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Comment by danbruc | Hacker News Reader

Do we actually want flying cars? They are probably less efficient because you have to overcome gravity, they are probably going to be pretty noisy, falling out of the sky and smashing into the ground is a new failure mode, ...

Flying cars are certainly a nice gadget, but do we really need or want them? I can only think of two good arguments for flying cars, entering the third dimension if we run out of space on the surface and maybe being able to get rid of our current infrastructure, i.e. no longer having to build and maintain roads and railroad tracks and the accompanying infrastructure.

In metropolitan areas it certainly looks a bit like we are running out of space on the surface but I am actually not sure that we are not just pretty bad at making use of the available space. No longer having to maintain a large piece of infrastructure seems actually the more convincing argument to me.

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Surprisingly, they don't actually need to be all that inefficient.

The rolling resistance of a typical car is 0.01 to 0.015 [1], so the effective lift/drag ratio of a car's suspension is about 70 to 100, for just the wheels themselves. Missing from this number are the parasitic losses of all other unsprung mass, aerodynamic drag, and the costs incurred by traveling along roads which are neither level nor straight routes between your start and your end.

Small aircraft have L/D of 10-20 [2], and electric craft will probably fare slightly better if anything because of packaging advantages vs big ICEs.

I might do a more in depth analysis later and write up a Medium post, but my point is: Even just looking at the rolling resistance of the car and the whole L/D of aircraft, the difference is only an order of magnitude. Rolling resistance is one of the smallest contributions to drag in a car, so all up electric cars are probably only 3-6x more efficient than electric aircraft, and combustion cars are probably have a far smaller advantage.

[1]: https://en.wikipedia.org/wiki/Rolling_resistance#Rolling_res...

[2]: https://en.wikipedia.org/wiki/Lift-to-drag_ratio#Examples

I don't think L/D of more than 10 is realistic for a compact VTOL aircraft even in cruise mode, and then there's the vertical take off and landing component that will cause further inefficiency especially on short trips. But at the same time I don't think it matters that much.

Depends on the type of VTOL. Quad copter? Not so efficient. Tilt-wing? I imagine it's much better. (Amateur opinion disclaimer)

iirc a v-22 is below 5:1 and somewhere around 3:1

The new DEP designs will do better, but exceeding 10:1 seems unlikely

You need compare the whole system: internal combustion engine plus the gas tanks to feed it, versus an electric motor plus batteries.

The energy density of batteries is far worse than gasoline. Also, after you burn gasoline, you don't have to carry it anymore, which isn't true for batteries.

Also consider that for a plane, running out of gas can be fatal, so you can't actually use all the range. There needs to be a safety margin.

And then, consider that a practical flying car can't actually take off or land like a plane, and probably can't have the wingspan of a plane, so you might want to compare to a helicopter instead.

I have been working on a flying car project for years and can guarantee you that one/two seat Electrical VTOL is at least 30 years away, battery density must triple and then you have regulations.

Current solutions can be airborne at maximum 15 minutes considering that FAA and other agencies require 20 minutes reserve you do the math.

The Zee.aero patent design as been abandoned because they couldn't scale it to fit a passenger inside.

If by "flying car" Larry really means "Toyota Camry that can fly with middle class people inside" then that's obviously preposterous to anyone with the slightest shred of general aviation experience.

If he means "VTOL Cessna with really good avionics" it's still a tall order but perhaps within the realm of "eventually possible given great determination and unlimited money" instead of "laugh him out of town."

the cost it's also another big barrier I don't see it hitting the market at less than $250k.

As a proxy you have Icon A5 it was target at a price point of $130k in 2008 currently it's priced around $240k and only a handful have been delivered.

https://en.m.wikipedia.org/wiki/ICON_A5

off course it will be possible when batteries tripple the density without increasing weight.

You will get a 25 minute around 30 miles ride with 20 minute reserve

And without being a fire hazard.

with current battery technology this is controlled but with new tech chemistry this could become a problem.

Biofuels. Otherwise, you're waiting another 20 years.

to do a small combustion engine VTOL vehicle its even harder I have only seen it work with several two stroke engines.

