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Friday, March 1, 2024

To Solve Flying Cars' Battery Problem, Tie Them to Power Lines

Of the many challenges facing the nascent flying car industry, few turn more hairs gray than power. A heavier aircraft needs more power, which requires a bigger battery, which weighs more, thus making a heavier aircraft. You see the dilemma. So how do you step out of that cycle and strike a balance that lets you fly useful distances at useful speeds without stopping to recharge?

One startup thinks the answer lies in another question: Who needs a big battery, anyway?

San Francisco-based Karman Electric proposes dividing the need for power from the need to carry that power through the air. It wants to connect passenger-carrying electric air taxis to dedicated power lines on the ground, like an upside-down streetcar setup. The aircraft will carry small batteries so they can detach from the lines when necessary, but they’ll get most of their juice from their cords, allowing them to cover long distances at high speeds.

A few more questions, then. What happens if the cable gets jammed, or a bird flies in its path, or a helicopter wanders by? What if there’s a power loss on the ground, or if two vehicles get their cords tangled? How can you traverse bodies of water or rugged terrain? And doesn’t tying a flying car to the ground defeat the whole purpose?


Karman cofounder Chiranjeev Kalra, an alum of Virgin’s Hyperloop One program, has a surprisingly reasonable set of responses to this unsurprisingly wide array of concerns. For starters, the vehicles will pull power from the ground only at altitudes of 30 to 100 feet, outside of dense population centers. If they’re flying through a city, or approaching their destination, they can disengage from the power line, pull in the tether, and run off their own battery, flying as high as 3,000 feet. “This portion of the flight is untethered and operates on batteries,” Kalra says, “typically the so-called first or last mile of intercity travel.”

The idea of routing power straight from the grid to a moving electric vehicle is as old as the moving electric vehicle. Trolleys have been doing it for more than a century. In cities like San Francisco, buses and streetcars use this setup. It’s common for trains, too. The setup has even been broached as a way to run long-haul trucks on electricity instead of diesel. Karman simply inverts the idea, combining the flexibility of an air vehicle that can detach and go anywhere whenever necessary—something trains can’t do—with the efficiency of a grid-powered system.

Named for Hungarian aerospace engineer Theodore von Kármán, the company debuted the idea with a demonstration at Bentonville UP, a secretive, invitation-only air taxi conference held this past weekend in Bentonville, Arkansas. Karman engineers strung a pair of wires between two supports and flew a small quadcopter drone back and forth between them. Karman is developing a full-scale, six-rotor demonstrator now and expects to start testing by the end of the year.

A full-scale system could, Kalra says, transport 10,000 people per hour for hundreds of miles between cities, cruising in close formation at speeds north of 200 mph. That makes it more capable than an aircraft that can use only as much power as it can afford to carry. And while it doesn’t eliminate the need for room on the ground, Kalra says stringing those power lines is still easier than building, say, a hyperloop.

“This is a completely open system,” Kalra says. “Aircraft can leave or enter the power track at any point and land wherever they need.” At those entry and exit points, the “WireRunners” that connect to the ground track would be “flown” down via built-in drones, then retracted via the same setup at the end. And if a cable does get caught on something, a quick-release mechanism stops it from taking down the aircraft—which should have enough battery life to manage a safe landing.

Of course, the key question isn’t how this idea compares to the hyperloop. It’s how it compares to solutions that actually exist—like commercial air travel, highways, trains, and intercity bus networks. Could it compete on efficiency or cost? How long would it take to build, and how much would it cost to maintain? Large infrastructure projects like laying hundreds of miles of power cables are always complicated and expensive, at least in the United States. Throw in the serious regulatory concerns the flying car space already faces, and this looks like a rather hard sell.

But if Karman can handle those concerns without getting itself tied up in knots, at least it won’t have to worry about where its power is coming from.

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