Uncertain Propulsion Breakthroughs?

by Paul Gilster on December 30, 2016

Now that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers. Marc Millis, former head of NASA’s Breakthrough Propulsion Physics project and founding architect of the Tau Zero Foundation, has spent the last two months reviewing the relevant papers. Although he is the primary author of what follows, he has enlisted the help of scientists with expertise in experimental issues, all of whom also contributed to BPP, and all of whom remain active in experimental work. The revisions and insertions of George Hathaway (Hathaway Consulting), Martin Tajmar (Dresden University), Eric Davis (EarthTech) and Jordan Maclay (Quantum Fields, LLC) have been discussed through frequent email exchanges as the final text began to emerge. Next week I’ll also be presenting a supplemental report from George Hathaway. So is EmDrive new physics or the result of experimental error? The answer turns out to be surprisingly complex.

by Marc Millis, George Hathaway, Martin Tajmar, Eric Davis, & Jordan Maclay

It’s time to weigh in about the controversial EmDrive. I say, controversial, because of its profound implications if genuine, plus the lack of enough information with which to determine if it is genuine. A peer-reviewed article about experimental tests of an EmDrive was just published in the AIAA Journal of Propulsion and Power by Harold (Sonny) White and colleagues: White, H., March, P., Lawrence, J., Vera, J., Sylvester, A., Brady, D., & Bailey, P. (2016), “Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum,” Journal of Propulsion and Power, (print version pending, online version here.

That new article, plus related peer-reviewed articles, were reviewed by colleagues in our Tau Zero network, including two who operate similar low-thrust propulsion tests stands. From our reviews and discussions, I have reached the following professional opinions – summarized in the list below and then detailed in the body of this article. I regret that I can only offer opinions instead of definitive conclusions. That ambiguity is a significant part of this story that also merits discussion.



(1) The experimental methods and resulting data indicate a possible new force-producing effect, but not yet satisfying the threshold of “extraordinary evidence for extraordinary claims” – especially since this is a measurement of small effects.

(2) The propulsion physics explanations offered, which already assume that the measured force is real, are not sound.

(3) Experiments have been conducted on other anomalous forces, whose fidelity and implications merit comparable scrutiny, specifically Jim Woodward’s “Mach Effect Thruster.”


(1) If either the EmDrive or Mach Effect Thrusters are indeed genuine, then new physics is being discovered – the ramifications of which cannot be assessed until after those effects are sufficiently modeled. Even if it turns out that the effects are of minor utility, having new experimental approaches to explore unfinished physics would be valuable.

(2) Even if genuine, it is premature to assess the potential utility of these devices. Existing data only addresses some of the characteristics necessary to compare with other technologies. At this point, it is best to withhold judgment, either pro or con.

Pitfalls to Avoid

(1) The earlier repeated tactic, to attempt fast and cheap experimental tests, has turned out to be neither fast nor cheap. It’s been at least 14 years since the EmDrive first emerged (2002) and despite numerous tests, we still lack a definitive conclusion.

(2) In much the same way that thermal and chamber effects are obscuring the force measurements, our ability to reach accurate conclusions is impeded by our natural human behavior of jumping to conclusions, confirmation biases, sensationalism, and pedantic reflexes. This is part of the reality that also needs understanding so that we can separate those influences from the underlying physics.


(1) Continue scrutinizing the existing experimental investigations on both the EmDrive and Mach Effect Thrusters.

(2) To break the cycle of endlessly not doing the right things to get a definitive answer, begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts. The Tau Zero Foundation stands ready to make arrangements with suitable labs and analysts to produce reliable findings, pro or con.

(3) If it turns out that the effects are genuine, then continue with separate (a) engineering and (b) physics research, where the engineers focus on creating viable devices and the physicists focus on deciphering nature. In both cases:

  • Characterize the parameters that affect the effects.
  • Deduce mathematical models.
  • Apply those models to (a) assess scalability to practical levels, and (b) understand the new phenomena and its relation to other fundamental physics.
  • On all of the above, conduct and publish the research with a focus on the reliability of the findings rather than on their implications.


Pitfall 1 – The Fog of Want

Our decisions about this physics are influenced by behaviors that have nothing to do with physics. To ignore this human element would be a disservice to our readers. To get to the real story, we need to reveal that human element so that we can separate it from the rest of the data, like any good experiment. I’m starting off with this issue so that you are alert to its influences before you read the rest of this article.

As much as I strive to be impartial, I know I have an in-going negative bias on the EmDrive history. To create a review that reflects reality, rather than echoing my biases, I had to acknowledge and put aside my biases. Similarly, if you wish to extract the most from this article, you might want to check your perspectives. Ask yourself these three questions: (1) Do you already have an opinion about this effect and are now reading this article to see if we’ll confirm your expectation? (2) Do you want to know our conclusions without any regard to how we reached those conclusions? (3) Are you only interested in this EmDrive assessment, without regard to other comparable approaches?

If you answered “yes” to any of those questions, then you, like me, have natural human cognitive dysfunctions. To get past those reflexes, start by at least noticing that they exist. Then, take the time to notice both the pros and cons of the article, not just the parts you want to be true. Deciphering reality takes time instead of just listening to reflexive beliefs. It requires that one’s mind be open to the possibility you might be right and equally open to the possibility you might be wrong.

EmDrive History

This history is a recurring theme of incredible claims with non-credible evidence for those claims. In all cases, the effect is assumed to be real before the tests – which reflects a blinding bias. This dates back to at least 2002 when Roger Shawyer claimed to invent a device that “provides direct conversion from electrical energy to thrust, without expelling propellant.” I was still at NASA and vaguely remember reviewing it then. Regardless of the claims, the fidelity of the methods were below average. Over the years I heard about several other tests, but never saw any data. Eventually there was a press story about tests in China, along with this photo. It turns out that this photo is not a Chinese rig, but one of Shawyer’s:


Shawyer’s device and supporting equipment are on a rotating frame, where that rotation is used to determine if the device is thrusting. Note, however, the radiator and coolant lines. Any variation in the coolant flow would induce a torque that would obscure any real force measurements. Knowing the claimed thrusting effect is small and having enough experience to guess the likely variations in coolant flow, I considered this test set-up flawed.

Regarding the Chinese tests, I did not previously know they are described in peer-reviewed articles. Since many of us did not know either, I’m listing them here along with cursory impressions:

Juan, Y., et al, (2012). Net thrust measurement of propellantless microwave thrusters. Acta Physica Sinica, Chinese Physical Society.

Due to all of the impressions below, I do not have any confidence in their data:

  • Assumes first that the EmDrive is genuine.
  • Verbally describes theory, but without predicting experimental findings.
  • The experiment is not described in enough detail to assess its fidelity, but is similar to the one in the photo. Regardless, there is absolutely no discussion of possible influences on the rotation from tilting, power lead forces, vibration effects, thermal effects, or others.
  • The behavior of the thrust stand was not characterized before installing the EmDrive. Testing the two together without first having characterized the thrust stand separately prevents separating their distinct characteristics from the data.
  • The data plots lack error bands.

Juan, Y., et al (2013). Prediction and experimental measurement of the electromagnetic thrust generated by a microwave thruster system. Chinese Physics B, 22(5), 050301.

Due to all of the impressions below, I do not have any confidence in their data:

  • The description of the experiment is improved from the 2012 paper and appears to be the same configuration. This time possible effects from tilting and the power lead forces are mentioned, but they still do not address vibration, thermal, coolant loop, or other effects.
  • Again, they fail to characterize the thrust stand separately from the EmDrive.
  • Unlike the 2012 paper, they attempt to make numerical predictions. Details are provided for their physics derivations (which I did not scrutinize). That theory is then applied to make predictions for their specific hardware, but only verbally described it, rather than showing an explicit derivation. They show plots of the predicted force versus power, but only up to 200W, where the experimental runs span about 100W to 2400W.
  • The experimental results do not match their linear predictions for the ratio of force-to-power. These differences are then evasively dismissed.

Juan, Y., et al. (2016), “Thrust Measurement of an Independent Microwave Thruster Propulsion Device with Three-Wire Torsion Pendulum Thrust Measurement System,” Journal of Propulsion Technology, vol. 37, no. 2, pp 362-371.

The text is in Chinese, which I did not translate, but the figures and plots are captioned in English. Therefore I comment only on those diagrams. Again, what is shown is not enough to support claims of anomalous forces:

  • From figures 2, 3, 6, 7, 16, and 19, it appears the prior apparatus is now hung from torsion wires instead of a rotating support from below. This time the coolant loop is explicitly shown, but in a conceptual drawing instead of showing specifics. Again, the influence of the coolant loop is ignored.
  • The only “measurement results” plot is “force versus serial number” – which conveys no meaningful information (without being able to read associated text).
  • I learned later from Martin Tajmar, that the observed thrust drops by more than an order of magnitude when the device is powered by batteries instead of the external cables (cables whose currents can induce forces).

I chose not to cite and comment on the many non-peer-reviewed articles on Shawyer’s website and related AIAA conference papers.

