Hydrogen-powered planes almost ready for takeoff

You'd need huge cryogenic tanks due to the volume density of hydrogen over kerosene. Good for rockets that you can jettison tanks from, but less so for planes. I just don't see it ever being practical for aviation over just creating our own hydrocarbons out of something else. Either catalyst based or otherwise. That's potentially carbon neutral as well.
Edit: my comment, but with numbers https://pubs.aip.org/physicstoday/article/74/9/11/928294/Hydrogen-as-an-aviation-fuel It's not a problem with how heavy the fuel would be or just how much space they'd take. It's how heavy the damn tanks would need to be and how much of the aircraft would be devoted to them on long distance flights.
- Even if it takes more space, there are still benefits over biofuels.
  The hydrogen can be created using electricity. Currently it is not very efficient, but only uses electricity and water. Electricity can come from de carbonated (/low carbon) sources.
  And a fuel cell will use that hydrogen to generate electricity by combining the hydrogen into water with outside oxygen.
  For the biofuel, it's a big climate hoax. The issue with bio fuels, is that the energy required to produce them is huge. It required bacteria producing carbon emissions, and the fuel also produced carbon emissions. Whatever entered that plan, will get out, and even more because of the transformation. (i don't remember which video from Undecided with Matt Ferell was about biofuels). Tho maybe it could be used for something. To get slightly less carbon emissions than with normal fuel.
  There may also be a solution with batteries. However the energy density for them is lower compared to hydrogen. Tho, there may be some battery innovation I saw passing by which could be pretty interesting.
  
  CO2 to syngas to hydrocarbon fuels is probably a better carbon zero process, considering we will need to do a ton of cdr anyway....although doubt energetics and economics would be great. Hydrogen, just like biofuels today are anything but carbon neutral, and efficient electrolysis might never happen. Hydrogen production will also face water shortage issues and in general electrolysis requires pretty low tds water which is not trivial to source...not sure what's best way to get carbon zero airplanes honestly...
- There was an article around here about Germany ditching hydrogen for their trains, which, if justifiable, seems damning for anything in the air.
  
  As someone from Germany that's the first time in reading that it was ever a thing for trains
  Pretty much all our rails have electric lines on top and most trains are working electrically already
  I really don't see a point to waste hydrogen on cars or trains where pure electricity is working fine
  Planes seems to be the main target that absolutely will never work electrically so it needs hydrogen - there even was an article about a ship running on batteries a couple of days ago
  
  The thing with trains is twofold: First of all, it's relatively easy to ensure that a train is more or less always hooked up to the grid (lines over the tracks). That means it can charge almost constantly, and doesn't need a large battery.
  The second thing is that the energy required to run a train scales very slowly with mass, because there is almost no rolling resistance (steel wheels on steel tracks have that advantage). That means you can increase the base weight of the train a bit without worrying about increased energy consumption.
  Hydrogen can compete in applications where you need large amounts of energy, that needs to be transported, and where you don't have regular access to the grid. Prime examples could be long-distance shipping, flight, and long-distance trucking through areas with little or no electric infrastructure (e.g. rural Australia).
- It's no more of a problem than dealing with LPG, surely? Pressurise it for storage.
  
  The difference is the 'L' in LPG. It turns liquid at a relatively low pressure and takes up much less space then. Hydrogen does not do that, so it has to be stored at a much, much higher pressure. For example, a medical oxygen bottle or a scuba tank has around 200 atm of pressure. For cars, hydrogen is usually stored at 700 atm. And the pressure inside an LPG tank is around 8 atm at room temperature.
  
  I think it is, not sure but it requres bigger pressure and hidrogen is smallest atom that escapes even from high presure tanks.
  
  You can't keep liquid hydrogen by pressure alone and even as a liquid it's volume density it's very low compared to other liquids.
  
  A couple issues have been mentioned, but what hasn't been mentioned is that hydrogen is difficult to store, because the molecules are small enough do migrate through most containers and escape. If your container is made of metal, you also get something called hydrogen embrittlement which breaks your container over time.

Germany just announced they will discontinue their hydrogen-powered train service in favor of a battery-based solution due to the higher running cost.
Hydrogen may be an alternative, but it has yet to make continuous, solid financial sense for any type of transport.
- If weight isn't an issue, then it makes sense to use a system that only costs a fraction of a hydrogen-powered setup.
  Trains don't need to fly. Just pack them full of batteries or - arguably even better - just electrify the line wherever possible.
  That's just not an option for planes, so hydrogen remains a potentially viable approach.
  
