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JadedIdealist t1_iy3r08e wrote

Reply to comment by westbamm in 'Landmark achievement': Rolls-Royce and easyJet hail successful hydrogen jet engine test by Wagamaga

If you include the weight of the container hydrogen goes back to being abysmal though.

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[deleted] t1_iy3s27e wrote

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JadedIdealist t1_iy3smq7 wrote

If you store a low density fuel then your container needs to be bigger (and therefore heavier) to hold the same weight of fuel.

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[deleted] t1_iy3sspo wrote

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dinosaurkiller t1_iy3ugqt wrote

If it’s a bigger tank for the same fuel it’s completely true. The context very much matters and you’re making a lot of assumptions.

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[deleted] t1_iy3ux7z wrote

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RevolutionaryMove357 t1_iy3x901 wrote

Right? Look at rockets. Destin from Smarter Every Day on YT toured a ULA facility and the tanks for hydrogen and other fuels are insanely, insanely thin.

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jdmgto t1_iy44jex wrote

Just… ok… so, no. Rocket fuel tanks do not operate at anything like gaseous hydrogen tank pressures. Every rocket that uses hydrogen fuel is cryogenic, and they are all designed with pressure relief valves specifically so that as the hydrogen boils off the pressure is released. None of them are designed to operate at any significant pressure. Even then, while the actual structural component of the tank is thin, it’s covered in a lot of insulation to prevent the hydrogen from boiling off. Also rockets are designed to be loaded in a single direction, longitudinally and aircraft… aren’t.

Cryogenic hydrogen is just an ungodly pain in the ass to work with which is why every non-rocket utilization of hydrogen as a fuel uses pressurized gaseous hydrogen instead. 

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lestofante t1_iy7lxxl wrote

Yes but also that is why Airbus is researching on this.
They think tech may ready to be able to overcome those issues and are gonna try make 3 different demonstrator, one normal frame that burn hydrogen, one lifting body, and one normal frame but fuel cell propeller.
As they are one of the 2 biggest company about planes, I think they know what they can achieve

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jdmgto t1_iy7s01s wrote

It's not that you can't make a hydrogen powered aircraft, you can. The problem is that barring the government just straight up banning conventionally powered jets they won't be able to compete. It is just a physical fact that hydrogen’s energy density is awful and working with it is painful. Any aircraft running on hydrogen will either carry less cargo (people or stuff) or have significantly shorter range or some combo of both.

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jdmgto t1_iy43exb wrote

>Carbon fibre, kevlar and other materiels are good for the job and weigh less than convential plane fuel tanks.

No, they don’t, because conventional plane fuel tanks are the structure of the wing. Never mind that they aren’t the right shape. Super high pressure storage containers are spheres or cylinders for a reason. Aircraft fuel tanks are long flat rectangles, just about the worst shape to make a pressure vessel out of.

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[deleted] t1_iy45do5 wrote

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jdmgto t1_iy47q2c wrote

It’s only strange if you have no clue how modern jetliners function, are built, or how hydrogen storage works. Fuel is stored in the wing because fuel is a liquid and can fill odd shapes that are inefficient for anything else. Wings are necessary for aircraft and by their construction have a lot of odd unusable space for cargo. They’re easy to use for fuel storage. Storing fuel in the wing structure is popular because it’s effectively weightless, you had to build the structure regardless. The work to turn them into fuel tanks is pretty trivial and largely what you’d have to do for a single purpose tank. Second, it frees up the fuselage for passengers and cargo, the stuff that makes money. Fuel storage in the fuselage is taking up space that you now can’t sell to make money. And no, there isn’t enough room in the wings for cylinder storage, at least not useful storage. The structure of the wings, the part that holds the fuel is made up of various box girders which are rectangular. The only pressure tanks you could fit in them would be many long, thin, incredibly wasteful tanks that add a lot of points of failure for not a lot of fuel storage.

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[deleted] t1_iy48zr3 wrote

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jdmgto t1_iy4eywf wrote

It’s condescending because you don’t understand the fundamental reasons why aircraft are built the way they are, how hydrogen storage works, or just basic concepts but you speak authoritatively as if you do. Do you know why the tank in the 737’s wing is that shape? Because the slats and flaps and their equipment take up the leading and trailing edges of the wing. The fuel is contained in the long, rectangular structural box that runs down the center of the wing. That’s what I’m talking about, you don’t understand even the basics of how airplanes work. It’s got nothing to do with balance. 

And no, it couldn’t be used for cargo. Aside from the structural problems of opening that up enough to pack it full of bags which are just horrifying. Do you know how cold that space would be? I doubt passengers would be ok with having their bags frozen solid. Never mind the bag handling issues as you’ve gotta individually Jenga the bags into the wing every time you load it versus chucking it in the hold.

There is a reason about the only place hydrogen is regularly used as a fuel is rockets, and even that’s not universal. Could you build a hydrogen powered aircraft? Sure, but you’ll also see the cost of air travel increase dramatically. Like it or not, baring governments just outlawing conventional jets entirely in favor of hydrogen ones, no ones gonna buy them. 

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