> 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. This trade-off depends essentially on the size of the aircraft. [1]

[1] https://en.wikipedia.org/wiki/Hydrogen-powered_aircraft#Prop...

From what I understand a considerable amount of the weight savings for H2 is lost when you add in the mass of the fuel tanks and piping.

The other problem is that the reduction in wing area needed (due to lower weight) is offset by the increase in drag of the fuselage so the savings are modest if they even materialize.

The problem with biofuels in aviation is that the most common available forms have... problems with storage and weight of the system. Because ethanol evaporates too fast, which is the same reason why aviation still uses leaded gasoline, and why ethanol additives are very limited.

Remember, aviation fuels need to work way above 10km above sea level.

I'd assume ethanol would be converted to something like kerosene, since that's what jet engines burn anyways. But without regulation I don't see the incentive to use biofuels. They're significantly more expensive and don't offer any performance benefits. Hydrogen has the same problems btw.

One gigantic advantage for synfuel kerosene that is carbon-neutral because it is produced with renewable energy, is you can continue to use the present airliner fleet. With hydrogen you have to spend many trillions of dollars replacing it.

Furthermore, replacing all the planes would take many decades, while synfuel kerosene might go into production much sooner.

Do the hydrogen airliner boosters take all that into account?

> Do the hydrogen airliner boosters take all that into account?

Sure, and other things too, like combustion benefits and hazards. But regarding your money worries - they don't need to happen overnight, just like electric cars don't replace gasoline ones suddenly.

Hydrogen fundamentally more potent fuel than kerosene - both by energy density and heat characteristics. Like with other commercial technologies, to be accepted it has to change traditions somewhat, which isn't easy. Safety is another important matter - it remains to be seen if hydrogen can be safely brought onboard to regular commercial liners, though advancements demonstrated by Toyota Mirai remind that progress doesn't stand still.

It may well be that hydrogen is the fuel of the future for airlines. The problem is that with the rate global climate change is happening, we can't wait decades for a solution. We need something as soon as possible, and as far as I can tell, synfuel kerosene could replace fossil fuel kerosene decades sooner than hydrogen could. Do the hydrogen boosters address this concern?

carbon-neutral Jet A1 would be very nice, but so far the only case of it being used is the newest USN supercarrier, which can throw efficiency to the trash and has immense amounts of "extra power" from reactors that it can throw at it.

I wouldn't mind a future where we use syntin-based fuels or similar for aviation and push for max renewables and nuclear for power elsewhere.

> Because ethanol evaporates too fast, which is the same reason why aviation still uses leaded gasoline

Not really. Most of commerical aviation doesn't use leaded fuel anymore, and general aviation uses leaded gasoline because it is technologically still mostly stuck in the sixties.

Most commercial aviation doesn't use leaded fuel because it uses Jet-A1 instead of AVGAS 100LL.

Replacements for currently used anti-knocking agents are searched for, but less so specifically because most commercial use involves Jet-A1, and low-end general aviation uses MOGAS where possible due to general lower prices (though those tend to vary - sometimes AVGAS 100LL can be wildly cheaper than MOGAS)

Avgas is leaded because it is used as an octane booster and an anti-wear coating for valve seats.

Replacements for tetraethyllead have unfortunate negative effects fuel evaporation and general characteristics in lower pressure / higher temperature environment.

This seems like an easier problem to solve than converting to H2.

Yes, I'm curious to know how much of a weight penalty H2 incurs in required heavy pressure vessels, compared to typical liquids?

Only gaseous hydrogen is stored in heavy tanks under high pressure.

As explained in the article, gaseous hydrogen has been deemed infeasible for aviation and the idea is to use liquid hydrogen. No high pressure involved.

Well, liquid hydrogen requires some pretty heavy insulating/cooling equipment, doesn't it?

The insulation would likely be some type of spray-on foam over aluminum tanks, so not a lot of weight penalty there.

Cooling likely wouldn't be done, I assume any excess hydrogen boil-off that couldn't be burned immediately would be allowed to escape through an overpressure vent. (So ideally top it up right before taking off. There could still be a problem if the plane needs to queue a very long time for a congested runway.)