Shawyer eventually published a peer-reviewed article, specifically: Shawyer, R. (2015), “Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe,” Acta Astronautica, vol. 116, pp 166-174. Shawyer states: “Theoretical and experimental work in the UK, China and the US has confirmed the basic principles of producing thrust from an asymmetric resonant microwave cavity.” That assertion has not held up to scrutiny. Therefore, all related assertions are equally unfounded. Instead of offering substantive evidence, this article instead predicts the performance for three variations of EmDrives that now claim to use superconductivity. From these, he presents conceptual diagrams for their respective spacecraft. He also mentions the “Cannae Drive,” by Guido Fetta, as another embodiment of his device.

Latest EmDrive Paper

The latest paper, in the AIAA Journal of Propulsion and Power, is an improvement in fidelity on the prior tests and may be indicative of a new propulsive effect. However, the methods and data are still not crossing the threshold of “extraordinary evidence for extraordinary claims” – especially since this is a measurement of small effects. With the improved fidelity of the reporting and the data traces themselves, I have to question my earlier bias that the prior data was entirely due to experimental artifacts and proponent biases.

The assessment offered below is a summary of discussions with the coauthors of this report plus a few other colleagues. Both Martin Tajmar and George Hathaway operate similar low-thrust propulsion test stands and thus are familiar with such details. George Hathaway’s more focused analysis will be posted in a future Centauri Dreams article.

The major problems with the paper are (1) lack of impartiality, (2) the test hardware is not sufficiently characterized to separate spurious effects from the test article’s effects, (3) the data analysis is marred by the use of subjective techniques, and (4) the data can be interpreted in more than one way – where one’s bias will affect one’s conclusions.

The first shortcoming of the paper is that it is biased. It assumes that the propulsion effect is genuine and then goes on to invent an explanation for that unverified effect. This bias skews how they collect and analyze the data. To be more useful, the paper should have reported impartially on its experimental and analytical methods to isolate a potential new force-producing effect from other contaminating influences.

The next shortcoming is insufficient testing for how spurious causes can affect the thrust stand. While this new paper is a significant improvement over the previous publications, it falls short of providing the needed information to reach a definitive conclusion. They use techniques comparable to engineering tests of conventional low-thrust electric propulsion. While such engineering techniques might be passable for checking electric propulsion design changes, it is not sufficient to demonstrate that a new physics effect exists. The specific shortcomings include:

  • Thrust stand tilting: The thrust stand has a vertical axis, where even slight changes of that alignment will affect how the thrust stand behaves. There are three parts to this, none of which are quantified: the fidelity of the thrust stand flexures and pivots, the alignment fidelity of that structure to the vacuum chamber, and the sustained levelness of the “optical bench” upon which the vacuum chamber is mounted.
  • Thrust stand characterization: The thrust stand does not return to its original position after tests, even for most calibration events. Additionally, the thrust stand is over-damped, meaning that it is slow to respond to changes, including the calibration events. Those characteristics (time for the thrust stand to respond to a known force and the difference between its before/after positions) are important to understand so that those artifacts can be separated from the data. These facets are largely ignored in the paper. The report does mention that the location of the masses on the thrust stand affects its response rate (“split configuration” versus “non-split”), but this difference is not quantified. The thrust stand uses magnetic dampers. Similar dampers used on one of Martin Tajmar’s thrust stands were found to cause spurious effects (subsequently replaced with oil dampers). Given the irregular behavior, it is fair to suspect that other causes are interfering with the motion of the thrust stand. The flexural bearings might be operated beyond their load capacity or might be affected by temperature.
  • Forces from power cables: To reduce the influence of electromagnetic forces from the power leads, Galinstan liquid metal screw and socket connections are used. While encouraging, it is not specified if these connections (several needed) are all coaxially aligned with the stand’s rotation axis (as required to minimize spurious forces). Also, there are no tests with power into a dummy load to characterize these possible influences.
  • Chamber wall interactions: Though mentioned as a possible source of error, the electromagnetic forces between the test device and the vacuum chamber walls are dismissed without quantitative estimates or tests. One way that this could have been explored is by using more variations in the position and orientation of the test device relative to the chamber. For example, in the “null thrust” configuration, only one of four possibilities is used (the device pointed toward the pivot axis). If also pointed up, down, and away from the pivot, more information would have been collected to help assess such effects.
  • Thermal effects: The paper acknowledges the possible contributions from thermal effects, but does not quantify that contribution. For example, there are no measurements of temperature over time compared to the thrust stand’s deflection. Such measurements should have been made during operation of the device and when running power through a dummy load. Absent that data, the paper resorts to subjectively determining which parts of the data are thermal effects. For example, without any validation, the paper assumes that the displacement measured during the “null thrust” configuration is entirely a thermal effect. It does not consider chamber wall interactions or any other possible sources. The paper does speculate that temperature changes might shift the center of gravity of the test article in a way that affects the thrust stand, but no diagrams are offered showing how a slight change in one of those dimensions would affect the thrust stand.

The third and most egregious shortcoming in the report is that they apply a vaguely described “conceptual simulation” (which is never mathematically detailed) as their primary tool to deduce which part of the data is attributable to their device and which is due to thermal effects. They assume a priori the shapes of both the “impulsive thrust” (their device) and thermal effects and how those signals will superimpose. There is no consideration of chamber wall effects, power lead forces, tilting, etc. As a reflection of how poorly defined this assumed superposition, the ‘magnitude’ and ‘time’ axes on the chart showing this relation (Fig. 5) are labeled as “arbitrary units.” Another problem is that their assumed impulsive thrust curve does not match the shape of most of the data that they attribute to impulsive thrust. Instead of the predicted smooth curve, the data shows deviations about halfway through the thrusting time. They then apply this subjective and arbitrary tool to reach their conclusions. Because they are biased that the effect is genuine and because their methods overlook critical measurements, I cannot trust the authors’ interpretations of their results.

Absent an adequate accounting for the magnitude and characteristics of secondary causes and how to remove those possible influences from the data, the fourth major problem with the report is that its data can then be interpreted more than one way.

Rather than evoking subjective techniques here, the comments that follow are based only on examining their data plots as a whole. To illustrate how this data can then be interpreted in more than one way, both dismissive and supportive interpretations are offered. In particular, we compare the traces from the “forward,” “null,” and “reverse” thrust configurations and then the force versus power compilation of the runs.

The data for the 80W operation of the device in the “forward,” “null,” and “reverse” thrust configurations is presented in Figures, 9c, 18, and 10c, respectively. Recall from the above discussions that this data includes all the uncharacterized spurious causes (thermal, chamber wall interactions, power lead forces, tilting of the thrust stand, and seismic effects), plus any real force from the test device. The values shown in the table below were read from enlarged versions of the figures.


Table of Noteworthy Data Comparisons Between Forward, Null, and Reverse Thrust Orientations

For a genuine thrusting effect, one would expect the results to show near-matching magnitudes for forward and reverse thrust and a zero magnitude for the null-thrust orientation. If one looks only at the “Total deflection,” all the magnitudes are roughly the same, including the null-thrust. Pessimistically, one could then infer that the spurious effects are great enough to be easily misinterpreted as a genuine thrust.


Conversely, if one considers how quickly the deflections occur, then the attention would be on the “Rate of deflection.” In that case, the thrusting configurations are roughly twice as large as the null-thrust configuration. From only that, one might infer that a new force-producing effect is larger than spurious causes.

To infer conclusions based on the deflection rates, one must also examine the rate of deflection for the calibration events, which should be the same in all configurations. The calibration deflection rate appears roughly the same in the forward and reverse thrust configuration, but more than 2.5 times larger in the null thrust configuration. That there is a difference compounds the difficulty of reaching conclusions. There are also significant inconsistencies with how the thrust stand rebounds once the power is turned off between the thrusting and null-thrust configurations, again compounding the difficulty of reaching conclusions.

Because a possible positive interpretation exists within those different perspectives, I cannot rule out the possibility that the data reflects a new force-producing effect. But as stated earlier, given all the uncharacterized secondary effects and the questionable subjective techniques used in the report, this is not sufficient evidence. Given the prominent role played by the rate of deflections, the dynamic behavior of the thrust stand must be more thouroughly understood before reaching firm conclusions.

Next, let’s examine the compilation of runs, namely Fig. 19. Based on a linear fit through the origin with the data, they conclude a thrust-to-power ratio of 1.2 ± 0.1 mN/kW (=µN/W). While this is true, the data can be interpreted more than one way. Note that the averages for 60 and 80 watts operations are the same, so a linear fit is not strictly defensible. One could just as easily infer that increasing power yields decreasing thrust, a constant 50 µNewton force, or an exponential curve that flattens out to a constant (saturated) thrust of about 100 uN. Note too that the null-thrust data (which could be interpreted to be as high as 211 µN) is not shown on this chart.


