Aviation Week editors are joined by special guest Martha Neubauer, a senior associate at AeroDynamic Advisory, to discuss the complex path to hydrogen propulsion and why air travel will get more expensive.

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Rush Transcript

Joe Anselmo:

Welcome to Aviation Week's Check Six podcast. I'm Joe Anselmo, Editorial Director and Editor-in-Chief of Aviation Week magazine.

Nobody has figured out yet how commercial aviation is going to make the leap to net-zero travel by 2050 as the industry has promised. Sustainable aviation fuels will need to play a big role in the near term, but that's just a down payment. Getting to net-zero will likely require a radical change in strategic thinking about the design of future airliners. Enter Universal Hydrogen and its visionary founder Paul Eremenko. Earlier this month the company conducted a flight test of a modified Dash 8 aircraft with a megawatt scale hydrogen fuel cell propulsion system replacing the turboprop's right-hand Pratt & Whitney engine.

The flight was momentous enough that we put it on the cover of Aviation Week and Space Technology magazine under the banner, “Hello Hydrogen.” Universal Hydrogen is aiming to modify Dash 8s and ATR 72s into hydrogen powered aircraft and says it has orders for 247 conversions from 16 operators. And Eremenko predicts that within five years it will be inconceivable for Airbus or Boeing to launch a kerosene burning airplane, even if that kerosene is SAF.

Hold on, say a sizeable number of skeptics. They note that huge technical and market hurdles will have to be overcome before hydrogen powered flight becomes routine.

Joining us for today's discussion is Martha Neubauer, a senior associate at Aerodynamic Advisory, an aviation and aerospace consulting firm based in Ann Arbor, Michigan. Also on the podcast are two Aviation Week editors who have written extensively about hydrogen propulsion, Graham Warwick and Thierry Dubois. Martha, you just finished writing a guest viewpoint for Aviation Week on the challenges of hydrogen propulsion. Tell our listeners what those are.

Martha Neubauer:

Hi, Joe. Thank you so much for having me on the podcast. How we view this at Aerodynamic Advisory is that there really are both technical and market hurdles to overcome before we see hydrogen powered aircraft in our fleet. We think these test flights by ZeroAvia and Universal Hydrogen are incredibly exciting, but we also understand that there are significant hurdles before we actually are going to be getting on board a hydrogen aircraft.

To touch on some of the technical challenges, first is really scaling up the systems. So the test flights that have been done by ZeroAvia and Universal Hydrogen provide about half or less of the power that's going to be necessary for regional aircraft in the future. So this is something that just getting these fuel cell systems to scale, not only getting larger fuel cell stacks, but especially integrating the large cooling system required into the aircraft, is going to take significant time.

Really the main reason for this is that cooling system, which is often called the balance of plant, which requires significant integration because it's such a large system because a fuel cell releases 50% as heat. So, if you're producing one megawatt of electrical power, you also have to dissipate one megawatt of heat. So this creates significant cooling drag, which also then increases the size of the total system and increases that power requirement that you need.

Next, there are a lot of challenges just because fuel cells haven't really been tested in aviation applications and that longevity hasn't been tested. So fuel cell durability is a challenge that really there's just a lot of unknowns that need to be solved, one of those being embrittlement of the system and how that can cause cracking, another, maintaining the proper humidification in the fuel cell and also just how it responds to shock and vibration and if that can cause cracking in the fuel cell in that brain. A lot of these are problems that seem solvable. It's really just that you need time to test and do that lifecycle proving out that fuel cells can meet the aviation level of safety.

Also, there are significant market challenges that need to be overcome and a lot of uncertainty in the cost picture and how hydrogen aircraft will be cost competitive to traditional kerosene aircraft. Right now with some modest increases in carbon prices, it's expected that hydrogen fuel cell aircraft will cost about double what it costs to fly a traditional kerosene aircraft today. Again, there are a lot of unknowns that there could be increases in carbon taxes, there could be hydrogen or SAF subsidies along the way, and I do think this is something that is coming in our future, but this is something that could be an ever-changing picture in terms of that cost competitiveness of hydrogen.

One of the other main challenges with hydrogen aircraft is the range fungibility. Airlines like to have aircraft with ranges that are much longer than what they typically fly that aircraft for just because it provides flexibility for the operator. Hydrogen aircraft of this size, even if flown on liquid hydrogen, are expected to have a range of about 500 nautical miles, which is significantly less than what we see today for regional aircraft. This again, is a challenge for airlines.

