em drive

[birchoff]

There are already theories that don't break the laws of physics. We simply don't know yet if any of them corresponds to the EmDrive physics. I tried to sum up all proposed working principles for the EmDrive, the good ones and the bad:

• Radiation pressure: Roger Shawyer's explanation about radiation pressure due to different EM group velocities upon the two end reflectors of the tapered cavity seems to break conservation of momentum, even resorting to different frames of reference in special relativity.

• Lorentz force imbalance: Juan Yang at NWPU and Guido Fetta at Cannae LLC both refer to a Lorentz force imbalance acting on the lectron trajectories upon the two end reflectors of the cavity, using classical electromagnetism. Same breaking of the laws of conservation of momentum.

• Quantum vacuum virtual plasma: Harold "Sonny" White at NASA has a conjecture about Quantum Vacuum Fluctuations (QVF). He thinks the virtual particles that pop in and out of the vacuum state can be treated as a real plasma. So he tries to impart momentum on this virtual plasma using magnetohydrodynamics (MHD) i.e. a Lorentz force produced by crossed electric and magnetic fields that accelerates electrically conducting fluids. So White's Q-thruster is like an electromagnetic plasma thruster, except the propellant that is pushed back is a virtual plasma created from the vacuum by quantum fluctuations. The fact that momentum could be imparted to virtual particles is not proved and quite dubious though. The model predicts a force output scaling proportional to the E-field strength to the fourth power (V^4).

• Scalar-tensor theory: Fernando Minotti from CONICET explains that a scalar-tensor theory of gravity, of the Brans-Dicke type (proposed by Mbelek & Lachièze-Rey) would account for the thrust produced by RF resonant tapered cavities. Within this S-T theory, the thrust is the result of the gravitational force on the cavity walls. The metric tensor has a negative effective source. With the different EM resonant modes (TE or TM) in the cavity, the corresponding total effective source is zero, with differentiated regions where it is either positive or negative (the latter should thus be located as close as possible to the walls). Moreover this theory is compatible with an increased thrust due to the presence of a dielectric resonator inside of the cavity near an end reflector, which would distort the source distribution in the right direction. The effective source is proportional to the time average of B^2 – (E/c)^2
  S-T theory is easily falsifiable in the lab:
  - First, for fixed EM resonant mode and power, but different operating resonant frequencies, thrust could be higher with certain lower frequencies, and thrust should reverse for other frequencies. Those special frequencies can be precisely calculated, from cavity dimensions.
  - Second, still for fixed EM resonant mode and power, the thrust should increase with the mass of the cavity. One does not even have to change the cavity, but simply wrap it with a layer of some heavy material.

• Mach effect: James Woodward at CSUF has integrated Sciama's work about Mach's principle and Wheeler-Feynman "action at a distance" theory within the framework of General Relativity, that led to the description of relativistic Mach effects. This work led to experimental testing of propellantless Mach Effect Thrusters (MET) and a theoretical development involving Transient Mass Equation (TME). The TME could explain why an RF resonant tapered cavity like the EmDrive, with a dielectric material inside, would produce thrust when the dielectric increases its internal energy, storing energy from the microwaves. It could also explain why such a version of the same cavity lacking its internal dielectric would still produce a (smaller) thrust, due to the metal of the cavity walls which is weakly electrostrictive. The model predicts a force output scaling to the second power (quadratic).

under the assumption that the effects measured in the lab are real.

I hope ME ends up being the winning explaination.

[williatw]

10 questions about Nasa's 'impossible' space drive answered


A superconducting version of the EmDrive, would, in principle, generate thousands of times more thrust.

Here we answer many of your questions, quibbles and criticisms.

1. Isn't such a tiny force likely to be experimental error?

The equipment can measure forces of less than ten micronewtons, and the thrust was several times that high.

The test rig is carefully designed to remove any possible sources of error. Even the lapping of waves in the Gulf of Mexico 25 miles away every three to four seconds would have showed up on the sensors, so the apparatus was floated pneumatically to avoid any influence. The apparatus is completely sealed, with power and signals going through liquid metal contacts to prevent any force being transmitted through cables.

Similar consideration was given to any other possible factors that could influence the result, for example shielding everything from electromagnetic effects. There may be a gap somewhere, but the Nasa experimenters appear to have been scrupulous.

