Look! Up in the sky! Is it a drone? Is it a car? It's both, crossed with Uber

@Christian Berger - "don't have enough of that material on earth"

Don't have enough lithium? Seriously?? It makes up 0.0017% of the Earth's crust. That may not sound like much, but the thing about the Earth's crust is that there's rather a lot of it. 0.0017% is twice the abundance of lead and 9x the abundance of tin, and I've never heard anyone worry about running out of either.

I gather you've probably read some alarmist article that does math based on known "reserves" of lithium and yearly production, to see what happens if every car uses lithium batteries, we use them for home energy storage, etc. and says "OMG we only have a decade's worth!" Reserves beyond a few decades are meaningless, because if you have 50 years of known reserves of something, no one is going to pay to explore to find 50 more years of reserves.

The best information I could find said lithium production in 2014 was 36,000 metric tons. Compare with the amount of lithium dissolved in seawater, estimated at 230 billion tons. That's a tiny tiny fraction of the amount in the Earth's crust. I think we're fine. If demand goes up, people will spend money to look for more lithium, and they will find it, because its literally everywhere.

Re: "The internal combustion engine" [...] is designed to use fossil fuels

>The concept assumes the ground and air modules will be battery-powered and therefore more environmentally-friendly than petrol-burning cars, which of course neglects the very real possibility the electricity charging those batteries was generated in a coal-or-oil-fuelled power plant.

It neglects nothing. Whilst burning fossil fuels is likely to play a part in generating said electricity, these fuels aren't being burnt in densely populated cities, i.e in the environment that many people live in. CO2 emissions are a concern, but in a city other emissions and soot are a real health issue.

Re: "The internal combustion engine" [...] is designed to use fossil fuels

Correct.

If solar panels, wind farms etc instead of feeding electricity to the grid, were powering some apparatus to convert CO2 and water into hydrocarbons, you could burn the fuel thus produced with an almost net zero emissions. (almost due to process inefficiencies).

Hydrocarbons have a far higher energy density than even the best batteries, AND their weight is removed from the vehicle once they are used, as opposed to batteries that weigh the same charged or empty. MUCH more suited to aviation

Re: "The internal combustion engine" [...] is designed to use fossil fuels

@Paul Kinsler

I take your point but I would offer that these engines really are designed specifically to burn fossil fuels. Different hydrocarbons have different properties and these properties matter to the operation of the engine.

Take biodiesel. If you put 100% biodiesel into a regular diesel engine it may work but it is likely to cause damage - if not in the immediate future then further down the track. That is why using biodiesel (at least at higher mixtures) tends to void your warranty and (e.g.) cars may specify the allowable percentage of biodisel.

Likewise petrol cars. Yes, like diesel, you can generally use low percentage ethanol blends with no ill effects but not 50%. Indeed, most cars list the specific fuel you should use and the reason is that the engine has been designed with a specific rating in mind.

It is, of course, possible to design an engine to run specifically from biofuels but the reality is that the overwhelming majority of engines are designed to use fossil fuels instead.

The point is that, while different hydrocarbons may be able to be used, engines are designed to utilise one specific type and, even when an engine will work with different blends of hydrocarbons, there is usually a trade-off - either in power or longevity (though at lower blends, this is very slight). A battery-powered electric car is able to use any source of electricity available without any performance impact.

Re: And if you think about it for more than 10 minutes...

Currently space is not an issue because there isn't many of them, get 2 million of them up there each needing to be at least a mile apart from each other and things change.

Also Air traffic control is stressful with the current setup, imagine people having to organise that many flying vehicles. Yes I know they would intend to automate it, but that is not currently the case.

Re: And if you think about it for more than 10 minutes...

The extra dimension gets you very little since it increases the complexity of control by an order of magnitude. Consider if you're dividing the atmosphere into bands then you're creating corridors of limited space which is what you state is the cause of congestion and collision.

Worse in many cities there are tall vertical structures that one would have to fly between further limiting space and reducing the 10 m bands to near copies of the existing streets. Complicating that further is the need to traverse between bands to get the the proper band. In a city the "flying cars" will be functionally flying over the roads unless the aim is to go a substantial distance or for intercity travel where you first rise to clear the entire city.

You're also ignoring the fact that much of the congestion is caused by people going to and from the same hubs whether it's Times Square or Madison Square Garden or the East Village. The only place where the flying cars will have an advantage is when it can avoid geographical bottlenecks like the Brooklyn Bridge or Holland Tunnel.

Lastly there's one problem that nobody seems to mention and that's noise. These flying cars will have to be far quieter than a helicopter or typical drone if they're ever going to be accepted in any great number. If it's a problem that's been solved it must be expensive to implement since it isn't often that a subsonic flying object sneaks up on anyone.

Re: And if you think about it for more than 10 minutes...

No, it takes more energy to fly the same distance, all else being equal. If a ground car has to take a long, windy route and constantly gets stuck in traffic, while the flying one can do a direct route with no delays, it's no longer cut and dried.

Any flying car that's actually usable in real cities will necessarily have to be some sort of STOVL aircraft. That takes *vastly* more power than a runway takeoff - which is why our old aircraft carriers were fitted with ski-jumps for the Harriers.

You have to have a particularly contrived scenario to make STOVL flight more energy-efficient than surface transport.

Flying gives you effectively unlimited extra space to use - just divide the atmosphere into 10m altitude bands and you quickly have tens or hundreds of times more capacity

And you also have carnage. Minimum separation distances are 5 miles horizontally and 1000 feet vertically, although this can be reduced to 3 miles under certain conditions. And you need separation even if your aircraft are under automatic control - as most aircraft are these days - because you need manoeuvring room in the event of some sort of problem.

Aircraft crashing in mid-air during a flight is almost unheard of; even the most dangerous near misses usually involve planes only being with a few hundred metres of each other

That's true today - but wasn't so before aviation authorities got the idea of minumum separation properly established; you only have to go back to 1956 to see what happens when minima can be ignored; that one cost 28 lives, and led to sweeping (and necessary) changes in aviation procedures.

There are plenty of real problems flying cars have, most of which come down to safety. Limited flying space causing congestion just as bad as on current roads is absolutely not one of them.

Spend some time around light aircraft and you'll come to understand just how wrong is that assertion...

Vic.

Re: Transport isn't solved

I'd sort of assumed a decent speed - say, 100mph straight-line. Nowhere near easyjet speeds, but with a 5 minute to strap-in, rather than 3 hours.

That would be enough for me to want to / be able to live outside the megacity, if it wasn't a daily commute.

How fast do we think these embiggened quadcopters can go? (and, come to think of it, how come they're so much more compelling than regular helicopters? If they are, why do helicopters still exist?)