Em drive good news...

[wumpus]

1 hour ago, p1t1o said:

My money is on: instrument sensitivity has been rising steadily, now we are getting tiny readings from nowhere that we couldnt detect before - is it from tiny environmental factors or newly discovered, ground-breaking physics?

I'll let you try out Occams razor on that one.

I'd have to say that assuming that equations hold that much further than the data used to generate them seems the height of hubris.  You shouldn't always assume that nature is going to hand over the Higgs Bison once you scale up your experiments, sometimes you get noise like microwave background radiation with your new radio telescope.  I will admit that anything that gives you a "free lunch" is *never* going to get the benefit of the doubt.

https://en.wikipedia.org/wiki/Holmdel_Horn_Antenna

[p1t1o]

14 hours ago, wumpus said:

I'd have to say that assuming that equations hold that much further than the data used to generate them seems the height of hubris.  You shouldn't always assume that nature is going to hand over the Higgs Bison once you scale up your experiments, sometimes you get noise like microwave background radiation with your new radio telescope.  I will admit that anything that gives you a "free lunch" is *never* going to get the benefit of the doubt.

https://en.wikipedia.org/wiki/Holmdel_Horn_Antenna

I know, I know, and I've been trying  really hard with the emdrive, but it has been quite a long time for nothing much to come from something that supposedly violates conservation of momentum.

[78stonewobble]

2 hours ago, p1t1o said:

I know, I know, and I've been trying  really hard with the emdrive, but it has been quite a long time for nothing much to come from something that supposedly violates conservation of momentum.

Well there's 2 options?

Either you can violate conservation of momentum, under certain circumstances... Or it doesn't really violate conservation of momentum.

EDIT: Well and there's the third offcourse... That it doesn't work.

Edited November 9, 2016 by 78stonewobble

[p1t1o]

15 minutes ago, 78stonewobble said:

Well there's 2 options?

Either you can violate conservation of momentum, under certain circumstances... Or it doesn't really violate conservation of momentum.

EDIT: Well and there's the third offcourse... That it doesn't work.

I try and keep an open mind but the 3rd option seems more and more likely the longer it takes...to figure out if anything is even happening...

I would have thought that if violation of conservation of momentum was possible (which if it turns out to be the case, *has always been* possible) that no sign of it has ever even been suspected up until now. 

Would be extremely happy to be proven wrong of course

[hms_warrior]

1 hour ago, p1t1o said:

I would have thought that if violation of conservation of momentum was possible (which if it turns out to be the case, *has always been* possible) that no sign of it has ever even been suspected up until now.

Well i am not saying that emDrive is true but: the effect is created by high-frequency, high power em-Waves.... the first dips into this area are only 70 years old. Remember how long it took humanity to go from focusing light by lenses to a full theory of what photons are? Personaly i would not find it too suprising to find out we have not a complete understanding of what high power em-waves are/can do. I tried to read into the whole radio-technology stuff when i first heard of emDrive and it is ... complicated. Complex. lot's of maths....the difficult ones. I wouldn't be suprised to find out there are more people with a deep understanding of relativity theory than with the same knowlege-level of radiotechnology.

Edited November 9, 2016 by hms_warrior

[p1t1o]

7 minutes ago, hms_warrior said:

Well i am not saying that emDrive is true but: the effect is created by high-frequency, high power em-Waves.... the first dips into this area are only 70 years old. Remember how long it took humanity to go from focusing light by lenses to a full theory of what photons are? Personaly i would not find it too suprising to find out we have not a complete understanding of what high power em-waves are/can do. I tried to read into the whole radio-technology stuff when i first heard of emDrive and it is ... complicated. Complex. lot's of maths....the difficult ones. I wouldn't be suprised to find out there are more people whit a deep understanding of relativity theory than with the same knowlege-level of radiotechnology.

All that stuff is the exact reason I have an open mind and havn't entirely dismissed it as a scam.

On the other hand, one reason I am skeptical is because this is not the first time (remember the faster-than-light neutrinos?) this has happened and won't be the last.

[Nuke]

i like to think that we just found a better way to make a photon drive through some quantum effect that is better than the usually quoted 300MW per newton.

[Green Baron]

22 minutes ago, hms_warrior said:

Well i am not saying that emDrive is true but: the effect is created by high-frequency, high power em-Waves.... the first dips into this area are only 70 years old. Remember how long it took humanity to go from focusing light by lenses to a full theory of what photons are? Personaly i would not find it too suprising to find out we have not a complete understanding of what high power em-waves are/can do. I tried to read into the whole radio-technology stuff when i first heard of emDrive and it is ... complicated. Complex. lot's of maths....the difficult ones. I wouldn't be suprised to find out there are more people with a deep understanding of relativity theory than with the same knowlege-level of radiotechnology.

