SpaceX’s first employee, Tom Mueller, thinks the historic IPO is just the beginning

Tom Mueller, CEO of Impulse Space, says investors are buying a vertically integrated vision for space-based computing, AI, and the next industrial revolution.

The guy who built SpaceX’s engines has thoughts on its IPO.

Tom Mueller was employee No. 1 at SpaceX. He built the engines behind the Falcon 9 rocket that rewrote the economics of getting to orbit. Now, he runs Impulse Space, valued at $4.26 billion, which designs and manufactures space vehicles that move satellites from one orbit to another. So, when SpaceX filed for its IPO, Mueller had more skin in the game than most.

His reaction when the S-1 dropped? “Finally.”

For years, Musk was vocally hostile to the idea of taking SpaceX public. He’d lived through the whiplash of Tesla’s public market journey and made no secret of his preference for the freedom of staying private. But SpaceX’s ambitions have outgrown its balance sheet. The company is targeting 555.6 million shares at $135 each—a $75 billion raise that would be the largest IPO in history. At that price, the company is valued at roughly $1.75 trillion.

Mueller told me that valuation “seems incredible”—and he meant it somewhat literally. SpaceX posted $18.67 billion in 2025 revenue with a $4.9 billion net loss, driven by nearly doubled capital expenditures of $20.7 billion, much of it going into AI development. 

“You’ve got to understand what Elon’s selling,” he told me. The valuation is actually a bet on compute and data centers moving to space and that Musk has the vertically-integrated stack to make that happen: Musk has cheap rockets to get hardware into orbit, Starlink has already proven you can run serious computing power in space (the satellite internet business alone generated $11.39 billion in 2025 revenue). And between xAI’s Grok, Tesla’s robotics, and X, he’s sitting on more data to train AI models than almost anyone on the planet. “He has all the pieces,” Mueller said. 

Doubting that thesis, Mueller explained, requires you to ignore SpaceX’s entire track record: Falcon 1, Falcon 9, crewed missions to the ISS, Starlink itself—every single one of those had a chorus of naysayers. “Are we still betting against Elon?” he said. 

As for the trajectory of how the stock will perform, Mueller compared it to riding Tesla from IPO through years of delays before the stock eventually took off. His prediction: a high opening, a “valley of death” when schedule slips become public-market problems, and then—probably—a recovery. The difference, of course, is that being late is a lot more forgiving when you don’t have quarterly earnings calls. 

The way Mueller sees it, SpaceX going public doesn’t just validate the space sector. It accelerates the timeline toward what he’s been working toward since he was a kid watching Star Trek: a true space economy, then megastructures built from lunar and asteroid resources, then outward. Next, Impulse is launching spacecraft Helios with a 2027 target.

“I’m going long,” he said—and he wasn’t talking about the stock.

SpaceX and the secondaries Wild West… Allie here, just back from Brainstorm Tech in Aspen. I stuck my head up yesterday to publish this explainer I feel very strongly about: SpaceX IPO today marks the beginning of a reckoning in the venture secondaries market. For anyone who bought pre-IPO shares of SpaceX through SPVs, the moment of truth is coming: What do you actually own? While you’re waiting to see that stock price, read the whole story here.

See you next week,

Lily Mae Lazarus
X: @LilyMaeLazarus
Email: lily.lazarus@fortune.com
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This story was originally featured on Fortune.com