Another optin is turbine like the AirMule, but will be hard to use it for civilian operations the hourly cost is brutal and noise and heat is really annoying for nearby people and even passengers.

https://en.m.wikipedia.org/wiki/Urban_Aeronautics_AirMule

the two stroke VTOL is homebuilt

http://www.dailymail.co.uk/news/article-2123200/The-ultimate...

as a sidenote contrary to the rest of the world there is no regulation in the USA for a electrical LSA Ligh Sport Aircraft because it can only be powered by internal combustion engine the FAA is taking more than a decade to add two words to the regulation "and Electrical" imagine how much will take to develop a completely new regulation for electrical VTOL.

Eh, it's not that far away if we really wanted to push it.

Just add an airfoil envelope with enough of something lighter than air(heated air, helium, w/e) to offset the weight until a decent performance point is met. The heat from the engines running could help heat the gas for added efficiency.

Hybrid airships are already being marketed by Lockheed Martin so this isn't revolutionary at all.

what about the joby s2? Is that also impossible? It looks feasible and there are a bunch of people working on it... Thoughts?

similiar glider designs to Joby S2 get 1h to 1h30 flight time with current battery density, it all depends how much energy is spent doing the vertical takeoff and landing.

For electrical VTOL the Joby is probably the best bet, one big question mark is, the 16 motors how much will weight even at a very low weight of 15kg each you get 240kg/52lb in motors a similar complete two person glider weights around 300kg/661lb.

Motors will be more like 1kg each. One can get a 10 kilowatt 1 kg air cooled motor.

Batteries are the heavy bit, and in my opinion, the future there is to have batteries capable of 2 minutes of flying, and a gasoline engine as a hybrid generator.

don't know if you ou will manage lift with 160kw will depend on overall weight, you also have to factor the weight of the propeller and rotating mechanism and covers so 10 to 15 kg is not exaggerated.

Rich people want them. What society wants (needs) is a superior airport experience and more fuel efficient air travel.

I'd prioritise high speed rail over more efficient air travel. But rail is not always feasible.

https://tools.ietf.org/html/rfc1925

   (3)  With sufficient thrust, cars fly just fine. However, this is
        not necessarily a good idea. It is hard to be sure where they
        are going to land, and it could be dangerous sitting under them
        as they fly overhead.

>Do we actually want flying cars?

There's probably a market for a vertical-takeoff vehicle serving a premium/luxury transportation niche - the same segment that is currently served by helicopters. I imagine you would still need a pilot's license and have to adhere to the rigorous FAA-maintenance schedule - so it would never be a mass-market product.

Many products (cell phones, cars, medical) started off for "the rich" and gradually became mass market. I am very surprised at how many people are not able to see a future where general purpose ground based transportation is obsolete.

It'll happen once the strict licensing is no longer needed. Currently the necessary training for flying is too long and expensive for most people.

And this is where the autonomous flying is coming into place: you will not fly this car at all. Software will be certified for this.

Which means:

1. wait for tesla like autonomous software that works for cars - we have for planes but this is a bit different 2. either high density batteries for electrical engines or very light weight ICE engines ( biodiesel or bio ethanol ) to be mass produced

It's not just the flight training that's the problem. It's the expense of maintaining and certifing the vehicle, and those regulations will never be loosened.

That's how I read this. They basically want a cheaper autonomous-helicopter-uber-like service for mid-level execs.

Two related things that first jump out to me as interesting:

- Opens up a lot of potential living space which is geographically close, but not practically connected via transit arteries

- Opens up living space in areas which are not passable by cars either because of terrain or in-tact wilderness (e.g. an off the grid home on a nearby mountain)

Both would no doubt mostly benefit the rich, but well, nobody's shocked that this is where that's targeted.

Wouldn't you still have to build infrastructure to those places to build the homes in the first place? I guess if you are filthy rich you can just airlift things in and out again.

You can source many if not most building materials from the environment wood can be chopped and made into lumber and plaster can be made out of local deposits.

If you have some sort of a mobile house factory that will utilize local materials and 3D print the rest you really only need to worry about a few materials that can't be locally sourced.

Yes this is far away but about as far as flying cars.

Heck In 2 decades you might order a house on amazon a blip will come and set it down some roomba style bots will come out and finish it and you'll jump into your flying car and move in.

