3 ms·

The article mentions NASA tested it. Is that untrue or less true than it sounds? Genuinely curious.

TrevorJ 10y ago
It's true - I think the general issue is that the forces produced are tiny, so it's hard to rule out some other effect coming into play and for the EM drive to work would mean overturning a decent amount of 'settled' physics understanding so the evidence needs to be pretty incontrovertible.
rybosome 10y ago
Here is a good summary of the state of EmDrive testing (as of a year ago): https://www.reddit.com/comments/34cq1b/ https://www.reddit.com/comments/34cq1b/ TL;DR - a small, experimental division within NASA called Eagleworks tested the device. They are a very small group with very limited funding tasked with exploring unconventional theories around advanced propulsion. Their results were not published in a peer-reviewed journal, and there is considerable disagreement as to the validity of their experiment. They are continuing to refine their experiments, and the last update provided is that they intend to publish a peer-reviewed paper describing an experiment that successfully breached 100uN of thrust, which was the target needed for JPL and others to attempt to replicate their results.
- HCIdivision17 10y ago
  Thanks for the link - that comment is great. I gotta quote one line that is just cool, though: 4. A test at 50 W of power during which an interferometer (a modified Michelson device) was used to measure the stretching and compressing of spacetime within the device, which produced initial results that were consistent with an Alcubierre drive fluctuation. Which is just really cool. The followup sums up my fascination with the whole thing niceley: Test #4 was performed, essentially, on a whim by the research team as they were bouncing ideas off each other, and was entirely unexpected. They are extremely hesitant to draw any conclusions based on test #4, although they certainly found it interesting. That right there is science in progress: a hint of something interesting, a test leading to another test leading to another, each interesting in their own right. It's still not clear if something spectacular is going on, but I think it's undeniably interesting. Careful reexamination can yeild all manner of useful insights! (Off topic, but along the lines of closer examination, see https://news.ycombinator.com/item?id=9020065 https://news.ycombinator.com/item?id=9020065 for how some careful (and extensive!) experimentation helped illuminate sodium's reaction with water. Not just how much work was needed to tease out the details!)
  - noir_lord 10y ago
    > The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...' - Isaac Asimov. This could be complete bunkum but it's fun watching anyway as an interested bystander.
  - imglorp 10y ago
    If that thing is really stretching and compressing spacetime, and a Michaelson Morely interferometer can see that in theory, then something like LIGO would be equipped to measure it.
rimunroe 10y ago
A very small team[1] at NASA did indeed test it, but their results had problems[2]. Also, results from any source can be reported on poorly. [1] https://en.wikipedia.org/wiki/Advanced_Propulsion_Physics_Laboratory https://en.wikipedia.org/wiki/Advanced_Propulsion_Physics_La... [2] https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster#EmDrive_2 https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster#Em...
ComputerGuru 10y ago
Yup. At the EagleWorks lab which many people confuse as not part of NASA (though it very much is, and exists for testing exactly stuff like this) https://en.m.wikipedia.org/wiki/Advanced_Propulsion_Physics_Laboratory https://en.m.wikipedia.org/wiki/Advanced_Propulsion_Physics_...
hannob 10y ago
sorta, kinda... It is true that some scientists at NASA have done experiments with this where they claimed to have found some result. A lot of other scientists were very sceptical about these results and said they weren't rigorous enough in eliminating possible errors. The same scientists have done other controversial experients and made claims that other scientists found overhyped. NASA is a big institution. It's a very different thing to say "NASA said XY" or "someone at NASA claimed to have found XY".
gaur 10y ago
> The article mentions NASA tested it. NASA is so big that that statement doesn't really mean anything.

It's true - I think the general issue is that the forces produced are tiny, so it's hard to rule out some other effect coming into play and for the EM drive to work would mean overturning a decent amount of 'settled' physics understanding so the evidence needs to be pretty incontrovertible.

rybosome 10y ago

Here is a good summary of the state of EmDrive testing (as of a year ago): https://www.reddit.com/comments/34cq1b/ https://www.reddit.com/comments/34cq1b/ TL;DR - a small, experimental division within NASA called Eagleworks tested the device. They are a very small group with very limited funding tasked with exploring unconventional theories around advanced propulsion. Their results were not published in a peer-reviewed journal, and there is considerable disagreement as to the validity of their experiment. They are continuing to refine their experiments, and the last update provided is that they intend to publish a peer-reviewed paper describing an experiment that successfully breached 100uN of thrust, which was the target needed for JPL and others to attempt to replicate their results.

HCIdivision17 10y ago
Thanks for the link - that comment is great. I gotta quote one line that is just cool, though: 4. A test at 50 W of power during which an interferometer (a modified Michelson device) was used to measure the stretching and compressing of spacetime within the device, which produced initial results that were consistent with an Alcubierre drive fluctuation. Which is just really cool. The followup sums up my fascination with the whole thing niceley: Test #4 was performed, essentially, on a whim by the research team as they were bouncing ideas off each other, and was entirely unexpected. They are extremely hesitant to draw any conclusions based on test #4, although they certainly found it interesting. That right there is science in progress: a hint of something interesting, a test leading to another test leading to another, each interesting in their own right. It's still not clear if something spectacular is going on, but I think it's undeniably interesting. Careful reexamination can yeild all manner of useful insights! (Off topic, but along the lines of closer examination, see https://news.ycombinator.com/item?id=9020065 https://news.ycombinator.com/item?id=9020065 for how some careful (and extensive!) experimentation helped illuminate sodium's reaction with water. Not just how much work was needed to tease out the details!)
- noir_lord 10y ago
  > The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...' - Isaac Asimov. This could be complete bunkum but it's fun watching anyway as an interested bystander.
- imglorp 10y ago
  If that thing is really stretching and compressing spacetime, and a Michaelson Morely interferometer can see that in theory, then something like LIGO would be equipped to measure it.

rimunroe 10y ago

A very small team[1] at NASA did indeed test it, but their results had problems[2]. Also, results from any source can be reported on poorly. [1] https://en.wikipedia.org/wiki/Advanced_Propulsion_Physics_Laboratory https://en.wikipedia.org/wiki/Advanced_Propulsion_Physics_La... [2] https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster#EmDrive_2 https://en.wikipedia.org/wiki/RF_resonant_cavity_thruster#Em...

ComputerGuru 10y ago

Yup. At the EagleWorks lab which many people confuse as not part of NASA (though it very much is, and exists for testing exactly stuff like this) https://en.m.wikipedia.org/wiki/Advanced_Propulsion_Physics_Laboratory https://en.m.wikipedia.org/wiki/Advanced_Propulsion_Physics_...

hannob 10y ago

sorta, kinda... It is true that some scientists at NASA have done experiments with this where they claimed to have found some result. A lot of other scientists were very sceptical about these results and said they weren't rigorous enough in eliminating possible errors. The same scientists have done other controversial experients and made claims that other scientists found overhyped. NASA is a big institution. It's a very different thing to say "NASA said XY" or "someone at NASA claimed to have found XY".

gaur 10y ago

> The article mentions NASA tested it. NASA is so big that that statement doesn't really mean anything.