Passenger Aircraft: What Will Green/Comfier Versions Look Like in 2040?
Passenger aircraft will be changing rapidly on at least three fronts: 1) Under pressure to lower carbon emissions, short-haul aircraft will become more battery-powered and electric, while long-haul aircraft may become more hydrogen-powered 2) As a reaction to passengers going stir-crazy on crowded flights, longer-haul aircraft may place passengers at two levels, allowing them some ability to be horizontal and 3) Material science improvements (such as carbon-fiber) and improved wing-designs will decrease air-friction, allow for faster speeds and greater fuel economies. All-together, improved aircraft may overtake the concept of regional high-speed rail.
The Background: For many years, aircraft was spared the energy and pollution scrutiny of automobiles. It was as though folks were so excited to be in a plane (and be entertained by it-turns-out-not-so-practical Buck Rogers aircraft futures involving supersonic speeds and airline cruise-ships), they tolerated ANY kind of aircraft or flight. But now, people are realizing that aircraft also pollutes, and that while priced reasonably, people are packed like rats (and sometimes subsequently act like rats). Meanwhile, there are some fairly simple improvements “waiting in the wings”, which could make aircraft more efficient, safer, and comfortable. All this may also be rather bad news for rail fans, since improved aircraft may soon make long-distance train-travel look silly by comparison (rail purists hate all this, but it seems inevitable).
The Evolution of Battery-Powered, Electric, and Hydrogen Powered Aircraft: Similar to the evolution of battery and fuel cell powered autos and trucks, aircraft is evolving in much the same fashion. Smaller aircraft (and passenger aircraft with short-hauls) are developing along the battery-powered electric route, while larger, long-haul aircraft designers are looking seriously at hydrogen powered aircraft.
1) Small and short-haul battery-powered aircraft: Much of this is predicated upon battery evolution, as batteries need to get more energy-dense (and lighter) to be viable in aircraft (where weight is critical). Currently, small planes can be powered by lithium-ion batteries that power electric motors, but to be useful in larger short-haul aircraft, batteries will need to get better (lighter, cheaper, safer, more range). Never fear though, solid state lithium batteries are on their way. They are more expensive, but still within the budgets of passenger airline haulers. There are even “hybrid” aircraft on the way, using fuel for takeoff, and batteries for cruising speeds (thereby saving energy and polluting less).
2) Large Hydrogen powered aircraft-Airbus has already rolled out several hydrogen aircraft prototypes, called ZeroE Concepts, which are predicted to be in place by 2035 (note: 1,000 nm=1,000 nautical miles=1,150 miles, 2,000 nm is close to a NY to LA flight, and not quite a NY to London flight):
a) ZeroE Turbofan (Range 2,000 nm+, 200+ passengers): Two hybrid-hydrogen turbofan engines provide thrust. The liquid hydrogen storage and distribution system is located behind the rear pressure bulkhead.
b) ZeroE Turboprop (Range 1,000 nm+, 100+ passengers): Two hybrid-hydrogen turboprop engines, which drive eight-bladed propellers, provide thrust. The liquid hydrogen storage and distribution system is located behind the rear pressure bulkhead.
c) Blended Wing (Range 2,000 nm+, 200+ passengers): The Blended-Wing Body’s exceptionally wide interior opens up multiple options for hydrogen storage and distribution. Here, the liquid hydrogen storage tanks are located underneath the wings. Two hybrid-hydrogen turbofan engines provide thrust.
d) Fully Electrical Concept (Range 1,000 nm+, 100+ passengers): The fully electrical concept was revealed in December 2020. It is based on a fully electrical propulsion system powered by hydrogen fuel cells (airbus.com,2023)
e) More About Hydrogen: The Hindenburg Disaster aside, hydrogen is generally good stuff. It can be used to power fuel cells (which produce electricity), or burned directly (zero-pollution or carbon in either case). It can also be used as an energy storage device, being made by excess renewable energy through electrolysis (this helps at times when our electric grid can’t handle all the renewable energy produced). For some reason (ignorance? jealousy?), many oppose hydrogen (in favor of batteries), but hydrogen is much more energy dense and light, which really helps in aircraft. The major drawback currently is cost, but that is expected to drop as technology and economy-of-scales improve. Incidentally, the safety/flammability issues brought forth by the Hindenburg disaster have also substantially been addressed. (fchea.org,nd),(Memon,2022)
Improvements in Passenger Comfort: There has been a big change the last 20 years in airline efficiency. Gone are the days when there were more airlines and flights, often with many empty seats that allowed one to stretch out and not catch the cold of the adjacent passenger (or get bit by their emotional support animal). Airlines were deregulated and became more competitive, which resulted in fewer carriers (and flights), with just about every flight being full (or even overbooked). The cost of flying has subsequently become cheaper (it costs about the same to fly coast to coast now as it did in the 80s), yet passenger comfort has declined. The airlines use this as a way to sell more business class tickets, but soon they’ll need to increase passenger comfort simply to maintain customer satisfaction while keeping their staff and other passengers safe from nuts:
1) Larger Aircraft: While aircraft is not getting much faster anytime soon (they are capable of supersonic speeds, but that uses too much fuel and is out of step with current environmental goals), they may well get larger. Using hydrogen itself may precipitate larger aircraft, as it takes up more space for an equivalent jetfuel energy density.
