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Theory: how is this?

I was doing a lot of research about the EmDrive thruster, i find 50% papers says that it work and other 50% saying that the "thrust" is a product of the interaction with the magnetic field of the Earth. I also see this, EmDrive on cubesats?? And then i think, a 3U cubesat with very big solar array, can drive that cubesat from LEO to Moon orbit?

Thanks for any clarification.

Valentino Zaffrani
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    See “Magic Space Unicorns” disproven? Any technical write-ups of the explanation of Em-Drive results presented at Space Propulsion 2018? and also The “Em Drive” paper is out - need some help understanding it and finally What's the final word; *does the EmDrive drive work or not?* – uhoh Oct 19 '20 at 13:31
  • Yhea, but that was arround two years ago, the last paper that i add here was from this month – Valentino Zaffrani Oct 19 '20 at 13:33
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    There are several reasons to post links to related questions. The important one is to link them permanently so that people on this page will see the others (in the linked section) and people on those pages will then see your newer question which is a good thing, right? I don't know what that paper says nor if it is worth reading, but a website called "emdrive.com" is automatically a non-authoritative source in my book! What are they selling? – uhoh Oct 19 '20 at 13:36
  • If it's a legit paper, can we locate a less-biased source for it? Thanks! – uhoh Oct 19 '20 at 13:44
  • emdrive.com is the home page of SPR Ltd, which is the company founded by the creator of the thruster. You can find references to this page in tons of papers and big medias. – Valentino Zaffrani Oct 19 '20 at 13:48
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    My brain is hurting, but a read through suggests it is a legit(ish) drive, but not en EM reactionless drive, it is getting thrust by radiating microwaves https://en.wikipedia.org/wiki/Photon_rocket with the pros and cons there. Which does not match the graphs and listed powers in the article. So I think we have two different things being called "EM' which is probably not helping work out what is going on – GremlinWranger Oct 19 '20 at 13:53
  • Thats right haha – Valentino Zaffrani Oct 19 '20 at 13:55
  • @ValentinoZaffrani so if your question is not about the conservation law-violating EmDrive then maybe you can add some clarification to your question once this gets sorted out. – uhoh Oct 19 '20 at 13:58
  • @uhoh i think the EmDrive no violates any law – Valentino Zaffrani Oct 19 '20 at 13:59
  • is like a chamber with presure, but the presure are 3GHz frequency waves. http://www.emdrive.com/theorypaper9-4.pdf – Valentino Zaffrani Oct 19 '20 at 14:00
  • @ValentinoZaffrani, can I suggest you change the title to something like 'microwave drive for cubesats' and move the link up to the top, making it specific to this proposed drive. I think there is an interesting question here, but needs to be separated from the 'EM drive' that violated conservation of momentum a couple of years ago. My spherical cow guesses at the moment is that this might be useful for attitude control but not going to the moon, since it is basically a low efficiency solar sail that can be pointed in arbitrary directions. – GremlinWranger Oct 19 '20 at 14:01
  • @GremlinWranger maybe low efficiency, but think that is a motor with no fuel, if the papers and tests that i read are correct with this litle motor on a cubesat u can be on the moon in 4 hours, but probably this papers are totaly incorrect, right? – Valentino Zaffrani Oct 19 '20 at 14:10
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    @GremlinWranger see answer below, have I got it wrong or is this still a momentum non-conserving unicorn? It looks exactly like the Em Drive hocus pocus sealed, high-Q microwave cavity that mysteriously generates thrust for no good reason. – uhoh Oct 19 '20 at 14:16
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    @ValentinoZaffrani and like gas pressure, photon pressure on the inside of a closed container produces no net force. EmDrive is based on the sort of misunderstanding that would predict that a pressurized soda bottle would accelerate toward its base because the base has more surface area than the cap. – Christopher James Huff Oct 19 '20 at 14:35
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    @GremlinWranger for an actual real-world photon thruster (not the EmDrive), thrust only depends on power output. You just want to produce EM radiation with as little mass as possible, nothing is gained by producing it in a narrow band or having it more than mostly collimated. An incandescent filament and foil reflector would vastly outperform a microwave source, laser, etc. This question is about the EmDrive reactionless thruster/perpetual motion machine/free energy device, though. – Christopher James Huff Oct 19 '20 at 14:51
  • @GremlinWranger: The thrust is of order of a couple piconewtons. Too little to be of any use for anything beyond chip-probes like Breathrough Starshot, less than 1 gram and even there it's way underpowered. – SF. Oct 19 '20 at 15:06
  • Sounds like the same old bootstrap lifter to me. – Organic Marble Oct 19 '20 at 16:04

1 Answers1

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This is the same or similar unphysical stuff as before.