When you can 3D print almost anything including your food and produce electricity locally via wind and solar you can now live in the middle of nowhere Alaska without much infrastructure.

If we're talking about the class of people who will use a flying car to get to work, airlifting containers via helicopter to construct their home is probably within reach.

Bridge choke points, mountain ranges and other small body of water crossings is where electric flying cars / taxis will shine. It would be very useful in cities such as Seattle, SF or NYC. It would also be useful for places like Victoria-Vancouver or Victoria-Seattle. You either take an inconvenient ferry for ~3 hours or you could take an on demand air taxi for 30m.

> You either take an inconvenient ferry for ~3 hours or you could take an on demand air taxi for 30m.

The SF-Alameda-Oakland ferry is already 30 minutes :).

Sorry I was unclear. I was talking about the Victoria-Vancouver ferry, which is about 3hrs. Same with the Seattle-Victoria Ferry.

The SF ferry is also slower than driving with no traffic or bart :)

But we already have point-to-point 4-seater "air taxis". They're way more expensive than a ferry otherwise they'd be everywhere, and there's no reason to think a flying car would be cheaper.

...I hate to be aggressive here, but did you read the darn article? It's the reason we're even on this page, and it directly addresses your point. That's even underselling it, the entire purpose of the article is to ask and answer your point.

My fault; I should've elaborated. I absolutely do believe that underlying technology will improve and get cheaper. I don't think that the cost of getting that technology in the air (FCC certification, maintenance, etc.) will come down significantly.

Small aircraft are already not a whole lot more sophisticated than a production car - and often less so. But nonetheless they're still an order of magnitude more expensive.

It does not so much address the issues as it glosses over them. For example, it assumes that past battery performance trends can be extrapolated, but the battery-makers, -engineers and -chemists themselves do not expect this. Nor does the article attempt to address the noise problem.

I walked away with the impression that trends couldn't be extrapolated, thanks to various snippets from the article, but there's no pull quote that clearly proves it, so, sure.

The noise problem you brought up apropos of nothing.

You're responding to a comment responding to a comment that had concerns that were already addressed by the article, to let me know your concerns weren't addressed by the article. Surely there's a better place in the comment hierarchy for this? You'll get ignored down here.

There are four consecutive paragraphs saying that battery technology is almost there and improving rapidly, and nothing more on the topic, so it is interesting that you got the impression that trends could not be extrapolated.

Yeah, I don't know either. Maybe don't think of them as flying cars, but instead as cheap helicopters on-demand.

Of course we want. But to see why, you can't imagine it as a car, like everybody insist. It's will be a vehicle, but not a plane, a drone or a car. They will not compete with these.

We definitely need for example a faster way to transport rich people than cars, but cheaper than planes in short distances.

We definitely need a better way to transport patients between hospitals than ambulances and helicopters.

We need to see the future here, not the past (the outdated idea of 'flying cars')

Let's build a bot to participate in HN discussions. Then we can all save some time and get back to work. My first two suggestions:

Q: Someone is building flying cars.

A: Do we really need them?

Q: Someone is investing money into extending human life.

A: Let's talk about the social implications of immortality.

We can abstract this a bit

Q: Innovation announced! A: Not possible based on my legacy experience/guild qualification.

That doesn't actually generalize GP, but presents a very different issue (neither of the examples you claim to be "abstracting" involve challenging the possibility of the announced innovation.) GP is more "Announcement: Innovation! Response: Questions about utility and/or unintended consequences."

There are advantages that can make them more efficient:

- Straight line transportation, saving energy & time

- Faster speedwise

- No infrastructure needed, software is basically infrastructure

- Can handle rough terrain with less maintenance

- Can deal with traffic better or have more concurrent bandwidth.

- Can allow cities to de-concentrate and people to live further away. Our model at the moment is the city model where everyone needs to live in population centers to work well.

- Less time wasted in lifts if the car is parked on the terrace.

- Less need of properties to be adjacent to roads or the cost basis of new developments to be cheaper.

- No driving needed, simplistic autopilot can work.

- No bridges needed to cross water bodies.

I would argue there's no need to ask if people want or need it, it's one of those things everyone has dreamt with lust about at some stage or another.

If seen on a massive scale, I'm not so sure about some these arguments.

