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kgb_izzy t1_iy8g8iv wrote

Awesome. hope it works out.


kukukele t1_iy8i4v2 wrote

Since the article didn't mention it, could some people share what the differences may be from a passenger perspective? It obviously has environmental benefits, but I assume it would be more cost-effective? Would it be quieter?


squeevey t1_iy8l766 wrote

It's still in discovery. But i believe reading between the lines this is still combustion of fuel (hydrogen) vs hydrogen fuel cell (which makes electricity to run the motor).


SomeDEGuy t1_iy8l90q wrote

Noise shouldn't be a huge difference, as its still burning material to force an object through air at speed.

Hydrogen is more energy dense per pound, but has some storage issues that would have to be figured out for safety. Storing a compressed gas like hydrogen is significantly more dangerous than the same mass of jet fuel. It's a good test, though, and helpful to explore new methods.


SzmFTW t1_iy8mf21 wrote

So… “Oh the humanity” is the first thing that pops in my head here.

Have they found a way to purely mitigate “engine go boom”?


MostlyPseudonymous t1_iy8mf9m wrote

Actually it's incredibly energy intensive, so 'easy' is misleading. That's only one of the very major problems with hydrogen as a fuel. Electrolysis of water consumes more energy than combustion of hydrogen releases.


Renoskytower t1_iy8mp40 wrote

The environmental benefits are not obvious, around 3/4 of the energy is lost in conversions... Having to build 2-3 times the infrastructure to do the same amount of work is not trivial


haircut50cents t1_iy8pwaq wrote

This will be an unpopular opinion but that's okay.

I wish they would stop spending time on hydrogen. The energy density is so low unless you turn it into "slush" which takes an incredible amount of energy to do and becomes a really dangerous fuel. I worked on these projects at a fairly large industrial company.

It just doesn't work but governments pay for it to appease environmentalists and businesses happily take the money. They all know it's not the future.


Art-Zuron t1_iy8s0k4 wrote

That's why it wouldn't be useful for power generation for a country, but as a fuel for discrete things like jets. Renewables like wind and water, and nonrenewables like fission should make up the difference. And, if we can ever figure out fusion, we could get nuclear power out of water too.

It took more energy to make Petrol than you get out of it too. And it takes millions of years to make it at that.


NoStatic78 t1_iy8t3jq wrote

That wasn't the engine that went boom, but the hydrogen in the gas bags used to provide lift. In any event, yes I understand we've created sufficiently study tanks to contain hydrogen, even in most accidents. There are films going back to the 1960s showing serious crash tests of cars with hydrogen tanks mounted, which got through the tests without leaks. Whether those tanks would survive an airplane crash, rather than a car crash, is a great question and I don't know the answer. But I would hope there's been some additional progress in the intervening sixty-ish years.


HillSooner t1_iy8vz7g wrote

That is highly misleading. Hydrogen in a form that can burn is not abundant. You have to put more energy in to separate hydrogen from things like water than you would get from burning the hydrogen.


Fearlessleader85 t1_iy8wznr wrote

Not to mention nearly all metals and some other materials suffer "hydrogen embrittlement" which causes them to fail catastrophically after extended exposure.

Hopefully it works out, but there are still significant engineering challenges to overcome before this is commonplace.


Bagellord t1_iy8x75u wrote

What would make me nervous is keeping it stable and leak free in an airplane, over their service lives. Not to mention the infrastructure on the ground.

To be clear, I think it's a great thing, if the benefits are there. But there's a ton of work to be done beyond a functioning engine.


MrJoyless t1_iy8xhwa wrote

>Hydrogen is more energy dense per pound,

True, but not by volume. That's why you see hydrogen tanks for rocket launches taking up a huge % of the total launch vehicle volume vs the oxidizer. Also the extra insulation required really offsets hydrogen's main weight saving benefit.

I'm not sure if there really is a good or safe way to transport or store hydrogen for air travel. Thermal issues would abound, especially with the temperature differentials airplanes experience at cruising altitude. That's not even mentioning the storage issues that occur since hydrogen is so damn small it can leak through seemingly solid containment vessels.


series_hybrid t1_iy8znee wrote

It was never a question as to whether or not it would work. The theory is soud,'s already been dine before by Lockheedin the late 1960's.

The problem has always been how to transport the fuel, and what form of H2 fuel was viable.

Which usually translates into short range.


Fearlessleader85 t1_iy91spo wrote

For airplanes, the energy intensive nature of it doesn't matter quite so much. We can produce it on the ground using alternatives, but up in the air is where energy density matters, both per unit volume and mass. Hydrogen has mass energy density in spades, which does matter.

