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All Hope is Not Lost for Flying Cars

September 15, 2015

It’s a huge science fiction cliché, but it’s something people seemed to actually believe back in the 1950s: in the future, there’s going to be flying cars. Wouldn’t that be amazing? No traffic jams, no intersections, go much faster than you could in a street vehicle. Unfortunately, it’s 2015, and we’re still driving around in ground cars. Population is increasing, the amount of traffic in big metropolitan areas is generally rising, and we’re not getting to work any faster.

Why is it that flying cars aren’t a thing? You can easily point to several reasons. For one, the cost of fossil fuels is rising and current Vertical Take-Off and Landing (VTOL) aircraft are not at all energy efficient. A small two-seater helicopter can easily burn 10 gallons of fuel in just an hour. It’s also difficult to imagine that the average Joe could really afford a flying car when even a small used helicopter from 1963 can cost over 130K. Then there’s licensing and safety issues. Drunk driving is a problem now, just imagine if drunk people could fly over the city at high speeds. Maintenance-wise, it’s one thing when your engine stalls on the highway, but imagine what would happen when poorly maintained vehicles break down in the sky.

It recently dawned on me, however, that technology has in fact advanced quite a bit when it comes to flying things. Now, you can buy yourself an electrically-powered, gyro-stabilized quadcopter for just over $50. This wasn’t possible when I was a kid. You’d have been looking at a few hundred dollars for the most basic gas-powered airplane (maybe $500 in 2015 dollars), it would have been a huge amount of effort to maintain, and you couldn’t realistically have flown that in the city.

What does that have to do with flying cars? Well, I had this thought: what if you could scale up flying electric drones? Amazon and Google want to build bigger drones that can deliver packages, but what if you could use drones to deliver people? Thanks to the great push for electric cars, lithium batteries are getting cheaper, lighter and ever more efficient. High-performance electric motors are getting cheaper too. Very soon, it might very well be possible to build electric vehicles that are relatively inexpensive and powerful enough to carry people.

A few days ago, I found out that someone had already built such a thing. The Swarm vehicle weighs just 148kg, sports 54 rotors and can deliver a whooping 22 Kilowatts of power. It’s powerful enough to lift one person and cost just 6000 british pounds to build. Okay, this thing only has an autonomy of 10 minutes, poor controls, and it probably isn’t really safe. It’s really just a prototype, but I still think it’s a great proof of concept. Battery technology is progressing constantly, so within a few years, such electric flying vehicles could likely be made smaller and have more autonomy.

I believe that if such large-size electric flying drones could have just 15-20 minutes of autonomy, interesting applications would already become possible. Doing a little back-of-the-envelope math, the island of Montreal (where I live) is only about 16km wide. I myself am only about 8 kilometers away from downtown. If a flying vehicle could fly at 100 kilometers per hour, it would only need 5 minutes at cruise speed to fly me to downtown, assuming it’s flying in a straight line. Make it 7 a minute flight to account for acceleration and deceleration. That probably leaves sufficient autonomy for the vehicle to return to some nearby supply station to charge.

What, I think, makes such an idea much more realistic is that such drones could be computer-controlled. Completely removing the need for a human pilot makes flights faster and accidents much less likely. The possibility of having multiple independent computer-controlled rotors and multiple batteries also allows for a level of redundancy that might make such a vehicle much safer than a helicopter whose one engine failing means low survivability. If you could add a giant computer-controlled airbag to protect riders, pedestrians and infrastructure from emergency crashes, and cover the drone in flexible foam, you could possibly have a pretty safe autonomous human-delivery mechanism.

The scenario I have in mind goes something like this: you dial an app on your phone, within 4 minutes a flying drone pod shows up, flashes safety lights to signal its presence, and gently lands in front of your doorstep (or perhaps at a designated landing pad). A door opens up, you hop into the single seat, the door closes shut and locks itself, and 2 minutes later you’re already flying away. After a 5 to 10 minute flight, you’re deposited up to 16km away from home. Would you ride inside a drone pod to work, if it could mean completely avoiding traffic and shortening your commute to mere minutes?

EDIT 2016-01-07: the Chinese firm EHang has just unveiled the EHang 184, a prototype of a computer-controlled drone meant to carry a single passenger short distances. This is pretty much exactly what I had in mind when I wrote this post four months ago.

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  1. There’s a couple of laws-of-physics problems with building big drones:

    First, the big benefit of a quadcopter style drone is that control can be entirely in software, with no mechanical linkages needed. This is very important for miniaturized drones, but isn’t an advantage for large craft. A single or double rotor helicopter can generate lift more efficiently than a quadcopter, and the mechanical control linkages aren’t a problem to build at full-scale.

    Second, the lift generated by rotors grows with area (quadratic) while weight grows with volume (cubic). As your craft gets bigger, there is eventually a crossover point where it can no longer generate enough lift for its own weight. The exact crossover point depends on the details (and obviously it can be made to work at human scales, c.f. helicopters), but using the lower efficiency multicopter architecture will lower the crossover point, now increase it.

    This is also the reason why building an electric full-size helicopter is hard: the energy density of lithium batteries is very low compared to fossil fuels, so the mass of any electric craft would be dramatically greater than a fossil fuel craft with a similar flight time.

    • The volume only grows in a cubic manner if you’re talking about a solid volume with uniform density. As for the energy density of lithium batteries: they’re improving constantly, and we now have electric flying vehicles, these are a reality.

      Check this out:

      Many groups across the world are already working on prototypes similar to what I was talking about, that is, electrically-powered single-person flying vehicles. All of these engineers see the potential behind such an idea, and they have working prototypes. Hence, perhaps it’s not as infeasible as you make it out to be.

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