Cannae/EmDrive

[perk]

Thanks, i didn't know that, but looking at Eq. 19 its quite obviously the way you describe http://arxiv.org/pdf/gr-qc/0009013v1.pdf

[Rakaydos]

You need to put in enough energy to produce a particle-antiparticle pair. That is a Lot of energy.

Otherwise, particle stays virtual, and must interact with something else.

So what happens if you dont put in enough energy, is my question.

[cpast]

You can't just send it to orbit and turn it on; it's extremely expensive to get the precision equipment you need into space, and you have to work out how you're going to even measure what you want to measure. Running experiments in space is very much not trivial, and far less flexible than on Earth (as you're limited to what you sent up, instead of being able to fairly easily reconfigure stuff). Validation in orbit is something that's basically only worth doing once you're pretty sure you understand what it'll do (so that you know what measurement equipment is needed). It's a safe bet most "BS" experiments you've heard of (like geckos mating) are actually rather more complicated than reported in the media, and the groups launching them managed to convince funders (or a space agency, which works like convincing funders) that the experiment was worth doing in space and the necessary preparation had been done (so they were pretty sure they'd get good data, instead of the experiment just failing [i.e. failing to produce any decent data, not just not giving the expected result] and needing to be redone). It would not be cheap to test this in orbit; probably significantly more expensive than an ISS experiment.

[K^2]

So what happens if you dont put in enough energy, is my question.

Nothing. But a virtual particle can't propagate freely, so if you don't give it that energy, it can only go from point A to point B, and not very far at that.

[Rakaydos]

Nothing. But a virtual particle can't propagate freely, so if you don't give it that energy, it can only go from point A to point B, and not very far at that.

So if you give it a little energy, but not enough, it vanishes with the energy?

...I get the feeling theres something being left out.

[K^2]

Virtual particle vanishes when it interacts with something else, potentially, another virtual particle^*. That energy will be transferred to that particle. If it's virtual, it will then be transferred to another particle, and so on, until it ends up being transferred to a real particle. The probability of that entire chain of events taking place decreases with the length of the chain and the distance.

^* There are other conservation laws at play here as well. A virtual electron will need a virtual positron at that vertex, because just like energy and momentum, virtual particles conserve things like charge and lepton number.

[Rakaydos]

That sounds interesting. I remember hearing that people working on quantum computing were working on ways of "gaming the system" to get good probabilities out of statistically random events... is it plausable to "improve the odds" of a virtual particle chain in the same way?

[K^2]

Within reason, probably. But it would require a medium. You can't really do much about it in vacuum by definition.

By the way, to have a better mental picture of how such things work, a classical example of such, "stacking the odds," is Brewster's Angle.

[Technical Ben]

So your argument is that since there is only one explanation, then that one explanation must be the accepted explanation for how it works, irrelevant of how silly the explanation is?! HAHA. Ok. So, I propose that the EM drive works because there is an invisible pink unicorn hitched to the front of it that pulls it. The more electric current that flows, the stronger the unicorn is shocked and the harder it tries to get away.

There. Now with this unicorn drive hypothesis, you have a strong contender to the virtual particle quantum plasma mumbo-jumbo, because according to your rules, being stupid does not disqualify a hypothesis from consideration.

Someone beat me to the alternative theory... I'll never get my paper published or taken seriously in Unicorn University now.

Sadly, it seems 99% of people have mistaken the direction of scientific discovery.

It goes:

Make observation -> Make theory -> make new observation to see if it fits the theory.

If it does, then your theory is more than likely correct.

(ok I skipped some steps, but am simplifying it)

Sadly, many just "Make theory" -> "Does this theory match our theoretical results we just imagined?" with zero observations, they always hit their imaginary observations every time. "It's got to be virtual particles, because that's all we can imagine it to be".

PS

For example a laser resonator. You have a standing em-wave in them. The em-intensity in the middle of the resonator is in most cases much greater than to the edges of the resonator (near the mirrors). If that would create any thrust, like described for the em-drive, it would slightly squish or streach the resonator. We would have definetly be able to measure that, because the coherence length of the laser-light is easily measurable and dependent on the length of the resonator. We would always be wondering why the coherence length is always slightly different than expected. That question would come up in almost every single laser, so we would have surly noticed it.

Interestingly, that's how I'd do an alternate universe story for Sci-Fi with FTL and/or antigrav etc. One tiny measurement always there that they suddenly find was staring them in the face.

