Jeff Thornburg, a key figure in developing SpaceX's Raptor engine, has co-founded Portal Space Systems to advance solar thermal propulsion technology. The startup, established in 2021, announced a $50 million Series A funding round, valuing the company at $250 million, with lead investors including Geodesic Capital and Mach33. Portal aims to harness concentrated solar heat to propel spacecraft at high speeds, a concept NASA explored but did not commercialize due to a lack of demand for in-space mobility. With the increasing number of satellites and military requirements for rapid orbital maneuvering, Portal's technology is gaining traction, having already secured $45 million in U.S. military funding. The company plans to demonstrate its "fighter jet for orbit" prototype, the SuperNova spacecraft, in 2027, building on advancements in additive manufacturing and materials science.