Cannae/EmDrive

[K^2]

Now it has been some speculations that efficiency tapper off over time so you can not get free energy, this is how it would work if the drive interact with something.

If it's interacting with something, I have no problems with it. I still insist that it's rather unlikely that it's interacting with something we haven't discovered yet, so we should be looking for conventional exhaust. But interaction with absolutely anything massive is fine in principle.

The original proposal, however, besides all other nonsense, suggested that propulsion is entirely reaction and interaction free. It suggests that radiation pressure inside the chamber is responsible for thrust. Which is just as absurd as thinking that you can design a barrel of just the right shape, so that you can inflate it with some gas, and have it fly off without expelling any of that gas, purely on an imbalance of forces from internal pressure. The whole thing is made worse by the fact that the entire notion arises from failure to understand basic EM equations.

So while I can see EMDrive working in principle due to an interaction with some sort of a medium, one thing we can pretty much guarantee is that it doesn't work the way its inventor said it should.

How does the EmDrive allow for generation of infinite energy? Last time I checked, the big problem is momentum isn't conserved, putting it at odds with Newtonian physics. Electricity is still required to produce thrust meaning that energy is still conserved even if we don't know how.

For starters, you can't violate conservation of momentum without violating conservation of energy. They are the same law. But in practical terms, it's also very easy to generate as much energy as you like. Attach a couple of these EMDrives to the ends of a rotor, which is attached to an electrical generator. If it's a reaction free drive, it will require same amount of energy to generate same amount of thrust at any speed. (Otherwise, speed relative to what?) And power generated by a generator is proportional to speed and torque applied. Torque is fixed, because that's determined by size of the rotor and thrust. So in order to get more energy, we just need to have the generator turn faster. No matter how much energy EMDrive takes, I can have generator spin faster and still produce more power. In fact, as much power as I like, within mechanical capabilities of the generator. Infinite power. QED.

If it takes a fixed amount of energy to generate thrust, either the amount of thrust must drop with speed, which happens if you are driving a car (speed relative to ground) or flying a plane (speed relative to air). Or you must have additional source of energy. This is a case with a rocket (extra energy comes from K.E. of exhaust.) But a reaction-free, exhaust-free drive cannot have either. No matter how it works, we can exploit it for free energy.

So according to original proposal, not only would we be able to have flying cars with EMDrives that consume power comparable to a Tesla, but it'd generate its own power while doing so, and you'd never have to charge it. Which sounds awesome on paper, but there are some very good reasons why it simply can't work that way. On top of the proposal itself being, frankly, just stupid.

[Sean Mirrsen]

If it's interacting with something, I have no problems with it. I still insist that it's rather unlikely that it's interacting with something we haven't discovered yet, so we should be looking for conventional exhaust. But interaction with absolutely anything massive is fine in principle.

The original proposal, however, besides all other nonsense, suggested that propulsion is entirely reaction and interaction free. It suggests that radiation pressure inside the chamber is responsible for thrust. Which is just as absurd as thinking that you can design a barrel of just the right shape, so that you can inflate it with some gas, and have it fly off without expelling any of that gas, purely on an imbalance of forces from internal pressure. The whole thing is made worse by the fact that the entire notion arises from failure to understand basic EM equations.

So while I can see EMDrive working in principle due to an interaction with some sort of a medium, one thing we can pretty much guarantee is that it doesn't work the way its inventor said it should.

The inventor, however, could be both right and wrong. (Suffice to say I never read the original proposal here, I'm just talking hypotheticals as usual) There could, in fact, be a net imbalance of forces within the device - if the forces within the device act on an unknown medium, the device does not experience whichever forces "disappear" into that medium. It would be a side effect of the interaction, rather than its cause, a case of "swaying trees cause wind", stupid in its own way, but possible.

For starters, you can't violate conservation of momentum without violating conservation of energy. They are the same law. But in practical terms, it's also very easy to generate as much energy as you like. Attach a couple of these EMDrives to the ends of a rotor, which is attached to an electrical generator. If it's a reaction free drive, it will require same amount of energy to generate same amount of thrust at any speed. (Otherwise, speed relative to what?) And power generated by a generator is proportional to speed and torque applied. Torque is fixed, because that's determined by size of the rotor and thrust. So in order to get more energy, we just need to have the generator turn faster. No matter how much energy EMDrive takes, I can have generator spin faster and still produce more power. In fact, as much power as I like, within mechanical capabilities of the generator. Infinite power. QED.

