Portal Space Systems announced on Thursday that it has closed a $50 million Series A funding round, bringing the company’s valuation to $250 million. The round was co-led by Geodesic Capital and Mach33, with participation from Booz Allen Ventures, ARK Invest, AlleyCorp, and FUSE.
Founded in 2021, the startup is led by Jeff Thornburg. A former key engineer at SpaceX, Thornburg was instrumental in turning the full-flow staged combustion cycle concept into the "Raptor" engine that powers SpaceX’s heavy-lift launch vehicles.
Building a "Fighter Jet" for Orbit
Portal is currently developing a cutting-edge technology known as "solar thermal propulsion." Unlike traditional satellite engines, this technology does not rely on chemical combustion, nor does it merely convert solar energy into electricity.
Thornburg explains that the engine uses concentrators to collect solar thermal energy, which then directly heats the propellant. This provides spacecraft with significantly more power than conventional electric propulsion systems. Industry analysts suggest that this design will grant spacecraft exceptional maneuverability in orbit, leading many in the sector to refer to the craft as "fighter jets for orbit."
Research into solar thermal propulsion dates back to the 1960s. While it has long existed as a theoretical concept for deep-space missions, it has never been successfully deployed in orbit. Thornburg and his co-founders, Ian Vorbach and Prashaanth Ravindran, aim to change that within the next two years.
Thornburg began his career in the U.S. Air Force, where he focused on high-performance rocket engine research. He is now applying that deep engineering expertise at Portal, aiming to transform research projects once shelved by NASA into highly efficient propulsion solutions for the commercial space sector.
With this $50 million infusion, Portal plans to accelerate the prototyping and testing of its propulsion system. The company’s goal is to achieve technical validation in the near term, providing the U.S. military and commercial space markets with more competitive orbital maneuvering capabilities.
