Hydrogen powered passenger planes? Is it possible? - Page 1
Forum section: electronics / general

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 05:29:26 pm
content: Airbus is claiming they "could" have zero-emissions hydrogen powered aircraft in the skies soon. While this sound wonderful, I'm wondering if the folks at Airbus slept through their physics class? Is this as feasible as nuclear powered aircraft? We know hydrogen powered cars (with the technology we have) are a stupid idea. But what about hydrogen powered planes? Just as stupid as Musk's EV semi-trucks and nuclear powered aircraft? Or does the physics show that this is a silly as a shovel with a rope handle?https://www.flyertalk.com/articles/could-hydrogen-powered-airliners-become-reality-by-2030.htmlhttps://youtu.be/f7MzFfuNOtY

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 24, 2020, 05:44:49 pm
content: And the first hydrogen fueled aircraft that flies, please name it the Hindenburg 2.Now seriously. All of the issues found in the use of H2 for automotive use, here are amplified by an order of magnitude: the low caloric content as compared to Jet-A, the fact that the tanks themselves could weight more than the fuel itself, or that you require to reform hydrocarbons to actually obtain hydrogen.

author: richard.cs
author_rank: Super Contributor
timestamp: July 24, 2020, 05:52:39 pm
content: What I read a few years back on hydrogen planes revolved around cryogenic H2. The intention was that boiling off the H2 would be used to chill the engine air intake (after the first compressor maybe?) giving some mild efficiency gains. The major engineering challenge was claimed to be that the aircraft had to be redesigned to be "fat" with all the fuel in the fuselage because it's not very dense and cryro tanks need a low surface area to volume ratio.It was a while back and I've not looked at it since, but it seemed plausible though less convenient than liquid hydrocarbons.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 05:54:05 pm
content: Quote from: schmitt trigger on July 24, 2020, 05:44:49 pmGlad someone else made took cheap-shot. I was going to make it, but didn't want to detract from the serious question I was asking.

author: Marco
author_rank: Super Contributor
timestamp: July 24, 2020, 05:58:28 pm
content: Quote from: DougSpindler on July 24, 2020, 05:29:26 pmPlanes can be fuelled shortly before take off. This might make relatively light weight cryogenic hydrogen storage practical. Boiling off what's left after landing, or defuelling the plane.They don't have to stand in the sun with a filled tank for a week like a car.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 06:06:10 pm
content: Quote from: richard.cs on July 24, 2020, 05:52:39 pmAirbus says the planes will be powered by hydrogen made from sun and wind. Sounds wonderful doesn't it? And then there's reality.

author: Marco
author_rank: Super Contributor
timestamp: July 24, 2020, 06:27:03 pm
content: If you raise the taxes on the alternatives high enough then it's realistic ... it's not like fuel costs are a huge part of ticket prices.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 06:34:25 pm
content: Quote from: Marco on July 24, 2020, 06:27:03 pmHow does raising the taxes change the laws of physics? We know we can build and fly nuclear powered passenger planes. We know batter and solar cell powered planes are not possible with current technology. Hydrogen powered cars are possible but not feasible. So what about hydrogen powered passenger planes? They are possible, but are they practical as Elon's battery powered semi-trucks. Where 90% of the cargo spaces is for the batteries and 10% is for the cargo.

author: Marco
author_rank: Super Contributor
timestamp: July 24, 2020, 07:35:51 pm
content: Cryogenic hydrogen is stored at atmospheric pressure, it doesn't need heavy tanks, just well insulated ones.Hydrogen in planes has an entire different set of use conditions than in a car.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 07:44:09 pm
content: Quote from: Marco on July 24, 2020, 07:35:51 pmJust how far can a passenger plane fly on a fill-up of Cryogenic hydrogen? Is there even enough energy in a tank to move the plane?