If it takes a fixed amount of energy to generate thrust, either the amount of thrust must drop with speed, which happens if you are driving a car (speed relative to ground) or flying a plane (speed relative to air). Or you must have additional source of energy. This is a case with a rocket (extra energy comes from K.E. of exhaust.) But a reaction-free, exhaust-free drive cannot have either. No matter how it works, we can exploit it for free energy.

Wouldn't the same thing happen with a photon drive? Yes, not reactionless, not exhaust-less, but with an exhaust velocity that equals c it has a functionally infinite ISP, and can do basically all the same things, it just converts electricity to thrust at a much lower rate.

Or how about an electric motor? I think you could replace that pair of EMDrives at any point with an electric motor of arbitrary size, that would generate more torque for the same electricity input, just because their rate of conversion of electricity to motive force is higher. The drive would still create no energy in the rotor-generator system, at best it would mitigate the generator's conversion losses. A perfect generator powered by a perfect EMDrive on its rotor would just spin forever, balanced at the point where the rotor resistance from the generator converting rotation to electricity equals the torque generated by the EMDrive. Same as with a perfect generator and a perfect electric motor, no matter the gear ratio between them.

Not really saying you're in the wrong there, just honestly curious as I thought that'd be the case.

[Ralathon]

Wouldn't the same thing happen with a photon drive? Yes, not reactionless, not exhaust-less, but with an exhaust velocity that equals c it has a functionally infinite ISP, and can do basically all the same things, it just converts electricity to thrust at a much lower rate.

Or how about an electric motor? I think you could replace that pair of EMDrives at any point with an electric motor of arbitrary size, that would generate more torque for the same electricity input, just because their rate of conversion of electricity to motive force is higher. The drive would still create no energy in the rotor-generator system, at best it would mitigate the generator's conversion losses. A perfect generator powered by a perfect EMDrive on its rotor would just spin forever, balanced at the point where the rotor resistance from the generator converting rotation to electricity equals the torque generated by the EMDrive. Same as with a perfect generator and a perfect electric motor, no matter the gear ratio between them.

Not really saying you're in the wrong there, just honestly curious as I thought that'd be the case.

The difference between a reactionless drive and a conventional photon drive is the lack of an exhaust.

Your kinetic energy depends on your frame of reference. A 1kg mass moving at 1ms has 0.5 J of energy. But if the mass is moving at 1000m/s it would have a whopping 0.5MJ.

Now factor in this EM drive. Suppose it works as advertised and for simplicity converts 100% of the provided electrical energy into kinetic energy.

Say we stand next to the drive and feed it 50 joulles. That's enough to speed up a 1kg drive by 10 m/s. So we see the drive accelerate from stationary to 10m/s.

Now lets put it on a train moving 1000m/s. You again feed it 50 joulles. Now this is only enough to accelerate it by sqrt(2*500050J) - 1000m/s ~ 0.5 m/s. So now that same amount of energy is only enough to accelerate your drive by half a meter per second.

This leads to a paradox. If you stand on the train next to the drive it's supposed to accelerate to 10m/s relative to you. But if you stand on the station it is supposed to accelerate by 0.5m/s.

This is because the kinetic energy of an object is entirely dependant on the reference frame you choose to use. There is no preferential frame of reference, so the drive does not 'know' how much it is supposed to accelerate.

This is why reactionless thrust breaks so much .... and why it's so easy to make infinite energy with it. In the case of that rotor it is assumed that the drive gives equal thrust regardless of the reference frame. This means you are generating more and more energy the faster it moves. So you can always pick some arbitrary speed where the drive is generating more energy than it consumes. If you have some form of exhaust you don't have this paradox since the missing energy is carried by the exhaust. Even with a photon drive the photons will redshift depending on the velocity, thus ensuring that no free energy is created.

Edited August 17, 2015 by Ralathon

[Sean Mirrsen]

This leads to a paradox. If you stand on the train next to the drive it's supposed to accelerate to 10m/s relative to you. But if you stand on the station it is supposed to accelerate by 0.5m/s.

This is because the kinetic energy of an object is entirely dependant on the reference frame you choose to use. There is no preferential frame of reference, so the drive does not 'know' how much it is supposed to accelerate.

Is it, again, not true for everything? Relativity works both ways. Drop the EMDrive, and use the other way we have of converting electricity to kinetic energy directly - a Gauss rail. Set the Gauss rail to deliver 500 joules of energy to its payload - you'll have the same paradox in regards to how much acceleration it should result in. A reactionless drive, even if reaction-less, still provides the action. It produces a force with no counterforce, but in the context of differing frames of reference, all it does is convert one type of energy to another.

