"It’s fundamentally impossible to improve on jet fuel because it would break the laws of physics", pronounced Laughlin. "You can’t have airplanes unless you make hydrocarbon fuel."
If electrical energy was cheap but hydrocarbons were expensive, it would be cost-effective to electrolyze water into hydrogen and oxygen. By mass, hydrogen is the most efficient way to store chemical energy. By volume, it's not so efficient, and currently storage is difficult. Still, 200 years from now I think materials technology will have advanced a little.
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"It’s fundamentally impossible to improve on jet fuel because it would break the laws of physics", pronounced Laughlin. "You can’t have airplanes unless you make hydrocarbon fuel."
If electrical energy was cheap but hydrocarbons were expensive, it would be cost-effective to electrolyze water into hydrogen and oxygen. By mass, hydrogen is the most efficient way to store chemical energy. By volume, it's not so efficient, and currently storage is difficult. Still, 200 years from now I think materials technology will have advanced a little.
Another option is nuclear-powered aircraft. (http://en.wikipedia.org/wiki/Nuclear_aircraft)
Yet another pie-in-the-sky option would be to beam power to the airplane (either from satellites or ground stations).
I'm no physicist, but I think I just listed three ways airplanes can exist without hydrocarbons.
And for about $200 a barrel, you can use nuclear power to make that same hydrocarbon fuel out of thin air.
None of those options seem particularly viable, even given advanced technology:
* Nuclear has trouble with radiation shielding - not good for passenger planes unless you make enormous planes with a couple of thousand passengers.
* Beaming power is going to cook birds along the route
* If you're going to the trouble of making hydrogen, which is notoriously hard to store, you might as well just make jet fuel instead.
You can run jet engines on ethanol, too. It's slightly less efficient by volume than kerosene, but surely it beats hydrogen.
Ethanol is basically a hydrocarbon anyway.
Here's a fourth : Blimps.
Blimps are slow. Also blimps are not planes.