The PBR-20 (Water Resistojet Thruster) is a compact 1U water vapor propulsion system optimized for 6U–8U CubeSats. It is a fully integrated solution that incorporates the thruster head, fluidics, electronics, and propellant tank within a single unit. Its clusterable architecture also enables scalability across a wide range of spacecraft sizes and mission requirements.

The PBR-20 uses water as propellant, eliminating the need for high-pressure storage systems. The propellant is preloaded into the tank prior to factory delivery, allowing satellite integrators to avoid complex fueling procedures during spacecraft integration.

The propulsion system first demonstrated successful operation in low Earth orbit in March 2023. Its reliability was further validated through a second in-orbit operation in January 2025 aboard Sony’s first satellite, EYE.