Ion Drive of an Airplane - from MIT

[Tom.G]

 

[Mark44]

I wonder how they powered the thing. At the front is a thin wire at + 20,000V and at the rear is a plate at -20,000V. This isn't feasible for batteries I don't believe, so maybe big capacitors?

 

[collinsmark]

I wonder how they powered the thing. At the front is a thin wire at + 20,000V and at the rear is a plate at -20,000V. This isn't feasible for batteries I don't believe, so maybe big capacitors?

I suspect some sort of switched mode power supply (SMPS) is used.

Switched mode power supplies are nothing new. But with today's integrated circuit (IC) technology, they are more ubiquitous than ever before. You probably use several (at least indirectly) every day without even knowing it.

Although they can involve AC current/voltage (an example being a device that plugs into your car's cigarette adapter and produces a standard 120/240 V AC output, for camping and whatnot), they are typical used for DC-to-DC converter applications. Applications that change a lower DC voltage to a higher DC voltage are called "boost" converters, and those that go from a higher to lower voltage are called "buck" converters. In certain applications, a SMPS "buck" regulator is more efficient than the more traditional "voltage divider" based regulator because it removes the IR drop losses (this depends on the application though).

Often, you can use the same IC (or internal circuit block, if it's an embedded circuit) to operate as either a boost or buck by merely changing the external circuit topology.

It's likely some sort of SMPS (whether it be boost or buck) is used not just in your computer's main power supply, but also in your computer's motherboard, computer's graphics card, your cellphone, e-cig battery module, electric car, etc.

SMPS are also commonly used as LED drivers, functioning more-or-less as a constant current source in this configuration. Here, they can automatically increase their voltage (often well above the battery's DC voltage) regardless of how many LEDs in series are active in the circuit. [Edit: by that I mean to match the number of series LEDs in the circuit. I.e., if you wish to reduce the number of active LEDs, you simply short them out, and the SMPS adjusts its voltage accordingly, all automatically.]

+/- 20 000 V is a lot, of course. I'm guessing in this ion drive application there's some sort of "flyback" circuit involved (which, btw, is another type of SMPS).

My point of all this is that with modern electronics it is pretty easy to go from one DC voltage to another DC voltage (and to do so pretty efficiently too).

 

[Peter Terren]

I have been making "flying" contraptions with ionic levitation for many years called "lifters". These are light weight, flimsy and made with balsa, foil and cotton in a triangular shape. They are tethered to the ground that with fine wires feeding 80kV. At this voltage the device is buzzing with corona and occasional 4cm arc overs.
The 80kV version weighs 4.6 g and can lift 4.1 g ie roughly its own weight. It is about 30cm on a side and snaps up to the tethers at around 30cm. This is a better ratio than many helicopters but the rub is that a lifter has a power supply on the ground.
The 2,400 g aircraft as described in this article has been able to lift off with an on board power supply within the very stringent weight restriction. Horizontal flight makes this more feasible than vertical flight as in a lifter though.
My lifters and details here:

http://tesladownunder.com/Lifters.htm