author: ejeffrey
author_rank: Super Contributor
timestamp: July 24, 2020, 08:04:08 pm
content: Quote from: DougSpindler on July 24, 2020, 07:44:09 pmWell, LH2 has 2-3x the energy per weight of hydrocarbons, but 1/4 the energy per volume. Weight is a bigger issue for airplanes -- you can make the fuselage a bit bigger to add a lot of volume, drag is still mostly controlled by how much lift you need to overcome gravity. But increasing the fuselage size adds weight as well, and H2 storage tanks will weight more than jet fuel tanks. That would cut into your weight savings, and the aerodynamic cost of the fuselage size isn't zero either.My guess as a non-expert? you would need a designed from scratch airframe, but it would work -- you could get reasonable range and cargo capacity out of a hydrogen fueled aircraft. It also solves some of the problems that hydrogen cars face: you only need fueling infrastructure at major airports, fuel before departure makes cryogenic storage more feasible. I don't know the story on hydrogen turbine engines in terms of efficiency or performance.But I am not sure if there is much point. Biofuel or synthetic hydrocarbon fuels produced from renewable electricity both seem like better options. They aren't terribly efficient so there seem to be better long term options for ground transportation. But for aviation it makes sense to leave your inefficiency on the ground.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 08:18:57 pm
content: Quote from: ejeffrey on July 24, 2020, 08:04:08 pmVery nice reply, thank you.Airbus is saying they are going to do it. Like EVs it is until the infrastructure is built it will flights will be limited to a few airports. I could see this working with flights on the East or West coast of the US. SF to LA. Boston to NY. NY to Florida. SF, LA and Orlando would have the sun or wind to produce the fuels. But won't the have the same technological issues providing fuel for cars have which make the cost of producing, compressing, storing and transferring hydrogen to the plane uneconomical?

author: coppice
author_rank: Super Contributor
timestamp: July 24, 2020, 08:31:54 pm
content: Quote from: DougSpindler on July 24, 2020, 08:18:57 pmSuch a radically new aircraft probably won't roll out very quickly. People will want to see how the first few planes perform on a few key routes. So, there will probably be plenty of time to roll out of ground support across the world's airports.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 24, 2020, 09:26:14 pm
content: Quote from: coppice on July 24, 2020, 08:31:54 pmBut do you think we/Airbus has the technology to do it where it would make sense? Or is this something where the laws of physics have to be broken to work?With cars

author: coppice
author_rank: Super Contributor
timestamp: July 24, 2020, 09:36:37 pm
content: Quote from: DougSpindler on July 24, 2020, 09:26:14 pmIt seems feasible to adapt both the engines and the tanks of a modern plane for cryogenic hydrogen, although a lot more space would be needed for the tanks. The real question is why this would make any sense? Hydrogen cars make no sense, as if you re making a recyclable fuel you might as well make a liquid one, like ethanol. The same is true for aviation fuel.

author: Gyro
author_rank: Super Contributor
timestamp: July 25, 2020, 11:04:57 am
content: I suspect they'd have to spend rather more time de-icing planes, especially if they'd been delayed on stand for a significant period.

author: coppice
author_rank: Super Contributor
timestamp: July 25, 2020, 11:08:38 am
content: Quote from: Gyro on July 25, 2020, 11:04:57 amYou can't just fill a big plane at the last minute. It takes a couple of hours of continuous pumping to fill a current large aircraft.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 25, 2020, 02:43:06 pm
content: I remember reading about hybrid aircraft that used helium to provide a large part of the lift so that the wings and engines can be much smaller. Presumably hydrogen could be used for cargo aircraft on overseas routes.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 25, 2020, 02:44:05 pm
content: It will be interesting to see if the folks at Airbus deliver. They think they will be. Selling hydrogen powered planes in 10 years.

author: nctnico
author_rank: Super Contributor
timestamp: July 25, 2020, 05:29:27 pm
content: Quote from: DougSpindler on July 24, 2020, 05:29:26 pmIt is funny how you always claim 'laws of physics' but never enlighten us with a thourough mathematical analysis to show why you are right.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 25, 2020, 05:48:27 pm
content: Quote from: nctnico on July 25, 2020, 05:29:27 pmNever claimed I was right, I just asked the question. Look at the heading for this post. Do you see it is in the form of a question and not a statement?Aren't you that person from the Netherlands that a couple of years ago was telling us the bio-fuels will be powering the world? How's that working out? No where nears as good as what you were promoting. Are you still promoting it? Or what are you promoting now?

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 25, 2020, 08:50:13 pm
content: Quote from: DougSpindler on July 25, 2020, 05:48:27 pmWorking a lot better than hydrogen powered and electric aircraft - there have been many flights powered by biofuels.https://en.wikipedia.org/wiki/Aviation_biofuel#Commercial_flightsInvestment in biofuels for aircraft, however, will be way down because demand for passenger flights has gone way down.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 26, 2020, 03:29:26 am
content: Quote from: NiHaoMike on July 25, 2020, 08:50:13 pmBut Airbus isn't going to build bio-fuel planes. They said they will be building hydrogen powered plans from hydrogen created at the airports from solar and wind. Now is that doable? Do you think the airlines will add hydrogen fueled Airbuses to their fleet?

