Flight powered by ionic wind: a notion from the wilder shores of UFO spotting? Or an idea whose time has come? If new aviation-related research at MIT really can bring this arcane phenomenon into play, the ultimate prospect could be planes with no fuel on board. Ned Allen, Chief Scientist at Lockheed Martin, speaks of its “nearly miraculous potential”.
We’ve known since the 1950s about ionic wind – more properly known as electro-hydrodynamic thrust. Using highvoltage electricity, air molecules are ionised and repelled from a thin electrode, and simultaneously attracted towards a thicker collector (such as an aluminium tube). They push on the surrounding neutral air molecules, whose displacement generates the thrust. Some Soviet satellites relied on this for propulsion, once in space.
What’s new is the remarkably high efficiency achieved in the MIT experiments. This convinces Steven Barrett, Director of MIT’s Laboratory for Aviation and the Environment, that ionic wind is “definitely worth investigating further”. By increasing the distance between the electrode and the collector, his research team found that total thrust per kilowatt was maximised at low velocity over a large area – and reached 110 newtons, or 50 times more than a modern jet engine.
The energy density of aviation fuel has hitherto put it in a class of its own for propelling planes – but at great environmental cost. So, ionic wind is exciting if sustainable flight is your dream. But don’t hold your breath. The challenges for aircraft design are massive, to say the least. Getting a big enough gap between the electrode and the collector to achieve the high efficiency rates seen in MIT’s lab might mean encompassing the whole plane within the thruster. Moreover, you’d need lightweight portable power, perhaps from solar or fuel cells, to produce enormous voltages to get the whole caboodle off the ground. You might not want to be sitting inside. And, once up, efficiency decreases at speed.
If this ever does take off, its first application may be in unmanned drones for military surveillance, with the big bonus that their motorless flight would be noiseless and have no infrared-detectable heat signature.
Then again, there could be other uses for ionic wind. An Apple patent application published last year, for instance, would harness it to keep laptops cool – silently. Now that would be nice.
Photo credit: NASA