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.