Analytical Modelling and Parametric Optimization of Hybrid Hydrogen-Electric Propulsion for Long-Endurance UAVs

This study presents a clear and analytically explicit framework for exploring hybrid hydrogen–electric propulsion in micro-to-small fixed-wing unmanned aerial vehicles (UAVs). By combining classical lift–drag relationships with a first-principles energy balance, the model expresses flight endurance and range through simple, closed-form relations involving hydrogen mass, battery capacity, and cruise speed. Unlike approaches that rely on computationally intensive CFD simulations or extensive hardware testing, the framework is entirely physics-based, enabling fast, transparent, and reproducible performance estimation during early design stages. A parametric design-space analysis examines how mass allocation between hydrogen and battery storage influences endurance and range. Under idealized, constant-mass and constant-efficiency assumptions, the analytical model predicts that balanced hybrid configurations can yield theoretical endurance values approaching 70 hours and ranges on the order of 3700 km, representing a substantial improvement relative to battery-only operation. Contour-based visualization illustrates trade–offs associated with hybridization ratios and cruise conditions, providing intuitive insight into system-level behaviour. Owing to its simplicity, interpretability, and open analytical structure, the framework serves as a practical conceptual-design tool for UAV sizing, propulsion planning, and sustainable long-endurance flight studies. The model supports early-stage decision-making by offering a physics-grounded means of exploring hybrid UAV performance trends prior to more detailed analyses.