Seven Solutions Flying Cars Need (and One They Don't)

Seven Solutions Flying Cars Need (and One They Don't)
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Everyone's very excited right now about "flying cars" because—hey, who wouldn't be? It's right up there at the top of the science fiction wish list, along with the robot servant who cleans your house for you. And now we're being told pretty frequently that the flying car is on its way.

But we're not getting a lot of sober discussion about the problems that actually need to be overcome before you can go airborne on your morning commute. Here are seven big problems we're going to have to solve before flying cars can make it to the masses.

1. Rotor Wash

Here's where I get on my soapbox and insist that almost everything we're being told is a "flying car" isn't really a flying car. It's pretty straightforward. A flying car is a car that flies, which means that it has to be capable of driving down a normal roadway.

A few of the "flying cars" we're being shown fit that bill, like the new one being developed by Toyota, which we are told will be able to drive on the roadways before taking off vertically—though it is still in the very early stages. Then there is the Aeromobil, even if it looks like a distinct compromise as an automobile. It might not be fun to drive, but you can drive it. Most of the vehicles billed as "flying cars," however, are small fixed-wing aircraft that either won't fit on the road or won't really be fast enough or maneuverable enough to do more than taxi out to the helipad.

That brings us to a bigger issue: the helipad. The Aeromobil might be able to drive on the roads, but it needs a runway to take off. Most of the other options, the ones presented by Uber, Lilium, or Airbus, require a helipad—or a cluster of helipads, which Uber is calling a "vertiport."

This is not the "flying car" of science fiction, because it doesn't fulfill the dream of point-to-point travel, where you can take off from anywhere and go to anywhere. The reason you need a runway or helipad mostly has to do with rotor wash: the downward blast of air required to lift a VTOL craft off the ground, which also requires a significant clear space around the vehicle for everyone's safety. This is more than just a disappointment to fans of "Blade Runner" and "Back to the Future"—both of which promised us flying cars that would just float off the ground. It makes a material difference for the ability of small VTOL aircraft to ease the morning commute. You might just end up trading time stuck in traffic for time waiting in the queue at the "vertiport."

I don't think anyone is going to solve this problem, short of developing a radically new method of propulsion. But this means that "flying car" is not going to be an accurate term for the new transportation method we're talking about. "Air taxi" would be much more accurate. And while air taxis might not be quite the same thing as flying cars, they're still pretty cool, right?

Who am I kidding? Everyone is still going to keep calling them "flying cars," because clicks.

2. Infrastructure

If air taxis are going to become an everyday means of transport for millions of ordinary commuters—as opposed to a luxury for the wealthy, like helicopters today—then we're going to have to build "vertiports" densely packed into urban and suburban environments. The scale of this undertaking will be huge. If you have a thousand people working in an office building, then you're going to need to be able to accommodate at least 1000 arrivals every morning and 1000 departures every evening. The same goes for an apartment building with 1000 residents, which means about 1000 departures in the morning and 1000 arrivals in the evening.

This is a massive infrastructure challenge. The way you accommodate that much traffic right now is either to assume most people will take mass transit (if you are in a densely populated city) or to build a parking lot or parking garage. Perhaps most of that parking space can be converted to vertiports, but because of the prop wash issue I just mentioned, the amount of space required for a vertiport landing pad is much larger than for conventional parking spaces.

For high-rises in dense city centers, this is even more difficult. Parking garages for automobiles are often built into the lower levels or even the basements of the buildings, where they are least accessible to small aircraft, while rooftop space is very limited. The most densely packed urban centers with the most ground traffic are the places where we most badly want the advantages of traveling by air—but those are precisely the places where the problem of providing sufficient vertiport space is most difficult.

3. Noise

Now imagine yourself having breakfast in that apartment building you share with 1000 other residents—as dozens of them are lifting off outside your window to join the morning commute in their air taxis. Given current technology, the noise is going to be terrific.