There's definitely some barriers, but if we can get it to work, it opens some massive doors for fighting climate change.

It's possible, even likely, that an algae based biofuel could be a lower hanging fruit, but before that gets to be carbon neutral, it has to scale to support the full supply chain. Hydrogen doesn't have that limit. We could produce it cleanly, even with non-firm power options like solar and wind. Then from day one, it's carbon neutral.


greynolds17 t1_iy92zki wrote

I thought we decided that using hydrogen gas as a fuel was a bad idea on account of how extra explosive it is


Dangerous_Dac t1_iy95kem wrote

And even with all that volume and insulation, they're still constantly topping off the tanks until t-0, and all that gas you see billowing out from rockets on the pad is boiloff from large amounts seeping out from various junctions and connections because keeping that shit in one place is hard.


WeTheSummerKid t1_iy95r40 wrote

I want a hydrogen-powered turbo-rocket-ramjet; a Variable Cycle Engine that can switch from turbojet, to ramjet in supersonic speeds, to a rocket-ramjet at hypersonic speeds to a pure rocket in outer space.


Fearlessleader85 t1_iy965pz wrote

We have materials that can hold hydrogen well, and it's trivially easy to make an effectively impermeable coating on something like a compressed gas cylinder. But doing the same for a full plane is less simple.

And we have some promising materials for that, like some graphene based stuff. It's not as far out as you suggest. It's just a long way from cheap.


Fearlessleader85 t1_iy9869t wrote

Gold might not be a bad material for it, especially on tubes and engine parts, but I don't know enough about gold playing to know if it's adherence is good enough in a thin film application to coat something like a turbine.

Another problem is hydrogen's flame temp is absolutely insanely hot. Gold has a fairly high melting temp for such a soft metal, but it will need excellent cooling. It's conductivity could help a bunch with that though.

Damn, i wish i was in engine r&d sometimes. All my fiddling with engines is on 4-bangers in my shop. And i don't even have a cnc.


itsbicycle_repairman t1_iy98pri wrote

If that was the case, you'd need to know at what rate it leaked to work out how much fuel you need for a flight, and if the leakage was a "standard" rate over every aircraft. And if it was a linear equation too, but I'd hazard a guess that more pressure = more loss at a higher pressure.


jg727 t1_iy9abwl wrote

A lot of that is intentional release of hydrogen and oxygen.

They cryogenic fuels in rockets, stored at their freezing point. As they slowly warm up/boil off the liquids, the tanks have to hav a way to vent the excess pressure


Stenthal t1_iy9b2k0 wrote

> True, but not by volume.

Generally weight is the bottleneck for aircraft, not volume. If we could trade weight for volume, we'd just make fatter planes.

> I'm not sure if there really is a good or safe way to transport or store hydrogen for air travel.

This is a bigger problem.


haircut50cents t1_iy9crlr wrote

Hydrogen is great per mass but horrible per volume. That's why it has to be cooled down past liquid into slush. Even then the tanks needed are enormous compared to jet fuel used now. Would require a complete redesign of airplanes - maybe larger lifting body aircraft or flying wings.

That would require a more space at airports. Maybe the supply chain is there but rebuilding all the worlds airports? That's a mess.

I do like biofuels because of the mass and volume energy storage and they drop into the supply chain really well.

The best way to stay carbon neutral is always to not build new stuff to replace working stuff. True for cars and I would bet even more so for airplanes.

Interesting discussion though, thank you!


Blissboyz t1_iy9d8uw wrote

Sounds great an all until a engine failure, then the plane becomes a nonnuclear hydrogen bomb.


Fearlessleader85 t1_iy9e3g8 wrote

I was also thinking of much larger lifting bodies, like flying wings. I don't think you'd need to rebuild airports completely, but renovations would for sure be needed. But in that change, you could get some significant benefits, like higher altitude flights with greater ease.

But i disagree with your claim of reusing things rather than building new. For most things like cars, the carbon use of the fuel or energy quickly outstrips the corbon footprint of production. So, continuing to use that refrigerator from 1956 that keeps on chugging is churning out more carbon every few years than building a new fridge. Replacing a car that gets 20 mpg with a new one that gets 30-35 mpg has a very rapid "carbon payback".

If efficiency is more or less constant, sure, keep using the old thing as long as possible. If new versions produce significant improvements, replacement is the best option. The math for these decisions isn't that complex.


