Hacker News Reader

Comment by colin_mccabe | Hacker News Reader

Airplanes are not "insanely efficient" when it comes to greenhouse gasses. A plane emits roughly the same amount of greenhouse gasses per mile per person as a car. Maybe 50% if we assume an efficient plane and an inefficient car. And the number of miles travelled by plane is typically much more. Even one round trip flight from SF to europe is 10,000 miles, which is comparable to a year's worth of driving for one person.

View on HN

> roughly the same amount of greenhouse gasses per mile per person as a car

I see. How much non-human cargo are these cars carrying? More to the point: how else do you propose one go from SF to Europe?

Reading between the lines, you're either suggesting people stay home or that they take a boat, both of which are absolute crazy talk.

EDIT: moreover, wikipedia's numbers suggest jetliners get roughly 70 to 110 passenger-miles/gallon (https://en.wikipedia.org/wiki/Energy_efficiency_in_transport...). I have yet to come across a car that gets that kind of mileage period, let alone per passenger.

Besides, gas turbine engines are pretty much the model of efficiency when it comes to hydrocarbon-consuming engines. I don't know where you people are getting your numbers but my BS detector is off the charts.

I don't think that turbine engines are the model of efficiency that you claim. On a BSFC basis, they're significantly worse than piston diesels or marine two-strokes. https://en.wikipedia.org/wiki/Brake_specific_fuel_consumptio...

(That's for shaft engines, which a turbojet isn't, but the turboprop examples are jet engines with a gearbox and propellor mounted.) Jet engines are incredibly powerful (per unit of mass) and reliable, but I don't think they're incredibly efficient.

Perhaps I don't understand the measure (entirely possible!) but I think thrust-specific fuel consumption is a better indicator here. You need to account for the thrust required in these behemoths: replace the gas turbine engines with piston engines large enough to produce equivalent thrust and I doubt you'll retain the fuel economy.

Either way, this is an auxiliary point: the per-passenger fuel economy of airplanes is significantly higher than that of cars.

What's a more efficient way of getting from San Francisco to LHR? Via ship, the long way?

> What's a more efficient way

Staying in California.

Reply on news.ycombinator.com