Recall too that they did not quantify the potential spurious effects, so their presumed error band of only ±6 µN does not stand up to scrutiny. Note, for example, the span in the 40W data is about ± 17µN, the 60W about ± 50µN, and the 80W about ± 32µN. What is not clear is if these 40, 60, and 80 Watt runs represent different operating parameters (Q-factor?), or if instead, these are the natural variations with fixed settings.

The pessimistic interpretation is that the deviations in the data represent variations for the same operating conditions, in which case the data are too varied from which to conclude any correlations. Conversely, the optimistic interpretation is to assume the variations are due to changes in operating parameters, but then that additional information should be made available and be an explicit part of the analysis.

In summary, this most recent report is a significant improvement, but has many shortcomings. Questionable subjective techniques are used to infer the “thrust” from the data. Other likely influences are not quantified. But also, despite those inadequacies, the possibility of a new force-producing effect cannot be irrefutably ruled out. This is intriguing, but still falling short of defensible evidence.

EmDrive and Other Space Drive Theories

First, I cannot stress enough that there is no new EmDrive “effect” yet about which to theorize. The physical evidence on the EmDrive is neither defensible nor does it include enough operating parameters to characterize a new effect. The data is not even reliable enough to deduce the force-per-power relationship, let alone any other important correlations. What about the effects of changing the dimensions or geometry, changing the materials, or changing the microwave frequencies or modulation? And then there is the unanswered question, what are the propulsion forces pushing on?

Assuming for the moment that the EmDrive is a new force-producing effect, we know at least two things (1) it is not a photon rocket, because the claimed forces are 360 times greater than the photon rocket effect, and (2) a force, without an “equal and opposite force,” goes beyond Newton’s laws. Note that I did not evoke the more familiar “violating conservation of momentum” point. That is because these experiments are still trying to figure out if there is a force. We won’t get to conservation of momentum until after those forces are applied to accelerate an object. If that happens, then we must ask what reaction mass is being accelerated in the opposite direction. If the effects are indeed genuine, then new physics is being discovered or old physics is being applied in a new, unfamiliar context.

For those claiming to have a theory to predict a new propulsion effect, it is necessary that those theories make testable numeric predictions. The predictions in Juan’s 2013 paper did not match its results. The analytical discussions in White’s 2016 experimental paper do not make theoretical predictions. The same is true with his 2015 theoretical paper: White (2015), “A discussion on characteristics of the quantum vacuum,” Physics Essays, vol. 28, no. 4, 496-502.

Short of having a self-consistent theory, any speculations should at least accurately echo the physics they cite. The explanations in the White’s 2016 experimental paper, White’s 2015 theory paper, and even White’s 2013 report on the self-named “White-Juday Warp Field Interferometer” (White (2013), “Warp Field Mechanics 101,” Journal of the British Interplanetary Society, vol. 66, pp. 242-247), did not pass this threshold. I’ll leave to other authors to elaborate on the 2015 and 2016 papers, while a review of the 2013 warp drive claims is available here. It is Lee & Cleaver (2014), “The Inability of the White-Juday Warp Field Interferometer to Spectrally Resolve Spacetime Distortions,” [physics.gen-ph].

In contrast, it is also important to avoid pedantic reflexes – summarily dismissing anything that does not fit what we already know, or assuming all of our existing theories are completely correct. For example, the observations that lead to the Dark Matter and Dark Energy hypotheses do not match existing theories, but that evidence has been reliably documented. Using that data, many different theories are being hypothesized and tested. The distinction here is that both the proponents and challengers make sure they are accurately representing what is, and is not yet, known.

If a propulsion physics breakthrough is to be found, it will likely be discovered by examining relevant open questions in physics. A relevant theoretical question to non-rocket propulsion concepts (including the EmDrive) is ensuring conservation of momentum. One way to approach this is to look for phenomena is space that might serve as a reaction mass in lieu of propellant, perhaps like the quantum vacuum. Another approach is to dig deeper into the nature of inertial frames. Inertial frames are the reference frames upon which the laws of motion and the conservation laws are defined, yet it is still unknown what causes inertial frames to exist or if they have any deeper properties that might prove useful.

Woodward Tests and Theory

In addition to the overtly touted EmDrive, there are about two-dozen other space drive concepts of varying degree of substance. One of them started out as a theoretical investigation into the physics of inertial frames which then advanced to make testable numeric predictions. Specifically I’m referring to what is now called the “Mach Effect Thruster” concept of James F. Woodward, which dates back at least to this article:

Woodward, James F. (1990), “A new experimental approach to Mach’s principle and relativistic gravitation,” Foundations of Physics Letters, vol. 3, no. 5, pp. 497-506.

A more in-depth and recent publication on these concepts is available as:

Woodward, James F. (2013) Making Starships and Stargates: The Science of Interstellar Transport and Absurdly Benign Wormholes. Springer Praxis Books.

Experiments have been modestly underway for years, including three recent independent replication attempts by George Hathaway in Toronto Canada, Martin Tajmar in Dresden Germany, and Nembo Buldrini in Wiener Neustadt, Austria. A workshop was held to review these findings in September 20-23, 2016, in Estes Park, Colorado. I understand from an email conversation with Jim Woodward that these reports and workshop proceedings are now undergoing peer review for likely publication early in 2017.

The main point here, by citing just this one other example, is that there are other approaches beyond the highly publicized EmDrive claims. It would be a disservice to our readers to let a media fixation with one theme blind us to alternatives.


If either the EmDrive or Mach Effect Thruster is indeed genuine, then new physics is being discovered or old physics is being applied in a new, unfamiliar context. Either would be profound. Today it is premature to assert than any of these effects are genuine, or conversely, to flatly rule out that such propulsion ambitions are impossible. When the discussions are constrained to exclude pedantic disdain and wishful interpretations, and limited to people who have either the education or experience in related fields, one encounters multiple, even divergent, perspectives.

Next, even if new physics-to-engineering is emerging, it is premature to assess its utility. The number of factors that go into deciding if a technology has an advantage over another are way beyond what data is yet available. Recall that the performance of the first aircraft, jet engine, transistor, etc, were all tiny examples of what those breakthroughs evolved to become. Reciprocally, we tend to forget about all the failed claims who have faded into obscurity. We just do not know enough today, pro or con, to judge.

I realize the urge within human behavior for fast, definitive answers that we can act on. This lingering uncertainty is aggravating, even more so when peppered with distracting hype or dismissive disdain. To get to the underlying reality, we must continue with a focus on the fidelity of the methods to produce reliable results, rather than jumping to conclusions on the implications.

What to Do About It

If you want definitive answers, then we must improve the reliability of the methods and data, and remain patiently open for the results to be as they are, good news or bad news. I alluded earlier to the broken tactic of trying to get answers with fast and cheap experiments. How many inadequate experiments and over how many years does it take before we change our tactics? I’ve had this debate more than once with potential funding sources and I hope they are reading now to see… “I told ya so!” Sorry, I could not resist that human urge to emotionally amplify a well-reasoned point. To break the cycle of endlessly not doing the right things to get a definitive answer, we must begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts. Granted, those types of service providers are not easy to find, where impartiality is the hardest to come by. Also, it might take three years to get a reliable answer, which is at least better than 14 years. And the trustworthy experiments will not be cheap, but quite likely far less than the aggregate spent on the repeated ‘cheap’ experiments. If any of those prior funding sources (or new) are reading this and finally want trustworthy answers, contact us. Tau Zero stands ready to make arrangements with suitable labs and analysts to conduct such a program.

And what if we do discover a breakthrough? In that case, we recommend distinguishing two themes of research, one from an engineering point of view to nudge the effect into a useful embodiment, and another from an academic point of view, to fully decipher and compare the new effects to physics in general. In both those cases we need to:

1. Characterize the parameters that affect the effects. Instead of just testing one design, vary the parameters of the device and the test conditions to get enough information to work with.

2. Deduce mathematical models from that more complete set of information.

3. Apply those models to (a) assess scalability to practical levels, and (b) explore the new phenomena and its relation to other fundamental physics.

4. On all of the above, conduct and publish the research with a focus on the reliability of the findings rather than on their implications.

For those of you who are neither researchers nor funding sources, what should you do? First, before reposting an article, take the time to see if it offers new and substantive information. If it turns out to be hollow click-bait, then do not share it. If it has both new information with meaningful details, then share it. Next, as your read various articles, notice which sources provide the kind of information that helps you understand the situation. Spend more time with those sources and avoid sources who do not.

Regarding questionable press stories, I’m not sure yet what to make of this: “The China Academy of Space Technology (CAST), a subsidiary of the Chinese Aerospace Science and Technology Corporation (CASC) and the manufacturer of the Dong Fang Hong satellites, has held a press conference in Beijing explaining the importance of the EmDrive research and summarizing what China is doing to move the technology forward.” Some stories claim there is a prototype device in orbit. If true, I would expect to see at least one photo of the device being tested in space. But we’ll see…

When faced with uncertain situations and where the data is unreliable, the technique I use to minimize my biases is to simultaneously entertain conflicting hypotheses, both the pro and con. Then, as new reliable information is revealed, I see which of those hypotheses are consistent with that new data. Eventually, after enough reliable data has accrued, the reality becomes easier to see.


