Helicopter design isn’t the answer. But electric motors show the way.
Episode Summary:
In the early 1960s, the Hanna-Barbera animated television series, The Jetsons predicted a future world of flying cars and homes in the sky. Flying taxis have been predicted for decades, but physics dictated that vertical takeoff and landing meant the cost and complexity of helicopters. Today, high-capacity batteries combined with lightweight, high-efficiency electric motors promise to make passenger carrying drones similar to small-scale hobby drones: multiple motors, multiple rotors and microprocessor control for stability. The technology will be ready soon. But will the regulatory framework be ready when hardware is?
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Transcript of this week’s show:
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Remember the Jetsons? The bright future where everyone lived in the sky and drove flying cars? Well 60 years on, those flying cars may be just around the corner. In fact, urban air mobility is most exciting new segment in the aerospace industry. And urban is the key. According to the World Bank, 55% of the world’s population, 4.2 billion people, live in cities. By 2050, the urban population will double in size and nearly 7/10 people on Earth will live in cities. More than 80% of global gross domestic product will be generated in cities.
Cities are the future of the planet, and as most people live in them know, mass transit and surface transportation in private cars simply doesn’t work where millions of people are concentrated into city sized areas. But there is a great untapped transportation resource in every city, the airspace above it. The very affluent already use helicopters to exploit this resource, but helicopters have suffered from several problems which have never been resolved: they’re expensive to buy, expensive to maintain, are difficult to fly and can’t operate in an airspace filled with other air vehicles at low altitude. Keeping the flying taxis from bumping into each other is a readily solvable problem, but making a suitable airframe and powerplant is a lot harder.
Until recently, the physics were simple: one or two large rotors, connected to an internal combustion engine or turbine with a very complex gearbox and rotor hub assembly. The most popular configuration is of course a single large rotor with an anti-torque tail rotor, but this design initially presented serious problems. Forward motion meant that the advancing blades had more relative airspeed over the airfoil than the retreating blades, so the angle of attack had to be increased as the blade retreated and decreased and advanced relative to the airflow. The hub mechanism to do this was, and is complex and expensive.
But battery electric propulsion changes the dynamic entirely. Decentralizing power into multiple electric motors carries no significant weight penalty because of the absence of complex gearbox and hub assemblies. Rotors can be fixed pitch, and with four, six or more of them, they can be counterrotating to negate torque effects. The collective control used by helicopter pilots to change rotor blade angle can be eliminated entirely, and replaced with speed control of individual motors. We’ve all seen it with hobby and commercial drones, and the system scales nicely into air vehicles large enough to carry passengers. Battery weight is considerable, but it can be strategically used to optimize the centre of mass for better stability.
Will range be terrible? Yes, it will be. But a 20 minute endurance with reserves should be plenty for intracity operations when you consider the other major advantage battery electric urban air vehicles: the fuel. Electricity is not only readily available, is non-flammable and non-toxic. Every rooftop landing pad can be equipped with charging, and new generations of batteries promise 70 or 80% charging in 15 to 20 minute timelines.
Yes, there’s a lot to resolve, including regulatory approval and the redefinition of air traffic control over cities, but there are no fundamental hardware or software limitations now to making that Jetsons flying pod a reality. How long? I’m guessing the first in five years, and regular service in 15.