scitation.aip.org
Just interested to hear what other physicists think of this paper. I just found it while looking for something else about EM waves, and it looked interesting.
I'll give you the tl;dr of the paper: EM Drives produce exhaust, thus not violating physical laws.
Also, I understand the skepticism. I was and still am doubtful that the EM Drive is anything more than /pop/sci hopes and dreams, but please read the paper before you /sage/
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According to the researchers, the exhaust being blasted out is actually light, photons that have become paired up with another out-of-phase photon in order to shoot out of the metal cavity and produce thrust.
>the two photons in those pairs are out of phase and have no net electromagnetic field.
>the exhaust photons become invisible from an electromagnetic point of view because they're being masked by their out-of-sync partner.
SO it shoots photons out the back.
How is this different from just having a source of light pointing out the back of your spaceship? Is the meme drive more efficient at creating photons than leds?
Do pairs of out-of-phase photons have less energy than the 2 would have separately?
you would need 100 000 times more energy than this thing is using to create enough photons for the measured thrust.
That's what I was thinking too. OH BOY THERE'S THE SAME AMOUNT OF THRUST AS THERE WOULD BE IF YOU OPENED UP A MICROWAVE OVEN!
I like how every time I've asked "well what if things like photons and electrons are flying out, wouldn't that make thrust?" and then everyone here screamed that was stupid.
I wasn't even suggesting the EM drive is a good idea, it was just a question that apparently somebody with an actual relevant degree answered.
it is stupid, this whole thing is stupid. that article is stupid.
if it does produce photons its just a photon rocket, but then its still breaking the laws of physics because the amount of photons needed for the measured thrust has more energy than is put in to it.
I find the theoretical part more interesting and compelling than the EMdrive specifics. This idea of paired photons embodying the vacuum is pretty damn elegant, and explains spontaneous virtual particles and other quantum bullshit quite naturally. de Broglie will be vindicated soon enough.
>that article is stupid.
It's not an article... This is an American Institute of Physics site, it's where papers are published.
Do you even have a degree?
>if it does produce photons its just a photon rocket, but then its still breaking the laws of physics because the amount of photons needed for the measured thrust has more energy than is put in to it.
How, exactly? Explain carefully, if you can.
The meme drive using 1J of energy to produce 0.0001Ns of momentum. If this is from photons then using [math] E = pc [/math] means the photons out the back contains E = 0.0001*300000000 = 30kJ of energy
So this thing is somehow creating 30 000 times the energy it uses.
Seems legit
Is this different than electrogravitics which has been known about since the 1920s?
en.m.wikipedia.org
In the 50s, every major aerospace company was working on electrogravitics, then you just stopped hearing about it. I presume it's just another technology that graduated to the world of black budgets.
mfw this is a century old technology.
>It's not an article... This is an American Institute of Physics site
you dont know what 'article' means, do you?
>How, exactly?
see
If something does produce more energy than the input, that does not mean it broke the laws of physics. It means we never understood the laws of physics to begin with. We are bitches to physics, not vice versa.
>that does not mean it broke the laws of physics. It means we never understood the laws of physics to begin with.
wat
>you dont know what 'article' means, do you?
In common parlance it certainly doesn't mean a peer-reviewed paper, that's for sure.
>see
Where does it say 1J of energy = 0.0001N of momentum? I ask because of this:
>We think that this characteristic sensitivity of interference phenomena manifested in the test runs where the mean thrust of 91.2 μN with 16.9 W was recorded at 1932.6 MHz corresponding to the first TM211 mode in the tapered cavity having a quality factor of about 7320 and the mean thrust of 50.1 μN with 16.7 W
Can you explain what this means?
I took ht largest measured thrust to power ratio, which is more than the paper is mentioning, but in this case
91.2 μN from 16.9 W
0.0000912 N from 16.9 J/s
0.0000912 N*s from 16.9 J
0.0000912/16.9 N*s from 1J
0.000005 N*s from 1J
So its actually worse
1932.6 MHz is the frequency they used, but doesn't matter in energy conservation.
TM211 mode I have no idea
quality factor of about 7320 is the fudge factor they use to make the math work.
and they said memes dont real
Thanks, but even if it did all work this idea seems kind of retarded anyway.
Whatever you're using for power generation would likely be a great thing to use for propulsion, wouldn't it? This is just adding a middleman that's not even good at what he does. They could take all this work put into this drive and shift it into comparatively simple fission fragment research. At best this drive is a massive energy hog for the thrust of a giggle fart.
No, that's the point. Also, the meme drive can run without traditional rocket fuel, which if you've ever played Kerbal Space Program, is a miracle. Meme drives run on electricity, so they can be solar powered. Think about satellites that never have to deorbit, or long distance spacecraft that only have to use fuel to get into orbit.
