Author Topic: Propellantless Field Propulsion and application  (Read 666159 times)

Offline 93143

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Re: Propellantless Field Propulsion and application
« Reply #1700 on: 11/12/2012 02:35 AM »
According to the discussion on talk-polywell, White's QVF theory says that Shawyer's drive should work.

March says that a possible reason their test article failed is that they couldn't eliminate a glow discharge with the vacuum pump they had, and their predicted thrust with the discharge limiting the voltage was below the sensitivity of the balance.

So we may be looking at something more closely related to M-E than was first thought...

Online KelvinZero

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Re: Propellantless Field Propulsion and application
« Reply #1701 on: 11/12/2012 04:45 AM »
According to the discussion on talk-polywell, White's QVF theory says that Shawyer's drive should work.

I certainly don't claim enough knowledge to discount that! Im really looking for someone who understands the paper well enough to explain how it would behave, if it behaves differently from the model I produced.

If it is simply 0.72 newtons from 2.5kw with no other proviso, we can use it to generate energy out of nothing. I don't consider conservation of energy to be sacrosanct if momentum is not. If momentum is maintained over an undefined volume that could also explain where the energy comes from anyway. Perhaps using the device would slow the expansion of the universe very slightly.

On the other hand, perhaps it somehow obeys the Ke=0.5mv^2 rule, ie it is propellentless in the sense that a propeller is propellentless. That is still far superior to the rocket equation. As far as I can see this would involve choosing a special frame to 'push against' and would have different performance in different directions since it is unlikely we are exactly stationary wrt to this frame, especially on earth.

Or there might be another behaviour that I haven't thought of. In any case we don't need to understand all the details of the device to understand someone's explanation of what it does and does not promise us.


Offline JohnFornaro

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Re: Propellantless Field Propulsion and application
« Reply #1702 on: 11/12/2012 02:48 PM »
You can't get more energy out of the deceleration than you applied during the acceleration.

Sure you can.  All you need to do is fly through an electromagnetic decelerator instead of using the thruster.

Is this not what the Prius does, when braking downhill?   And after your journey over hill and dale, don't you have to fill it up with gas again?  Because of entropy?

Partly because of entropy - that's why the gas engine isn't 100% efficient.  But even if it were, and if the electric motor operation and reclamative braking were 100% efficient, and the batteries didn't leak at all, and there were no frictional or air resistance or rolling resistance losses, you would still not end the journey with more stored energy than you had at the start.

This is because the energy required to produce a certain amount of thrust depends on the speed of the vehicle, so no matter how fast you go, it takes at least as much energy to get that fast as you can theoretically get by slowing back down.  Basic Newtonian mechanics.

Wait a sec.  Didn't I say that you can't get more energy out of deceleration than you put in during acceleration?  Can you explain what this exchange below means?

Quote from: Me
You can't get more energy out of the deceleration than you applied during the acceleration.

Quote from: You
Sure you can.

Quote from: 93143
The proposed thruster doesn't appear to have that limitation, which implies that its operating principle is something weird, that may lead to an entropy principle violation or even a conservation violation.
 

Why'd you say "Sure you can [get more energy out of deceleration than you put in during acceleration]"?

Quote from: JF
Isn't the efficiency term where entropy is factored in?

Quote from: 93143
It's where entropy is generated.  But the Second Law of Thermodynamics provides no reason why η needs to be below unity in principle, because the described system is not a heat engine.  And there is certainly no fundamental physical reason η needs to be low enough to prevent local over-unity operation of the described system given an arbitrarily high vehicle speed.

Thanks for trying, but if eta is over-unity in a locally operated system, it means that the system is using energy.  On these various thrustors, that energy comes from the wall socket, AIUI.  So, I'm not sure what point you would be making here.

Quote from: JF
Quote from: 93143
There are better ways; they involve rotation...
I don't get what point you are trying to make.

Quote from: 93143
Basically that the linear acceleration/deceleration system you and I described is monstrously impractical for energy generation, and a steady-state rotating system might be a better plan.