author: sleemanj
author_rank: Super Contributor
timestamp: July 26, 2020, 04:25:01 am
content: Quote from: coppice on July 25, 2020, 11:08:38 amA stackexchange answer gives about half an hour to fill from dry a 787-8 using two 35psi pump trucks.https://aviation.stackexchange.com/questions/15955/how-much-time-it-will-take-a-b787-to-fuel-completely-when-empty

author: DougSpindler
author_rank: Super Contributor
timestamp: July 26, 2020, 04:33:09 am
content: Quote from: sleemanj on July 26, 2020, 04:25:01 amAnd what about for hydrogen?

author: f4eru
author_rank: Super Contributor
timestamp: July 26, 2020, 09:18:06 am
content: and what about BEV planes?That is already coming for small GA planes, and we can expect a battery improvement in gravimetric specific energy of perhaps 2x in the next 10 years, so there may be small regional jets as BEV...

author: coppice
author_rank: Super Contributor
timestamp: July 26, 2020, 11:07:24 am
content: Quote from: sleemanj on July 26, 2020, 04:25:01 amA quick Google seems seem to show figures a little under an hour for a 747. I based my 2 hour figure on what people who refuel aircraft at large airports, where all fueling ports on the plane are used, have told me about practical refueling of the 747 and A380. Perhaps various factors mean the achievable filling rate is a lot slower than the theoretical one.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 26, 2020, 02:52:43 pm
content: A quick Goggle search indicates that a 747 carries in excess of 380,000 pounds of JET-A.Loading that much fuel in under an hour is very fast indeed!

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 26, 2020, 03:04:08 pm
content: It's also worth mentioning that commercial aircraft are rarely filled to full - the extra weight is expensive. The amount of fuel actually loaded for a flight is the calculated amount needed plus several safety margins.

author: coppice
author_rank: Super Contributor
timestamp: July 26, 2020, 03:06:52 pm
content: Quote from: NiHaoMike on July 26, 2020, 03:04:08 pmThat's true, and some 747s only fly for an hour on super high traffic routes. Most planes can't land safely with full tanks, so its absolutely necessary to only part fill the tanks on short routes. However, most big planes these days are build for extreme range, because that is the kind of flight that dominates in their market.

author: richard.cs
author_rank: Super Contributor
timestamp: July 26, 2020, 04:34:58 pm
content: Quote from: coppice on July 26, 2020, 03:06:52 pmWhich is an excellent way to "life" the airframe by putting a lot of pressurisation cycles on it over a fairly short operating period. That was a contributing factor to Aloha flight 243 - the famous open-top 737, or at least why that airline encountered the manufacturing and design defect before others.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 26, 2020, 04:51:40 pm
content: Quote from: richard.cs on July 26, 2020, 04:34:58 pmAnd Japan Airlines Flight 123.Kyu Sakamoto, who was famous for the hit song "Ue o Muite Arukō" or "Sukiyaki" was killed on that flight.

author: coppice
author_rank: Super Contributor
timestamp: July 26, 2020, 07:52:34 pm
content: Quote from: richard.cs on July 26, 2020, 04:34:58 pmLanding cycles gets factored into the plane's economics and service schedule. Things only go wrong when the predictive models used to set those service schedules are flawed. Some short routes just carry thousands of people each day, with a 747 leaving every hour or so. With that level of traffic I assume its easy to pay for new planes.

author: richard.cs
author_rank: Super Contributor
timestamp: July 26, 2020, 09:43:31 pm
content: Quote from: coppice on July 26, 2020, 07:52:34 pmIndeed. I'd kind of assumed they would try to get the most out of the whole plane, so lifeing the fuselage when there's still usable hours on other components seems non optimal. Maybe that's done by changing around routes or selling the aircraft, or maybe it's just not worthwhile. No idea.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 26, 2020, 10:21:14 pm
content: There are engineering solutions to the problems of hydrogen as an air fuel. The question is, do those solutions have a market.One example. Hydrogen has low density, which implies high volume and thence high drag. But drag can be reduced by reducing speed and it is a square law relation so you get a factor of four reduction by cutting speed in half. Low density may also imply shorter range, implying higher numbers of flight cycles and increasing fatigue issues. But only if you fly at high altitude.So one solution might be a 300 kph airliner that flies at under 3200 meters altitude.This is an extreme case, but I think the answer is that it will be very difficult and maybe impossible to make a marketable hydrogen powered airplane. Maybe it will end up like the Concorde and to some extent the A380. A plane that will fly, and that is right on the border of marketable. Though in the end both of those aircraft ended up as economic failures. Development + operational costs more than revenues.

