To Mars in 70 days: Expert discusses NASA's study of paradoxical EM propulsion drive

December 7, 2016 by Colin Poitras
EM Drive in forward thrust configuration. Credit: NASA Photo

After months of speculation and rumor, NASA has finally released its long-awaited research paper on the controversial EM Drive propulsion system. The paper was recently published in the American Institute of Aeronautics and Astronautics' peer-reviewed Journal of Propulsion and Power. If the electromagnetic technology proves sound, it could radically change the way humans travel in space, opening up the possibility of journeys to Mars in just 70 days. But there is no shortage of skeptics who are adamant that the drive is more science fiction than science fact. Critics are quick to point out that the drive violates one of the fundamental laws of physics, namely: for every action, there is an equal and opposite reaction. With the science world abuzz in light of the recent developments, UConn Today called on engineering professor Brice Cassenti, an expert in advanced propulsion systems, to help us understand what's happening.

Q. What is the EM Drive propulsion system and what makes it so unique?

A. An EM Drive uses electromagnetic waves (e.g., radar) to produce thrust, which is obviously something that is needed for a rocket engine. The drive consists of a truncated conical copper shell with a plastic (polyethylene) disc covering the narrow end of the truncated cone. An electromagnetic wave is induced inside the copper shell in the same manner as a microwave oven. The propulsion system is unique because the device uses no traditional fuels or propellants. Instead, in the simplest of terms, the bounce around inside the cone in a way that some say causes propulsion. In the NASA tests, a thrust of 1.2 millinewtons per kilowatt was reported for an EM Drive activated in a vacuum, which is a very, very small – but noticeable – movement. By not relying on traditional fuels, the EM Drive would make spacecrafts lighter, and eliminate the need for massive amounts of fuel currently required to launch a spacecraft to far-off destinations.

Q. What's behind all the skepticism about the EM Drive, and what's your take on all of this?

A. Although the EM Drive appeared to create thrust in these tests, there was no mass or particles of any kind expelled during the process. This is a violation of Newton's third law of motion, which says that for every action there is an equal and opposite reaction. Action and reaction is a direct result of the conservation of momentum. The violation of such a basic law as the conservation of momentum would invalidate much of the basis for all of physics as we know it. Hence, many scientists and engineers feel the thrust measurements reported for the EM Drive are due to experimental error. Adding to this is the fact that those who believe the results are valid do not yet have an experimentally or a theoretically plausible proven physical explanation. I personally believe that there is a mundane explanation for the results. For example, electric currents are heating components within the Drive that expand during the experiments, causing motion that would appear as a force. It is very difficult to remove such effects, although the authors of the journal article tried to remove not only these thermal effects but also many other possible sources for experimental errors. It is extremely difficult to know for sure that all of the possible sources for errors have been removed. The only sure method is to have a hypothesis (or theory) that can be tested independently.

Q. The fact that NASA's research has passed peer review is being heralded as a major step. What exactly does the peer approval mean in the context of ongoing research?

A. Peer review is important, since it means that other experts have reviewed the work, and the results are professional and important enough to distribute to others in the community. It does not mean, however, that the reviewers consider the results valid. A reviewer of the journal paper that I spoke with before the paper was submitted does not believe the results point to any new physics. But that person felt the results are puzzling enough to publish.

Q. If the EM Drive really does work, does this mean Newton was wrong and there are mysterious other aspects of physics that we still don't understand?

A. If the results are valid, it definitely points to . Newton's laws have already been shown not to apply at high relative speeds (where special relativity applies), in large gravitational fields, and with very small scale molecules. But Newton is still mostly right. There are certainly many aspects of physics that we do not understand. Some aspects are so mysterious that we don't even know where to begin!

Q. Everyone seems to be excited about the EM Drive being tested in space as the next step. What advantages are there to testing the device in space versus here on Earth?

A. If the EM drive is tested in space, then the acceleration could be directly measured, which would eliminate all of the confusion associated with force measurements. Space would provide an ideal vacuum, so the device would not have to be placed in a vacuum chamber, and it would provide a weightless environment, eliminating any need for a support (current tests rely on a balance arm so any resulting forces can be measured). But space missions are expensive – at a cost of $10,000 to launch one pound of material into orbit. It may be better to first try to experimentally find the cause for the thrust measurement, and only when the cost on the ground begins to approach the cost for an orbital mission should an experiment in space be performed.

Q. Is there anything else you would like to share about the EM Drive to help us understand?

A. No, but over my professional life I have seen several of these exciting experimental or theoretical results reported in peer-reviewed literature. So far only the reality of black holes has come through. So, based on my experience, the probability of this holding up under further analysis and testing appears slim. But it's not zero.

Explore further: Was physics really violated by EM drive in 'leaked' NASA paper?

