Emdrive could be mainly magnetic effects but there is still more testing to be done

A few days ago Nextbigfuture reported that a research group TU Dresden in Germany led by Martin Tajmar, is finding more magnetic interaction from cables. He is not conclusively saying that is all that is happening with EMdrive or Mach Effect but he thinks it is a significant error source for such tiny thrust measurements.

New Scientist is indicating that the Tajmar EMdrive results look bad for EMDrive.

The team built their EM drive with the same dimensions as the one that NASA tested, and placed it in a vacuum chamber. Then, they piped microwaves into the cavity and measured its tiny movements using lasers. As in previous tests, they found it produced thrust, as measured by a spring. But when positioned so that the microwaves could not possibly produce thrust in the direction of the spring, the drive seemed to push just as hard.

And, when the team cut the power by half, it barely affected the thrust. So, it seems there’s something else at work. The researchers say the thrust may be produced by an interaction between Earth’s magnetic field and the cables that power the microwave amplifier.

Most of their setup was completely shielded from outside fields, but some of the cables did not fit inside the box and there may have been a few centimeters left unshielded, Tajmar says. The current running through those unprotected cables could interact with a magnetic field to push the EM drive forward. When they calculated the strength of this effect, they found that it could produce a few micro-Newtons of thrust. The thrust that they measured from the EM drive was 4 micro-Newtons.

If the drive really is powered by magnetic fields instead of microwaves, it won’t be able to work in space, away from Earth’s magnetic field.

“This propellant-less propulsion business is regarded by those in the mainstream as speculative at best, and at worst it’s just serious nonsense and people are wasting their time,” says Jim Woodward. But he adds, “I don’t think this group is wasting their time. If there is a real effect, they’ll find it.”

Sonny White at Eagleworks (NASA) is scaling his EMDrive tests to 400 watts.

Jim Woodward has proposed Mach Effect propulsion.

Discussion at the NASA Spaceflight forum is criticizing the Tajmar experiment based on pictures of the test device.

User Monomorphic said

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!

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.

See picture above

Monomorphic is running this own tests-

I also avoided bundling the twisted pairs as that can lead to problems with the fields not cancelling out properly. Otherwise you have to use twisted pairs with different twist rates.

You can see in these images that my main power leads are one quarter or less the length of Tajmar and my twisted pairs are highly twisted.

I had 6.7A going to the centrally mounted amplifier yesterday and was not seeing these same problems.


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