A different kind of reactionless drive would not create a force, instead directly affecting velocity - however such a drive would cease affecting its velocity the moment it ceased operating, it cannot "coast" - lacking both reaction and action, it supplies no force. (if you ever played Star Control, the Arilou Skiff has this kind of drive) Therefore you wouldn't be able to use such a drive to build up a high velocity - unlike a merely reactionless drive, it would require greater energy input for a greater total "deviation" from normal conditions. This one you could, perhaps, theoretically use to create infinite energy, but since such an effect even I have trouble wrapping my mind around the logistics of, I suspect that what its limits would be is completely unknown. If the conservation laws are indeed all-important in the universe, the effect would be limited in such a way as to prevent it ever threatening them. I don't know what that would take, though.

edit: Hm. Now that I think about it, perhaps the problem is that the latter device could still alter its velocity if it were moved by something else - the lack of preferential reference frames would create that exact kind of situation, with a direct change in velocity rather than constant thrust. The drive accelerating itself to 10 m/s relative to its "at rest" position could impart its momentum to a different object via collision (for instance), which would allow it to accelerate again... although wait, no, it would just mean that the object and the drive would eventually start moving in the same direction with the same speed, because the drive can't cease operating without the object imparting its momentum right back at the drive. Hm. Me is confuse. Gonna have to think about it some more later.

Edited August 15, 2015 by Sean Mirrsen

[SargeRho]

You cannot create an action without a reaction. Even a photon drive is a reactive engine, being accelerated by the fore produced by the production of photons.

[Rakaydos]

A gauss rail still has recoil.

If the EM drive is pushing off something exotic like the gauss rail would be, the equations would balance out.

[K^2]

The inventor, however, could be both right and wrong.

Accidentally stumbling on a device where thrust is produced, while having something totally illogical for an explanation is not being right by any measure. It's being lucky, at best.

Wouldn't the same thing happen with a photon drive?

Nah. Photon drive works just like a chemical rocket. With a chemical rocket, you have to have much higher thrust early on, because you have to push all these heavy fuel tanks. So you are burning extra fuel to accelerate fuel. Once you are going fast, you are using part of the kinetic energy of the fuel to help push your ship. So while you do get more power out of your engines than chemical energy of fuel ought to provide, that energy isn't free. You had to pay for it up front.

Photon drive is much the same, except relativity is involved. If you have some supply of energy E, then once you got up to speed v, your total energy supply is actually γE, where γ = 1/sqrt(1-v²/c²) is the Lorentz boost factor. This extra energy is what lets you run photon drive at higher power (from perspective of "stationary" observer). But again, it wasn't free. Energy, in quantities you need to operate a photon drive, is extra mass. And your photon drive had to work extra hard to get that m = E/c² up to speed.

There is some additional relativistic weirdness going on. If from ship's perspective, we maintain constant thrust, we maintain constant proper acceleration. Say, exactly 1g for convenience. (Yes, big photon drive.) From perspective of stationary observer, however, our acceleration is merely g/γ³. A stationary observer would conclude that this decrease in acceleration is due to two factors. Ship's mass has increased by a factor γ, because relativistic mass works that way, but also ship's drive appears to operate at lower thrust due to red shift and/or time dilation, depending on your perspective.

It's important to note that while yeah, relativity does, in fact allow for thrust to decrease at extreme relativistic speeds, simply adding a constraint that energy is neither created nor destroyed, allows us to derive energy usage of such a drive. And it's still 300MW/N. In other words, the only thing that can operate that way is some variation on photon drive.

[PB666]

If it's interacting with something, I have no problems with it. I still insist that it's rather unlikely that it's interacting with something we haven't discovered yet, so we should be looking for conventional exhaust. But interaction with absolutely anything massive is fine in principle.

Experiment #1. In a pure vacuum the exhaust vectors must be (in excess) in a hemisphere

premise 1 - whose radius is determine by hv of the resonator and the upper limit of which is determine by the inverse of the atomic weight of the potentially ejected ions. *

premise 2 - either ejected as ions (plasma) which emit light and can be detected in a dark chamber

premise 3 - or carry a charge that can be detected as voltage blips on a strike plate.

