7 ms·

'Impossible' EmDrive Space Thruster May Really Be Impossible

45 points by jackfoxy 8y ago

ballenf 8y ago
The measured thrust was evidently interactions of electrical cabling with the Earth's magnetic field as per the new study.
- yummybear 8y ago
  Wasn’t that just a theory - has it been conclusively proofed it was the cabling?
nategri 8y ago
Yes, the laws of physics are rarely to be messed with. Doesn't mean we should stop trying, as long as we stay grounded.
- the-pigeon 8y ago
  We still can't bridge classical mechanics and quantum mechanics so obviously we are missing at least one huge piece of the puzzle.
  - throwaway37585 8y ago
    You mean general relativity?
  - marcosdumay 8y ago
    What problems with bridging them do you have in mind? I thought this was entirely solved.
    - 21 8y ago
      Einstein theory of gravity is still considered classic (since it's not quantified).
  - nategri 8y ago
    We can approach classical behavior from the quantum mechanical formulism via the application of the Ehrenfest theorem [1] in limiting situations (e.g. as per the article, cases where "the wave function is highly concentrated around a point"). I suspect you are instead referring to unification of general relativity with quantum mechanics, which has indeed not yet been accomplished. (However, it's worth noting that quantum mechanics has been found to be consistent with special relativity, and the union of the two yields much of modern particle physics). [1] https://en.wikipedia.org/wiki/Ehrenfest_theorem https://en.wikipedia.org/wiki/Ehrenfest_theorem
- 21 8y ago
  Sometimes the laws of physics change.
searine 8y ago
I wanted to believe it could be true, but that's the beauty of science. Test. Test and re-test. If the conclusion isn't want you want it to be, refine the accuracy of your test and increase sample size. If you test is already at maximum resolution, then tough tacos buddy.
- tabtab 8y ago
  Re: "I wanted to believe it could be true" Indeed. Star Trek dreams shatnered, I mean shattered. Sorry, no visiting green Orion space-babes. Live long and cuss. And, wouldn't somebody typically check electrical interaction with Earth's magnetic field? It's a factor already known about.
gaze 8y ago
Of course it is. Nearly every physicist knew this was quackery from day one. It should of course be tested properly, but nobody should be surprised.
- tabtab 8y ago
  Just because one cannot explain a phenomenon using known physics doesn't mean they should outright dismiss it. A good many discoveries started with, "Hmmm, that's odd...". And, science mistakes are good lessons, such as "why didn't we think to check that?"
  - scott_s 8y ago
    I think you are not doing credit to the many physicists and science communicators who thoroughly explained why this was quackery. And in a world with quacks - people who have deceived themselves or are deliberately deceiving others - I think it is defensible for most of us to ignore people who claim to have violated the conservation of momentum with scant evidence.
    - dwringer 8y ago
      If it had been thoroughly explained then there wouldn't have been anomalous experimental results. I agree that it's rather likely that we're seeing experimental artefacts rather than new unexplored areas of physical law, but we must scientifically explain the results or else be very cautious, in general, when declaring something to be impossible. As the joke goes, that is well known to be the surest way in science to eventually be proven wrong. Even if it turns out these pseudoscientific dismissals were reaching the correct conclusion; well, as they say, even a stopped clock is right twice a day.
      - pixelcloud 8y ago
        It find it super funny how it was a cable related issue just like this famous one https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly https://en.wikipedia.org/wiki/Faster-than-light_neutrino_ano...
larkeith 8y ago
Unsurprising, but still unfortunate.
alan 8y ago
Hmm, could we use interactions with the Earth's magnetic field for thrust when in LEO? With the Sun's magnetic field? It would be slow going.
- hooo 8y ago
  Yes, I remember reading about people using this to deorbit satellites... though I can't find the link right now.
- db48x 8y ago
  Yes, satellites already do this.
- cheesepizza1077 8y ago
  Yes there are various forms of electromagnetic drives that use the earths magnetic field for small tasks like rotation and (maybe) station keeping. There are a few types, some which use propellant, and some that do not. More info here: https://en.m.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion https://en.m.wikipedia.org/wiki/Electrically_powered_spacecr...
- sigstoat 8y ago
