Author Topic: EM Drive Developments - related to space flight applications - Thread 11  (Read 223707 times)

Offline wicoe

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It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).

I don't believe this is correct. Different reference frames will disagree on how much work was done on the ship and how much on the exhaust but all should agree with the total amount of work done.

I don't think there is any disagreement... I was talking about the work done to accelerate a specific object (i.e. to change its kinetic energy), ignoring the other parts.  Of course if you include everything, the total work to accelerate all parts of the system (i.e. exhaust + object) will be the same in any reference frame, and will equal the total amount of chemical (or other frame-independent) energy spent.  My point was that this frame independence is only achievable if you include some type of exhaust (or some external object(s) you push against or interact with) in the equation.
« Last Edit: 06/12/2018 05:37 pm by wicoe »

Offline meberbs

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It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).

I don't believe this is correct. Different reference frames will disagree on how much work was done on the ship and how much on the exhaust but all should agree with the total amount of work done.
Work is defined as change of energy of an object. If you add up the work of everything, you always get zero because of conservation of energy. When one object does work on another, it has equal and opposite work done on it. The actual number is frame dependent.

Offline X_RaY

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Isolated or not, my argument is that any additional structure within the cavity, especially a conductive one, changes the natural frequencies of the resonator. The second point I do not understand from your contributions is why an additional spectrum analyzer is needed to map the amplitudes of the E field. This could be done with a 2-port VNA in S21 mode.

By the way, you can only isolate the DC component, which is irrelevant in this case, but not the AC RF.  ;)

XRay,

This is something that you need to try. It does work.

I use 300mm of the thinnest and stiffest GHz coax as the probe, plus a longer more flexible coax to the 10dB or 20 dB or 40dB attenuator
to the freq scanner.
This is exactly what I was thinking. Inserting a coax cable into the cavity will cause the resonant frequency to rise the further in the coax is inserted. Then RF will couple with the coax shielding at varying degrees as the coax is inserted, leaking RF to the outside, which will probably be very non-linear. I would be very surprised if we could make sense of spectrum analyser readings in these conditions.

Holes in the walls and end plates do work to a limited extent. Really good are holes in the small and big end plate where the max E field intensity is projected to be.

Suggest you sim an electrically isolated 1mm dia coax inserted into the cavity from a hole in the middle of the big end, centered and at various penetration depths and see what happens to resonance.

Sorry but way too much theory and no experimental data to back it up. Heavy on theory and light on experimental data is why DIYers struggle to generate significant P-P force.
I was busy regarding the impact level of the probe as suggested by TT.
I found that there is a field distortion, but at a low level. I also found a frequency shift as assumed but, again, surprising low, in the order of ~50 kHz.
The first field simulations look promising.*

I would therefore ask the experimenters to subject the methodology described to a practical test.

Maybe using a Semi-Rigid Coaxial Cable like this one:
http://www.crossrf.com/coaxial-cables/semi-rigid-cables/sr-034-coaxial-cable-50ohm
http://crossrf.com/pdf/SR034.pdf
With connector:
https://coaxicom.com/product/straight-male-for-semi-rigid-or-ultra-flex-cable-10/
or
https://fieldcomponents.com/FC10DSF-B16-1.html

However, I am a little sceptical about the easy implementation and distinguishability of modes that also have an index in the form "TXmn3".

* TE013. Known Brady cone dimensions as it was used by EW. The three simulations where done with equal mesh densities.


« Last Edit: 06/15/2018 03:11 pm by X_RaY »

Online Monomorphic

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I would therefore ask the experimenters to subject the methodology described to a practical test.

Maybe using a Semi-Rigid Coaxial Cable like this one:

Making SMA cables is not that easy. I ordered these for less than $10 and they will arrive Thursday: https://tinyurl.com/y743rjpu

I'll just cut off one of the SMA male connectors, leaving a very short stub of the inner conductor, and solder the frayed ends of the shields. That way the other end still has a male connector that can connect to the spectrum analyser.
« Last Edit: 06/12/2018 10:10 pm by Monomorphic »

Offline TheTraveller

Testing the miniVNA tiny+ with a 1/4 wave stub antenna.

It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

How many Joules of Work will be done by a P-P drive that can generate 60,000 Newtons of Force, while accelerating a 60,000kg spaceship's mass for 100 seconds that is mid way between the orbits of Earth and Mars?

It depends on the reference frame since energy is not conserved if P-P drives work.

Energy is conserved. The KE gain of the mass during acceleration is provided by some of the input Rf energy. As a result the resonant photons wavelengths increase due to them transferring some of their energy to the accelerating mass, via asymmetric radiation pressure, and in high Q cavities the length must be increased to keep the cavity resonant.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

How many Joules of Work will be done by a P-P drive that can generate 60,000 Newtons of Force, while accelerating a 60,000kg spaceship's mass for 100 seconds that is mid way between the orbits of Earth and Mars?