However, in the real world, we get perfect results every time, Note, as mentioned above with observations Einstein had to have an observation of mercury's orbit to get an inclination of the "problem", and had to get an observation to confirm his predictions of relativity (during an eclipse IIRC).

Here we only have the first observation. Without additional ones, we have zero chance/probability/knowledge of what underlying theory/mechanism is at work.

Edited February 23, 2015 by Technical Ben

[PB666]

Someone beat me to the alternative theory... I'll never get my paper published or taken seriously in Unicorn University now.

Sadly, it seems 99% of people have mistaken the direction of scientific discovery.

It goes:

Make observation -> Make theory -> make new observation to see if it fits the theory.

If it does, then your theory is more than likely correct.

This is a classic paper tiger argument.

The proponents and most of the opponents to the VP explanation think more testing is needed. The only thing I could gather for a couple of opponents is that they don't want to see it used in space on craft with humans on board. So as far as I see 100% of folks here want it tested more with more test parameters. So 99% of people have not mistaken the direction, at least here, 0% have.

I'll remind you of a once famous scientist referring to one of the basic legs of quantum physics said "god does not play dice with the universe". It turns out that he may be wrong on two accounts in one statement.

[Technical Ben]

Sorry, but there are levels of imagination at what people are saying way above a mistake there. No one has suggested what you propose.

The comments have been that costs prohibit a space test. No comments on human testing.

The comments have been that the data against this drive is massive, thus it requires likewise to prove it works. It then requires another massive amount of data to know how it works.

Your quote of Einstein is not fitting for the subject, logical argument, structure of your sentence or the purpose you are using it for. As chance or "dice" have no impact on the requirements of virtual particles meeting other observed laws (conservation of energy etc).

[magnemoe]

Someone beat me to the alternative theory... I'll never get my paper published or taken seriously in Unicorn University now.

Sadly, it seems 99% of people have mistaken the direction of scientific discovery.

It goes:

Make observation -> Make theory -> make new observation to see if it fits the theory.

If it does, then your theory is more than likely correct.

(ok I skipped some steps, but am simplifying it)

Sadly, many just "Make theory" -> "Does this theory match our theoretical results we just imagined?" with zero observations, they always hit their imaginary observations every time. "It's got to be virtual particles, because that's all we can imagine it to be".

PS

Interestingly, that's how I'd do an alternate universe story for Sci-Fi with FTL and/or antigrav etc. One tiny measurement always there that they suddenly find was staring them in the face.

However, in the real world, we get perfect results every time, Note, as mentioned above with observations Einstein had to have an observation of mercury's orbit to get an inclination of the "problem", and had to get an observation to confirm his predictions of relativity (during an eclipse IIRC).

Here we only have the first observation. Without additional ones, we have zero chance/probability/knowledge of what underlying theory/mechanism is at work.

Yes, often because observations don't match the theory, or its some problems with the existing theory.

Note that your new theory has to be good to be accepted, an theory who only solve half of the problem will have problem getting accepted.

Was Mercury the background for Einsteins theory, I thought it was ether and how it looked like light has the same speed in all directions.

(again astronomy, easiest way to measure speed of light without fast electronic is the movement of Jupiter's moons. Its an 14 minutes delay depending on Earth is on the same side of sun as Jupiter or not)

Let us assume that the speed of light is constant, this will have other effects called relativity. This solved a lot of problems and later experiments confirmed this.

[rtxoff]

This is a classic paper tiger argument.

The proponents and most of the opponents to the VP explanation think more testing is needed. The only thing I could gather for a couple of opponents is that they don't want to see it used in space on craft with humans on board. So as far as I see 100% of folks here want it tested more with more test parameters. So 99% of people have not mistaken the direction, at least here, 0% have.

I'll remind you of a once famous scientist referring to one of the basic legs of quantum physics said "god does not play dice with the universe". It turns out that he may be wrong on two accounts in one statement.

It would be better to actually say something relevant to the Cannae/EM drive then speculating about what people here on the forum would like to see or not. However i don't think there is anything relevant left to say beside wait for further test results. I would really like to see that Cannae/EM drive actually working, however i am very well aware that it could be an dead end and that we yet failed to see something that could explain the test results so far.

[Mazon Del]

From reading the thread that has been linked to a few times, they are actually in an annoying spot of trouble. Their current funding basically ends the first week of March unless they can get the test article to produce thrust over 100 micro-Newtons in order to pass it to the next lab for verification. Now this doesn't mean that the funding is cut entirely, but that it will drop low enough that one of the physicists they brought out of retirement 4 years ago just to work on this project will be unable to continue working. Though he has a home lab that he was working out of on this exact technology before NASA snagged him again and he says that if it happens, he'll just jump back to that.