Therefore placing a scintillation detector or a charged particle detector behind the device and comparatively graphing the force of acceleration against voltage spikes or EM pulses would be able to elucidate the 'ablation'

*having worked on coating materials using charged ions for the purpose of electron microscopy I can suggest this is not simple, the problem is that almost everything gets coated with a patina of particles that when properly influenced come off and can go anywhere. The may be sufficient amount of gunk on the metal device to explain acceleration, so will have to set the bound.

In response to the rest of your article. If this is working as the authors state, then momentum is being transferred 'free' to objects in local or universal space. I do not believe (absolutely certain) that their device is so efficient that it could be a perpetual motion machine, after all they are input enough power to blow up caps and only getting 10^-6 the argument is starting to sound like a red herring. There are many authors now and what they say is happening is irrelevant since they have not done any experiments to rule out all possibilities. All they are saying is that force is generated and it is not an artifact of the electronics that generate resonance.

Assuming that Experiment #1 is done properly and the ablation problem is excluded.

The local space issue can be tested by a carefully designed vacuum with a hemispheric strike plate placed around the 'accelerator', with force sensors connected to the chamber itself.

The universal space issue can be tested by testing the device in space, without local space interactions, the devices output should not saturate. If is does not, then with proper design you could create something approximating perpetual motion (although heat production will still probably disallow it).

- - - Updated - - -

Is it, again, not true for everything? Relativity works both ways. Drop the EMDrive, and use the other way we have of converting electricity to kinetic energy directly - a Gauss rail. Set the Gauss rail to deliver 500 joules of energy to its payload - you'll have the same paradox in regards to how much acceleration it should result in. A reactionless drive, even if reaction-less, still provides the action. It produces a force with no counterforce, but in the context of differing frames of reference, all it does is convert one type of energy to another.

Good analogy, but the problem is that the magnetic field lines already exist in space _before_ realization of force and we know this is just another face of electromagnetism. So basically the EM is already present and you are simply engaging it momentarily to transfer momentum. We have to assume that the researchers have already ruled out that this is happening (although by the comments of K2 this is not clear).

- - - Updated - - -

It's important to note that while yeah, relativity does, in fact allow for thrust to decrease at extreme relativistic speeds, simply adding a constraint that energy is neither created nor destroyed, allows us to derive energy usage of such a drive. And it's still 300MW/N. In other words, the only thing that can operate that way is some variation on photon drive.

Except that Cannae is operating a magnitude more efficiently than a photon drive.

E² = p²c² + m²c² Since a photon has no mass and no (m²c²), then either they have a means of converting photons of one energy to 10 times as many at a lower energy without loosing momentum which is impossible (p = h_redk = ^h/_^l which means you cannot convert photons to something 10 less energy without affecting momentum), or there is a compliment of reaction mass also being accelerated somewhere.

.

[Rakaydos]

Accidentally stumbling on a device where thrust is produced, while having something totally illogical for an explanation is not being right by any measure. It's being lucky, at best.

Nah. Photon drive works just like a chemical rocket. With a chemical rocket, you have to have much higher thrust early on, because you have to push all these heavy fuel tanks. So you are burning extra fuel to accelerate fuel. Once you are going fast, you are using part of the kinetic energy of the fuel to help push your ship. So while you do get more power out of your engines than chemical energy of fuel ought to provide, that energy isn't free. You had to pay for it up front.

Photon drive is much the same, except relativity is involved. If you have some supply of energy E, then once you got up to speed v, your total energy supply is actually γE, where γ = 1/sqrt(1-v²/c²) is the Lorentz boost factor. This extra energy is what lets you run photon drive at higher power (from perspective of "stationary" observer). But again, it wasn't free. Energy, in quantities you need to operate a photon drive, is extra mass. And your photon drive had to work extra hard to get that m = E/c² up to speed.

There is some additional relativistic weirdness going on. If from ship's perspective, we maintain constant thrust, we maintain constant proper acceleration. Say, exactly 1g for convenience. (Yes, big photon drive.) From perspective of stationary observer, however, our acceleration is merely g/γ³. A stationary observer would conclude that this decrease in acceleration is due to two factors. Ship's mass has increased by a factor γ, because relativistic mass works that way, but also ship's drive appears to operate at lower thrust due to red shift and/or time dilation, depending on your perspective.

It's important to note that while yeah, relativity does, in fact allow for thrust to decrease at extreme relativistic speeds, simply adding a constraint that energy is neither created nor destroyed, allows us to derive energy usage of such a drive. And it's still 300MW/N. In other words, the only thing that can operate that way is some variation on photon drive.

