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Old 9th September 2016, 10:36 AM   #41
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If it's in orbit and continuously points the same way, the integral of the pico-thrust will eventually make a measurable deviation in the satellite's orbit.
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Old 9th September 2016, 05:27 PM   #42
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Originally Posted by Beelzebuddy View Post
If it's in orbit and continuously points the same way, the integral of the pico-thrust will eventually make a measurable deviation in the satellite's orbit.

Yeah, that's the idea. The complication is if they can maintain that "continuously points the same way" part. If they can overcome that, and can make the satellite move into an orbit that would be physically impossible to reach using any known means of propulsion, then we'd have to take a serious look at it.
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Old 10th September 2016, 12:49 PM   #43
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Originally Posted by Beelzebuddy View Post
If it's in orbit and continuously points the same way, the integral of the pico-thrust will eventually make a measurable deviation in the satellite's orbit.
You don't think there are other forces on the satellite that are orientation dependent?
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Old 11th September 2016, 05:10 AM   #44
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Originally Posted by RussDill View Post
You don't think there are other forces on the satellite that are orientation dependent?
In space? Not really. There's drag, but that's very predictable, and shouldn't interfere with detecting anomalous thrust.
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Old 11th September 2016, 09:55 AM   #45
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Originally Posted by Beelzebuddy View Post
In space? Not really. There's drag, but that's very predictable, and shouldn't interfere with detecting anomalous thrust.
The drag is not that predicable in low orbits. The top of the atmosphere is variable.

Unless this puts out enough thrust to significantly overcome the drag, how do you tell if it's making thrust or just dragging a minuscule amount less than you expected?
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Old 11th September 2016, 10:32 AM   #46
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Originally Posted by Beelzebuddy View Post
In space? Not really. There's drag, but that's very predictable, and shouldn't interfere with detecting anomalous thrust.
Outgassing, incoming radiation pressure (both from the sun, and the earth), outgoing radiation pressure, forces from electric fields, forces from magnetic fields, etc.

And you discount drag, but you'd have to account very carefully for it. You can't just imagine drag coming from a single direction. The angle it impacts the many surfaces of the spacecraft effect the direction of force that the reaction imparts. So you also have to account for lift and sideslip.

ETA: And don't forget to the additional uneven heating of the spacecraft created by drag.
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Old 11th September 2016, 11:52 AM   #47
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Originally Posted by phunk View Post
The drag is not that predicable in low orbits. The top of the atmosphere is variable.
If you want low orbit, fuggitaboudit. The higher-isp kind of ion drives aren't even good in low orbit, and their thrust is measurable. I'd assume you want to park the satellite in a graveyard orbit, because it'll take years to get a effect. Which is another strike in cubesats' disfavor, since low orbit is their typical destination.

Originally Posted by RussDill View Post
Outgassing, incoming radiation pressure (both from the sun, and the earth), outgoing radiation pressure, forces from electric fields, forces from magnetic fields, etc.
Outgassing should be short term, and all the rest are either predictable enough to be factored out (forces from magnetic fields), or small enough to be discarded (outgoing radiation pressure).

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Old 11th September 2016, 12:23 PM   #48
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Originally Posted by Beelzebuddy View Post
If you want low orbit, fuggitaboudit. The higher-isp kind of ion drives aren't even good in low orbit, and their thrust is measurable. I'd assume you want to park the satellite in a graveyard orbit, because it'll take years to get a effect. Which is another strike in cubesats' disfavor, since low orbit is their typical destination.


Outgassing should be short term, and all the rest are either predictable enough to be factored out (forces from magnetic fields), or small enough to be discarded (outgoing radiation pressure).
Show me the money (error bars)
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Old 11th September 2016, 12:36 PM   #49
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Originally Posted by RussDill View Post
Show me the money (error bars)
I think I've already spent enough effort defending something I don't think works to begin with.
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Old 22nd September 2016, 04:27 AM   #50
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Still chugging on:

http://www.ibtimes.co.uk/emdrive-con...rence-1582115#


It would seem that we're at least moving closer to an answer.

