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edmund_the_destroyer wrote

I think your criticism of the von Kármán calculation is fair.

On the other hand, I suspect even if you calculate the cost of laying rail for trains, freight trains are still the most energy efficient cargo system we have this side of sailing ships.

This article states that a modern airship uses 80% less fuel than a modern cargo plane. I tried to find stats for cargo planes and got this: on page 7 the most energy efficient cargo carrier had payload fuel energy efficiency of 146 in units of kgkm/MJ. So our hypothetical airship might reach 730 kgkm/MJ.

Another measurement I've heard, in US units, is that friction on rail is so low that one gallon of diesel fuel will transport one US ton of freight 400 miles. So that's 2000 pounds/2.2 pounds per kg * 400 miles * 1.6093 miles/km / 136 MJ in a gallon of diesel fuel =~ 4300 kg*km/MJ.

I could have my numbers wrong, please check. But if I'm right, rail is so far ahead of airships that if you spread out the cost of building the rail over the life of the railroad then rail still comes head. And that's true even if you consider that rail is inherently at a disadvantage because it can't travel directly from origin to destination as the crow flies. A 30% or 50% efficiency loss due to circuitous routes still puts it ahead of airships.


indi wrote

There are other costs that rail has that air doesn't, such as the environmental impact of running rail through long stretches of green space (something inevitable in Canada, for example).

But I generally think you're correct. For overland transport, yes, rail is probably the best way to go.


edmund_the_destroyer wrote

As far as running rail through green space, I think that brings up discussions of making infrastructure as environmentally friendly as is practical vs advocating primitivism or something along those lines.

Maybe if I had a more abstract perspective on the situation I would advocate the latter view. But I have an enormous extended family that I love dearly, and I can't see any policy that calls for mass dismantling of infrastructure objectively. I imagine it would require the death of huge portions of the population - which may well happen anyway with what humanity is doing, but I can't bring myself to advocate fixing the problem by proactive mass murder.