Uncommon Thinkers: Alexis Harroun aims for space with a new engine — and stays grounded

Editor’s note: This series profiles five Seattle-area “Uncommon Thinkers,” who will be recognized Dec. 10 at the GeekWire Gala in partnership with Greater Seattle Partners.

A few weeks after learning that her tiny startup had won a NASA prize to fly its engine in space, Alexis Harroun was camping in Yellowstone, sitting around a fire and looking up at the stars. Satellites kept drifting past overhead — and the news finally sank in.

“I’m like, oh, we’re going to be sending something up and we’re going to be able to see it,” she said. “That was very humbling in a lot of ways and very exciting.”

Harroun is co-founder and CEO of Juno Propulsion, a Tukwila, Wash.-based startup building a new kind of rocket engine. Instead of burning fuel in a steady flame, Juno’s engines use detonation, a supersonic combustion wave that releases more energy from the same amount of propellant.

“It’s essentially like a higher MPG rocket engine,” Harroun said.

The technology has been studied for decades but has never flown in orbit. Juno aims to change that next year, when its engine is set to fly aboard a Momentus satellite in a mission called Project Iris.

That’s a big goal for a company that, when the July 2025 NASA call came, was just Harroun, co-founder and CTO Ari Martinez and a summer intern working out of a one-room office.

If Iris succeeds, Juno’s engines could let satellites run on non-toxic fuel and maneuver far more freely in orbit, something both commercial and defense customers increasingly want. For Harroun, who earned her Ph.D. studying these engines, it would be the payoff of years of work.

Harroun sees the technology as a long-overdue leap. The basic physics behind today’s rocket engines dates to the 1930s and has been refined about as far as it can go, she said, calling it a constraint that’s “been a glass ceiling for too long, in my opinion.”

No astronaut story

Harroun grew up south of Seattle in Federal Way. She didn’t come from an aerospace family or spend her childhood dreaming about space. Her dad was a physician and her mom a flight attendant and flight instructor.

What she did pick up at home was an entrepreneurial streak. Her dad ran his own practice for about 20 years, and her mom is now a real estate agent. Harroun said watching them make “something out of completely nothing” has shaped her own path, especially in building Juno.

She calls herself a “late bloomer” who fell for engineering as she was finishing high school and heading to the University of Washington. Sci-fi became an inspiration along the way, and it’s now one of her favorite genres.

She spent all four years at UW working with professor Carl Knowlen, who leads the Aeronautics & Astronautics Department’s Detonation Engines Lab, and she joined the student rocketry team, eventually leading its propulsion group.

Knowlen “sees the potential in everyone,” Harroun said, and the two built a strong relationship that’s still going. Juno’s $1.2 million National Science Foundation grant, awarded this summer, is a partnership with his research group.

“What’s exciting is seeing this come full circle,” Knowlen said in a 2025 UW story. “Alexis’s passion for this technology grew out of our lab work together, and now we’re collaborating to turn that early research into something that will fly in space.”

During college, Harroun interned at NASA, Boeing and Blue Origin. That first stint at Blue Origin, in 2016, set her next move.

“I realized that everyone who had the job that I wanted had gone to Purdue,” she said.

She spent the next six years at Purdue University in West Lafayette, Ind., earning a master’s degree and a Ph.D. Her doctoral research was on the technology Juno is now building. She also met Martinez there. The two shared an office for years.

Harroun never planned to stay in academia.

“That just didn’t feel like my calling,” she said. “I wanted to use that very unique experience to get the technical chops to do the type of engineering that I wanted to do.”

Her doctoral advisor, Purdue professor Stephen Heister, still advises her and the company.

“He was one of the people who really pushed me to think about starting this company,” Harroun said. “I think he saw the potential that I had as a founder, both from a technical and a leadership perspective.”

Heister recalled their first technical discussion, when Harroun arrived as a new master’s student. He went deep on nozzle flows, her thesis topic, and the complications of building a nozzle for a detonation engine.

“At the end of my diatribe, she sat quietly and said, ‘You’ve given me a lot to think about,’” Heister said. “I can’t think of any other 22-year-old student with such a response but I knew she was indeed a special talent.”

He described Harroun as having “the unique ability to think deeply and at length,” and said it’s “terribly gratifying” to watch her commercialize the technology she worked on as a grad student.

After finishing her Ph.D. in 2023, Harroun came back to the Seattle region and started Juno. She knew the territory: her UW lab work and the rocketry team had put her in touch with local industry, and Juno now works with some of the same companies she did as a student.

Interning at Blue Origin was the first time she could say “there’s literally a rocket company in our backyard,” Harroun said. Its presence helped build a regional talent pool, which she described as “a contingent of rocket scientists that just live here.”

Starting a company comes with many unknowns, and coming home crossed one off the list.

“I knew how to go start doing stuff immediately,” she said. “So it made that calculus really easy.”

The next Rocketdyne

Harroun’s ambitions reach well beyond one demo flight.

“Our mission is to be the rocket engine provider for the U.S.,” she said. “Think of a Rocketdyne.”

That company built engines for the Saturn V and the space shuttle, and it’s now part of L3Harris. Juno wants to play a similar role with a new technology. It’s starting with in-space propulsion for satellites and plans to expand into engines for upper stages, orbital transfer vehicles and, eventually, the boosters that lift rockets off the pad.

The first step is Project Iris. NASA paid Juno about $500,000 through its TechLeap program to build the payload, and it’s also covering the Momentus spacecraft and the flight. There’s no paying customer yet, but the mission is designed to mimic the maneuvers a real satellite would make.

Japan’s space agency has flown rotating detonation engines on suborbital research rockets, but going to orbit is “a whole ‘nother game,” Harroun said. “Going to space is hard. I can attest to that.”

Building a company has taught Harroun things her Ph.D. didn’t. Handling toxic propellants is so complicated, she learned, that operators can spend more fueling a satellite than on “the propulsion system itself, which is kind of crazy.”

The bigger draw is mobility. For decades, satellites have mostly stayed in the orbit a rocket left them in, she said, and “that’s not really acceptable anymore in today’s world.”

To get there, Juno has raised a $1.4 million pre-seed round led by SOSV, on top of its NASA and NSF awards.

As for going to space herself, Harroun admits it would be hard to say no if she got the opportunity.

But the avid hiker and backpacker is partial to terra firma. Her best-case future is one where Earth is the place humanity gets to enjoy and space is what makes that possible.

“I don’t know that I would be the traveler,” Harroun said, “but I’d definitely like to be the enabler.”