Held aloft by hydrogen

The Economist ^ | September 15, 2005 | Economist Staff

[Zuben Elgenubi]

Unmanned hydrogen-powered aircraft in our future.

[Zuben Elgenubi]

ping

[GSlob]

While liquid hydrogen as a fuel might have three times the energy content of hydrocarbon fuels per unit of weight, its density is one tenth of the hydrocarbons (0.07 vs. 0.7g/ml) - i.e. the energy content per unit of volume is 30% that of hydrocarbon fuels. Add to it bulky cryogenic storage tanks - and the spatial requirements of liquid hydrogen as a fuel become problematic, unless the amounts used are very large, like in space shuttle.

[My2Cents]

[MikefromOhio]

LOL

[wolicy_ponk]

[supercat]

Add to it bulky cryogenic storage tanks - and the spatial requirements of liquid hydrogen as a fuel become problematic, unless the amounts used are very large, like in space shuttle.

If an aircraft were not fueled until immediately before deployment, could not the vaporisation of fuel as it is removed from the tank be used to keep the rest of it cool?

[Mr. Jazzy]

You are soooooooo bad!!!




But, I must give "props" to the manatee.



hehehe

[tbeatty]

I like Hydrogen as a fuel. You combine it with other Hydrogen atoms to make Helium.

Oh wait. the greenies don't like that method.

[GSlob]

Theoretically yes - but hydrogen heat of vaporization is not high, and its boiling temperature is very low (i.e. you have large heat gradient from outside air and large heat flows) - which means that you will still need to drastically curtail heat flow into your liquid hydrogen tank, or the natural evaporation will keep it cold during the few minutes it will take to evaporate dry. If you tank is of gigantic size, then it becomes less important (surface/volume ratio drops; heat flow is through the surface, and you'll have a lot of volume to evaporate). Also, without thermal insulation you will immediately start condensing atmospheric moisture and will be all covered with heavy hoarfrost (now, what was your takeoff weight?).

[Luddite Patent Counsel]

I like Hydrogen as a fuel. You combine it with other Hydrogen atoms to make Helium. Oh wait. the greenies don't like that method.

Can you blame them? It makes their voices sound like Munchkins.

[wizr]

OH, the humanity!!!!!

[tbeatty]

Density and cryo storage are the reasons why fuel cells are more practical. Extracting a hydrogen atoms from alcohol or gasoline is way more practical than compressing Hydrogen into the weight and volume necessary to propel a vehicle.

I haven't looked in a while but I thought peroxide plus hydrazine had a nice energy density as well as no carbon. Only problem is it's toxicity to humans (not really a concern for greenies since it's combustion artifacts are very green).

[tbeatty]

It's a simple question of weight ratios. A 5 oz aluminum bird can't carry a 2 pound hydrogen coconut.

[GSlob]

Well, the solution would be to master artificial gravity - and keep the hydrogen compressed by it to 100g/ml (conditions obtaining in the center of stars and near extreme astronomical objects). The thing would ruin the car finish, though.
As for hydrazine with peroxide - unless you dilute them with water (ballast!), both are explosion hazard. "Kursk".

[anymouse]

LOL! (Cleaning coffee off screen and keyboard.)

[solitas]

LOL! I almost sh_t myself. :D

[BlackbirdSST]

Man that is sick! Mind if I steal a copy? Blackbird.

[MikeD]

Suppose two birds carried the coconut together...