So just hypthetically... if there existed a drive that interacted with a medium that we have not otherwise detected, (lets be classical and call it the luminus aether) and any momentum transferred to the aether is "Somebdy elses's problem", would we expect different thrusts in different directions? (a simulated "preferred frame of reference", where the so called "frame of refrence" is the current local aether currents, not a true global preference)

[K^2]

Except that Cannae is operating a magnitude more efficiently than a photon drive.

Which proves that there is a reaction mass involved. It's the only way to prevent situation where arbitrary amount of energy can, at least in theory, be created.

So just hypthetically... if there existed a drive that interacted with a medium that we have not otherwise detected, (lets be classical and call it the luminus aether) and any momentum transferred to the aether is "Somebdy elses's problem", would we expect different thrusts in different directions? (a simulated "preferred frame of reference", where the so called "frame of refrence" is the current local aether currents, not a true global preference)

Yes. An electric motor with a propeller is a perfectly good propellant-less drive if you are flying in an atmosphere. But it's only efficient up to certain speeds. Then you start having to waste a lot of extra energy.

If there is an aether used by EMDrive as a reaction mass, I would expect a very similar behavior. There are, however, some caveats here that make it unlikely. First, aether cannot have sufficient EM cross section for EMDrive to grab onto it directly. Such aether would be very obvious in other experiments. We would have found it two hundred years ago, at least. Especially, since people have been actively looking. This still leaves an outside margin of probability that EMDrive does have some sort of a Q Thruster type of interaction with some exotic virtual particle, which in turn passes momentum to aether. This still raises a lot of questions, however. First, why haven't we seen this in particle accelerators, where we use far more powerful resonant chambers to accelerate particles? This ought to have been detected. Second, if this aether is weakly interacting, it can't possibly be "sticking" to Earth's surface. So we ought to be able to detect thrust variations depending on a) Orientation of the EMDrive, Orientation of Earth (time of day), and potentially c) Time of year.

I haven't seen anything in orientation of EMDrive tests that screams aether, but they are noisy. It'd be nice to set up a series of tests specifically to exclude this possibility. It's still a very unlikely one, but not on the same margin of impossible as some other suggestions.

P.S. Existence of weakly interacting massive aether would help explain some things, though. I just find it very unlikely that EMDrive can interact with such a thing.

[Aethon]

I have been attempting to follow the NASA Space flight EMDrive forum developments, which is difficult since it is now four consecutive threads over 900 pages long (I wish these smart people could learn to snip their quotes), and some of the Maths is over my head. There seems to be a number of DIY builders constructing various devices, altering parameters, and taking data under the guidance of some serious scientists.

Here is a folder which holds all the known, public Eagleworks EMDrive Force measurement runs.

https://drive.google.com/folderview?id=0B7kgKijo-p0ifnFrZ2V1UmZEY25FXzNrX0hjNXJmQXR5YzRnaVBqcTdMZUhxcjVkMUUtaXc&usp=sharing

One forum user rfmwguy plans to live test and record his new device on Tuesday August 25th. I'll try to post a link if I catch it.

[Three1415]

P.S. Existence of weakly interacting massive aether would help explain some things, though. I just find it very unlikely that EMDrive can interact with such a thing.

We already know such an "aether" exists, do we not? After all, the dispersion of hydrogen atoms/molecules throughout interstellar space could already be considered a sort of aether, so it seems logical that dark matter would exhibit similar properties, especially given its characteristics. The interstellar medium is so largely devoid of baryonic matter because of the latter's tendency to clump up into discrete, collectively massive objects, and thus most of what would otherwise constitute a diffuse but far thicker medium is bound up into clumps of many orders of magnitude higher density.

However, at least as far as I know, we have yet to detect similar clumps of dark matter on scales below several kiloparsecs (i.e, objects such as "dark stars" or "dark planets"); if such objects were to exist, I would expect them to largely dominate gravitational interactions between baryonic structures on a much smaller scale due to the fact that their combined mass-energy exceeds that of the former by more than a factor of six. This we would undoubtedly have noticed much earlier and in a far less esoteric fashion than via the measurement of orbital velocities of billions of stars in large galaxies, or via distortion amplitude measurements performed on Einstein rings.

So it seems to me that the only logical conclusion is that, for whatever reason (and I certainly cannot posit a mechanism for the difference in behavior between the two with any real belief in its accuracy) and unlike baryonic matter, dark matter is instead distributed, at least on the scale of stars and star clusters, in an extremely homogeneous, diffuse medium--the only real way we could not immediately discern its presence, and the precise definition of a "weakly interacting aether." And this should hold true regardless of the identity of dark matter, be it vast quantities of neutrinos or fewer and more exotic WIMPs.

