Cannae/EmDrive

[Rakaydos]

Many thanks for whomever gave the pointer to the NASA forum,I shall have a look through it when I get back home. However, assuming that there is a valid, real efffect here; if it is so tiny, then it's unlikely to have any practical use so far as I can see (solar sails and ion engines would likely be more useful). If it's a case of it being an effect that can be amplified in some way with teh right setup, that may be more interesting. But the very fact that the effect exists (if it does) is very interesting indeed from the point of view of helping t improve our models of how the universe works,even if it doesn't have any practical use.

At present, it stillmodels out as being MORE effcent than an ion drive.

[spudman2]

The official article is here but you have to pay for it.

Good thing my university pays for access to arc.aiaa.

[Scotius]

Can you give us, laymen a quick run-down of the article when you finish reading it?

[CptRichardson]

I can well understand people being skeptical at whether the Cannae drive actually produces any thrust without using reaction mass (NB: reaction mass and fuel are not necessarily the same thing . In a chemical rocket they are the same thing, whereas in an ion engine, the reaction mass is ionised and thrown out the back - but some source of power is required to both ionise the reaction mass and charge a grid to repel it, whether that be solar power,a diesel electric generator or a lump of plutonium. )

Many thanks for whomever gave the pointer to the NASA forum,I shall have a look through it when I get back home. However, assuming that there is a valid, real efffect here; if it is so tiny, then it's unlikely to have any practical use so far as I can see (solar sails and ion engines would likely be more useful). If it's a case of it being an effect that can be amplified in some way with teh right setup, that may be more interesting. But the very fact that the effect exists (if it does) is very interesting indeed from the point of view of helping t improve our models of how the universe works,even if it doesn't have any practical use.

And if it turns out that the claimed effect doesn't actually eixst, but is an artefact caused by X (where X is some as yet unidentified bit of teh experimental setup) that's still interesting. At least the whole thing isn't obvious crank science, like yer average perpetual motion or free energy claimant.

For its size, it's still twice as efficient/powerful as a classic Hall ion thruster that would be comparable in size/mass. And this is the unrefined prototype stage. Provided they can tune it, we're looking at 8 times as much thrust as an ion drive.

[Esme]

At present, it stillmodels out as being MORE effcent than an ion drive.

But efficiency isn't the same as usefulness. For instance, if the thrust to weight ratio for the drive is too low, then an ion drive might still be more suitable for work in the outer solar system - or a light-sail in the inner. But that's very interesting, if the efficiency is higher. Depending on how much power it needs, could be a candidate for interstellar probes, maybe?

[magnemoe]

But efficiency isn't the same as usefulness. For instance, if the thrust to weight ratio for the drive is too low, then an ion drive might still be more suitable for work in the outer solar system - or a light-sail in the inner. But that's very interesting, if the efficiency is higher. Depending on how much power it needs, could be a candidate for interstellar probes, maybe?

Drive system itself is pretty lightweight and you don't need fuel who is itself increases the twr, efficiency here would be trust / kw,

[skyace65]

Take that physics and your laws

http://www.ign.com/articles/2015/07/28/impossible-em-propulsion-engine-confirmed-by-scientists?utm_source=IGN%20hub%20page&utm_medium=IGN%20(front%20page)&utm_content=20&utm_campaign=Blogroll

and for those who want the more wordy and scientific article

http://arc.aiaa.org/doi/abs/10.2514/6.2015-4083

[Redshift OTF]

Ooh interesting. No-one's dis-proved it yet anyway.

[sal_vager]

Guys, I'll be rolling this into the main EMdrive thread.

Also, Tajmar was only trying to rule out outside causes and mistakes in testing, he didn't try to validate the drive itself, though if you can get access to the full paper you'll find he did find thrust and couldn't find a cause, but it's paywalled or I'd post my copy.

[Kryten]

IGN, really? That's the best you could find?

EDIT: Also note this is a conference presentation, not a peer-reviewed paper.

[skyace65]

IGN, really? That's the best you could find?

EDIT: Also note this is a conference presentation, not a peer-reviewed paper.

It's the first place I heard about it working.

back to the drive itself. I wonder, if we had a bigger drive with enough thrust for a manned spaceship, maybe a mass driver could be used to launch it into space.

[Redshift OTF]

I still reckon it has something to do with the Casimir effect. I think the Casimir effect occurs when two plates exclude certain wavelengths of virtual particles between them forcing the plates together. Perhaps this drive, if it works, excludes virtual particles from forming in a certain direction creating thrust.

[AngelLestat]

So this big annuncement and we can only find a note in "IGN" or "quora", "hacker-magazine"??

I never wanted to enter in this discussion because there was nothing solid to talk about.

But I really wish they sent this thing to space once and for all to confirm if it works or not, because all these "ghost test" that it works are starting to be annoying.

-If it works.. a big congratulations to the creator and all its fans, lets used and find why it works...

-if not.. good.. we can close this topic once for all.