>Think about satellites that never have to deorbit, or long distance spacecraft that only have to use fuel to get into orbit.
I don't play video games, but that sounds like a job for a solar sail in my opinion.
Really long distance spacecraft are still going to need to generate their own electrical power the further they go away from the sun, and at that point it's just easier to use a direct propulsion method and far more efficient. I'm not some kind of expert who understands all this, I'm a nuts and bolts guy myself, but I do understand the basic stuff enough to recognize a problem.
I get the end goal, don't worry, I just think this is a dumb idea to get to it.
meme drive BTFO
What is this quality factor?
I think what he means is that it isn't constrained by the rocket equation but I agree a fission-fragment rocket would have been a better use of funds. At least it's not based on meme theory
not a Veeky Forums type of person but this was linked from /pol/ and im finding this interesting.
question though, if this turns out to be legit, on a scale of 1 to 10 how big of a change would it be? Could it solve other problems other than space travel? How much of a leap are we talking about here.
lolwut daz cray
>getting to Mars in 10 months
>cheap engines that aren't constrained by fuel weight
It would be pretty great. You probably couldn't use it outside of space though.
Because it is 6x the theoretical thrust of a photon drive.
I work at RF. Shit leaks out Errywhere. Prolly some surface waves coupling energy out through a crack or some such shit.
Sqeeeewk!
So they say that dark photon pairs tunnel through the cavity wall forming the 'exaust' that drives the meme. If so, why not simply connect the magnetron to a suitable horn antenna and let them all out, paired as well as single?
p=E/c, F=p/t --> F=P/c
Expect 3.33e-9 newton per watt, the 'legal limit'.
The authors mention 91.2 µN at 16.9 W (5.4 µN/W) and 50.1 µN at 16.7 W (3 µN/W).
The highest documented emdrive thrust (NWPU 2012) was 0.72 N at 25 kW or 28.8 µN/W or about 8640 times the legal limit.
quality factor has to do with resonance
Yea, just like me and everyone with half a brain said a year ago, it's shooting particle out the back. Fucking mongs.
how so? its still shooting photons out of the back as I understood it.
> Is this different than electrogravitics
Yes. The EM drive hasn't been conclusively debunked yet.
I don't know anything about science and just stop by sometimes to read some shit I don't understand and leave so bear with me here. How can these photons generate thrust in a vacuum when they have no mass?
>0.72 N at 25 kW
It was 2.5 kW, not 25.
Well if it works and could serve as a practical means for space transportation (at least small probes), then it's something we should be excited about.
That being said the emdrive probably doesn't work.
I don't see why people keep saying this- there are repeated tests which demonstrate thrust developing.
I wouldn't take those experimental "verifications" too seriously. You should do research of your own obviously, but from what I understand a lot of the experiments conducted had major flaws.
I have a feeling it works by ablation or photon generation- I certainly don't believe that CoM and N3L are violated. Regardless, this is still a novel technique for producing thrust.
>graduated to the world of black budgets
Certainly after WWII, some say since the 1920s.
>the experiments conducted had major flaws.
Most likely. The latest Chinese report suggests that only independent (self-contained) devices should be trusted. Any external connection (e.g. power supply or rf feed) introduces errors that are too hard to catch and quantify. J. Yang et al., Journal of Propulsion Technology 37, 362–371 (2016)
If it's ablation how long can we expect the "fuel" to last?
a giant battery takes much less to lift than a giant fuel tank, requiring even more fuel for lift off which is the primary source of cost and inhibitor in space launches
also when the fuel tank is empty, the ship has no way to move, regardless of its proximity to a sun. The meme drive will get at least a little energy even far away, and as long as it gets its momentum close to a sun it can drift to the next solar system without worrying about refueling as long as there is a star. For traditional fuel it would have to land, refill with fuel that it hopes any planets in the solar system have (if there are planets) and then relaunch wasting more fuel
>In the 50s, every major aerospace company was working on electrogravitics, then you just stopped hearing about it.
>I presume it's just another technology that graduated to the world of black budgets.
Instead of presuming, try actually reading the article you linked:
en.m.wikipedia.org
The things Brown was working on are simple (and cheap) enough that anyone could reproduce his work in their own garage.
If there were anything to this, we'd have flying cars by now, never mind "muh gubbermint consipricy".
>wat
Not him but...
The whole, main, central idea of science is that we should make our ideas match our observations, not the other way around.
No idea. It's all dependent on the velocity with which the particles are expelled.
That being said, that's just my pet theory- nothing to it beyond that