I'd like to know the final verdict on the EmDrive (or EM Drive); does it work or not?
Some say yes, others say no, some say the measured effect was not propulsion, but just the energy radiated by the cables.
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asked Feb 29, 2020 at 20:40
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3$\begingroup$ See this answer. You may search for "em thruster" in Space Exploration. So I am sure the EM drive does not work. $\endgroup$– UweCommented Feb 29, 2020 at 20:48
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1$\begingroup$ It's a good question, and I think it would be good if we had a stand-alone question with a definitive and conclusive yes or no answer in the site. I assume most people will agree the answer is "no" since it violates some pretty fundamental principles of physics that always work without exception so that we call them laws. Note, if it can't be answered yes or no today, that does not mean we can't have the question. $\endgroup$– uhohCommented Mar 1, 2020 at 0:04
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$\begingroup$ chat started: chat.stackexchange.com/transcript/message/64722356#64722356 $\endgroup$– uhohCommented Nov 15, 2023 at 23:25
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1 Answer
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- There is no theoretical reason to think it would work. Its inventor based it on his fundamental misunderstandings of relativity and basic Newtonian mechanics. (Amusingly, Shawyer's analysis assumes Earth's surface is at absolute rest...he appears to be a geocentrist [1].) Alternative theoretical explanations are at the level of handwaving attempts to explain the claimed thrust shown in experiments, but:
- Each attempt at replication with more sensitive experiments results in smaller quantities of "possible signs of thrust". Oddly, they always seem to be right down at the level of noise and measurement error.
Lacking any sound theoretical or unambiguous observational reason to think it works, it is about as likely to work as any other conglomeration of RF electronics assembled without any understanding of physics.
[1]: Look at Shawyer's concepts on http://emdrive.com/hybridlaunch.html. He claims the EmDrive becomes less efficient at higher velocities (not relative to anything, but absolute velocity), and so uses it for "static thrust" because he believes there's something different between hovering above Earth's surface and accelerating at 9.8 m/s. He must have slept through the class where the equivalence principle was explained.
answered Mar 5, 2020 at 13:08
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2$\begingroup$ Can you add some references to back up your assertions? (I completely agree with your conclusion, and this question deserves a good answer.) Some links about the replication attempts, the geocentrist part, etc would be most helpful. Otherwise this is just somebody on the internet's opinion. $\endgroup$ Commented Mar 5, 2020 at 13:23
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2$\begingroup$ If you can cite the "Each attempt at replication with more sensitive experiments results in smaller quantities of "possible signs of thrust"" with links and show said decreasing numbers, that would be excellent. If you can't then as OM points out there's no way for readers to know if this is true or not, and so while this may be correct, it wouldn't be a good Stack Exchange answer. Someone else could say the opposite, the only way to refute it is with actual numbers. Thanks! $\endgroup$– uhohCommented Mar 5, 2020 at 13:36
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2$\begingroup$ No argument, I'll extend it with some references. One notable example, though: Shawyer's site has videos (emdrive.com/dynamictests.html) of an EmDrive rotating on a turntable, which would be a demonstration of forces vastly greater than those in the various replication attempts...if you believed it was from the drive and not the laptop (hard drive, fans, and all), power supply, coolant loop, etc. Amusingly, it appears to rotate the "wrong way". $\endgroup$ Commented Mar 5, 2020 at 22:39
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$\begingroup$ chat started: chat.stackexchange.com/transcript/message/64722356#64722356 $\endgroup$– uhohCommented Nov 15, 2023 at 23:25