Well, fine, but eta is still and always less than unity. No free lunch and all that.

Quote from: JF
Somebody tell me that my summary of the EM Drive, and the ME drive is incorrect:  You put electricity into it, and then it moves forward.  ...  I also don't seem to grasp how kinetic energy is apparently not related to momentum.

Basically this:

Quote from: 93143
You can't turn electrical energy into kinetic energy without throwing something away...

You have to push on something, and it can't be yourself.  Newton's Third Law.  All of this discussion turns on that.

Cars push on the road.  Rockets push on their propellant.  M-E thrusters (if they work) push on the rest of the observable universe...

Which I summarized earlier:

Woodward and all claim that the ME device pushes against the frame of rest of the universe, and state that they have derived a mathematical model which correctly restates the idea of action at a distance to support their thesis.

Quote from: 93143
...but since their behaviour seems to be independent of velocity or at least orientation this has some interesting theoretical consequences.

Hence the thread... Go on...

Quote from: 93143
It isn't yet clear what this EM-Drive is supposed to push on.

Shawyer asserts that group velocity imparts directional pressure, and thus momentum, AIUI:

Shawyer maintains that there is a causal relationship between the group velocity of a wave thru matter, and the actual momentum of the matter, and that he can manipulate it so that there is a preferential direction of momentum.  It appears to violate the conservation of momentum...

Shawyer is relating group velocity to momentum.  Go figger.  I cain't.

Quote from: 93143
Also, both momentum and kinetic energy are frame-dependent, but to different powers, while other forms of energy are not frame-dependent.  This messes nave attempts at equivalence right the #### up.

Hence the thread... Go on...

Quote from: 93143
Energy being the capacity to do work, it might make more sense to consider kinetic energy not as inherent in the velocity of a moving object, but rather as inherent in the difference in velocities between two objects.  If everything is moving at the same velocity, there's no capacity to do work involved no matter what reference frame you pick.

An interesting sidetrack, to be sure. Not clear to me how it applies to this.

Both of these guys, Shawyer and Woodward, are saying that there is a direct causal relationship between electricity and forward momentum, and that they can control it.  Somewhat.

BTW, the new 2012 Chinese article uses the same illustration as is used in this 2008 article:

http://blog.wired.com/defense/2008/09/chinese-buildin.html
« Last Edit: 11/12/2012 02:52 PM by JohnFornaro »
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Offline JohnFornaro

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Re: Propellantless Field Propulsion and application
« Reply #1703 on: 11/12/2012 03:05 PM »
Posted on talk-polywell:

http://www.emdrive.com/yang-juan-paper-2012.pdf

This paper appears to be a translation of the one written in Chinese, and posted earlier.  I cannot be considered a peer reviewed paper.  The device that they use is protected by Chinese patents, and a device not available to western scientists:

Quote
This paper uses a nationally patented device - the rocket indifferent equilibrium thrust measurement device - to measure the propellantless microwave thruster net thrust. Thus further experimentally verifying the feasibility of the practical microwave propulsion device.
Sometimes I just flat out don't get it.

Offline 93143

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Re: Propellantless Field Propulsion and application
« Reply #1704 on: 11/12/2012 11:09 PM »
Wait a sec.  Didn't I say that you can't get more energy out of deceleration than you put in during acceleration?  Can you explain what this exchange below means?

Quote from: Me
You can't get more energy out of the deceleration than you applied during the acceleration.

Quote from: You
Sure you can.

Quote from: 93143
The proposed thruster doesn't appear to have that limitation, which implies that its operating principle is something weird, that may lead to an entropy principle violation or even a conservation violation.
 

Why'd you say "Sure you can [get more energy out of deceleration than you put in during acceleration]"?

Being able to get more energy out of deceleration than you put in during acceleration is entirely contingent on the acceleration (but not the deceleration) being done by a device such as is being discussed/postulated/assumed in this thread - a propellantless thruster with a velocity-independent thrust-to-power ratio.