The cited devices have gone by multiple names (e.g. EmDrive, EM Space Drive; Mach Effect Thruster, Mach-Lorentz Thruster), and the versions used in this article are the ones with the greatest number of Google search hits.


{ 104 comments… read them below or add one }

Thomas Goodey December 30, 2016 at 11:35

There’s a lot of junk science being done in China. And, if the peer reviewers of junk are likewise junk, then peer review means nothing.


ljk December 30, 2016 at 16:21

I distinctly recall when cold fusion was first announced in 1989, the Soviet Union declared it had duplicated their own cold fusion experiments 17 times. Funny how we never actually saw anything from them and it all disappeared shortly thereafter.


Albert A Jackson December 30, 2016 at 18:35

“The meaning of the world is the separation of wish and fact.”
— Kurt Gödel


AlainCo January 3, 2017 at 5:23

Cold Fusion, aka LENr is replicated thousands of time, and it is published in more than 153 peer reviewed articles showing excess heat.

There is only 4 peer reviewed papers who claims to explain an artifact for F&P experiments.
The two first (Lewis and Hansen), are refuted by experts in mainstream calorimetry and by the last paper of Wilson.
Morison paper is so incoherent and absurd that it is hard to understand how it could be peer reviewed, except because the conclusion was pleasant and the reviewer incompetent.
Wilson paper is finally the only competent paper, but the conclusion is over-interpreted. After refuting previous critics, it conclude that a slight correction can explains the excess heat of small results, but F&P showed alos huge burst that cannot be explained by Wilson correction (Fleischmann used that correction in later works).
The details and citations are well detailed in “Excess Heat” by Charles Beaudette, the most documented book on the domain.

the initial myth is based on 2 crush tests done by physicists in the first 40 days, and ignores results done by chemists after more than one year of hard work.

LENR shows how Groupthink , caused by initial errors (of Fleischmann in particle detection, in calorimetry by Caltech and MIT), launch a cognitive cascade that impossible to unlock.

The good point is that for EmDrive it is not yet there, and if there is skepticism and oppositions to further research (the symptom of bad science and voodoo consensus is refusal to further research), it seems not yet established as a definitive dismissal.


ljk January 3, 2017 at 11:10

So what exactly has been done with cold fusion in terms of making our civilization a better place?


AlainCo January 3, 2017 at 14:50

good science…
peer-reviewed papers describing experiments proving an anomaly.


this is triggering research efforts by Japanese alliance involving Tohoku university with Toyota, MHI, Nissan among partners…
This involve TTU in Texas with Robert Duncan and Seashore Research funded by Bill gates…
This involve SKINR in Missouri.

by the way, do you realize that you just said that since an anomaly have not yet any application, it does not exist and thus does not deserve to be investigated to find applications ?

are you so much lost in biased reasoning that you did not see how fallacious is that reasoning.

I forgive you as you are very … replicated…
This is a very common reasoning, you are not exceptional.
I’ve heard that argument many times today. It is fun. Is it an academic version of PostTruth?

Kindly yours.


ljk January 3, 2017 at 15:29

Replicated? Replicated? Hansel?

I admit I haven’t fastidiously pursued the goings on about cold fusion since the big announcement back in 1989, but the fact that little if any such presumed events have caught my attention for someone who keeps up with both science and regular news all the time says a lot about what CF has and has not done in the last nearly thirty years, at least for me.

Now please note I did not mean to say that CF doesn’t exist because it hasn’t improved my golf swing – and I don’t even golf – I just wanted to know why I haven’t seen it do much.

And is it really so bad to ask what CF can do for me? Or have I entered the religious dogma zone as I also see with the EM Drive and Warp Drive with its True Adherents and I Shall Dare Not Question?

Maybe CF needs better PR reps. Especially the kind that do not attempt to belittle those who dare to question the Keepers of the Holy CF. Because this feels more like a cult than science.


Michael T January 10, 2017 at 21:38


However, assume for the sake of argument, that a field of research has, for good OR bad reasons, fallen into disrepute. Then it will become harder to get funding, harder to attract researchers, and harder to get research accepted. Naturally technological exploitation will also be retarded, even IF some phenomenon is genuine. The point if this is not that we should be credulous. It is that lack of use doesn’t mean non-existence.


ljk January 3, 2017 at 15:36

An obscure science journal from India. No, that’s not suspicious at all.


Antonio December 30, 2016 at 11:57

Does this pseudoscience really deserve an article here?

“To break the cycle of endlessly not doing the right things to get a definitive answer, we must begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts.”

Heck, no! Qualified labs and analysts have much more important things to do! I hope they don’t waste my taxes to do that!


rfmwguy December 30, 2016 at 13:50

As somebody (DIY) who has designed, built and tested a couple of EmDrives over the past couple of years, I find this article very well written and objective. The main takeaway I have on the EmDrive is that I observed a displacement force on both a teeter totter and torsion beam test stand using two different cavity designs at ~2.45 GHz. While I cannot say if this will pan out for interstellar propulsion, I believe it is perhaps a small crack in the wall of the mass ejection/rocket “tyranny” which will never get us there. Thank you for opening up to the possibility. Be prepared for a fair amount of pushback from the public…it comes with the territory. Good luck.


Bryan Kelly January 2, 2017 at 17:22

On the other hand, “mass ejection/rocket “tyranny” may only be a crack in the wall obscuring what gets us to interstellar propulsion without any new physics, i.e., light continuously pumped through mass at the speed of light with us riding along, a hydrogen light pump-jet.


rfmwguy January 4, 2017 at 17:29

I agree. The EmDrive is about as close as we’ve come to being on the verge of true interstellar propulsion, despite the obvious concerns there are with known physics. Known physics is the operative phrase here and I for one believe “Known physics” is a changing landscape and will be for the foreseeable future. I’d suggest we explore the “cracks” as much as possible with experimentation over argumentation. Few real discoveries are made by playing it safe, thus the common phrase: no guts…no glory.


David Taylor-Fuller December 30, 2016 at 14:07

It is your kind of thinking that makes it damn near impossible to make any progress at all. It is not sufficient to discount an idea from further analysis just because it doesnt jive with your interpretation of physics. That justification presupposes that; one, your interpretation of physics is correct. Two, physics is a 100% accurate description of reality. While it is likely that the first is a valid assumption. I would bet ungodly sums of money that the second is not.

That said, the only requirement for further study of new experimental effects should be whether or not the person proposing the idea has done everything within their knowledge and capability to address experimental issues. If that is done, and the analysts at “Qualified labs” cannot suggest simple changes to experimental protocol within the inventors capabilities to do. Then the ball is firmly in the court of others to further the cause. Now I am not trying to be unreasonable. I am sure “Qualified Labs” have a lot of work they could be doing. That said, the fact that they have work they deem more important to do does not absolve them from eventually evaluating other experiments they deem less important.


Antonio December 31, 2016 at 3:29

“It is not sufficient to discount an idea from further analysis just because it doesnt jive with your interpretation of physics.”

Huh?? It’s not because that, it’s because White and co. don’t have any evidence worth of that name! There are zillions of stupid claims out there. Scientists can’t test them all, and certainly they shouldn’t!

“As a variation on an old saying if you don’t have anything constructive to add then don’t post at all.”

Good description of you post.


tchernik December 30, 2016 at 15:05

If there are falsifiable claims, a clear replication recipe and no definitive validations or refutations, yes, it does deserve attention here and elsewhere.


RAS December 30, 2016 at 16:23

As a variation on an old saying if you don’t have anything constructive to add then don’t post at all.


Bill Housley December 31, 2016 at 9:42

Antonio–Prior to the peer-reviewed publication…no.

However, this publication puts someone’s reputation on the line and seems to credibly challenges the claim that this is in fact “pseudoscience”. I don’t think that the burden of proof has shifted over to the nea-sayers…yet…but it’s moving towards them. At the very least the complaints are already well documented to the point where continuing to beat those dead horses has become unhelpful. At this point this issue needs more data that accounts for the variables and less arm-chair quarterbacking.

So if anyone else wants in on it at this point, then it’ll really be more helpful if just they ante up some effort and build something.


James Stilwell December 30, 2016 at 12:10

It’s another Dean Drive or we’ll soon be traveling to the planets…


Thomas Goodey December 30, 2016 at 13:39

Personally I back, Dean drive.


Larry Kennedy December 30, 2016 at 12:24

Thanks for a very rational post.


Edward Friday December 30, 2016 at 12:37

Very balanced treatment of a topic that, as Mills et. al., said, involves “behaviors that have nothing to do with physics.”


xcalibur December 30, 2016 at 12:40

I would assume that if this is genuine, there must be some sort of propellant/reaction that is being overlooked. Certainly if you could generate an electromagnetic field and use it for thrust, it would be quite useful, even if it is not reactionless.


