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FlyZero Unveils Final Hydrogen-Powered Airliner Concepts
- throwawayboise 5y agoSynthetic kerosene as jet fuel seems to me to be a far more pragmatic approach, it does not require the development and airworthiness certifications of entirely new fuel handling and storage systems, and it does not make obsolete the entire stock of existing aircraft.
- ncmncm 5y agoSynthetic kerosene certainly will be used, but aircraft using it will not be able to compete with hydrogen-fueled craft on the same routes.
- exabrial 5y agoDumb question, feel free to ridicule me: Most aircraft keep fuel in their wings, but said wings are thin because fuel is not under (high) pressure. Why can't we have thicker wings, or thinner tanks, that can accommodate hydrogen vessels?
- Ourgon 5y agoThe answer is air resistance which increases with the third power of the object speed. Airships are fairly slow which allows this type of design. Passenger or freight jets are supposed to be fast, this being their major appeal over ship and rail transport.
- kurthr 5y agoI think for safety and convenience, they're likely to use the upper portion of the fuselage for storage. That way, if there is a leak... it goes up and out. https://cleantechnica.com/2022/01/12/money-talks-zeroavia-nails-paine-field-site-for-hydrogen-aircraft-rd/ https://cleantechnica.com/2022/01/12/money-talks-zeroavia-na...
- ncmncm 5y agoIt will be assumed there are leaks at all times, and positive airflow will be maintained to eliminate possibility of ignition. But the fuel probably should be stored liquified in outboard nacelles, anyway.
- Hnrobert42 5y agoThe article describes “dry” wings which allows for more flexibility and some other benefits. The fuel is stored, depending on the model, under the fuselage or at the rear of the aircraft.
- carabiner 5y agoThinner tanks would have to be strengthened and heavier because they're under pressure and the non-spherical shape leads to higher stresses. It'd be like building a main cabin shaped like a square; the volume to weight ratio would suffer. Thicker wings... this would have major reductions in performance. For cruising speeds of today, thinner airfoils are favored for low drag at supercritical speeds. Airfoil design is delicate and minute changes in the shape can dramatically affect the performance (operating cost) of the entire aircraft. Biggest tradeoff in commercial aircraft design is operating cost vs. everything. Anything can fly with a big enough engine on it, even a lead block. That's not the challenge. Minimizing cost per passenger-mile though is everything.
- thot_experiment 5y agoI am very skeptical they will be able to get the efficiency numbers to a place where it makes sense in the timeframes they're throwing around unless oil goes up like 4x in price. Storing hydrogen is really hard and the related tradeoffs are much tougher than with a room temp liquid hydrocarbon. I imagine burning it in turbines also comes with some new issues but I know less about that. I think it's a decent path forward if we can figure it out, and I imagine the engine related problems are likely much more surmountable than the storage issues. There's also the related fuel infra that will need to happen before this is viable. It's far away unless something truly drastic changes the calculus on fossil fuels. (which would be great)
- upofadown 5y ago>Storing hydrogen is really hard Wouldn't this just be a low pressure insulated tank? The temperature would self regulate as the liquid H2 boiled off.
- deepnotderp 5y agoThere are also issues like hydrogen embrittlement, tiny cracks, etc. These are all solvable, but it's just expensive and hard.
- ncmncm 5y agoHydrogen embrittlement is a problem in high-pressure high-temperature tanks. When the pressure is low, nothing is being driven into the metal.
- dehrmann 5y agoI wonder if we'll just end up running jet engines on biodiesel for long-haul flights where batteries aren't viable.
- nradov 5y agoYes this has already been tested in existing commercial turbine engines and works fine. It's safe and won't require any changes to aircraft or aviation infrastructure. The sticking point is the cost of manufacturing the fuel. It will only be economically viable with some major government intervention.
- linsomniac 5y agoLegitimately wondering if the public will be able to overcome the marketing of the last hydrogen "airliner"...
- RobLach 5y agoThe Hindenberg disaster was quite the spectacle but surprisingly only ~30% of those onboard died.
- cm2187 5y agoBut this is with Hydrogen under pressure. I am a bit nervous about the failure mode.
- usrusr 5y agoCryogenic, or some hybrid. If insulation involves some actual gap I'd imagine that reliable methods to detect any cookoff failures would be simple and having access to a near sonic airsteam should give plenty of emergency venting opportunity. You'd still have a serious problem, but more of the ETOPS kind than of the fireball kind.
- ncmncm 5y agoNot under pressure. Liquified, at atmospheric pressure, and vented to make ignition of leaks impossible. There is a minimum partial pressure of hydrogen that must be exceeded before it can ignite. Keep leaked hydrogen below that, and it is harmless.
- vondur 5y agoWell, the Hindenburg didn't hit the ground very fast...
- AYBABTME 5y agoReading NTSB reports on (fatal) GA airplane accidents, most of them involve the plane burning down on impact. I'd say the current state of affairs isn't very glorious in term of fire risk, for planes using AVGAS.
- samwillis 5y agoWith all these “green” airplane startups I’m so completely unconvinced by the “electric” battery powered and hydrogen powered ones. The energy density for the battery’s and safety for hydrogen just isn’t feasible. I believe the only carbon neutral route forward for air travel is a carbon natural synthetic hydrocarbon fuel that is as close to current fuels as possible. It gets us the energy density needed and builds upon the 100 years of development the engines have had. Siemens Energy and Shell are both putting significant energy (pun intended) into R&D around these.
