In the wake of escalating climate concerns and the urgent call for sustainable energy alternatives, aviation—a sector responsible for roughly 12% of global CO2 emissions—faces immense pressure to transform its propulsion technologies. Among these advancements, hydrogen propulsion emerges as a compelling candidate, particularly for unmanned aerial vehicles (UAVs), which are becoming indispensable across military, agricultural, and logistics domains. By producing only water vapor upon combustion, hydrogen promises a clean, virtually emission-free energy source, thereby holding the potential to revolutionize aerial transportation. Yet, the practical challenges of harnessing hydrogen’s potential, especially its storage and safety within UAV systems, remain formidable barriers.
The low volumetric energy density of hydrogen complicates storage solutions, necessitating either substantial volumes or innovative containment strategies to deliver practical energy capacities. Liquid hydrogen storage systems, which maintain hydrogen at cryogenic temperatures to condense it into a liquid, offer the advantage of reduced volume and weight. However, this approach introduces a suite of complex engineering challenges. Storage vessels undergo severe thermal stresses due to drastic temperature gradients near absolute zero, leading to potential material deformation. Furthermore, UAV operational conditions impose highly dynamic loads, including multi-directional accelerations and impact events, raising concerns about the structural integrity and longevity of these cryogenic containers.
Addressing this multifaceted problem, a pioneering research group at Seoul National University of Science and Technology in South Korea has developed the first integrated analytical framework specifically tailored to evaluate liquid hydrogen storage systems in UAV applications. Led by Assistant Professor Nak-Kyun Cho and Ph.D. candidate Jinmyeong Heo from the Department of Manufacturing Systems and Design Engineering, in collaboration with Professor Nam-Su Huh of Mechanical System Design Engineering, this project represents a watershed moment in hydrogen fuel storage research. Unlike previous isolated assessments that focused narrowly on thermal insulation or static structural analysis, their framework synthesizes thermal, structural, fatigue, and drop impact analyses into a unified model precisely engineered for the severe operational regimes encountered by UAVs.
Fundamental to the project was the procurement and characterization of temperature-dependent cryogenic material properties, facilitated through collaboration with Korea Institute of Materials Science’s Hydrogen Materials Research Center. The primary storage vessel materials comprised SUS316L stainless steel for the inner and outer tanks, pipes, and supporting structures, known for its corrosion resistance and mechanical robustness at low temperatures. Complementing this, a vapor-cooled shield (VCS) fabricated from aluminium alloy Al6061-T6 was incorporated to minimize heat ingress. Mechanical properties at cryogenic temperatures, including tensile strength and fatigue limits, were experimentally determined through rigorous testing on a 100 kN tensile-fatigue apparatus, ensuring precise parameterization for subsequent computational simulations.
The research team employed advanced finite element analysis (FEA) methodologies to simulate complex thermal and mechanical behaviors under operational conditions. Thermal simulations underscored the efficacy of the vapor-cooled shield in reducing the boil-off rate (BOR) of liquid hydrogen by approximately 30% in theoretical evaluations, though empirical testing showed a somewhat moderated 15% reduction, attributed to differences between idealized conditions and real-world complexities. Such performance gains are critical, as BOR quantifies the rate at which cryogenic hydrogen is lost due to unavoidable heat transfer—directly impacting UAV range and mission durations.
Structural assessments within the integrated framework revealed critical stress concentrations and deformation risks localized at the pipes and support structures, areas often neglected in conventional designs. These findings emphasize the urgent necessity for engineering refinements aimed at reinforcing these vulnerable components to withstand dynamic UAV operating forces. In parallel, fatigue analysis indicated that the storage vessels dramatically exceed the 10,000 cycle threshold prescribed by ISO 21029-1 standards, suggesting that, under standard operating profiles, the tanks possess effectively unlimited fatigue life, a promising indicator for long-term UAV missions.
Perhaps most innovative was the team’s development of a novel computational approach to simulate drop impact scenarios using a VUSDFLD subroutine-based element deletion technique. This allowed accurate modeling of material failure and damage progression in multi-material assemblages when subjected to abrupt mechanical shocks such as accidental drops from operational heights. The simulation highlighted weaknesses in the connecting pipes and supporters, mirroring the structural analysis results and reinforcing these areas as priorities for design optimization.
“The comprehensive insights gleaned from this holistic framework serve as a new benchmark for safety and performance standards in liquid hydrogen storage for UAVs,” commented Mr. Heo. The establishment of a robust cryogenic materials database further extends the impact of their work, offering a valuable resource for future technological advancements not only in aerospace but potentially across broader engineering sectors where cryogenic systems are utilized.
This integrated analytical strategy opens avenues for further innovation in hydrogen-fueled UAVs, promising prolonged flight endurance, enhanced payload capacities, and rapid deployment capabilities essential for logistics and delivery sectors. More importantly, it heralds a decisive move towards greener aviation by mitigating one of the primary technical hurdles—safe and efficient hydrogen storage—paving the way for widespread adoption of environmentally sustainable UAVs powered by hydrogen.
The team’s work, published in the July 7, 2025, issue of the International Journal of Hydrogen Energy, provides the scientific community and industry stakeholders with a pivotal reference for hydrogen propulsion system design and safety validation. It underscores the vital interplay between material science, mechanical engineering, and computational simulation in addressing the nuanced challenges of cryogenic fuel technology.
As global demand for cleaner energy surges, such advancements underscore the crucial role of interdisciplinary research in driving the next generation of sustainable aviation technologies. Liquid hydrogen storage tanks, once a bottleneck in UAV design, are now poised for transformative improvements, thanks to this groundbreaking framework that ensures reliability, safety, and efficiency are harmonized under the most demanding operational criteria.
By addressing both fundamental material challenges and real-world operational stresses, this research significantly accelerates the transition toward a hydrogen economy in urban air mobility and unmanned system applications. The scalability of the framework may also inspire analogous solutions in other domains requiring extreme low-temperature storage, such as space exploration, cryogenic medical preservation, and high-capacity energy storage systems.
In summation, the convergence of precise material characterization, holistic structural analysis, and innovative simulation of impact events culminates in a robust, scientifically rigorous pathway toward realizing hydrogen’s promise as the sustainable fuel of the future for UAVs and beyond. The global aviation community will keenly watch how these findings influence regulatory standards, engineering practices, and the commercial viability of hydrogen-powered flight in the years to come.
Subject of Research: Not applicable
Article Title: Analytical framework for liquid hydrogen storage tanks in UAVs: Thermal performance validation and structural integrity assessment
News Publication Date: 7-Jul-2025
Web References:
https://doi.org/10.1016/j.ijhydene.2025.06.042
References:
DOI: 10.1016/j.ijhydene.2025.06.042
Image Credits:
Credit: Dr. Nak-Kyun Cho from Seoul National University of Science and Technology, Korea
Keywords
Hydrogen storage, Aerospace engineering, Low temperature physics, Mechanical engineering, Structural design, Aviation, Materials science, Hydrogen fuel