Michael December 30, 2016 at 13:35

If it emits photons it is not a propellant less drive, my microwave emits loads of photons but it is not propellant less. To me propellantless would be the drive emitting Space-Time packets without mass or energy, I can’t see how this would be possible.


Thomas Goodey December 30, 2016 at 13:50

But, if due to new physics it is doing that, there is no particular reason why you would be able to see how it was possible! It would be totally outside your sphere of imagination (and mine). So what you can see how is possible, is really no criterion at all.

I don’t know about this Shayler drive – I expect it is pure BS – but sooner or later, somebody will discover something radically new in physics, and by the nature of imagination, it will be beyond our imaginations, at least, beyond those of our imaginations that are properly disciplined. Only an out-of-control imagination can visualize something really new, and, unfortunately, such an imagination is of little use.


hiro December 30, 2016 at 21:14

The foundation has been laid for more than 20 years, there is no need for any new physics. The problem is that people from the top simply refused to try testing some new physics models (that might have failed most of the time). Sometimes they just acted no different from those Flat Earthers ( someone had friendly chat with these people and failed in the end ).


Thomas Goodey December 31, 2016 at 12:00

Whaaaaat? Some guy comes up with a system that claims to violate conservation of linear momentum, and you say that (assuming it actually works) there is no need for any new physics?

To the contrary, if the Shayler drive works (which I doubt), physics will need to be revised drastically. Nobody will accept that it works, without a set of the most careful experiments to prove it – which have not been performed yet.


hiro December 31, 2016 at 18:38

We have already had the FTL neutrino story for a few years, then after that the gravitational wave proving inflation or multiverses (can’t remember). It’s best to wait for more tests before conclude needing new physics. In the worst case scenario, this is like the Euler’s 5th postulate again; however the math has been here for quite sometime, only the physics part is still in the domain of ignorance.


hiro January 1, 2017 at 18:23

*Euclid’s fifth postulate


sanman January 3, 2017 at 6:39

Arguably, the expansion of the universe is violating Conservation of Momentum – what’s making it expand like that? Gravity is attractive, not expansionary. What rules out a man-made device being able to push off the Quantum Vacuum? We’ve already seen nano-engineered structures which exploit the Casimir effect to create virtual springs which can push surfaces apart at the nano-scale (nested hemispheres, for example). There seems to be some Casimir effect involved in the EMdrive explanation, in that it relies on a resonant cavity which can selectively exclude certain wavelengths in an asymmetric way.


Alex Tolley December 30, 2016 at 14:49

If the vacuum is a constant seething of particles forming and disappearing, it is conceivable that you might be able to harness these particles before they disappear in some way. That still might not be “reactionless” by your definition, but it might appear to be to an observer.

Another possibility is harnessing dark energy. If a device could magnify its effect at a local level, that might be an example of a true reactionless drive, would increasing gravity or generating directional gravity to pull the craft towards a target.

Any drive should obey the law of conservation of energy, so any drive that appears to violate that should, IMO, be suspect.


Thomas Goodey December 30, 2016 at 17:07

If it violates (bypasses) the law of conservation of momentum, why shouldn’t it violate the law of conservation of energy?


sanman January 2, 2017 at 5:49

It’s not violating Conservation of Momentum, in the the sense that it’s not a closed system – just like a propeller on an airplane or boat isn’t violating Conservation of Momentum.


Thomas Goodey January 2, 2017 at 9:52

Well, who said that? There is some airy-fairy idea that it is pushing against the virtual particles seething in the vacuum, but that is not supported by any concrete theory, and is not consistent with physics as we know it. Apart from that “possibility” which is not really a possibility, how is it not a closed system?


sanman January 3, 2017 at 6:00

Just because the theory hasn’t been precisely defined, doesn’t mean we won’t have to pay attention if the thing actually works. People didn’t have to know the exact theory behind propellers or even oars and paddles, before they started using them. Science is an interplay of Theory and Observation – sometimes your known theory causes you to overrule a conflicting observation and declare it a mistake – other times the strength of the conflicting observation forces you to revise your theory. If this thing can outperform a Photon Rocket by a wide enough margin, and if sources of error can be adequately catalogued and bounded, then it could be seen as something that challenges accepted theory. People will continue to scour the contours of physics for chinks and cracks in its armor. As long as we stick to the Scientific Method, we have no need to fear any ridicule.


Jossarian January 3, 2017 at 10:35

Regarding the law of energy conservation.

Currently the electrical energy is the energy mainly derived from kinetic energy, this is how electrical generator works in power plant. I don’t get why we can’t change electrical energy into kinetic energy then? It seems to be valid in principle.

If EmDrive works as claimed then it is transforming electrical energy into kinetic energy (if tested in “zero g-force” environment). The law of energy conservation is preserved if amount of electrical energy is less then amount of produced kinetic energy.

I think this limit could be seen as maximum possible force in Newtons which one kW of electric power can produce in EmDrive.
Implication of this is that the Roger Shawyer claims from 2014 publication: “increase the first generation specific force of 300 mN/kW to a target of 10 kN/kW” are not valid as it would mean that EmDrive is perpetual motion machine of the first kind.


rfmwguy January 4, 2017 at 17:37

Don’t think I’ve noted this opinion of yours on NSF, Dr.


Robert Walker January 20, 2017 at 18:26

Just to say – that new discoveries may well seem to violate conservation of energy when they are first made. Beta decay seemed to violate conservation of energy and momentum, and lead to the discovery of the neutrino.

Good balanced article!

I did an article a while back on Science20 on EM Drive http://www.science20.com/robert_inventor/suggestion_the_em_drive_is_getting_the_appropriate_level_of_attention_from_the_science_community-156719)


Thomas Goodey December 30, 2016 at 13:38

Yes, but if it is not reactionless (i.e. if it pushes against something that we haven’t spotted yet), then it is hardly going to work in space, is it, unless you supply it with that something? Which would essentially mean that it is not much use in the end, since it would just do what an ion drive does, only much less efficiently.


sanman January 3, 2017 at 6:03

The more appropriate comparison is with a Photon Rocket rather than an Ion Engine. Operating the apparatus for an extended period of time and then weighing it for any loss in mass might be a way to rule out any ion propulsion effects.


Asteroidenbergbauer December 30, 2016 at 13:12

there was another interesting paper from roger shayer, acta astronautica. vol.116

Second generation EmDrive propulsion applied to SSTO launcher and interstellar probe.

amazing times ;)

“If I had asked people what they wanted, they would have said faster horses.”
(Henry Ford )


Joe December 30, 2016 at 13:14

This is a very impressive article. I would love to see Centauri Dreams post a similar article with this level of rigorous evaluation to Low Energy Nuclear Reactions (AKA Cold Fusion.)


Bruce Mayfield December 30, 2016 at 13:57



Alex Tolley December 30, 2016 at 13:41

This is by far the best post I have read on the EM Drive. Will throwing a lot more resources get a definitive answer, of will this be a repeat of the cold fusion story that remains a zombie? The claim by China that an EM drive experiment on their space station confirmed it works has yet to show any evidence. I look forward to a review of any published work that emerges.

Feynman famously said “The first principle is that you must not fool yourself – and you are the easiest person to fool.”

More relevantly here is this: “There is one feature I notice that is generally missing in cargo cult science. It’s a kind of scientific integrity, a principle of scientific thought that corresponds to a kind of utter honesty — a kind of leaning over backwards. For example, if you’re doing an experiment, you should report everything that you think might make it invalid — not only what you think is right about it; other causes that could possibly explain your results; and things you thought of that you’ve eliminated by some other experiment, and how they worked — to make sure the other fellow can tell they have been eliminated.”

My sense is that these experiments are not that well done and that tests that could have been done were not. Was this lack of time or resources, or due to a desire to only present confirming evidence of an effect?


ljk December 30, 2016 at 13:57

The other question to look into is, who is attempting to benefit from this project? And by benefit I mainly mean making money (and fame, which will generate more money) off it. Whether the EM Drive ultimately works or not is not the point to such people if pure profit is the case.

Most people, even and including rich ones, are neither scientists nor engineers. They have been told in numerous forms that some kind of hyper or wrap drive is the only real way to reach the stars. They do not want the details, they only want to know that someone claiming to be an expert makes it work.

The EM Drive is not a faster than light (FTL) propulsion drive, you say? No, it isn’t, but many have not bothered to differentiate this little fact. This is why real scientists and real engineers need to examine this device in detail and drag it into the light. Dismissing it without any explanation will only fuel the fires of ignorance – or has no one learned that lesson from this year’s election?


Thomas Goodey December 30, 2016 at 14:07

From the article, it seems that those experiments were shockingly badly done. I am rather stunned by the inefficiency of those laboratories.


Eric December 30, 2016 at 14:01

Good article, and thanks for guiding us through a swamp of rumor and sensationalism. Thanks also for offering a rational approach to pursuing this. I too agree that the chance that these approaches will lead to new physics is pretty remote.

