Jeff Thornburg helped transform a government research project into SpaceX’s powerful Raptor engine. Now, at his startup Portal Space Systems, he’s reviving a NASA idea to create a new kind of rocket engine. The company just raised $50 million, valuing it at $250 million.
Portal is developing solar thermal propulsion. Instead of burning fuel or using solar panels, it concentrates the sun’s heat to superheat propellant, creating high-speed thrust. This old concept, studied since the 1960s, is now in demand for modern satellite mobility and national security.
Portal has secured significant U.S. military funding. It plans to launch a prototype in October and its first operational “SuperNova” spacecraft, a nimble orbital vehicle, by 2027. The technology also paves the way for future nuclear thermal rockets, proving key components in space first.