  this is suggested frequently in these threads. it is already used in the very limited application where it is useful. https://en.wikipedia.org/wiki/Magnetorquer https://en.wikipedia.org/wiki/Magnetorquer "It is also impossible to control attitude in all three axes even if the full three coils are used, because the torque can be generated only perpendicular to the Earth's magnetic field vector." the non-earth orbiting mission i worked on didn't have any; it used little thrusters to desaturate its reaction wheels.
- ben_w 8y ago
  Yes, sort of, but that’s mainly useful for torque rather than thrust as thrust relies on (if I’m getting this right) field gradients rather than absolute field strength. It’s not nothing, but it might as well be. I back-of-enveloped a launch system with a very big magnet on the ground, supplying a much steeper gradient to push against, and it was still crazy expensive. (I wonder if it would be useful for skyhooks?)
daotoad 8y ago
Disappointing, but not really surprising. Yes the actual laws of physics can't be broken. We don't know those. We know an approximation of them based on centuries of careful observation and analysis. That approximation is incredibly good, too. It lets us make microchips with 7nm features, synthesize high atomic weight elements, and build spacecraft that have traversed the solar system. Even so, there are things we know we don't know and there are bound to be things we don't know we don't know. It would be nice if the EmDrive turned out to be a ground breaking demonstration of a hole in our model. We could probably squeeze a century of amazing science out of it. Not to mention the potential practical applications. But groundbreaking new discoveries that shake the foundations of a developed scientific theory are incredibly rare. So, as awesome as it could be if it were right, the odds were always against it.
- WJW 8y ago
  It is also much more likely for such a discovery to appear at the edge of our knowledge where our understanding of the rules is at least a bit fuzzy (like near black holes and whatnot). Something like EmDrive, which is in a regime that has been exhaustively tested, would be like discovering that Bin Laden was hiding in the Oval Office all along.
  - roywiggins 8y ago
    And the reason you didn't notice him was you needed to stand on your head and close one eye while chanting "abracadabra" before he could be seen.
  - sebnap 8y ago
    And then you found out about Operation Cyclone and your allusion gets some cracks!
  - cecilpl2 8y ago
    Which is really hard to do, because there aren't any corners in it. You need pull a Comey and hide in the drapes. EDIT: Apologies for the incorrect wording, I want to point out that you should stand AMONG the drapes, not IN the drapes.
bitL 8y ago
Pity, I really hoped we hacked the rounding error of the Universe :-/
DanielBMarkham 8y ago
I've been curiously watching this story although, like many other folks, I realized that the chances were greater than 99% that it wouldn't work out. What saddened me is the glee that some scientists and students took with dismantling all of these home experimenters. It was shameful to watch. What could have been a great opportunity for many to learn more about science and experimentation turned into a bunch of jackasses mocking a bunch of interested laymen. Not exactly the public image you want for your field of study.
- SubiculumCode 8y ago
  Agreed. Science is hard, especially without funding...but amateurs do contribute to science. This is most noted in astronomy.
  - DanielBMarkham 8y ago
    When I was 17, I took independent math study at my high school. (I had ran out of math classes to take by doubling up on them) The math department lead mentored me. One day I asked "Why is 1/0 undefined? You guys said you couldn't take the square root of a negative number, but when push came to shove, you just invented new stuff. Why not do that with 1/0?" He did not laugh at me or mock me. He looked earnestly at me and said "Why don't you try doing that. See what happens." I spent the next week or two trying to set up another number system. When I ran into trouble, I did a bunch of research at the library. When I came back the following week or two? I was able to give him a mini lecture on why it didn't work. Curiosity, humility, ignorance, and passion is the beating heart of science. The more we make it into some modern priesthood, pro football team, or rock band, the more the general public doesn't want anything to do with it.
    - flubert 8y ago
      https://en.wikipedia.org/wiki/Riemann_sphere https://en.wikipedia.org/wiki/Riemann_sphere
      - 8y ago
roywiggins 8y ago
It would have been a perpetual motion machine of the first kind (you could get an unlimited amount of energy out of it): https://arxiv.org/abs/1506.00494 https://arxiv.org/abs/1506.00494 The evidence for it was no better than the evidence for any other perpetual motion machine, there was nothing that made it special other than not claiming to be a perpetual motion machine (despite being one).
jwilk 8y ago
The paper discussed on HN: https://news.ycombinator.com/item?id=17096175 https://news.ycombinator.com/item?id=17096175

