In January 2002, Elon Musk strolled into a warehouse in Los Angeles, where he spotted Thomas Mueller hoisting an 80-pound engine over his shoulder as he bolted it into the lower thrust structure of a rocket. This wasn’t a day job: Mueller, then an engineer at aerospace manufacturer TRW, would often spend his weekends with amateur rocket club Reaction Research Society to build new kinds of rockets outside his scope at work. Musk had shown up at the club’s headquarters to sell its members, including Mueller, on his vision of building a space company that would enable humanity to one day colonize Mars.

Before Mueller had the chance to set the engine down, Musk began firing question after question “in very typical Elon fashion,” Mueller recalls. What is that? Is that a big engine? What’s the biggest engine you’ve worked on? A 650,000 pound engine for TRW, he responded hesitantly. After all, the only thing Mueller knew about Musk was that he was an internet millionaire, recently ousted from his CEO position at PayPal. But it didn’t take long for the two to click: When asked if he could build an engine of similar scale from scratch for Musk, Mueller said yes—even though he knew the real answer was no. “That was the optimism and the naivety that Elon wanted to see because that's the way he was, too,” Mueller said.

The very next week, on Super Bowl Sunday, Mueller invited Musk over to his house where they and a few other members from the rocket club conceived what came to be known as the Merlin engine. A few more meetings later, in April 2002, Mueller officially signed on as employee No. 1 at SpaceX, where he spent the next two decades as one of Musk’s right hands.

Today, that Merlin engine powers the Falcon 9 and Falcon Heavy rockets, famous for revolutionizing the space industry because they’re reusable, allowing for more frequent, lower-cost rocket launches. That propelled SpaceX to a $800 billion valuation, helping turn Musk into the world’s wealthiest person, with a net worth of $730 billion. It’s also set the stage for a mega IPO that could value the company at up to $1.5 trillion this year.

As anticipation bubbles among SpaceX investors and employees for what could be one of the largest public listings of all time, there’s another group eagerly anticipating the IPO: early space tech investors. “This is where it starts to get really fun,” said Chad Anderson, founder of space-focused investment firm Space Capital. “This massive wealth creating situation for a lot of SpaceX employees is certainly going to create a dynamic where we see a lot more founders.”

They’d be in great company. In the last ten years, SpaceX has spawned a........

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