Lastly, integration into airline operations is a challenge, which could also be a challenge with 100% SAF. So it's something that we'll see how this plays out in terms of managing a dual fuel system. In this case, having hydrogen and jet fuel. And what do you do if you have an aircraft that is flying on hydrogen and you're flying it to an airport that doesn't have hydrogen? That's not going to be an option to then fly that aircraft back if you have to refuel. So I know this is the problem that Universal Hydrogen and ZeroAvia are trying to solve, but definitely it's a logistical challenge for airports and airlines.

Joe Anselmo:

Graham Warwick, that was quite a list we just heard. What's your reaction to what you just heard?

Graham Warwick:

Yes, and Martha hit all of the points. I mean this is a huge challenge. I'm fine with skepticism, but what I hate is skepticism based on ignorance and what Martha's done is she's laid out what the real reasons for skepticism are because of all these challenges. So often you just hear people who are skeptical simply. They just say “It can't be done because it hasn't been done, it can't be done because we tried it 50 years ago.” And that is just unacceptable. If you're going to base your skepticism, base it on understanding, making an effort to understand the technology and that's what I am doing. I'm a 67-year-old aviation journalist. I've been writing for aviation for 45 years. I am learning about electric propulsion, I'm learning about fuel cell and hydrogen propulsion. I'm taking the effort to understand or try to understand and communicate my understanding of how these things work and what the challenges are. And we are getting a start across all of these technologies, batteries, fuel cells. We're getting a start by taking automotive technology and adapting it to aerospace.

So these fuel cells that are flying are the size that would power a heavy duty truck or something like that, and they're on the roads today, Gaius hydrogen storage, you name it, low temperature membranes, but you have to adapt them to aircraft. Now we are adapting them to smaller airplanes, lower performance airplanes. These airplanes don't fly too fast, they don't fly too high, they don't fly IN that much rain. So the drag issue for these initial airplanes is minimized because these are slow low-flying airplanes, not jet airplanes, they're turboprops, whatever.

So you can see a path to taking that, adapting that technology and getting something flying. The big question I'm asking, and I know Thierry's been doing this asking, is how do we start making aerospace grade fuel cell propulsion systems? What do we need to do to make a truly aerospace grade -- that's safety, performance, weight, everything like that? If I have skepticism -- I am pretty sure Universal Hydrogen and ZeroAvia are going to get something certified, going to get something into the marketplace. They're going to get initial customers flying and you can look around the world and you can see where this is going to work. If you're in Norway or if you are in maybe New Zealand, maybe the west coast of the U.S., you could have a closed environment where you can make sure hydrogen is available for a relatively short haul network between airports that can be supplied with hydrogen.

My biggest issue is it's a great start, but it makes absolutely no dent on aviation sustainability, or no noticeable dent on aviation sustainability. How do you take that and scale it to where you really do start to decarbonize a larger part of the industry? The big issues that Martha raised is airlines do not like running dissimilar fleets. They want to have all the same airplanes lined up on the runway. They don't want to have a sub fleet that can only do short routes or a sub fleet that can only use one fuel. That's an operational issue that we've got to tackle. So my feeling is yes, be skeptical, but be informed to be skeptical and be skeptical about the right things. It's all right to say it'll never get certified. If these companies throw enough money at it, they will get it certified.

The question then becomes can they get this in the market in a way that then logically scales to a point where they really make a difference to aviation? And that's where I'm looking and saying I could see this working in pockets around the world. I can see this working on small numbers, certain types of airplanes. I'm trying to understand how you get this out of this little box into something that really makes a difference across a broad range of aviation.

Joe Anselmo:

Thierry Dubois, Airbus is going full speed ahead to develop a small hydrogen powered airliner by 2035, but even Airbus says it's not going to be scalable enough to move the needle on net-zero by 2050.

Thierry Dubois:

Correct. And they are betting on both hydrogen and SAF. But also Airbus, a well established aircraft manufacturer, is going full steam ahead. Who is making the headlines right now? Who has stolen the headlines? It's Paul Eremenko, a startup, and of course ZeroAvia as well. So that shows us how innovative aviation has to be to really tackle climate change and how successful those startups are being.

