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We are specifically discussing scenarios where you are not pushing off anything.

Really? Your posts come off more as a catigorical negation of the whole concept of the EM drive, without any exceptions for rational explanations, such as the parts of my post that you deleted when you replied.

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This whole thing bothers me. Suppose that future experments will conform (I still doubt that they will) that it is working, what would that mean for Physics? Would it mean there are some kind of aether that the drive pushes aginst?

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This whole thing bothers me. Suppose that future experments will conform (I still doubt that they will) that it is working, what would that mean for Physics? Would it mean there are some kind of aether that the drive pushes aginst?

Define "working."

There are ways it could work that would have minimum changes to physiics. Then there are "theories" that violate the fundamental priniples on which we've built over a century of scientific progress. Or it could "work" via understood principles that we failed to account for in control expiriments.

I believe it's the first. The internet believes its the second, and skeptics are trying hard to maintain that it's the third.

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Would it mean there are some kind of aether that the drive pushes aginst?

Everyone, please don't hit me. But... Gravitons?

Edited by vger
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Everyone, please don't hit me. But... Gravitons?

Then it would mean this device somehow converts a part of electromagnetic spectrum (microwaves) into gravitation. Using household current as a source of power.

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Really? Your posts come off more as a catigorical negation of the whole concept of the EM drive, without any exceptions for rational explanations, such as the parts of my post that you deleted when you replied.

I can recommend some resources on improving reading comprehension. I don't see how else I can be of help. It might be good if you had an understanding of some basic concepts from physics, like preferred frame, but that might be a secondary issue.

Everyone, please don't hit me. But... Gravitons?

ANY massless, or nearly so, field gives you efficiency of 300MW/N. Photons, gravitons, neutrinos. Take your pick. They don't fit with the measurements.

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Then its just a photon drive, which can already be done more efficiently by putting a really big flashlight on your spacecraft. Power requirement for even one measly millinewton of thrust from a photon drive is enormous.

Well, they are. According to latest research, 700w magnetron produces 20micronewtons of thrust. So for 1 milinewton, you'd need 35000w magnetron.

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We are specifically discussing scenarios where you are not pushing off anything.

If you are pushing from something, there is momentum flux wherever the force is applied. This is precisely what I expect to be happening. The question is, what is it pushing from?

1) Something massless: Efficiency will be equal to that of a photon drive, which contradicts measurements.

2) Something massive and remote: This requires a massless mediator boson, which we ought to have discovered by now.

3) Something massive and proximate: There will be a detectable exhaust.

4. Many massless particles with weak unipolar magnetic field.

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This drive can only work if it doesnt violate conservation of momentum, but it can avoid that violation in exotic ways and still be "real".

If it doesnt violate conservation of momentum, it is pushing off of something, and physics remains relatively intact.

Reasonable assertion?

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Maybe the wiki could have a huge disclaimer that "the content within this page is just collected reposts of what random guys on an internet forum say, and is certainly riddled with basic physics errors." ?

Originally it was supposed to somewhere, it is possible someone has since taken it down. Uncertain.

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Everyone, please don't hit me. But... Gravitons?

Axions. An hypothesized form of dark matter.

After reading Tajmar's paper I've been starting to think it might really just all come down to some thermal outgassing effect or some such, though. And the accuracy in predicting the measured thrust would just be good (but blind) empirical modelling.

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Axions. An hypothesized form of dark matter.

After reading Tajmar's paper I've been starting to think it might really just all come down to some thermal outgassing effect or some such, though. And the accuracy in predicting the measured thrust would just be good (but blind) empirical modelling.

Pretty freaking unlikely. They only get to 100 degrees Fahrenheit.

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This drive can only work if it doesnt violate conservation of momentum, but it can avoid that violation in exotic ways and still be "real".

If it doesnt violate conservation of momentum, it is pushing off of something, and physics remains relatively intact.

Reasonable assertion?

Entirely reasonable. But that something has to be massive to get the power/thrust ratio we're seeing. (Again, conservation laws.) Which means we ought to be able to detect exhaust and/or recoil of some sort. Whether it works like a completely new kind of an ion drive, using resonance chamber to accelerate nearby charged particles, or somehow pushes off from nearby objects, we should be able to detect that. Which means, all of our measurements and experiments should still focus on mundane. We need to find something else that also has an extra force applied to it when EM Drive is active. This might require a more clever setup than ones I've seen so far.

Well, they are. According to latest research, 700w magnetron produces 20micronewtons of thrust. So for 1 milinewton, you'd need 35000w magnetron.

And for a photon drive, or anything that works from the same principle, it'd be 300,000W per 1 mN. This thing is still operating at an order of magnitude above maximum efficiency you can have with massless exhaust. So we can safely exclude photons, gravitational waves, neutrinos, or other (near-)massless particles/fields.