2) Double decking passengers: There are several competing concepts for a redesign of passenger areas (especially in economy). Many involve the “double decking” of seats, which more or less allows passengers some legroom and a change to stretch out horizontally and sleep. This may require a decrease in cargo payload (currently the lower half of a typical plane), which is a big profit-center for airlines (yes, cargo holds carry much more than your luggage, likely many FedEx packages and the like, since airlines are also long-distance freight-haulers). A 1–2 hour haul may not discomfort the typical economy passenger in current seating configurations, but as economy seating has become more dense, long haul (ie coast to coast or overseas) economy flights have become almost unbearable. Some double-decking almost approaches the old Pullman Railroad car experience, with seats converting from vertical to horizontal, curtains and so forth. First Class compartments already have such nice capabilities, but bear in mind they’re paying about 5 times as much. At one time (the 50s), some airlines had bunk beds just like trains. So the next time you push the recline button and you only go back an inch or so (while the kid in back of you is kicking your seat), try to imagine what may soon be possible. (Shahani,2020),( (Street,2023),(Hadden,2023)
3) Cargo-Hauling vs Passenger Comfort vs Fuel Economy/Carbon Airlines operate on small profit margins (about $6 per person), and added weight increases fuel costs (which is why they sometimes charge more for bags). Fuel costs them about $0.10 per pound on a transcontinental trip. Their cargo customers pay by weight (more than $1 per lb, while not complaining about the food or clogging the toilets). All told, you might say that some airlines are tempted to haul more cargo and less economy passengers to make money, unless aircraft were to get bigger/more efficient to accommodate everyone. Since airlines are now under zero-carbon pressure, it appears that a kind of hydrogen-powered Blended Wing aircraft may be in their futures, not taking up any more airport footprint than a 747, but adding fuselage space along with more lift and fuel economy. This way, just about all interests of airline/passenger may be resolved, and you won’t have to cry “Mooo!” as you enter/exit, nor carry around that silly neck-pillow. Skift,2014),(Jensen,Yutko,2014)
Improvements in Aircraft Materials and Design: These are also materials and designs that have been around awhile, but coming closer to maturity due to tech progress:
1) Composites and Carbon Fibers: At one time, planes were mostly made of aluminum. This changed in the 80s, when the Airbus 300 started using composites (similar to fiberglass). These materials were at the time tested on various secondary parts, such as stabilizers. This evolution is also taking place with automobiles (in which you’re increasingly likely to see plastic/fiberglass parts) Cars also have weight/fuel economy issues (made more critical by zero carbon goals), but are more likely to contain steel, less likely aluminum. Lighter metals such as magnesium and titanium are also used in aircraft, although they are still quite expensive. With improvements to composites/carbon fibers, they are currently used on over 50% of the Boeing 787 and Airbus A350. Carbon Fiber Reinforced Plastic (CFRP) is currently used on modern aircraft wings. Though expensive, composites and carbon fibers have extraordinary strength to weight ratios, and are reducing the weight of modern aircraft up to 25%, which also results in fuel efficiencies. Besides costs, other composite/carbon fiber drawbacks are that proximity to fires can weaken resins, and any damage must be repaired immediately. (Memon,2023),(indmetal.com,2017)
2) Blended Wing Body: The Blended Wing Body (BWB) design has been around for awhile, and generates efficiencies by integrating the wings with the fuselage, generating more lift. When combined with hydrogen or Sustainable Aviation Fuel (SAF, a kind of biomass generated jet fuel), passenger aircraft’s carbon footprint could decrease by up to 80%. The main drawback to using BWB for large passenger aircraft is the loss of windows, but that could perhaps be offset by skylights and light tubes. (Michaels,2023),(energy.gov,nd)
What Effects will All of This Have on Climate Change, and How Soon? This is hard to say, but I suppose some of this might be called “Airline Greenwashing”, since its easy for them to say “Hydrogen planes are coming by 2035” or some such, and not fulfill the objective. The aircraft industry doesn’t want to throw away its expensive Boeing 737s or Airbus A320s overnight either, so I suspect they need to start looking at hydrogen-fuel conversions (currently, aviation fuel (basically, kerosene) is stored in wing bladders, hydrogen fuel storage would involve utilizing more fuselage space, which in turn might pinch passenger comfort, so some things to work out).
Conclusions: I suppose that passenger airlines may be the last frontier of zero carbon tech, since it takes so much fuel to get those things up in the air. There also doesn’t seem to be as much consumer choice or government pressure in the matter (after all, we have much more consumer choice with more highly-regulated automobiles). One could see things like cruise-ships converting to hydrogen power/providing unlimited passenger comfort, as they are HUGE and might convert easily. Aircraft almost requires an entire redesign and paradigm shift to accommodate creature comforts and zero carbon. Short of going back to the 2-day transatlantic zeppelin trips of the 30s (now there’s comfort and fuel economy), we may need to get airlines to about 80% efficiencies and “carbon-tax” the rest, at least for the near-term. Finally, sorry high-speed rail fans, for moving people/freight quickly and flexibly, you probably won’t be able to compete with this new generation or air-travel. Even in rail-topia Europe, air-travel is started to replace rail. (Finlay,2020),(O’Toole,2021)
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