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2020, 07:30:22 pm
content: Quote from: CatalinaWOW on July 26, 2020, 10:21:14 pmThat is true because fossil fuel is so cheap. Once fossil fuels get heavily taxed (or simply run out) the alternatives become commercially viable. But the technology needs to be ready first so it is understandable that development has already started.

author: SkyMaster
author_rank: Frequent Contributor
timestamp: July 27, 2020, 08:02:11 pm
content: Quote from: nctnico on July 27, 2020, 07:30:22 pmIsn't the vast majority of hydrogen produced from fossil fuel?It is interesting to see that all the alternative sources of energy always use crude oil, or another form of fossil fuel, in their processes.

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2020, 08:30:11 pm
content: Quote from: SkyMaster on July 27, 2020, 08:02:11 pmYes and no. Hydrogen is a good energy storage medium compared to batteries. When it is in a tank you can keep it there, ship it over long distances and the energy transfer is very fast (unlike batteries). Making hydrogen from solar & wind energy is a promising direction; it looks like Australia is heading towards becoming a large hydrogen producer. On the other hand making hydrogen from fossil fuels allows to pump the CO2 (and whatever else isn't needed) back into the well and there are no NOx and sulphur emissions. I've been saying this for the last 20 years: every last bit of fossil fuels will be used. Until recently my thinking was that the resulting CO2 would end up in the atmosphere but turning fossil fuels into hydrogen (near a well or CO2 storage facility) is a good way to avoid that.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 27, 2020, 08:35:54 pm
content: Isn't most hydrogen produced today from fossil fuels? Isn't that because it is far cheaper that from sun and wind?And why has no one considered what would happen if we dump all of that extra oxygen into our atmosphere? That would bring us back to prehistoric times. Just think about the insect problem we would have. Imagine trying to have a picnic with flies and ant a foot long going after your food.

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2020, 09:00:49 pm
content: Quote from: DougSpindler on July 27, 2020, 08:35:54 pmRead up on basic chemistry before jumping to crazy conclusions!

author: tom66
author_rank: Super Contributor
timestamp: July 27, 2020, 09:11:21 pm
content: Hydrogen is mostly produced by steam reforming natural gas.But there are some prototype plants that use excess wind power at night to produce hydrogen, this hydrogen is then pumped into the natural gas infrastructure and burned in conventional water heating boilers (in some ratio like 20% H2 to 80% CH4).They have been replacing gas pipes all over where I live with plastic pipes to prepare for a mixed hydrogen grid ... it is a massive undertaking.Presumably it would be possible to produce aviation grade H2 (if it would even be different from regular H2, maybe less impurity) using a similar method but would the cost ever be worth it? Electrolysis is extremely expensive and efficient electrolysis requires techniques similar to fuel cells so if you are talking about something like a 100MW electrolysis plant the input energy is still at least 150MW and the cost is in enormous platinum electrode electrolysis machines. Not to mention the freshwater consumption - not exactly common in desert climates.As for aircraft I think some form of synthetic fuel or a biofuel might make most sense. Algae fuels were quite promising but they aren't cost competitive with fossil fuels and may well not be for many decades. One way to push this along would be to require airlines to commit to using biofuels of some % by some date in the future. It would create an immediate economic demand. Sadly that is not happening yet.

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2020, 09:18:57 pm
content: Quote from: tom66 on July 27, 2020, 09:11:21 pmIt is a good thing it isn't happening yet; most of the current bio-fuels are made from crops grown specifically for fuel which affects food supply. That needs to change first. This change process is ongoing by banning the worst bio-fuels (palm oil IIRC) which then make way for bio-fuels which co-exist with food production. In theory fuel in the EU should have 10% of bio-fuel mixed in but in practise it is around 7% because there isn't enough low-impact bio-fuel available. Mandating airlines to use bio-fuel would create a supply problem at this time. However it is reasonable to assume that in the next 5 to 10 years airlines will be forced to use bio-fuels.

author: tom66
author_rank: Super Contributor
timestamp: July 27, 2020, 09:23:34 pm
content: Quote from: nctnico on July 27, 2020, 09:18:57 pmYes, that's why I mentioned algae biofuels, they're generally grown in large vats with the lipid oils extracted from the top or by drying out the algae. These have minimal impact on the biosphere and have minimal land use requirements. If you account for land use changes many biofuels are actually as bad or worse than burning fossil fuels. Got to be careful here.Prototype flights have been made using algae biofuels but the technology development seems to have been significantly reduced by the oil price crash of 2015-16 (and then subsequent slump due to COVID).