More information: Harold White et al. Measurement of Impulsive Thrust from a Closed Radio-Frequency Cavity in Vacuum, Journal of Propulsion and Power (2016). DOI: 10.2514/1.B36120

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Reg Mundy
1 / 5 (13) Dec 07, 2016
If my theory on the nature of velocity and momentum is correct (see "The Situation of Gravity", free on Kindle) then movement is the alignment of tiny expanding gyroscope-like domains from which matter is formed. The speed of light is attained when all domains are perfectly aligned. Applying force to an object effectively aligns its domains, but as the number of domains aligned approaches 100% more force applied has no effect.
It may be that the EM drive is affecting alignment without recourse to an outside force - there are no other mechanisms known other than applying an external force (i.e. interaction with other matter) to effect domain alignment and therefore velocity and momentum.
BarryV
2.1 / 5 (7) Dec 07, 2016
As to theoretical basis for EM Drive, please google Hawking-Unruh Radiation; see 1998 paper "Hawking-Unruh Radiation and Radiation of a Uniformly Accelerated Charge" by Kirk T. McDonald; see 2016 paper "Testing quantised inertia on the emdrive" by M.E. McCulloch.
antialias_physorg
4.7 / 5 (12) Dec 07, 2016
Well, if the effect is something like exerting a push on vacuum fluctuations (virtual particle pairs) then there need not be a violation of the laws of motion (as mentioned in the link which leads to the full article. Good read).
This might be testable by having a Casimir force measurement setup behind/in front of the drive as it should create a vacuum fluctuation 'wake'.

On a side note: I don't think the argument that "space missions are expensive" is relevant, anymore. The setup does not seem to be dependent on the size of its components, so I could well see a miniature version housed inside a cube sat and sent up for testing for a couple of (tens of) thousand dollars. That's not too much of an investment to give this a go and see if it pans out.
javjav
5 / 5 (5) Dec 07, 2016
this thing is so small, light weight and easy to build that it worth testing it in space. They could make one in the ISS, attach a solar panel to it and throw it to space manually. Then see what happens.
TheGhostofOtto1923
3.5 / 5 (6) Dec 07, 2016
I could well see a miniature version housed inside a cube sat and sent up for testing
-And with a 10 sec google we find that Cannae is apparently about to test a cubesat in orbit

"roughly one-quarter of this shoebox-sized satellite will be taken up by the Cannae Drive, and they'll stay in orbit for at least six months: "The longer it stays in orbit, the more the satellite will show that it must be producing thrust without propellant"
(for the google-illiterate)

-also I seem to remember that this can be used to drive trains and ships. Can't find and source though.
shavera
3.1 / 5 (8) Dec 07, 2016
Experiment I'd like to see: Send up a cubesat with a flashlight pointed one way, and the em drive pointed the other. Power them both with the same level of power and see which way the object moves. If it balances thrust, then the EM-Drive is just a fancy EM cavity emitting radiation in a preferential direction. (which may be of too low a wavelength or something otherwise that isn't detected in ground experiments). If the flashlight is the higher thrust, then the whole point is moot anyway because we may as well power our rockets with flashlights and save all the trouble of magical mystery engines. Even if the EM-Drive is the larger thrust, it still doesn't necessarily rule out conventional physics explanations (it may be more efficient at converting power to directed EM radiation or some such thing), but as a functional matter, then go ahead and look at it as a useful technology.
antialias_physorg
5 / 5 (9) Dec 07, 2016
If the flashlight is the higher thrust, then the whole point is moot anyway because we may as well power our rockets with flashlights and save all the trouble of magical mystery engines.

Well, they say right there in their paper:
however, for missions with very large delta-v requirements, having a propellant consumption rate of zero could offset the higher power requirements. The 1.2  mN/kW performance parameter is over two orders of magnitude higher than other forms of "zero-propellant" propulsion, such as light sails, laser propulsion, and photon rockets having thrust-to-power levels in the 3.33–6.67  μN/kW


Whydening Gyre
3.7 / 5 (7) Dec 07, 2016
IF it works, Newtons law is still not being violated.
It would be more a matter of opposite reactions being slightly out of alignment (not 180)...
Thereby allowing for a little "traction".

And Reg.
Ponder my screen name for a bit...
eachus
1.5 / 5 (4) Dec 07, 2016
The article has a very wrong attitude about this experiment. When dark matter, dark energy, and the vacuum energy were unknown, this drive would require serious new physics to understand. But if there is an interaction with any of those three, physics is resolved--except that the dark matter investigators will want to tear it apart to see if it can be used to detect dark matter.

What is the probability that this drive does interact with one of those? Quite high for vacuum energy. It is very difficult (but not impossible!) to pull power from vacuum energy. However, if external energy is supplied (as it is here) and there is a net force acting on the virtual particles, everything works.

You might think that interacting with virtual particles is forbidden unless you supply enough energy to make them real. Not how it works. Virtual particles are indistinguishable from real particles over sufficiently short time periods.
Captain Stumpy
4.1 / 5 (13) Dec 07, 2016
@pseudoscience reg
If my theory on the nature of velocity and momentum is correct
1- it's not a theory, it's speculative at best, but considering the direct evidence falsifying it, it's a pseudoscience delusion

2- if you have any kind of reputable evidence you would be saying "read my peer reviewed journal" instead of "read my book that has no peer review or evidence"

3- quit trying to drum up publicity for your book when you can't get peer review for a paper
Whydening Gyre
3.8 / 5 (4) Dec 07, 2016
You might think that interacting with virtual particles is forbidden unless you supply enough energy to make them real. Not how it works. Virtual particles are indistinguishable from real particles over sufficiently short time periods.

