Former SpaceXer brings in largest space seed round for next generation spacecraft

Jeff Thornburg, former SpaceX VP that oversaw the development of Starship‘s Raptor engine, announced today that his company, Portal Space Systems, has raised $17.5 million in seed funding. The company plans to finish development and launch its first Supernova satellite system that is powered by an engine that comes with the benefits of nuclear propulsion, without the reactor.

Led by another former SpaceX employee, Brandon Jones of AlleyCorp, the seed funding brought in a suspected record-breaking $17.5 million to the company for final development, testing, and its first mission.

Supernova, Portal Space Systems’ core product, is described by the company as a “multi-role, trans-orbital spacecraft” that will target defense and commercial customers who need rapid response and mobility while in orbit.

Powered by “solar thermal propulsion,” the company states the engine uses a similar propulsion method to that of a nuclear engine, minus the need for a reactor or nuclear material. While dreamed of by many sci-fi enthusiasts, a major roadblock for nuclear propulsion is regulatory approval.

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Currently, in the United States, only the NASA Administrator or President has the authority to authorize a rocket launch that contains nuclear material. To date, these have primarily been Radioisotope Thermal-Electric Generators used by missions like the Voyager probes and Mars rovers.

Supernova’s engine promises to remove the red tape while keeping the same benefits of nuclear energy by using the Sun as its heat source.

Portal Space Systems’ timeline with its new funding is to finish its critical design review and full testing of the thruster this year, with the launch of its first demonstration mission no earlier than mid-2026.

Thornburg is one of many former SpaceX engineers who have left the company to start their own. He previously served as VP of Propulsion Engineering, leading the development of SpaceX’s Raptor engine. He left after 2015, before he could see the project through to flight about five years later.

Thornburg later went on to work at Amazon’s Project Kuiper, Stratolaunch, where he still serves as an advisor, and engine manufacturer Ursa Major.

With space above us getting ever crowded, and the need for space awareness, companies or the Space Force to keep track of what is up there, there is a need for hyper-mobile spacecraft. The ability to use the Sun as a source of energy to power their engines will allow Supernova to reach high efficiency numbers, leading to a longer usefulness to potential operators.