Air transport will need management for safety reasons, which means air corridors, landing areas, some kind of ATC system. Which correlates to infrastructure costs, not so straight line transportation and not so time efficient commutes.

As activity centers tends to be somewhat concentrated, huge amount of flying cars will tend to go or left small areas at the same time, creating air traffic jams to land or take off.

Classic infrastructure will still be needed to transport heavy items, such as large quantities of food, machinery, etc. Even the construction phase a new developments will need those roads and bridges.

Strangely, faster transportation doesn't mean shorter commutes, quite the contrary, the average commute time tends to go way up when transports evolve to become faster and denser as it enables urban areas to grow even more. The real alternative is to "de-concentrate" activity centers to have relatively autonomous parcels with residential, work and commerce close together and necessitating only light transport forms (by foot, by bike, or light transports like tramways).

Flying cars are also mostly "fail catastrophically systems", it's good that motors are redundant, but there are not the only items that can fail. Batteries, the control surfaces, the inboard computer, or the whole structure can fail. Flying is also quite hard, specially in difficult meteorological conditions, building automation to handle such cases will be extremely hard (I've no competences in the area but the picture of a vertical landing in windy condition, seems a bit frightening).

Interesting statistic: on a per journey basis, airplanes have 2 to 3 times more death than cars, (on a per km basis it's very safe), imagine what it would looks like with a lot of small commutes.

I'm not convinced it's really the solution... I see it at best as a cheaper and more accessible helicopter ride.

Straight line transportation

Roads are quite straight over long distances, and planes don't fly in straight lines if there's something in the way (eg a storm). I wonder if there'd really be that much difference on a journey longer than a few hundred miles.

Any idea that could be a solution for roadkills deserve to be explored at least. Think in the millions of terrestrial animals, some endangered, that we could save each year.

Would be a real blessing for vanishing amphibians, hedgehogs, snakes, endemic terrestrial crabs, big cats... On the other part could be a problem for birds, bats and flying insects also, of course. And will boost the feral cat problem.

For good or worse, from a environmental point of view would be a real game changer.

Isn't that like someone in the 19th century predicting that automobiles will never happen because rail is so much more effective, comfortable, safe?

Convenience and flexibility always seem to win in the end.

Rail and electrified commuter air could be complementary. Nothing beats rail for moving large number of people efficiently.

Its not going to be flying cars as in a replacement of cars, not for a long time. What is needed is short "hops" in crowded areas.

San Jose -> SF is the example in the article that Uber gave.

Flying cars won't be used in the same role as land cars. Unless you live some kind of extreme rural life in Montana or something and have money, it's not something an individual would own.

I've always imagined micro airports. They'd be like train stations. Need to get from Irvine, CA to Pasadena, CA in 20 minutes?

With this approach the flight paths could be deterministic and the cars could be reused all the time.

Yes, we want flying cars, and yes we "need" them if we want to solve congestion and traffic as our planet grows beyond 10 billion people.

> if we want to solve congestion and traffic as our planet grows beyond 10 billion people

These are all symptoms of a badly designed city. What a place like this needs is better infrastructure, especially public infrastructure such as bike lanes, buses, and trains so that a lot of that traffic isn't necessary. Getting more people into cars will only create more problems. All you're doing is moving that traffic and congestion into the sky. If you said we needed an airbus, I'd point you to my friend who is named "airplane".

You don't get to redesign all the cities of the world, and it'd be a mighty impressive feat to move all the traffic to the sky.

There's also a lot more sky up there than there is land down here.

I think that most people who want a flying car imagine a world in which they are one of the few owners. Larry Page might be one of the few who could achieve that goal, but only so long as they are too expensive for the rest of us.

I certainly think "flying buses" should come before flying cars.

I think of low-cost airlines like that. Once I got on one with a terrible hangover in Slovakia and woke up in Italy an hour later, I don't even remember taking off. :)

We already have ryanair and easyjet.

Talking mainly about inter-region transportation. Hop a "bus" from Palo Alto to SF, etc.

If we think it of as helicopter with less (?) noise and less helipad area the first market is probably the same that uses now helicopters for urban transport.

> Do we actually want flying cars?

Agree. Not every improvement in technology is actual progress. Let's skip flying cars and wait for teleportation.

You're thinking too narrowly.