Interesting posit.
Nik_2213
4 / 5 (1) Dec 07, 2016
Perhaps, at sufficiently high energy densities, there are 'weird' surface effects such that Einstein trumps Newton ?

But, agreed on the free-flying tests. Sadly, I don't think LEO cube-sats will have enough 'power to weight' to claw clear of 'baseline noise' due to drag, thermal emissions etc etc.

Should it work, albeit at micro-thrust, the recent development of lightweight, efficient MOSFET transistors that can replace chunky, clunky trad magnetrons in microwave ovens may help...
gkam
3 / 5 (8) Dec 07, 2016
The optimist in me says "hooray!", but experience is whispering that it's more like N-Rays.
LED_Guy
5 / 5 (3) Dec 07, 2016
The hype about this article is wrong. Solar panels in near earth orbit can deliver 300W/kg.

This unit generates 1 mN/kW. Do the math and if you ignore the weight of the thruster (very large array) you can accelerate at 0.0003 m/sec^2. That's about 0.00003 g. Sunlight on the solar panels of a spacecraft are likely to generate more thrust.

The thrust works out to 1 MW/N and you need 100's to 1000's of N to move a spacecraft carrying humans. Get a gigaWatt level power supply into space . . .

It will be an interesting paper and revolutionary if it passes muster (remember supraluminal neutrinos?), but it needs a factor of 1000 improvement before it has a chance to change space travel.
Mark Thomas
2 / 5 (4) Dec 07, 2016
It will never work in space.

This appears to be an uneven thermal effect that is probably throwing off the balance in the test setup. If it did work, you would also have to explain how it stores energy and releases it slowly in a brand new way. For example, when the power is shut off and there are no microwaves remaining in the cavity, the "thrust" does not immediately end, it very slowly decreases in a curve that looks a lot like heat dissipation.

Alternatively, how about developing technology we know that works, like nuclear thermal rocket engines that once produced as much as 4 gigawatts of power for 12 minutes.

https://en.wikipe...l_rocket
Mark Thomas
1.8 / 5 (4) Dec 07, 2016
"Well, if the effect is something like exerting a push on vacuum fluctuations . . . then there need not be a violation of the laws of motion"

Exactly how would momentum be transferred that way? A microwave leaves the magnetron, travels some distance, interacts with a virtual particle pair, then what? How is momentum transferred back to the EM drive?

How about if the microwave QM tunneled through the flat side of the cone and caused a regular stray air molecule in the partial vacuum, or even half of a virtual particle pair, to impact the flat side of the cone, thereby transferring momentum. That might work, but there just isn't much to push against. The question becomes how much of the thrust is due to residual air molecules in the test apparatus and how much is due to virtual particles? I think you will find almost all the thrust is due to air molecules, even under this concept, which may be wrong.
Joe-Pop
4.2 / 5 (9) Dec 07, 2016
Professor Cassenti stated that in his experience only the reality of black holes had lived up to the excitement it generated. I would offer several other equally surprising developments including the reality of continental drift, the reality of the Bretz floods and the reality of metamaterials with negative refractive index. All of these were initially dismissed because they violated accepted principles but are now accepted. Metamaterials, in particular, were deemed impossible when first reported but are now the basis for disruptive technologies. Certainly a violation of Newton's Third Law is an extraordinary claim and requires extraordinary proof but, if true, it will have extraordinary consequences. I am excited to see how this story ends.
antialias_physorg
4.2 / 5 (5) Dec 07, 2016
Sunlight on the solar panels of a spacecraft are likely to generate more thrust.

The point would not be to accelerate the cubesat, but to have the acceleration measurement apparatus inside the cubesat in an environment that is isolated from external factors as much as possible (traffic/wind/wave-seismic activity, gravity, imperfect vacuum, etc. )


Exactly how would momentum be transferred that way? A microwave leaves the magnetron, travels some distance, interacts with a virtual particle pair, then what? How is momentum transferred back to the EM drive?

Just speculating here: If that is the mechanism then the microwave photon will lose some impulse due to the interaction (i.e. will shift in wavelength to a lower one). Which in turn will mean that upon reflecting from the interior wall of the cavity it will exert less force. This presupposes that there is a 'favored direction' for interaction with the virtual particle pairs.
Mark Thomas
2.3 / 5 (3) Dec 07, 2016
AAP, points for creativity, but I still don't think it would produce anything practical. Your thrust is the difference in energy of the photons before and after interaction with a virtual particle pair. Ignoring the 'favored direction' assumption (which I believe would also be new physics), wouldn't it be more effective to simply open up the side of the cone opposite of the magnetron so that the unaffected microwaves, your lower frequency light, and maybe your now real virtual particles, all simply leak out the same end providing maximum thrust?
Andrew Palfreyman
4 / 5 (4) Dec 07, 2016
The goal of a space-based test is to demonstrate performance in Newtons per Watt that exceeds that of a photon rocket by a sizeable margin. Mundane sources of space-based thrust may be due to asymmetric thermal emission, as was observed with the Pioneer Anomaly.
antialias_physorg
4 / 5 (4) Dec 07, 2016
wouldn't it be more effective to simply open up the side of the cone opposite of the magnetron so that the unaffected microwaves,

I dunno. As they say in their paper: the effect is bigger than doing just that, so there has to be something else at work. 'pressure differentials' between places where virtual particle pairs get displaced? At this point it's basically anyone's guess.

