13 ms·

Link? According to the article, "And last year, NASA conducted its own tests in a vacuum to rule out movement of air as the origin of the force." So either the

Link? According to the article, "And last year, NASA conducted its own tests in a vacuum to rule out movement of air as the origin of the force." So either the story is wrong or you are, but both can't be right, right?

XorNot 11y ago
Huh, seems I'm wrong - there was an actual high vacuum test -http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083 http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083 Paywalled on that link though so I can't see the details which tend to be everything since last time a vacuum chamber was involved it wasn't actually evacuated.
- fapjacks 11y ago
  A German team tested it in a vacuum. It's mentioned with sources on the EmDrive's Wikipedia page.
  - Animats 11y ago
    Yes, and that report indicates a null result. But they also indicate that the driving frequency was way mistuned for the cavity. They were driving it with a magnetron from a microwave oven, which output a frequency far from optimal. This indicates a low-budget operation, and not one in a lab with lots of microwave gear. NASA, at least, has a microwave source with the right frequency. But they report "researchers were now working on a new integrated analytical tool to help separate EmDrive thrust pulse waveform contributions from the thermal expansion interference". That indicates this thing is still way too close to the noise threshold. Back when cold fusion was taken seriously, I went to a Stanford talk where a physicist described their attempts to replicate the experiment. At first, he said, they had the apparatus surrounded with radiation detectors and alarms, in case it produced a dangerous burst of neutrons. After a while, they realized that wasn't going to happen. They discovered that the effect being measured was about twice background radiation. Then they discovered that people moving around the apparatus affected neutron readings by more than the measured amount. (Humans are mostly water, and thus reflect neutrons.) Finally they moved the experiment to a "neutron cube" built from lead bricks, where the background radiation was very low. The measured neutron readings went way down. That's what it's like when a phenomenon is near the noise threshold.
    - batbomb 11y ago
      > That's what it's like when a phenomenon is near the noise threshold. That's not really noise level, that's just unknown systematic errors.
      - readams 11y ago
        he just means here are all kinds of piddly effects that will throw it off. If you switch the thing on and you get a huge effect size with high signal/noise you don't need to worry about stuff like who is standing near the tank other than to worry that they're being irradiated with fast neutrons.
    - taneq 11y ago
      If you're that low-budget why would you not just size the cavity to match a commercial microwave oven magnetron?
    - angersock 11y ago
      My understanding was that the report didn't show a null report: The device produced positive thrusts in the positive direction and negative thrusts in the negative direction of about 20 micronewtons in a hard vacuum, consistent with the low Q factor. Besides being tested horizontally in both directions on the torsion pendulum, the cavity was also set upwards as a "null" configuration. However, this vertical test intended to be the experimental control showed an anomalous thrust of hundreds of micronewtons that could be caused by a magnetic interaction with the power feeding lines going to and from liquid metal contacts in the setup. (from Wikipedia) Am I misreading this somehow?
    - madaxe_again 11y ago
      The German team did it for a BBC documentary on "junk science" - they were looking for a null result, so while I take claims that the tech works with a pinch of salt, the same applies here. Everybody acts to their own interests.
      - raverbashing 11y ago
- JoBrad 11y ago
  Nasa's test and their results are publically available on Nasa's website. http://ntrs.nasa.gov/search.jsp?R=20140009930&hterms=RF+Test+Device&qs=N%3D0%26Ntk%3DAll%26Ntt%3DRF%2520Test%2520Device%26Ntx%3Dmode%2520matchallpartial%26Nm%3D123%7CCollection%7CNASA%2520STI%7C%7C17%7CCollection%7CNACA http://ntrs.nasa.gov/search.jsp?R=20140009930&hterms=RF+Test...
jasonwatkinspdx 11y ago
The article is very sweeping. You're getting only the pro side, not any of the critical view. People are still heavily debating the experiments. It has not been empirically demonstrated to a standard sufficient to call the thrust real. That's why only a very small community is working on this. "NASA" in this context means EagleWorks is letting a couple people spend a bit of spare time and resources on it as a speculative project. Mike McCulloch's work is interesting, but it's quite far from any mainstream acceptance or testing, as he himself would admit. It's mostly independent of the EmDrive stuff, but the enthusiast community has latched onto it as a way to escape the unpleasant reality that established physics says the EmDrive is a perpetual motion machine. I'm glad EmDrive is giving his work a boost because I think it should be tested, but there should be much better ways of testing Modified inertia by a Hubble-scale Casimir effect than the EmDrive (he's got a couple blog posts about it if you're curious).
- techdragon 11y ago
  Its arguably a possibility that we are so unsure of the effect because we have scientists "cautiously creeping" so as to not hurt their future reputation. There was anomalous scaling in the observed effects in one Chinese research teams results, but it has not been repeated because full reproduction and pushing past their power levels would cost some decent money. Seems stupid the (possibly) most groundbreaking advance in propulsion ever made, can't get a million or two when we collectively gamble more than that each day at casinos lotteries and horses races. We could quickly eliminate the question of "is this anomalous results from bad experiment design" with a bigger experiment that would make such flaws more evident. Yet we waste time instead of money.
  - marcus_holmes 11y ago
    I think you've nailed it there. A professional scientist can't take this seriously because the reputational risk is so high. Science needs to embrace failure more!
    - madaxe_again 11y ago

