EmDrive (again)

The Rocketry Forum

Help Support The Rocketry Forum:

Winston

Lorenzo von Matterhorn
Joined
Jan 31, 2009
Messages
9,415
Reaction score
1,548
"Martin Tajmar, the German scientist who has been independently testing the EM Drive, has a history of debunking experimental propulsion systems. So far, the drive appears to work, even in a vacuum. More testing is required to examine exactly how it works, and whether it is viable for use."

51st AIAA/SAE/ASEE Joint Propulsion Conference
27 Jul 15

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

The 'impossible' EmDrive could reach Pluto in 18 months
24 July 15

https://www.wired.co.uk/news/archive/2015-07/24/emdrive-space-drive-pluto-mission

Excerpt:

Last summer WIRED revealed that Nasa's Eagleworks Lab was testing a copy of the EmDrive, a propulsion device frequently labelled as "impossible" because it appears to violate the law of conservation of momentum. Against all expectation they found it produced thrust. The response from the scientific community was dramatic, and generally sceptical -- but the "anomalous thrust" stubbornly refuses to disappear as more research zeroes in on it.

The situation is not helped by garbled media reports like "British scientist who says he's found the secret of Star Trek's 'warp speed'". But the subject is attracting serious examination from scientists who want to know if a sealed cavity filled with resonating microwaves can really produce net thrust. Previously the effect has been measured by British scientist Roger Shawyer, who invented the EmDrive, and a Chinese team, as well as Nasa.

Martin Tajmar, professor and chair for Space Systems at the Dresden University of Technology, is perhaps uniquely well qualified to evaluate the EmDrive. His research interests include "Breakthrough Propulsion Physics," space drives which do not rely on the variations on rocket thrust but which draw on more exotic science.

The obvious sources of error -- air currents, leaking microwaves, ionisation -- have long ago been ruled out. But this is the first time that someone with a well-equipped lab and a strong background in tracking experimental error has been involved, rather than engineers who may be unconsciously influenced by a desire to see it work.

Tajmar will be presenting his results at the American Institute for Aeronautics and Astronautics' Propulsion and Energy Forum and Exposition in Orlando on 27 July, in a paper called "Direct Thrust Measurements of an EmDrive and Evaluation of Possible Side-Effects". By side-effects, he is referring to the electric and magnetic fields that may cause false readings.

Tajmar prefers his results not to be shared in advance, but told WIRED that his paper will not close the EmDrive story and that it merits further research.

Roger Shawyer is encouraged by Tajmar's work, which he says validates his own theoretical predictions as well as his experimental results. Shawyer has often been dismissed because of his own lack of peer-reviewed scientific publications. That looks to be changing very soon; a paper Shawyer presented at the International Astronautical Conference in Toronto in 2014 is in the final stages for peer-review for publication. This describes an advanced EmDrive-powered spaceplane.
 

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
267
Tajmar's team is reporting that their test results neither refute or confirm the claims for the device.

-- Roger
 

cerving

Owner, Eggtimer Rocketry
TRF Sponsor
TRF Supporter
Joined
Feb 3, 2012
Messages
4,308
Reaction score
1,642
Why don't they just put one out there (they could toss it from the ISS) and see if it goes anywhere?
 

aerostadt

Lifetime Supporter
TRF Lifetime Supporter
Joined
Oct 27, 2009
Messages
3,439
Reaction score
333
Location
Brigham City, UT
Why don't they just put one out there (they could toss it from the ISS) and see if it goes anywhere?
I think there are plans to do this. The Chinese and the the Americans are interested in this device. I think the Chinese are planning to test it space.
 
Last edited:

Winston

Lorenzo von Matterhorn
Joined
Jan 31, 2009
Messages
9,415
Reaction score
1,548
In the article, less definitive than "death":

In major international tests, the physics-defying EmDrive has failed to produce the amount of thrust proponents were expecting. In fact, in one test at Germany’s Dresden University, it didn’t produce any thrust at all. Is this the end of the line for EmDrive?

Still, several research groups, including NASA’s Eagleworks (formally known as the Advanced Physics Propulsion Laboratory, set up to explore new technologies) and DARPA, the Defense Department’s research projects agency, have continued exploring the viability of the EmDrive.

Why? Because the concept could “transform space travel and see craft lifting silently off from launchpads and reaching beyond the solar system,” Mike McCulloch, a lecturer in geomatics at the University of Plymouth, U.K., and leader behind DARPA’s EmDrive project, told Pop Mech last year. “We can also get an unmanned probe to Proxima Centauri in a (long) human lifetime, 90 years.”

The crux of the EmDrive is if you bounce microwaves around inside the tube, they exert more force in one direction than the other, creating a net thrust without the need for any propellant. And when NASA and a team at Xi’an in China tried this, they actually got a small-but-distinct net force.

Now, however, physicists at the Dresden University of Technology (TU Dresden) are saying those promising results showing thrust were all false positives that are explained by outside forces.

Interested parties have described the tests as EmDrive’s “do-or-die” moment, and it seems like the outcome points to die—for now.
 

Marc_G

Well-Known Member
Joined
Jun 6, 2010
Messages
6,923
Reaction score
937
Location
Indianapolis Metro Area
Like any good scifi or horror film, just when you think it's dead, there's the possibility of new life. It's not dead, as long as we remember it.
 

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
267
Another nail in its coffin. The "thrust" was due to heat affecting the measuring device:

 

Funkworks

Well-Known Member
Joined
Jul 28, 2018
Messages
1,408
Reaction score
1,003
The crux of the EmDrive is if you bounce microwaves around inside the tube, they exert more force in one direction than the other, creating a net thrust without the need for any propellant.
Despite being propelled by 120 Volts AC many times a week, my microwave oven is still exactly where it was set years ago.

Here’s what radiative propulsion “without the need for any propellant” really looks like:
 

Reinhard

Well-Known Member
TRF Supporter
Joined
Jan 18, 2009
Messages
1,150
Reaction score
358
Location
Austria
Another nail in its coffin. The "thrust" was due to heat affecting the measuring device:

This makes me wonder why the original team didn't find that out. If it is a thermal effect, there is a low-pass behavior between application of power and apparent generation of thrust. Maybe the data is buried in noise, but even then it might be possible to extract it by cycling the system often enough and to average the results. Similarly, a lock-in amplifier that modulates the power of the drive would also have shown now correlation between power an thrust. Maybe there are some characteristics of the setup that prevented the use of that - or they didn't bother to look.

Reinhard
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
5,149
Reaction score
2,436
Location
Melbourne Australia
Lots of teams have found this works to some degree and I find it interesting that they all would have missed the thermal effect. I know that all along people have been looking for thermal effects and kept coming up dry. Jury is still out IMHO.
 

Winston

Lorenzo von Matterhorn
Joined
Jan 31, 2009
Messages
9,415
Reaction score
1,548
Despite being propelled by 120 Volts AC many times a week, my microwave oven is still exactly where it was set years ago.

Here’s what radiative propulsion “without the need for any propellant” really looks like:
Just reporting the news. I'm a skeptic myself.
 

Funkworks

Well-Known Member
Joined
Jul 28, 2018
Messages
1,408
Reaction score
1,003
"When pilot-astronomer Mike Call arrived at a top-secret New England lab, he found a brilliant research team had seemingly repealed that basic law and produced a device with a device with one-way thrust."

All due respect to sci-fi stories and Mr. Stine, but "one-way thrust" would be like blowing a balloon and instead of forming an O-shape, it made D-shape.
:headspinning:
 
Top