First thing will be independent verification, though. But that shouldn't take too long.
tesschris
Dec 07, 2016
This comment has been removed by a moderator.
eachus
not rated yet Dec 07, 2016
Just speculating here: If that is the mechanism then the microwave photon will lose some impulse due to the interaction (i.e. will shift in wavelength to a lower one). Which in turn will mean that upon reflecting from the interior wall of the cavity it will exert less force. This presupposes that there is a 'favored direction' for interaction with the virtual particle pairs.


The favored direction is not hard to explain either. Imagine that the microwaves interact with virtual protons and electrons. Actually, you can calculate that given the EM fields inside the device. Some of these particles bounce off the truncated cone toward the rear of the device. Before they get there, they return to the quantum foam. (When the particle vanishes it transfers its state to the local vacuum, its state becomes part of the state of the point at which it vanishes. This state is instantly split between new virtual particles along with the rest of the state.)
eachus
5 / 5 (2) Dec 07, 2016
What makes this such an interesting device? Momentum which you are trying to change with any existing rocket or space drive is mv. To get more thrust, increase the mass ejected or reflected, or the velocity at which it leaves. But energy is mv2, so to eject matter at a higher speed, the power required goes up as the square of the speed. For light, or microwaves, v = c so you need lots of power for a photon drive.

If this drive really is bouncing virtual particles off the truncated cone, the energy in each particle will be the same, but the velocity will be much smaller. This means more thrust for a given amount of power. Can this device be optimized to produce lots more thrust for the same power? Almost certainly.

If this is how the device works though, expect power loss at high speeds, say v = c/2. So it will at best be a very nice gadget for roaming around the solar system, and maybe a few unmanned missions to nearby stars.
Reg Mundy
1 / 5 (3) Dec 07, 2016
@Widening Gob
And Reg.
Ponder my screen name for a bit...

Yes, I have done. It's very stupid, isn't it? My version is a definite improvement.
javjav
5 / 5 (2) Dec 07, 2016
This Newton law is too old and the fact is that it has never been demostrated. It just "seems to work" , but it could be just that we have not found counter examples until know. Think about another famous law, the law of conservation of energy. It is violated by dark energy all the time, isn't it?
Mimath224
3.7 / 5 (3) Dec 07, 2016
I am in agreement with antialias_physorg, shavera etc if only from a basic layman's point of view. Basically, anything that moves has the potential to move something else and on the EM level the photoelectric effect comes to mind. My thought is if the self undulating property of a photon is not considered a violation of Newton's laws then I don't see how an EM drive would. My simplistic idea is that the EM would have a 'action/reaction' with the equipment but perhaps so small as to be undetectable. My question would be that the EM drive needs to produce enough effect to overcome this. A very simple view I know, but I have said many times on this forum that I have a lot of confidence in the scientific community and in this case if is proved, no matter how slightly, in the future EM drive replace other methods. Keep doing with the experiments, guys, this is way to go!
Moebius
4 / 5 (4) Dec 07, 2016
Wow, what a scathing rebuttal, it violates one of the fundamental laws of physics. Well obviously if it works it doesn't and we will either explain it within the laws or change them.

Guess what happens before we change the laws of physics? We find a violation and change the laws so there isn't a violation. And that's what will happen again because there are things we can't explain yet.
KBK
5 / 5 (3) Dec 07, 2016
And with a 10 sec google we find that Cannae is apparently about to test a cubesat in orbit

"roughly one-quarter of this shoebox-sized satellite will be taken up by the Cannae Drive, and they'll stay in orbit for at least six months: "The longer it stays in orbit, the more the satellite will show that it must be producing thrust without propellant"
(for the google-illiterate)


The experiment is so inexpensive, that I'd prefer three of them on three different satellites from three provably different sources.

all the eggs of proof in one basket in such a critical point of contention, well, the possibility or room for malfeasance is too great.

there is an embedded suppression crew in existence- a black ops shill set....desiring to keep their technological advantage... and they work in concert .. ridiculing new ideas and the intrepid with, derision, smearing --- SOP dismissal tactics.

Trust --- but check. always. In this case, the safety is in redundancy.
ddaye
4 / 5 (4) Dec 07, 2016

The experiment is so inexpensive, that I'd prefer three of them on three different satellites from three provably different sources.


The incentives for private space companies would seem to be "astronomical." Maybe one would want to do its own test. I agree I'd like to see several tests.
Whydening Gyre
3.7 / 5 (3) Dec 07, 2016
This has me wondering...
Which requires more energy, a push or a pull?
The Universe, being "miserly" in it's energy expenditure modality will pick the most efficient.
Personally, I think a push requires more...
Anybody else?
Mimath224
3.7 / 5 (3) Dec 08, 2016
@Whydening Gyre Ever tried pulling 'uphill" Ha! Maybe the most economical in both time and direction?
yep
3 / 5 (2) Dec 08, 2016
Here it is straight from the horses mouth!
Pretty sweet interview!!
http://youtu.be/4hTdSg47h3k
antialias_physorg
3.7 / 5 (3) Dec 08, 2016
Here it is straight from the horses mouth!
Pretty sweet interview!!
http://youtu.be/4hTdSg47h3k

Unfortunately there's no detail on how it works (and the little detail he gives is somewhat at odds with the NASA paper linked in this article)
medusa_milena
4.2 / 5 (5) Dec 08, 2016
dark matter, dark energy

Those are still unknown, they only exist in calculations to fill in the gaps of other calculations.

