WAVE-XS: Water-Based Micropropulsion for Smallsats

Europe’s rapid smallsat scaling is increasing demand for propulsion that is safe to handle, simple to integrate, and operationally useful across the full mission lifecycle—including collision-avoidance maneuvers and end-of-life deorbit. This paper presents WAVE-XS, a water-centered micropropulsion architecture for CubeSats and small spacecraft that uses stored liquid water as the only consumable and converts it into gaseous H₂/O₂ on demand for pulsed chemical thrust.

WAVE-XS is designed as a modular subsystem comprising a compact water tank, a PEM electrolyzer, gas management and drying stages, dual gas plenums sized to the stoichiometric 2:1 H₂:O₂ volume ratio, isolation and metering valves, ignition hardware, sensors, and a nozzle optimized for small-thruster packaging (baseline expansion ratio ~12). A moderate storage pressure regime (baseline ~50 psi target) is selected to balance component availability, safety, and repeatable pulse performance for laboratory validation. Particular attention is placed on real integration and reliability issues that often dominate smallsat adoption: residual water carryover, condensation control, gas purity, startup priming, valve timing repeatability, spark energy budgeting, and inhibit logic for safe handling and launch operations.

We outline an incremental verification plan using an integrated test-stand controller to characterize gas output stability and dryness, validate impulse-bit repeatability under pulsed operation, and execute hot-fire testing to map thrust, transient behavior, and endurance. Representative mission use cases are provided for LEO station-keeping and end-of-life disposal planning, showing how a single-fluid consumable can simplify propellant logistics while improving mission assurance. Future work discusses extension to eclipse-resilient energy cycling via a regenerative fuel-cell “water battery” module for longer-duration operations.