[jonititan]

I'm actually on a project looking at this and it's not so rosy. My area is trying to predict maintenance costs for the hydrogen PEM fuel cells. The cells get contaminated pretty fast.

Regarding hydrogen suitability while it has excellent gravimetric efficiency it has terrible volumetric efficiency. You either need huge tanks and high pressure or cryogenic tanks to store it in its liquid phase.

Like anything else its doable we just need to accept higher airliner prices and slower speeds/shorter ranges.

[credit_guy]

> You either need huge tanks and high pressure or cryogenic tanks

According to Airbus all 3 demonstrator planes will have liquid hydrogen [1].

As for the fuel cells, they will basically not be used.

The engines will be regular engines that burn hydrogen instead of jet fuel. Fuel cells will only be used for the electricity needs of the airplane, but not for moving the airplane through the air. They are probably going to use less than 1% of the liquid hydrogen.

[1] https://www.airbus.com/en/innovation/zero-emission/hydrogen/...

[janef0421]

That gets to the point I was trying to make. Aviation initially became popular because it had advantage in cost, speed, and range. If climate change adaptation means aviation loses all or most of those advantages, then it would be logical to transition to other forms of transport, like rail, which have other advantages, such as capacity and comfort.

[R0b0t1]

There are iirc substances like graphite(?) sponge that will take in more H2 at a given pressure. It's still high, but it's better. The tanks can be made long and thin and stacked. Is the extra tank material too much in either cost or mass?

[jonititan]

I haven't looked at the various sponge or chemical binding concepts personally. To be used in an aircraft to be delivered say in 10 years time they would already need to have been approved by EASA or FAA or have a clear and straightforward approval pathway. Otherwise they represent a large schedule risk and new airliner types cost several billion to launch so they are pretty risk averse.

That's not to say those concepts won't work. Regarding long thin tanks wings don't actually have that much suitable internal volume for that. Lots of ribs, stringers, etc. That's why most hydrogen aircraft concepts use under wing pods or fuselage tanks to store the hydrogen even though it reduces safety margin. Civil aircraft regulators are allergic to storing fuel in the fuselage near the passengers for good reason.

[R0b0t1]

The containers for the hydrogen can be made to vent safely for a lot of impacts. Fiberglass, carbon fiber, or other composites.