  Same goes for large container ships. It won't make sense to use batteries unless there are significant breakthroughs in capacity technology.
- I'm just happy that there are efforts being made into alternatives to oil... at any level.
  
  Sadly industrial hydrogen production is done by reforming petroleum with steam which releases huge amounts of CO2.

Hydrogen sounds like a great idea for decarbonization until you get around to asking, "wait, where do we get the hydrogen from?" and realize that it's incredibly energy intensive and the most popular process releases a lot of CO2 directly.
https://en.wikipedia.org/wiki/Hydrogenproduction
- Hydrogen is an energy storage, like a battery, so of course it requires a lot of energy to produce, that's the energy that you get back when consuming it (minus inefficiency losses of course).
  The advantage of hydrogen over fossil fuels is that it can be produced from renewable energy, while fossil fuels cannot.
- There's a comment on another post with this article doing the math on this, and it seems like the net emissions (when you account for efficiencies) actually favour steam-reforming + fuel cells.
- Last time I checked, CO2 released at that altitude has 3x the effect on radiative forcing, so it's good that we're not dumping it up there. I know water is also a greenhouse gas, but I expect the residence time to be substantially lower than for CO2. So it would be a net positive as long as we're emitting on the ground the same amount of CO2 as emitted up there (we're probably emitting more, but probably not 3x more and it would be easier to capture at the exhaust than from up there)
  PS: more on radiative forcing factors here https://sustainable.stanford.edu/sites/g/files/sbiybj26701/files/media/file/s3-radiative-forcing-rfi-memo_public.pdf

No.... No, it isn't... But you can imagine what it would be like if it was, right?

This is the best summary I could come up with:
A complete hydrogen fuel cell powertrain assembly occupied the pride of place in the pavilion of Beyond Aero at the recently concluded Paris Air Show.
That a fuel cell system was the Toulouse-based startup’s centerpiece at the biennial aero event is an indication of the steps being taken by a range of companies, from startups to multinational corporations, toward realizing the goal of using hydrogen as fuel in the aviation sector.
Even though in its current form, it serves only ultralight aviation, the successful test of the powertrain is a crucial step in our technical development path for designing and building a business aircraft,” Beyond Aero co-founder Hugo Tarlé told Ars Technica.
“The CS23 is a EASA (European Union Aviation Safety Agency) certification for small aircraft with a low Maximum Take-off Weight.
Speaking about the design challenges, Tarlé said mastering the characteristics of hydrogen and oxygen inside the fuel cell was a critical task.
Mastering the complexity of the cooling system is therefore critical,” he said, adding Beyond Aero has patented a solution in this regard.
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Imagine the explosion upon impact. 🤣

Leaking hydrogen into the upper atmosphere sounds like a bad idea. It extends the life of methane, making the green house problem worse. I really hope that they reduce the leaking issue to a minimum.
- But the short term profits!!!
- Isn’t it flammable? I’d think leaks would have to be zero for even more basic reasons.
  
  Yes, it's very flammable. But it's also very light. Lighter than Oxygen. And the molecules are small which means most air tight applications don't work well. Even the tanks they make now still has this issue where hydrogen molecules can escape through the barriers over time.

Hydrogen-powered planes almost ready for takeoff
No they aren't, and they never will be (save for maybe a few small private one-offs). Certainly never for anything commercial.
- While I certainly agree with the first part of your comment, what makes you sure they'll never be commercially viable? The energy density and application of liquid hydrogen is getting pretty good these days.
- Never Say Never.
  
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The output is water, right? Wouldn't this put more water vapor in the atmosphere? Because water vapor also increases the greenhouse effect.
- However since water vapors also create clouds which reflect light it is definitely bettern than co2
- Water doesn't linger in the atmosphere like CO2, and so much water evaporates from the oceans that anything we could do to put more water in the air is negligible. The only real way we can influence the humidity of the atmosphere is by changing the temperature with carbon.
- It's ok, well drink it
- a bigger problem is that hydrogen that leaks out reacts with free hydroxides that would otherwise break down methane into co2

That sounds like an incredibly bad idea.
- Why?
  
  I'm guessing that they are (falsely) equating it to the hindenburg, when IMO it wouldn't be much different safety-wise than current fossil fuel powered planes.
  It's not like they would be filling the wings and luggage compartment with free-floating hydrogen, it stays in it's tank
  
  Because hydrogen is highly explosive.
  
  Hindenburg
  
  Something something woke liberal climate hoax.
- Bad idea? You don't even know how it works. So please don't comment your s* opinion.
  
  What makes you think I don't know how it works?
  It's a bad idea because hydrogen is highly flammable and explosive compared to jet fuel.