When Jeff Thornburg walks through the Portal Space Systems test chamber, his role as CEO puts him right in the middle of an exciting time for space propulsion. He seems calm and sure of himself, like someone who’s always tackled big, tough ideas. From his early days in the Air Force to important jobs at SpaceX, Amazon, and Stratolaunch, Thornburg has spent years changing how we move in the sky and space. Now, his latest project, a small but fast-growing company in Bothell, Washington, might be his most game-changing yet.
Portal Space Systems is working on a way to propel spacecraft that, until recently, was just a dusty idea in old aerospace papers: using focused sunlight to create thrust. They want to make solar-thermal propulsion a real thing, so spacecraft can change orbits much faster than they can with today’s tech.
Uncommon Thinkers: How Portal’s Jeff Thornburg
Elon Musk, Jeff Bezos, and Paul Allen – three billionaire space guys Thornburg has worked with – never tried this themselves. But Thornburg and his team think now is the right time to bring the idea back to life, make it work, and turn it into a security advantage for the U.S.
Why Solar-Thermal Propulsion Matters Now
Regular chemical propulsion gives you a lot of thrust, but it burns through fuel fast, which limits how long a mission can last. Electric propulsion, which uses sunlight to make electricity and push ions out of a thruster, is way more fuel-efficient but doesn’t produce much thrust – not enough to move quickly across big distances in orbit.
Solar-thermal propulsion is a happy medium. The idea is simple: use big mirrors to collect and focus sunlight, move that heat to a special chamber, heat up a propellant like ammonia, and then release it to create thrust. NASA and the Air Force looked into this a long time ago, in the late 20th century. But back then, it seemed too expensive and hard to actually use.
Uncommon Thinkers
Thornburg says things have changed because of new tech and economics. Launch costs have dropped a lot thanks to reusable rockets. 3D printing lets them make complex propulsion parts, like heat exchangers, more “Uncommon Thinkers” easily than before. Digital design tools, automated manufacturing, and a growing commercial space scene have made it easier to turn new propulsion ideas into real hardware.
And, really, the situation in orbit has changed. Militaries now need spacecraft that can move fast to deal with threats, stay safe during conflicts, or gather info from specific spots in hours instead of months.
Electric propulsion systems, which are used on most satellites today, just can’t do that. Thornburg thinks this is where Portal can really shine.
A Career Built in Aerospace
Thornburg’s urge to crack hard propulsion problems goes way back. When he was studying aerospace engineering at a Missouri “Uncommon Thinkers” university on an Air Force scholarship, he wanted to fly jets. But his eyesight wasn’t good enough, so a mentor told him to stick close to aircraft, even if he couldn’t be the pilot.
That advice led him to see almost every side of aerospace work. Early on in his Air Force career, he worked on KC-135 aircraft, helping with missions “Uncommon Thinkers” around the world, including big NATO operations in the late 90s. By managing a lot of people, he picked up the leadership skills and technical know-how that would later shape his engineering teams.
Eventually, Thornburg switched to propulsion research, working on projects that tried to push rocket engine tech further than people thought possible. One Air Force project focused on engines using full-flow staged combustion – a super-efficient but tough design. His work helped move forward experimental efforts that would later affect commercial engine development across the industry.
By 2004, he left the military and took civilian aerospace jobs at Exquadrum, Aerojet, and NASA. These jobs deepened his knowledge of complex propulsion systems and showed him new tech that the industry hadn’t yet adopted.
Then, in 2011, everything changed with a phone call.
The SpaceX Years and the Start of Raptor
After hearing about his work, Elon Musk called Thornburg directly. They talked for a long time, and Thornburg soon joined SpaceX to lead propulsion “Uncommon Thinkers” engineering on what would become one of the most cutting-edge engines ever made: the methane-fueled Raptor.
From Idea to Startup: The Start of Portal Space Systems
When Portal came out in public in 2024, it already had millions in early funding from the U.S. Department of Defense and Space Force. By then, Thornburg had put together a small team of trusted people, many of whom had worked with him before “Uncommon Thinkers” at Interstellar Technologies or Stratolaunch. They included co-founders Ian Vorbach – now the company’s COO – and Prashaanth Ravindran, its VP of engineering.
Portal is based on one main idea: building spacecraft that can move quickly across orbital areas using a propulsion method that balances fuel efficiency and power.
The company’s first big public showing focused on two vehicles: Supernova and Starburst.