Quote
Quote from: 93143
It's where entropy is generated.  But the Second Law of Thermodynamics provides no reason why η needs to be below unity in principle, because the described system is not a heat engine.  And there is certainly no fundamental physical reason η needs to be low enough to prevent local over-unity operation of the described system given an arbitrarily high vehicle speed.

Thanks for trying, but if eta is over-unity in a locally operated system, it means that the system is using energy.  On these various thrustors, that energy comes from the wall socket, AIUI.  So, I'm not sure what point you would be making here.

In this case η is only applied to the deceleration phase (and the recharge phase, in my example, but whatever).  It is less than (or in the ideal case equal to) 1.

Given the reported behaviour of the thruster, which already includes all associated inefficiencies because it's an experimental result, more energy will be collected by the decelerator than was expended during acceleration if the peak velocity reached by the vehicle exceeds a critical value, in this case 6944.44444444444/η m/s (I goofed up the math last time; the previous post has been edited).

The only assumption required here is that the performance of the thruster doesn't depend on how fast it's going.  This is unprecedented for a propellantless device, and the result is locally-apparent free energy.  You cannot invoke conservation of energy to eliminate this result as you seem to be trying to do, because the problem is already fully specified.

Quote
Quote from: JF
Quote from: 93143
There are better ways; they involve rotation...
I don't get what point you are trying to make.
Quote from: 93143
Basically that the linear acceleration/deceleration system you and I described is monstrously impractical for energy generation, and a steady-state rotating system might be a better plan.
Well, fine, but eta is still and always less than unity. No free lunch and all that.

Nope.  See above.

Assuming the thruster reacts against distant matter or something like that, conservation is still respected globally.  But up close, the device does appear to be a perpetual motion machine of the first kind.

Quote
Quote from: 93143
...but since their behaviour seems to be independent of velocity or at least orientation this has some interesting theoretical consequences.
Hence the thread... Go on...

Well, if I understand correctly (which I wouldn't bet on), the M-E thruster implies an entropy condition violation, making it a perpetual motion machine of the second kind.  Proponents assure me that this is not the case, so I would rather not make a big deal of this before reading all the relevant papers...

At the very least, velocity- and orientation-independent behaviour has some interesting implications regarding how the thruster always manages to interact with "far-off active mass" that is essentially stationary with respect to itself.

And, of course, there's the transactional advanced/retarded wave stuff that purportedly results in instantaneous interaction, which wouldn't be necessary if this were a local conservative field effect (and thus not orientation-independent).

Quote
Quote from: 93143
Energy being the capacity to do work, it might make more sense to consider kinetic energy not as inherent in the velocity of a moving object, but rather as inherent in the difference in velocities between two objects.  If everything is moving at the same velocity, there's no capacity to do work involved no matter what reference frame you pick.
An interesting sidetrack, to be sure. Not clear to me how it applies to this.

Kinetic energy (as defined for a single object at a single velocity) is frame-dependent, while electrical energy is not.  In order to allow conversion of the one into the other, without reacting against anything, either the amount of electrical energy being used or the efficiency of the thruster would have to be quadratically related to the observer's reference frame, which is silly.  No need to worry about conservation of momentum; conservation of energy alone is sufficient to show that such a reactionless drive is not physically consistent.

The reason conservation of both momentum and energy are respected by a reaction drive is that the kinetic energy inherent in the relative motion of the vehicle and its exhaust is not frame-dependent.

...

Also, I thought the idea might help in the understanding of how a propellantless thruster with constant thrust-to-power ratio inevitably leads to the theoretical possibility of local over-unity operation when combined with reclamative braking or something conceptually similar.

Reclamative braking works on the principle of kinetic energy inherent in a velocity difference; it only works if a velocity difference is present between system components, and the energy collected is the same in all reference frames.

A propellantless thruster with a constant thrust-to-power ratio, on the other hand, doesn't care (or even know) how fast it's going because its operating principle doesn't involve interaction with something in a fixed reference frame other than its own.  (Hence the "interesting theoretical consequences" of M-E.)