I'm hoping it works. I'm thinking it probably doesn't.
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Old 22nd September 2016, 03:47 PM   #51
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Originally Posted by Beelzebuddy View Post
If it's in orbit and continuously points the same way, the integral of the pico-thrust will eventually make a measurable deviation in the satellite's orbit.
That would be fine if there weren't other issues that effect the trajectory. The effects of gravitation variations for instance, CMEs, etc.
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Old 10th October 2016, 03:12 AM   #52
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Here's a theory as to how it works: https://www.researchgate.net/publica...AVITY_IN_A_CAN

I'm not convinced, but I don't know enough about the physics to say much.
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Old 10th October 2016, 03:23 AM   #53
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Originally Posted by Squeegee Beckenheim View Post
Here's a theory as to how it works: https://www.researchgate.net/publica...AVITY_IN_A_CAN

I'm not convinced, but I don't know enough about the physics to say much.
It seems written in a very amateurish way overall. He makes a fair number of assumptions and doesn't explain what the equations are supposed to mean. In the end he even says "ground state". Ground state is a defined and proper term, but he puts quotes around it and explains it (accurately) in parentheses, I really don't see someone skilled enough to come up with a valid explanation doing that. On top of it all, he actually says the energy is stored in a ground state, which is the exact opposite of what a ground state means (i.e. the state of the particle that has the lowest energy).

The site it's published on doesn't look like a particularly trustworthy science magazine either.

I wouldn't bet on this being a valid scientific explanation for EM drive

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Old 10th October 2016, 04:04 AM   #54
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Doesn't look great to me. He seems to be making the assumption that a wave propagating in a tapered waveguide changes frequency so as to match the change in resonant frequency of the cavity, and that this can be expressed as a red shift in one direction and a blue shift in the other; if I understand it correctly, that's simply nonsense. Everything else follows from there.

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Old 10th October 2016, 11:23 AM   #55
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Conservation of momentum is one bedrock of physics that I really don't expect to be overturned. I could believe that there might be a momentum transfer that hadn't been accounted for but violating conservation of momentum* would be about as big as violating one of the laws of thermodynamics.

If you want something that doesn't use reaction mass, photons can carry momentum.

*which was an early claim (IIRC)
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Old 10th October 2016, 12:51 PM   #56
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Originally Posted by Squeegee Beckenheim View Post
Here's a theory as to how it works: https://www.researchgate.net/publica...AVITY_IN_A_CAN
As soon as we read the phrase "Engineering Model of Quantum Gravity" in an abstract we can guess at a bad presentation at what looks like a dubious conference.
The actual "model" is in a slide show (!) and is basically throwing in an arbitrary refractive index into known equations.
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Old 10th October 2016, 03:10 PM   #57
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Originally Posted by Reality Check View Post
As soon as we read the phrase "Engineering Model of Quantum Gravity" in an abstract we can guess at a bad presentation at what looks like a dubious conference.
The actual "model" is in a slide show (!) and is basically throwing in an arbitrary refractive index into known equations.
So is this one of those models that requires that the speed of light is not a constant inside the EM drive? Your mention of an "arbitrary refractive index" seems to suggest this to me but the math in that link you quoted is beyond my current capibility to understand.
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Old 10th October 2016, 03:13 PM   #58
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Originally Posted by Reality Check View Post
As soon as we read the phrase "Engineering Model of Quantum Gravity" in an abstract we can guess at a bad presentation at what looks like a dubious conference.
The actual "model" is in a slide show (!) and is basically throwing in an arbitrary refractive index into known equations.
There's a text paper which deals with his idea of Quantum Gravity here: https://www.researchgate.net/publica...UANTUM_GRAVITY
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Old 10th October 2016, 04:16 PM   #59
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Originally Posted by Squeegee Beckenheim View Post
There's a text paper which deals with his idea of Quantum Gravity...
Not worth wasting time on when the author does not even know what quantum gravity means !

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Old 10th October 2016, 04:19 PM   #60
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Originally Posted by Turgor View Post
So is this one of those models that requires that the speed of light is not a constant inside the EM drive?
It is not even a model - just a crank making up bad physics that is not really related to the actual EM drive (other than a "tapered" cavity). The author is speculating about a future superconducting frustrum cavity.

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Old 21st October 2016, 04:30 AM   #61
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The inventor is now touting having been granted a patent as some sort of validation of the drive.

Don't people get granted patents for perpetual motion machines?



http://www.zmescience.com/science/ne...public-friday/
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Old 24th October 2016, 10:10 AM   #62
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Originally Posted by 3point14 View Post
The inventor is now touting having been granted a patent as some sort of validation of the drive.