Thus, such a suggestion appears entirely reasonable (albeit in my mostly uninformed opinion), at least in comparison to such effective impossibilities as the violation of conservation laws; the only real issue is, as K^2 pointed out, that what is effectively a microwave in a box should be the last thing in which we would expect to observe such an effect--this is my main source of doubt as to the reality of the EmDrive's applicability. Had it been some beautifully engineered, complex hardware built on mostly sound principles and with the anticipation of causing this effect, I would be far less skeptical; but as of now it begs the question why no-one has ever observed this effect before, especially if it is reproducible with such a simple apparatus.

Edited August 17, 2015 by Three1415

[K^2]

We already know such an "aether" exists, do we not?

Not really. There are competing theories to explain dark matter. The two main categories are Weakly Interacting Massive Particles (WIMPs) and Massive Compact Halo Objects (MACHOs). (Yes, physicists are very silly people.) Only the WIMP hypothesis is consistent with a massive aether. And even then, there is no guarantee that it's evenly distributed. Fact that we've found no evidence of it in the Solar System suggests that it's probably not. In which case, it can't be responsible for propulsion. I suppose, there is possibility that density of it around here just happens to be much, much lower than in the rest of the galaxy. But would it then still be possible to get any measurable thrust out of it?

The situation dark energy is even murkier. (Har! *cough* Sorry.) Suffice it to say, there is no reason to believe that it actually has rest mass. So even if we could somehow use it for propulsion, it's unlikely to actually have higher efficiency than a photon drive.

Long story short, this is all very far from, "already know." It's one of the possibilities. It's on the table for hypothetical high efficiency propellant-less (but not reaction-less) space propulsion. EMDrive turning out to be such a device would make it the unlikeliest discovery yet. But I can't call it impossible.

What I can say is that there are still a long list of far more likely explanations we're yet to cross out. And it will be far more time-efficient to test these first. Given the unexpected outcome of some previous tests, I think it's time to bite the bullet and do an honest ion trail search. If we can reliably exclude ion propulsion, EMDrive would rightfully step up from "curious" to "interesting".

[SAI Peregrinus]

Just to be clear, the observed distributions of Dark Mater are nonhomogeneous (it causes significant gravitational lensing, which wouldn't happen at all if it were homogeneous) which makes it inconsistent with the idea of a massive aether. And we already know that it can't interact significantly with microwaves, since if it did so it would be far more visible than just seeing its gravitational effects.

[Ralathon]

Is it, again, not true for everything? Relativity works both ways. Drop the EMDrive, and use the other way we have of converting electricity to kinetic energy directly - a Gauss rail. Set the Gauss rail to deliver 500 joules of energy to its payload - you'll have the same paradox in regards to how much acceleration it should result in. A reactionless drive, even if reaction-less, still provides the action. It produces a force with no counterforce, but in the context of differing frames of reference, all it does is convert one type of energy to another.

No, it wouldn't create a paradox if you take the reaction mass into account.

Say our gauss rail has a mass of 1kg and a reaction mass of 1kg. You feed it 100 joulles, which is split evenly between the reaction mass and the railgun. So they both move in opposite directions with 10m/s relative to the ground. The initial energy is 0J, the final energy is 2*(0.5*10^2) = 100J, exactly as expected.

Now lets do the same thing on a train that moves 1km/s. We know the initial energy of the system is 0.5*2*1e3^2 = 1MJ. We know that we feed the system 100J, so the final energy needs to be 1.0001MJ.

So we need to solve 0.5*v_reaction^2 + 0.5*v_gauss^2 = 1.0001MJ. We also know that the velocity difference is symmetrical. v_init-v_reaction = v_gauss-v_init = ÃŽâ€v.

