Portal Space Systems announces $50 million Series A funding round for new Solar Thermal Propulsion engine

Portal Space Systems announced a $50 million Series A funding round Thursday that values the company at $250 million. The round was led by Geodesic Capital and Mach33, alongside Booz Allen Ventures, ARK Invest, AlleyCorp, and FUSE.

The company is developing a technology called solar thermal propulsion. Today's standard satellite engines either burn chemical fuel or convert the sun's energy to electricity, using that to power efficient but low-powered thrusters. Portal's engines would instead concentrate the heat of the sun, using that to heat propellant and move the spacecraft along at high speed.

The technology has been the subject of investigation in government research labs since the 1960s, most recently as a concept for sending a probe into interstellar space, but has yet to make it into orbit. Thornburg, along with co-founders Ian Vorbach and Prashaanth Ravindran, plans to change that in the next two years.

Thornburg began his career in the U.S. Air Force, where he worked on a program to develop an efficient, powerful next-generation kind of rocket engine that engineers call full-flow staged combustion. A decade later, he was wooed to SpaceX by Elon Musk to turn those concepts into the Raptor engine that now powers the company's massive Starship.

After stints working at Stratolaunch and Amazon's Project Kuiper, he turned to propulsion once again.

A new kind of rocket engine

Solar thermal power is, in Thornburg's view, the next logical step in rocket tech. NASA had studied the technology extensively in the late nineties and concluded it provides better performance in many cases. It wasn't developed further because there wasn't enough demand for in-space mobility, according to a 2003 report commissioned by NASA.

With satellites and space probes flying much more rarely back then, it was simpler just to use a more powerful rocket than invest in in-space propulsion. Now, with thousands of new satellites flying every year and the U.S. military demanding spacecraft that can fly quickly between orbits to surveil or threaten rivals, that calculus has been turned on its head.

"It's no longer acceptable to move slowly on orbit," Thornburg told TechCrunch. "You know, China's running circles around our spacecraft. We need equivalent capability."

Portal has already received $45 million in strategic funding from the U.S. military, on top of $67.5 million in private capital, thanks to the potential for using its technology for orbital warfare, according to Booz Allen Ventures' managing director Travis Bales.

And in a future where we may see millions of satellites in orbit around the Earth providing communications and computing services, satellite operators will need cheaper means of maneuvering spacecraft out of each other's way, notes Aaron Burnett, the CEO of the aerospace-focused venture fund Mach33. Burnett sees Portal becoming a "space mobility prime," providing propulsion to a variety of users.

Read the entire article at TechCrunch