It sounds like they are attempting to change out the radio emitter for one of a much higher frequency in the hopes of kicking it up a couple notches. They are looking at something in the gigahertz range I believe.

Additionally, they are discussing the possibility from some test data that the effect might be casimir related. (WARNING: Not a physicist, this description will not be as good as ones on the thread.) They note this because of the following observations. When in vacuum (with air inside the engine, but not outside) the engine works. When in vacuum (but no air inside the engine), the thrust is drastically reduced (but not to zero). When in vacuum (inside and out), but they have a block of PTFE snugged up near the emitter on the inside of the engine, the thrust is comparable with when the air is inside. When in vacuum (outside) and they have the block of PTFE AND air inside, they get the best performance. If the engine is in vacuum, but has air inside, and there is a small gap between the block of PTFE and the emitter, they see reduced performance. Now, they have checked to make sure that none of this air or matter is leaving the closed engine area to ensure this. So one of the theories is that whatever effect is going on inside the engine might be utilizing the Cassimir effect and that the denser material of the PTFE is better at this than the air itself was.

There was a humorous anecdote that during one of the tests the nylon bolt (on the inside of the engine) used to hold the PTFE broke and so this several kilogram block of plastic fell down to the inside of the chamber. Considering the system was designed to measure in the micro-Newton range, this was like a magnitude 9 earthquake as far as their sensor was concerned. This event is actually what tipped them off to the fact that the thrust was being influenced by the presence of the PTFE.

[SuperFastJellyfish]

Dr. Rodal did an overview of what has been done and what has been ruled out by people(Ph.D.'s and amateurs alike) in those two threads for those who don't have the time to go through it:

This thread has resulted in great synergy between NSF contributors and Paul March at NASA, and I wanted to take this opportunity to name a partial list of accomplishments and thank everybody that has contributed -including a few humble persons who privately asked me not to list their numerous valuable contributions -(please forgive me if I am missing important contributions, tell me what I missed, or if you disagree, what I should correct):

Consideration was made of whether the experimental measurements of thrust force were the result of an artifact. Dr. Rodal, one of the contributors, solved the nonlinear, fully coupled system of differential equations (including magnetic damping) of an inverted torque pendulum with Mathematica to examine whether parasitic modes or nonlinear dynamics could be involved. Chaotic motion and strange attractors were also examined. Comparison with the experimental results showed that none of these nonlinear dynamics effects were involved in the experimental measurements at NASA Eagleworks, and therefore a nonlinear dynamics cause was eliminated. Dr. Rodal (in the US) also conducted Power Spectral Density and Autocorrelation analysis of NASA's experimental data and worked with another contributor, @frobnicat, (in France) to examine the dynamics of the experimental response. They concluded that indeed NASA's experimental measurements exhibited the expected response of NASA's torque pendulum as excited by an initial thrust force impulse followed by a thrust force response during the 30 to 40 sec length of the experiments. Dr. Rodal analyzed possible thermal instability (thermal buckling of the flat ends) as a cause for the measured thrust and reported this at NSF and at ResearchGate (https://www.researchgate.net/publication/268804028_NASA%27S_MICROWAVE_PROPELLANT-LESS_THRUSTER_ANOMALOUS_RESULTS_CONSIDERATION_OF_A_THERMO-MECHANICAL_EFFECT). A thermo-mechanical effect (thermal buckling) is shown that occurs in less than 1 second (for the copper thickness employed for the microwave cavity), with a temperature increase of a degree C or less and that results in forces of the same magnitude as reportedly measured by NASA. Moreover, this thermal instability produces forces in the same direction as measured, and it will occur in a vacuum (since the heating can be due either to induction heating from the axial magnetic field in a TE mode or resistive heating due to the axial electric field in a TM mode). However, this effect can only explain the initial impulsive force and cannot explain the longer 30 to 40 second measured force. Thus the thrust force measured for up to 40 second is not nullified by this explanation either.

Thermal expansion effect as posited by a team from Oak Ridge National Labs for another propellant-less set of experiments was also eliminated as a possible source by the NSF contributors because it would result in forces in the complete opposite direction as the forces measured by NASA.

