Last month, a team of researchers led by MIT’s Steven Barrett demonstrated the first heavier-than-air craft to fly without moving parts. Their plane creates thrust by using electrodes to generate an “electric wind” or, in Barrett’s preferred nomenclature, “ionic wind.”
Barrett said his dogged pursuit of the plane—he’s been working on it for years—was rooted in his appreciation of the silent, propeller-less crafts in science fiction like Star Trek. But the phenomenon of movement created purely by electrical charge is both much older and much stranger than that.
Note: Major thanks to Myron Robinson, who traced the history of electric wind in a technical paper written for the military in 1960. It’s available online. The Xerox is terrible, but everything that’s legible is interesting.
An ionic, or electric, wind is the result of a flow of ions between two electrodes. In the case of the plane at MIT, negative electrodes are embedded in the plane’s wings, and positive electrodes are mounted on wires in front of them. When the positive electrodes are highly charged, positive ions flow from them towards the wings, bumping into air molecules—creating a focused wind that reaches 200 mph.
Humanity first got wind of this idea centuries ago. A phenomenon related to the so-called “electric wind,” corona discharge, is first described by Otto von Guericke, who also invented the vacuum pump. He had mounted a sulfur sphere on a crankshaft. When the globe was rubbed by hand as it rotated, it began to glow and make noise in the form of “roarings and crashings.”
In the mid-18th century, a man called Wilson invents, and a man called Hamilton perfects, something that comes to be known as “the electric fly.” In this device, a charge is delivered to wires arranged in an “s” shape, causing the wire to spin like a pinwheel. (Mr. Wilson’s and Mr. Hamilton’s first names have proved hard to find; 1864’s 27th volume of The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science provides only their surnames.)
For the next century, luminaries including Peter Mark Roget of Roget’s Thesaurus and Svante August Arrhenius, who first defined acids and bases, debated what the hell actually causes the fly to fly.
German scientist August Toepler uses a technique called schlieren photography, invented to study supersonic motion (and still used to visualize airflow around airplane wings) to visualize what was then known as the “electric wind.”
American scientist and tinkerer Thomas Townsend Brown publishes “How I Control Gravitation” in Science & Invention Magazine. Having discovered ionic wind and built devices that use it to move, he writes of the interplay between electrical fields and gravity, which… isn’t quite right.
Still, not content to stop there, he explained how his work is rounding out Einstein’s Theory of Relativity: “Einstein’s field theory is purely mathematical. It is not based on the results of any laboratory test… The new theory accomplishes its purpose by ‘rounding out’ the accepted Principles of Relativity so as to embrace electrical phenomena. The Theory of Relativity thus supplemented represents the last word in mathematical physics. It is most certainly a theoretical structure of overpowering magnitude and importance. The thought involved is so far reaching that it may be many years before the work is fully appreciated and understood.”
Popular Mechanics publishes a cover story on the Ionocraft, a direct forbear of the solid state plane. It points to the ionic wind the plane generates straight downward so it flies straight upward. (It’s also called a “lifter.”)
PM describes it as an “incredible magic carpet of the future” and—perhaps with an eye to Townsend Brown’s dubious reputation—declares its creator, Major de Seversky, as “no crackpot” but “a practical visionary who in many areas has been far in front of his field.”
The article also hits on a potentially huge benefit that Barrett suggests about today’s plane, too: Given its lack of moving parts, and thus near-nonexistent maintenance requirements, an ionocraft covered in solar panels could stay aloft almost indefinitely.
A 2009 NASA review of Ionic Wind Propulsion off-handedly mentions that many of the same principles are used by a commercial air purification device called Ionic Breeze. Then a major part of the gadget lineup at The Sharper Image—which said the device “mysteriously circulates air without a fan”—the Ionic Breeze was the root cause of a series of lawsuits, including one brought by The Sharper Image against Consumer Reports after the latter said that, honestly, the IB didn’t really work. The Sharper Image lost.
Today, a decade after filing for bankruptcy, The Sharper Image still exists as an online retailer, and still sells a successor of the Ionic Breeze.
2012: Ionic laptops
Apple is granted patent number 8,305,728, “Methods and Apparatus for Cooling Electronic Devices,” in which the company raises the possibility of using ionic winds as a cooling method for devices like laptops. The problem with using ionic winds for this purpose, according to the patent, is that ionic winds only flow in a straight line from one electrode to another, while in a laptop, different parts of the circuitry may need cooling at different times (e.g., if you’re gaming, the big heat source might be the GPU, but if you’re just checking emails, that wouldn’t be the case).
The patent details a method of generating electric or magnetic fields to act as deflectors, so the ionic wind could be directed on demand to the most important heat source. As of now, Apple hasn’t actually put the technologies in the patent into service.
Scientists from Deponegoro University in Indonesia present findings in which they use ionic wind to dry slices of wild ginger, an Indonesian plant used in herbal medicine, which must be dried for storage. Drying via ionic wind is more energy-efficient than using ovens, and more hygienic (and predictable) than drying in open air—not least because the electric discharge kills microbes in addition to creating airflow.
Originally posted on Popular Mechanics