To answer Martha's list of absolutely legitimate and well-explained concerns, I would say the glass is half full and filling fast. That's how I would see it. You mentioned the power level that these aircraft have been showing, which is about half what the original aircraft will actually need in commercial operations. It's absolutely true. I would say that being already at half that power is already an achievement. So yes, they have yet to prove that they can go higher than that, but I think there are ... when I they that's essentially ZeroAvia and Universal Hydrogen, I think they're on the right track.

I would also say that the aviation industry can really have reasonable hopes to leverage technologies from other sectors, other transport sectors such as the maritime sector or the train industry. In the train industry, for example, a hydrogen train is only 30 to 40% more expensive in terms of that the purchase price, 30-40% more expensive than a regular train, which is far lower than the expectations for hydrogen aircraft. And we can expect maybe two generations of trains or two generations of ships before Airbus, for instance, before the first Airbus flies with hydrogen, which means that technologies developed in all the sectors may help aviation with bringing costs down.

So I think there is a lot of hope in front of aviation. And to answer your concern and Graham's concern or remark on fungibility and on the fact that airlines want quite uniform fleets, I think at some point aviation will have to sacrifice something. I think at some point aviation will have to accept that they cannot operate as they did over the last decades.

Martha Neubauer:

Yeah, thank you. I appreciate that both of you have highlighted that yes, there are a lot of technical challenges, but you can't just say, “Oh, it will never happen.” Because we're aviation. We solve some of the world's hardest problems and I'm sure if 50 plus years ago, if you said the temperatures that engines would be running at today, that people would say “You're crazy and it's never going to happen. You'll never find materials that can work in those engines.” They'd say you were crazy. So you never know what this industry can solve.

But on your point about the integration of operations and having more of a bifurcation in terms of shorter range aircraft and longer range aircraft, I completely agree that that's something that we'll be moving towards eventually. And I actually think regional jets versus turboprops are a good example of where this happens already today, where turboprops are cheaper to operate. They are slower, so they're not great for some longer routes, but they do have a more niche case where they do actually make a lot more sense to operate from a cost perspective and there are those more cluster operations like Horizon Air, used to be only turboprops previously.

So I think that that's a good ... it shows that it's something that's possible, and especially with seeing how carbon taxes and subsidies evolve, that will motivate that shift to a bifurcation and short range aircraft versus longer range aircraft in order to take advantage of the lower emissions of these aircraft that are applicable to shorter ranges.

Joe Anselmo:

To the point you just made, Martha, I thought it was really interesting that even if a lot of these technological hurdles are overcome, just the cost of retrofitting airports to accommodate hydrogen power aircraft is immense.

Graham Warwick:

Okay, can I just jump in here and say that that's one of the question marks, but we've got to realize here that when you're talking about hydrogen, you are talking about the potentially a societal level change in energy, and if we can ride on that societal level change in energy, then we don't have to do all the heavy lifting ourselves. You look at the cost of hydrogen and if you take the part of energy's goal, I think you said it's a dollar a kilogram or something, I forget what it is anyway, but if you look at that and you say that that is an energy industry-wide issue about getting to the levels of production of green hydrogen where you get the costs down to what these targets are.

So aviation can't get green hydrogen to that level of production, but there may be other areas. As Thierry says, maritime is another big one for this. I mean they're struggling with maritime to be able to decarbonize. Trains another one. And then just energy, just globally energy, what do you do with renewable energy? It's a somewhat uncontrollable asset. You get electricity when you get electricity, so you want to turn it into something. So they're looking at hydrogen as way of storing that. So there are all these things that are going on that could affect the price of hydrogen. So we have to realize that it's possible that aviation doesn't have to do all the heavy lifting here.

Secondly, Marta brought up the point that if we look at anything in aviation, somebody at some point said it wasn't possible. I've already seen just looking at ... but just tracking battery technology. We haven't seen huge jumps in battery performance in the past five years. We've seen huge jumps in electric aircraft performance in the last five years because we are learning how to use, to work within the limits of the batteries and make the most of them. So we don't have these huge heavy packs anymore. We have integrated structures that make the best use of the ... it's aerospace engineering. We are really good at this stuff. Right?

And then I think that, and this is Thierry's point, absolutely Thierry's point, airlines have no choice going forward. The monolithic air transport structure is going away. It's going to be replaced by a much more tailored, bespoke led, segmented industry because no one solution to decarbonization applies to everything. So we are going to have to use multiple solutions, which means we're going to have to have fleets with slightly different characteristics. And so that makes it, if you accept that, then you can carve out a niche for hydrogen aircraft.