author: JohnG
author_rank: Frequent Contributor
timestamp: July 27, 2020, 09:29:22 pm
content: It could only make sense if the plane is electric.Then you can have a very high (>90%) electrical to mechanical conversion, you can use materials that don't need to run red-hot or hotter, and you can keep the conversion efficiency high over a very wide range (much more so than a turbofan). It also becomes cost-effective to distribute motors so you can have much better control over airflow.You can also do regenerative braking on your descent!I'm not saying it does make sense, I'm only saying it could make sense. Personally, if they can make cost effective fuel cells that work with fuels that are liquid not to far from STP, it is much more likely to happen. Motors and power electronics are much farther along.John

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2020, 09:31:36 pm
content: Quote from: tom66 on July 27, 2020, 09:23:34 pmAFAIK algea biofuels have been put on hold because it turned out getting an industrial scale process going is extremely hard. But I have not checked what has happened when it comes to algea biofuels for the past 1 or 2 years.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 27, 2020, 10:42:52 pm
content: Quote from: nctnico on July 27, 2020, 09:00:49 pmDude, it's more than just chemistry. It's biology or more specifically Paleobiochemistry.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 27, 2020, 10:44:55 pm
content: Quote from: nctnico on July 27, 2020, 09:31:36 pmAren't you the bloke that was telling us three years ago algea biofuels are going to power the world. You were promoting the heck out of a company in the Netherlands that was going to make it happen. What went wrong?

author: DougSpindler
author_rank: Super Contributor
timestamp: July 27, 2020, 10:47:39 pm
content: Quote from: JohnG on July 27, 2020, 09:29:22 pmThe folks at Airbus said in 10 years they will have a plane powered by hydrogen made for solar and wind. Are these the words of a someone who knows science? Or some MBA that never took a physics class?

author: khach
author_rank: Contributor
timestamp: July 27, 2020, 10:56:40 pm
content: Old soviet TU-155https://en.wikipedia.org/wiki/Tupolev_Tu-155

author: DougSpindler
author_rank: Super Contributor
timestamp: July 27, 2020, 11:02:20 pm
content: Quote from: khach on July 27, 2020, 10:56:40 pmUmm did you read what type of fuel was used?"The Tu-155 first flew on 15 April 1988. It used hydrogen fuel and later liquified natural gas (LNG)." LNG is not the same as hydrogen.

author: Syntax Error
author_rank: Frequent Contributor
timestamp: July 27, 2020, 11:04:17 pm
content: Well this not Hydrogen, but still a noteworthy and interesting development in super endurance solar aviation.BAe Systems PHASA35https://www.theengineer.co.uk/phasa-35-maiden-flight-bae-systems/

author: khach
author_rank: Contributor
timestamp: July 27, 2020, 11:14:12 pm
content: Quote from: DougSpindler on July 27, 2020, 11:02:20 pmBoth types. Tu-155 is a cryogenic fuel flying laboratory based on passanger Tu-154 plane. Cryo fuel storage designed for liquid hydrogen and compatible with LNG.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 27, 2020, 11:50:14 pm
content: Quote from: nctnico on July 27, 2020, 07:30:22 pmIt isn't just price. Lets say that hydrogen fuel costs 10% of fossil hydrocarbons. But the density issues still remain. For my example, is there a market for an airplane that flies low and slow in relatively short flight segments. Even with low ticket prices. The answer isn't obvious to me. It could be there, but it seems equally likely that trains and electric automobiles would be preferred to such an aircraft. Trains and automobiles would also benefit from those low prices if they materialize. Remember that while fossil fuel prices are guaranteed to go up both because of scarcity and loss of subsidies there is no guarantee that hydrogen costs will go down. Maintenance on a hydrogen infrastructure is likely to be costly and remain so.The example solution is an extreme case, but all solutions will have consequences and may result in an un marketable design.

