By Bjorn Fehrm
February 14, 2025, ©. Leeham News: We do a Corner series about the state of developments to replace or improve hydrocarbon propulsion concepts for Air Transport. We try to understand why the development has been slow.
We have covered the progress of battery-based aircraft and hybrids. Last Corner started looking at hydrogen-fueled alternatives. A day after the Corner, the Airbus workers union Force Ovrier published information from an Airbus internal meeting, in which the airframer delayed the introduction of a hydrogen aircraft by 2035 to about 10 years later. As a consequence, it reduces the R&D spending on the development of hydrogen propulsion technologies.
Figure 1. The Airbus ZEROe concepts. Source: Airbus.
The Hydrogen Echo System
The reason given at the internal meeting was that the supply ecosystem of green hydrogen is developing slower than anticipated, including the hydrogen production, distribution, and availability at relevant airports.
Since the start of the Airbus ZEROe hydrogen-focused alternative propulsion project (Figure 1), it’s been clear that the air transport market cannot lead the transition to hydrogen. The volumes are too small, just as they are for the development of aircraft battery technology.
The development of the key elements of batteries and hydrogen for transport applications has to be led by the huge ground transport market, the air transport market is too small.
Figure 2. The Mercedes liquid hydrogen fuel cell truck runs 1,000km on one tank. Source: Mercedes Truck.
The project that would lead the transition to liquid hydrogen for transport applications would be the long-haul truck industry, Figure 2. The truck industry has converged on battery-electric trucks for local distribution, where these can be charged overnight and then deliver goods during the day.
Also, some longer-haul trucking, such as trucking between urban areas, can be battery-electric if the fast-charging infrastructure is available. But real long-haul truck transport can’t function with the need to charge 30 minutes or more several times daily.
This is where the largest truck supplier, Mercedes, has developed liquid hydrogen fuel-cell electric trucks and tested them on long routes over the last years. Figure 2 shows a test run from 18 months ago, in which a fully loaded 40-tonne Mercedes truck was charged with 80 kg of liquid hydrogen at Woerth in Germany and then ran the 12-hour Autoban trip to Berlin, 1,000 kilometers (620 miles) away, without refueling.
The transition from diesel trucks to battery or hydrogen trucks has just started (it trails the change to battery-electric cars). This change has to happen before the investment in the production and distribution of hydrogen for air transport can happen.
Only then can air transport latch on. So it’s not a matter of air transport not wanting to change; it can’t change unless the much larger and more important change in ground transport happens.
The same stark reality is true about the aircraft battery system. Aircraft startups that have bet on battery-electric concepts have universally found that their capacity doesn’t allow a sensible design of a short-haul aircraft or anything but an ultra-short-haul eVTOL flying the 10-minute mission from an airport to a city center.
Those who promised too much had to bet on special battery chemistries (Lilium is one), which has consumed a vast amount of R&D money for the energy store. As predicted, these projects are running out of money as we speak (Lulium is not out of insolvency, CityAirbus is frozen because of batteries, and eViation is going into hibernation…).
When the craze started around hydrocarbon propulsion alternatives some eight to 10 years ago, we published this Gartner Hype Cycle curve, which describes the typical cycle around new technology advancements.
Figure 2. The Gartner hype cycle curve with a year-scale added by me. Source: Gartner Inc.
This is the Gartner hype curve of the Corner from April 10, 2020, where I daringly put years underneath the curve. The recent announcements of the demise of several alternative propulsion projects, where we said five years ago this would happen, are pretty spot on.
So, we have now passed the “Peak of Inflated Expectations” and are on our way down the “Through of Disillusionment.” Are we at the bottom? Most likely not. We will be there in 2026 or 2027 when the first operational eVTOLs start flying and the naive business cases go up in smoke. That is the negative part.
It is essential to understand that once we get past this, around 2030, we will see real progress and viable alternative propulsion solutions with a useful range for battery electric aircraft and eVTOLs and the emergence of functional hydrogen supply for the longer-range hydrogen solutions.
The subject of the Corner changed
We should have started covering the hydrogen burn solution this week, but given the development since the autumn and especially the Airbus news from last week, a pause was needed to put it all in perspective.
We have been critical of overinflated expectations for 10 years now. However, this doesn’t mean we don’t believe in a change to more environmentally friendly propulsion solutions.
It’s just, you have to put pen to paper and check all the wild statements that have been circulated. We didn’t even have to employ our sophisticated Aircraft Performance and Cost Model (APCM) to punctuate these claims. A simple check using first principles sufficed.
Next week, we continue with hydrogen burn.
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