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'Lifter' design used as a thruster to power a model plane

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Dr. Slack

Thu Nov 22 2018, 06:26AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Guardian

There's a link in the Guardian article that redirects to a free, non-printable, non-downloadable (but screenshottable

) copy of the original paper *

There's also a whole bunch of youtube videos appeared, search for 'ion drive first flight'.

Steven Barrett at MIT has apparently put a proof of concept plane together with onboard battery, multiplier, and corona wires to make a serviceable free flying model plane. Turning a thruster through 90 degrees and using it with wings for lift is a standard technique that makes fixed wing planes way more efficient than helicopters. I'm interested in his claim that ion wind is comparable in thrust to power ratio to that of jets. I'm not sure that jets are the gold standard for low speed work, I would have thought spinning props were, but at high speed where props don't work so well, maybe.

Approximate key specs to save anyone having to read the article -
2.5 kg all up weight
5m wingspan
5m/s flight speed
600W power input
3.2N thrust
200V battery, H bridge at 600kHz to x15 resonant transformer, CW cascade to 40kV

In the last part of his conclusion, he compares it favourably to the first flight of Kittyhawk

* I originally cut'n'pasted the Guardian link into this post, but that only went to the paywalled version. The link when used from the Guardian article context redirects to the full paper, albeit with view-only access. There's obviously some scripting magic going on that I don't understand. I don't know how long that facility will remain available, get it while it's hot. If it's stopped working already, ask and I can send you the screenshots, it would take only a few minutes to manually reconstruct in your office app of your choice.

Dr. Slack

Thu Nov 22 2018, 06:29AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

hit the wrong button, mods please remove this double post

Nickel

Thu Nov 22 2018, 01:32PM

Registered Member #4367 Joined: Thu Jan 26 2012, 07:54PM
Location: NE Hampshire UK
Posts: 16

Google: < ionic wind plane > for more info.

Patrick

Fri Nov 23 2018, 01:16AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

im highly skeptical. the lifters idea has always been 3-5 % effciency.

Dr. Slack

Fri Nov 23 2018, 02:36PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Patrick wrote ...

im highly skeptical. the lifters idea has always been 3-5 % effciency.

Skeptical about what?

The paper seems quite thorough and plausible, so I'm happy that he's done what he claims. In fact he claims about 2.5% efficiency.

Skeptical about future application of this to flight? Absolutely.

For one, I wonder how this engine would cope in the rain, or even fine mist. That's rather like the Daleks' plans for world domination being scuppered by the first flight of stairs they come to.

Secondly, one parameter he mentions in his paper is thrust per frontal area of the aircraft, a pressure if you like. He quotes his as about 3Pa, that's 3N for about 1m2 total frontal area. A commercial airliner comes in at about 1kPa, which is why it can go somewhat faster. It's probably something to do with a jet engine compressing the air before adding heat. The ionic thrust is only acting on ambient pressure air.

But a fun demonstration nonetheless.

Weston

Fri Nov 23 2018, 08:25PM

Registered Member #1316 Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365

I used to work in the research group that did the electronics design work for the project and have sat through a few presentations on it, it's pretty cool.

As far as I know, it's the first self powered craft capable of flight with ion wind based propulsion. By using a glider/plane instead of the conventional 'Lifter" configuration you avoid the need to have to directly generate vertical thrust equal to the mass of the craft.

Uspring

Thu Nov 29 2018, 01:47PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
Location:
Posts: 711

I'm interested in his claim that ion wind is comparable in thrust to power ratio to that of jets. I'm not sure that jets are the gold standard for low speed work, I would have thought spinning props were, but at high speed where props don't work so well, maybe.

Exactly, jet engine efficiency in terms of energy consumed compared to kinetic energy imparted to the plane is atrocious for low speeds. The problem is, that ion thruster don't have enough power to accelerate planes to a velocity, where the efficiency becomes sensible. Apart from that, an ion thruster can match a jets thrust/power ratio.
At low velocities props are much better as exemplified by reports about a human powered helicopter, which was able to take off for a few seconds.

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