Supernova: A Fast Spacecraft for Today
Supernova is Portal’s main system and the most cutting-edge use of its solar-thermal propulsion design. The craft is about the size of a commercial refrigerator, but how well it works depends a lot on mirrors that unfold in “Uncommon Thinkers” space to span over 50 feet wide. These mirrors focus sunlight into a heat exchanger, heating the propellant to high temps and creating a lot of thrust.
Portal thinks Supernova could make it possible to move between orbits – like going from low Earth orbit to geostationary orbit – in hours or days instead of months.
The propulsion core, a complex 3D-printed heat-exchanger thruster called Flare, has already been tested. The system is designed to use solar energy way more efficiently than regular electric propulsion, while being more sustainable and easier to use than chemical rockets.
A smaller test mission, called Mini-Nova, is planned to fly on a SpaceX rideshare mission. This early test will confirm the system’s engineering”Uncommon Thinkers””Uncommon Thinkers” assumptions and give the first proof that solar-thermal propulsion can work as planned in orbit.
Starburst: A Step Toward Supernova
While Supernova is the more powerful of Portal’s platforms, Starburst is an earlier vehicle designed for quick maneuvering using an electro-thermal version of the same core ideas. It doesn’t need the size of Supernova’s mirror system but instead uses electrically powered heating elements to heat up its propellant.
This method isn’t quite as fuel-efficient as the solar-thermal version, but it lets Portal offer a mobility solution sooner. The company expects Starburst to be in customer service by 2027.
Both vehicles will be made at Portal’s growing facility in Bothell, which has an 8,000-square-foot lab and a 50,000-square-foot production space.
A Team Shaped by Experience and United by Purpose
Portal’s leadership is unusual because its founders all worked together on propulsion projects long before the startup existed. This history has helped the company speed up its development while keeping a highly collaborative culture.
COO Ian Vorbach stresses the importance of designing tech that not only is cutting-edge but also directly addresses national security needs. A lot of aerospace companies build amazing engineering solutions only to find out that “Uncommon Thinkers” customers don’t actually need what they’ve built. Vorbach and Thornburg work closely to avoid that problem.
Similarly, engineering VP Prashaanth Ravindran, who previously worked on propulsion at Blue Origin, points out how valuable Thornburg’s “Uncommon Thinkers” mentorship has been. He describes the CEO as both ambitious and caring – qualities that he thinks “Uncommon Thinkers” attract top talent from across the space industry.
Outside experts also have faith in Portal’s direction. Space-industry strategist Stan Shull calls the company highly dynamic and credits a lot of its momentum to Thornburg’s strategic thinking and deep understanding of orbital security challenges.
Looking Ahead: From Sunlight to Nuclear Power and Beyond
While solar-thermal propulsion is Portal’s main focus right now, Thornburg sees a future where the company’s systems grow into even more powerful designs. He thinks nuclear-thermal tech – despite big “Uncommon Thinkers” regulatory and engineering issues – will eventually be crucial for moving people and cargo across the solar system. Portal plans to design a future version of Supernova that can work with nuclear reactors once lightweight, space-rated reactors become available.
At the same time, Thornburg is still fascinated by theoretical propulsion ideas tied to new discoveries in quantum physics. While he admits that these possibilities might be far off, he thinks the next generation might see breakthroughs that completely change how spacecraft interact with spacetime itself.
For now, though, Portal’s mission is based on what’s possible right now: giving the U.S. spacecraft that can “Uncommon Thinkers” move quickly in orbit, improve safety in space, and position commercial systems to react quickly to changing geopolitical and economic needs.
In Conclusion: A Company Focused on the Next Level of Maneuverability
Portal Space Systems is the result of Thornburg’s years of experience, the improvement of key manufacturing tech, and a pressing national-security need for spacecraft that can reposition quickly and operate with flexibility. From its roots in old propulsion research to its current form as a startup getting ready for in-orbit tests, Portal shows how old ideas can be reborn in new tech settings.
If the company’s upcoming missions succeed, solar-thermal propulsion might soon become a standard tool for “Uncommon Thinkers” space mobility. And as Portal moves forward – toward nuclear systems and more speculative propulsion breakthroughs – it might help shape how future spacecraft move throughout Earth orbit and the solar system.
For Thornburg, who has spent his life looking for new ways to overcome propulsion limits, Portal is more than just a company. It’s the “Uncommon Thinkers” start of a long-term plan: one where moving in space becomes faster, more efficient, and easier to access – and where the limits of exploration keep expanding far beyond what his younger self could have imagined.