Given a system in which the thrust from such a propellantless thruster is exactly countered by drag from a reclamative braking system (at constant efficiency, for the sake of argument), the power input is constant but the power output is linear with the velocity of the thruster.  Therefore, regardless of the value of the thrust-to-power ratio, there will be some thruster velocity at which this system produces more power than it consumes.  In the case of M-E, this power is siphoned off from the rest of the observable universe.  With a genuinely reactionless thruster, the energy appears out of thin air.

The variable efficiency of a real system does not save you from this theoretical result, because the efficiency of the braking system is mathematically unrelated to the behaviour of the thruster, and even if it weren't, the 'lost' energy would still show up as heat.  P = Fv doesn't have a loss coefficient, and it doesn't care what kind of energy the power P ends up as.

http://www.emdrive.com/yang-juan-paper-2012.pdf
This paper appears to be a translation of the one written in Chinese, and posted earlier.  It cannot be considered a peer reviewed paper.

I never said it was.  But I wasn't the only person complaining of being unable to read Chinese...

Online QuantumG

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Re: Propellantless Field Propulsion and application
« Reply #1705 on: 11/12/2012 11:19 PM »
a device such as is being discussed/postulated/assumed in this thread - a propellantless thruster with a velocity-independent thrust-to-power ratio.

I like that wording.

Also, having read the translation of the paper, I'm not sure they are saying it is velocity-independent, but..

Kinetic energy (as defined for a single object at a single velocity) is frame-dependent, while electrical energy is not.  In order to allow conversion of the one into the other, without reacting against anything, either the amount of electrical energy being used or the efficiency of the thruster would have to be quadratically related to the observer's reference frame, which is silly.

Exactly. It's not Infinite Improbability Drive silly, but it's still pretty silly. What's not to like? :)
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Offline JohnFornaro

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Re: Propellantless Field Propulsion and application
« Reply #1706 on: 11/13/2012 12:37 AM »
Being able to get more energy out of deceleration than you put in during acceleration is entirely contingent on the acceleration (but not the deceleration) being done by a device such as is being discussed/postulated/assumed in this thread - a propellantless thruster with a velocity-independent thrust-to-power ratio.

Well yeah. 

But first, thanks for the response.

Well yeah.  But the accelerating device I described is not this device; "a propellantless thruster with a velocity-independent thrust-to-power ratio".  I wouldn't mind believing in the premise of the thread, for its obvious utility in the HSF field.

It is the theoretical existence of this "propellantless thruster with a velocity-independent thrust-to-power ratio", which is the problem at hand.

Quote from: 93143
The only assumption required here is that the performance of the thruster doesn't depend on how fast it's going.  This is unprecedented for a propellantless device, and the result is locally-apparent free energy.  You cannot invoke conservation of energy to eliminate this result as you seem to be trying to do, because the problem is already fully specified.

Here is where I got and continue to stay, lost.  Locally apparent free energy.  Nor do I accept, perhaps only intuitively, but still, nor do I accept that the problem is "fully specified".

Quote from: 93143
Kinetic energy (as defined for a single object at a single velocity) is frame-dependent, while electrical energy is not.

The first part I get.  I'm travelling in the same direction and the same velocity as the speeding bullet.  I reach out my hand, NEO style, and pick the bullet up, and send it elsewhere.  Me and the bullet are in the same frame.  If me and the bullet hit the brick wall, stationary in our frame of reference, we go splat.

Electrical energy is different, always speeding around at more or less the speed of light; a constant, no matter the frame of reference.  So I sorta get that part as well.  Still hazy on the link (or lack of link) between the "mechanical", "framed" kinetic energy of a massy "thing", and the "frame" of an electrical energy wave.

These experimenters claim that they can take that electricity out of its frame, and direct it to mass in another arbitrary frame of reference.

Executive summary:  I'm not following you.
Sometimes I just flat out don't get it.