author: SkyMaster
author_rank: Frequent Contributor
timestamp: July 27, 2020, 11:52:18 pm
content: Quote from: DougSpindler on July 27, 2020, 10:47:39 pmIt is probably the latter; with a probability of 100%.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 12:19:01 am
content: Quote from: SkyMaster on July 27, 2020, 11:52:18 pmThat's what I'm thinking. Just some stupid thing some MBA was saying to get investor's minds distracted from the fact airlines aren't doing well and are not buying planes right now.I suspect if it were practical to power planes with hydrogen we would be doing in by now.Other I thought I had was why hydrogen? When it comes to rockets, we use hydrogen peroxide and kerosene not hydrogen. And kerosene is very similar to jet fuel.Wait a second, maybe it's not so dumb after all. Just found this.Hydrogen has an energy density per unit mass that is 3 times higher than traditional jet fuel, but a lower energy density per unit of volume.If hydrogen is available in quantity from low-carbon energy sources such as wind or nuclear, its use in aircraft will produce fewer greenhouse gases (water vapor and a small amount of nitrogen oxide) than current aircraft. Currently very little hydrogen is produced using low-carbon energy sources, and there are several serious obstacles to the use of hydrogen in aircraft and other vehicles. Due to the way it is produced, and the relative inefficiencies of its production given current technology,hydrogen is more expensive than fossil fuels.Liquid hydrogen has about four times the volume for the same amount of energy of kerosene based jet-fuel. In addition, its highly volatile nature precludes storing the fuel in the wings, as with conventional transport aircraft. Therefore, most liquid hydrogen aircraft designs store the fuel in the fuselage, leading to a larger fuselage length and diameter than a conventional kerosene fuelled aircraft. This lowers the performance due to the extra wetted area of the fuselage. The larger fuselage size causes more skin friction drag and wave drag. On the other hand, hydrogen is about one-third of the weight of kerosene jet-fuel for the same amount of energy. This means that for the same range and performance (ignoring the effect of volume), the hydrogen aircraft would have about one-third of the fuel weight. For a Boeing 747-400 type aircraft, this would reduce the takeoff gross weight from 360,000 to 270,000 kg (800,000 to 600,000 lb). Thus, the performance of a hydrogen-fueled aircraft is a trade-off of the larger wetted area and lower fuel weight.Look like this might be feasible. If the fuel has to be stored in the fuselage, then the I guess the passengers would have to be seated in the wings?This might be is in the realm of being possible if Airbus starts working on it soon. It might also be the end of Airbus of the cost of the hydrogen fuel remains higher than jet fuel. Need to check back in 5 years to see how they are doing.

author: coppice
author_rank: Super Contributor
timestamp: July 28, 2020, 12:26:04 am
content: Quote from: DougSpindler on July 27, 2020, 11:02:20 pmThe wikipedia page says the TU-155 flew 100 times, but gives no indication how many flights were with hydrogen, and how many were with LNG. It doesn't say anything about the purpose of this plane. It would be interesting to know that.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 01:00:18 am
content: Quote from: coppice on July 28, 2020, 12:26:04 amIt would. Have you seen the nuclear powered planes the US was working on and the Soviets built and flew?

author: coppice
author_rank: Super Contributor
timestamp: July 28, 2020, 01:11:20 am
content: Quote from: DougSpindler on July 28, 2020, 01:00:18 amOn Youtube you can find some videos on the US nuclear aircraft work, where the people who worked on it actually say they never considered it feasible. It was just a good way to get a budget for their nuclear power research.

author: tom66
author_rank: Super Contributor
timestamp: July 28, 2020, 06:27:30 am
content: Quote from: CatalinaWOW on July 27, 2020, 11:50:14 pmIn a similar sense France is acting to ban domestic flights entirely where the fast train is 2.5 hours or less. Ultra-high speed trains could probably replace a great deal of domestic and short-haul European flights, especially when you consider the security time at the airport.Any such technology needs to ensure that it does not find itself in an obsolete area - it should address what aircraft do really well, which is long distance, high speed flights (>1000km, >3 hours)

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 07:57:32 am
content: Quote from: tom66 on July 28, 2020, 06:27:30 amThis was discussed on Rick Steves Travel forum last summer before COVID. The price for a train train ticket is typically much higher compared to the price of a ticket on one of Europe’s low cost airlines. Price is typically The decisive factor for consumers.

