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Ultra-light liquid hydrogen tanks promise to make jet fuel obsolete
- zeristor 5y agoVery interesting, i guess a number of technologies would need to be improved hydrogen fuel cells, and electric motors, for aircraft each of those could yield improvements. Would the tanks need to go in the main fuselage, or would this be a chance for flying wing designs to be used?
- harg 5y agoI guess one could also just burn the hydrogen directly in a jet engine, which might be lighter than fuel cells and motors
- giantg2 5y agoWhy do you guess that? My assumption is that the deflagrenation rate is way too fast compared to jet fuel for that to work.
- namibj 5y agoGas turbine power plants are built already that will just need the combustor switched out to be switched from current nat gas fuel to eventually pure H2 in some seasonal storage projects. Gas turbines themselves have no problem with hydrogen as a fuel, it's just the burners/fuel injectors/flame holders that need appropriate adjustments. Also, they can fly higher, because hydrogen is more flammable and will burn even in extremely lean mix that happens at very high altitude.
- giantg2 5y agoI think the engine design has to be changed too. Basically a full engine swap. I initially saw their comment as meaning adapting the existing engines to use hydrogen. I see now that they might just mean using engines designed for hydrogen, not the jet engines we have today that use jet fuel. Yeah, the gas turbines would be easy to convert compared to jet engines.
- namibj 5y agoAirliner jet engines are just gas turbines with a ducted fan in place of the generator, and all the heat exchangers/air filters stripped. Well, at least some power plant gas turbines share the power core with airplane turbofan engines. Technically they likely differ somewhat in the power turbine, as jet thrust from the exhaust is wasted on the ground and thus they try to extract more of the exhaust's power than for a plane, where it's a trade-off between turbine/fan weight and fuel efficiency from essentially gearing the exhaust velocity down to barely above flight speed (having double the exhaust velocity costs 4x the power but only gives 2x the thrust).
- jillesvangurp 5y agoThere are rockets that run on hydrogen. There have been jet designs that run on it. There is even a company in the UK that is building combustion engines for heavy digging equipment that burn hydrogen instead of diesel. It's a great fuel. Fuel cells are potentially more efficient though.
- twobitshifter 5y agoFrom the tank shown in the article it looks like it would fit best in the fuselage. Hypoint is developing the fuel cells, and they’ve partnered with someone else on the tanks. Electric motors for small planes don’t appear to be a challenge. Beta technologies out of Burlington Vermont is flying electric planes with lithium batteries today. So in that case, it is really about switching the energy source for the plane. I think what’s missing is all the hydrogen infrastructure to get cryogenic hydrogen to the runway. But that’s a classic chicken and the egg problem.
- phkamp 5y agoI hope they have anti-sloshing-baffles in their design, because liquid hydrogen has low viscosity, and you really do not want it sloshing around without energy dissipation, in particular not during take-of or landing.
- netsharc 5y agoI'm sure they don't need an Internet comment to tell them what they already know...
- namibj 5y agoMaybe a piston pressurized on the "empty" side with gaseous cryogenic hydrogen? The forces shouldn't be an issue, at least for cylindrical tanks where adding an atmosphere or 5 in internal overpressure capability (relative to outside) is quite cheap once you already have to stay in shape filled or not.
- dotancohen 5y agoHow would you actuate that piston? Drill through the hydrogen tank to run hydraulic lines? That's a nice place for hydrogen leaks. Electric? In a hydrogen tank?
- namibj 5y agoGaseous hydrogen. The initial idea was for ensuring feed in case of negative G's, as some high-efficiency subsonic airfoils are unstable in the high-lift orientation, so recovery from malfunction/turbulence would start with flipping to negative G's followed by rolling over into inverted cruise. That would of course only be possible if the tank can be made to reliably feed independent of gravity, and the otherwise-typical bladder (AFAIK pressurized by gas/air between the bladder and the structural tank) doesn't work for LH2, due to cryogenic temperatures making all remotely normal materials very brittle. But a low-speed piston seal that only has notable pressure across it during active roll maneuvers (centripetal force from the roll-rotation) and uncoordinated turns, between LH2 and gaseous H2 with the latter slightly warmer than the former... it's not like you'd want the empty part of the cryogenic tank to be at non-cryogenic temperatures or filled with something that'd contaminate your LH2.
- tomohawk 5y agoWhy not also in cars and trucks, then?
- giantg2 5y agoIt sounds like this requires cryogenic cooling equipment. That might mean there are strict fueling and defueling procedures that are more applicable to the already highly procedure-ized flight industry. Also, if that tank ruptured during a crash, then it would be catastrophic. Crashes happen much less frequently in commercial aviation vs on the roadways. Hydride tanks would be a much safer option for roads. However they weigh more with less storage and would not be suitable for most aircraft. Plus, it seems that due to international nuclear weapons treaties, one of the components of the hydride tanks is difficult to source.