Online QuantumG

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Re: Propellantless Field Propulsion and application
« Reply #1707 on: 11/13/2012 12:42 AM »
Well, if it works, there's two possibilities:

* You can make infinite energy with it, which is pretty silly; or
* The thrust/power ratio drops off as you go faster, which is pretty silly also.

So, if it works, things are going to be silly, it's just a question of which kind of silly.

 8)
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Offline 93143

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Re: Propellantless Field Propulsion and application
« Reply #1708 on: 11/13/2012 02:27 AM »
The first part I get.  I'm travelling in the same direction and the same velocity as the speeding bullet.  I reach out my hand, NEO style, and pick the bullet up, and send it elsewhere.  Me and the bullet are in the same frame.  If me and the bullet hit the brick wall, stationary in our frame of reference, we go splat.

Electrical energy is different, always speeding around at more or less the speed of light; a constant, no matter the frame of reference.  So I sorta get that part as well.  Still hazy on the link (or lack of link) between the "mechanical", "framed" kinetic energy of a massy "thing", and the "frame" of an electrical energy wave.

These experimenters claim that they can take that electricity out of its frame, and direct it to mass in another arbitrary frame of reference.

Executive summary:  I'm not following you.

For electrical energy, consider a battery charged up with 50 kJ of chemical energy (which is just another form of electromagnetic energy).  Accelerate that battery to 1000 m/s (fast, but nonrelativistic).  What is the stored chemical energy in that battery?

50 kJ.  It hasn't changed.

So if you use this battery to directly impart kinetic energy to a vehicle, the kinetic energy it imparts has to be the same in all reference frames, because the energy used to impart it is the same in all reference frames.

Except that it can't be, because kinetic energy, when defined as 0.5mv for a single chunk of matter of mass m at a single velocity v, is inherently not the same in all reference frames.

But if you use that chemical energy to push something else in one direction, causing the spacecraft to accelerate in the opposite direction, the sum of the kinetic energy changes in the vehicle and its reaction mass is the same in all reference frames.

This is why conservation of energy inherently requires reaction mass.  And that is why the M-E people are so keen on pointing out that their idea is not a "reactionless" thruster, but merely a "propellantless" thruster.
« Last Edit: 11/13/2012 06:19 AM by 93143 »

Offline A_M_Swallow

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Re: Propellantless Field Propulsion and application
« Reply #1709 on: 11/13/2012 03:25 AM »
Well, if it works, there's two possibilities:

* You can make infinite energy with it, which is pretty silly; or
* The thrust/power ratio drops off as you go faster, which is pretty silly also.

So, if it works, things are going to be silly, it's just a question of which kind of silly.

 8)


That is the same 'sillyness' that Relativity has.  Although there the mass increases with velocity when approaching the speed of light.

Online KelvinZero

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Re: Propellantless Field Propulsion and application
« Reply #1710 on: 11/13/2012 05:55 AM »
Well, if it works, there's two possibilities:

* You can make infinite energy with it, which is pretty silly; or
* The thrust/power ratio drops off as you go faster, which is pretty silly also.

So, if it works, things are going to be silly, it's just a question of which kind of silly.

 8)


That is the same 'sillyness' that Relativity has.  Although there the mass increases with velocity when approaching the speed of light.

It does sound a bit similar, but in this case we are talking about velocity relative to some specific frame. This is exactly the situation that you get from a propeller in air. A 'space propeller' pushing against stray atoms does not violate any laws and is potentially far more efficient than a rocket.

Relativity on the other hand is famous for removing the need for light to propagate in a specific frame such as the 'ether'.

By the way, talking about what is and isnt possible, Here is another 'possible' as far as I can tell. if there were such a thing as a tractor beam that could reach across interstellar distances we could swing though the stars like tarzan, always chosing a new star with the desired relative velocity to us. This also gives us energy for free, at least locally.

We can think up various 'propellentless-like' forms of propulsion that do not violate physics, we just don't have anyone to explain the specific one being claimed in this case. It would be the first thing I clarified if ever I were to propose a mechanism I thought could work.

