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Flying cars will always be less efficient (and thus, more expensive) than driving cars due to the physics of it. I wouldn't hold my breath on flying cars replac

Flying cars will always be less efficient (and thus, more expensive) than driving cars due to the physics of it. I wouldn't hold my breath on flying cars replacing driving cars, just as airplanes haven't replaced trains.

vidarh 8y ago
> Flying cars will always be less efficient (and thus, more expensive) than driving cars due to the physics of it. As it stands, for cars, the typical energy use is 3k-4k BTU per passenger mile. Commercial airliners use 2k-3k BTU per passenger mile. Of course those get their efficiency from packing more passengers in. But the point being that a statement like the above only makes sense when comparing comparable vehicles (the bad numbers for cars is in part because cars on average have less than 2 people in them; fill a car up, and it will do better per person than a typical plane). However the best reported numbers I've found from test flights of electric planes is energy use as low as below 1300 BTU per mile (these numbers will also vary wildly by number of people; most prototype models in progress are for 2 people, including Lilium, though their next version will be a five seater). Part of this is due to totally different design constraints. Of the 12 in-progress models I'm aware of, the heaviest is about 1/4th the weight of the lightest Tesla. The lightest is about 1/6th the weight of the lightest Tesla. E.g. the two-person version of the Lilium was 400kg without passengers. Part of this again is that the cost of purchase vs. cost of operation calculations are entirely different: Most of these are designed for the hire operator market or as luxury items, and they're not even possible if they weigh too much, so much more money gets spent on expensive materials to push weight down. Their assumption is that they'll get the operational costs down far enough to amortise the increased finance costs of buying it.
- FabHK 8y ago
  Yes. The Uber Elevare white paper looks at this issue, and the stylised numbers are: Car: 1 mile/kWh Flying car: 2 mile/kWh Electric car: 3 mile/kWh (Electric engines are much more efficient than combustion engines.) So, it’s not too bad, plus ground based vehicles (according to the same study) have to drive on average 1.4 miles for 1 mile distance “as the crow flies”. However, the numbers above are for fixed wing flight, as far as I can tell. Drone-like hovering flight is less efficient. Still, I think that’s not the main problem. Regulation, battery specific energy, ATC are bigger hurdles. https://www.uber.com/elevate.pdf/ https://www.uber.com/elevate.pdf/

vidarh 8y ago

> Flying cars will always be less efficient (and thus, more expensive) than driving cars due to the physics of it. As it stands, for cars, the typical energy use is 3k-4k BTU per passenger mile. Commercial airliners use 2k-3k BTU per passenger mile. Of course those get their efficiency from packing more passengers in. But the point being that a statement like the above only makes sense when comparing comparable vehicles (the bad numbers for cars is in part because cars on average have less than 2 people in them; fill a car up, and it will do better per person than a typical plane). However the best reported numbers I've found from test flights of electric planes is energy use as low as below 1300 BTU per mile (these numbers will also vary wildly by number of people; most prototype models in progress are for 2 people, including Lilium, though their next version will be a five seater). Part of this is due to totally different design constraints. Of the 12 in-progress models I'm aware of, the heaviest is about 1/4th the weight of the lightest Tesla. The lightest is about 1/6th the weight of the lightest Tesla. E.g. the two-person version of the Lilium was 400kg without passengers. Part of this again is that the cost of purchase vs. cost of operation calculations are entirely different: Most of these are designed for the hire operator market or as luxury items, and they're not even possible if they weigh too much, so much more money gets spent on expensive materials to push weight down. Their assumption is that they'll get the operational costs down far enough to amortise the increased finance costs of buying it.

FabHK 8y ago
Yes. The Uber Elevare white paper looks at this issue, and the stylised numbers are: Car: 1 mile/kWh Flying car: 2 mile/kWh Electric car: 3 mile/kWh (Electric engines are much more efficient than combustion engines.) So, it’s not too bad, plus ground based vehicles (according to the same study) have to drive on average 1.4 miles for 1 mile distance “as the crow flies”. However, the numbers above are for fixed wing flight, as far as I can tell. Drone-like hovering flight is less efficient. Still, I think that’s not the main problem. Regulation, battery specific energy, ATC are bigger hurdles. https://www.uber.com/elevate.pdf/ https://www.uber.com/elevate.pdf/