Don't people get granted patents for perpetual motion machines?



http://www.zmescience.com/science/ne...public-friday/

Quote:
“This is a proper, professional way of establishing prior ownership done by professionals in the patent office, and in order to publish my patent application, they had to first carry out a thorough examination of the physics in order to establish that the invention does not contravene the laws of physics.”

Yeah, see, that's complete ********.

In virtually all jurisdictions now, including the UK, patent applications are routinely published prior to the patent being granted, and often prior to the application even being examined. This usually happens 18 months after the filing date, or the earliest "priority" date.

In fact, here in Canada, I'm not even allowed to examine the application prior to its publication. This pre-grant publication is a mostly automated process, which the applicant has to actually take positive steps to avoid, if they decide they don't want their application to be published (this also means their patent won't be granted, btw).

And even after the patent is granted, it's far too ambitious to say that we've carried out "a thorough examination of the physics in order to establish that the invention does not contravene the laws of physics". That's the ideal, but the ideal is often not met, due to constraints on time allocated to examination, the limits of the examiner's own knowledge, and certain structural features of the patent examination process created by years of jurisprudence, that on occasion actually prevents the examiner from exercising proper skepticism of questionable claims.


ETA: and if you click the link at the bottom to see the "patent", it's clearly labelled, right on the front page, "UK Patent Application", with a publication date of 12-10-2016. And if you go check the status at the UK IPO : https://www.ipo.gov.uk/p-ipsum/Case/...mber/GB2537119 its status is listed as "Awaiting First Examination".
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Old 24th October 2016, 10:33 AM   #63
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Indeed Horatius.

As an aside

I'm no more likely to entertain the idea of a violation of conservation of momentum than I am to entertain the idea of a violation of the conservation of energy.
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Old 9th November 2016, 01:00 PM   #64
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Leaked paper suggests EM Drive tested by NASA actually works



Note the lack of peer review for the leaked article, but it's interesting, nonetheless.
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Old 9th November 2016, 03:20 PM   #65
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Originally Posted by RussDill View Post
Outgassing, incoming radiation pressure (both from the sun, and the earth), outgoing radiation pressure, forces from electric fields, forces from magnetic fields, etc.

And you discount drag, but you'd have to account very carefully for it. You can't just imagine drag coming from a single direction. The angle it impacts the many surfaces of the spacecraft effect the direction of force that the reaction imparts. So you also have to account for lift and sideslip.

ETA: And don't forget to the additional uneven heating of the spacecraft created by drag.
As a passing aside from one who normally lurks in such a thread, I hope you don't mind my pointing out that I would hate to have ever received a homework assignment from you. Holy cow.
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Old 9th November 2016, 05:23 PM   #66
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Originally Posted by Hlafordlaes View Post
As a passing aside from one who normally lurks in such a thread, I hope you don't mind my pointing out that I would hate to have ever received a homework assignment from you. Holy cow.
Extraordinary claims require extraordinary evidence. Since these claims for the EM drive are extraordinarily extraordinary to the point of bordering on miraculous, I see no fault at all in such great attention to detail.
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Old 9th November 2016, 10:04 PM   #67
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Yup, from my armchair at least, it seems like it'd be a lot easier to control variables of a test article you actually have access to rather than one you have to launch into space.
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Old 10th November 2016, 01:15 AM   #68
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Just kidding around, guys. It was that thoroughness with an extra "homework" ETA that made an impression. Couldn't be happier there are people to challenge extraordinary claims.
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Old 10th November 2016, 04:54 AM   #69
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Originally Posted by 3point14 View Post
Leaked paper suggests EM Drive tested by NASA actually works



Note the lack of peer review for the leaked article, but it's interesting, nonetheless.
There's a couple of critiques of the paper on reddit:
https://www.reddit.com/r/EmDrive/com...paper/d9nyssv/
https://www.reddit.com/r/EmDrive/com..._data/d9n8vf6/
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Old 10th November 2016, 05:05 AM   #70
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Originally Posted by Squeegee Beckenheim View Post

Many thanks
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Old 10th November 2016, 05:39 AM   #71
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I'm pretty sure the EM Drive runs on N Rays.