But let’s say it is 99% likely to go nowhere but reveal experimental artifacts. Even a 1% chance for something very new is interesting and important so it is worth pursuing to get more clear results. We need to be less risk adverse in science, otherwise we’re only going to learn what we more or less already know. That’s not to say we accept sensationalism, it means we should be sometimes give a second look at weird results on the threshold of noise.

Even with adequate funding, more stringent testing of the EmDrive and Mach Effect drives would be orders of magnitude cheaper than many Dark Matter experiments, not to mention CERN. Remember, the Dark Matter searches have so far turned up null-results. Physics research is full of leads that go nowhere.

So I think it’s worth investigating deeper, even if the most interesting outcomes will be new insights in human psychology and less physics. :)


Neil S December 30, 2016 at 14:07

Thank you for a reasoned, open-minded approach to this. You and your colleagues.


Douglas Dwyer December 30, 2016 at 14:40

An excellent summary. I am not inclined to believe; but
if there was something in it and the mechanism was exploited billions of light years away to accelerate real mass in an impulse the the result on Earth would look like a Fast Radio Burst.


Douglas Dwyer December 30, 2016 at 14:45

Though a non- believer ; If it works then it exploits non-linearity in free space.


ljk December 30, 2016 at 16:18

This is not a belief system. This is supposed to be science. Just like no one should “believe” in alien life unless they are supernatural and you actually worship them.


RobFlores December 30, 2016 at 15:21

A. Tolley, Spot On.

These experiments on Em Drives are very constrained.
A whole battery of Experiments could be done, to demonstrate the
parameters of possible error sources, they have not done that to exhaustion. It is not enough to cite literature on similar approaches. You must fully characterize your device first and Then attempt explain away anomalies, until the only explanation is thrust.

As a side note, fully characterized includes launching these “devices” into
solar orbit with separate micro-sat instrument payloads for measurements. That is I do not 100% trust Terrestrial or even LEO tests. Put it out there and see it if actually does something, it is the only way to be sure.


J. Jason Wentworth January 3, 2017 at 3:17

FINALLY, someone (thank you, RobFlores) has suggested perhaps the only reliable way to determine if the EmDrive (or the Mach-Lorentz Thruster, or any such unorthodox propulsion system) really works:

Launch an EmDrive test unit into solar orbit (it could even fly cheaply as a “hitch-hiker” payload [after delivering its satellites into orbit, the Centaur stage of an Atlas 5 launched in November disposed of itself in solar orbit, from a near-polar Sun-synchronous orbit; its excess escape payload margin would be even larger in an easterly launch]), turn it on, and see what happens, and:

If it produces measurable acceleration in any direction (thrusting prograde, retrograde, and at various angles to the plane of its orbit), it will be time to get excited. If it produces acceleration only when thrusting against the solar magnetic field (at its local field lines orientation at the spacecraft’s location; onboard magnetometers could determine that), the EmDrive could still be useful around planets with magnetospheres, as well as around stars (thrusting against the galactic magnetic field might make it useful for interstellar propulsion, provided that the local field lines were properly aligned with respect to the desired destination star). Also:

This may upset some people, but I don’t care if the EmDrive seems to violate the laws of physics. Marconi disregarded the statements of the physicists of his day, who said that radio signals would not pass over the horizon, but would pass straight out into space just as a searchlight beam would. He had only a hunch that radio signals would act differently, and would propagate around the Earth beyond the horizon, and his hunch proved correct–and physics had to catch up with his hunch, to explain WHY his hunch proved to be correct. Not all such hunches prove to be correct, of course, but testing the real universe (instead of refusing to conduct certain experiments because human beings’ mathematical model of the universe–in which they have deeply invested emotions–indicates that the experiment can’t possibly have positive results) is the only way to truly know what won’t work…and what will work.


Brian McConnell December 30, 2016 at 15:25

I remain skeptical about the EmDrive, but am keeping an open mind. One possibility that has been mentioned is that dark matter is interacting in some way that allows it to be used as reaction mass. That would be interesting as a scientific outcome, even if the effect remains too weak to be used for practical propulsion. That said, I would put my money on a problem with the experimental setup, like electromagnetic coupling with the vacuum chamber walls.


Randy Chung December 30, 2016 at 17:16

I’ve wondered about the chamber walls, too. I’d feel better if they added and removed some wideband RF absorbing panels (like the ferrites used for stealth vehicles) to see if that made a difference.


craig watkins December 30, 2016 at 16:49

So nice to see a reaction here! I’ve been waiting patiently to see an article discussing this for some time. There’s a lot of either sensationalized or offhandedly dismissive coverage on this and it was nice to see a sober approach.


Richard December 30, 2016 at 17:13

How about sending the device into space and testing the effect there. Oh, that’s such a reasonable proposal the Chinese are actually doing it. Galileo “Yet it moves!”


Thomas Goodey December 30, 2016 at 18:04

I think it will be more like “tuttavia non si muove”!

(at considerable expense)


ljk December 30, 2016 at 19:36
James Stilwell December 30, 2016 at 18:14

If the universe was born spinning, maybe the net angular momentum of the universe is what others are attempting to measure without realizing it…A shot in the dark…well outside acceptable physics…maybe…we’ll see…what if…


hiro December 30, 2016 at 21:01

Dr. Godel did cook up the same universe model which allows Quantum CTC in large scale. However, the physical reality is extremely cruel.


Tom Greenhaw December 30, 2016 at 18:52

Dumb question: Why not have the teams claiming propellantless propulsion supply a suitable battery powered unit, take them into space and then activate them. If one or more moves, we have something to look at. If they don’t, then we move on. Isn’t there something to be said about a simple empirical test?


Robert G December 30, 2016 at 19:39

Thank you very much for this extremely clear and well written article.

Extraordinary claims require extraordinary proof. I think they need to go above and beyond plain vanilla peer review as well, and articles like this one seem a service towards that end. It seems to me as though this is replicating not the experiment, but the review process itself with additional eyeballs and experience.

Is there a name for this?


Andrew Palfreyman December 30, 2016 at 22:27

This was a good review. Closure will only come with a space-based test that is professionally designed and instrumented.


Thomas Goodey December 31, 2016 at 12:01

Closure (negative) could come with a terrestrial-based test that would be professionally designed and instrumented. It is clear that the tests so far have been very amateurishly set up.


tyy December 31, 2016 at 4:18

Nice article, thank you.


Bynaus December 31, 2016 at 4:20

Excellent article: open-minded, fair, and focused on the experiments.

While I do not have the means to fund an entire project “done right”, I would be more than ready to contribute to a crowd-funded study set up by the Tau Zero foundation. I suspect I might not be alone…


David Randall McKay December 31, 2016 at 8:25

Love how everyone thinks they know everything about physics, and nothing new could possibly exist. Grow up, people.


Bill Housley December 31, 2016 at 12:42

Thank you for a very detailed analysis. Your points about the lack of a “dummy load” for the cables and the heat are especially useful. I hope that someone at Eagle Works heard that so that follow-up can focus in that direction. They are the best ones to go back and include those measurements because it is their equipment that generated the data that those measurements would need to compare to.


Project Studio December 31, 2016 at 12:55

Glad to see minds are opening up. I think the emphasis should be on qualifying the empirical effect. Like Michelson-Morley, it is the stunning experimental result that can spark new conceptual theory compatible with it. Much credit is deserved by the researchers who have through very limited means demonstrated enough to overcome the incredulity with which this phenomena was originally received. Hopefully more money will be invested to fully quality the effect to satisfy the reasoned critiques.

Personally, I was satisfied as to Eaglework’s characterisation of thermal component. But reasonable minds could reasonable want to delve deeper. The physics of the actual physical systems – however simple we try to make them – is very complex. I’d like to see a proper critique of Eaglework’s error analysis once two-way dialog is set up – if Tau Zero could facilitate.

Although it’s a poor comparison, I’m sometimes reminded of the arguments that claimed a rocket could not operate in space because there was nothing for the rocket to “push” against. I’m glad that argument didn’t stop Goddard from experimenting with his rockets. Yes I think there is something to the em-drive. But more so, I have thought, and continue to think, this is an approach worth investigating further. It pulls at the edges of our understanding. Perhaps nature will do much more than we ever imagined to ensure momentum is conserved across different reference frames. But that’s theory. Let’s establish the empirical fact.


Tom Baty December 31, 2016 at 13:15

Great article…superb commentary. I have learned a good deal from this article and the following discussion.


Robert Kennedy December 31, 2016 at 18:27

Marc wrote:
“Chamber wall interactions: Though mentioned as a possible source of error, the electromagnetic forces between the test device and the vacuum chamber walls are dismissed without quantitative estimates or tests.”

