A New Space Propulsion Era
Jeff Thornburg, a key figure behind SpaceX's powerful Raptor rocket engine, is spearheading a new venture called Portal. Founded in 2021, Portal has secured
$50 million in Series A funding, valuing the company at $250 million, with support from notable investors like Geodesic Capital and Mach33. The company is focused on developing solar thermal propulsion, a technology that aims to harness the sun's heat directly to propel spacecraft at high speeds. Unlike current satellite engines that rely on chemical fuel or electricity generated from solar power for low-thrust operations, Portal's system will concentrate solar energy to heat a propellant, providing significantly greater thrust. This approach has the potential to dramatically improve in-space maneuverability and speed, addressing a growing need in the satellite industry and for national security applications. The technology has been explored by government research labs for decades, but Portal intends to be the first to bring it into operational orbit within the next two years.
Solar Thermal's Untapped Potential
The concept of solar thermal propulsion has a long history, with NASA extensively studying its benefits in the late 1990s. A 2003 NASA report indicated that while the technology offered superior performance in many scenarios, it wasn't pursued further due to a lack of demand for rapid in-space mobility. In an era when fewer satellites were launched, the reliance on more powerful initial launch rockets was simpler than investing in sophisticated in-space propulsion. However, the current landscape has shifted dramatically. With thousands of new satellites being deployed annually and increasing military requirements for rapid orbital adjustments for surveillance and strategic positioning, the need for swift maneuverability has become paramount. Thornburg emphasizes this shift, stating, "It's no longer acceptable to move slowly on orbit." Portal's innovation directly addresses this urgent demand for faster, more agile spacecraft.
Bridging to Orbit
Portal's journey towards orbital deployment is progressing with tangible steps. The company recently conducted a test flight of its flight electronics on a shakedown cruise around Earth, and another prototype spacecraft is slated for launch in October. The anticipated launch of their first SuperNova spacecraft in 2027, described by Thornburg as a "fighter jet for orbit," will serve as a demonstration of a fully operational solar thermal engine prototype. Portal benefits significantly from recent advancements in additive manufacturing and materials science, which have been crucial in developing their integrated solar concentrator and nozzle system, known as the Hex thruster. While the concept of nuclear-powered rockets is often cited as the ultimate advancement for deep space travel, the complex regulatory and safety hurdles make it an impractical endeavor for a startup. However, Portal's solar thermal technology lays essential groundwork for future nuclear thermal propulsion systems, as it will have already proven many of the core orbital operational components. Thornburg notes that this will allow his team to mature such advanced technologies much more rapidly in orbit than through extensive, costly ground-based testing facilities.
Funding and Military Interest
The significant potential of Portal's solar thermal propulsion for space mobility applications has attracted substantial investment and strategic partnerships, particularly from the U.S. military. The company has already secured $45 million in strategic funding from the U.S. military, in addition to its $67.5 million in private capital. Travis Bales, managing director at Booz Allen Ventures, highlighted the military's interest in the technology for its implications in orbital warfare scenarios. Furthermore, Aaron Burnett, CEO of the aerospace-focused venture fund Mach33, foresees Portal becoming a "space mobility prime." As the orbital environment becomes increasingly crowded with potentially millions of satellites offering communications and computing services, efficient maneuvering capabilities will be essential for satellite operators to avoid collisions and manage their assets effectively. Portal's propulsion system is poised to provide this vital capability, catering to a diverse range of users in the burgeoning space economy.