Theory, nothing proved yet.
Bart_A
1 / 5 (1) Dec 08, 2016
Anti, please see this link for an explanation on how it works. Also from the inventor himself.

https://www.youtu...k6xWDrwY

Bart_A
1 / 5 (1) Dec 08, 2016
Anti, please see this link for an explanation on how it works. Also from the inventor himself.

https://www.youtu...k6xWDrwY

Captain Stumpy
3 / 5 (4) Dec 08, 2016
@antialias_physorg
Unfortunately there's no detail on how it works (and the little detail he gives is somewhat at odds with the NASA paper linked in this article)
i preferred this video:
https://www.youtu...mp;t=18s

or listen to Dr. Paul Matt Sutter (of: ask a spaceman) on the topic - he makes some real important observations regarding the EM drive in the link below - start at 32:30 -
https://www.youtu...t=36m24s

hiranyu
3.7 / 5 (3) Dec 08, 2016
Experimental results do not require a theory for them to be valid. It has been suggested by some supposed scientists that this is necessary. It is not the case nor has it ever been.
gkam
1 / 5 (4) Dec 08, 2016
I still think it runs on N-Rays .

Look them up.
Uncle Ira
3.2 / 5 (9) Dec 08, 2016
I still think it runs on N-Rays .
We been trying to tell you how stupid you are, so you did not need to tell us you think that.

Look them up.
It's a science site Skippy. Why you always asking everybody to look stuffs up? Maybe they already know that you thinking N-Rays is just more proof of how stupid you are.
Whydening Gyre
4.5 / 5 (6) Dec 08, 2016
@Whydening Gyre Ever tried pulling 'uphill" Ha! Maybe the most economical in both time and direction?

What if what you're pulling is round?
Anyway, there is no "uphill" in space - only other gravitational wells (and magnetic fields, of course)
gkam
2.3 / 5 (6) Dec 08, 2016
N-Rays were largely believed to be real by many scientists until proven wrong in a public demonstration. I suggest you use your upper head instead of just your mouth.
Uncle Ira
3.2 / 5 (9) Dec 08, 2016
N-Rays were largely believed to be real by many scientists until proven wrong in a public demonstration. .
I see you looked him up. You should do that more often,,,, BEFORE you push the "Submit-Him" button.
gkam
1.6 / 5 (7) Dec 08, 2016
No, Ira, I already knew it, unlike you, who really did just look them up.

That's why I brought them up.

Why would you think you are as smart as other folk?
Uncle Ira
3.7 / 5 (9) Dec 08, 2016
No, Ira, I already knew it,
Aaah, I see. That is why you said,,,,

I still think it runs on N-Rays


Uh, huh.

That's why I brought them up.
I bet you wished you didn't now, eh?

Why would you think you are as smart as other folk?
Depends on which other folks it is. As you? I am light years smarter than you. I think all the pot you smoke might have something to do with though, your kind of stupid can not be natural.
Whydening Gyre
5 / 5 (7) Dec 08, 2016
I still think it runs on N-Rays .

Look them up.

N rays (or N-rays) were a hypothesized form of radiation, described by French physicist Prosper-René Blondlot in 1903, and initially confirmed by others, but subsequently found to be illusory.

The professor was a blonde...
gkam
1 / 5 (5) Dec 08, 2016
Keep on snortin' that-there diesel soot and oil smoke . It's good for the thinkin'.

What is your need to attack? What is under your skin?

I brought up N-rays because like this phenomenon, folk were ready to believe it, . . . like cold fusion. N-Rays are an old story for those who had educations in science.
Uncle Ira
3.5 / 5 (8) Dec 08, 2016
I brought up N-rays because like this phenomenon, folk were ready to believe it, . . . like cold fusion. N-Rays are an old story for those who had educations in science.


Aaah, I see. So when you say "I still think it runs on N-Rays", what you really meant was "N-Rays are not real". If you say so,,,, is that the story you are going to stick with?
Scroofinator
5 / 5 (4) Dec 08, 2016
I didn't read the study yet, so for those that have, does the thrust change with varied frequency?
Mimath224
5 / 5 (4) Dec 08, 2016
@Whydening Gyre Yes, but was really thinking metaphorically. Really was thinking of the tensors involved in gravitation, that is very simply put finding the gradient of a slope then finding the next. For example, there is considerable energy arriving from the Sun and going in the opposite direction perhaps a 'pull' or push might be the same. Going into the Solar wind perhaps a 'push might be better? Just a thought.
Whydening Gyre
5 / 5 (3) Dec 08, 2016
@Mimath.Really was thinking of the tensors involved in gravitation, that is very simply put finding the gradient of a slope then finding the next. For example, there is considerable energy arriving from the Sun and going in the opposite direction perhaps a 'pull' or push might be the same. Going into the Solar wind perhaps a 'push might be better? Just a thought.