Pesto_Nightmare t1_iy9fniu wrote

Fuels like gasoline and kerosene are cheap because they are energy dense products that we just need to pull out of the ground and clean up. Fuels like hydrogen are more expensive because we need to invest the energy that is later extracted by burning or through fuel cells. We technically can use electricity to split water to generate hydrogen, but that process takes electricity, which costs money.


Methylatedcobalamin t1_iy9fnqi wrote

Hydrogen is not an energy source. It takes energy to produce hydrogen. A hydrogen jet engine is still a good deal as whatever the dominant form of energy is there can hydrogen to run the jets.


tyler1128 t1_iy9fvoe wrote

It's highly experimental and we are still trying to do green propulsion engines. All of these engines basically take a fuel, make it explode inside with very fast air going through as well, and throw it out the back to generate thrust. The usual fuel for aircraft would be hydrocarbons, aka oil derived fuel. It's basically a slightly modified kerosine.

Hydrogen can still combust (or explode) in the presence of air. It's actually what made the original space shuttles able to get out of the atmosphere. The exhaust is mostly just water, as H2 + O => H2O (water). Whether this specific strategy will get off the ground is too early to tell (pun intended).


HotTopicRebel t1_iy9h584 wrote

Now show me the lifetime cycle analysis and reliability reports. I'm betting it's not great.


jigokubi t1_iy9ikhx wrote

If they pull this off, it will be the Rolls-Royce of hydrogen engines. Wait...


hazelnut_coffay t1_iy9zdq9 wrote

you do know that the vast majority of hydrogen is manufactured via steam reforming rather than hydrolysis right? there’s a reason why O&G companies are pushing for hydrogen as the next energy source rather than renewables.

steam reforming is methane (ie natural gas) + water -> carbon monoxide + hydrogen

hydrolysis is an energy intensive process. meaning you need to put in more energy than you get out of it. it’s not sustainable at large scale.


brcguy t1_iy9zed5 wrote

It’s more about the storage than the turbine tho. The tanks and fuel lines are the problem way before the combustion chambers. Those need to handle more heat, but shouldn’t be in major danger of hydrogen embrittlement as it’s on fire and mixing with air by then. (I could be wrong it’s been a while since I’ve messed with turbines).


StarDatAssinum t1_iy9zk0m wrote

I heard about this guy who invented an engine that runs on water, man!


hazelnut_coffay t1_iy9zs8m wrote

look up the process used to create most of the hydrogen right now. it’s called steam reforming. it uses natural gas. theres a reason O&G companies are pushing for hydrogen fuel cells as the next energy source.


Fearlessleader85 t1_iy9zzsb wrote

I mean, you could be right, but with the lifetimes we're demanding of aircraft, i think it would behoove us to keep everything from hydrogen embrittlement. Injectors might be the main trouble spot, though.


brcguy t1_iya0urx wrote

Yeah plus I think storing a suitable volume might be a problem too. Just need to make a super efficient electric turbine and then build the whole airframe out of batteries lol.

Who are we kidding - the climate crisis will only be solved by the climate crisis killing half of us. Now I’m sad.


CurtisLeow t1_iya1bbi wrote

Kerosene can't be produced from carbon neutral sources. Kerosene produces soot. Natural gas-powered aircraft are already a thing, by the way. It's a more common fuel than hydrogen.


Fearlessleader85 t1_iya1ctf wrote

I'm no expert on hydrogen containers, but i do believe some of our better options emply ceramic coatings, but they can't generally be pure ceramic, because they can't handle the hoop stress. Also, i think most ceramics still leak a significant amount of hydrogen.


moofunk t1_iya75dw wrote

Considering how long it takes the FAA to certify unleaded fuel, which is supposed to be done by 2030, I can't imagine how long it would take to certify a hydrogen powered plane.


GandalfSwagOff t1_iya9e7k wrote

>It takes energy to produce hydrogen.

What are you even talking about? It takes energy to produce oil, coal, nuclear, solar, geothermal...What is your point? Are you arguing that it takes MORE energy to produce hydrogen?


mces97 t1_iyad5r6 wrote

I'm more concerned about what happens if they need to make an emergency landing, if landing gear don't work? Cause if that tank isn't 100% tested against the type of damage that could make it explode, I would be very concerned getting on a plane.


groveborn t1_iyaf1bx wrote

It depends on how the fuel is used. If it's being burned then it needs to be done in an elemental state (h2 gas or liquid), but if we just need electricity to run the engines, then the hydrogen can be bonded with a metal for easy and safe storage. Just add water to fizz it out.

I suspect the first, rather than the second.


jesset77 t1_iyald09 wrote

>Generally weight is the bottleneck for aircraft, not volume. If we could trade weight for volume, we'd just make fatter planes.