Edited by K^2
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How much has ablation been investigated as a potential source of thrust? Suppose that the microwaves somehow cause ablation of the chamber such that it spews out a few massive particles? Like a laser ablative drive, but with microwaves.

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How much has ablation been investigated as a potential source of thrust? Suppose that the microwaves somehow cause ablation of the chamber such that it spews out a few massive particles? Like a laser ablative drive, but with microwaves.

Should be easy to check. If its outgassing, its losing weight by scattering particles\molecules\atoms around. If device is noticeably lighter after the test, then we would find at least one suspect. Then again - Emdrive\Cannae devices were put on really precise scales or balancing beams to measure their thrust. Somehow i doubt all of the different teams performing experiments, would overlook the fact that they are missing couple of fraction of grams after every test. Mind - one of the teams consisted of NASA propulsion experts used to work with ion engines, which produce even wimpier thrust than Emdrive :)

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you could probibly check for ablation by weighing it, letting it run for a long time, and then weighing it again. any loss in mass should be detected thusly. i think thus far all test articles were run for very short times due to the durability of the electronics in a vacuum. (ninjad)

have they tried the device in different orientations with respect to earth's magnetic field? might there also be inducing eddy currents in the copper frustum giving it its own local magnetic field, which might attract it to the nearest metal wall of the vacuum chamber. i know they rotate the engine on the test apparatus to determine that the force is directional, but if the center of magnetism is offset, it could also cause the device to be attracted to the opposite wall of the chamber which is now closer. you could probibly check for magnetic effects with a magnetometer array to see what kind of fields are in play.

Edited by Nuke
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How much has ablation been investigated as a potential source of thrust? Suppose that the microwaves somehow cause ablation of the chamber such that it spews out a few massive particles? Like a laser ablative drive, but with microwaves.

Given the last attempt at a control produced measurable thrust with no microwaves, it's likely in another part of the setup entirely. Probably a magnetic effect.

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Tajmar's rig registered weakening thrust even after power was cut off. Apparently it matched closely drop in temperature, which would indicate it was indeed thermal interaction. Althought some users on nasaspaceflight forum criticised Tajmar for doing a shoddy job putting his drive together :)

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Tajmar's rig registered weakening thrust even after power was cut off. Apparently it matched closely drop in temperature, which would indicate it was indeed thermal interaction. Althought some users on nasaspaceflight forum criticised Tajmar for doing a shoddy job putting his drive together :)

What are the odds that a tangentially related effect has the same thrust bleed off as thermal emmision in vacuum?

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Should be easy to check. If its outgassing, its losing weight by scattering particles\molecules\atoms around. If device is noticeably lighter after the test, then we would find at least one suspect. Then again - Emdrive\Cannae devices were put on really precise scales or balancing beams to measure their thrust. Somehow i doubt all of the different teams performing experiments, would overlook the fact that they are missing couple of fraction of grams after every test. Mind - one of the teams consisted of NASA propulsion experts used to work with ion engines, which produce even wimpier thrust than Emdrive :)

Suppose that the device is ablating. Since we are talking micronewton scale thrust, and I assume that (in the case of outgassing) most of the thrust would be provided by the velocity of the outgoing reaction mass, a very tiny amount of material would have to be ejected to produce thrust over the course of the experiment, no? Could that mass be essentially immesurable with the present equipment?

Assuming ablation is happening, can we calculate roughly how many weight units of copper (?) have been lost over the course of the experiment, given force and time measurements from - say - Tajmar's experiment?

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I'm sure it can be done. If piece of copper produced X amount of thrust, it is reasonable to think it lost Y amount of mass used as a propellant - Rocket Equation is the way to go. But required math is way over the head of this lowly graduate of forestry school :) Give me an acorn, and i will grow a tree out of it LOL. Math? Not my forte.

Anyways, my gut says 35 degrees of heat is not enough to cause a copper drum to spew enough molecules - if it would be the case, any sufficiently hot frying pan would launch itself towards the roof. Not to mention Tajmar's team managed to reverse the thrust during the tests.

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Suppose that the device is ablating. Since we are talking micronewton scale thrust, and I assume that (in the case of outgassing) most of the thrust would be provided by the velocity of the outgoing reaction mass, a very tiny amount of material would have to be ejected to produce thrust over the course of the experiment, no? Could that mass be essentially immesurable with the present equipment?

Yes, and I agree that mass might not be the best way to measure it. Though, definitely an option to be looked into.

My other thought is that there is no way it's unlikely it's accelerating neutral exhaust to sufficient speeds to provide this thrust. If this is what happens, we should be looking for ablation + ionization. In a good vacuum chamber, ion trail would be way easier to detect than a mass change.

I'm sure someone will look into this possibility.

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