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Comment by dekhn | Hacker News Reader

The efficiency argument doesn't work: moving up against gravity will always be more expensive.

There are always tradeoffs... airplanes move more or less at a steady speed, and are much more aerodynamic than cars, which spent quite a bit of time stuck in traffic. Thus in many cases planes are more efficient than cars (despite needing to lift).

Airplanes have to go faster than the stall speed. Stall speed is typically ~60mph or more, and air resistance goes up as the square of the speed (times the aerodynamc cross section). Airplanes aren't really that much more aerodynamic than modern cars.

Not necessarily. If a car is twice as efficient, but has to travel three times as far because of the windy road system, the flying car will have it beat in a straight line.

> travel three times as far because of the windy road system,

Ironic choice of words. The winding road system adds distance to your commute, but a windy airspace adds air-miles to your commute.

That is, a flying car doesn't travel through the same amount of air when going 1 ground mile in different directions.

Haha, completely unintentional. Very good point though.

Personally I don't think flying cars will take off (ha, done it again...) for quite some time, if only for risk reasons. Think about just how many car accidents there are every day, now imagine every accident ending with a 100m death plunge from the sky. I just can't see it going mainstream for a long time.

I think you'll need to adjust that from "three times", to "90 times" for the physics and math to work.

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