But what of the stronger "pull" of the Sun's gravity?
Much of it depends, of course, on the angle of the point of strongest contact....
Whydening Gyre
5 / 5 (3) Dec 08, 2016
@Mimath.Really was thinking of the tensors involved in gravitation, that is very simply put finding the gradient of a slope then finding the next. For example, there is considerable energy arriving from the Sun and going in the opposite direction perhaps a 'pull' or push might be the same. Going into the Solar wind perhaps a 'push might be better? Just a thought.

But what of the stronger "pull" of the Sun's gravity?
Much of it depends, of course, on the angle of the point of strongest contact....

The suns gravity pulls in, the centrifugal force pulls out. Solar wind is just a little "friction"
antialias_physorg
5 / 5 (3) Dec 09, 2016
i preferred this video:
https://www.youtu...mp;t=18s

Yeah, there's a couple of things in his video that are weird:
The amount of power needed for a flying car would be huge (as noted in the critique you posted)
The one that got me wondering, however, was when makes a comment about 'second generation' EM drives which are 'superconducting'. Now this one makes absolutely no sense, as nowhere in the apparatus would superconduction help (except make the power input a tiny bit more efficient).
antialias_physorg
5 / 5 (3) Dec 09, 2016

or listen to Dr. Paul Matt Sutter (of: ask a spaceman) on the topic - he makes some real important observations regarding the EM drive in the link below - start at 32:30 -
https://www.youtu...t=36m24s

Of course they make valid points about conservation of momentum and error bars (i.e. this is a paper which could be used to say: There might be something here that should be investigated with better methods" - i.e.: further work needed.)

Note, that in the following I am not making a statement on how the EM drive might work (if it does at all). I'll just giving a counter-example where you can get apparent(!) motion from nothing without violating coservation of motion:
The Alcubierre drive seems to be a mathematically valid way of getting from A to B. Note that nothing is actually moving in an Alcubierre drive so momentum is conserved (space is expanded/contracted.).

But generally I'm sceptical. Given the ease of setup I still think this should be verified in space.
Captain Stumpy
3.3 / 5 (7) Dec 09, 2016
But generally I'm sceptical. Given the ease of setup I still think this should be verified in space
@AA_P
yep... i am 100% with you on that one
(i.e. this is a paper which could be used to say: There might be something here that should be investigated with better methods" - i.e.: further work needed.)
i don't know... on one hand i think there should be more investigation into the subject (& a space test)...

but i also happen to agree with the second link i left above - there really should have been a lot more data and measurements before publishing anything

Captain Stumpy
3.3 / 5 (7) Dec 09, 2016
I didn't read the study yet, so for those that have, does the thrust change with varied frequency?
@Scroof
search the paper for the following:
Optimal tuning: considerable time and effort were spent empirically studying and mapping out the optimal and nonoptimal RF tuning configurations for the TM212 mode to generate maximum thrust.
http://arc.aiaa.o...1.B36120

apparently no
tesschris
Dec 09, 2016
This comment has been removed by a moderator.
Captain Stumpy
3 / 5 (6) Dec 09, 2016
NASA doesn't understand the EMDrive, but ...reddit.com/r/Physics_AWT/....

WARNING
PHISHING PSEUDOSCIENCE LINK

@zeph
if ya can't produce a reputable source to a journal then linking to your personal thread is simply phishing for suckers that click your link

antialias_physorg
5 / 5 (3) Dec 09, 2016
NASA doesn't understand the EMDrive

reddit? Really? You're scraping the bottom of the barrel now.
Mark Thomas
2 / 5 (2) Dec 09, 2016
How about heating the thing up by a different means, such as with electricity, to see if the measured "thrust" is the same? Because the reported "thrust" lags both when the device is turned on and when it is turned off in a way that looks like heating and cooling is involved, my guess is that if you heat the components up without microwaves you will still get the same reported effect. Note that we have to be careful to heat it up in exactly the same way, for example, it should look the same in infrared either way.

Mark my words, this is some kind of thermal effect, not new physics. Uneven thermal expansion shifting the center of mass, heating of residual air molecules on one side like a Crookes radiometer bulb, something I haven't thought of, etc.

Captain Stumpy
3 / 5 (6) Dec 09, 2016
reddit? Really? You're scraping the bottom of the barrel now.
@AA_P
it's zephir's awt threads ... it's worse than scraping the bottom of the barrel

it's flat out phishing for suckers and promoting delusional pseudoscience

not to mention spam spam spam spam spam spam eggs and Spam
gculpex
1 / 5 (1) Dec 09, 2016
This has me wondering...
Which requires more energy, a push or a pull?
The Universe, being "miserly" in it's energy expenditure modality will pick the most efficient.
Personally, I think a push requires more...
Anybody else?

Only because you don't want to be squished by the object if very heavy.
Whydening Gyre
5 / 5 (2) Dec 09, 2016
I didn't read the study yet, so for those that have, does the thrust change with varied frequency?
@Scroof
search the paper for the following:
Optimal tuning: considerable time and effort were spent empirically studying and mapping out the optimal and nonoptimal RF tuning configurations for the TM212 mode to generate maximum thrust.
http://arc.aiaa.o...1.B36120

apparently no

But, then - might it vary with changing the angle of the cone...? Or perhaps, where the microwaves originate. I guess I'm saying - would changing the angle of EM direction vary the thrust...?
tesschris
Dec 09, 2016
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Whydening Gyre
5 / 5 (1) Dec 09, 2016
Of course, it's linked and explained above.