2. Thrust was also measured from the 'Null Drive', doesn't that mean the experiment failed?

Lots of commenters jumped on this, assuming incorrectly that this was a control test and that thrust was measured when there was no drive.

In fact, the 'Null Drive' was a modified version of the Cannae Drive, a flying-saucer-shaped device with slots engraved in one face only. The underlying theory is that the slots create a force imbalance in resonating microwaves; the 'Null Drive' was unslotted, but still produced thrust when filled with microwaves. This may challenge the theory -- it is probably no coincidence that Cannae inventor Guido Fetta is patenting a new version which works differently -- but not the results.

The true 'null test' was when a load was used with no resonant cavity, and as expected this produced no thrust:

"Finally, a 50 ohm RF resistive load was used in place of the test article to verify no significant systemic effects that would cause apparent or real torsion pendulum displacements. The RF load was energised twice at an amplifier output power of approximately 28 watts and no significant pendulum arm displacements were observed."

Equally significantly, reversing the orientation of the drive reversed the thrust.

3. They didn't do it in a vacuum, so how do we know the result is valid in space?

While the original abstract says that tests were run "within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure", the full report describes tests in which turbo vacuum pumps were used to evacuate the test chamber to a pressure of five millionths of a Torr, or about a hundred-millionth of normal atmospheric pressure.

4. Why didn't they test Shawyer's EmDrive design as well as the Cannae drive?

It turns out that in January this year they did test the EmDrive design.

The test results for this were also positive, and in fact their tapered-cavity drive, derived from the Chinese drive which is in turn based on Shawyer's EmDrive, produced 91 micronewtons of thrust for 17 watts of power, compared to the 40 micronewtons of thrust from 28 watts for the Cannae drive.

5. Even if it works, how can such a small thrust push a spacecraft?

The thrust was low because this is a very low-powered apparatus. The Chinese have demonstrated a system using kilowatts rather than watts of power that produces a push of 720 millinewtons. This is enough to lift a couple of ounces, making it competitive with modern space drives. The difference is that this drive doesn't require any propellant, which usually takes up a lot of launch weight and places a limit on how long other drives can operate for.

The Nasa paper says "the expected thrust to power for initial flight applications is expected to be in the 0.4 newton per kilowatt electric (N/kWe) range, which is about seven times higher than the current state of the art Hall thruster in use on orbit today."

6. How does this get us to Mars?

The small but steady push of the EmDrive is a winner for space missions, gradually accelerating spacecraft to high speed.

The Nasa paper projects a 'conservative' manned mission to Mars from Earth orbit, with a 90-ton spacecraft driven by the new technology. Using a 2-megawatt nuclear power source, it can develop 800 newtons (180 pounds) of thrust. The entire mission would take eight months, including a 70-day stay on Mars.

This compares with Nasa's plans using conventional technology which takes six months just to get there, and requires several hundred tons to be put into Earth's orbit to start with. You also have to stay there for at least 18 months while you wait for the planets to align again for the journey back. The new drive provides enough thrust to overcome the gravitational attraction of the Sun at these distances, which makes manoeuvring much easier.


A less conservative projection has an advanced drive developing ten times as much thrust for the same power -- this cuts the transit time to Mars to 28 days, and can generally fly around the solar system at will, a true Nasa dream machine.

7. What's this about hoverboards and flying cars?

A superconducting version of the EmDrive, would, in principle, generate thousands of times more thrust. And because it does not require energy just to hold things up (just as a chair does not require power to keep you off the ground), in theory you could have a hoverboard which does not require energy to float in the air.

You'll have to provide the lateral thrust yourself though, or expend energy pushing the thing along by other means --- and in any case, superconducting electronics are rather bulky and expensive, so the super-EmDrive is likely to be a few years away.

8. Surely a single result by one lab is likely to be an error?
The Nasa work builds on previous results by Roger Shawyer in Britain and Prof Yang Juan at Northwestern Polytechnical University in Xi'an as well as Guido Fetta's work at Cannae. This is more of a confirmation.

9. Why isn't there a simple explanation of how it's supposed to work without violating the laws of physics?

Different research groups all seem to have their own theories -- Shawyer's is based on relativity, the Chinese one is based on Maxwell's Law and Nasa is now talking about pushing against "quantum vacuum virtual particles" and saying that this is "similar to the way a naval submarine interacts with the water which surrounds it." The Nasa report deliberately avoids any theoretical discussion on this point, with good reason.