It depends on the reference frame since energy is not conserved if P-P drives work.

It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).  The kinetic energy difference (after - before) depends on the ref. frame, which is quite obvious.  As a consequence, the amount of work done by the drive must depend on the ref. frame to counteract this (i.e. so that the total energy is conserved).  This is only possible if this involves propellant or some other interaction that introduces frame dependence (simply spending chemical or electric energy is not enough since it is not frame-dependent).

As you accelerate mass, it's KE increases. This is not frame dependent. It is a part of how mass responds when it is accelerated.

Mass does not know it's velocity and some external value of velocity does not alter it's inertial mass.

You are in a spaceship 1/2 way between the Earth and Mars. The ship's mass is 60,000kg. It's P-P drive system can generate 60,000 Newtons of Force. The crew turn the drive system on for 100 seconds.

Simple question is how much Work was done on the Mass by the Force during the 100 seconds?

It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).

I don't believe this is correct. Different reference frames will disagree on how much work was done on the ship and how much on the exhaust but all should agree with the total amount of work done.

I don't think there is any disagreement... I was talking about the work done to accelerate a specific object (i.e. to change its kinetic energy), ignoring the other parts.  Of course if you include everything, the total work to accelerate all parts of the system (i.e. exhaust + object) will be the same in any reference frame, and will equal the total amount of chemical (or other frame-independent) energy spent.  My point was that this frame independence is only achievable if you include some type of exhaust (or some external object(s) you push against or interact with) in the equation.

As an EmDrive accelerates, the resonant photons lose both momentum and energy at each inelastic end plate absorb and emit event. ie their emit wavelength is longer than their impact wavelength. As the tapered cavity creates an asymmetric radiation pressure enviroment, a Force differential is created. However Force alone will not do Work on Mass. There must be a source of both energy and momentum, which the photons also provide.

So the resonant photons both generate the Force and provide the Energy and Momentum to support Work being done on the Mass.

No frame other than the inside of the cavity is needed or required.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

It depends on the reference frame regardless of the drive type (i.e. even ignoring the P-P part).

I don't believe this is correct. Different reference frames will disagree on how much work was done on the ship and how much on the exhaust but all should agree with the total amount of work done.
Work is defined as change of energy of an object. If you add up the work of everything, you always get zero because of conservation of energy. When one object does work on another, it has equal and opposite work done on it. The actual number is frame dependent.

When the resonant photons do Work on Mass, their wavelengths increase as a result of the Work they have done.

Energy is conserved, ie gained KE of the Mass is balanced by the lost energy of the longer wavelength photons.

Momentum is conserved, ie gained momentum of the Mass is balanced by the lost momentum of the longer wavelength photons.
« Last Edit: 06/13/2018 03:03 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Online Jim Davis

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You are in a spaceship 1/2 way between the Earth and Mars. The ship's mass is 60,000kg. It's P-P drive system can generate 60,000 Newtons of Force. The crew turn the drive system on for 100 seconds.

Simple question is how much Work was done on the Mass by the Force during the 100 seconds?

The simple answer is : it depends.

Work is defined as the integral of force over distance:

W=Integral(F ds)

Noting that ds = v dt we can substitute in the above

W=Integral(F v dt)

Since in your example F and m are constant, a is constant, and velocity at a given time is

v = v0 + at

where v0 is the velocity at initial time t0.

Substituting

W=Integral(F (v0 + at) dt)

Since a = F/m we have

W=Integral(F v0 dt) + Integral(F^2 t dt /m)

Integrating we get

W = F v0 (t - t0) + F^2/(2 m)(t^2 - t0^2)

As you can see the work done depends on the initial velocity, ie the reference frame.

Offline meberbs

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As you accelerate mass, it's KE increases. This is not frame dependent. It is a part of how mass responds when it is accelerated.
No, it is obviously frame dependent because the kinetic energy is proportional to velocity squared. In some frames velocity (and therefore kinetic energy would be decreasing.
Mass does not know it's velocity and some external value of velocity does not alter it's inertial mass.
And therefore it does not know it's kinetic energy.
You are in a spaceship 1/2 way between the Earth and Mars. The ship's mass is 60,000kg. It's P-P drive system can generate 60,000 Newtons of Force. The crew turn the drive system on for 100 seconds.

Simple question is how much Work was done on the Mass by the Force during the 100 seconds?
This was already answered, it is frame dependent. Work is force times distance. Distance is 0.5*a*t^2+ v*t. In this equation a=F/m and v is the initial velocity in the reference frame you choose.