XorNot 11y ago

Huh, seems I'm wrong - there was an actual high vacuum test -http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083 http://arc.aiaa.org/doi/pdf/10.2514/6.2015-4083 Paywalled on that link though so I can't see the details which tend to be everything since last time a vacuum chamber was involved it wasn't actually evacuated.

fapjacks 11y ago
A German team tested it in a vacuum. It's mentioned with sources on the EmDrive's Wikipedia page.
- Animats 11y ago
  Yes, and that report indicates a null result. But they also indicate that the driving frequency was way mistuned for the cavity. They were driving it with a magnetron from a microwave oven, which output a frequency far from optimal. This indicates a low-budget operation, and not one in a lab with lots of microwave gear. NASA, at least, has a microwave source with the right frequency. But they report "researchers were now working on a new integrated analytical tool to help separate EmDrive thrust pulse waveform contributions from the thermal expansion interference". That indicates this thing is still way too close to the noise threshold. Back when cold fusion was taken seriously, I went to a Stanford talk where a physicist described their attempts to replicate the experiment. At first, he said, they had the apparatus surrounded with radiation detectors and alarms, in case it produced a dangerous burst of neutrons. After a while, they realized that wasn't going to happen. They discovered that the effect being measured was about twice background radiation. Then they discovered that people moving around the apparatus affected neutron readings by more than the measured amount. (Humans are mostly water, and thus reflect neutrons.) Finally they moved the experiment to a "neutron cube" built from lead bricks, where the background radiation was very low. The measured neutron readings went way down. That's what it's like when a phenomenon is near the noise threshold.
  - batbomb 11y ago
    > That's what it's like when a phenomenon is near the noise threshold. That's not really noise level, that's just unknown systematic errors.
    - readams 11y ago
      he just means here are all kinds of piddly effects that will throw it off. If you switch the thing on and you get a huge effect size with high signal/noise you don't need to worry about stuff like who is standing near the tank other than to worry that they're being irradiated with fast neutrons.
  - taneq 11y ago
    If you're that low-budget why would you not just size the cavity to match a commercial microwave oven magnetron?
  - angersock 11y ago
    My understanding was that the report didn't show a null report: The device produced positive thrusts in the positive direction and negative thrusts in the negative direction of about 20 micronewtons in a hard vacuum, consistent with the low Q factor. Besides being tested horizontally in both directions on the torsion pendulum, the cavity was also set upwards as a "null" configuration. However, this vertical test intended to be the experimental control showed an anomalous thrust of hundreds of micronewtons that could be caused by a magnetic interaction with the power feeding lines going to and from liquid metal contacts in the setup. (from Wikipedia) Am I misreading this somehow?
  - madaxe_again 11y ago
    The German team did it for a BBC documentary on "junk science" - they were looking for a null result, so while I take claims that the tech works with a pinch of salt, the same applies here. Everybody acts to their own interests.
    - raverbashing 11y ago
JoBrad 11y ago
Nasa's test and their results are publically available on Nasa's website. http://ntrs.nasa.gov/search.jsp?R=20140009930&hterms=RF+Test+Device&qs=N%3D0%26Ntk%3DAll%26Ntt%3DRF%2520Test%2520Device%26Ntx%3Dmode%2520matchallpartial%26Nm%3D123%7CCollection%7CNASA%2520STI%7C%7C17%7CCollection%7CNACA http://ntrs.nasa.gov/search.jsp?R=20140009930&hterms=RF+Test...

jasonwatkinspdx 11y ago

The article is very sweeping. You're getting only the pro side, not any of the critical view. People are still heavily debating the experiments. It has not been empirically demonstrated to a standard sufficient to call the thrust real. That's why only a very small community is working on this. "NASA" in this context means EagleWorks is letting a couple people spend a bit of spare time and resources on it as a speculative project. Mike McCulloch's work is interesting, but it's quite far from any mainstream acceptance or testing, as he himself would admit. It's mostly independent of the EmDrive stuff, but the enthusiast community has latched onto it as a way to escape the unpleasant reality that established physics says the EmDrive is a perpetual motion machine. I'm glad EmDrive is giving his work a boost because I think it should be tested, but there should be much better ways of testing Modified inertia by a Hubble-scale Casimir effect than the EmDrive (he's got a couple blog posts about it if you're curious).

techdragon 11y ago
Its arguably a possibility that we are so unsure of the effect because we have scientists "cautiously creeping" so as to not hurt their future reputation. There was anomalous scaling in the observed effects in one Chinese research teams results, but it has not been repeated because full reproduction and pushing past their power levels would cost some decent money. Seems stupid the (possibly) most groundbreaking advance in propulsion ever made, can't get a million or two when we collectively gamble more than that each day at casinos lotteries and horses races. We could quickly eliminate the question of "is this anomalous results from bad experiment design" with a bigger experiment that would make such flaws more evident. Yet we waste time instead of money.
- marcus_holmes 11y ago
  I think you've nailed it there. A professional scientist can't take this seriously because the reputational risk is so high. Science needs to embrace failure more!
  - madaxe_again 11y ago