working with Anduril Industries to create prototypes of space-based interceptors for President Trump’s Golden Dome missile defence shield, a layered system intended to protect the US from ballistic missile and hypersonic weapon attacks. The project requires spacecraft that can manoeuvre quickly and precisely in orbit, exactly the capability that Impulse’s propulsion systems are designed to provide.

The defence connection is significant for the company’s valuation. Space defence contracts provide predictable, long-term revenue streams that commercial satellite customers do not, and the Golden Dome programme is expected to generate tens of billions of dollars in procurement over the next decade. For a company with “hundreds of millions of dollars in customer contracts,” as Impulse has disclosed, defence work could become the largest single revenue category.

Scaling up

Impulse Space now employs 500 people with approximately 200 open positions. The company has more than doubled its headcount over the past year and opened new offices in Washington, DC, and Boulder, Colorado, the former signalling its growing engagement with government and defence customers. The $500 million raise will fund team expansion, manufacturing capacity, and the development of propulsion systems optimised for specific use cases including long-distance transport, landing, and orbital repositioning.

The company is developing its own propulsion technology rather than relying on third-party engines, a vertical integration approach that mirrors what Mueller helped build at SpaceX. Controlling the propulsion stack gives Impulse the ability to optimise vehicles for different mission profiles and reduces dependency on suppliers in a market where lead times for specialised space hardware can stretch to years.

The space economy thesis

Impulse Space’s $4.26 billion valuation reflects a broader bet that the space economy needs an infrastructure layer between launch and operations. SpaceX dominates launch. Satellite operators like SpaceX’s own Starlink, Amazon’s Kuiper, and dozens of smaller constellations are building the applications. What sits between them, the logistics of getting hardware to the right place in space efficiently, is the market Impulse is targeting.

If the analogy holds, Impulse Space is building the trucking and logistics network for orbit. The $1 billion raised in five years, the Founders Fund backing, the SpaceX pedigree, and the Golden Dome contract all point to a company that investors believe will become 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.

Impulse Space, a startup founded by SpaceX engine guru Tom Mueller to build highly-maneuverable spacecraft, announced a $500 million Series D this week that it will use to hire as many as 200 new employees.

The round, led by 137 Ventures and BANNER VC, with participation from Founders Fund, Lux Capital, and Linse Capital, reflects investor interest in space and defense tech as the U.S. government hurls cash at national security problems and SpaceX gears up for its IPO.

Impulse is focused on in-space mobility. The company has developed a highly maneuverable platform called Mira that is targeted at U.S. Space Force buyers. It’s also building Helios, a vehicle designed to carry satellites rapidly to high orbits after they are dropped off in space closer to Earth.

President and COO Eric Romo told TechCrunch that the new capital will help the company build and test more space vehicles and emphasized the company’s hiring plans at a time when aerospace talent is in high demand.

While the company’s software teams are adopting AI coding tools, Romo said that when it comes to solving engineering problems in the real world, deep learning models aren’t quite ready for prime time. As the 13th employee at SpaceX back in 2003, Romo’s job was creating computer simulations of the company’s engine design to assess its performance.

“I considered it success if I got within 20% of the right answer, because the simulations were just not that good,” Romo said. “They’ve improved, but they’ve not improved that much, and so there’s not really any substitute for designing the thing, analyzing the thing, building it, and then getting it on the test stand.”

Romo suspects AI tools for hardware design may be slower to arrive because the right training data is hard to find, compared to the amount of text and code available on the internet to train LLMs. “If you want to go, say, find the best designs for a turbo pump seal package in the world, you’re not going to find those online,” he points out.

Impulse started with a focus on propulsion and evolved to build spacecraft, requiring the company to add more expertise in the form of engineers who build vehicle structures and flight computers. One reason the company recently opened an office in Colorado is that aerospace talent has more options today — instead of just going to Los Angeles, engineers can find work in Seattle, Denver, or Texas.

Next up for the company is another launch of its Mira spacecraft, which made its third flight late last year. That flight wasn’t without incident — a problem with its navigation system led it to expend much of its propellant early on. Romo said the company is prepping a new Mira mission that is expected to launch before the end of the year.