EM-drive fizzle

[Adam Dray]

The latest test suggests that the EM-drive doesn't work (article in New Scientist).

Thrust effects might be an interaction between the unshielded cables and the Earth's magnetic field. There might still be a thrust effect to take advantage of, but a) it would only work within a planet's magnetic field and b) it doesn't violate any known laws of physics.

But it's just one test, at low power, and the jury is still out. The science doesn't bode well for the EM drive, though (Occam's Razor, and all that).

 

[mike wightman]

The jury is not out. Real scientists have now carried out real experiments.

The em drive is not a reactionless drive, it is just a result of the magnetic field interactions of the current carrying wires powering the 'drive'.

It's always a shame when real science spoils the claims of mad inventors...

 

[atpollard]

The jury is not out. Real scientists have now carried out real experiments. ... It's always a shame when real science spoils the claims of mad inventors...

Sure. :rant: You scoffers said the Dean Drive would never work, and here I am enjoying my flying car ... o: Oh, wait ... (never mind)

 

[wellis]

The jury is not out. Real scientists have now carried out real experiments.

The em drive is not a reactionless drive, it is just a result of the magnetic field interactions of the current carrying wires powering the 'drive'.

It's always a shame when real science spoils the claims of mad inventors...

So what could this drive be potentially used for then? Some sort of maglev in an atmosphere?

 

[Gray Lensman]

So what could this drive be potentially used for then? Some sort of maglev in an atmosphere?

Not a science type but would the power requirements to be effective be economically viable? I sincerely doubt it.

 

[Charles.Darney]

Sure. :rant: You scoffers said the Dean Drive would never work, and here I am enjoying my flying car ... o: Oh, wait ... (never mind)

Any car can be a flying car.

Once.....

 

[Gray Lensman]

ahem ... real flying cars

I know, they are weak, but they do work, and more will come.

 

[Adam Dray]

The jury is not out. Real scientists have now carried out real experiments.

The US/NASA and Chinese experiments that showed thrust were carried out by real scientists, too. This is another attempt to falsify the results, with success (so to speak) this time. I think one experiment isn't enough to be conclusive.

Even they say they will have a real answer within the year.

 

[mike wightman]

The US/NASA and Chinese experiments that showed thrust were carried out by real scientists, too.

The vast majority of the physics community questioned the validity of their methods at the time of their experiments, this latest experiment that actually does the science right shows the EM drive is yet another bottle of snakeoil

This is another attempt to falsify the results, with success (so to speak) this time. I think one experiment isn't enough to be conclusive.

It's cold fusion all over again...

Even they say they will have a real answer within the year.

Want a wager on what it will be?

 

[Adam Dray]

The vast majority of the physics community questioned the validity of their methods at the time of their experiments, this latest experiment that actually does the science right shows the EM drive is yet another bottle of snakeoil
It's cold fusion all over again...

Want a wager on what it will be?

It's a good thing that "questioning" isn't a conclusive part of the scientific method!

I'll wager that it turns out to be magnetic effects from the cables. But again, it's a good thing that gambling isn't a conclusive part of the scientific method.

If you note the subject header I picked, I believe that the EmDrive is dead, at least as earlier "understood." It might turn out to produce some useful thrust property based on magnetism, though, and anything that converts microwaves to thrust (even just within the Earth's magnetosphere) is incredibly useful.

 

[inexorabletash]

Generating torque against a planetary magnetic field isn't totally useless...

https://www.movaglobes.com/how-mova-globe-works/

Saw these at a museum gift shop. Looked up how they worked... and was still impressed.

 

[JimMarn]

If new stuff was never looked at, we would still be wondering if that thing called fire was worth it or not.

Not that I'm saying odd space drives will work.

edit:

I just noticed I'm now SOC-13. When did that happen ? Sometimes when I log in here I'm not wide awake, so I have no clue when I went from 12 to 13.

 

[whulorigan]

I just noticed I'm now SOC-13. When did that happen ? Sometimes when I log in here I'm not wide awake, so I have no clue when I went from 12 to 13.

It happened when you hit 501 posts. It will go to SOC-14 when you hit 1001.

 

[Blue Ghost]

It it's too good to be true...

 

[JimMarn]

It happened when you hit 501 posts. It will go to SOC-14 when you hit 1001.

Okay, thanks. I didn't think I had done anything spiffy/outstanding.

 

[Timerover51]

As I see it, we have to try out all of the odd and off-beat ideas proposed, and keep poking at the Dean Drive, as you never know when something is actually going to work. Saying something is impossible does not make it so. Go back and read some of the comments by senior scientist and engineers at the end of World War 2, and see how many of those experts were wrong.

 

[aramis]

The US/NASA and Chinese experiments that showed thrust were carried out by real scientists, too. This is another attempt to falsify the results, with success (so to speak) this time. I think one experiment isn't enough to be conclusive.

Even they say they will have a real answer within the year.

Based upon the Ars Technica article...

They didn't use a model built to other model's specs; they built their own new model. That's bias 1.

Bias 2, they expected it to be magnetic field before building their test model.

Bias 3, they put an attenuator into the device, which is absent in all other test sets, save NASA's. They left theirs wired in; NASA's replaced the drive on the torsion arm for their attenuator test.

In short, they sabotaged their own credibility by NOT using one of the existing designs; they don't believe any of it, and so may have unintentionally built a non-working device, or may have compromised the device by the attenuator circuit.

Not lethally so, but it's clear that the Ars Technica writer doesn't trust their results, even tho' he doesn't believe the drive works at all himself.

No mention of unshielded chamber versus shielded chamber tests.
explicit mention of changing the nature of the internals from other drives - polished interiors versus the unpolished ones of the "working" ones.

Note also, Eagleworks did an inward-pointing test and an attenuator only test series, and got no significant thrust on attenuator alone, nor on the EM in. There was significant thrust in both perpendicular tests.

Until the actual paper is ready, detailing their methods (or lack thereof), given the number of published "thrust observed" results, theirs is the oultier the statistician gets to ignore outside a footnote.

 

[JimMarn]

As I see it, we have to try out all of the odd and off-beat ideas proposed, and keep poking at the Dean Drive, as you never know when something is actually going to work. Saying something is impossible does not make it so. Go back and read some of the comments by senior scientist and engineers at the end of World War 2, and see how many of those experts were wrong.

From the 1950s, I remember scientists, at least they claimed they were, stating that rockets would never reach outer space 'because there was nothing to push against'. The V-2 went outside the Earth's atmosphere.

And they apparently didn't know about Newton's Third Law, but I did at age 8.

My mother told me during all of this that when she was a kid, pre-WW2, her parents had bought her an encyclopedia set to help her in school.

The encyclopedia article claimed we would never get to the Earth's moon because it would take too long to get there.

What measurement did they use ? The speed of steam locomotives.

Or the statement by my high school geology teacher that plate techtonics was nonsense. This was after the IGY year showed the spreading apart of the Mid-Atlantic Ridge by plate movement.

 

[aramis]

It it's too good to be true...

The published data by the various science communities looks to be 1-2 mN per kW. That is low. Most ion drives are higher - 10-19 mN/kW.

The ONLY advantage the EM-Drive shows is that in mass. It has no fuel need. The drive itself is about half the mass of a similar sized ion drive, but 1/10 the thrust, so even there, it's only optimal for long duration use.

 

[Adam Dray]

It also has a weird Q curve. Basically, the faster you go, the worse the drive works. On the other hand, you can reverse it without flipping the ship.

I think they are claiming that the 2nd generation drives would be 10x more efficient in terms of mN/kW, but it's a vague and unsupported claim.