Again, the problem is the rotors. Anything capable of moving enough air downward to lift a small aircraft upward is going to have to beat the air with rotors at high speed. Small drones already sound like enormous angry wasps buzzing. Or consider that relatively small test version of the Toyota flying car. That sound you hear isn't the engine; it's using relatively quiet battery-powered electric motors. That sound is the rotors beating against the air. And that's just for a small, relatively light test craft.

Now magnify that by ten or a hundred or a thousand, and make it the constant background noise for a city where a significant number of people are traveling by air taxi, and you get something pretty intolerable.

This problem can probably be solved, and some developers are claiming that they have quieter systems in the works. But they're going to have to demonstrate that.

4. Safety and Reliability

Now consider what happens when everyone lands at the vertiports to go into their office buildings or go shopping or whatever else they want to do. When your air taxi lands, we have the additional challenge of safely off-loading the passengers from the aircraft and moving them away from the landing pad. This will limit how quickly air taxis can be moved through the vertiports, which will be another big bottleneck for their capacity.

That's just the beginning of a bigger question of safety. The reason most of us are so comfortable with the idea of routine air transportation is because we're used to flying on large commercial airliners. Through decades of effort, airplane manufacturers and the big airlines have reduced fatal accidents to a level so low they are measured in terms of loss rates per million departures. Even then, it is measured in fractions.

But air taxis are more similar to small private airplanes, which have a much higher accident rate. The fatality rate for general aviation is just over one death per 100,000 flight hours. One analysis compares that to accident rates for automobiles: "The fatality rate [for cars] was 1.1 deaths per 100 million vehicle-miles traveled. Assuming an average vehicle speed of 50 miles per hour (a big assumption), the fatality rate for automobiles translates to 1.1 per every 2 million hours." Multiply that by a vastly increased volume of traffic, and you will more than take back the thousands of lives projected to be saved every year by self-driving cars.

Large airliners have the benefit of experienced professional pilots (more on that in a moment) and, just as important, large ground crews who thoroughly check the vehicle between flights and are available around the clock to perform maintenance and make repairs. How would we scale this up to accommodate a whole new vast sector of air taxis? How much is it going to cost? And how will it affect the ability of air taxi services to provide transportation on demand?

If airlines have conditioned us to expect safe transportation, modern automobiles have conditioned us to expect reliable transportation. Automobiles are much simpler vehicles than air taxis, and we're used to driving them for three to five thousand miles before needing so much as an oil change, and we're now used to having warranties that stretch out to cover the first 100,000 miles. For most of us, our cars are just there for us, every morning and every evening, ready to be used at the turn of a key (or the push of a button), without any special need for maintenance. Air taxis are going to have to rival that level of reliability, but they still have a long way to go.

5. Stable Avionics

Before we talk about long-term reliability, we have deal with the short-term task of surviving our first flight. Have you noticed something about all of the videos you see of flying cars or VTOL air taxis? You can see it in that Toyota test, or in this promotional video for the Kitty Hawk flyer. VTOL vehicles are wobbly. This is true of drones, too, but because they are smaller and with less mass, the variations are not as visible. The bigger and heavier the vehicle, the more chance that the wobble created by trying to balance a load on top of a collection of whirring fans will be impossible to control. It will either be a deadly ride, or one that leaves you airsick.

There is a general sense that flying cars are easier to pilot than self-driving cars, because in the air, there's plenty of room and you're less likely to hit anything. But a car at least has four wheels planted firmly on the ground. It doesn't need to have complex algorithms just to stay upright. A truly smooth flight, not to mention an enjoyable one, is going to have to depend on taking the task of balancing and stabilizing the craft out of the hands of a human pilot and giving it to computers that can make adjustments with lightning speed. That brings us to the next big issue.

6. Autonomy

The reason we need algorithms to make flying cars work is because there aren't enough pilots, and even if there were enough pilots, they are too expensive. The two issues are related. To say that there is a shortage of pilots is really to say that not enough people want to become pilots at the current pay level. We could eventually increase the number of pilots, if we increased their salaries dramatically enough to induce people to invest in the training to switch over from other careers. But higher pay would increase one of the largest expenses of operating an air taxi, making it even less viable as a means of transportation for the mass market.