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Old 10th November 2016, 06:59 AM   #72
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So, I'm confused. Does it work , at albeit a very small thrust, or does it not?
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Old 10th November 2016, 07:02 AM   #73
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Originally Posted by jaydeehess View Post
So, I'm confused. Does it work , at albeit a very small thrust, or does it not?

Probably not, being realistic about it.

There's a tiny chance that it does.

The best that can be said of it at the moment is that it hasn't been proved not to work.
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Old 10th November 2016, 07:13 AM   #74
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Originally Posted by 3point14 View Post
Probably not, being realistic about it.

There's a tiny chance that it does.

The best that can be said of it at the moment is that it hasn't been proved not to work.
The main issue being that the physics that allow for this force being generated are, at present, unknown?
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Old 10th November 2016, 07:20 AM   #75
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Originally Posted by jaydeehess View Post
The main issue being that the physics that allow for this force being generated are, at present, unknown?

The physics are believed to be impossible - i.e. producing an action without an equal and opposite reaction.

There is at least one theory that attempts to explain how it can do this but that hasn't been peer reviewed, as far as I'm aware, so must be taken with a whole mine's worth of salt.
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Old 10th November 2016, 12:12 PM   #76
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Originally Posted by jaydeehess View Post
The main issue being that the physics that allow for this force being generated are, at present, unknown?
That and that, as yet, none of the experiments which have shown positive results appear to have fully controlled for outside forces. The only group to apparently have done so is a group in China - they published some results a few years back showing some thrust and immediately set about refining the experiment in order to better eliminate the influence of potential outside forces. When they did so, they found that any results were indistinguishable from noise, and attributed their earlier results to noise.

The EMDrive community (which is only interested in the truth, rather than really, really wanting it to be true) either misrepresented those results, presenting the point above which they would have counted thrust as significant as being the actual thrust achieved (it wasn't even close), or claimed that the lead scientist had given up science all together to become a poet (she hasn't).
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Old 10th November 2016, 12:14 PM   #77
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Originally Posted by 3point14 View Post
There is at least one theory that attempts to explain how it can do this but that hasn't been peer reviewed, as far as I'm aware, so must be taken with a whole mine's worth of salt.
There have been several hypotheses, but I've yet to see one that didn't have quite an emphatic take-down.

My favourite was that there was exhaust because neutrinos are constantly moving through matter, so there are neutrinos inside the chamber, and if the waves in the chamber interact with the neutrinos somehow, then the neutrinos would be the exhaust. Science!
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Old 10th November 2016, 12:14 PM   #78
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Originally Posted by 3point14 View Post
The physics are believed to be impossible - i.e. producing an action without an equal and opposite reaction.

There is at least one theory that attempts to explain how it can do this but that hasn't been peer reviewed, as far as I'm aware, so must be taken with a whole mine's worth of salt.
Indeed, conservation of momentum is pretty fundamental.
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Old 10th November 2016, 06:31 PM   #79
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Originally Posted by Squeegee Beckenheim View Post
That and that, as yet, none of the experiments which have shown positive results appear to have fully controlled for outside forces. The only group to apparently have done so is a group in China - they published some results a few years back showing some thrust and immediately set about refining the experiment in order to better eliminate the influence of potential outside forces. When they did so, they found that any results were indistinguishable from noise, and attributed their earlier results to noise.

The EMDrive community (which is only interested in the truth, rather than really, really wanting it to be true) either misrepresented those results, presenting the point above which they would have counted thrust as significant as being the actual thrust achieved (it wasn't even close), or claimed that the lead scientist had given up science all together to become a poet (she hasn't).


You forgot the laughing dog.

The EM drive is just as real as Rossi's "ecat" and Bush's Iraq WMD. Neither works because they can't work. The world has FAR to many "scientists" of low ability. No chance for them to do anything worthwhile so they "work" on crap like EM drive and LENR.

The ecat is a knowing fraud and so is EM drive.
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Old 11th November 2016, 12:03 PM   #80
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Originally Posted by Squeegee Beckenheim View Post


Quote:
Data from only 3 test runs (Table 2).

Wow, this alone makes me think they really don't know what they're doing. I had more data than that for my Master's thesis, and that was on something that wasn't even physically impossible

Anyone who thinks that this would be enough data to overturn so many different laws of physics should just be ignored.
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