Yep, I think so. My friend David Woolsey, also a working experimental physicist in the Bay Area, looked into this and hypothesized that uwave resonant interaction of RF radiation between the test object and the *undamped* test chamber is of sufficient magnitude to explain the observed result. The “Q-factor” is of order 10^4. Suggestions he made 2 years ago to the PIs to correct this flaw in their test apparatus (by installing simple absorbers to reduce the Q-factor) went unanswered and apparently unheeded. See his blog:




Project Studio January 1, 2017 at 10:12

However, the recent test results conducted in a vacuum chamber are of the same magnitude as the earlier tests conducted at standard pressure. This would tend to indicate that there is no significant interaction with the chamber walls. But for sure, do a test run with a proper RF absorber in the test chamber environment and see what happens


R. Gopalaswami December 31, 2016 at 22:12

“….To get to the underlying reality, we must continue with a focus on the fidelity of the methods to produce reliable results, rather than jumping to conclusions on the implications….”
Marc Millis’s article brings out what is the nature of substantive content and meaning of a scientific review of other people’s work. There is real beauty in the objective perspective of the author’s thought processes, a true rendering of the interface between physics and engineering, the transition from conceptual design and conceptual simulation to validation of the concept through experiments, and the human factor of “bias” that is an essential corollary which introduces the subjective perspective .

The topic addressed is Electro-Magnetic Propulsion, or “massless propulsion” in space where the thrust is in the order of micrograms, but sufficient to cut down the time for travel to Mars from months to days.
Measuring such ultra-low levels of thrust on the ground poses many possibilities of experimental error that tend to defeat the fundamental assumptions and conclusions of the theory and experiments The reviewer thus suggests constructively that ” Even if it turns out that the effects are of minor utility, having new experimental approaches to explore unfinished physics would be valuable….”.

The author offers a splendid example of clear and rigorous thinking to review the finding and claims of scientists in many countries, based on their published papers, analysis of his creative numerical extractions from various Figures in their papers, and his very careful observations on the practical details of the experimental set-up.

Essentially he brings out repeatedly that the reaction forces from several items of the experimental rig are in the same order of magnitude as the very propulsive force that is being measured. But while casting serious doubts on the fidelity of these experiments based on data and analysis, his nevertheless leaves the options open to other scientists and policy makers to continue to look in this direction.

This work is a superb example of scientific objectivity needed to verify new concepts, innovations and inventions that appear to defy the known laws of physics and contradict the work of many past generations. He brings out the need to break the cycle of endlessly not doing the right things to get a definitive answer, and to begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts.

THIS IS GENUINELY CONSTRUCTIVE REVIEW, unlike the sometimes very destructive review of scientists of new concepts advanced by others, and policy decisions by leaders of scientific institutions to kill evolution of new concepts based on such biased review.

The author lucidly brings out how the human factor of “…..Our decisions about this physics are influenced by behaviors that have nothing to do with physics. To ignore this human element would be a disservice to our readers. To get to the real story, we need to reveal that human element so that we can separate it from the rest of the data, like any good experiment…….. I know I have an in-going negative bias on the EmDrive history. To create a review that reflects reality, rather than echoing my biases, I had to acknowledge and put aside my biases……
(1) Do you already have an opinion about this effect and are now reading this article to see if we’ll confirm your expectation?
(2) Do you want to know our conclusions without any regard to how we reached those conclusions?
(3) Are you only interested in this EmDrive assessment, without regard to other comparable approaches?
If you answered “yes” to any of those questions, then you, like me, have natural human bias


Harold Daughety January 1, 2017 at 1:51

All I see in the EM Drive, Cold Fusion and the Dean Drive is that the desire for the thing to work overwhelms the capability to see null results and to magnify some unexplained transient behavior as proof of the concept. I spent a few minutes listening to an explanation of a perpetual motion machine, then pointed out that work and force were not the same thing. The proponent would not accept that at all and continued to elaborate on why it would work. He was an excellent draftsman considering he only could use a felt tip pen and loose leaf notepaper: he was a long term patient in a psychiatric hospital and I, the unit social worker, was accused of being in cahoots with the CIA. The playing field in the hospital was vastly different from the three proposed discoveries, but the human element is the same.


Thomas Goodey January 1, 2017 at 9:42

I do not think it is fair to lump the EM drive, cold fusion and the Dean drive indiscriminately together. The Dean drive was obvious rubbish even back in 1960, as could easily be understood by looking at Dean’s patent (I actually did). Cold fusion has many hundreds of researchers reporting different vaguely positive results worldwide, and it is difficult not to believe that there is something there, although exactly what is debatable. This Shayler EM drive is somewhere between the two on the continuous spectrum between absolutely nonsensical pseudoscience, through to solidly demonstrated scientific fact.


Don Diego de la Vega January 1, 2017 at 5:57

This is a typical Millis armchair quarterback rant. Lot’s of words what others should do, no action on his part, either theory or experiment. He does not know about how isotropic mass modulation does not violate momentum conservation, and leads directly to center of mass acceleration. The needed momentum is borrowed from the distant mass in the universe via the Machian radiation reaction, which requires both advanced and retarded wave gravitational interaction with all the mass in the universe. This same interaction apparently allows the borrowing of energy also, making the universe a sort of amplifier.

It is easy to make long laundry lists of what experimenters should have, could have done. However, first reports rarely contain that level of detail. Since Millis obviously does not understand that even cheap and quick experiments are rarely cheap or quick, it is not surprising that the experiments of anyone trying to do something new on very limited budget and with 1 or 2 people working part time in a lab is not going to meet his criterion for testing.

If you want to see more rapid progress Mark, do some experiments yourself, or help someone who is performing them. You obviously are not capable of doing the required theory. So I challenge you, put up or shut up! Stop writing endless and repetitious critiques and help the people doing the hard work in the trenches.


Daniel January 2, 2017 at 8:04

Well said Don Diego de lá Vega! Simple and direct comment the best comment here.

We don’t want just talk Mark,we want you to put what you write in action with experiments,if one day interstellar travel ever happen will start with experiments and not with just talk,Tau Zero foundation should help others scientists or do it’s on experiments and published per reviews on the criterion than you write here in this article.


jlandau January 2, 2017 at 10:14

Quoting directly from the Millis article:

“To break the cycle of endlessly not doing the right things to get a definitive answer, we must begin a more in-depth experimental program using qualified and impartial labs, plus qualified and impartial analysts. Granted, those types of service providers are not easy to find, where impartiality is the hardest to come by. Also, it might take three years to get a reliable answer, which is at least better than 14 years. And the trustworthy experiments will not be cheap, but quite likely far less than the aggregate spent on the repeated ‘cheap’ experiments. If any of those prior funding sources (or new) are reading this and finally want trustworthy answers, contact us. Tau Zero stands ready to make arrangements with suitable labs and analysts to conduct such a program.”


Robert January 2, 2017 at 14:58

But Millis is wrong to imply that the current experiments are not reliable. They just are not reliable to him but other competent scientists disagree.


ljk January 3, 2017 at 10:29

So what EM Drive experiments have you guys conducted? Only fair to ask.


Michael Spencer January 3, 2017 at 7:06

“The needed momentum is borrowed from the distant mass in the universe via the Machian radiation reaction, which requires both advanced and retarded wave gravitational interaction with all the mass in the universe. ”

Would you like Thousand Island on that, sir, or perhaps oil and vinegar?


Ron S January 1, 2017 at 10:45

What I’d like to know is how this paper passed peer review. What process does the Journal of Propulsion and Power follow in this regard?

Happy new year to all.


George Turner January 2, 2017 at 0:36

The way I would test such a drive is:

a) Mount two thrusters face to face (fwd and rev), along with a dummy load, and suspend them via a nylon cord hung from a wooden frame.

b) Feed power to the assembly with a coax cable tie-wrapped to the nylon cord.

c) Use a remotely (RF or IR) operated solid-state relay to switch power between fwd, rev, and dummy.

d) Swing the assembly to find it natural period of oscillation as a pendulum.

e) Around the device, suspend other equipment from the ceiling with similar cords, adjusting their length so their period of oscillation matches that of the device. This is to test the idea that the thruster is just a very poor rotor in an electric motor, and that something nearby must be acting as the stator (equal and oppositve forces). If the device starts swinging and nearby equipment starts swinging, the swinging equipment is the stator.

f) Cycle power to the fwd or reverse thruster at the pendulum’s natural frequency. Record the results.

g) Vary the atmospheric pressure, north/south orientation, nearby equipment (plastic, wood, copper, steel, super-magnets, etc), power levels, and RF frequency. Record the results.


Ronald January 2, 2017 at 7:44

Happy, healthy and prosperous new year!
And a year with many new planetary discoveries!
In particular all the best wishes to Paul, keep up the good work.


Ivan Vuletich January 2, 2017 at 8:25

Great article, when I first heard about the EM-drive I had no idea that doing a definitive test of the drive would be so hard.

One thing that leaps out at me is that, even if genuine, this effect is so small that it is hard to distinguish from experimental noise. This makes me suspect that the results are just experimental noise.

On the other hand, does anyone have any ideas on how to increase the magnitude of this effect to make it easier to study? Because, if not, a space based test is unlikely to reveal much, as any experiment would have to go to great lengths to account for things such as residual drag, photon pressure (from the Sun), tidal effects, interactions with solar wind etc.