Neither seems to explore the variations I was curious about...
Da Schneib
5 / 5 (1) Dec 09, 2016
I'm going with the Unruh Effect, if this is proven beyond doubt by experimental data.
Whydening Gyre
5 / 5 (3) Dec 10, 2016
I'm going with the Unruh Effect, if this is proven beyond doubt by experimental data.

Interesting. But can you explain why? Increase of spin?
(I'm cousin to some North Dakota Unruh's, BTW...:-)
Da Schneib
5 / 5 (3) Dec 10, 2016
Yes, but it's pretty esoteric.

I'll give you a link to a pretty balanced article that has links to where the real data are. Give it a look and tell me what you think. http://www.scienc...ve-works
tesschris
Dec 10, 2016
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tesschris
Dec 10, 2016
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tesschris
Dec 10, 2016
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Whydening Gyre
5 / 5 (4) Dec 10, 2016
Yes, but it's pretty esoteric.

I'll give you a link to a pretty balanced article that has links to where the real data are. Give it a look and tell me what you think. http://www.scienc...ve-works

Again, sifting thru what I could, no real info on wave "angle of attack". Just throwing MW into the cavity. If ya think about it, the cone shape can add additional spin velocity to an already spinning wave...
Depending on the angle...

BTW - Tesschris is Zeph - I recognize the "style"...:-)
antialias_physorg
5 / 5 (3) Dec 10, 2016
Just throwing MW into the cavity.

I guess the path length will habve to be so that it's a resonance in there, That would set up a fixed relationship between diameter and angle of the cavity.
antialias_physorg
5 / 5 (4) Dec 10, 2016
the cone shape can add additional spin velocity to an already spinning wave...

Not really (conservation of angular momentum would be violated)
Da Schneib
5 / 5 (3) Dec 10, 2016
Here's why the Unruh Effect changes the calculation of conservation of momentum.

The Unruh Effect says that the vacuum appears warmer in an accelerated frame.

Analyses of the EM Drive that claim it violates conservation of momentum assume that the vacuum is nothing; in fact, the Unruh Effect shows that the vacuum is something. It couldn't radiate (which is required to appear warmer, as the Unruh Effect shows) if it were nothing. Thus, the analyses that are based on the radiation of microwaves, and their containment within a metal enclosure, show that conservation of momentum is violated when we ignore the contained vacuum.
[contd]
Da Schneib
5 / 5 (4) Dec 10, 2016
[contd]
GRT shows unequivocally that two accelerated frames need not be equivalent; all inertial frames are equivalent and this denies absolute velocity, but accelerated frames can be irreconcilable and this supports absolute acceleration. Absolute acceleration means that observers from all frames will agree that an object that is being accelerated is being accelerated. They may not agree on the magnitude of the acceleration, but they agree on its existence.

This in and of itself shows that momentum is not conserved among accelerated frames. In fact, in GRT, it is not momentum that is conserved, but energy. This alone has already violated conservation of momentum, and we have known it since 1915. The overarching conservation of the energy-momentum tensor means that momentum and energy can be interconverted, just as mass and energy can be interconverted under SRT.

[contd]
Da Schneib
5 / 5 (4) Dec 10, 2016
[contd]
Getting down to the nitty-gritty, what GRT shows is that the energy-momentum tensor is non-divergent;. in other words, energy + momentum is conserved. It does not conserve momentum as an individually conserved quantity, and just as SRT overturned conservation of mass, and replaced it with mass-energy, GRT overturns conservation of momentum and replaces it with energy-momentum.

That is, if the measurements of the acceleration by the EM Drive are correct. It will be interesting to see how this develops as more and more precise measurements of its operation are made.
Whydening Gyre
5 / 5 (4) Dec 10, 2016
[contd]
Getting down to the nitty-gritty, what GRT shows is that the energy-momentum tensor is non-divergent;. in other words, energy + momentum is conserved. It does not conserve momentum as an individually conserved quantity, and just as SRT overturned conservation of mass, and replaced it with mass-energy, GRT overturns conservation of momentum and replaces it with energy-momentum.

That is, if the measurements of the acceleration by the EM Drive are correct. It will be interesting to see how this develops as more and more precise measurements of its operation are made.

Wow, Schneib... Those last 3 posts are only gonna take me 3 days to absorb...:-)
WB, BTW...
However, I did have one take away - sounding dangerously close to "Aether", there...:-)
Da Schneib
5 / 5 (4) Dec 10, 2016
We already know that vacuum is not empty. Think of fields.
Mimath224
5 / 5 (3) Dec 10, 2016
@Whydening Gyre I have to admit that I am not as well informed on the Unruh effect as Da Schneib but since he talks of '...The Unruh Effect says that the vacuum appears warmer in an accelerated frame...' then I think some scientists have said that it can be similar to Hawking Radiation. At least that's what it seems to me. Vacuum here is then defined as a field of the lowest state (not sure about my terminology here). Again, as I understand it (please correct me if I'm wrong) it applies to accelerated observers. @Da Schneib a question here...in which respect would you regard the stress energy tensor? Electromagnetic or other. Any ideas on what/how an accelerating expanding universe would have on the Unruh effect since basically the field might accelerating along with the coordinates? (not a trick but a genuine question...as a layman I simply don't know, Ha!)
Whydening Gyre
5 / 5 (3) Dec 10, 2016
@Whydening Gyre I have to admit that I am not as well informed on the Unruh effect as Da Schneib but since he talks of '...The Unruh Effect says that the vacuum appears warmer in an accelerated frame...'