The other point is if you use hydrogen in shorter range airplanes, if you keep SAF and everything for the really long range and you use hydrogen in smaller airplanes, then the reality is the onsite hydrogen production becomes a reality. Airports are already putting solar arrays all over the airports. They're going to become major energy hubs going forward. So you're going to be able to generate power on the airport. You might want to be able to use that to put it into hydrogen, I don't know. But all of these pieces are in motion and to just look at it and say it'll never happen is the wrong approach. What you need to do is look at it and say, okay, which of the pacing items here, what's going to happen first? What needs to happen next? And say, okay, some of these things may ... they would almost certainly won't happen on timescales people say they will. But they could happen on different timescales.

Thierry Dubois:

To Graham's point, I was earlier saying that airlines will have to sacrifice something and as Graham was saying, there will be multiple solutions and the concept of monolithic transport is going away, that's Graham's words. To tell differently, I think airlines and passengers have to accept that from an economical point of view, air transport will not be as optimal as today. The good news is there might still be some of that transport, it might still be acceptable by the society at large because of those solutions, but ... well, maybe it would be more costly, maybe shorter ranges will make traveling less practical, but it will still be possible and that's the good news.

Joe Anselmo:

Martha, I see you nodding in agreement.

Martha Neubauer:

Yeah, that's really something. I think what it boils down to when looking at all forms of alternative propulsion technology and sustainable aviation fuels is that it's inevitable that flying is going to get more expensive in the future. And whether that be power to liquid, sustainable aviation fuels, which are much more expensive than kerosene or whether that be hydrogen and maybe airlines having to deal with less optimal route structures, it will get more expensive. And so, what we want to see as an industry is those solutions, subsidies for development of the enabling technologies, anything that can help support sustainment of our air travel industry, so it doesn't just mean that people aren't able to fly and travel, whether that be for business or leisure in the future.

Joe Anselmo:

We are running short on time, but Graham Warwick, I wanted to end with you. You've interviewed Paul Eremenko many times, you know him well. What the heck is he talking about, that Boeing and Airbus won't launch kerosene fueled aircraft after 2028? Boeing might not even launch an aircraft by then, right? Anything.

Graham Warwick:

Paul is passionate about this and he's a very, very outspoken person. He founded Universal Hydrogen to tackle the single biggest problem with hydrogen, which is infrastructure. His focus is how to get hydrogen to the airport so it can be used in aircraft. His goal is to enable Airbus or Boeing to use hydrogen by putting that infrastructure in place. The powertrain bit of it is just to get the market going. He wants to do that and he's passionate about it being hydrogen. If you talk to him about hydrogen used in sustainable aviation fuel, which is an absolutely perfect good use of power to liquid, great, okay. He literally says, why spend the money doing that, changing that conversion from hydrogen to SAF? It just doesn't make sense. He's very, very passionate about it,.

But he is trying to tackle the single biggest challenge, which is the thing that people say, how do you get hydrogen to an airport? And that's his goal. I'm going to just end by emphasizing Martha's point. Aviation is going to get more expensive. We are used to taking an energy resource out of the ground. We did nothing. We didn't put the energy in there, that was put in there in geological ages. We’re just pulling it out, turning it into fuel and putting it in airplanes.

Every option we have in front of us, we have got to take energy and put it into a carrier and put that carrier, whether it's a battery, whether it's hydrogen, whether it's SAF, whether it’s ammonia, we've got to put that energy carrier into an airplane and turn it into thrust. That takes money, that takes energy to put energy in, to get energy out, and we are not used to doing that. We're used to having the energy for ... it's there, we just use it. Going forward, we are going to have to pay for that energy. Now that energy's going to get cheaper as the whole world tackles that problem, but we have got to realize that as an industry going forward, we've got to start to pay to put the energy in that we take out when we fly the airplane.

Joe Anselmo:

Okay. Well, that's a rather sobering note to end this podcast on, but fascinating conversation. Thank you, Graham, thank you, Thierry. Martha, special thanks to you for joining us as a guest on this edition. That is a wrap for this week's Check Six podcast. Special thanks to our podcast editor, Guy Ferneyhough. If you're interested in air travel, you don't want to miss the recent edition of our sister podcast, Window Seat. Listen in as Emirates President Tim Clark joins ATW Editor-in-Chief Karen Walker to talk about his 50-year career and where he sees the air transport industry heading. You can find Window Seat where you found this podcast. Thank you for your time and have a great week.