- Solve traffic

- Live in Santa Cruz, commute to SF

- Buy a mansion in Modesto, commute to Palo Alto

- The views!

These will be VTOL, electric, autonomous air taxis, not road-drivable cars.

> The views!

Obviously, these will be blocked by swarms of flying cars.

Long after they're blocked by swarms of delivery drones.

I'm skeptical about delivery drones for this reason. Between the noise, security concerns, and visual pollution it will be hard to implement mass adoption of UAV's for delivery.

I could see delivery drones for last-mile drop offs... imagine delivery trucks as automated machines with a small swarm of drones (4-6) per truck.. the truck drives a route on the main street(s), while the drones do the drop-off to the door.

It could work in that scenario... My biggest thought for drones, is it won't work from the distribution centers, simply because they are too far out from a lot of the drop off locations.. but combined with trucks, you could have the trucks drive less in-out, and drones for drop off. Would need a handler in addition to a driver though, depending on automation capability.

This would also need to be supplemented with uber-like service for deliveries that don't fit well for drone drops.

You can run the motors out of phase to cancel noise.

It doesn't work.

> - Live in Santa Cruz, commute to SF

Or we could be more ecologically and energy conscious...

Like the people currently taking private jets and helicopters!

+1 travel as the crow flies from Oakland to Mountain View in a fraction of the time. Pagether

Do people really believe that flying cars would solve traffic? Now all the traffic is in the sky! And thanks for ruining everyone else's view with your cars. Not to mention flying cars would be extremely hazardous depending on the height. You'd pretty much be required to create specific airways and means of signaling at busy locations. Congratulations, you just created another layer of roads.

You can stack the traffic. Delivery drones will kill the view anyway. You can build in passive safety + have them follow freeways.

Have you ever heard of a little thing called traffic?

Or something called a "speed limit"?

Can't believe this is the top comment on HN. Reddit? Sure, but I expect better here...

Conceivably traffic in the air would still be a problem once we get enough volume, unless we permit cars just fly wherever (huge danger!). Similarly, speed should probably be limited unless we want 200mph cars crashing into a building.

The application for it might be another form of mass(less) transit. Think about dedicated, low-lying air paths for travel between cities in the Bay Area: airBart

It's not about space ...it's about congested roads. Dedicated rail (or tubes for high speed over long distance being the exception) for mass transit is not the way to think about our improving our cities anymore. There will be a hardware - and software - solution.

Air travel means noise and carbon emissions. There is no way it's more efficient than ground based public transportation anytime soon. I work in the aviation industry and the slightest change brings a huge amount of public outcry. Between the noise, visual pollution, and energy issues it's just not going to happen.

Bad existing public transportation doesn't mean that all public transportation will be bad.

Yes we do! That's one of the things that is slowing down the whole civilization -- inability to quickly and efficiently travel especially into the places when we need to gather to do work.

Opening a new dimension will be like switching from a horse to a first Ford car - day and night in terms of speed. Practically no more traffic jams because you can always travel at higher/lower travel channels.

> They are probably less efficient because you have to overcome gravity

Yes but eventually it might get narrow. At least you wont be stuck in traffic burning gas but constantly moving.

> they are probably going to be pretty noisy

If you plan a picnic on a silver cloud 10k feet above the ground then yes. For majority of people living in cities on the ground, it won't. I can imagine first flying cars will be very noisy just like first cars were pollution monsters... but let the Government impose fines and never-ending restrictions that will make sure car makers invest large chunks into quieting them down.

> falling out of the sky and smashing into the ground is a new failure mode

First and foremost, the only way you will fly in a car when it is 100% autonomous. There will never be a car that you can control manually. Perhaps only military/LEOs/etc, but for us civilians it won't do. Most likely by the time they fly above your heads - 10-15 years from now? most street cars will be automatic as well.

You will never own the car by the way. You won't be able to make any modifications etc. You will pay equivalent to your current car payment but you will only rent (good thing is you can always get new model without hassle of selling your old one).

In terms of smashing, I bet the first design to fly human will be made with airbags covering the whole thing, similar to the recent rover flying to the Mars. By the time you "smash" to the ground, you will be one huge bouncing ball of air.

Flying cars will move us into another lap of human evolution! No doubt about it.

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