4 ms·

Scientists pinpoint source of “impossible” EmDrive's thrust

38 points by dgudkov 6y ago

geoah 6y ago
Would have been more fun if they had proven it works hehe. > “When power flows into the EmDrive," he continued, "the engine warms up. This also causes the fastening elements on the scale to warp, causing the scale to move to a new zero point. We were able to prevent that in an improved structure.
yoz-y 6y ago
I assume they always "knew" the drive was not working and the real exercise was to find why the measurements failed? Which makes this finding interesting because they can design for better experiment next time?
- jfengel 6y ago
  What makes the finding interesting is that a lot of people really, really, really, really wanted it to work. They wanted big wins for free. They wanted fundamental science laws to fall. They wanted a revolution. They wanted it to come from somebody just playing around, rather than more boring incremental results by somebody who dragged their ass through a PhD and postdoc. And several agencies, including NASA, threw money at it. Why? Honestly, I'm not sure. A combination of really, really wishing it was right, and wanting to be able to say they looked. So to scientists this isn't really interesting at all. Just like with the faster-than-light neutrinos, they knew all along that it was a measurement error. The specific source of the measurement error is mildly interesting, but not a billionth as interesting as New Physics would have been. Everybody wants New Physics, including scientists. The scientists are just extremely doubtful that we're going to just stumble on it, because all that stuff is well-worn territory, and it's unlikely that there's something really obvious that they've missed. But it's not impossible, which means that this isn't the first story we've gotten like this, and it won't be the last. (It's probably not even the end of this one, to be honest. I'm sure people will keep working on this. But the scientists can legitimately stop.)
  - k__ 6y ago
    Couldn't it just be that some scientists saw a problem with an experiment and used the hype to gather money to get that problem fixed?
    - thoughtstheseus 6y ago
      Not much money either.
    - jfengel 6y ago
      It didn't start with scientists. It started with tinkerers (who prefer to be called "inventors", though I'm unable to find anything else that they've invented). It wasn't really an "experiment" in that it wasn't testing a well-defined hypothesis. It really was just a guess. For some reason it attracted the attention of Harold White, a genuine scientist who NASA employs to do nutjob work. It never produces anything. It looks for all the world as if NASA likes having a pet mad scientist they can trot out to say, "Look, we're taking your stupid ideas seriously, now leave us alone." He couldn't figure out why pumping vast amounts of energy into a thing produced a tiny effect he couldn't otherwise account for, though "it made something hot that you didn't measure" seems a pretty obvious answer. Entropy is squirrely, and we all knew that. It did attract White more hype, so I guess you're right on that score. And as the sibling post notes, it's not all that money, and it comes out of NASA's PR budget. It then attracted more money and that's the money (and time) that really feels wasted. No problem got fixed. It was just an expensive version of the "Is it possible that dark matter is made of the socks that disappear from my washing machine?" type questions that plague scientific Q&As.
  - PeterisP 6y ago
    Well, one way or another, once you get reproducible experimental results that conflict with known physics, someone has to do the due diligence in finding the flaw, it would be irresponsible to shrug and say "ah, must be a fluke, who cares why". Perhaps if we had a whole range of other promising avenues to explore for new phsyics (like natural scientists a century or two ago), then it would be different, but as of now it seems there's not much competition that's more promising than the EmDrive was.
jakedata 6y ago
At least the Mach Effect thruster had a half-plausible mass/energy sort of hand-wavy theory behind it. Alas it too has slipped fully into the realm of wishful thinking... in this universe anyway.
ampdepolymerase 6y ago
> The ability to generate thrust without having to carry the parasitic mass of fuel would be a game-changer in space This is poor phrasing. You can already do this with lasers. You just cannot do it sustainably.
hinkley 6y ago
I remember seeing a device that used flywheels to “generate lift” and I couldn’t help but noticing it involved counterrotating units, meaning that where they approached each other they were both spinning the same direction (up or down, I don’t recall which). I thought, “I bet this doesn’t work in a vacuum chamber”. Later I remembered rotor ships. He essentially stood a complex one on its ear, and made some math errors that backed up his discovery.