Might be true that one day we'll dismiss conservation of momentum or find something else to replace it, and maybe the em-drive thing is the first step towards that, but for now and until there haven't been reliable reproductions as well as seriously reviewed papers the em-drive thing is rather something to hope for/believe in.

In one of the links in the OP there was a peer reviewed paper announced for december, if i got it right. Looking forward to that ...

 

[Nefrums]

One crazy theory is that we are looking at a Artificial gravity generator...

Edited November 9, 2016 by Nefrums

[78stonewobble]

5 hours ago, p1t1o said:

I try and keep an open mind but the 3rd option seems more and more likely the longer it takes...to figure out if anything is even happening...

I would have thought that if violation of conservation of momentum was possible (which if it turns out to be the case, *has always been* possible) that no sign of it has ever even been suspected up until now. 

Would be extremely happy to be proven wrong of course

Well, I presume any scientist or just scientifically curious person would be excited about the discovery of something new.  

In regards to your middle part... Well, it could be that the effect has allways been there, it's just now that our ability to measure it is sufficient (if it isn't measurement errors in some way).

I'm trying to keep an open mind as well, but I usually takes things like these with a large grain of salt... Basically I think it should be researched and checked out, but I'm not gonna throw my money after a supposed miracle product.  

[monstah]

I can't do ctrl-F on the document, and I ain't reading it all; but skimming it, nowhere did it give me the impression it's "a NASA paper". It's a paper by people who work at NASA, as far as I can see. And even if it were, arguments by authority aren't really arguments, so this "NASA is studying it so it must be real" attitude seems rubbish to me.

And, like others have said, they seem to extrapolate from tiny measurements that could be background noise, up to power settings way above those used in the experiments. And the introduction itself says that "RF resonant cavities have generated anomalous thrust (...) in spite of the apparent lack of a propellant or other medium", where the "apparent" is emphasized on the article, not by me. YMMV, but I interpret this as even they don't seem to be sure they aren't just throwing particles or interacting with environmental electric fields. They do mention possible sources of error from page 25 to page 28, and RF interaction prevention seems to me to be the most handwaved as "eh, good enough".

Long story short, I still think this is rubbish, unfortunately  

[Technical Ben]

On 08/11/2016 at 5:06 PM, p1t1o said:

Im not sure, but IIRC one of the most prominent tests did try the test with the thruster upside-down....and measured a force in the same direction as right-side up....

IIRC that may have been the bell (cavity) swapped around, not the entire device? If it does follow one direction only, then it strongly suggests the force is a magnetic or thermal one. Is it repelling off the metal structure of the buildings etc?

[monstah]

5 hours ago, p1t1o said:

remember the faster-than-light neutrinos?

Wasn't that the experiments where the problem was a faulty contact in a cable? Shows you how simple the problem can be that generates news of "NEW SCIENCE!"

And no, I don't think this is a scam, just as I don't think Mars One is a scam. That's because I don't doubt the people's intentions, rather their beliefs and/or conclusions. They're good-hearted (as far as I believe), but wrong nevertheless.

[PB666]

On 11/8/2016 at 7:18 AM, Steel said:

Well the paper's abstract gives us the headline figure of 1.2 (+/- 0.1) mN/kW, so 1 MW (assuming a perfectly linear relationship) would give 1.2 N of thrust.

 

Interesting to note that the authors, in their own conclusion, cede that the effects of thermal expansion were only "addressed to a degree" and that further testing would need to be performed to completely rule out thermal expansion having an impact on reported results.

EDIT: Reading a little further, even the units of the headline figure are a little odd, considering it quotes a figure in mN/kW, when in fact their tests only go up to 80W. It's a fair bit of extrapolation to go from 80W to 1000W...

EDIT #2: also can we please talk about how these guys have assumed a straight line fit over a range of input power in the kilowatts, based on a data set of three points over range of 40W...

Given that a photon drive is 100 MW/N and we 100MW/120N therefore its 120 time more power efficient that a photon drive. Not good but useful.