- AYBABTME 5y agoWhat's the main safety concern for hydrogen?
- paranoidrobot 5y agoAs others have mentioned here, it is difficult to keep contained, and because it's not very dense at room temperature/low pressures. So the example FTA given is cryogenic cooling. Because of the extreme cold, this can lead to new failure modes for materials. The other issue is that hydrogen when it burns has a very pale blue flame that can be difficult to impossible to see during daylight. It also apparently has a low radiant heat, which makes it difficult to feel from a distance. This makes firefighting and safety a major concern. The first you might know of a hydrogen fire, is that you're suddenly on fire yourself.
- ncmncm 5y agoIn confined spaces, mixed with air within a range of concentrations, it is explosive. So, hydrogen systems will need continuous positive airflow around them so that the partial pressure of any leaked hydrogen is kept at all times well below the point of ignitability. You start with the assumption that hydrogen will be leaking everywhere (because it does) and design so that it doesn't matter.
- dr_dshiv 5y agoAnd offsets. Everything needs offsets. Even green supply chains.
- akamaka 5y agoThere are a lot of people commenting on how difficult this will be to achieve, but it’s worth keeping in mind that even the “conventional” roadmap for improving aircraft efficiency is full of enormous challenges. Some of the proposed technologies include variable-pitch turbofans, laminar flow wings, blended wing body aircraft designs, all of which are risky R&D projects which might cost tens of billions of dollars to bring into production. Just an incremental improvement like the last GE9X engine cost several billion to develop, for a 10% fuel efficiency improvement. While these hydrogen concepts are incredible risky, it’s worth putting into context how difficult it will be to get to the next level of efficiency in aviation even without them.
- HPsquared 5y agoSometimes it can be better return on investment to try a new approach than to thoroughly optimize every detail of the existing approach. Edit: but, of course, complete failure is now possible when trying a new concept: it may not work at all. On the other hand, when making 1000 small optimisations the 100 unsuccessful ones can be left out.
- tatersolid 5y agoComplete failure is not an option in the aerospace industry. There are in fact lives at stake.
- jnsie 5y agoYour definition of complete failure is something making it to production and catastrophically failing. I would have imagined complete failure in this case as being significant R&D expense with no returns.
- fransje26 5y agoNah. A new approach is not what the investors want to hear. They want their dividends tomorrow. Better to squeeze an old design until the last drop of profit was extracted from it. No matter if crashes a few times in the process. You can always boast about the Jedi tricks you played on the (corrupt) "certification" authorities, and blame the crash on poor 3rd world piloting skills.
- adonovan 5y ago> Although the fuel cells only emit water as a byproduct mixture of liquid and vapor, the ATI adds that a water storage system was added. This was done to avoid the potential for creating precipitation during initial climb or leaving liquid water on the runway. What's the problem with liquid water on the runway? Can't most planes fly in heavy rain?
- chris_va 5y agoTakeoff and landing distances are based on surface conditions, and those conditions have to be known for pilots to make accurate decisions for the type of aircraft they are flying. Presumably unexpected water on the runway (which might later freeze, too) would cause the state to deviate from what was expected. For a particular plane, there are some runways that are long enough for takeoff when dry, but not (say) safe for takeoff with water/ice because you cannot abort safely. This is less of a thing for planes flying back and forth between large commercial hubs (since those same aircraft fly every day, in whatever conditions, they are generally sized accordingly). For a military heavy-lift transport, though, this becomes more of a thing.
- tomrod 5y agoI would love to see these come to fruition. Aren't these flying bombs, though? How to prevent combustion like a Hindenburg, but now from a hijacker?
- ceejayoz 5y agoUnless you mix oxygen in, hydrogen will just burn, not explode. 2/3 of the Hindenburg crew and passengers made it out alive, despite the visual impressiveness of the fire. Unlike jet fuel, it won't burn very long. Crashing one into the WTC on 9/11 would likely have done substantially less damage.
- warmwaffles 5y ago> Crashing one into the WTC on 9/11 would likely have done substantially less damage. That's actually an interesting thought. Had the burn not been as constant, would the towers have survived? And then even if they survived, how in the world would it have been repaired?
- thot_experiment 5y agoThe WTCs collapsed because of a myriad of reasons, I doubt very much that if an equivalent hydrogen powered jet had crashed into them the outcome would have been different. iirc the general consensus is that many (most?) skyscrapers would continue to stand after being hit by a plane in the same manner as the WTC towers, and specifically the all-steel no concrete construction combined with some other problematic factors in the design was the reason for the total collapse.
- hindsightbias 5y agoNorth Tower, probably. Hit upper levels. South Tower, mid-level, not a chance. It’s crazy it survived the impact. If the wing spar had gotten the corner it would have gone immediately (the video shows it tearing through the structural facade on the east side, but missing both corners). The exterior provided 50% of the structural support.
- gigatexal 5y agoHow do they solve the hydrogen leaking out of its container?
- HPsquared 5y agoAirliners only fly for a few hours at a time, this isn't as much of an issue over those timescales - just put some insulation on the tanks.