The journey from fuel tank to aircraft turbine

Liquid hydrogen is one of the energy carriers that could make aviation more climate-compatible in the coming decades. Despite the progress already made, there are still a number of physical hurdles to overcome and new technologies to develop before reduced-emission medium-haul flights can be powered by hydrogen. Researchers at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) are tackling this challenge at the newly built Future Propulsion Test Facility (FPT).

In 2024, researchers at the DLR Institute of Propulsion Technology in Cologne comprehensively demonstrated that aircraft engine combustion chambers can be operated safely on 100 percent gaseous hydrogen. However, a system for delivering hydrogen from the fuel tank to the combustion chamber - known as the distribution and conditioning system - and the required component technology, remain largely unexplored and fraught with challenges.

The culprit is liquid hydrogen (LH2). Compared to conventional jet fuel, it requires more space, higher pressure and, above all, it likes it cold - extremely cold. Gaseous hydrogen only liquefies at temperatures below minus 253 degrees Celsius, which engineers refer to as cryogenic temperatures. This temperature must be kept as constant as possible in the tank and throughout the entire distribution system right up to the engine, just before the combustion chamber - and this must be maintained at every stage of a flight, whether at cruising altitude with an outside temperature of minus 30 degrees Celsius, or on the tarmac in Kuala Lumpur, for example, at plus 40 degrees Celsius.

From shipping to aviation

Since no aviation-ready technology is currently available on the market, the solution lies in 'disruptive research' conducted by DLR in collaboration with researchers from other disciplines. Tanks, pumps, distribution networks and heat exchangers must be designed, built and tested on the ground under cryogenic conditions down to minus 253 degrees Celsius for use in aviation. DLR is accelerating the development of new technologies through its research and a hydrogen test infrastructure that simulates aviation operating conditions.

On its journey from tank to aircraft turbine, liquid hydrogen requires a pressure of up to 100 bar. To achieve this pressure, specialised pumps capable of operating under cryogenic conditions are required. "There was nothing comparable in the aviation industry - but there was in the shipping industry," explains project leader Christian Fleing, describing how the collaboration began with Italian firm Vanzetti, a company with many years of experience manufacturing pumps for maritime applications. The Messer Group contributed its expertise in cryogenic technology.

"Our tests serve to gather data and demonstrate that the concept works. This is the first step on a long journey - but the first step is often the most important one," adds Fleing. The tests carried out in February 2026 were at Technology Readiness Level 4 (TRL 4), involving the validation of components or prototypes in a laboratory environment. The data collected will now be used in computer simulations to work on scaling the system - adapting the test scale to the size actually required in aviation.

"With the current tests at our Future Propulsion Test Facility, we are doing something that has become rare in the work of aeronautical engineers: Instead of optimising an existing technology, we are researching the design and configuration of an entirely new technology," explains Florian Herbst, Director of the DLR Institute of Propulsion Technology.

Funding

The Future Propulsion Test Facility, completed in October 2025, was funded by the Project Management Agency for Aviation Research with resources from the UpLift Aviation Research Programme of the Federal Ministry for Economic Affairs and Energy (BMWE). UpLift supports the development of technologies aimed at achieving climate-neutral aviation.

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