H₂ aircraft 200 Kilometer Range: Switzerland's First Hydrogen-Powered Aircraft

Every gram counts when it comes to zero-emission flight: Busch’s Mink MH recirculation blower reduces hydrogen consumption in ETH Zurich’s H2-Sling research aircraft. By precisely recirculating unburned fuel back to the anode, the range and efficiency are increased—crucial factors for the planned flight across the Alps.

According to the German Aerospace Center, more than 36 million flights took off in 2024, making air travel responsible for about 2.1% of global CO2 emissions. This is roughly equivalent to the total annual emissions of a country like Germany. New technologies are needed to reduce the climate impact of aviation and make air travel significantly more environmentally friendly in the future. And Busch vacuum solutions are being used in research into precisely these technologies. 

According to a report by the Office for Technology Assessment (TAB) of the German Bundestag, short-term innovations in the area of sustainable fuels make the most sense, since fuel consumption is the most important driver of aviation’s climate impact.

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Hydrogen, in particular, offers great potential as a clean aviation fuel. In its report, however, the TAB also points out that storing hydrogen in aircraft poses a technical challenge, as it requires large, insulated tanks maintained at a temperature of minus 253 degrees Celsius. These tanks are very heavy. Overcoming these and other challenges will require further research and technological advancements in today’s aircraft and infrastructure. 

A group of Swiss students, organized under the Cellsius association, has now developed a small aircraft powered exclusively by hydrogen. Cellsius is a nonprofit organization founded in 2022 that is dedicated to research into sustainable aviation. Here, students at ETH Zurich in their final year of their bachelor’s program can put the knowledge they’ve acquired into practice. 

As part of this project, they developed the so-called H2-Sling: an aircraft powered by gaseous hydrogen. The Mink MH hydrogen recirculation blower ensures efficient recirculation of the hydrogen; Busch Vacuum Solutions donated this blower to ETH Zurich to support the research project and advance technological progress.

Switzerland's First Hydrogen-Powered Aircraft

The aircraft itself is powered by a 100-kilowatt fuel cell system. Since water is the only byproduct of the reaction, no climate-damaging greenhouse gases are emitted into the atmosphere during flight. The hydrogen is stored in two tanks located beneath the aircraft’s wings, each with a capacity of 2.6 kilograms. Because hydrogen has a high energy density, this amount gives the aircraft a range of 200 kilometers, which corresponds to approximately two hours of flight time. The aircraft was unveiled and first presented to the public in October 2025. It is now awaiting certification from the Swiss Federal Office of Civil Aviation so that the first test flight can take place in the spring of 2026. The ultimate goal: a flight across the Alps. 

How does a fuel cell work?

In a fuel cell, an electrochemical reaction between hydrogen and oxygen generates electricity and heat. The cell consists of two electrodes separated by an electrolyte membrane: an anode and a cathode. The membrane is responsible for ion transport. 

Hydrogen enters on the anode side. The hydrogen molecules are split into protons and electrons. The hydrogen protons diffuse through the membrane to the cathode, where they react with oxygen from the ambient air to form water, releasing energy in the process. An electric motor then uses this energy, for example, to drive an airplane’s propeller. 

What is the effect of recirculation?

For the fuel cell to operate reliably, the chemical reaction must be sustained by a carefully controlled supply of hydrogen and air. The Mink MH recirculation blower from Busch ensures that unreacted hydrogen is not lost but is reused.

Here’s how it works: More hydrogen is supplied from the high-pressure tanks beneath the wings than is actually needed to ensure a stable chemical reaction in the fuel cell. This prevents local “depletion”—an effect that occurs when the concentration of the reactant in the cell drops so low that the reaction cycle ultimately comes to a halt.

Due to the excess supply, hydrogen remains after the reaction ends. If this residual hydrogen were not utilized, even larger hydrogen tanks would be required. This would increase the aircraft’s weight and reduce its performance. To maximize flight time and range, the unused hydrogen must therefore be recycled.  

Recirculation fan specifically designed for fuel cells

To do this, the reactant must be directed from the fuel cell’s anode outlet back to its inlet. This is where Busch’s Mink MH comes into play: Two claw-shaped rotors rotate in opposite directions inside the compressor housing. The rotation of these claw rotors draws in the hydrogen, compresses it, and then returns it to the fuel cell’s anode, where it mixes with fresh hydrogen from the tank. This allows the reaction cycle to continue without interruption. Reusing unreacted hydrogen minimizes fuel consumption and conserves resources. 

The TÜV-certified recirculation fan was developed specifically for use in fuel cells. “Busch is one of the few providers of solutions for hydrogen fuel cells. We’ve already had very good experiences with the smaller version of the Mink MH, which we installed in a test cycle,” explains Andres Neff, technical director of the H2-Sling project. “Everything worked perfectly in this test system, and the blower is very user-friendly. That’s why we were very pleased to be able to use the larger version of the blower for our project.”