We already tried this though, Blimps have not been terribly successful. Especially the ones kept in the sky via hydrogen. 😋


_toodamnparanoid_ t1_iyas0xp wrote

> fatter planes

Aaaaaaaaare you gonna take me home tonight?

Aaaaaaaaah, down beside red PAPI lights

Aaaaaaaaaaare you gonna let those flaps hang out?

Fat bottomed planes you make the turbine world go round!


Ericus1 t1_iyas72s wrote

Fully synthetic fossil fuels using green energy to manufacture. Still massively energy intensive, would need the same hydrogen as a feedstock, but vastly safer, more stable, uses existing infrastructure, and would be carbon neutral.


Ericus1 t1_iyatfau wrote

Yes. The round-trip conversion to first produce then use hydrogen is significantly less efficient than directly using the electricity or fossil fuels themselves. Problem is batteries aren't energy dense enough for long-range flight and fossils are dirty. However, hydrogen - unless frozen and compressed - also has terrible energy density and requires highly specialized storage and handling. The better solution IMO is not stopping at hydrogen but going to fully synthetic fossil fuels, but either way will require massive surpluses of green power that don't exist yet. Right now 99% of hydrogen comes from natgas.


kinyodas t1_iyay3tn wrote

I live about 20 minutes from where they test - it shakes the earth like nothing I’ve ever experienced.


Dt2_0 t1_iyb7oi7 wrote

Yea it's looking more like the airline industry will transfer to biofuels and work to be carbon neutral than go for non carbon fuels.


CurtisLeow t1_iybmdzp wrote

Fossil fuels are fossil deposits. Some natural gas comes from fossil deposits. There are renewable sources of natural gas, just like there are renewable sources of hydrogen. Although currently most natural gas, and most hydrogen comes from fossil deposits. Most hydrogen isn’t carbon neutral either.


kr0kodil t1_iybuxan wrote

Yes, you’d run into the same issues with hydrogen-powered jets. You need to compress and refrigerate the hydrogen in order to store it in liquid or supercritical form, and you’d need to constantly vent off excess hydrogen when tank temperatures rise.


CurtisLeow t1_iybwccr wrote

And by that standard, hydrogen isn’t carbon neutral either. The vast majority of hydrogen comes from natural gas, as shown in the other Department of Energy article I linked.


Ok_Tree6772 t1_iybxjqd wrote

Rolls won't even be around in a few years, seems like it's just everyone trying to cash out their piece of it.


Cpt_Soban t1_iyc27dl wrote

It's still better using hydrogen derived from fossil fuels from the grid, than burning fossil fuel gas after extracting gas from fossil fuel, then burning it as a fossil fuel.

The net benefit is fewer carbon emissions using hydrogen, with improvements later as the grid transitions.

As I said: we need to transition AWAY from carbon emitting energy.


iWork4Beer t1_iyc363r wrote

Rolls Royce last desperate plea on their stock death march to $0


AffectSweaty927 t1_iycdgp1 wrote

The CIA killing Rolls Royce engineers definitely wasn't on my 2022 bingo card


1funnyguy4fun t1_iycvvjq wrote

Speaking of the containment issue, I read a comment from an engineer that said, “Hydrogen won’t work out because it is a slippery little bastard that is hard to contain and a general pain in the ass to work with.” Seems to be the general consensus from what I have read. In theory, hydrogen as a fuel solves a lot of problems. In practice, you end up creating a lot more problems than you fix.


Ericus1 t1_iydbezv wrote

Environmentalists are not the ones pushing for hydrogen. Look at who actually is pushing it and funding lobbying groups behind it - it's the natgas/fossil fuels industries, desperately trying to push something they can produce and control into these sectors. Same as with heating, other areas of transportation, and storage.


eighty6gt t1_iydd058 wrote

Didn't Kelly try this back at Lockheed;)


Prophet_of_Entropy t1_iydjxk7 wrote

yea, new engine designs wont get past the fact we havent come up with an energy positive way to generate hydrogen. or past the basic physical properties of hydrogen.

so why do this? every company does a bit of green washing now and then.


EmperorArthur t1_iyecwwv wrote

> then build the whole airframe out of batteries


Actually skip the electric engine, just use the fuel to heat the air.

90% sure the US dreamed up a plane like that in the 60s.


EmperorArthur t1_iyedb0t wrote

Unfortunately not. Hydrogen is so tiny it has to be stupidly cold or under insane pressure to be a liquid.

We do it for rockets, but even through all the insulation ice still forms. That killed seven people...