Then for 40W power inside cavity, the calculated Thrust T=20.44mN.

There is no propellant here. If 40 Watts were in the form of photons, then the thrust would be $P/c$ = 133 nanoNewtons. This generates 105 more momentum per unit time that it's allowed to.

What's the final word; does the EmDrive drive work or not?

It continues to work generating cash and website clicks and dreamy hope that interstellar flight could be achievable, and seems to be more successful than Mars One in doing that kind of... of... what's a good word for it?

What is was Mars One?

From this answer to Are they building on mars or do they have a camp there?

As everyone knows, the best way to check to see if something is a scam is to see if it has a website.

Lets see how long non-conservation of momentum can hold out!

uhoh
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  • Interesting way to think. and a last question, what happend if i add more magnetrons? like instead of one, i put four, i have more wave "presure" on my chamber? i mean, if u think, this is totaly possible, but is hard to see – Valentino Zaffrani Oct 19 '20 at 14:30
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    @ValentinoZaffrani I think this is totally impossible, as do most people. It violates conservation of momentum. Why is the “impossible” space drive impossible? – uhoh Oct 19 '20 at 15:32
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    And for those who for some reason believe it's somehow "more okay" to violate conservation of momentum than energy: it violates conservation of energy too. In http://www.emdrive.com/2Gupdate.pdf Shawyer explicitly claims the drive acts as a reversible electrical machine that will transform acceleration to power. This means you could just sit one on one end on the ground and have it constantly generate power from gravitational acceleration. (Shawyer makes numerous mistakes which make it clear he doesn't understand the equivalence principle.) – Christopher James Huff Oct 19 '20 at 16:12
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    So the final word is: NO, the EmDrive dont generate thrust. Thanks to all – Valentino Zaffrani Oct 19 '20 at 16:55
  • @ValentinoZaffrani I believe that's what most people think, but it's only been 3 hours since you've posted your question! Keep checking to see what other answers may be posted in the next few days. – uhoh Oct 19 '20 at 17:05
  • @ValentinoZaffrani technically it does, just so little/less than advertised throwing the whole thing off your spaceship is many magnitudes more useful – Topcode Oct 19 '20 at 18:42
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    @Topcode are you sure? It's a closed resonant cavity. It could generate 133 nanoNewtons if it beamed its 40 watts out the back, but it doesn't. The only propulsion it is capable of is the unexplained weak residuals in poorly designed experiments (I'm being opinionated there I know). I don't think that there are any physically accepted mechanisms by which this closed resonant cavity can propel, are there? – uhoh Oct 19 '20 at 18:45
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    @uhoh, im sure theres a miniscule amount of radiation that escapes and creates some thrust, didnt say it was useful in the slightest – Topcode Oct 19 '20 at 18:48
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    @Topcode there's always the Pioneer effect ;-) – uhoh Oct 19 '20 at 18:53
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    @ValentinoZaffrani On the experimental side, there's no clear evidence that it produces thrust, every improvement in measurement reduces the amount of thrust it might produce. On the theory side, there's no theoretical reason to think it should produce thrust, and very strong theoretical reasons to think that no such device can do so. The justifications for it are severely flawed: Shawyer clearly doesn't understand relativity, White's quantum vacuum nonsense is just technobabble...quantum vacuum fluctuations are not a plasma. – Christopher James Huff Oct 19 '20 at 21:39
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    @ValentinoZaffrani basically, it's as likely to produce thrust as any other random contraption thrown together from spare parts. That doesn't mean it doesn't produce thrust, but it'd be a miraculous coincidence if it did. It's not a productive approach to developing spacecraft propulsion. At best, if reactionless drives actually are possible, it's almost certainly a distraction from whatever mechanism actually allows them. – Christopher James Huff Oct 19 '20 at 21:43