Portal Becomes First Commercial Company to Successfully Test Solar Thermal Propulsion System for Multi-Orbit Spacecraft

Portal Space Systems has successfully tested its proprietary Heat Exchanger (HEX) Thruster, named Flare, in vacuum - the first commercial demonstration of a solar thermal propulsion system which will power the company’s rapid maneuverability and multi-orbit Supernova spacecraft. 

SEATTLE, WA — SEPTEMBER 30, 2025 — In a first for the commercial space industry, Portal Space Systems has successfully tested a solar thermal propulsion (STP) system at operational temperatures inside a vacuum chamber - validating the core technology powering Supernova, Portal’s next-generation, multi-role spacecraft built for space superiority through rapid maneuverability and long-duration missions. 

The test campaign, conducted at Portal’s Bothell, WA facility, demonstrated full-power, high-temperature operation of the company’s patented, 3D-printed heat exchanger (HEX) thruster, confirming predicted performance under flight-like conditions. Named Flare, this HEX Thruster will enable maneuverability from LEO to MEO in a few hours, MEO to GEO in under a day, and LEO to Cislunar space in just a few days all using a single, non-cryogenic, storable monopropellant: ammonia. 

“With maneuverability becoming a defining advantage in space operations, Supernova is built to give national security and commercial operators the ability to reposition, respond, and persist across orbits,” said Jeff Thornburg, CEO of Portal Space Systems. “This propulsion system unlocks mission tactics and timelines that traditional chemical or electric systems simply can’t support.” 

While solar thermal propulsion has been studied and under experimentation since the 1960s by NASA and the Air Force, it has remained for the most part a research effort. Portal is the first commercial company to bring the concept to life in a flight-representative environment by leveraging additive manufacturing, advanced materials, and a novel heat exchanger to make STP viable for real-world missions. 

Unlike traditional systems built to hold position, Supernova is designed to move - supporting real-time responsiveness and persistent presence across LEO, MEO, GEO, and Cislunar orbits. With no combustion required and using a non-cryogenic propellant, Portal’s propulsion architecture also supports refuelability and an over 5-year life on orbit, giving operators greater flexibility without added complexity. 

What Was Achieved During Test 

• Full-power test of Portal’s HEX Thruster (Flare) in vacuum 
• High-temperature performance of patented, 3D-printed heat exchanger 
• Predicted thrust and Isp verified under flight-representative conditions 
• Fully instrumented campaign including cold flow, calibration, and high-temperature sequences 
• Facility brought online to simulate solar energy via high-power electric heating 
• Propulsion architecture validated for integration with future flight hardware 

About Portal Space Systems 

Portal Space Systems is a next-generation spacecraft company headquartered in Washington state. The company builds reconfigurable, maneuverable spacecraft designed to support defense and commercial missions on operational timelines. Portal emerged from stealth in 2024, earned STRATFI support, raised one of the largest publicly announced seed rounds in the sector, and was named a Via Satellite “Top 10 Startup to Watch.” 

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