Jeff Thornburg, a former SpaceX engineer and one of the key figures behind the development of the Raptor engine used in Starship rockets, is now spearheading an ambitious project at the startup Portal Space Systems.
Founded in 2021, the company announced on April 9, 2026, a $50 million Series A funding round led by Geodesic Capital and Mach33, with participation from investors such as Booz Allen Ventures, ARK Invest, AlleyCorp, and FUSE.
This capital injection valued the company at $250 million, solidifying its position in the aerospace sector.
Portal Space Systems is developing solar thermal propulsion technology, a method that uses solar heat to warm propellants and propel spacecraft at high speeds.
Unlike current satellite systems that rely on chemical fuels or low-power solar-powered electric thrusters, Portal’s system directly harnesses solar thermal energy, promising greater efficiency and cost reduction.
This approach, although studied since the 1960s in government labs, has never been applied in orbit. Thornburg’s team, alongside co-founders Ian Vorbach and Prashaanth Ravindran, aims to realize this advancement within the next two years.
In addition to the Series A funding, the company had already secured $45 million in strategic contracts with the US military, aimed at military applications such as rapid orbital maneuvers for surveillance or threat response.
Added to this, another $67.5 million in private capital was previously raised, totaling over $160 million in resources for the project, as highlighted by Travis Bales, managing director of Booz Allen Ventures.
The demand for space mobility has grown with the increase in satellite launches and the strategic needs of the US in space, especially in scenarios of orbital competition with rival powers.
Portal Space Systems has already conducted initial tests, sending flight electronics on an experimental mission around Earth. The company plans to launch a prototype spacecraft in October 2026, with the goal of demonstrating a functional engine by 2027.
According to Bloomberg, which monitors the aerospace sector, the technology could transform satellite maneuverability, reducing operational costs and increasing flexibility in space missions.
Another highlight is the potential evolution to nuclear thermal propulsion systems, replacing solar heat with that of a nuclear reactor.
Thornburg argues that testing these technologies directly in orbit is more feasible than building ground-based nuclear test facilities, which are estimated to cost around $2 billion. This strategy could accelerate significant advances in space propulsion, positioning the startup as a leader in innovation in the sector.
Although the technology has potential for civilian and commercial applications, the US military interest raises debates about the dual-use nature of such systems.
The ability to quickly move spacecraft between orbits could facilitate exploration missions as well as intensify the militarization of space, a topic that continues to generate discussions in international forums. For now, Portal Space Systems focuses on proving the viability of its technology, with high expectations for the next steps of its ambitious project.
With information from techcrunch.com.
Original published at O Cafezinho.