While everyone has a drivers' license today and can drive themselves, the requirements are far less rigorous than those for a pilot's license—particularly one that licenses a pilot to fly in the dark or in bad weather. And that's what we want, if this is going to be our new morning commute. We want to be able to fly if it's raining, or to fly to the symphony hall for a concert in darkness and fog. After all, those things wouldn't stop an automobile.

So air taxis or flying cars are not going to become a common means of transportation unless they become autonomous and pilotless—fully and safely.

7. Air Traffic Control

We don't just need autonomous technology to run the aircraft. We also need new technology to coordinate an air taxi's route through crowded airspace.

Currently, there are about 7,000 commercial aircraft in the United States and about 225,000 general aviation aircraft, but the air traffic control system is already stretched to its limit.

There are more than 250 million ground vehicles registered in the United States. To move even a small fraction of the traffic from these vehicles into the air would require at least a ten-fold increase in the capacity of our air traffic control system. That's before we consider the thousands or millions of drones that we're expecting to have in the same future that brings us flying cars or air taxis.

Add to this the fact that we're going to want air taxis to take us on small, individual, often unplanned flights to a large number of small destinations within densely populated urban areas. That's far more complicated than guiding a few thousand large commercial jets along established routes between large airports.

We're not going to expand the existing air traffic control system to handle all of that traffic. Instead, we will eventually require some kind of radically new, fully automated air traffic control system that can be scaled up to handle the sheer numbers and complexity of a world with flying cars and drones. There are companies like AirMap that are already working on this, developing software systems to coordinate weather data, the heights of structures, the movements of other small and large airborne vehicles, federal, state, and local airspace restrictions—everything needed for a next generation air traffic control system that just might be able to handle the mass adoption of air taxis. But it's a heroic task, and it's going to take a long time to make it a reality.

You would think that all of this would be more than enough, but it seems that every time we hear about a flying car project, one of the first things we hear is the one thing that is not strictly necessary to make a flying car work.

1. Electric Motors

It seems like every flying car design is based on electric engines powered by big batteries, and this is regarded as a necessary component of the project, for reasons that are never quite clear.

Yet this is the one thing that is likely to delay flying cars the most. There may be some benefits to an electric-powered aircraft, but the battery technology just isn't here yet, and by some projections it is not likely to be here for another thirty years.

It's all about power to weight ratios: "Right now, the specific energy of batteries is roughly 2 percent that of liquid fuel. Factor in the efficiency of electric powertrains compared to internal combustion engines, and you get closer to 7 percent—so 1,000 pounds of jet fuel yields about 14 times more energy than a 1,000-pound battery." Then take into account the fact that a 1,000-pound battery takes hours to recharge, while 1,000 pounds of jet fuel or gasoline can be pumped into a fuel tank in mere minutes, giving the internal combustion engine a huge advantage in efficiency and availability.

Of course we all know what is driving the mania for electric aircraft. Fears of global warming and the belief that we have to abandon the internal combustion engine in favor of electric vehicles. This, in turn, causes technology writers to enthusiastically snap up any corporate PR claiming to have made an advance in that direction, even when the numbers don't really add up. And Silicon Valley entrepreneurs respond to these incentives. They can all see what happened to Elon Musk, and they're smart enough to try to make the same thing happen for them: to be seen as the tech visionary who is saving the planet. So they don't dare be the guy who says his flying car is going to burn gasoline and emit carbon dioxide.

But it probably will. We just looked at the other seven enormous challenges any attempt at an air taxi system has to overcome. Innovators are likely to solve those problems first, at which point they will build their vehicles around whatever power technology is most practical. Which probably won't be electric.

Those are the big challenges for people who want flying cars or air taxis: building a whole infrastructure for vehicles that are quiet, safe, unfailingly reliable, stable, and autonomous both in their own operation and in their coordination with everything else in the sky. That's more than enough to worry about.

Rob Tracinski is the editor of RealClearFuture.

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