None of these explanations has gone unchallenged by theoreticians, and it might be fair to say that there is no accepted explanation as to how a close system of resonating microwaves can produce a thrust. There is no accepted theoretical explanation of how high-temperature superconductors work either, but because the effect has been replicated so many times, nobody doubts that it happens.

If the new drive results continue to be replicated, then theory may have to catch up.

10. What happens next?

The next stage will be more tests and more validation. An improved version of the tapered drive based on the EmDrive has been designed, and this will be built and sent out to other facilities so they can confirm the initials results.

The current plan is for IV&V (Independent Verification and Validation) tests at the Glenn Research Center using their low thrust torsion pendulum, similar to the one used, followed by another one at the Jet Propulsion Laboratory (JPL) using their low thrust torsion pendulum. The Johns Hopkins University Applied Physics Laboratory may also test the device using a different type of apparatus known as a Cavendish balance.

After that, the sky's the limit. Or perhaps it isn't.

http://www.wired.co.uk/news/archive/201 ... ible-drive

[GIThruster]

That's an interesting wish list but do remember that each of these permutations have different impedances and therefore require different power systems or at least specific adaptations of any given power system. These things are not plug and play.

Agreed, but the data collected from the entirety should provide enough information to either start informing a coherent theory or help find the experimental protocol error.

Yes, it's extremely useful to be able to change one significant variable such as the permittivity of the cavity and do a parametric study. Same with voltage. As with the Mach Effect Thrusters, it would be very difficult to change the frequency so that's not really practical, but changing the geometry slightly and doing further tests especially when you can use the same or similar power conditioning, is very very useful. I have little doubt we'll see someone get to the bottom of this within a couple years so long as it remains funded, which at this point looks like what's in the works.

[GIThruster]

10 questions about Nasa's 'impossible' space drive answered
http://www.wired.co.uk/news/archive/201 ... ible-drive

Nicely laid out. Shame it doesn't really look more carefully at the MET explanation.

I would just note however, that this needs high frequency and we don't have any UHF nor microwave superconductors that I'm aware of. I stopped looking for superconducting power system components for MET's about 6 years ago because everything seems to be HF or VHF at best.

[GIThruster]

There are already theories that don't break the laws of physics. We simply don't know yet if any of them corresponds to the EmDrive physics. I tried to sum up all proposed working principles for the EmDrive, the good ones and the bad:

• Radiation pressure: Roger Shawyer's explanation about radiation pressure due to different EM group velocities upon the two end reflectors of the tapered cavity seems to break conservation of momentum, even resorting to different frames of reference in special relativity.

• Lorentz force imbalance: Juan Yang at NWPU and Guido Fetta at Cannae LLC both refer to a Lorentz force imbalance acting on the lectron trajectories upon the two end reflectors of the cavity, using classical electromagnetism. Same breaking of the laws of conservation of momentum.

• Quantum vacuum virtual plasma: Harold "Sonny" White at NASA has a conjecture about Quantum Vacuum Fluctuations (QVF). He thinks the virtual particles that pop in and out of the vacuum state can be treated as a real plasma. So he tries to impart momentum on this virtual plasma using magnetohydrodynamics (MHD) i.e. a Lorentz force produced by crossed electric and magnetic fields that accelerates electrically conducting fluids. So White's Q-thruster is like an electromagnetic plasma thruster, except the propellant that is pushed back is a virtual plasma created from the vacuum by quantum fluctuations. The fact that momentum could be imparted to virtual particles is not proved and quite dubious though. The model predicts a force output scaling proportional to the E-field strength to the fourth power (V^4).