Offline JohnFornaro

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Re: Propellantless Field Propulsion and application
« Reply #1711 on: 11/13/2012 02:13 PM »
The first part I get. ...

Electrical energy is different, always speeding around at more or less the speed of light; a constant, no matter the frame of reference. ...

These experimenters claim that they can take that electricity out of its frame, and direct it to mass in another arbitrary frame of reference.

So if you use this battery to directly impart kinetic energy to a vehicle, the kinetic energy it imparts has to be the same in all reference frames, because the energy used to impart it is the same in all reference frames.

Except that it can't be, because kinetic energy, when defined as 0.5mv for a single chunk of matter of mass m at a single velocity v, is inherently not the same in all reference frames.

This part I get, I think; once you accelerate in a preferred direction, things look different when viewed from different reference frames.  But the energy sum remains constant, what with the prop going out one end, and the battery getting weaker.  Eventually, the spacecraft stops accelerating when the battery dies.

So far so good; I've known this part since before I started reading this thread.

Quote from: 93143
This is why conservation of energy inherently requires reaction mass.  And that is why the M-E people are so keen on pointing out that their idea is not a "reactionless" thruster, but merely a "propellantless" thruster.

Thanks for restating the problem at hand.

So....

What are they pushing on?  Woodward says, "distant matter".  Shawyer says, I think, "group velocity".

Sciama says, in 1964, "Inertial forces are exerted by matter, not by absolute space. In this form the principle contains two ideas:

"(1) Inertial forces have a dynamical rather than a kinematical origin, and so must be derived from a field theory [or possibly an actionat-a-distance theory in the sense of J.A. Wheeler and R.P. Feynman... ].

"(2) The whole of the inertial field must be due to sources, so that in solving the inertial field equations the boundary conditions must be chosen appropriately. "

[I've attached Woodward's 2004 paper, claiming fair use, for educational purposes.]

After Sciama's quote above, Woodward begins to explain his interpretation of Mach's principle, and how it can afford action at a distance.  I have a limited understanding of his line of argument.

**************************

As an aside:

This paper appears to be a translation of the one written in Chinese, and posted earlier.  It cannot be considered a peer reviewed paper.

I never said it was.

I never said that you said it was.  All you did was report the existance of the paper on the Polywell site.  You cannot be assumed to be in favor or, or opposed to the paper, on the basis of your having reported its existance alone.

You miss the point here.  Let an observation stand as an observation; do not place an accusatory frame of reference around an observation without reason.  I'm quite aware, in principle, of my imperfections; it's not about you and me.

Like I was saying, it is not a peer reviewed paper.  Furthermore, the device that these people are discussing is protected by the Chinese patent system.

As a nested aside, we all know how much they respect our patent system; with their patent system, I'm sure they're very particular about intellectual property rights.  Moving right along...

The device itself is not available for independent verification; the paper cannot be analyzed in principle by an arbitrary peer, without access to the device.  According to their illustrations, it is exactly the same device pictured in an article from 2008, which therefore offers the reviewer absolutely no new information about the device.  The paper presents the results that these researchers have measured when using the device in a certain way.

Nothing can be definitely concluded from the work of the Chinese experimenters, as presented.
Sometimes I just flat out don't get it.

Offline MP99

Re: Propellantless Field Propulsion and application
« Reply #1712 on: 11/13/2012 02:35 PM »
if there were such a thing as a tractor beam that could reach across interstellar distances we could swing though the stars like tarzan, always chosing a new star with the desired relative velocity to us. This also gives us energy for free, at least locally.

We can think up various 'propellentless-like' forms of propulsion...

The tractor beam is not propellantless - the stars are the propellant (though pulled towards the craft, rather than the normal pushed away).

The tractor beam would also be doing work against the star (to accelerate the ship), so that wouldn't be free, either?

cheers, Martin
« Last Edit: 11/13/2012 02:38 PM by MP99 »

Offline aero

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Re: Propellantless Field Propulsion and application
« Reply #1713 on: 11/13/2012 07:45 PM »
I had some fun with this by comparing the results from the subject paper to a rocket engine using massive photons as the reaction mass. The paper here:

http://www.emdrive.com/yang-juan-paper-2012.pdf

Basically, the following theory is as good as any, IMO, and a lot simpler.