One of the participants in the NSF forum is Dr. McCulloch (an academic from the UK), who independently developed a tentative theoretical explanation for the EM Drive: assuming that photons have inertial mass, which is caused by Unruh radiation, whose wavelengths must fit inside the EM Drive cone, more Unruh waves fit in at the wide end of the EM Drive, so photons traveling along the axis would always gain mass going towards the wide end and lose it going the other way. This is equivalent to expelling mass towards the wide end, so the EM Drive must move towards its narrow end to conserve momentum. This agrees with the (forward) direction of movement of the EM Drive in reported NASA experiments. Dr. McCulloch derived a simple formula to predict the thrust force and published his theory in the journal Progress in Physics (http://www.ptep-online.com/index_files/2015/PP-40-15.PDF). In his blog and published paper he acknowledges the help from NSF participants (@aero, and @Fornaro) in estimating the geometrical dimensions of the EM Drives tested in the US, UK, and China.

Another participant in the NSF forum, @Notsosureofit (Ph.D. Physics) developed and posted an analysis of the EM Drive thrust considering an accelerating frame of reference caused by a dispersive cavity resonator and obtained a formula to predict the thrust of the EM Drive that takes into account the electromagnetic mode shape of the EM Drive (unlike the formulas of McCulloch and Shawyer that do not explicitly include mode shape information).

@frobnicat and Dr. Rodal conducted statistical analyses of the experimental data. @frobnicat wrote a computer program that included hundreds of possible combinations of the experimental parameters (such as power input, frequency, Q (quality factor of resonance), geometrical dimensions, etc.) to the first few powers. Interestingly the best fitting formulas were similar to the theoretically derived formula by Notsosureofit and also McCulloch's formula.

Astrophysicist TMEubanks examined whether the EM Drive could be coupling to the (Dark Matter) Axion background. He concluded that this is very unlikely (by up to 20 orders of magnitude) due to the findings of the Axion Dark-Matter experiment, looking for yoctowatts (10^-24) of RF power in the 2 - 20 micro-eV range, precisely the range of the EM Drive, by tuning the cavity's resonant frequency to the axion mass. There is simply no way that the Drive is coupling to the axion background - the ADMX would see a whopping signal.

Dr. Rodal obtained an exact solution for the electromagnetic modes in a cavity with similar geometry as the NASA's EM Drive using Mathematica and the theory of spherical waves developed by the Russian/American scientist Schelnukoff. The resulting equations are very similar to the ones posted by Greg Egan (http://gregegan.customer.netspace.net.au/SCIENCE/Cavity/Cavity.html) . Dr. Rodal calculated the natural frequency for electromagnetic modes tested in the EM Drive, from this exact solution, to compare with the NASA predictions by Frank Davies NASA/JSC/EP5 using Finite Element Analysis with the computer code COMSOL. The exact solution results calculated by Dr. Rodal at the NSF forum are only 1% different from the NASA calculations using COMSOL. This confirms the validity of NASA's COMSOL analysis, and that the finite element mesh used was fine enough to result in predicted frequencies that are less than 1% from the exact solution, hence confidence can be had on those calculations. The validity of NASA's COMSOL calculations has been simultaneously confirmed by experimental comparison with the IR thermal camera image produced for mode shape TM212.

NSF member @aero is using MIT's Finite Difference computer code MEEP to calculate the force produced by evanescent waves escaping from the EM Drive and interacting with the stainless steel vacuum chamber. This work is in progress.

Despite considerable effort at NSF to dismiss the reported thrust as an artifact the EM Drive results have yet to be falsified. After consistent reports of thrust measurements from EM Drive experiments in the US, UK, and China, at thrust levels several thousand times in excess of a photon rocket, and now under hard vacuum conditions, the question of where the thrust is coming from deserves serious inquiry.

[K^2]

Mazon Del, is the thrust in Vacuum-Vacuum case reduced to photon drive? Because this is a hell of an elephant in the room if the thruster only works when filled with gas, or PTFE, which will produce F2 gas under test conditions, which is an even better propellant than air for an ion drive.

[Nuke]

i seem to recall reading about another capacitive based reactionless engine (operating off of the Woodward effect) where the dielectric within a capacitor would undergo mass fluctuations, and by syncing this up with a mechanical oscillation you could produce thrust. that big hunk of plastic could be operating as a dielectric in a capacitor (especially with all that copper around it).

[SuperFastJellyfish]

Mazon Del, is the thrust in Vacuum-Vacuum case reduced to photon drive? Because this is a hell of an elephant in the room if the thruster only works when filled with gas, or PTFE, which will produce F2 gas under test conditions, which is an even better propellant than air for an ion drive.