• Scalar-tensor theory: Fernando Minotti from CONICET explains that a scalar-tensor theory of gravity, of the Brans-Dicke type (proposed by Mbelek & Lachièze-Rey) would account for the thrust produced by RF resonant tapered cavities. Within this S-T theory, the thrust is the result of the gravitational force on the cavity walls. The metric tensor has a negative effective source. With the different EM resonant modes (TE or TM) in the cavity, the corresponding total effective source is zero, with differentiated regions where it is either positive or negative (the latter should thus be located as close as possible to the walls). Moreover this theory is compatible with an increased thrust due to the presence of a dielectric resonator inside of the cavity near an end reflector, which would distort the source distribution in the right direction. The effective source is proportional to the time average of B^2 – (E/c)^2
  S-T theory is easily falsifiable in the lab:
  - First, for fixed EM resonant mode and power, but different operating resonant frequencies, thrust could be higher with certain lower frequencies, and thrust should reverse for other frequencies. Those special frequencies can be precisely calculated, from cavity dimensions.
  - Second, still for fixed EM resonant mode and power, the thrust should increase with the mass of the cavity. One does not even have to change the cavity, but simply wrap it with a layer of some heavy material.

• Mach effect: James Woodward at CSUF has integrated Sciama's work about Mach's principle and Wheeler-Feynman "action at a distance" theory within the framework of General Relativity, that led to the description of relativistic Mach effects. This work led to experimental testing of propellantless Mach Effect Thrusters (MET) and a theoretical development involving Transient Mass Equation (TME). The TME could explain why an RF resonant tapered cavity like the EmDrive, with a dielectric material inside, would produce thrust when the dielectric increases its internal energy, storing energy from the microwaves. It could also explain why such a version of the same cavity lacking its internal dielectric would still produce a (smaller) thrust, due to the metal of the cavity walls which is weakly electrostrictive. The model predicts a force output scaling to the second power (quadratic).

I'm impressed. This is very nicely done. I had not heard of the Scalar-tensor theory. I must own I am suspicious of scalar theories a la the Russians, because I investigated them some years ago and found all those I found to be frauds. The Russians have done quite a bit of scalar theory and most Westerners think it's all nonsense--twisting spacetime and whatnot--but who knows what this is without looking. I certainly plan to take a look as soon as I find time.

Thanks for this!

[RERT]

The gravitational behavior of antimatter is still unknown......

I read about experiments being set up to test that years ago. Not seeing a followup I presumed a 'null' result of antimatter acting exactly like normal matter to within the precision of the experiment.

I keep looking, but AEGIS has not yet reported. As of today the only outputs I can see are papers on the experimental setup.

[birchoff]

I don't know if anyone other than GiThruster is interested in Mach Effect Thrusters. but it looks like Woodward published a book explaining the theory in 2012. Bought it a few days ago since i read that the proceeds are being used to fund additional investigations. I must say while this is heavy on the theoretical justifications, using a fair amount of math it is not at all unreadable. Hell I plan on at least finishing my first read this weekend. According to the forward the book is not necessarily written for scientists or engineers, but for an "educated audience who has an interest in science and technology."

edit: forgot to include a link to the book see here

[Carl White]

I have a copy of the book as well.

It's divided into three sections. The first addresses the underlying physics and the second past and current experiments. The "central theme" of the third is "the creation of an effective Jupiter mass of exotic matter in a structure with typical dimensions of meters" and involves the ADM electron model.

I found the note in the foreword about QI (quantum inequalities) to be a little discouraging though.

[williatw]

The "central theme" of the third is "the creation of an effective Jupiter mass of exotic matter in a structure with typical dimensions of meters" and involves the ADM electron model.

I found the note in the foreword about QI (quantum inequalities) to be a little discouraging though.

Setting aside Sonny White's as yet untested hypothesis of being able to get by with only a Voyager Space probe mass of "exotic matter" for hypothetical warp drive, how does one create exotic matter, and what exactly is it supposed to be? Just me guessing how to make it I would assume to make significant amouts of you would need some kind of high energy particle accelerator collisions...similar to how anti-protons are made. Of course if one had cheap access to space, you could build/orbit a large linear particle accelerator, maybe one dozens or even hundreds of miles long; you could get some really insane high energy collisions then.

[tokamac]

how does one create exotic matter, and what exactly is it supposed to be?

"Exotic matter" is simply matter with negative mass and energy. We don't observe it in nature. It hasn't been created in lab, for example within particle accelerators.

First theoretical possibility to create exotic matter (or exotic energy density): Three things related and combined: Mach effect, Transient Mass Equation (TME), negative bare mass ADM model of the electron.

