EmDrive

[Z-Man]

From the perspective of an observer gently floating down with 10 cm/s, 3.3 kW. And you're allowed to switch to that observer's view if the device is supposed to also produce the same thrust in a vacuum. You would not be allowed to if the device in question was, say, a solid floor.

(The force to hold up 3.3 metric tons is 33kN, by the way.)

[Heimdall5008]

The force is defined by Newtons law as:

F = m*a

In this case a is the gravitational acceleration, noted as g.

F=m*g

For middle europe g is normally g = 9.81 m/s².

The energy is given as the potential energy as E_pot = m*g*h, where h is the height above the ground (a.k.a. the local minimum of the potential energy).

[gamowin]

http://xkcd.com/1404/

My favorite web comic series.

[magnemoe]

http://imgs.xkcd.com/comics/quantum_vacuum_virtual_plasma.png

http://xkcd.com/1404/

My favorite web comic series.

Let us set up an scientist test with cuffs and crocodile clamps (poor girl:))

However an copper block should not twitch, it would radiate radio waves if configured or just heat up, exception is magnet fields who I assume they was aware off.

[RuBisCO]

The force is defined by Newtons law as:

F = m*a

In this case a is the gravitational acceleration, noted as g.

F=m*g

For middle europe g is normally g = 9.81 m/s².

The energy is given as the potential energy as E_pot = m*g*h, where h is the height above the ground (a.k.a. the local minimum of the potential energy).

So then the theoretical minimum amount of energy needed to hold up something, as in no change in height, is zero

[ZetaX]

You achieve this theoretical minimum every time you stand on the ground.

[RuBisCO]

You achieve this theoretical minimum every time you stand on the ground.

The body does need to waste energy because skeletal muscles must spend energy to remain contracted. Likewise just to keep a flying car hovering must consume energy somehow.

[CptRichardson]

I don`t have the background to be able to say for sure if that is the case here. My prejudice wants to say all Chinese science results are fake, hehe.

NASA notes that the chinese results are much higher because the chinese input power was much higher. Kilowatts instead of watts like NASA was using.

[KerikBalm]

The body does need to waste energy because skeletal muscles must spend energy to remain contracted. Likewise just to keep a flying car hovering must consume energy somehow.

The body doesnt need to... a dead man lying in the ground expends no energy, yet doesn't sink to the Earth's core.. wonder why?

A harrier produces force by moving air, a relatively small amount, really fast. The KE imparted to the air is how much energy it needs to keep hovering.

Because KE= 1/2 mv^2, a helicopter which moves a larger volume of air at a slower speed, expends less energy to hover.

In the case of a person doing squats, there is considerable movement at the molecular level, manifesting as heat production.

Basically, the less you need to move things to generate the force, the less energy you need to expend.

A rock lying on the floor doesn't need to move anything to generate the force to counter gravity, and thus needs no energy expenditure.

[RuBisCO]

The body doesnt need to... a dead man lying in the ground expends no energy, yet doesn't sink to the Earth's core.. wonder why?

Woooo semantics: Dead men don't "stand".

A rock lying on the floor doesn't need to move anything to generate the force to counter gravity, and thus needs no energy expenditure.

I'm pretty sure I pointed that out to begin with: "So then the theoretical minimum amount of energy needed to hold up something, as in no change in height, is zero"

Anyways back to the subject, 'Red Iron Crown' claimed that 3.3 kN (?) from 1 kW is beyond 100% efficiency, all I'm asking is how he figures that? Is it a newton to watt direct conversion? That is kind of flawed reasoning. Just as a rock expends no energy to "push" against the ground and not fall to the center of the earth, it is not expending a watt for every tenth of a kilo it weighs.

Edited August 15, 2014 by RuBisCO

[stefanbanev]

The claim is 1KW to hover 3 tones. In space it means 1G acceleration for 3 tones by 1KW. Observers in cabine with working emDrive in both cases (Earth/Space) experience 1G and should not distinguish where this 1G came from according to the "principle equivalency". However, claim states that acceleration increases the kinetic energy so thrust is going down thus, the observer in the cabin on the Earth continue experience 1G while, observer in the space-cabine does not experience 1G thus the author of emDrive discovered a way to violate the "principle equivalency". How emDrive may "know" when it should produce the thrust 1G and when it should not; it must feel the gravitational gradient ;o) so when emDrive in free fall and it is powered on it stops the fall and hovered, but when emDrive is in free fall in space it realises that it is wrong place to produce thrust thus, to keep its credibility it does not produce thrust, somehow it feels the presence of gravity...

[Z-Man]

Let me rephrase my earlier statement. Standing still without using power or using arbitrarily low power is only possible if you allow direct or indirect interaction with the ground. The rock and dead man directly interact with it. The helicopter indirectly interacts with it because the air it pushes against is held up by the ground. A sci-fi hovering device using polarity reversed tractor beams to keep its distance can also use as little power as circumstances allow.

