Airplanes hover on the water

The hydrogen airplane is taking shape

The latest aircraft design from Airbus does not look like an aviation revolution, floating in the cloudless sky to spherical music. On closer inspection, it is noticeable that there are no windows in the rear third of the fuselage of the Airbus aircraft study. On top of the tail unit there is a short extension that looks more like an antenna. These characteristics indicate that this is indeed a potentially groundbreaking novelty.

"The hydrogen tank is located in the rear third of the fuselage behind the pressure bulkhead of the cabin, and the extension at the top of the tail unit is used to vent gas in the event of a leak," said Airbus technology director Grazia Vittadini when the first drafts of future-oriented aircraft were presented Hydrogen propulsion. The goal is ambitious: Airbus wants to bring out the world's first emission-free commercial aircraft by 2035.

"Historic Moment"

The European manufacturer has three different concepts, one of which is to be implemented, including the more conventional-looking jet. Under strong political pressure, especially from France and Germany, Airbus wants to lead the transformation in order to promote the move away from fossil fuels and thus decarbonization for aviation. Germany has already developed its own hydrogen strategy, and France announced at the beginning of the month that it would invest seven billion euros in hydrogen technology over the long term. The move by Airbus fits exactly into the picture.

One of three variants: The turbofan concept (computer animation)

"This is a historic moment for all of commercial aviation," said Airbus CEO Guillaume Faury of his "bold vision". Head of Technology Vittadini emphasizes that these "exciting concepts are also intended to inspire future generations of engineers."

Not a new idea

The idea of ​​using hydrogen instead of kerosene as an energy source for aircraft engines is not new, but it is still difficult to implement. As a result, there has been a lack of commercially viable aircraft concepts that are suitable for everyday use. Because hydrogen is not easy to care for: it has three times the energy density compared to kerosene - a major advantage over batteries - and weighs only a third as much, but requires up to four times more volume than conventional fuel. And space on board aircraft is notoriously scarce and precious.

In addition, and this makes it particularly challenging, hydrogen is a so-called cryogenic fuel: a gas that can only be used as a liquid and compressed under high pressure for drives at minus 253 degrees Celsius. Which in turn requires a double-walled, cylindrical or spherical tank. As early as 1988, engineers in what was then the Soviet Union brought out a modified version of their three-engine Tupolev TU-154 passenger jet; they named the test aircraft TU-155, the right engine of which was powered by hydrogen. Hydrogen can be used in various ways for aircraft: for direct combustion in converted gas turbines, converted into electrical energy by fuel cells, or it can be used to produce synthetic kerosene in combination with CO2.

The turboprop version of the concept aircraft in the computer animation

Not for transatlantic flights

"We have to redesign the aircraft around these conditions," says Grazia Vittadini. Airbus is now trying to do this with a trio of suggestions. The so-called turbofan design described at the beginning, which is supposed to carry 120 to 200 passengers over distances of around 3700 kilometers, so it does not manage long-haul or transcontinental flights in America, but all intra-European routes. The concept is a little smaller than the current base model A320neo, which flies at Lufthansa, for example, but reaches the same speed with a good 800 km / h even when powered by hydrogen.

The second design is a turboprop aircraft with propeller drive for up to a hundred passengers on short journeys, which, at a good 600 km / h, would be around a hundred kilometers per hour faster than today's turboprops. Both designs are powered by modified gas turbines, supplemented by a hybrid electric motor powered by fuel cells, and deliberately kept conventional. "We don't have to invest in completely new technologies for this," explains Airbus boss Faury.

There is also a disruptive concept - a hydrogen-powered flying wing, the so-called Blended wing body. Here the wings and fuselage form a continuous aerodynamic body. This configuration, most recently presented by KLM and TU Delft with their Flying V concept, is already considered to have a promising future. "The flying wing is aerodynamically the most advantageous model for integrating the hydrogen tanks," Grazia Vittadini told DW. "But that doesn't mean that this is also the optimal solution for the other parameters."

Computer animation of the Flying V model from KLM and TU Delft

Not entirely emission-free

The Airbus initiative is also well received in science. "The world is ripe for it and Airbus has seized the opportunity," Dragan Kozulovic, professor of aircraft engines at the Hamburg University of Applied Sciences (HAW) told DW. It is remarkable that the studies managed entirely without kerosene, and the planned market launch by 2035 is quite realistic.

Kozulovic considers the realization of the design of the hydrogen-powered turboprop aircraft to be the most likely. The decisive factor for success, however, is that the necessary infrastructure on the ground for the commercial use of hydrogen is created, from production to storage and refueling, "that is a mammoth task".

Hydrogen is only sustainable if it is produced using green electricity from solar or wind energy, for example. The professor defends himself against the labeling of the ZEROe named Airbus concepts as "emission-free". Because even without CO2 generation, the combustion of hydrogen continues to produce water vapor as an emission, which triggers climate-relevant contrails in the sky. Nitrogen oxides would also continue to be released. "These aircraft would be much better, but not emission-free," explains Dragan Kozulovic.

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