JUst remember, to get to mars you need to carry a Kilotonn. Solar panels at best would produce maybe 1MW, though we are talking realistically space station size panels at double the efficiency at 300 kw range. That basically puts you in the .4N range sub microg range. Very difficult to get out of LEO with that. Its basically a high ISP ion drive. Very small devices maybe, tugging between mars L1 and Earth L2 maybe,

Also remember, that the device has not be tested in space.

 

Edited November 9, 2016 by PB666

[YNM]

IMHO all these experimental objects aren't going to go to space unless they're tested in space (or close to space - space-like - condition). I mean, jet engines do work down here, but certainly not in orbit.

[Thygrrr]

This is the best video I found on the topic. 

[Technical Ben]

I don't think anyone has been against the idea of this being a photon drive. The problem is that measurements have been stronger than a 100% photon drive should be, and that using such a cavity setup should theoretically be less than 100%...

 

Though such an above idea... does match the "propeller" idea that some have been putting forwards (that like a propeller, it pushes against something, in this case some standing wave).

Edited November 10, 2016 by Technical Ben

[Nefrums]

even with my limited understanding of this the vidio appears to be missing some crucial elements. Like that the shape of the cavity causes the Vg so decrease towards one end. This decrease in Vg should (in my uniformed opinion) cause as much momentum transfer to the cavity as the difference in Vg.  So the resulting thrust on the cavity should be 0.

 

[p1t1o]

1 hour ago, Nefrums said:

even with my limited understanding of this the vidio appears to be missing some crucial elements. Like that the shape of the cavity causes the Vg so decrease towards one end. This decrease in Vg should (in my uniformed opinion) cause as much momentum transfer to the cavity as the difference in Vg.  So the resulting thrust on the cavity should be 0.

 

Its also weird that the video purports to "explain the science" behind the emdrive when no one knows how it really works yet...

[Thygrrr]

The science is solid. 

The phantom force people speak of, I believe this came from a misunderstanding and press sensation bias. 

Though -  my late father actually researched a little in this field and I'm still trying to piece together what he found, because he also mentioned a weird effect that defied his physics understanding. (he was a bona fide physicist and repeatedly worked with NASA, though that was mostly mass spectrometry and leak detection tech). 

I'm sadly more of a computer scientist so my understanding is very limited. 

Edited November 10, 2016 by Thygrrr

[p1t1o]

1 hour ago, Thygrrr said:

The science is solid. 

It is? Then what is all this hoo-haa about?

1 hour ago, Thygrrr said:

The phantom force people speak of, I believe this came from a misunderstanding and press sensation bias. 

This I can believe, science reporting in general is quite terrible.

[Steel]

1 hour ago, Thygrrr said:

The science is solid. 

The science is in fact NOT solid. Despite what the video says, radiation pressure is dependent on the phase velocity, not the group velocity of the light. These are two very different quantities.

EDIT: Also the part where he "derives" the "thrust equation" for an m-drive is just horrible to watch for anyone who has any understanding of science and maths.

EDIT 2: wow, it gets much worse! This guy apparently has zero understanding of conservation of momentum or Newton's laws

Edited November 10, 2016 by Steel

[Thygrrr]

Hmm I wasn't able to follow him everywhere, so what do you see as problematic ? 

[Steel]

Let's start with how he says it generates thrust: He says there are two different forces at each end due to different group velocities. In fact the forces on each end are the same because radiation pressure is dependent on the phase velocity (not the group velocity as he claims), which is the same (and is equal to c) going both ways, regardless of how the cavity is shaped.

Secondly, the part where he derives the equation. He uses F = ma. This is fine, until the part he changes a for v/t. This is ok so long as (a) you're 12 years old and trying to work constant acceleration for your physics homework and (b) if you keep in mind that v should in fact be Δv, the change in the cavity's velocity. He somehow confuses the v in v/t (which is the cavity's change in velocity) with the group velocity of the wave - which we already know has nothing to do with the force anyway. Just because the two things have the symbol v in them doesn't mean that they refer to the same thing or can be used interchangeable (also he uses E = mc² to come up with some sort of weird "effective photon mass" thing in his derivation, which is particularly bad).

The final straw for me is when he says this force is doubled due to Newton's third law. If what he said is true, every time you bounced a ball against a wall, there would be the force on the wall by the ball and then this force would, for some reason, be doubled by the wall's reaction force against this (at this point I realised this guy had no grasp of even basic physics, let alone how his own invention supposedly works)

Also the bit where he talked about conservation of momentum is just so badly wrong that I have neither the time, nor the energy to go through the whole thing.

Edited November 10, 2016 by Steel

[NeverEnoughFuel!!]

Well this is relatively fresh...