Start with http://en.wikipedia.org/wiki/Photon

Energy = n*h*f where n is the number of photons, h is the Planck constant = 6.63E-34 J.s and f is frequency in cycles per second. Given that the Energy is 2500 Watts and f = 2.45 GHz, calculate the number of photons, n = 1.54E+27.

The subject paper claims Thrust = 720 mN or 0.72 N. Using T = mdot * Ve, and Ve ~= c = 299792458 m/s, calculate mdot = 2.4E-9 kg/s. It follows that each photon must mass about 1.56E-36 kg if they were being generated like a flashlight would. We know that is wrong as the upper limit of photon mass under normal conditions has been established by multiple experiments to be less than 1E-50 to 1E-60 kg.

But Wait! Look what happens when photons are constrained in a resonate cavity.

http://arstechnica.com/science/2010/11/researchers-get-trapped-photons-to-act-like-massive-particles/

Quote
At this point, the system "is formally equivalent to an ideal gas of massive bosons." Massive, in this case, being 6.7 x 10-36kg.

And 6.7E-36 kg is close enough to the above calculated 1.56E-36 kg as to make no difference. The only thing left to figure out is, "Where do these massive photons go after they react against the cavity walls?" Well obviously they tunnel into the Quantum Foam underlying the universe and disappear from our perceived reality.

http://en.wikipedia.org/wiki/Quantum_foam

Edit added: On second thought, the massive photons more likely simply disipate, returning to their normal condition with masses less than 10E-60 kg and continue to bounce around until adsorbed by the walls as heat. In any case, the question becomes, "Why does the force exhibit a preferred direction?"
« Last Edit: 11/15/2012 04:27 PM by aero »
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Re: Propellantless Field Propulsion and application
« Reply #1714 on: 11/13/2012 10:41 PM »
if there were such a thing as a tractor beam that could reach across interstellar distances we could swing though the stars like tarzan, always chosing a new star with the desired relative velocity to us. This also gives us energy for free, at least locally.

We can think up various 'propellentless-like' forms of propulsion...

The tractor beam is not propellantless - the stars are the propellant (though pulled towards the craft, rather than the normal pushed away).

The tractor beam would also be doing work against the star (to accelerate the ship), so that wouldn't be free, either?

cheers, Martin

I said 'propellentless-like' ;)

But anyway, if you look a couple of posts up you will see people claiming the EM-drive (or whichever, I get them mixed up) is actually pushing against the universe as a whole or some such, in which case it is just another propellentless-like drive also.

The thing about my Tarzan drive is that when you understand the mechanism, the seemingly-free energy is explained: a sort of gravitational slingshot effect (my tractor beam acts like a lasso, silly, but breaks no laws). free energy comes from selecting stars with different velocities). If the EM-drive acts propellentless then there is no particular reason to reject seemingly-free energy. I dont think anyone on this thread has defined another consistent behavior. (To propose it becomes less effective at high velocity requires someone to define which frame this velocity is with respect to even if not why. Without that we dont even know how it claims to behave.)

This is really something that should be investigated and explained very clearly by whoever made the original claim though. Its weird that we are left to debate it here IMO.

My absolute first reaction to any propellentless proposal is to ask is what happens if we try to construct a perpetual motion machine as described earlier, just as my first reaction to any FTL proposal is how it would behave if we attempted to create a paradox in the usual way.
« Last Edit: 11/13/2012 10:56 PM by KelvinZero »

Offline joek

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Re: Propellantless Field Propulsion and application
« Reply #1715 on: 11/14/2012 01:34 AM »
Furthermore, the device that these people are discussing is protected by the Chinese patent system.

Which device are you referring to?  The device covered by their patent claim is for measuring the net thrust of the em-drive.  They do not appear to have asserted any claims on their implementation of the em-drive, which seems to be the same as Shawyer's.

