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Take a look at the slightly earlier thread "MIT designs ekectric plane with no moving parts" which seems to have been referring to the same work.

Sadly, nobody had got to the details of the electrical system - which turns out to be pretty much what I suspected that it would be - and I'm glad you managed to dig it out.

The series-resonant inverter does seem to be a variant of the Baxandall Cla ss-D resonant inverter, which has been around since 1960

Of course the paper was published in a UK journal, so Americans don't know about it, and Jim Williams even called his version of it a resonant Royer i nverter. Royer published even earlier, but his inverter was strictly square wave, and not at all resonant.

On Dec 4, 2018, snipped-for-privacy@ieee.org wrote (in article):

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In the Nature paper, they do discuss the electrical system design process, which was basically an optimization process. The airplane was also designed using the Geometric Programming approach to optimization, this probably being the only practical way to find the one design that _just_ worked.

Could be. I bet MIT just threw in all known topologies and let the optimizer proccess run.

't know about it, and Jim Williams even called his version of it a resonant Royer inverter. Royer published even earlier, but his inverter was strictly square wave, and not at all resonant.

Well, we do know of the IEE (UK, not IEEE (US)) around here, and you do see cites all the time. Probably people wanted square wave inverters, for efficiency, not sine wave.

Joe Gwinn

... after it crashed a lot of times.

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The UK IEE became the IET in 2006, so your claim does rather reinforce my p oint.

As Jim Williams pointed out, the Baxandall inverter can be remarkably effic ient - he finally got around 95%.

The point about series resonant inverters is that their switching transisto rs switch at points in the cycle where the current through the transistor,a nd the voltage across them are both minimal, which does cut switching losse s.

Of course this is the DeSeversky Ionocraft. But thrusting sideways, rather than an ion-helicopter. And with a breakthrough: carrying it's own H.T. power supply on board.

Unfortunately they can't increase the voltage by a couple of orders (and proportionally increase the thrust.) If you built a "Lifter" back in the 1990s, you'll have seen the spark-breakdown that imposes a serious limit.

But still, having it fly its own batteries on flea-power thrust is impressive.

Bill Beaty wrote

A balloon can do that better.

On Dec 4, 2018, snipped-for-privacy@ieee.org wrote (in article):

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Hairsplitting. The question was about the IEE when Baxandal published.

And, yes I do know about IET (nee IEE). IEE was probably more-or-less forced to change their name, because people confused IEE and IEEE.

IEE/IET papers, not just IEEE papers.

Yeah. But Jim W rescued the Baxandal circuit from obscurity. The question was the comparison before this improvement happened.

You may have the last word.

Joe Gwinn

On Dec 5, 2018, Bill Beaty wrote (in article):

Cute. I recall ionic-wind propulsion articles going back forever. Still a flea, after all these years.

Joe Gwinn

Maybe someone can get a publication out of flying a plane on energy harvested from convection currents in the atmosphere.

Look! No fuel, no batteries. Imagine the novelty!

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Rumour has it that he got given the circuit - but not the original paper - by somebody in the UK, where it was well known among people like me and the late Tony Williams.

Since the circuit seems to have been developed for photomultiplier power su pplies, it was easily adjusted to generate the even higher voltages requir ed to excite cold-cathode backlights in lap-top computers, and Jim Williams did that. He didn't "rescue it from obscurity" but rather exploited it in a new application.

As far as I can see, Jim Williams didn't "improve" the circuit at all. He j ust optimised versions of it for the back-lighting job.

MOS-FET switches work better in the inverter than do bi-polar transistors, and aren't susceptible to the squegging problem, but Jim Williams doesn't s eem to have exploited them.

You are playing to one of my known character defects.

Flight schedules aren't too reliable. Slope-soaring might work better, as long as the prevailing wind is actually blowing.

There have been many such attempts, and they would be commercially important for drone survellance flights.

So far they have failed to reliably find thermals /before/ you blunder into them - and then there is the problem of locating the thermal's core.

Skilled pilots can increase the chance by looking for the right type of clouds that are just beginning to form, or combine harvesters, or stubble fires, or circling buzzards (not vultures), or...

I know all that. My attempt at irony passed you by, it seems.

Jeroen Belleman

Tom Gardner does seem to fly sailplanes from time to time. He may know people who have tried to make money out of getting engine-free aircraft to do scheduled tasks (as opposed to amusing gliding enthusiasts).

Your proposition might not have been quite as ironic as you imagined.

There have been many attempts. The latest clutch seems to be around small drones, e.g. to stay up indefinitely when tracking animal poachers in Africa.

Obviously the military has a continuing interest as well.