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.
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.