45 points by jackfoxy 8y ago

The measured thrust was evidently interactions of electrical cabling with the Earth's magnetic field as per the new study.

yummybear 8y ago
Wasn’t that just a theory - has it been conclusively proofed it was the cabling?

nategri 8y ago

Yes, the laws of physics are rarely to be messed with. Doesn't mean we should stop trying, as long as we stay grounded.

the-pigeon 8y ago
We still can't bridge classical mechanics and quantum mechanics so obviously we are missing at least one huge piece of the puzzle.
- throwaway37585 8y ago
  You mean general relativity?
- marcosdumay 8y ago
  What problems with bridging them do you have in mind? I thought this was entirely solved.
  - 21 8y ago
    Einstein theory of gravity is still considered classic (since it's not quantified).
- nategri 8y ago
  We can approach classical behavior from the quantum mechanical formulism via the application of the Ehrenfest theorem [1] in limiting situations (e.g. as per the article, cases where "the wave function is highly concentrated around a point"). I suspect you are instead referring to unification of general relativity with quantum mechanics, which has indeed not yet been accomplished. (However, it's worth noting that quantum mechanics has been found to be consistent with special relativity, and the union of the two yields much of modern particle physics). [1] https://en.wikipedia.org/wiki/Ehrenfest_theorem https://en.wikipedia.org/wiki/Ehrenfest_theorem
21 8y ago
Sometimes the laws of physics change.

searine 8y ago

I wanted to believe it could be true, but that's the beauty of science. Test. Test and re-test. If the conclusion isn't want you want it to be, refine the accuracy of your test and increase sample size. If you test is already at maximum resolution, then tough tacos buddy.

tabtab 8y ago
Re: "I wanted to believe it could be true" Indeed. Star Trek dreams shatnered, I mean shattered. Sorry, no visiting green Orion space-babes. Live long and cuss. And, wouldn't somebody typically check electrical interaction with Earth's magnetic field? It's a factor already known about.

gaze 8y ago

Of course it is. Nearly every physicist knew this was quackery from day one. It should of course be tested properly, but nobody should be surprised.

tabtab 8y ago
Just because one cannot explain a phenomenon using known physics doesn't mean they should outright dismiss it. A good many discoveries started with, "Hmmm, that's odd...". And, science mistakes are good lessons, such as "why didn't we think to check that?"
- scott_s 8y ago
  I think you are not doing credit to the many physicists and science communicators who thoroughly explained why this was quackery. And in a world with quacks - people who have deceived themselves or are deliberately deceiving others - I think it is defensible for most of us to ignore people who claim to have violated the conservation of momentum with scant evidence.
  - dwringer 8y ago
    If it had been thoroughly explained then there wouldn't have been anomalous experimental results. I agree that it's rather likely that we're seeing experimental artefacts rather than new unexplored areas of physical law, but we must scientifically explain the results or else be very cautious, in general, when declaring something to be impossible. As the joke goes, that is well known to be the surest way in science to eventually be proven wrong. Even if it turns out these pseudoscientific dismissals were reaching the correct conclusion; well, as they say, even a stopped clock is right twice a day.
    - pixelcloud 8y ago
      It find it super funny how it was a cable related issue just like this famous one https://en.wikipedia.org/wiki/Faster-than-light_neutrino_anomaly https://en.wikipedia.org/wiki/Faster-than-light_neutrino_ano...

larkeith 8y ago

Unsurprising, but still unfortunate.

alan 8y ago

Hmm, could we use interactions with the Earth's magnetic field for thrust when in LEO? With the Sun's magnetic field? It would be slow going.

