[HN Gopher] FlyZero Unveils Final Hydrogen-Powered Airliner Conc...
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FlyZero Unveils Final Hydrogen-Powered Airliner Concepts
Author : hindsightbias
Score : 36 points
Date : 2022-03-16 16:49 UTC (6 hours ago)
(HTM) web link (aviationweek.com)
(TXT) w3m dump (aviationweek.com)
| linsomniac wrote:
| Legitimately wondering if the public will be able to overcome the
| marketing of the last hydrogen "airliner"...
| RobLach wrote:
| The Hindenberg disaster was quite the spectacle but
| surprisingly only ~30% of those onboard died.
| vondur wrote:
| Well, the Hindenburg didn't hit the ground very fast...
| cm2187 wrote:
| But this is with Hydrogen under pressure. I am a bit nervous
| about the failure mode.
| usrusr wrote:
| Cryogenic, 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.
| AYBABTME wrote:
| Reading 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.
| thot_experiment wrote:
| I 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)
| dehrmann wrote:
| I wonder if we'll just end up running jet engines on biodiesel
| for long-haul flights where batteries aren't viable.
| nradov wrote:
| Yes 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.
| karmakurtisaani wrote:
| I don't think they burn the hydrogen at all. Rather, it's
| turned into water and free electrons by some chemical process
| whose details I totally forgot.
|
| One idea I've seen floating around would be having small scale
| nuclear plants near airports producing hydrogen from water and
| electricity (the reverse process of what happens in the plane
| turbines).
| ElectronCharge wrote:
| You're talking about fuel cells, which are only used with the
| smallest (prop) design. The two larger jets are intended to
| have hydrogen turbines, burning hydrogen and producing water.
|
| I love the idea of small modular reactors (SMRs) being used
| to produce the hydrogen from water. We also need a vast
| buildout of safe, clean, dependable modern nuclear reactors
| to provide the developing world with enough energy to make
| the demographic transition (via a higher standard of living)
| to better environmental practices.
| upofadown wrote:
| >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 wrote:
| There are also issues like hydrogen embrittlement, tiny
| cracks, etc.
|
| These are all solvable, but it's just expensive and hard.
| throwawayboise wrote:
| Synthetic 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.
| samwillis wrote:
| With 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.
| dr_dshiv wrote:
| And offsets. Everything needs offsets. Even green supply
| chains.
| AYBABTME wrote:
| What's the main safety concern for hydrogen?
| adonovan wrote:
| > 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 wrote:
| Takeoff 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 wrote:
| I 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 wrote:
| Unless 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 wrote:
| > 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 wrote:
| The 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.
| exabrial wrote:
| Dumb 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 wrote:
| The 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.
| Hnrobert42 wrote:
| The 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 wrote:
| Thinner 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.
| kurthr wrote:
| I 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-na...
| akamaka wrote:
| There 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.
| iancmceachern wrote:
| Exactly. This is how we progress, by identifying things that
| are really worth doing, despite being hard and risky, because
| the payoff is worth the investment.
| HPsquared wrote:
| Sometimes 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.
| gigatexal wrote:
| How do they solve the hydrogen leaking out of its container?
| HPsquared wrote:
| Airliners 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.
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