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

Aswin Karkadakattil

doi:10.2478/tar-2026-0001

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

Transactions on Aerospace Research

Volume 2026 (2026): Issue 1 (March 2026)

By: Aswin Karkadakattil

Open Access

|Mar 2026

Figures & Tables

Functional architecture of the hybrid hydrogen–electric propulsion system assumed in the analytical model.

Conceptual layout and mass distribution of the baseline micro-to-small fixed-wing UAV assumed in the analytical model.

Range versus battery mass for different hydrogen loadings at a cruise speed of 25 m s-1.

Predicted endurance as a function of cruise speed for multiple hybrid hydrogen–electric configurations.

Contour map of predicted range as a function of battery mass and hydrogen mass at 25 m s-1.

Normalized range improvement of hybrid configurations relative to a battery-only UAV baseline.

Propulsive power requirement as a function of cruise velocity predicted by the analytical model.

Hybrid power-sharing characteristics during steady cruise flight predicted by the analytical model. (a)Fractional contribution of fuel-cell and battery power as a function of airspeed. At low and moderate velocities, the fuel cell supplies nearly the entire propulsive power demand, reflecting its role as the primary continuous energy source. As airspeed increases and aerodynamic power requirements grow, the battery contributes an increasing share of the total power, consistent with a hybrid operating strategy in which the battery provides transient or peak-power support while the fuel cell maintains baseline power delivery. (b)Hybridization ratio (γ) as a function of cruise velocity. The hybridization ratio, defined as the fraction of required propulsive power supplied by the fuel cell, remains close to unity at low speeds and decreases smoothly with increasing velocity as battery contribution rises. Values around γ ≈ 0.6 indicate a balanced hybrid operating regime in which battery loading is moderated while efficient utilization of the fuel cell is maintained. The smooth, monotonic trend reflects the internal consistency of the energy-sharing formulation adopted in the analytical model.

Mission-level energy utilization and endurance characteristics predicted by the analytical framework. (a)Energy contribution of the hydrogen fuel cell and battery over a representative mission segment, illustrating the dominant role of hydrogen in long-duration energy supply and the supporting function of the battery for transient loads. (b)Stacked comparison of total usable energy provided by each energy-storage subsystem, highlighting the relative contributions assumed in the hybrid architecture. (c)Endurance map as a function of battery mass and hydrogen mass, showing smooth scaling with hydrogen loading and diminishing returns for battery-dominated configurations. All results are derived under steady-cruise and constant-efficiency assumptions and are intended for conceptual comparison.

Endurance map as a function of battery mass and hydrogen mass predicted by the analytical framework.

Representative Hybrid UAV Performance Results (Analytical Predictions)_

Battery (kg)	H₂ (kg)	Endurance (h)	Range (km)	Power (kW)	Improvement (%)
3.0	0.00	3.2	100	0.41	—
3.0	0.25	18.9	720	0.43	620
3.0	0.50	35.2	1400	0.44	1300
3.0	1.00	68.0	3700	0.46	3000

Comparison of analytically predicted cruise-power requirements with representative values reported for small UAV platforms_

UAV System	Reported Cruise Power	Model Prediction	Deviation
DJI Matrice 600 (hexarotor)	0.4–0.6 kW	0.45 kW	< 10%
Hydrogen–Electric Fixed-Wing UAV [1]	180–220 W	195 W	< 8%

j_tar-2026-0001_tab_005

Symbol	Description	Value / Range	Unit
ρ	Air density	1.225	kg m^-3
S	Wing area	1.2	m²
C_D0	Zero-lift drag coefficient	0.025	—
k	Induced-drag factor	0.045	—
η_prop	Propeller efficiency	0.85	—
η_em	Motor efficiency	0.90	—
η_fc	Fuel-cell efficiency	0.60	—
ρ_batt	Battery energy density	230	Wh kg^-1
LHV_H₂	Hydrogen lower heating value	1.20 × 10⁸	J kg^-1
V	Cruise velocity	15-35	m s^-1
m_batt	Battery mass	1-5	kg
m_H2	Hydrogen mass	0-1	kg

Reference Model Parameters Used in the Analytical Framework_

Parameter	Symbol	Value	Unit	Source / Note
Air density (sea-level reference)	ρ	1.225	kg m^-3	ISA reference (adjusted in simulations)
Wing area	S	1.2	m²	Typical micro-UAV configuration
Zero-lift drag coefficient	C_D0	0.025	—	UAV aerodynamic literature
Induced drag factor	k	0.045	—	Empirical aerodynamic constant
Propeller efficiency	η_prop	0.85	—	Assumed constant (conceptual level)
Fuel-cell efficiency	η_fc	0.60	—	Typical PEM system
Motor efficiency	η_em	0.90	—	BLDC motor
Battery energy density	ρ_batt	230	Wh kg^-1	Commercial Li-ion cells
Hydrogen lower heating value	LHV_H2	120 × 10⁶	J kg^-1	ISO standard
Structural mass (reference literature scaling value)	m_struct	10	kg	Representative UAV sizing
Payload mass (reference literature scaling value)	m_payload	2	kg	Generic sensor payload

Baseline UAV Mass Breakdown Used in the Parametric Study_

Component	Symbol	Value (kg)	Notes
Structural mass	m_struct	0.85	Wing, fuselage, empennage
Payload	m_payload	0.10	Small camera or sensor
Fuel-cell stack	η_fc	0.18	150–200 W PEM system
Hydrogen tank	m_tank	0.25	Type-IV,700 bar (≈5:1 tank:H₂)
Hydrogen mass	m_H₂	0.05	≈6 wt% of tank assembly
Battery pack	m_batt	0.20	Peak-power support
Avionics + ESC	m_elec	0.07	Flight control and wiring
Electric motor	m_motor	0.12	BLDC motor
Total mass	m_total	1.82	Used in analytical calculations

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DOI: https://doi.org/10.2478/tar-2026-0001 | Journal eISSN: 2545-2835

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Language: English

Page range: 1 - 37

Submitted on: Oct 10, 2025

Accepted on: Jan 9, 2026

Published on: Mar 14, 2026

Published by: ŁUKASIEWICZ RESEARCH NETWORK – INSTITUTE OF AVIATION

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

Hybrid hydrogen–electric propulsion,

Fuel-cell-powered UAVs,

Physics-based analytical modelling,

Endurance and range analysis,

UAV energy systems,

Conceptual aircraft performance,

Sustainable aviation concepts thrust-to-weight ratio,

Related subjects:

Introductions and overviews,

Materials sciences, other,

Physics,

Physics, other

© 2026 Aswin Karkadakattil, published by ŁUKASIEWICZ RESEARCH NETWORK – INSTITUTE OF AVIATION
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Volume 2026 (2026): Issue 1 (March 2026)

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

Figures & Tables

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Representative Hybrid UAV Performance Results (Analytical Predictions)_

Comparison of analytically predicted cruise-power requirements with representative values reported for small UAV platforms_

j_tar-2026-0001_tab_005

Reference Model Parameters Used in the Analytical Framework_

Baseline UAV Mass Breakdown Used in the Parametric Study_

Paradigm

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