The EMDrive claims to be no such device. It claims to work in a vacuum. So if it can produce 33 kN from 1 kW while hovering, it also needs to be able to produce that in any other reasonable situation. Easy small modification: It also needs to produce the same thrust while ascending with 10 cm/s. In which case, it will increase the potential energy of whatever it is pushing up by 3.3 kJ each second (use Heimdall's formulae, I'm personally using g = 10m/s² for convenience), so output power would be 3.3 kW. More than the input power.

The same argument can be made, using higher ascend speeds, for any direct reactionless power-to-thrust engines as long as they are more efficient than a photon drive. If the device is as efficient or less than a photon drive, the speed required to break energy conservation becomes c or larger, and the argument breaks down.

[magnemoe]

Let me rephrase my earlier statement. Standing still without using power or using arbitrarily low power is only possible if you allow direct or indirect interaction with the ground. The rock and dead man directly interact with it. The helicopter indirectly interacts with it because the air it pushes against is held up by the ground. A sci-fi hovering device using polarity reversed tractor beams to keep its distance can also use as little power as circumstances allow.

The EMDrive claims to be no such device. It claims to work in a vacuum. So if it can produce 33 kN from 1 kW while hovering, it also needs to be able to produce that in any other reasonable situation. Easy small modification: It also needs to produce the same thrust while ascending with 10 cm/s. In which case, it will increase the potential energy of whatever it is pushing up by 3.3 kJ each second (use Heimdall's formulae, I'm personally using g = 10m/s² for convenience), so output power would be 3.3 kW. More than the input power.

The same argument can be made, using higher ascend speeds, for any direct reactionless power-to-thrust engines as long as they are more efficient than a photon drive. If the device is as efficient or less than a photon drive, the speed required to break energy conservation becomes c or larger, and the argument breaks down.

Hovering equals an 1 g acceleration, if will require 3.3 kW minimum, if you use 1 kw you might use this to produce energy: two weights with this drive mounted like elevator counter weights but with an generator instead of an motor on top, switch who weight will get power.

Now 1 newton for 1 kw is huge, it will transform space operations radically, 100 newton and you pretty much have a touch ship.

[Red Iron Crown]

Anyways back to the subject, 'Red Iron Crown' claimed that 3.3 kN (?) from 1 kW is beyond 100% efficiency, all I'm asking is how he figures that? Is it a newton to watt direct conversion? That is kind of flawed reasoning. Just as a rock expends no energy to "push" against the ground and not fall to the center of the earth, it is not expending a watt for every tenth of a kilo it weighs.

There is no direct conversion, but a little common sense can show some difficulties with the figures. Imagine the thruster is on a vessel travelling 1m/s, and in one second doesn't accelerate the ship significantly (it would take more time to build significant speed in this case). Calculate the power produced:

P = F * d / t

= 3300 * 1 / 1

= 3300W

From 1kW of supplied power, 3.3kW of propulsive power is generated. It gets worse the faster the ship is moving.

I don't think Oberth applies as the Emdrive is purportedly not a reaction drive. But maybe there's some other math going on there that makes it work, which is why I said "implied" rather than something more solid.

[DerpenWolf]

So as the title suggests I'm wondering what is up with the EM drive. Have they confirmed it works? Are they testing it? What is up with it??? I have a basic idea on how it supposedly works but if you could explain it to me anyway or point me to some articles that do so I would be quite happy! Cheers!

[KerikBalm]

In the same vein as the arsenic life paper, NASA published a study with shoddy controls, and the media wet their pants over it. At least this time the actual paper itself doesn't make unfounded claims (those unfounded claims are only peripheral or alluded to in the paper, not explicitely stated).

The test was not performed in a vacuum, thuse heating of air is a potential source of the thrust.

The test was performed on a device expected to be non-functional (ie, a negative control), but the same thrust was reported.

This means the study lacked proper controls, and any effect should therefore be really small if it is there at all.

Others may claim that the negative control was in fact still equally functional, and that the device still may work - but as I said, they lack controls.

So, the deal is that there is a lot of jumping to conclusions and media hype, and that this thing still probably doesn't work.

[lajoswinkler]

Stop spamming, people.

http://forum.kerbalspaceprogram.com/threads/79291-EmDrive

[KerikBalm]

"I don't think Oberth applies as the Emdrive is purportedly not a reaction drive."

Well, supposedly it is, its just the reaction mass are these ephemeral virtual particles.

Note that while hovering, or laying on the ground, there is no net acceleration- there are opposing forces yes, but no (net) acceleration (on the craft, in the hovering jet example, there's a whole lot of acceleration of air happening). The potenetial/kinetic energy of the craft does not change (except for lost fuel in the case of the hovering jet)

If this EM drive works, there will be acceleration, the craft will gain kinetic energy. If it gains kinetic energy greater than the input energy, we've violated conservation of energy, as well as conservation of momention - although I think it was already stated on this thread that you can't really violate one without violating the other.

This whole thing sounds ridiculous. If it really works (there is absolutely no good evidence that it does), I'll just throw up my hands, say that they've found a bug in the simulation, and ask our Universe's programmers to make me rich with a harem of beautiful women, or download my consciousness to their reality.

