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Why Elon Musk Doesn't Like Flying Cars (yahoo.com)
boley1 quotes Business Insider:
According to Elon Musk, the main challenges with flying cars are that they'll be noisy and generate lots of wind because of the downward force required to keep them in the air. Plus, there's an anxiety factor. "Let's just say if something is flying over your head...that is not an anxiety-reducing situation," he said. "You don't think to yourself 'Well, I feel better about today. You're thinking 'Is it going to come off and guillotine me as it comes flying past?'"
If flying cars are available the defenses will be useless.
They already are, if that's what you mean by useless. It's already possible to practice flying in simulation, then get some manuals and learn how to actually start up a plane, then stroll onto an airfield someplace and steal one since so many of them have basically no security.
You won't be allowed to control a flying taxi manually, and they will be totally dependent on their computers to fly so you're not going to be trivially overriding them from inside the cockpit.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Most airplanes are circumscribed to landing and taking off in special areas called airports and their use is highly regulated. That diminishes somewhat the worries people have of seeing their neighbors (who they've seen driving into trees and parked cars) attempting to master flight.
Democracy is a sheep and two wolves deciding what to have for lunch. Freedom is a well armed sheep contesting the issue
He does have a point in that anything owned and operated by the general public tends to be maintained to a lower standard than anything owned and operated in an industry which has rigorous maintenance standards and penalties for not following them, such as the airline industry...
Even with private aircraft and pilots, the pre-flight walk rounds can take more time than the flight - precisely because it is necessary to ensure some level of safety.
That is what terrifies me about the flying car concept - all the ideas are around private ownership and operation. Knowing that some people in the UK are more than willing to not maintain their cars to the level of passing a £35 governmental standard test (the MOT, once a year) and instead drive potentially unsafe cars around illegally, I don't want that situation when those cars take to the air...
I am a major skeptic about the whole flying-car idea. For many reasons, but not the same reasons as Musk.
Here, I am disagreeing with one of Musk's points out of technical nit-pickery, but I DO agree with his overall conclusion that flying cars are not the right answer to personal transportation.
I agree they will be noisy. That will never be fully solved. (And expensive and unsafe, but that's off topic.)
But, Musk's wind objection -- I just don't buy it.
Yes, aircraft generate lift by displacing air downwards. Some inclined plane (either the wings, or the rotor blades) deflects air downwards, creating an equal and opposite force upwards. So yes, all flying machines "create downward wind". Some do it highly efficiently (at optimum cruising speed, a typical fixed-wing plane or even to a lesser extent a helicopter). Some do it a little less efficiently (a fixed wing plane at very low airspeed), and some do it horribly inefficiently (a helicopter or drone hovering).
The efficiency is largely a function of the craft's forward speed through the air, for a very basic Newtonian reason. F = ma.
The upward FORCE (which must counterbalance the aircraft's weight) must be matched by downwards ACCELERATION of some MASS of air. Acceleration is not velocity, it is rate of change of velocity. Therefore, lift comes from the act of imparting new or increased downward velocity on some mass of air. Absolute velocity doesn't help, only increase in velocity. Hold that thought, we'll get back to it.
An aircraft moving forward horizontally encounters a steady supply of new air that does not yet have any vertical velocity. OTOH, once an aircraft that is hovering, has imparted downward velocity on a column of air, it remains within that accelerated column as it tries to accelerate more mass downwards. The established downward velocity of the air doesn't help, only the acceleration (increase) in downward velocity of some part of that air. To solidify this concept, think of "swimming up a waterfall".
Hopefully this illustrates why hovering is highly inefficient, and cruising is much more efficient.
Enter simple economics. Any economically VIABLE system of flying vehicles spends the minimum time hovering and the maximum time cruising. This is the reason helicopters are used only for specialized tasks or by rich people, while fixed wing planes are used for general transportation. While I don't personally believe that flying cars will take off (bad pun semi-intended), if they do, simple economics dictate that they won't spend much time milling around close to their terminals hovering. They will rapidly get a move on along their course. Once they are moving en-route, their "downward wind" is over such a dispersed area that is is essentially immeasurable.
I don't know what exact means they'll use to transition from takeoff to cruise -- rotors, fixed wings, adjustable wings, whatever -- but they won't be concentrating their "downward wind" in one small place for very long. If one's vision of personal air transportation involves any significant time hovering close to the terminal, then economics dictate that it won't succeed. And downward wind during cruise is simply not a problem.
There will be some localized wind right at the terminals, but if you've ever stood nearby when a helicopter takes off, you know that it is windy very strong but very localized, and does not persist long after the helicopter moves away.
The tunnel is actually plausible. Tunnel boring can be done for about $10,000 per foot. So a 20 mile stretch from San Jose to Palo Alto, with a tube in each direction, would cost roughly $2B, which is affordable. For a 10% ROI, it would need to generate about $600k per day in tolls. If the toll was $10 each way, that would be 30,000 round trips. Since it could draw traffic from both US-101 and I-280, that is plausible.
Flying cars for mass transportation, with existing tech, are a fantasy.