My favorite speculation about the EM-drive is that it is not a propellant less drive, instead its a dark matter acceleration device! After all, dark matter particles could pass through the closed end of the device as if it wasn’t there.


Zephir January 2, 2017 at 9:30

/* Now that the EmDrive has made its way into the peer-reviewed literature, it falls in range of Tau Zero’s network of scientist reviewers */

It doesn’t mean very much because the cold fusion is way better supported with experiments (even with these peer-reviewed ones) and it still never penetrated into mainstream journals. You cannot teach old dog new tricks as Max Planck once wrote:

“A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”

It just means, the skeptics will remain skeptical, no matter what – actually the more, the more arguments they will get (backfire effect)….


ljk January 3, 2017 at 10:27

Has anything useful ever been done with cold fusion? Billions of dollars and decades have been spent on hot controlled fusion with only a few seconds to show for it, and there is plenty of scientific evidence for the latter.

Yes, I am asking for the practical value of cold fusion and the EM Drive as well. Because thought experiments and the equivalent of guys tinkering in their basement can be nice and even fun, but since everyone wants them to take us to Alpha Centauri in 30 minutes or less, I think it is only right to ask if these so-called devices can serve us in our quest to conduct fast interstellar travel, or even fast interplanetary travel for that matter.


Bart January 2, 2017 at 14:41

The power being applied is fairly large, and the measured thrust comparatively small. Might it be possible that the application of such high power is causing ions to be ejected from the surface of the device at high velocity, and due to its shape, there is an asymmetry producing a net thrust? Then, it would become an ordinary action-reaction device, with the casing playing the role of a fuel rod in a more conventional such device.

I would aver that some sort of particle detection device should be included in the experimental setup, to see if, in fact, there is or is not some mass exchange going on.


Brian McConnell January 2, 2017 at 16:38

It seems to me that this would be a good cubesat experiment. If it is possible to fabricate a lightweight, low power version of the device, this could be launched as a freeloading payload to geostationary orbit. That’s high enough that atmospheric drag is nil compared to low orbit. Then let it run for a year, and see how the orbit changes and compare that to the predicted effects of photon pressure. Even at these low thrust levels, it would build up measure delta v over the course of a year.


Mike Serfas January 2, 2017 at 19:05

This posting gives many excellent reasons for skepticism. Yet I do wonder if there could exist some massless particle for which the vacuum has a high refractive index. I realize this is a bit preposterous, but if I can accept a Higgs field with a non-zero value throughout space, I may feel like anything is possible.

By way of comparison, photons seem to be drawn into glass and other substances by a normal force that changes their trajectories and increases their momentum, and if they lack a sufficient component of motion perpendicular to the surface, they are subject to total internal reflection. If such a particle could be created, it should receive extra momentum by interaction with the refractive vacuum, and the momentum would be recovered when the particle interacts with some distant object.


Paul Titze January 2, 2017 at 21:15

Hi Marc,

Thanks for the review. My thoughts on these “EmDrive, EM Space Drive; Mach Effect Thruster, Mach-Lorentz” or X drives is that there is no new physics here and “the dynamic behavior of the thrust stand must be more thouroughly understood before reaching firm conclusions”.

Since NASA stopped the Breakthrough Propulsion Physics (BPP) program, I predicted this would happen as there is now no longer an impartial, rigorous organisation with the technical, scientific and engineering means to check new BPP claims. As a result we ended up now with the problem of:

“How many inadequate experiments and over how many years does it take before we change our tactics?”

So I think NASA did a great dis-service to humanity by stopping the BPP program however I’m not a United States tax payer so I’m not really qualified to criticise how they spend their money. Unfortunetly relying on people’s donations etc to verify regular BPP claims just ain’t going to cut it.

Cheers, Paul Titze.


Steven Torry Rappolee January 3, 2017 at 1:15

this is a remarkable discovery that such small amounts of power from my washing machine motor can be transmitted such a vast distance……
The protocol must be to remove this device further from my machine to see if the effect vanishes ……. :)


Bill Christie January 3, 2017 at 5:30

Traction in space would enable massless rockets:
A light wave or photon is transmitted through space and thus interacts with space with transverse changes in electric and magnetic fields. In order to exist, the photon must move forward through the electromagnetic field such that changes in in both the electrical and magnetic fields induce each other. The photon thus has traction in space. If a photon can be brought into rotation then it will create a positron and electron. Thus matter will have traction in space as it is indeed transmitted through space as energy. This traction might allow for the extension of Newton’s 3rd law for EM Drives, Mach Effect or “massless rockets”. The EM Space Propeller is based on such traction.


DJ Kaplan January 3, 2017 at 13:21

Thank you for not taking this gee-whiz technology at face value! I know it’s tempting to hope for such a miracle, but guess what, that’s not what we call science.


RobFlores January 3, 2017 at 19:59

For the sake of keeping an open mind, let us assume that the EM-drive
White, Et all, is a new effect. Let assume it is a either a field or particle
effect previously not known or suspected.
If real, the effect seems tiny. If the power/thrust ratio cannot
be improved via differing configuration/scaling, Then it is only useful
where solar power has high efficiency. Certainly not beyond Mars since the
mass of the solar array begins to make the M/T ratio even worse. Use Nuclear reactor some would say. I say there are heck of a lot more efficient propulsion designs for Nuke Reactors than EM drives.
The Standard Model survived the Neutrino actually having a tiny mass.
it maybe the case that EM drive has tapped into unknown phenomenon.
But if the effects are tiny, I think the Standard model is safe.


AlainCo January 4, 2017 at 3:12

Your reasoning is psychologically very common.
The first reaction to an anomaly is to ignore it, then blame the experiment, then accuse experimenter of bias, then of fraud, and when data are quite good, people says “there is no application”…

You should fight against this easy excuse. an anomaly is an anomaly and open an unknown door in the theory that an engineer can exploit to an unexpected amplitude. the few W of radium anomalous heat above chemistry, the few hundred of watt of Fermi pile, have led a route to Hiroshima and 80% of France electric production..

Anyway this article is very good in reminding we are far from having confirmed the phenomenon, because the many confirmations looks (?) either thin like Eagleworks, or quite private…

I just hope this critic will be published as an answer to the paper.
If no such critic is published as an answer, you can consider either that it is BS critic, or that academic method is broken today.

This is the current question … Publish an answer to the paper, to which EW can answer, or admit EmDrive is confirmed, or admit academic science is dead and something that works have to be created to review such anomalies.


ljk January 4, 2017 at 10:16

I love it when people resort to the Anti-Establishment argument, as it usually means they have little or nothing of real scientific substance to offer, they just support their cause with a religious ferver – ESPECIALLY if it goes against the Establishment. Everyone wants to be the next Galileo/Einstein.

Yes, attack the person, not set up a cognizant scientific rebuttal. What is your background in this matter, or are you going to tell me it doesn’t matter or some other weak excuse? When you can offer something better than a few references from some obscure and questionable journals, then the professionals will take you seriously. Otherwise you’re just another fringe type trying to be different for the sake of being different, or an outright troll.

Academic science is not dead, as you apparently seem to wish it were. It needs adjustment and revision like all human institutions, at least the ones that aren’t the equivalent of cults. Science at its core still works, despite the desires of those who are clearly not its friends.


william f collins January 6, 2017 at 16:59

I enjoyed this latest Centauri Dreams entry along with the many comments which followed. While I have been very doubtful regarding the possibility of FTL/Warp Drives / Wormholes for “fast” interstellar travel, I do hope that there is a development of a propulsion or propulsion-less technology that would provide for fast interplanetary travel across the Solar System. I would hope that experiments to test the EM Drive, Light Sails, Nuclear Fusion (Cold or Hot) , Ion Drive , etc. could be conducted in Space (outside of Earth’s atmosphere). An economically feasible means of traveling in the solar system would turn our civilization into an interplanetary one – for a start


Doug Dwyer January 7, 2017 at 11:14

There are enough possibilities without invoking magic which it may need. Our technology was magic 200 years ago.


Michael January 7, 2017 at 14:57

I think the only thing on this rig worth anything is the radiator…and I like even numbers.


J. Jason Wentworth January 11, 2017 at 17:16

From what I’ve read about the cold fusion experiments (which is by no means exhaustive), positive results *were* reproduced by some other researchers (other than cold fusion’s initial claimants), but not consistently or by all of them. While this may mean that cold fusion wasn’t actually created (the heat that was produced possibly being due to something else), it might also mean that cold fusion *did* occur in those cases, but that some as-yet-undetermined factor or factors (a lack or perhaps excess of something in the experiment set-ups) resulted in the negative results of some of the researchers’ experiments (even “hot fusion” laboratory experiments have sometimes had “hit or miss” results).


Michael January 13, 2017 at 14:06

As I believe they where looking for neutrons, I hope they weren’t using the same neutron detector…


rfmwguy January 20, 2017 at 21:29

I put together a quick slideshow of my EmDrive design, build and test efforts in the Spring and Summer of 2016. It was a humble one-man experiment at home but hope it’s enjoyable:


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