Seoul National University of Science and Technology Researchers Unveil New Comprehensive Safety Assessment Framework for Liquid Hydrogen Storage Systems in UAVs

The comprehensive assessment framework can lead to more widespread adoption of greener and more sustainable hydrogen propulsion system in UAVs

SEOUL, Sept. 23, 2025 /PRNewswire/ -- Aviation accounts for approximately 12% of global carbon dioxide emissions. With intensifying climate change and environmental issues, the aviation industry is searching for greener propulsion systems. For unmanned aerial vehicles (UAVs), research has turned towards hydrogen propulsion systems. Hydrogen is a clean fuel that produces only water during combustion, representing a promising alternative to conventional fossil fuels.

However, hydrogen has low volumetric energy density, meaning larger volumes are required to match the energy of conventional fuels. One solution is liquid hydrogen storage systems. While these systems reduce storage size and weight, they also present various challenges, including vessel deformation due to thermal stresses and fatigue failure. This is particularly risky in UAV operation conditions, which involve multi-directional acceleration loads. A comprehensive assessment of thermal performance and structural integrity in UAV operation conditions is, therefore, crucial.

To address this gap, a research team led by Assistant Professor Nak-Kyun Cho and Mr. Jinmyeong Heo from the Department of Manufacturing Systems and Design Engineering (MSDE) at Seoul National University of Science and Technology, Korea, in collaboration with Professor Nam-Su Huh from the Department of Mechanical System Design Engineering at the same university, developed the first integrated analytical framework for evaluating the performance and safety of liquid hydrogen storage tanks in UAVs. "Unlike existing studies that were limited to isolated thermal insulation performance or structural analyses, we have developed the first holistic system integrating thermal, structural, fatigue, and impact analyses, specifically tailored for UAV operations," explains Dr. Cho. Their study was made available online on June 09, 2025, and published in Volume 145 of the International Journal of Hydrogen Energy on July 07, 2025.

The team began by obtaining cryogenic properties of the materials used in the storage systems with the support of research funding and material testing and verification evaluation of the Hydrogen Materials Research Center at Korea Institute of Materials Science (KIMS). They considered a standard liquid hydrogen storage tank made of SUS316L steel for the main structure and Al6061-T6 aluminium for vapor-cooled shield (VCS) that reduce entry of heat into the system. Temperature-dependent properties of these materials were measured using a 100 kN tensile-fatigue testing system, and incorporated into finite element analyses of the vessel, covering thermal, structural, fatigue and drop impact assessments.

Thermal analysis revealed that the VCS implementation reduced the boil-off rate (BOR) by 30% in analysis and 15% in experiments. BOR is a key performance indicator that represents the rate at which stored liquid hydrogen evaporates. Structural analysis revealed pipes and supporters as the weak points under UAV-specific operational conditions, highlighting the need for structural modifications. Fatigue analysis showed that the vessel far exceeded the 10,000 cycle requirement specified in ISO 21029-1 standards, with an effectively unlimited fatigue life.

For drop impact testing, the team developed a new computer simulation method using a VUSDFLD subroutine-based element deletion approach that identified connecting pipes and supporters as vulnerable areas.

"Our findings establish new standards for comprehensive safety assessment of liquid hydrogen storage tanks in UAV applications," concludes Mr. Heo.

Reference

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