Airbus Zero Emissions Concept
 

Airbus unveils their Zeroemission Aircraft Concept.

https://www.airbus.com/newsroom/pres...-aircraft.html


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The path between computer rendition and tarmac is very long.

"Support from governments will be key..." Which government has any money left?

What are the big picture challenges with using Hydrogen specifically within the airframe?

I'm assuming storage volume, insulation, leak proofing are big ones before you even get to a power plant? Are we talking pressurised gas or cryogenics?

Are they planning to burn it in a gas turbine or some kind of fuel cell and electric propulsion?

The whole area is fascinating but a lot of basic hurdles to overcome along the way.

That turbofan looks very nose heavy.

Bit of both - combusting it for propulsion, fuel cells to power electric consumers in the aircraft.

You'll note the rearmost passenger doors are placed quite well forward, indicating the aft pressure bulkhead is also quite a bit further up than we're used to in today's designs.
With the hydrogen storage systems being placed aft of the bulkhead, you need quite a bit of fuselage forward of the wing to balance things out again.

If you look at the mid range jet design, the wings also seen placed pretty far backwards - same reasons as you have significant weight sitting in the back

But whenever the hydrogen is spent and the tank empty don't you end up with a steep descent? Green MCAS so to say.

We can only hope that today Airbus FMA (failure mode analysis) is up to expectations ...

Would the weight of burnt H2 be an issue? Present designs are well tolerant for using up the fossil load. Quite significant sometimes.

My assumption is containers for liquified gas introduce the new angle, but those would stay for the full duration of the flight.

H2 has 3 times the energy density of fossil fuels PER KILO. So ideally, the fuel mass should only be a third for the same stored energy, ignoring all other factors (storage, efficiency ...)

......(storage, efficiency....) and pressure and cryogenics. A transportable load of 3500 kg (equivalent to ca 10000 kg kerosine) would require 200 bar. A flying bomb in my humble opinion.

Engines, passenger cabin, cargo and cockpit/avionics and some long fuselage section look like being deliberately placed ahead of the center of gravity while the tail looks very short. What heavy stuff is hidden inside the tail section if it's not the fuel itself? The pressure tanks? The insulation? Fuel cell? It must be quite heavy.

But the volume is significantly higher, so trading off some of that gain against increase sized tanks, larger structures, more drag &c. I find the whole thing absolutely fascinating and if 2050 really is the target look forward to flying some of these things before I retire.

What sort of issues are hiding in there? Is fuel gauging with cryogenics (if that’s the route they take) much harder? I almost wish I were clever enough/made the right career choices to be involved in development.

I am wondering why existing models couldn't be modified to run on hydrogen ? Obviously, new engines would be needed, and fuel tanks would need to be pressurized and able to withstand that pressure, but ?

Google 'roland berger Hydrogen: A future fuel for aviation?' , it's short and a good starter to the topic.

The target is 2035, 15 years from now. Given the timescales in aviation and the problems to solve : tomorrow. (as Airbus said in their presentation)

Thanks fruitflyer for posting a link to the article. To be clear, my question had to do with the usage of hydrogen combustion, not fuel cells.

The main problem seems to be that storing enough hydrogen in a practical manner in liquid form requires cooling, down to -253 deg Celcius, and just the cooling may consume up to 45% of the fuel itself.

Its been suggested that the oil companies are keen on hydrogen (you separate the it from the carbon in oil) but realistically it will come from electrolysis. The trouble is that we don't have enough renewable fuel for the existing grid and would need far more for electric cars and huge electrolysis plants. That's a lot of wind farms and photoelectric cells. Its interesting that going back to my childhood (half a century ago) the future was nuclear power, the power being used to create hydrogen which would be burnt in aircraft. Back then the problem was seen as lack of oil and no one had thought of global warming, but it was still felt that new sources of energy would be required. We know that technology advances, the question is how fast and crucially in which areas. Look at an episode of Thunderbirds (mid 60s). The (actually very perceptive) writers missed the rise in computers, algorithms, internet, mobile telephony for all (nor just a few selected International Rescue agents), etc but seemed to think that we would have rather more nuclear powered devices masses of supersonic commercial aircraft and so on. If we look back to today in thirty or fifty years how accurate will our predictions to the future look?

Its amazing how much technology come about because of the space race in the 60s. The Saturn V used cryogenic storage - for a few hours, it couldn't be used later in the mission and if launches were delayed the fuel was allowed to bubble off, rather wastefully - but maybe it was assumed that cryogenic storage would advance. If we announced the equivilant to the Apollo programme for sustainable fuels where would we get?