[vger]

This is really getting ridiculous now.

http://www.ign.com/articles/2015/07/28/impossible-em-propulsion-engine-confirmed-by-scientists

Martin Tajmar, the German scientist who has been independently testing the EM Drive, has a history of debunking experimental propulsion systems.

http://io9.com/no-german-scientists-have-not-confirmed-the-impossibl-1720573809

Two German researchers claim they have produced measurable amounts of thrust using a copy of NASA’s controversial EMDrive. It’s a result that has many people talking, but don’t plan your trip to the to the Alpha Centauri system just yetâ€â€the experts we spoke with are all highly skeptical of the study and its findings.

So in summary: Yesterday, we had skeptics with experience in debunking, who tried to debunk the EM Drive and were unable to. Now we have skeptics who are skeptical of the debunking skeptics.

[sal_vager]

From what I read, they found a thrust of about 20 micro newtons, not pico newtons as some have reported, they also found true reversal of thrust after they ruled out the magnetic damper by swapping it for oil damping and heat by using a ton of glass wool insulation, all this was in a vacuum.

Thrust was in-line with Shawers calculations, though their drive, and they built their own for these tests, was only 700watt (household microwave oven magnetron), but they had the most accurate testing rig possible (apparently in the world).

Their Q factor was low due to a fudge up with the epoxy sealing the small end, and Q went down during testing due to oxidization of the internal surfaces (testing started in air, moved to a chamber later).

The test device was essentially hollow with a commercial wave guide bolted to it, then the magnetron.

The one thing that was brought up at the end of testing was possible magnetism from the power feed lines, which ran to liquid cups to prevent any movement of the lines transferring force, but the lines themselves were just bunched together to reduce electromagnetism, not wound together, so there may have still been some.

The thrust seems to be linked to the temperature of the device, as thrust was measured in most cases while it was still warm, it only actually reached 35°C though, with most of the heat in the magnetron.

They did mention that if they shut off power early the thrust would instantly stop, but if allowed to "charge up" (that's the term in the paper) it kept running after power was removed.

No explanation is given as to the cause of the thrust, nor was the test even looking to verify the device, the only intention of the testing was to find overlooked possibilities which they were unable to do.

[Frozen_Heart]

This is really getting ridiculous now.

http://www.ign.com/articles/2015/07/28/impossible-em-propulsion-engine-confirmed-by-scientists

http://io9.com/no-german-scientists-have-not-confirmed-the-impossibl-1720573809

So in summary: Yesterday, we had skeptics with experience in debunking, who tried to debunk the EM Drive and were unable to. Now we have skeptics who are skeptical of the debunking skeptics.

People will continue being sceptical until its being used in space... and probably afterwards as well.

I still think its some error or magnetic interaction but this does give me hope that it could be real and useful.

[Linear]

Normally i would be laughing right now, but i keep reading and reading and...it just seems more plausible.

Recorded thrust near equation numbers, getting to the point where there are only a couple experimentation error possibilities, i'm getting excited now.

[vger]

People will continue being sceptical until its being used in space... and probably afterwards as well.

I still think its some error or magnetic interaction but this does give me hope that it could be real and useful.

It's just gotten to the point where I feel like I'm reading a drawn-out argument between science and religion (through the news reports I mean, not on this board). But I can't even be sure which "side" is which anymore. It's all variations of "You can't prove a negative," and "new evidence isn't really evidence because unicorns still can't exist," etc etc etc.

[sal_vager]

The news articles are definitely a poor source for any real information on this, remember they largely cater to the mass market readers, as far as I can find there simply is no adequate explanation at this time.

[Technical Ben]

So a heat leak/engine of some type? If heating is the main factor, and not the actual magnetron?

[sal_vager]

So a heat leak/engine of some type? If heating is the main factor, and not the actual magnetron?

Might be a novel form of thermal radiation thruster, though I have read that pure radiation thrusters are really feeble, but as thrust did change with Q factor it's hard to rule out the need for the magnetron.

[SuperFastJellyfish]

http://tu-dresden.de/die_tu_dresden/fakultaeten/fakultaet_maschinenwesen/ilr/rfs/forschung/folder.2007-08-21.5231434330/ag_raumfahrtantriebe/JPC%20-%20Direct%20Thrust%20Measurements%20of%20an%20EM%20Drive%20and%20Evaluation%20of%20Possible%20Side-Effects.pdf

Here is Tajmar's write up. It was only paywalled before the conference talk today, AFAIK

Edited July 28, 2015 by SuperFastJellyfish

[Darnok]

It isn't science if you allow only solutions you accept

[sal_vager]

That's fantastic SuperFastJellyfish, now everyone can read it.

Also, if anyone is having trouble with off-topic posters don't forget you can put people on your ignore list in your account settings.

[Scotius]

Tajmar's device heated up only to 35 degrees Celsius? Isn't that a bit too low to produce any noticeable outgassing?