February 02, 2015

Electric ducted fans

I'm an armchair dilettante when it comes to most hobbies, the same way I like hardware stores and watching This Old House but never plan to own a home. I'm not interested in model planes; it's the technology that fascinates me.

When I was a kid, model plane power plants came in three varieties: your arm, rubber bands, and (glow plug) diesel. Those glow plug engines were temperamental too. I recall as much effort being spent getting them to work as flying the planes.

These were free-flight or string-controlled planes. Though RC (radio controlled) model planes did exist, the technology was rudimentary and expensive.

Now it's sophisticated and cheap. Digital wireless, lithium-ion polymer batteries, and microprocessor-controlled brushless electric motors have eliminated most of the old frustrations.

Helicopter drones have been the big winners in this new market, both hobby and pro. And now there's the electric ducted fan.

The EDF is an electric fanjet that does a good job of pretending to be a turbojet. Scale models using EDFs mounted in lightweight expanded polypropylene foam airframes look and fly like the real thing.

Here's a F/A-18 powered by a pair of EDFs.

Quite often in science fiction these days, it's the fiction that has to catch up with the science. The original Star Trek got the flip phone right. But it and its sequels couldn't foresee the practicality of drones. The military certainly has.

Full-scale electric planes do exist. Elon Musk sees a future for them in commercial aviation, when "everything but rockets--ironically--will be electric." He'll be right if he can increase the energy density of batteries an order of magnitude.

Alas, even Musk admits that most of the battery "breakthroughs" publicized on a nearly weekly basis are impractical nonsense. Some day soon, hopefully. Unless you're flying model airplanes, that is. They work fine now.

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# posted by Anonymous Dan
Very impressive technology. Electric motors make so much more sense for models because, as you wrote, the fuel motors were smelly and unreliable. Likewise electric makes sense for lightweight personal aircraft for the same conveniences. The key being personal and lightweight. The combination of innovations in material and electronics has opened a lot of new machine applications. I suppose with foam materials it would not be far fetched to imagine individuals "flying" to work on their electric air "cycles". But it is a huge leap to go from applications demanding tens of equivalent horsepower to those requiring thousands.
2/09/2015 8:46 AM