Periodic Reporting for period 4 - fLHYing tank (flight demonstration of a Liquid HYdrogen load-bearing tank in an unmanned cargo platform)
Période du rapport: 2025-01-01 au 2025-12-31
The fLHYing Tank project was conceived in response to the urgent need for lightweight, efficient, and certifiable liquid hydrogen (LH2) storage solutions in aviation - an essential enabler for achieving the EU’s climate neutrality goals.
The project aimed to design, manufacture, and flight-test a 1,000-liter, flight-load-bearing, vacuum-insulated composite LH2 tank onboard the Pipistrel Nuuva V300 cargo UAV. This approach was disruptive in several ways:
- It targeted the end-to-end development and qualification of a relevant-scale, fully composite LH2 tank.
- It proposed a fast-track flight-testing methodology using UAVs to safely accelerate the validation of low-TRL, high-risk technologies.
- It introduced a digital twin framework—a fluid-dynamic, thermal, and structural model calibrated with real flight data—to support future digitalized certification pathways for hydrogen technologies.
By focusing on rapid knowledge acquisition through real-world flight testing, the project sought to dramatically reduce the time-to-market for revolutionary hydrogen storage systems.
The fLHYing Tank project was designed to deliver strategic impact by:
- Supporting the Clean Aviation Programme’s Phase 1 goals.
- Contributing to the REPowerEU and Fit for 55 packages by enabling hydrogen-powered flight.
- Providing a scalable and certifiable LH2 storage solution for future zero-emission aircraft.
Although the project was ultimately terminated due to the unavailability of a suitable tank development partner—a result of budget and timeline constraints—it remains a highly relevant and strategically aligned initiative.
The project aimed to design, manufacture, and flight-test a 1,000-liter, flight-load-bearing, vacuum-insulated composite LH2 tank onboard the Pipistrel Nuuva V300 cargo UAV. This approach was disruptive in several ways:
- It targeted the end-to-end development and qualification of a relevant-scale, fully composite LH2 tank.
- It proposed a fast-track flight-testing methodology using UAVs to safely accelerate the validation of low-TRL, high-risk technologies.
- It introduced a digital twin framework—a fluid-dynamic, thermal, and structural model calibrated with real flight data—to support future digitalized certification pathways for hydrogen technologies.
By focusing on rapid knowledge acquisition through real-world flight testing, the project sought to dramatically reduce the time-to-market for revolutionary hydrogen storage systems.
The fLHYing Tank project was designed to deliver strategic impact by:
- Supporting the Clean Aviation Programme’s Phase 1 goals.
- Contributing to the REPowerEU and Fit for 55 packages by enabling hydrogen-powered flight.
- Providing a scalable and certifiable LH2 storage solution for future zero-emission aircraft.
Although the project was ultimately terminated due to the unavailability of a suitable tank development partner—a result of budget and timeline constraints—it remains a highly relevant and strategically aligned initiative.
- The requirements for the liquid hydrogen storage and distribution system were defined and finalized during the System Requirements Review.
- Comprehensive safety assessments were conducted at the aircraft level, covering liquid hydrogen handling procedures as well as ground and flight testing activities.
- Thermal, fluid-dynamic, and structural evaluations were carried out on various liquid hydrogen tank configurations, providing critical insights that informed system architecture decisions.
- Multiple architectural solutions at the system, subsystem, and component levels were proposed and systematically cross-evaluated.
- A material screening campaign was conducted to assess the permeability of composite samples following immersion in liquid hydrogen, yielding valuable data on material behavior and permeability changes due to LH2 exposure.
- The risk of rapid vacuum loss was identified as a critical concern. Technical and project-level evaluations of mitigation strategies were performed by the consortium, ultimately leading to a decision to switch to a Type III tank with proven vacuum tightness, which also necessitated a change in project - partners.
- In parallel, alternative motion testing methods were explored to supplement or replace UAV-based testing. These included helicopter-based testing (via sling load or cargo cabin), ground vehicle testing (using rail systems or cargo vans), and simulations using a 6-DOF platform (hexapod). These approaches were established as contingency options in the event UAV testing was not feasible.
- Comprehensive safety assessments were conducted at the aircraft level, covering liquid hydrogen handling procedures as well as ground and flight testing activities.
- Thermal, fluid-dynamic, and structural evaluations were carried out on various liquid hydrogen tank configurations, providing critical insights that informed system architecture decisions.
- Multiple architectural solutions at the system, subsystem, and component levels were proposed and systematically cross-evaluated.
- A material screening campaign was conducted to assess the permeability of composite samples following immersion in liquid hydrogen, yielding valuable data on material behavior and permeability changes due to LH2 exposure.
- The risk of rapid vacuum loss was identified as a critical concern. Technical and project-level evaluations of mitigation strategies were performed by the consortium, ultimately leading to a decision to switch to a Type III tank with proven vacuum tightness, which also necessitated a change in project - partners.
- In parallel, alternative motion testing methods were explored to supplement or replace UAV-based testing. These included helicopter-based testing (via sling load or cargo cabin), ground vehicle testing (using rail systems or cargo vans), and simulations using a 6-DOF platform (hexapod). These approaches were established as contingency options in the event UAV testing was not feasible.
- Innovative tank system architectures were developed, accompanied by comprehensive trade-off studies.
- The layout for flight test instrumentation aimed at tank data collection, along with the associated flight test requirements, was formulated.
- The permeability of three novel composite materials for cryogenic tanks was characterized following exposure to liquid hydrogen (LH2), contributing new insights into their behavior under such conditions.
- Computational methodologies were developed, verified, and calibrated for calculating structural and thermal stresses in laminated and filament-wound composites.
- Interlaminar stresses were derived with sufficient accuracy to predict potential delamination damage.
- A reduced-order thermodynamic model was formulated to provide a more detailed representation of evaporation under static conditions.
- New insulation materials and strategies were evaluated, including low-density aerogels and various polymer foams.
- A spray model was implemented to simulate tank bunkering, incorporating several state-of-the-art heat transfer correlations.
- The layout for flight test instrumentation aimed at tank data collection, along with the associated flight test requirements, was formulated.
- The permeability of three novel composite materials for cryogenic tanks was characterized following exposure to liquid hydrogen (LH2), contributing new insights into their behavior under such conditions.
- Computational methodologies were developed, verified, and calibrated for calculating structural and thermal stresses in laminated and filament-wound composites.
- Interlaminar stresses were derived with sufficient accuracy to predict potential delamination damage.
- A reduced-order thermodynamic model was formulated to provide a more detailed representation of evaporation under static conditions.
- New insulation materials and strategies were evaluated, including low-density aerogels and various polymer foams.
- A spray model was implemented to simulate tank bunkering, incorporating several state-of-the-art heat transfer correlations.