0.5*(v_init-ÃŽâ€v)^2 + 0.5*(v_init+ÃŽâ€v)^2 = 1.0001MJ

(v_init-ÃŽâ€v)^2 + (v_init+ÃŽâ€v)^2 = 2*1.0001MJ

(v_init^2-2*v_init*ÃŽâ€v+ÃŽâ€v^2) + (v_init^2+2*v_init*ÃŽâ€v+ÃŽâ€v^2) = 2*1.0001MJ

2*v_init^2+2*ÃŽâ€v^2 = 2*1.0001MJ

v_init^2+ÃŽâ€v^2 = 1.0001MJ

v_init = 1000m/s

1MJ + +ÃŽâ€v^2 = 1.0001MJ

ÃŽâ€v^2 = 100J

ÃŽâ€v = 10m/s

So the final velocity of the gauss rifle will be 1010m/s and the final velocity of the reaction mass will be 990m/s. No paradox anywhere, both the guy on the station and the guy on the train see the gauss rifle move 10m/s faster than before. The total energy gained by the gauss rifle is much higher than 100J for the guy on the station, but it is compensated by the decrease in energy of the reaction mass.

Edited August 17, 2015 by Ralathon

[PB666]

Not really. There are competing theories to explain dark matter. The two main categories are Weakly Interacting Massive Particles (WIMPs) and Massive Compact Halo Objects (MACHOs). (Yes, physicists are very silly people.) Only the WIMP hypothesis is consistent with a massive aether. And even then, there is no guarantee that it's evenly distributed. Fact that we've found no evidence of it in the Solar System suggests that it's probably not. In which case, it can't be responsible for propulsion. I suppose, there is possibility that density of it around here just happens to be much, much lower than in the rest of the galaxy. But would it then still be possible to get any measurable thrust out of it?

But you open another bag of worms... if DM explains the orbits in this galaxy then its either really big rare stuff, or semiubiquitous. Niether of which are WIMPs. Alternatively its a feild and not a particle for most interactions in which case the standard model is incomplete.

The situation dark energy is even murkier. (Har! *cough* Sorry.) Suffice it to say, there is no reason to believe that it actually has rest mass. So even if we could somehow use it for propulsion, it's unlikely to actually have higher efficiency than a photon drive.

Long story short, this is all very far from, "already know." It's one of the possibilities. It's on the table for hypothetical high efficiency propellant-less (but not reaction-less) space propulsion. EMDrive turning out to be such a device would make it the unlikeliest discovery yet. But I can't call it impossible.

What I can say is that there are still a long list of far more likely explanations we're yet to cross out. And it will be far more time-efficient to test these first. Given the unexpected outcome of some previous tests, I think it's time to bite the bullet and do an honest ion trail search. If we can reliably exclude ion propulsion, EMDrive would rightfully step up from "curious" to "interesting".

but if there are missing fields in the standard model, and I think that its 50:50 then certainly one of these interactions could explain the effect. Its just so much easier to get NASA to build a space worthy drive and throw it up on USAFs Gps launch mission. It ether produces thrust in space that does not saturate due to depletion or local saturation, and you can sleep well at night knowing physics is not broken, otherwise you have a whole new NSF worthy physics to explore.

Edited August 19, 2015 by PB666

[SAI Peregrinus]

Alternatively its a feild and not a particle for most interactions in which case the standard model is incomplete.

As far as we know, all (quantized) fields have corresponding particles, and all particles have corresponding fields. So if there's a dark matter field then at some energy there's a dark matter particle. It's not an either-or proposition, particles are just properties of particular wavefunctions on fields.

As for testing it in space, why? It's cheaper to test things on the ground, and you can get MUCH more detailed data by testing in a lab than by slapping one on a satellite. Once we've exhausted the abilities of lab testing, THEN it's time to test in space (if an effect is still present and unexplained). Not before.

[K^2]

As far as we know, all (quantized) fields have corresponding particles, and all particles have corresponding fields. So if there's a dark matter field then at some energy there's a dark matter particle. It's not an either-or proposition, particles are just properties of particular wavefunctions on fields.

Correct.

And yes, DM being a new type of field/particle would make SM incomplete. Which is by no means impossible, nor would it really flip our understanding of physics upside down. SM is kind of built in a way that makes it relatively easy to add new fields to it without breaking everything else. The real problem is that we haven't detected that field yet. Which would suggest very weak interactions with known fields. And that makes it extremely unlikely that EMDrive can interact with it.

[SAI Peregrinus]

Indeed. We even have good reason to suspect that the Standard Model is incomplete: it can't yet account for gravity. But there's a lot of evidence for gravity, and some promising extensions to SM to let it do so. Dark matter shouldn't be much of a problem. Dark energy is more of an issue, and probably won't be solved until gravity is accounted for.

There's a lot of evidence that Dark Matter doesn't interact electromagnetically. The EMDrive is an electromagnetic system, it generates microwaves (EM radiation) in a cavity. Therefore it is highly unlikely it can be interacting with dark matter; there's simply too much evidence that microwaves and dark matter don't interact for the inconclusive results seen so far to overthrow that.