According to Jim Woodward, the TME allows to fluctuate the mass of a material storing energy (for example the dielectric of a capacitor submitted to a varying electric power) and undergoing a proper acceleration. This is a relativistic Mach effect. Quoting the article Woodward effect on wikipedia about the TME:

• The first, linear term (of the TME) is called the "impulse engine" term because it expresses mass fluctuation depending on the derivative of the power, and scales linearly with the frequency. Past and current experiments about Mach effects thrusters are designed to demonstrate thrust and the control of one type of Mach effect.
• The second, quadratic term (of the TME) is what Woodward calls the "wormhole" term, because it is always negative. Although this term appears to be many orders of magnitude weaker than the first term, which makes it usually negligible, theoretically, the second term's effect could become huge in some circumstances. The second term, the wormhole term, is indeed driven by the first impulse engine term, which fluctuates mass by around plus or minus the rest mass value. When fluctuations reach a very high amplitude and mass density is driven very close to zero, the equation shows that mass should achieve very large negative values very quickly, with a strong non-linear behavior. In this regard, the Woodward effect could generate exotic matter, although this still remains very speculative due to the lack of any available experiment that would highlight such an effect.

The transient mass fluctuation would express the negative bare mass of the electron, according to the ADM model.

If you want to learn more about Mach effects applied to propulsion and wormholes, wikipedia is limited. You'd have to read Woodward's book: Making Starships and Stargates: The Science of Interstellar Transport and Absurdly Benign Wormholes (Springer 2012).

Second possibility: Another recent explanation could be the negative effective source of the metric tensor in some Brans-Dicke scalar-tensor (ST) theory, as proposed by Fernando Minotti after the work of Marc Lachèze-Rey and Jean Paul Mbelek. ST would provide negative energy densities in RF asymmetric resonant cavities like the EmDrive. Depending on the TE or TM resonant EM mode used, some regions inside the cavity would have a positive gravitational field and others would have a negative gravitational field (while the corresponding total effective source is exactly zero). You can call that exotic energy, antigravity, dark energy…
Scalar-tensor theories and asymmetric resonant cavities

[Diogenes]

John C. Baez, a mathematical physicist at the University of California at Riverside, calls the experiment “graduate-level baloney.” He scoffs at the idea that microwaves in a “fancy-shaped can” could violate the law of conservation of momentum.

They keep saying that it does, and they never seem to consider the possibility that it doesn't. It's my understanding that it is the Higgs Boson and Higgs Field which gives everything mass. Perhaps this is directly manipulating the Higgs field?



I am reminded of when Einstein came out, everyone bitched that his theories violated the Aether theory.

[Diogenes]

And here is another one.



NASA’s “Impossible” Engine Actually Worked

People have been flipping their lids over a supposed “impossible engine” design, or EmDrive. Invented by British scientist Roger Shawyer, the engine is supposedly capable of generating thrust without any sort of propellant. Two independent tests have already confirmed different models work, and folks in the scientific community are cautiously becoming hopeful this technology could change space travel forever. The problem: it goes against a law of physics known as conservation of momentum, which states that every action must have an equal and opposite reaction.

http://www.technobuffalo.com/2014/08/09 ... ly-worked/

[Aero]

Reading up on the Casimir effect I came across a field named stochastic electrodynamics. It seems to be a disputed area like the EM Drive but also might be pertinent. http://en.wikipedia.org/wiki/Stochastic_electrodynamics

I was reading up on the Casimir effect because I wonder what happens to the Casimir force when the vacuum fluctuations between plates are swamped by high power coherent RF energy in a resonate cavity. I did discover that the shape of the surfaces are important and there have very recently been development of numerical solutions for the Casimir force for irregularly shaped surfaces. Of course the Wikipedia reference led to a pay wall.

Back to the EM Drive, it seems to me that the resonating RF signal in the cavity could overpower the zero point electromagnetic fluctuation at (and maybe near) the resonate frequency. So how does the vacuum energy field behave when one of its random frequencies is removed. I don't know.

[birchoff]

Excuse you, but don't lecture me about my assumptions while you're busy making assumptions. You sound ridiculous.

I don't have any need to present arguments nor evidence that comes to what you are proposing is the proper standard. When I say for example, that Sonny and Paul built a Shawyer resonator and hung it from a 2 meter penduluum in the garage, I am speaking from experience. I have known these two for almost a decade, and was appraised of their work when it was in progress, from the time before they approached Gary for funds until the day he cut them off for lack of results. There is no intellectual duty to the truth that forces me to pander to your ignorance on these issues, and I am not going to spend ANY time researching for evidence for you. Do it yourself.

