German Test Reveals That Magnetic Fields Are Pushing the EM Drive (arstechnica.com)

"Researchers in Germany have performed an independent, controlled test of the infamous EM Drive with an unprecedented level of precision," writes PvtVoid. "The result? The thrust is coming from interactions with the Earth's magnetic field." From the report: Instead of getting ahold of someone else's EM drive, or Mach-effect device, the researchers created their own, along with the driving electronics. The researchers used precision machining and polishing to obtain a microwave cavity that was much better than those previously published. If anything was going to work, this would be the one. The researchers built up a very nice driving circuit that was capable of supplying 50W of power to the cavity. However, the amplifier mountings still needed to be worked on. So, to keep thermal management problems under control, they limited themselves to a couple of Watts in the current tests. The researchers also inserted an enormous attenuator. This meant that they could, without physically changing the setup, switch on all the electronics and have the amplifiers working at full noise, and all the power would either go to the EM drive or be absorbed in the attenuator. That gives them much more freedom to determine if the thrust was coming from the drive or not.

Even with a power of just a couple of Watts, the EM-drive generates thrust in the expected direction (e.g., the torsion bar twists in the right direction). If you reverse the direction of the thruster, the balance swings back the other way: the thrust is reversed. Unfortunately, the EM drive also generates the thrust when the thruster is directed so that it cannot produce a torque on the balance (e.g., the null test also produces thrust). And likewise, that "thrust" reverses when you reverse the direction of the thruster. The best part is that the results are the same when the attenuator is put into the circuit. In this case, there is basically no radiation in the microwave cavity, yet the WTF-thruster thrusts on. So, where does the force come from? The Earth's magnetic field, most likely. The cables that carry the current to the microwave amplifier run along the arm of the torsion bar. Although the cable is shielded, it is not perfect (because the researchers did not have enough mu metal). The current in the cable experiences a force due to the Earth's magnetic field that is precisely perpendicular to the torsion bar. And, depending on the orientation of the thruster, the direction of the current will reverse and the force will reverse. The researchers' conclude by saying: "At least, SpaceDrive [the name of the test setup] is an excellent educational project by developing highly demanding test setups, evaluating theoretical models and possible experimental errors. It's a great learning experience with the possibility to find something that can drive space exploration into its next generation."

Comments

THIS is science

[Anonymous Coward]

This is what we should be teaching in schools and promoting in daily life/culture.

Re:THIS is science

[famebait]

Dear Gods, not again. Can we please just kill this thing once and for all?

*"Vegetable" is not a botanical category.*

"Vegetable" is a culinary term.
All vegetables are some part of a plant.
Botany always has a specific name for that part, but that does not exclude them from vegetables,
Salad does not cease to be vegetable for being botanically leaves or buds.
Celery does not cease to be a vegetable for being botanically a leaf stalk.
Artichoke does not cease to be a vegetable for being botanically a flower.
Carrot does not cease to be a vegetable for being botanically a root.
Tomato does not cease to be a vegetable for being botanically a fruit. Nor do squash, peppers, eggplant, cucumber, okra, avocado, or any number of others.

"Vegetable" refers to basically any part of a plant used for food, except those commonly placed firmly in more specific categories. One of those more specific categories is "fruit" (in the culinary sense), which usually requires it to be sweet and/or tart and used substantially for those qualities.
Some of the others are grain (usually botanically fruit before threshing), nuts (always botanically fruit), spices (includes a number of fruits botanically speaking), and herbs.

Culinary terms are made for utility in cooking, not for classification of plants - for that we have botany.
Thus the distinctions are inherently vague:

How big or mild-flavored does a leaf have to be to move from herb to vegetable?
At what size, mildness, or degree of dessication does a chili move from vegetable to spice?
How sweet would a plantain have to be to leave the vegtable section and move in with the banana?
Is it not fair to look for sugar cane and rhubarb in the fruit section, even though botanically they are not?
Is the sweet potato with the vegetables bacause it is a root or because of its usage? Or maybe in your shop it is not?

Thrust is coming from interactions with the Earth

[Camel Pilot]

No problem... we will just have to take the Earth with us.

Here Is A Link To The Actual Report

[careysub]

It was presented at the Space Propulsion 2018 conference.

Re:Thrust is coming from interactions with the Ear

[Michael Woodhams]

Once you've taken an EM drive and removed the useless cavity and microwave emitter, what you are left with is an electrodynamic tether which may indeed be useful, but doesn't owe anything to the EM drive.

Re:Satellites

[Michael Woodhams]

Yes, it can be, and that system is called an electrodynamic tether, and it doesn't make use of the microwave cavity which is at the heart of the EM drive (which, according to this latest experiment, wasn't doing anything in the first place.)

Not "case closed" yet...

[Anonymous Coward]

..If the folks over at nasaspaceflight are to be believed

Looks like the setup was very sloppy indeed.. with the wattage too low making any signal disappear into noise..

Quoting:

Looking at the pictures of Tajmar's experiment, no wonder they are seeing nothing but Lorentz. First of all their twisted pairs do not appear to be twisted enough. There should be at least two twists per inch. In the image below it appears that there is maybe one twist per two inches or so. And then look at the location of the main amplifier and the length of the main leads! :o

At only 2W of RF power, no wonder they are only seeing Lorentz. It's almost like they designed their experiment to be susceptible to this form of error.

Legacy of GM and Rolls Royce.

[Ungrounded Lightning]

The researchers used precision machining and polishing to obtain a microwave cavity that was much better than those previously published. If anything was going to work, this would be the one.

Now that reminds me of a story, back in my programming-for-the-auto-industry days.

Seems that Rolls Royce, after sticking with manual transmissions for a long time, decided to consider manufacturing a car with an automatic transmission. So they got hold of the best on the hoi polloi market - the GM 350 turbo-hydramatic - to use as a reference.

First they tested the heck out of it - and found it did exactly what an auto-tranny should. So how could they make something better? So they tore it down to see if there was anything they could improve. But everything was beautifully designed and machined. Except for one surface on one part, which was a little rough.

So they machined it smooth and reassembled the transmission. And it didn't work at all. That surface was SUPPOSED to be a little rough. B-)

- - - -

Now personally, as much as I'd like to see a working reactionless electronic thruster, I'm not holding my breath waiting for a violation of the law of conservation of momentum. But it would be nice if something DID show up that worked.