It's hard to beat the energy density of gasoline. You have to go with either compressed hydrogen, something nuclear, or antimatter. This is bad news for everything that runs on electricity, which includes all of our gadgets, electric cars, and (much more recently) electric aircraft. In order to make electric aircraft viable, a creative solution is necessary, and it doesn't get much more creative than autonomous midair recharging from giant flying UAV battery packs.
The real problem with batteries is that batteries aren't fuel. They store fuel in the form of electrons, but electrons don't weigh anything. With gasoline, it magically vanishes into dirty chemicals as soon as you use it, meaning that your vehicle gets lighter and more efficient as it goes. Batteries, on the other hand, become increasingly more useless as you suck the juice out of them to the point where you're lugging around giant boxes of metal for no reason.
Chip Yates (a world-record motorcycle racer) and a team of engineers think that this is silly, so they've come up with a better idea. Or actually, two better ideas, to make electric aircraft more viable and enable a non-stop flight from New York to Paris that they're calling Flight of the Century.
Better Idea #1: Jettisoning Used Battery Packs. There's absolutely no reason to carry around the extra weight of a depleted battery with you, but you can't just drop them out of the bottom of your electric airplane. Or, can you? The team plans on rigging its battery packs up with GPS-guided parachutes, and when the packs are depleted, they'll be jettisoned one by one and recovered on the ground and then recharged and used again.
Better Idea #2: Midair Recharging with UAVs. Aircraft that run on gasoline can refuel from flying tankers, so why can't aircraft that run on electricity refuel from flying battery packs? The Flight of the Century team is designing battery-laden UAVs that can autonomously dock with electric aircraft, transferring energy and then dropping away to return to base for a recharge. Over a long flight, an aircraft could take advantage of as many of these UAVs as it needs to keep going, and for its NYC to Paris attempt, the Flight of the Century team plans to use five of them, based along the route all the way from Newfoundland to Ireland. It may even be possible to keep an electric aircraft flying indefinitely, using a continuous loop of UAVs that take turns delivering power and recharging themselves on the ground or on marine platforms.
As cool as this system is, it's not going to take the place of jet fuel anytime soon. Chip Yates explains why:
"In the short term, electric airplanes are feasible for specific missions but not as a direct replacement for all fossil fuel burning aircraft. When quiet operations are required, or when the military demands a low heat signature for stealthy operation, or for areas with severe noise restrictions, or for training aircraft doing many landings and take-offs close to an airport, missions like this the electric plane makes sense. One day if society runs low on fossil fuels or when fuel becomes significantly more expensive, only then can you make a direct cost comparison with electric aircraft."
That day might still be a ways away, but it'll be important to be thinking ahead and coming up with innovative (and slightly crazy) methods of making renewable energy do what we need it to do. And to be clear, this whole Flight of the Century thing isn't just a concept: the team is planning battery jettison tests for this summer, with a transatlantic UAV-recharging flight in 2014.
[ Flight of the Century ] via [ CAFE Foundation ]
Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.