Schneibs real name is probly Unruh...:-)
Da Schneib
5 / 5 (2) Dec 10, 2016
Heh, no, I'm not that smart, but thanks.
Da Schneib
5 / 5 (2) Dec 10, 2016
@Whydening Gyre I have to admit that I am not as well informed on the Unruh effect as Da Schneib but since he talks of '...The Unruh Effect says that the vacuum appears warmer in an accelerated frame...' then I think some scientists have said that it can be similar to Hawking Radiation. At least that's what it seems to me.
Correct as far as I know. This is bolstered by noting that the rest coordinates for an accelerated frame are Rindler coordinates, which have an event horizon.

Vacuum here is then defined as a field of the lowest state (not sure about my terminology here).
Vacuum is always defined as the lowest state of the fields. Note that this is not necessarily zero; zero may be lower than the lowest possible state.

Again, as I understand it (please correct me if I'm wrong) it applies to accelerated observers.
Hmmmm, not sure what the referent for "it" is here. Also not sure what an "accelerated observer" is.

[contd]
Da Schneib
5 / 5 (2) Dec 10, 2016
[contd]
@Da Schneib a question here...in which respect would you regard the stress energy tensor? Electromagnetic or other.
The stress-energy tensor is the total of all mass and energy and field in a given place. It's also called the energy-momentum tensor. It's not either/or with respect to electromagnetic energy; electromagnetic energy is part of it, so is mass, so is stress, so is pressure, so is field, so is momentum. It's the right side of the Einstein Field Equations, multiplied by a bunch of constants. I'm not sure what you're asking here.

Any ideas on what/how an accelerating expanding universe would have on the Unruh effect since basically the field might accelerating along with the coordinates?
I'm not sure it would have any effect upon the Unruh Effect at all. Can you explain why you think it might? Remember that universal expansion, even accelerating universal expansion, doesn't necessarily imply real acceleration.
[contd]
Da Schneib
5 / 5 (2) Dec 10, 2016
One more thing, @Mimath: be quite careful to distinguish between spacetime itself- AKA "the vacuum"- and the coordinate system we apply to it in order to make measurements. The vacuum is a thing; the coordinates are not. We can pick any convenient set of coordinates and transform to another set later if that becomes convenient.
Mimath224
5 / 5 (2) Dec 11, 2016
@Da Schneib points taken. I thought there was a specific EM stress tensor which I think differs in the T^00 position which contains the Em fields but thinking again, this may be the tensor you are referring to. The other EM stress tensor is the one commonly met in EM having all positions bar the diagonal, with E or B entries which does have other names (Maxwell etc). No, I don't have any thoughts about the effect of an accelerating universe, I was simply asking for a view. I do say I am a layman and I'm really asking question rather than expressing a point of view...probably like most layman am trying to jump from the common 3D stress tensor and is easy to get the wrong idea. Anyway, thanks for your reply...interesting.
tesschris
Dec 11, 2016
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tesschris
Dec 11, 2016
This comment has been removed by a moderator.
tesschris
Dec 11, 2016
This comment has been removed by a moderator.
Tuxford
1 / 5 (1) Dec 12, 2016
Who now owns Physorg anyway?

http://www.omicro...ucts.asp

And Why?

https://en.wikipe...Phys.org

Inquiring minds want to know? Are we being monitored? I am sure that those comments made on this story are being scrutinized. The classified physics must be kept suppressed, for national security purposes.
Captain Stumpy
5 / 5 (3) Dec 12, 2016
@nutford
Inquiring minds want to know? Are we being monitored?
yes, but not like you imagine in the delusional conspiratorial way...
The classified physics must be kept suppressed, for national security purposes
WTF?
there is classified technology ... and that can be supressed

but there is no such thing as "classified physics"...

in fact, that can be demonstrated by the nuclear physics taught in this link: https://ocw.mit.edu/index.htm

if they won't classify nuclear physics and relativity to insure you can't learn how to build nuclear weapons so we can protect the world from idiots then what makes you think there is "classified physics"????

did bigfoot tell you?
Scroofinator
5 / 5 (1) Dec 12, 2016
but there is no such thing as "classified physics"...

Come on now, didn't you watch the X-files reboot?
Captain Stumpy
5 / 5 (2) Dec 12, 2016
but there is no such thing as "classified physics"...

Come on now, didn't you watch the X-files reboot?

@Scroof
LMFAO
Ok, that made me laugh

my dad was a big fan of the show... but i don't get TV here
Cassini1
2 / 5 (4) Dec 13, 2016
Except that China develops EMDrive for five years already: "This technology is currently in the latter stages of the proof-of-principle phase, with the goal of making the technology available in satellite engineering as quickly as possible' said Li Feng, chief architect of the China National Space Technology Institute's communications satellite division." As usually, the mainstream physics supporters are the least informed people about actual news in their field. 1url.cz/PtB19

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