Tom Mueller worked for Elon Musk at SpaceX for almost 20 years: 'I learned never to tell him no'

• Tom Mueller helped Elon Musk set up SpaceX in 2002.
• Mueller went from playing with toy rockets in Idaho to shaping one of the world's most innovative firms.

Tom Mueller may not be a household name, but he was Elon Musk's righthand man at Space X for about two decades.

Mueller spoke to Walter Isaacson for his new biography of Elon Musk, revealing the demanding billionaire's biggest weaknesses and what it was like working for him.

From growing up in rural Idaho to becoming SpaceX's propulsion chief, here's how Mueller became a leading figure in the aerospace world.

Mueller spent his college summers logging in Idaho before moving to Los Angeles

Mueller grew up just 100 miles from the border of Canada in the town of Saint Maries, population 2,500. Passionate about science fiction, he started building rockets aged 14.

With a father who worked as a lumberjack, Mueller took up the chainsaw during his summer vacations from the University of Idaho in the mid-1980s.

He still has "the rough-hewn look of a future lumberjack," according to Isaacson. But growing up around machines and tools also informed his passion for science and rocket building. "Being hands-on gave me a feel for what would work and what wouldn't," he tells Isaacson.

After graduating, Mueller moved to Los Angeles to start his career in aerospace, getting a job working on aircraft at TRW and becoming a member of the Reaction Research Society, America's oldest amateur rocketry club.

Musk and Mueller devised SpaceX on a Super Bowl Sunday

One Sunday in January 2002, Mueller was working on a homemade rocket in a garage with friends when he was told the internet millionaire Musk, who'd just sold PayPal to Ebay for $1.5 billion, wanted to meet him.

They arranged a meeting for the following weekend, which happened to be Super Bowl Sunday, at which they sketched out plans for the first SpaceX rocket.

"We watched like maybe one play, because we were so engaged in talking about building a launch vehicle," Mueller told Isaacson.

Along with Chris Thompson, the trio set up what was known as Space Exploration Technologies Corporation before becoming SpaceX later that year. Mueller was made head of propulsion – calculating how to safely create enough thrust to get the rockets off the ground.

"I was very lucky that I met the right visionary and because of my passion for rocket engineering I was invited to this opportunity that became SpaceX," he said of the meeting at a 2018 commencement speech at the University of Idaho.

Mueller's rocky start with Musk

Mueller made a misstep when he started working at SpaceX. Not wanting to risk his finances if the venture failed, he asked Musk to put two years' worth of compensation into escrow.

Musk agreed, but Isaacson writes that this meant Musk considered "Mueller an employee, rather than a cofounder, of SpaceX."

"You cannot ask for two years of salary in escrow and consider yourself a cofounder" Musk told Isaacson. "There's got to be some combination of inspiration, perspiration, and risk to be a cofounder."

"A maniancal sense of urgency is our operating principle"

At SpaceX, Mueller got the chance to fulfill his childhood dream of working on rockets. But he was also working for an "insane" boss who managed SpaceX through aggressive scheduling, a learn-by-failing mantra, and taught his employees to never say no to him.

"If you were negative or thought something couldn't be done, you were not invited to the next meeting," Mueller recalls in Isaacson's biography. "He just wanted people who would make things happen."

On presenting an already cut-down schedule for a Merlin engine, Musk complained that they had to move faster, per Isaacson's book. "How the fuck can it take so long?" Musk asked. "This is stupid. Cut it in half."

When Mueller told him that was impossible, he was held back after the meeting and told that if he wanted to remain in charge of engines he should give Musk what he asked for.

"I learned never to tell him no," Mueller says. "Just say you're going to try, then later explain why if it doesn't work out".

Sometimes the sense of urgency made the impossible happen, Mueller says of Musk's operational style in the biography. But it was also his biggest weakness: "If you give them a schedule that's physically impossible, engineers aren't stupid. You've demoralized them. It's Elon's biggest weakness."

In May 2014 he became CTO of propulsion, leading the development of the Merlin rocket engine that powers the Falcon 9 rocket, and the Draco engines that power the Dragon spacecraft.

"I am very proud of what we have achieved at SpaceX," Mueller told the University of Idaho in 2018.

Mueller's Mars race with Musk

Mueller left SpaceX in late 2020 and, thanks to significant investor encouragement from the likes of Peter Thiel, founded his own company, Impulse Space. It's building a spacecraft that can cost-effectively deliver "multiple payloads to unique orbits from a single launch," per its website.

Impulse is also teaming up with Relativity Space, which successfully launched the world's first 3D printed rocket earlier this year. They aim to delivery the first commercial payload to Mars in 2026 with Relativity Terran R launch vehicle, which uses Impulse rockets.

If they succeed, Mueller will be part of the team that beats Musk to his goal of being the first to reach Mars.

Mueller still hopes to go to space himself. "My bucket list would be to go the moon and ride an electric dirt bike on the moon," he told the Pathfinder podcast.

Mueller did not immediately respond to a request for comment from Insider.