Offline IRobot

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Re: Propellantless Field Propulsion and application
« Reply #1716 on: 11/14/2012 01:53 AM »
My absolute first reaction to any propellentless proposal is to ask is what happens if we try to construct a perpetual motion machine as described earlier, just as my first reaction to any FTL proposal is how it would behave if we attempted to create a paradox in the usual way.
It is not a perpetual motion machine as energy enters the system, for example by using solar panels. The problem with perpetual motion machines is energy dissipation, not "motion".

Online KelvinZero

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Re: Propellantless Field Propulsion and application
« Reply #1717 on: 11/14/2012 02:59 AM »
My absolute first reaction to any propellentless proposal is to ask is what happens if we try to construct a perpetual motion machine as described earlier, just as my first reaction to any FTL proposal is how it would behave if we attempted to create a paradox in the usual way.
It is not a perpetual motion machine as energy enters the system, for example by using solar panels. The problem with perpetual motion machines is energy dissipation, not "motion".

Hi IRobot,
You missed the middle of this conversation.

An explanation of how a propellantless thruster can create energy from nothing is given here.
http://forum.nasaspaceflight.com/index.php?topic=13020.msg977917#msg977917

Essentially,
(a) if a propellantless thruster can produce a constant force for a constant power, then you can produce a velocity proportional to the energy put in.

(b) but kinetic energy is defined by Ek=0.5mv^2, so using a totally conventional device we can extract energy proportional to the square of the velocity.

This lets us generate more energy than we put in. The example uses some exact numbers.

Then there was some discussion of whether a propellantless thruster could follow a different equation from (a) and so on. I gave some examples but as has been pointed out, these are not truely propellantless.

I personally like the Tarzan drive as an example of how silly you can get without breaking any laws of conservation :)


Offline JohnFornaro

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Re: Propellantless Field Propulsion and application
« Reply #1718 on: 11/14/2012 02:00 PM »
Furthermore, the device that these people are discussing is protected by the Chinese patent system.

Which device are you referring to?  The device covered by their patent claim is for measuring the net thrust of the em-drive.  They do not appear to have asserted any claims on their implementation of the em-drive, which seems to be the same as Shawyer's.

I re-read the English translation of the Chinese paper.  You are correct: the device explicitly mentioned as "patented", is the measuring device, and I mis-read the first time.  However, it measures the thrust of another device, the EM-drive, which apparently has not changed in design over the last four years.

Their experimental results cannot be duplicated until both devices, the one which thrusts, and the one which measures the thrust, can be built by another, independent, lab, and its net thrust also measured.
« Last Edit: 11/14/2012 02:08 PM by JohnFornaro »
Sometimes I just flat out don't get it.

Offline aero

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Re: Propellantless Field Propulsion and application
« Reply #1719 on: 11/14/2012 03:57 PM »
Furthermore, the device that these people are discussing is protected by the Chinese patent system.

Which device are you referring to?  The device covered by their patent claim is for measuring the net thrust of the em-drive.  They do not appear to have asserted any claims on their implementation of the em-drive, which seems to be the same as Shawyer's.

I re-read the English translation of the Chinese paper.  You are correct: the device explicitly mentioned as "patented", is the measuring device, and I mis-read the first time.  However, it measures the thrust of another device, the EM-drive, which apparently has not changed in design over the last four years.

Their experimental results cannot be duplicated until both devices, the one which thrusts, and the one which measures the thrust, can be built by another, independent, lab, and its net thrust also measured.

No one cares about the thrust measurement device. The thruster is the only item of interest. There are many thrusters in the sub Newton range and all have been measured on a thrust stand of one type or another. Pick any existing thrust stand rated at 0.1 to 2 Newton thrust range and use it to measure thrust. If a particular mechanism is needed to measure the thrust then the results are bogus.

If you want to build an emdrive in your garage, you could suspend your drive on a pendulum and measure the pendulum deflection from vertical while under thrust. I'm sure you can calculate the force applied to cause the deflection you measure.
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