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1331689#msg1331689

1) The first time (to my knowledge) that an EM Drive is tested under hard vacuum, with experimentally confirmed thrust (at a thrust/PowerInput level amply exceeding the one for a photon rocket).

http://forum.nasaspaceflight.com/index.php?topic=36313.msg1330854#msg1330854

Thust/Power= 1 uN per Watt

[K^2]

Mazon Del's post implies hard vacuum outside, but potentially either air or gas-generating polymer inside. His post states that thrust drops dramatically in the vacuum-vacuum case.

[sgt_flyer]

Mmh mazon del specified that they checked that none of the contents of the engine got out of it- though it would be better if they gave more infos on how they confirmed that they did not lost anything (they don't tell either if the PTFE block was altered in any way by the engine's running - only info they gave was that the block fell inside the engine during one of the experiments (wonder how it did - if it was the engine's em emmissions that disturbed the way they anchored the block - or if they just did not strap it correctly)

For sure, it could lead to think that some atoms / molecules managed to seep through the engine's body somehow, generating the additional thrust - so without more infos on the comparative tests, it'll be hard to determine something useful on our hand from that (here, it seems that they are at the phase 'let's throw anything we can think of in the chamber, to see if it allow us to generate the thrust forces we need to keep our funding...)

Edited February 25, 2015 by sgt_flyer

[K^2]

The mass defect to get the few uN they are measuring at relevant voltages would be miniscule. There is no way they could have verified it. Not without monitoring the vacuum chamber with mass-spec, or better yet, using radioactive tracers.

That's why I'm saying that what they should be doing are far more tests in well controlled environment on Earth. Not wasting money launching this junk into space.

As it stands, this is looking a lot like the story with ionocraft lifter.

Edited February 25, 2015 by K^2

[SuperFastJellyfish]

The mass defect to get the few uN they are measuring at relevant voltages would be miniscule. There is no way they could have verified it. Not without monitoring the vacuum chamber with mass-spec, or better yet, using radioactive tracers.

That's why I'm saying that what they should be doing are far more tests in well controlled environment on Earth. Not wasting money launching this junk into space.

As it stands, this is looking a lot like the story with ionocraft lifter.

I'm fairly certain that the image I linked to is a vacuum-vacuum run, but I could be mistaken. 78uN sustained from 50W. Whether that's the dielectric outgassing or not, I can't say.

Also, who's launching one of these into space? They can't even get their sister NASA labs to test one of these things with their superior testing equipment. This is essentially a few guys in a lab with barely any money.

Mr. March also had this to say which may address your concerns:

http://http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329225#msg1329225

Next, measureable thrust was not observed when the PE or Teflon discs were removed from the copper frustum while in air with up to 30W of RF using our Mini-Circuit RF amp. As to why the vacuum test were observing less thrust than in air tests. please note the difference in the RF amps there were driving each test series. The 30W Mini-Circuit Class-A RF amp was used for the in-air series reported in the 2014 JPC paper, whereas a 100W EMPower Class-A/B RF amplifier was used in the vacuum tests to date. So how could a less powerful RF amp produce more thrust than a more powerful one? Now think about what the driven magnitude of the time rate of change of the energy in the vacuum state might bring to this question...

Poor controls, unfortunately.

[Bill Phil]

So "It works and we don't know why" is an unacceptable statement?

[CptRichardson]

I'm fairly certain that the image I linked to is a vacuum-vacuum run, but I could be mistaken. 78uN sustained from 50W. Whether that's the dielectric outgassing or not, I can't say.

Also, who's launching one of these into space? They can't even get their sister NASA labs to test one of these things with their superior testing equipment. This is essentially a few guys in a lab with barely any money.

Mr. March also had this to say which may address your concerns:

http://http://forum.nasaspaceflight.com/index.php?topic=36313.msg1329225#msg1329225

Poor controls, unfortunately.

They can't get it tested because they can't put enough power through it under test conditions to get a projected result that will appear on the other lab's testing equipment. They've specifically made note that before they can send it on to the other labs (Which ARE looking to test this out) they have to get somewhere between an input power of 100 watts and 125 watts. Right now, they can only manage short bursts of 50 watts before the power burns out.

[SuperFastJellyfish]

They can't get it tested because they can't put enough power through it under test conditions to get a projected result that will appear on the other lab's testing equipment. They've specifically made note that before they can send it on to the other labs (Which ARE looking to test this out) they have to get somewhere between an input power of 100 watts and 125 watts. Right now, they can only manage short bursts of 50 watts before the power burns out.

Thanks for the clarification.