[Aethon]

Here's a better doc than the one I linked above, which includes the paper detailing the vacuum chamber EM Drive test.

Anomalous Thrust Production from an RF Test Device Measured on a Low-Thrust Torsion Pendulum

David A. Brady*, Harold G. White†NASA Lyndon B. Johnson Space Center, Houston, Texas 77058, Paul March‡, James T. Lawrence§, and Frank J. Davies**

https://drive.google.com/folderview?id=0B7kgKijo-p0ifnFrZ2V1UmZEY25FXzNrX0hjNXJmQXR5YzRnaVBqcTdMZUhxcjVkMUUtaXc&usp=sharing

[Aethon]

Using water waves in a resonant chamber to simulate the EM Drive.

Would be nice if he flipped it and ran it the other way. Oh well. I assume you have a bathtub.

Edited August 19, 2015 by Aethon

[PB666]

Indeed. We even have good reason to suspect that the Standard Model is incomplete: it can't yet account for gravity. But there's a lot of evidence for gravity, and some promising extensions to SM to let it do so. Dark matter shouldn't be much of a problem. Dark energy is more of an issue, and probably won't be solved until gravity is accounted for.

There's a lot of evidence that Dark Matter doesn't interact electromagnetically. The EMDrive is an electromagnetic system, it generates microwaves (EM radiation) in a cavity. Therefore it is highly unlikely it can be interacting with dark matter; there's simply too much evidence that microwaves and dark matter don't interact for the inconclusive results seen so far to overthrow that.

Whatever the EM drive is interacting with, its only slightly better than EM momentum by itself, it could be a very weak interaction, although I agree, not likely to interact with DM electromagnetically. We assume that the resonance is what is creating the force, the resonance may be interacting with the walls of the chamber and creating another non-electromagnetic field.

- - - Updated - - -

As far as we know, all (quantized) fields have corresponding particles, and all particles have corresponding fields. So if there's a dark matter field then at some energy there's a dark matter particle. It's not an either-or proposition, particles are just properties of particular wavefunctions on fields.

As for testing it in space, why? It's cheaper to test things on the ground, and you can get MUCH more detailed data by testing in a lab than by slapping one on a satellite. Once we've exhausted the abilities of lab testing, THEN it's time to test in space (if an effect is still present and unexplained). Not before.

I thought I was clear, for most interaction it behaves like a field and not as a particle. Testing it on the ground has one major problem, the ground is very massive, and this is exactly what the test needs to avoid, mass of any kind behind the device which can be pushed off of.

[KSK]

Indeed. We even have good reason to suspect that the Standard Model is incomplete: it can't yet account for gravity. But there's a lot of evidence for gravity, and some promising extensions to SM to let it do so. Dark matter shouldn't be much of a problem. Dark energy is more of an issue, and probably won't be solved until gravity is accounted for.

There's a lot of evidence that Dark Matter doesn't interact electromagnetically. The EMDrive is an electromagnetic system, it generates microwaves (EM radiation) in a cavity. Therefore it is highly unlikely it can be interacting with dark matter; there's simply too much evidence that microwaves and dark matter don't interact for the inconclusive results seen so far to overthrow that.

Without wishing to be snarky, I thought that dark matter doesn't interact electromagnetically by definition - otherwise it wouldn't be dark?

[K^2]

Using water waves in a resonant chamber to simulate the EM Drive.

This thing seems to move due to "leakage". I'm talking about the waves that escape "resonator". If EMDrive simply got propulsion from RF leaks, it'd have power/thrust efficiency of a photon drive. We wouldn't be having a discussion then. Instead, it has a measured efficiency an order of magnitude better. Which requires reaction mass. Without reaction mass, demonstrated efficiency violates conservation laws.

[SAI Peregrinus]

Without wishing to be snarky, I thought that dark matter doesn't interact electromagnetically by definition - otherwise it wouldn't be dark?

Sort of. It's still possible for it to interact very, very weakly (tiny coupling constant) or to have an indirect (exotic) decay path to something that does interact electromagnetically. And if it does interact via the weak force (there's a tiny bit of evidence for this, thus the popularity of Weakly Interacting Massive Particles) then at high enough energies (above the electroweak unification) it would interact electromagnetically since the weak and electromagnetic forces merge. Unfortunately the only places you get those energies are very shortly after the hot big bang or inside the event horizons of black holes, so studying them is difficult (to massively understate the issue).