38 points by dgudkov 6y ago

Would have been more fun if they had proven it works hehe. > “When power flows into the EmDrive," he continued, "the engine warms up. This also causes the fastening elements on the scale to warp, causing the scale to move to a new zero point. We were able to prevent that in an improved structure.

yoz-y 6y ago

I assume they always "knew" the drive was not working and the real exercise was to find why the measurements failed? Which makes this finding interesting because they can design for better experiment next time?

jfengel 6y ago
What makes the finding interesting is that a lot of people really, really, really, really wanted it to work. They wanted big wins for free. They wanted fundamental science laws to fall. They wanted a revolution. They wanted it to come from somebody just playing around, rather than more boring incremental results by somebody who dragged their ass through a PhD and postdoc. And several agencies, including NASA, threw money at it. Why? Honestly, I'm not sure. A combination of really, really wishing it was right, and wanting to be able to say they looked. So to scientists this isn't really interesting at all. Just like with the faster-than-light neutrinos, they knew all along that it was a measurement error. The specific source of the measurement error is mildly interesting, but not a billionth as interesting as New Physics would have been. Everybody wants New Physics, including scientists. The scientists are just extremely doubtful that we're going to just stumble on it, because all that stuff is well-worn territory, and it's unlikely that there's something really obvious that they've missed. But it's not impossible, which means that this isn't the first story we've gotten like this, and it won't be the last. (It's probably not even the end of this one, to be honest. I'm sure people will keep working on this. But the scientists can legitimately stop.)
- k__ 6y ago
  Couldn't it just be that some scientists saw a problem with an experiment and used the hype to gather money to get that problem fixed?
  - thoughtstheseus 6y ago
    Not much money either.
  - jfengel 6y ago
    It didn't start with scientists. It started with tinkerers (who prefer to be called "inventors", though I'm unable to find anything else that they've invented). It wasn't really an "experiment" in that it wasn't testing a well-defined hypothesis. It really was just a guess. For some reason it attracted the attention of Harold White, a genuine scientist who NASA employs to do nutjob work. It never produces anything. It looks for all the world as if NASA likes having a pet mad scientist they can trot out to say, "Look, we're taking your stupid ideas seriously, now leave us alone." He couldn't figure out why pumping vast amounts of energy into a thing produced a tiny effect he couldn't otherwise account for, though "it made something hot that you didn't measure" seems a pretty obvious answer. Entropy is squirrely, and we all knew that. It did attract White more hype, so I guess you're right on that score. And as the sibling post notes, it's not all that money, and it comes out of NASA's PR budget. It then attracted more money and that's the money (and time) that really feels wasted. No problem got fixed. It was just an expensive version of the "Is it possible that dark matter is made of the socks that disappear from my washing machine?" type questions that plague scientific Q&As.
- PeterisP 6y ago
  Well, one way or another, once you get reproducible experimental results that conflict with known physics, someone has to do the due diligence in finding the flaw, it would be irresponsible to shrug and say "ah, must be a fluke, who cares why". Perhaps if we had a whole range of other promising avenues to explore for new phsyics (like natural scientists a century or two ago), then it would be different, but as of now it seems there's not much competition that's more promising than the EmDrive was.

jakedata 6y ago

At least the Mach Effect thruster had a half-plausible mass/energy sort of hand-wavy theory behind it. Alas it too has slipped fully into the realm of wishful thinking... in this universe anyway.

ampdepolymerase 6y ago

> The ability to generate thrust without having to carry the parasitic mass of fuel would be a game-changer in space This is poor phrasing. You can already do this with lasers. You just cannot do it sustainably.

hinkley 6y ago

I remember seeing a device that used flywheels to “generate lift” and I couldn’t help but noticing it involved counterrotating units, meaning that where they approached each other they were both spinning the same direction (up or down, I don’t recall which). I thought, “I bet this doesn’t work in a vacuum chamber”. Later I remembered rotor ships. He essentially stood a complex one on its ear, and made some math errors that backed up his discovery.