Saturday, December 31, 2016

Flying Cars of the (Near) Future

People have dreamed about flying cars for decades, but the technology has always seemed far out of reach. Airplanes have long been too big, expensive, dangerous, loud, and complex for personal aviation to be more than a hobby for rich people.

But that might be about to change. “There’s a couple of technologies that are maturing and converging” to make small, affordable airplanes feasible, says Brian German, an aerospace researcher at Georgia Tech.

German argues that lighter and more powerful electric motors, batteries that can store more energy, and more sophisticated aviation software could transform the market for small aircraft.

Indeed, several companies are already working on prototypes of car-size airplanes that could soon become cheap, safe, and versatile enough for ordinary people to use them regularly. Google co-founder Larry Page has secretly funded one startup in this market, Zee Aero, since 2010. In 2015 he also invested in another called Kitty Hawk, led by former Google self-driving car guru Sebastian Thrun.

The flying cars of the future won’t look exactly like the ones on The Jetsons. There’s a good chance you’ll rent them on demand from a company like Uber instead of buying one that parks in your driveway — a possibility Uber explored in a recent white paper. But a future where millions of people take short trips by air on a regular basis could be closer than you think.

Silicon Valley innovations are spilling over into aviation

A conventional airplane takes off horizontally, building up enough speed for the wings to carry it skyward. That means a normal airplane needs a long runway to take off and land. Vertical takeoff and landing aircraft, by contrast, take off vertically like a helicopter, then switch to flying horizontally once they’re in the air. That allows them to take off and land in locations where conventional airplanes can’t.

VTOL airplanes are not a new technology — craft like the Harrier and the V-22 Osprey have been around since the 1960s. But these airplanes have never been very practical. They’re complex and expensive, and require pilots with specialized training to fly them.

But a shift from internal combustion engines to electric motors dramatically changes this equation. Electric motors can be much lighter, simpler, and cheaper than traditional aircraft engines powered by fossil fuels — and they’re getting lighter and more powerful every year. And that opens up a lot of new opportunities for airplane designers.

To see what the small, electric-powered aircraft of the future might look like, check out this image from a patent filing by Zee Aero, the Page-funded startup. It shows a tiny personal airplane not much wider than a conventional parking space (you can get a sense of scale from this photograph of a man standing next to a prototype):

It takes a lot more thrust for an aircraft to take off vertically than it does to keep the aircraft moving once it’s in the air. So Zee Aero’s design has eight vertical propellers that are used for takeoff, while there are just two in the back to provide horizontal thrust. Once the plane is soaring through the sky, the eight vertical propellers can be turned off to save power.

This kind of design wouldn’t work with conventional aircraft engines because 10 engines would be way too heavy. But electric motors can be made extremely small and light, allowing even a car-size vehicle to have 10 of them.

Of course, electric motors aren’t a new invention. But they’ve gradually gotten lighter and more powerful over time. Beyond that, it has taken rapid progress in two other areas to make VTOL vehicles practical: batteries and aviation software.

The big advantage of traditional airplane fuel is that it can pack a lot of energy into a small package, minimizing the amount of weight airplanes have to carry and allowing them to travel long distances without refueling.

“Right now, batteries that you could actually put in an airplane wouldn’t let you fly very far,” German says. “But you give it a few more years, and the writing’s on the wall that you will be able to make a very practical aircraft.”

Improvements in battery technology are a spillover benefit of innovations elsewhere in Silicon Valley. The burgeoning markets for laptops, smartphones, tablets, and electric cars have inspired companies to pour billions of dollars into better battery technology. As a result, the energy density of batteries has been improving steadily. And each time batteries improve, electric airplanes can be a little lighter and fly a little farther on a single charge.

German says battery technology isn’t quite there yet. He predicts the energy density of batteries will need to approximately double for small electric airplanes to really take off.

Batteries don’t improve as rapidly as computer chips, so it’s hard to say exactly how quickly batteries will improve. Tesla CEO Elon Musk, who is currently building a giant battery factory, has said that battery density typically improves by 5 to 8 percent per year, which implies that density could double in the next decade — though that could require finding new battery chemistries.

The other key breakthrough is better software. An airplane with 10 propellers is just too complex for a human pilot to manage effectively. But computer software can easily manage 10 propellers at once, supplying power to the propellers where the most thrust is needed.

And German says multi-propeller designs have significant safety advantages. “If you lose one, you still have some left,” he says. “You can design a lot of redundancy.”

The combination of smaller, more powerful electric motors, better batteries, and sophisticated software will open up dramatically new possibilities for aircraft design. I focused on Zee Aero’s 10-propeller design above, but there are lots of other prototypes under development.

by Timothy B. Lee, Vox | Read more:
Image: Joby Aviation and Zee Aero