The Shawyer work was paid for by the Brits for many years without reasonable results. In fact, the work was not even provided proper scientific controls. After years of serious support, the Brits had had enough and dropped the program. WHILE ALL THIS WAS GOING ON, from a time BEFORE THE FUNDS FOR THAT PROGRAM ARRIVED, all sensible people argued that Shawyer was an engineer, not a physicist, and that he did not understand what the concept of "group velocity" entails, and that what he was proposing was based upon his faulty understanding and which led to an obvious violation of conservation. All this is true, but those arguments are NOT why the Shawyer work was defunded in Britain. It was defunded because it failed to produce results, just as the replication done by Sonny and Paul (my mentor) failed to produce results.

Although I have not wasted my time on the recent stuff from China, I would note to you that they have had funding for this for several years now, and until lately, their reports were not of positive test results. Why they should suddenly have positive test results is beyond me, but I do know its not because Shawyer is right, because we know he is not, and it is not because Sonny is right, because we know he is not. If they're getting significant results in China, and at JSC, it is not the result of good science, because good science does not violate conservation (Shawyer's explanation) nor Einstein's Equivalence Principle (Sonny's explanation).

My belief is, this is all just another continuing counter-intel con game. It's noteworthy that it arrived exactly at the point where Sonny was scrambling for funding. Sonny was funded until September and until very recently, the story was that unless they could both get additional funding for Eagle, and produce the 0.4N/kWe thrust to power efficiency they had promised, they would close shop by October 1. Now suddenly despite they have not made their thrust efficiency goals, they have funding through June 2015. And this magically appearing funding is likely in no small portion the result of these supposed "findings" in China.

Just use a little common sense. The Chinese don't release test results without a purpose. In this instance, it seems to me completely likely, their purpose is to throw one of the CIA's barbs back in their faces, and it seems it worked! And seriously, if you don't know how these things happen and go on year after year, don't post some childish note telling me you're upset for my assumptions. My judgements are based on as much an insider's knowledge as is possible without being an insider. One thing you can count on--none of this is what it seems. This is how the CIA and places like China do their daily duty to their countries--through misinformation counterintelligence scams. The outcome is, that Eagle has funding for another year, and it looks like NASA Glenn is going to replicate their work. So we'll see what we see, after a few million more dollars. Trouble is, we ought to be spending those dollars on something that has a chance to work like M-E physics, rather than on this.

I wanted to point this out that I found some corroboration to what you were saying about Sonny's previous research on the EmDrive In Jim's book. As for why the funding was pulled though according to Woodward his documented perspective is that it was largely a result of the Recession. Which gave me the impression that even though they weren't getting results they probably would have gotten more money to continue to figure stuff out if the recession didnt happen.

[GIThruster]

Actually, the funding of Sonny and Paul's early Shawyer resonator work was not "pulled" per se. It ran its course and ended. They had appealed to Gary Hudson for funding and their project ran its course. During the attempt what they realized was they were unable to pull the kind of vacuum necessary, because the copper was vaporizing and allowing corona discharges, and this mitigated against the proper function of the cavity. They could have built a second cavity out of something like stainless steel, but Gary had already spent a great deal and is not an especially wealthy guy. He wasn't able to afford continuing support of the project. Of course though, DARPA and NASA are able to afford such continuing support and this is what Eagleworks is all about. Sonny had originally wanted to pursue the Shawyer and QThruster (MLT) designs but NASA decided they wanted answers about Sonny's QVF model and the warp interferometry experiment, so they directed Eagleworks to pursue that first. This is why Eagle has in some senses, taken as long as they have to get around to focusing on the thrusters, which they've been doing now for a couple years.

Word is, NASA Glenn and NASA JPL may both be looking into this in the future so we may see some answers in the next couple years. For now, I don't think either center even has a balance in service so it will be some time after they decide to move in this direction. Glenn may already be doing so. I don't really know. What I do know, is that none of these centers are pursuing M-E work, because Sonny considers it in competition with his model and is not looking to test Jim's theory. NASA and DARPA are not currently paying for this but of course, these things can change.