author: coppice
author_rank: Super Contributor
timestamp: July 28, 2020, 10:08:05 am
content: Quote from: DougSpindler on July 28, 2020, 07:57:32 amYep, its mostly down to price. Most airports are in awkward spots for most travellers, who take ages to get to them. When there is a good train network domestic flights generally only make sense as connecting flights to long distance routes...... until you get to the price, and then the train doesn't look so good. You don't even need a great train network, like the TGV in France. Even the crappy trains in the UK make it faster to travel from the typical building in London to the typical building in Manchester, unless those buildings happen to be near the airports.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 28, 2020, 05:31:23 pm
content: The price thing applies for trains and buses in the US. I am not sure why train and bus tickets are so expensive. Don't know if it is driven by real economic costs relative to air travel, or if the subsidies involved are so much different. Plains and buses benefit from publicly supplied infrastructure. Trains got huge public money to start a century ago, but afaik pay all current infrastructure costs. I am sure there are other factors.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 05:55:58 pm
content: Quote from: CatalinaWOW on July 28, 2020, 05:31:23 pmI've been told in Europe the reason train tickets are so expensive is the cost to maintain the trans and the track, the number of people required run the trains and the pensions for all of these employees. Something else to consider is the cost to build a new train route. And hope that once it's built the route will be profitable.Compare that to an airport. All one needs is a open spot of land, pave it over and you have an airport. Unlike trains which can only move along a set path, airplanes can go to any destination. And if they need to go to a new destination they can do that overnight. Something trains can't do. And think how easy it is to add a new destination for planes. No tracks to lay, bridges to build, highways to cross, tunnels to dig, mountains to climb.If we are talking US or Europe there states/countries which do not have a good train network so it's either plane, bus, car or walk.Last summer I was in Croatia traveling to Paris. Taking the train (which is bus and train) Google told me 22 hours. Plane was about 2 hours. Cost of the plane ticket? $35.Would you fly or take the train?

author: coppice
author_rank: Super Contributor
timestamp: July 28, 2020, 06:04:16 pm
content: Quote from: DougSpindler on July 28, 2020, 05:55:58 pmA 2 hour flight is a considerable distance. Trains can't be expected to compete with that on total journey time. Its all those one hour flights where the train is normally faster when the total journey is considered.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 06:40:32 pm
content: Quote from: coppice on July 28, 2020, 06:04:16 pmYeah, but a 2 hour flight for just $35?In the US a 45 min flight is quicker by plane and less expensive. I travel frequently from SF to LA. 45 min flight or 6 hour drive if there's no traffic. (Which is almost never.) They've been talking about building this for year. The train would take 4 hrs which is an hour less than driving and about the same amount of time as flying. Just to cover the construction costs, every man women and child in the state of California would have to make that trip 100 times at a cost of $200 (which is twice that of a plane ticket. And then what happens if there's a major earthquake? And you are on the train traveling 200 mph and the land /track shifts 20 feet?

author: tom66
author_rank: Super Contributor
timestamp: July 28, 2020, 07:36:06 pm
content: It's for this reason that we can't just ban aviation. Even Greta was forced to admit as much when she had to appear at a conference - you can sail across the Atlantic but really is this practical for everyone? Nobody wants to spend two weeks travelling. Sure, we can reduce flying (videoconferencing is one way), but not prohibit it entirely. Not yet.So we need to make aircraft cleaner. Easiest way to do that (doesn't require exceptional new technology) is to change the fuel.Proposal:- State to airlines that by 2030, their aircraft must use a total of 5% certified renewable, carbon neutral fuel; OR they must pay a total of $600/ton of CO2 from the 5% nonrenewable fuel- And by 2035, that must be 25%; and remove the carbon offsetting option- And by 2040, that must be 50%- And by 2050, that must be 100%All options permit entirely new technologies, like hydrogen or electric aircraft if somehow they become practical. The "certified" aspect should eliminate the possibility of massive sugarcane fields being used to produce fuels.You've created an immediate economic incentive to supply renewable fuels, provided a roadmap for it to be integrated into the supply chain ... and then you just sit back and watch the fuel companies compete to meet the need.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 07:45:26 pm
content: Quote from: tom66 on July 28, 2020, 07:36:06 pmYou can sayProposal:- State to airlines that by 2030, their aircraft must use a total of 5% certified renewable, carbon neutral fuel; OR they must pay a total of $600/ton of CO2 from the 5% nonrenewable fuel- And by 2035, that must be 25%; and remove the carbon offsetting option- And by 2040, that must be 50%- And by 2050, that must be 100%Put haow are you going to do it? And what are they going to do with the jet fuel is we don't use it? In the past gasoline was considered a waste product and just dumped into rivers and oceans before the internal combustion engine was created.

author: richard.cs
author_rank: Super Contributor
timestamp: July 28, 2020, 07:50:15 pm
content: Quote from: DougSpindler on July 28, 2020, 07:45:26 pmWith modern refineries turning it into any other useful hydrocarbon is no big deal. We've gone way beyond simply separating out the fractions and ending up with products in the ratio they exist in the crude. As such a reduced demand for jet fuel would simply mean a reduced demand for crude in general.