- Zigurd 5y agoThe danger from fuel tanks rupturing is hard to intuit. Hydrogen will gasify and escape upward. But the hydrogen tanks themselves could fragment and be propelled by the pressure in the tanks. It is an open question whether this is worse than kerosine escaping fuel tanks and pooling around a crashed plane.
- someguydave 5y agoat least kerosene burns with a visible flame…
- rbanffy 5y agoNoise is just one of the many reasons you were not allowed less than a couple kilometres from a shuttle launch.
- giantg2 5y agoSort of a moot comparison, right? We can see a flame from kerosene, but kerosene burns slowly. We can't see a flame for hydrogen, but it is gaseous and burns so fast that it essentially detonates. Given that small timescale, that means we wouldn't be able to act on that information (seeing a flame) anyways.
- doctor_eval 5y agoNot sure I’d want to fly New York - SFO on a Dash-8 !
- Kaibeezy 5y agoGive me a big comfy seat and I’d take it every time. Zero carbon emissions = zero guilt about flying business class. Dash-8 sturdy airframe does great in turbulence. Nap time. Zzzzz.
- sokoloff 5y agoEspecially since it’d end up being something like New York to Kansas City to Las Vegas/Salt Lake City to San Francisco.
- robonerd 5y agoWhy? Prop phobia? They're about as comfortable as 737s in my experience.
- captainredbeard 5y agoSpeed. Otherwise the dash 8 is the best. Lovely plane.
- doctor_eval 5y agoHaha, no not prop phobia, I just don’t like the idea of such a very long flight in a relatively small aircraft, just for comfort reasons. I wouldn’t enjoy it in a 737 either.
- fxj 5y agoDoes it also work for hydrazine? Then we could have cheap sub-orbital spaceflight. This would be much faster than plain old intercontinental supersonic flights.
- robonerd 5y agoIt doesn't matter how great your tanks are, hydrazine will never be suitable for commercial passenger flights. It's insanely toxic and hazardous to deal with. Forget the passengers, that stuff is dangerous for everybody on the ground too. It's not cheap either, I'm not sure why you'd think cheap sub-orbital flights are gated by hydrazine tanks. Also, old intercontinental supersonic flights aren't done anymore, the Concorde is gone and nothing replaced it. It will likely never be an economically viable niche, particularly since the utility of video streaming has been so conclusively demonstrated, soaking up much of the demand for business travel.
- zeristor 5y agoI take it only cars and trains can use regenerative breaking. Or maybe ships and planes could use it to reduce speed, as when an aircraft comes into land, or a ship coming into port. Though with that amount of power batteries wouldn’t be able to charge fast enough, and super capacitors would be added complexity.
- jodrellblank 5y agoSailboats with electric motors instead of diesel engines can use the motors to regenerate power; when under sail the motors are dragged backwards through the water forcing them to turn. (I don't know if that's useful enough for 'braking' as boats have fairly high mass and lots of inertia and travel slowly as it is, so gradually slowing down over a very long distance would just be annoying compared to a burst of reverse thrust to slow them down sharply)
- Chris2048 5y agoMaybe a space elevator could, But I'm not sure how a rocket would reclaim energy - from air drag on the way down?
- LargoLasskhyfv 5y agoWhy not? https://en.wikipedia.org/wiki/Ram_air_turbine https://en.wikipedia.org/wiki/Ram_air_turbine s exist :-)
- H8crilA 5y agoAirplanes already use "regenerative braking". When you're coming in to land the airspeed and altitude is used to move the aircraft forward, with reduced throttle on the engine. In fact it could be reduced to exactly idle, but that's just not the optimal setting, and in the final phase of the flight also not the safest setting (spooling up time of a turbojet engine depends a lot on the initial rpm, in case you need to go-around). There's no need for a capacitor when you have gravity and altitude.
- bell-cot 5y agoThe article's title seems very misleading. Even a magically zero-weight airliner hydrogen tank will be physically huge. Just compare cross-section diagrams for rockets running kerosene/oxygen engines with rockets running hydrogen/oxygen engines. (Use the oxygen tank sizes as your reference standard.) Now recall that jet fuel is basically kerosene, most of which is stored in tanks in the wings - where cylindrical liquid hydrogen tanks would be a poor fit. Huge cylinders added to an aircraft will also add huge drag, or eat up much of your passenger/cargo space. EDIT - OOPS, I didn't spot the article's emphasis on cryogenic (liquid, at 20 K, −253 °C or −423 °F) hydrogen. Ask a rocket scientist how safe, easy, and cheap that stuff is to handle. Current rockets mostly use kerosene instead, in spite of kerosene's far-worse efficiency in $millions-per-launch rocket engines, to avoid dealing with liquid hydrogen.