hooo 8y ago
Yes, I remember reading about people using this to deorbit satellites... though I can't find the link right now.
db48x 8y ago
Yes, satellites already do this.
cheesepizza1077 8y ago
Yes there are various forms of electromagnetic drives that use the earths magnetic field for small tasks like rotation and (maybe) station keeping. There are a few types, some which use propellant, and some that do not. More info here: https://en.m.wikipedia.org/wiki/Electrically_powered_spacecraft_propulsion https://en.m.wikipedia.org/wiki/Electrically_powered_spacecr...
sigstoat 8y ago
this is suggested frequently in these threads. it is already used in the very limited application where it is useful. https://en.wikipedia.org/wiki/Magnetorquer https://en.wikipedia.org/wiki/Magnetorquer "It is also impossible to control attitude in all three axes even if the full three coils are used, because the torque can be generated only perpendicular to the Earth's magnetic field vector." the non-earth orbiting mission i worked on didn't have any; it used little thrusters to desaturate its reaction wheels.
ben_w 8y ago
Yes, sort of, but that’s mainly useful for torque rather than thrust as thrust relies on (if I’m getting this right) field gradients rather than absolute field strength. It’s not nothing, but it might as well be. I back-of-enveloped a launch system with a very big magnet on the ground, supplying a much steeper gradient to push against, and it was still crazy expensive. (I wonder if it would be useful for skyhooks?)

daotoad 8y ago

Disappointing, but not really surprising. Yes the actual laws of physics can't be broken. We don't know those. We know an approximation of them based on centuries of careful observation and analysis. That approximation is incredibly good, too. It lets us make microchips with 7nm features, synthesize high atomic weight elements, and build spacecraft that have traversed the solar system. Even so, there are things we know we don't know and there are bound to be things we don't know we don't know. It would be nice if the EmDrive turned out to be a ground breaking demonstration of a hole in our model. We could probably squeeze a century of amazing science out of it. Not to mention the potential practical applications. But groundbreaking new discoveries that shake the foundations of a developed scientific theory are incredibly rare. So, as awesome as it could be if it were right, the odds were always against it.

WJW 8y ago
It is also much more likely for such a discovery to appear at the edge of our knowledge where our understanding of the rules is at least a bit fuzzy (like near black holes and whatnot). Something like EmDrive, which is in a regime that has been exhaustively tested, would be like discovering that Bin Laden was hiding in the Oval Office all along.
- roywiggins 8y ago
  And the reason you didn't notice him was you needed to stand on your head and close one eye while chanting "abracadabra" before he could be seen.
- sebnap 8y ago
  And then you found out about Operation Cyclone and your allusion gets some cracks!
- cecilpl2 8y ago
  Which is really hard to do, because there aren't any corners in it. You need pull a Comey and hide in the drapes. EDIT: Apologies for the incorrect wording, I want to point out that you should stand AMONG the drapes, not IN the drapes.

bitL 8y ago

Pity, I really hoped we hacked the rounding error of the Universe :-/

DanielBMarkham 8y ago

I've been curiously watching this story although, like many other folks, I realized that the chances were greater than 99% that it wouldn't work out. What saddened me is the glee that some scientists and students took with dismantling all of these home experimenters. It was shameful to watch. What could have been a great opportunity for many to learn more about science and experimentation turned into a bunch of jackasses mocking a bunch of interested laymen. Not exactly the public image you want for your field of study.

SubiculumCode 8y ago
Agreed. Science is hard, especially without funding...but amateurs do contribute to science. This is most noted in astronomy.
- DanielBMarkham 8y ago
  When I was 17, I took independent math study at my high school. (I had ran out of math classes to take by doubling up on them) The math department lead mentored me. One day I asked "Why is 1/0 undefined? You guys said you couldn't take the square root of a negative number, but when push came to shove, you just invented new stuff. Why not do that with 1/0?" He did not laugh at me or mock me. He looked earnestly at me and said "Why don't you try doing that. See what happens." I spent the next week or two trying to set up another number system. When I ran into trouble, I did a bunch of research at the library. When I came back the following week or two? I was able to give him a mini lecture on why it didn't work. Curiosity, humility, ignorance, and passion is the beating heart of science. The more we make it into some modern priesthood, pro football team, or rock band, the more the general public doesn't want anything to do with it.
  - flubert 8y ago
    https://en.wikipedia.org/wiki/Riemann_sphere https://en.wikipedia.org/wiki/Riemann_sphere
    - 8y ago

roywiggins 8y ago

It would have been a perpetual motion machine of the first kind (you could get an unlimited amount of energy out of it): https://arxiv.org/abs/1506.00494 https://arxiv.org/abs/1506.00494 The evidence for it was no better than the evidence for any other perpetual motion machine, there was nothing that made it special other than not claiming to be a perpetual motion machine (despite being one).

jwilk 8y ago

The paper discussed on HN: https://news.ycombinator.com/item?id=17096175 https://news.ycombinator.com/item?id=17096175