Composite carbon fiber material with resin is not compatible with cryogenic temperatures due to difference in expansion rate and brittleness of the resin at very low temperatures. What have been proven is aluminum and stainless steel as cryogenic storage containers. Of course, aircraft is also made out of aluminum so it is convenient for an aft-mounted tank to also be structural part to hold the tail empennage of the aircraft.

H2 can be made near the solar and wind farms and transported via pipelines to all end users, including airport facilities whereby the green H2 can be liquefied locally, stored locally, to be loaded into aircraft. No problem at all.
Piping will be used to move the LH2 to the engines.

Engines will be used instead of Fuel Cells because there is no real advantage of FC over combustion engines which can significantly gain efficiency from the use of LH2 to cool the intake air, thereby reducing compression work.

There will no more contrail than existing petroleum-fueled engines, due to the vastly increase in payload-to fuel ratio enabled by LH2. The amount of water vapor released from LH2 combustion aircraft will be comparable to existing aircraft.

Roger said:

' Composite carbon fiber material with resin is not compatible with cryogenic temperatures'

Yet if I have understood what they are saying correctly, that is exactly what are being built.

Gryf:

If I understand your reservations correctly, and not only am I entirely untrained in the field but also as my age increases my memory decreases, so I may have forgotten what you have patiently explained previously, your reservations are mainly to do with moving the hydrogen around onto and in the aircraft?

As a complete amateur, my own judgement is necessarily somewhat based on arguments of authority, ie I tend to look for what the big boys are doing.

After that comes whether they are putting their money where their mouths are, and then I look for obvious diversion tactics, such as the remarkable enthusiasm by the oil and gas industries for CO sequestration, sometime in the indefinite future.

So I pay some but limited attention to players like Zero Avia, but the likes of Airbus and Rolls Royce being interested attracts me more. I do like the HT PEMs that Zero Avia is to use, although of course they are way, way short of fully proven.

Boeing are several bolts short of credibility at the moment in what ever their objectives are, other than perhaps to keep flying.

Thanks as always, Gryf.

After the first video I had a look at this follow up one on fuel cell variants of hydrogen aircraft:

https://www.youtube.com/watch?v=aFCaST8hkIs

And was immediately struck by the claim at around 1 minute in that contrails in the fuel cell version would be low or even virtually eliminated.

This was new to me, so I bunged into google advanced search:
' fuel cell planes eliminate contrails'

And got a number of interesting hits.

I don't want this post to be autokilled as spam, so I will split this post giving additional links in another post.

Here is a link discussing what Airbus are doing to reduce contrails in all hydrogen powered aircraft, not just fuel cell ones:

https://www.mdpi.com/2226-4310/10/8/688

The bottom line is that they are redesigning the wings and fuselage.

They distinguish between all contrails and the persistent ones which are the ones which do the damage,

The optimum altitude to avoid contrails is very different for polar and lower latitude flight,

Their configuration looks at ranges of 2800km for the version they intend,

' Overall energy use and contrail persistence probability for the A320 and H320 are shown in Figure 14. The lighter weight of the hydrogen aircraft, as discussed in the previous section, increases the altitude required for a given lift coefficient by about 2 km, which enables operation with reduced contrail persistence. At this typical latitude, an H320 operating at a 13.5 km altitude leads to a very low ISSR frequency of about 1%, with about 15% higher energy use per passenger-km than the A320. Flying even higher would achieve a greater reduction in contrails, with negligible contrail persistence above altitudes of about 14 km in non-equatorial latitudes. Notably, the A320’s average ISSR frequency may also be reduced to about 3% by operating at 12.5 km, near its maximum altitude (assuming the A320 is not above 45% fuel capacity, as this would be above the maximum operating altitude of a fully loaded A320).'

So substantial reduction in harmful contrails can be achieved, albeit at some cost in fuel

At the end of 2023 Airbus sucessfully tested their 1.2MW fuel cell stack:

https://www.airbus.com/en/newsroom/stories/2024-01-first-zeroe-engine-fuel-cell-successfully-powers-on

Lots of hurdles to clear yet, of course, but so far everything has been on schedule etc with no nasty 'gotchas' appearing.

I have not managed to track the performance specs of the fuel cell down, but I have come across more info on how Airbus intends to move forward:

https://www.flightglobal.com/airframers/airbus-will-be-ready-to-develop-hydrogen-powered-aircraft-by-2035-goal-ceo/154962.article

' “The bottlenecks are no longer in the technology of the plane,” Airbus chief executive Guillaume Faury said on 12 September during an aerospace event in Washington DC. “We strongly believe that we will be ready by 2035 with a hydrogen plane. The technology will be ready.”

Airbus in 2020 revealed three hydrogen-powered aircraft concepts as part of its ZEROe programme, and said it aimed to bring one to market by 2035.'

That's a pretty strong claim about the technology,

And:

' Executives stress that, optimism aside, Airbus has not committed to developing a hydrogen-powered passenger airliner, saying the decision depends on factors partly or largely outside the company’s control.

Those include unclear regulatory and certification standards, the need for hydrogen transportation and storage infrastructure, and the availability – at the “right price” – of green hydrogen produced using renewable electricity: “That’s going to be where the challenge lies,” Faury says.

Knittel says any initial hydrogen-powered aircraft would likely be on the “smaller” side, and that “long range” is among the toughest “challenges” associated with hydrogen propulsion.'

My betting is that IF hydrogen gets the go-ahead, it will be in a configuration where fuel cells power the APU, with hydrogen combustion which can manage more range etc as the propulsive unit