author: coppice
author_rank: Super Contributor
timestamp: July 28, 2020, 07:50:45 pm
content: Quote from: DougSpindler on July 28, 2020, 06:40:32 pmThis is BS. You are comparing a door to door car journey with just the flight segment of an alternative journey. Talk about door to door in both cases if you want it to be meaningful. Time was when you could turn up a few minutes before a flight for domestic flights in the US. In the 2010s I've waited 2 hours to get through the TSA checks, and finally had to be escorted through before I missed my plane.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 08:02:55 pm
content: Quote from: coppice on July 28, 2020, 07:50:45 pmFlight time is 45 mins. Door to door time is just under 3 hours. Typically 2:45 from the time I leave my house in the morning, to the time I'm at my destination in Santa Monica. This can be faster (pre-covid) than it would take me to get from SF to San Jose, door to door.

author: tom66
author_rank: Super Contributor
timestamp: July 28, 2020, 08:05:07 pm
content: Quote from: DougSpindler on July 28, 2020, 07:45:26 pmWell, as stated earlier, the reason algae biofuels stalled is because they are unlikely to ever be cost competitive with $50/bbl or less oil. Algae biofuels are probably competitive when at around the $200/bbl point. As more money goes into the field the price will fall like most technologies.Fuel is a small part of the cost of running an aircraft, but it's still a significant fraction, so airlines will of course select the cheapest fuel they can get. What you're saying here is, with a proposal like this, you need to buy more expensive fuel now. Maybe flights will get $5 more expensive. But the reality is the price won't rise that much.There are other methods, like solar reformed hydrocarbons, which produce small amounts of fuel right now, but you would flood this field with investment if you provided guaranteed demand in a decade.Airlines generally purchase their fuel years in advance on long options contracts, so you need to give enough notice.

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 08:07:33 pm
content: Quote from: tom66 on July 28, 2020, 08:05:07 pmAirbus is saying 10 years.

author: tom66
author_rank: Super Contributor
timestamp: July 28, 2020, 08:09:14 pm
content: Quote from: DougSpindler on July 28, 2020, 08:07:33 pmGreat. So if they think it'll be 10 years then setting a requirement of "you absolutely MUST have 25% of your fuel produced carbon neutral within 15 years" is quite reasonable. Surely they wouldn't be lying just to continue to delay the inevitable.

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2020, 08:46:21 pm
content: Quote from: DougSpindler on July 27, 2020, 10:42:52 pmHint: where is your extra oxygen coming from? How does producing & consuming H2 produce oxygen?

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: July 28, 2020, 08:49:52 pm
content: Quote from: tom66 on July 28, 2020, 07:36:06 pmI hope you realize that where you say "they must pay" it really means "you're going to pay", yes?

author: DougSpindler
author_rank: Super Contributor
timestamp: July 28, 2020, 08:58:51 pm
content: Quote from: nctnico on July 28, 2020, 08:46:21 pmSilly - Did you not take a basic chemistry class? These are two different equations which occur at two different times. If they occur simultaneously there would be a huge explosion.

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2020, 09:00:41 pm
content: Again: where does the oxygen come from? Just for once answer a question instead of beating around the bush.

author: tom66
author_rank: Super Contributor
timestamp: July 28, 2020, 09:09:13 pm
content: Quote from: GeorgeOfTheJungle on July 28, 2020, 08:49:52 pmOf course. But a good airline will realise it can get more customers by being cheaper than others, by taking advantage of biofuel technology.I've long been of the belief that while capitalism got us into this mess - it can damn well get us out of it too.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 28, 2020, 11:16:48 pm
content: Perhaps the answer is just let the airplanes go on using hydrocarbon fuel. I've seen reports that air travel is only a tiny fraction of total CO2 emissions (5 to 7 percent in the ones I read). And that the tremendous reductions in air travel as a result in COVID aren't source of the reduced emissions observed. That the reason for those reduced emissions is because of all of the industries shut down and the reduced road vehicle traffic.Of course who knows the truth about air travel contribution global warming. Reports are a dime a dozen. And some very interesting effects were noticed post 9-11 when air travel in the US literally stopped for a few days.

author: tom66
author_rank: Super Contributor
timestamp: July 29, 2020, 07:29:43 am
content: One of the problems with aircraft is because the emissions are mostly at higher altitudes, you lose the carbon sink of the ocean. So while they may only be 5-7% of actual emissions their effect is roughly doubled.