- audunw 5y agoYeah, as always, they forget to mention volumetric energy density. Big red flag. There's some concepts that may work around that, like a blended-wing design. Airbus seems to think it's viable. https://www.airbus.com/en/innovation/zero-emission/hydrogen/zeroe https://www.airbus.com/en/innovation/zero-emission/hydrogen/... Also, a hydrogen fuel cell based plane could be designed to fly much more efficiently than a regular turbofan plane. For instance, something like the Maxwell X-57 where you have very thin, low-drag wings, and use small electric propellers to provide the extra lift needed during take-off and landing. Electric propulsion enables new designs that wasn't possible with turbofans, and I'm sure electric planes will end up looking quite different from todays planes. But it'll take a couple of decades to figure it out.
- bell-cot 5y agoFrom some quick searches, it sounds like modern jet engines are up to ~40% energy efficient, measuring kerosene ==> thrust. I'll guess that production-aircraft-grade hydrogen fuel cells won't get past 85% efficient (hydrogen ==> electricity). Then you have the inefficiencies of the electric motor, and the propeller. Maybe 60% total efficiency could be achieved? (So 1.5x the current-generation commercial jet engine efficiency.) My point: Your "much more efficient" looks correct, as language to use among informed engineers. But risky to use around managers, customers, etc. - who'll quickly develop fantasies of around-the-world jumbo jet flights, powered by the hydrogen tank in their carry-on duffel bag.
- mrtesthah 5y agoWhat’s the advantage of this over Fraunhofer’s ester-based hydrogen storage cartridge system (Power Paste)? Greater effective wattage? https://www.electrive.com/2021/02/02/fraunhofer-develops-hydrogen-storage-paste/ https://www.electrive.com/2021/02/02/fraunhofer-develops-hyd...
- torginus 5y agoWell, the article states that it uses magnesium hydride (MgH2), and the atomic weight of Magnesium is 12, so it means that such a compound is 7 times less weight efficient if we take into account the need for storing 1 Mg atom for 2 H.
- transfire 5y agoIf solid state batteries double capacity vs weight in the next 5 to 10 years will this still be relevant?
- JCM9 5y agoHeadline is rather hyperbolic. The challenge in replacing jet fuel is that on energy density (by volume and weight) jet fuel is extremely high compared to just about anything else. Also, shedding weight in flight is key to long range travel to make the engineering work. That perpetually limits what’s possible with anything powered by batteries. Until those two problems are solved we’re not going to see anything beyond short range travel switching off jet fuel.
- rbanffy 5y agoI believe that’s better news for DC-X, VentureStar, and Skylon spaceplanes than it is to passenger transport. OTOH, if we manage to make SSTO practical, we can think of single-stage suborbital passenger carriers, which are much more interesting than using Starship for that.
- LargoLasskhyfv 5y agoThe Skylon people already thought of that, and called it Lapcat A2, or something. Basically the Sabre engine from Skylon without the rocket part, called Scimitar. https://en.wikipedia.org/wiki/Reaction_Engines_LAPCAT_A2 https://en.wikipedia.org/wiki/Reaction_Engines_LAPCAT_A2 Rawrrr
- rbanffy 5y agoI always thought of it as being Sabre without the LOX feed. Sounds easier to build.
- stevespang 5y ago
- jessaustin 5y agoThe company says they've tested leak-tight, even through several* cryo-thermal pressure cycles.* Unless they left out the word "thousand" after the word "several", this technology doesn't seem too close to market.
- incomingpain 5y agoThis will never happen. What will inevitably be what happens is that battery systems will be charged at airports and be in some standard format that can be swapped not unlike the lifts that do food or luggage.
- clouddrover 5y agoHydrogen plane: https://newatlas.com/aircraft/hydrogen-electric-hy4-passenger-aircraft-sets-altitude-record/ https://newatlas.com/aircraft/hydrogen-electric-hy4-passenge... Another one: https://www.bbc.com/future/article/20210401-the-worlds-first-commercial-hydrogen-plane https://www.bbc.com/future/article/20210401-the-worlds-first... And this one was built in 1988: https://en.wikipedia.org/wiki/Tupolev_Tu-155 https://en.wikipedia.org/wiki/Tupolev_Tu-155
- incomingpain 5y agoYou didn't really explain your position, if I am getting you right, you're saying that there have been a few 1 offs and after they built them to realized how terrible they are and never built a second one? I also find it hilarious that 7,000ft is an achievement. Meanwhile, electric planes have literally went around the world. https://en.wikipedia.org/wiki/Solar_Impulse https://en.wikipedia.org/wiki/Solar_Impulse
- clouddrover 5y agoThe point is we've gone from your "will never happen" to "is happening" and "will continue to happen". Hydrogen fuel cell aircraft will be doing commercial passenger flights in a couple of years. How soon do you think solar aircraft will be doing commercial passenger flights?
- incomingpain 5y ago>The point is we've gone from your "will never happen" to "is happening" and "will continue to happen". Hydrogen fuel cell aircraft will be doing commercial passenger flights in a couple of years. So you disproved your own argument and are only arguing over semantics?
- baybal2 5y ago