My view is that the future is biofuel derived from algae (seaweed) which will cost a lot more than jet fuel does today but partially offset by more efficient aircraft making aviation affordable. Oil refineries may disappear to be replaced by large algae processing plants, but the actual fuel distribution network will be similar to today's. I may of course be wrong as to which technology works which is why I fully support the development of hydrogen and electric powered aircraft - and any other promising new technology that comes along. Lets hope that one of them achieves a breakthrough.

I read somewhere -forgot where- that the 4th Chinese aircraft carrier will be propelled by a molten salt thorium reactor. This will lead to 1000 (?) times less nuclear waste, and operates at temperatures of around 800 Celsius. It seems that even the Americans do not have such a capability. Is this the answer to producing cheap hydrogen in large quantities, in view of the high temparsature needed to break down the water molecule?
But even then the pressure and cryogenics problems still exist.

Well, the USA were happily helping them with the technology back in 2013...

https://www.reuters.com/article/us-b...9BJ0RH20131220

They are known to have been building 2 test reactors in the Gobi desert since 2017, supposed to be ready by 2020...

https://www.nextbigfuture.com/2017/1...ng-drones.html

And producing hydrogen is a possibility from a nuclear reactor.

Thanks Derfred, for a very interesting article. It seems, that the Chinese see an advantage in the use of thorium reactors. I wouldn't be surprised, if they also see a strategic advantage in using this technology for controlling large scale commodities, as they are now doing with African mines of kobalt etc. Hydrogen could well be such a strategic commodity in the future, maybe not for aircraft per se, but for all other applications on the ground.
Beware, I would say.

Back in the '80s, a pair of HTGCRs (High Temperature Gas-Cooled Reactors) were proposed in the US (Arizona, IIRC). They were also based on the Thorium cycle. Advantages included inherent safety - they shut down when they lost coolant gas (I don't recall what gas was used, but likely Helium). They were never built, probably as a result of the 3-Mile Island mishap.

https://www.alternative-energies.net...actors-energy/

Iirc, the HTGCRs turned out to be very troublesome to make, partly because high temperature helium is difficult to confine. The plant was transformed into a fossil fuel powered site. I believe that General Atomic, the construction manager, went out of the reactor business as a result.
That said, there is no question that nuclear power could blend happily with the hydrogen economy, as the inefficiency of hydrogen electrolysis is no problem for a reactor where fuel costs are minute relative to the capital cost. The reactor can generate electricity or hydrogen as required, bur runs 24/7, unlike solar panels or wind turbines. A cheap and reliable reactor is what is needed, not another frail technological miracle.

The problem with high temperature helium is, that it can diffuse thtrough steel piping, and is therefore difficult to contain.

From my reading, it seems that the USA’s reluctance to pursue the Thorium cycle had more to do with their economic confidence in their heavily researched Uranium cycle than anything else.

It’s all very well explained in this wiki article: https://en.m.wikipedia.org/wiki/Thor..._nuclear_power

To keep on thread though, hydrogen in this respect is not a power source, it is a storage medium.

Fossil fuels, such as Jet A1, are a power source, because they are not generated, they are sucked up from the Earth’s crust, refined, and then oxidised to produce power.

Nuclear powered hydrogen electrolysis is of course different. The nuclear reactor is the power source, the hydrogen is merely the storage medium.

A very difficult storage medium, mind you, requiring either extreme pressure or extremely low temperature to store.

Other techniques have been proposed to carry the hydrogen “energy”. The hydrogen can be combined with carbon to make methane. Or carbon and oxygen to create methanol. Possibly the most promising suggestion is to combine it with nitrogen to create ammonia.

The ammonia solution seems favourable for deep sea shipping.

But the minute you combine the hydrogen with anything else like carbon, oxygen or nitrogen, you’ve immediately lost the energy-weight advantage of hydrogen! So you might as well use some form of bio-fuel.

I don’t think anyone, including Airbus, has come up with anything anywhere near viable for carrying hydrogen as a source of power on an aircraft.

To store raw hydrogen at room temp, you would need around 3000 psi. That is the pressure of aircraft hydraulic systems. Try to upscale that to tens of thousands of litres and apply safety measures.

The other option is cryogenic storage near zero Kelvin. Try to put that on an aircraft with safety measures.

The pub test says no.