[Mazon Del]

To be fair, considering the low level of understanding with this effect, it is possible that the failure of the negative control could mean that the effect is real, but our understanding of the proper way to bring it about is incorrect.

[Vanamonde]

Merged into the existing thread for this matter.

[Nuke]

if you can build a cubesat sized test rig (such as the one in the video), it would be fairly affordable to test it in space. not sure what nasa spent on its experiments but i doubt its cheap. you could even get over enthusiastic space geeks to pay for your launch costs.

[KerikBalm]

To be fair, considering the low level of understanding with this effect, it is possible that the failure of the negative control could mean that the effect is real, but our understanding of the proper way to bring it about is incorrect.

To be fair, there is equal evidence that it could be magical pixies.

To claim it as evidence of a working EM drive/quantum virtual particle/whatever thruster is extremely unscientific. The results do not support any conclusion.

There is no evidence to refute a null hypothesis of the thrust being produced by heating of air.

This test shows no evidence that the thing works. End of Story until they do a proper test. There is no need to go into space to do a proper test at this time

[M Drive]

There is no evidence to refute a null hypothesis of the thrust being produced by heating of air.

This test shows no evidence that the thing works. End of Story

Now who's being unscientific? The thrust measured is well beyond the resolution of the measurement device, meaning it's probably not a measurement error, as so many claim. The thrust is most probably real, and proper tests have been executed. These are the proper tests.

Claiming it's "thrust produced by heating air" should be backed by theoretical evidence. Just saying "thrust generated by heating air" isn't an actual theory. How do you claim that'd work? Like those Swedish christmas ornaments? Because just "heating air" doesn't produce thrust if you thought so.

Your argument is hollow, is my point. There's solid evidence of thrust, and yes, a betting man wouldn't bet on conservation of momentum being broken. But even if that were 99.9999% probable, the fact remains that top scientists are having a hard time understanding where the thrust is coming from.

And that's the end of the story.

[CptRichardson]

I'd like to add something to that:

They did bring the test rig down as close to vacuum as they could manage on several tests, and continued to get consistent data. So, no, it's not atmospheric heating. It's another phenominon. One that I'd be baffled over too, but it's clear that it exists. Now, whether this is something similar to the time that Mythbusters managed to make a wagon roll by blowing a fan into a sail on it remains to be seen. It could well be an exotic photon drive or something of that nature, using light as a reactant. (which would be neat). If that's the case, which would work nicely, then there isn't any laws of motion being violated.

- - - Updated - - -

I'd like to add something to that:

They did bring the test rig down as close to vacuum as they could manage on several tests, and continued to get consistent data. So, no, it's not atmospheric heating. It's another phenominon. One that I'd be baffled over too, but it's clear that it exists. Now, whether this is something similar to the time that Mythbusters managed to make a wagon roll by blowing a fan into a sail on it remains to be seen. It could well be an exotic photon drive or something of that nature, using light as a reactant. (which would be neat). If that's the case, which would work nicely, then there isn't any laws of motion being violated.

[KerikBalm]

Now who's being unscientific? The thrust measured is well beyond the resolution of the measurement device, meaning it's probably not a measurement error, as so many claim. The thrust is most probably real, and proper tests have been executed. These are the proper tests.

...

Your argument is hollow, is my point. There's solid evidence of thrust, and yes, a betting man wouldn't bet on conservation of momentum being broken.

Your logical fallacy is: Strawman argument.

I never claimed there was no thrust, I simply state there is no evidence for your explanation of the thrust.

Claiming it's "thrust produced by heating air" should be backed by theoretical evidence. Just saying "thrust generated by heating air" isn't an actual theory. How do you claim that'd work? Like those Swedish christmas ornaments? Because just "heating air" doesn't produce thrust if you thought so.

Your logical fallacy is: Strawman argument, Burden of Proof & false statements.

Strawman: I never claimed it is thrust being produced by heating of air - simply that it is a possible explanation, and that there is not more evidence for the other explanation than for this explanation.

Strawman: the christmas ornament thing. - ties into the false statement/generalization and burden of proof fallacy with the statement "heating air" doesn't produce thrust"

There are ample theoretical, practical, empirical, working demonstrations ofthrust being produced by asymetric heating of air. Project Pluto certainly doesn't prove an EM thruster works. This EM drive had an energy supply, air as a potential reaction mass, and a cavity where the air had access and where the heating from the energy input was focused. There is a solid theoretical basis for that functioning as a thruster, similar to as in many electric drives that use microwaves to heat the exhaust gas, for example.

yes, a betting man wouldn't bet on conservation of momentum being broken. But even if that were 99.9999% probable, the fact remains that top scientists are having a hard time understanding where the thrust is coming from.

Your logical fallacy: Appeal to authority, False/misleading statements

The end of the story (for now) is there are plausible explanations to explain the thrust that do not violate conservation of momentum, and no evidence for the explanation that does violate it.

They did bring the test rig down as close to vacuum as they could manage on several tests, and continued to get consistent data. So, no, it's not atmospheric heating.

Please supply the source. The only thing I've seen in the actual publication simply says ambient air pressure or something like that.

Otherwise, I suspect you are essentially fabricating data/making false statements.