A Turbineless Hybrid Electric-Hydrogen Propulsion System with On-Demand Aluminum-Water Hydrogen Generation: Design and Static Thrust Characterization

This study presents a turbineless hybrid electric-hydrogen propulsion system developed and tested under static conditions. Two electric ducted fans (EDFs) provided the baseline thrust and combustion airflow, while hydrogen was generated on demand in an alkaline aluminum-water reactor and burned downstream of the fans. Hydrogen production was regulated by changing aluminum-rod immersion depth and measured directly at each operating condition with a hydrogen-calibrated mass-flow meter; aluminum consumption was additionally recorded to characterize the effective hydrogen yield. Static performance was evaluated at ten immersion-depth conditions using 76 independent paired EDF-only and hybrid runs per condition. At the highest tested hydrogen flow, thrust increased from 8.49 ± 0.15 to 9.94 ± 0.21 N, a 17.1% increase over the matched EDF-only baseline. Hydrogen production varied approximately linearly with exposed aluminum surface area (R² = 0.997), while marginal thrust gain decreased as hydrogen flow increased. The momentum-based combustion-to-jet conversion indicator remained between approximately 8.0 and 9.4%, with its highest observed values over a region of intermediate hydrogen flow rates. Chamber-pressure measurements provided an independent consistency check of the thrust increment. Supplementary cold-flow measurements provided a total two-fan electrical reference of approximately 1.33 kW. An endpoint exergy assessment estimated a lower jet-kinetic-power fraction of the combined electrical and hydrogen chemical inputs at higher hydrogen flow.