flight demonstration of a Liquid HYdrogen load-bearing tank in an unmanned cargo platform

Informations projet

fLHYing tank

N° de convention de subvention: 101101946

DOI

10.3030/101101946

Projet clôturé le 22 Avril 2025

Date de signature de la CE 9 Decembre 2022

Date de début 1 Janvier 2023

Date de fin 31 Decembre 2025

Financé au titre de

• Climate, Energy and Mobility

Coût total

€ 3 947 691,25

Contribution de l’UE

€ 2 998 491,25

Coordonné par

PIPISTREL VERTICAL SOLUTIONS DOO PODJETJE ZA NAPREDNE LETALSKE RESITVE
Slovenia

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

Résumé du contexte et des objectifs généraux du projet

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.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

- 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.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

- 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.