Quote
There must be a source of both energy and momentum, which the photons also provide.
The energy of the photons came from the battery, and the momentum came from the cavity/attached antenna. Since the momentum came from the cavity to begin with, the photons are not an independent momentum source. Energy coming from the battery is a problem because that energy is essentially frame independent, while kinetic energy is frame dependent.

Most of this has already been explained to you, so this is bordering on violating the warning in the opening post. To avoid such a problem, you need to stop acting like repeating things makes them true, and acknowledge the explanations you have been given.

Online Monomorphic

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I was busy regarding the impact level of the probe as suggested by TT.
I found that there is a field distortion, but at a low level. I also found a frequency shift as assumed but, again, surprising low, in the order of ~50 kHz.
The first field simulations look promising.*

I don't know if you cut a hole in the frustum for the probe, so I went ahead and gave it a try using Phil's latest dimensions. The same field distortions are present, but the overall mode shape is still intact. As I suspected, there is significant RF leaking from the coax shielding through the hole. But interestingly, the leaking is lower if the cavity is in peak resonance. Off resonance, by as much as ~90Khz causes the cavity to leak noticeably.  Ferrite cores are recommended between the hole and the spectrum analyser.

As soon as the rigid coax sma cable arrives tomorrow, I can test this using the older acetate and copper foil cavity that resonates at 2.45Ghz. If it works, then I can see about using the same technique on the 3D printed cavity.

One thing to note, I have not been able to excite TE013 using a stub off the side wall using Phil's latest dimensions. I had to use a loop or half loop. So i'm not sure a stub is the best coupler for this build.
« Last Edit: 06/13/2018 07:36 pm by Monomorphic »

Offline Mark7777777

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FYI FWIW:

emdrives.com redirects to the latest post on this Thread 11.

Regards
Mark

Offline X_RaY

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I was busy regarding the impact level of the probe as suggested by TT.
I found that there is a field distortion, but at a low level. I also found a frequency shift as assumed but, again, surprising low, in the order of ~50 kHz.
The first field simulations look promising.*

I don't know if you cut a hole in the frustum for the probe, so I went ahead and gave it a try using Phil's latest dimensions. The same field distortions are present, but the overall mode shape is still intact. As I suspected, there is significant RF leaking from the coax shielding through the hole. But interestingly, the leaking is lower if the cavity is in peak resonance. Off resonance, by as much as ~90Khz causes the cavity to leak noticeably.  Ferrite cores are recommended between the hole and the spectrum analyser.

As soon as the rigid coax sma cable arrives tomorrow, I can test this using the older acetate and copper foil cavity that resonates at 2.45Ghz. If it works, then I can see about using the same technique on the 3D printed cavity.

One thing to note, I have not been able to excite TE013 using a stub off the side wall using Phil's latest dimensions. I had to use a loop or half loop. So i'm not sure a stub is the best coupler for this build.

I only concentrated on the distortion and possible frequency shift due to the stub inside, so in my simulation there was no hole in the end plate and no galvanic contact between rod and cavity.
Interesting however is the additional frequency shift through the hole! With a low forward power VNA it could at least confirm the excited pattern as suggested by TT.

As for the stub antenna... It gives an very small couppling coefficient, it will not work this way. Bend the stub into phi-direction that should work for this mode.
Already suggested in Thread 3:
https://forum.nasaspaceflight.com/index.php?topic=37642.msg1412912#msg1412912
« Last Edit: 06/15/2018 09:45 pm by X_RaY »

Offline Star One

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This may be of interest to posters on here.

£720m Large Hadron Collider upgrade 'could upend particle physics'

Quote
Collider will be far more sensitive to anomalies that could lead to entirely new theories of the universe

https://www.theguardian.com/science/2018/jun/15/720m-large-hadron-collider-upgrade-could-upend-particle-physics
« Last Edit: 06/15/2018 12:00 pm by Star One »

Offline RotoSequence

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This may be of interest to posters on here.

£720m Large Hadron Collider upgrade 'could upend particle physics'

Quote
Collider will be far more sensitive to anomalies that could lead to entirely new theories of the universe

https://www.theguardian.com/science/2018/jun/15/720m-large-hadron-collider-upgrade-could-upend-particle-physics

Not likely. The LHC luminosity upgrade will let them get a lot more collision data a lot more quickly, but particle physics at terrestrially attainable energy levels is looking like a dead end for reconciling General Relativity and the Standard Model.

Offline Bob Woods

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Stephen Hawking was interred today at Westminster between Isaac Newton and Charles Darwin.


Bravo. And light speed to you Stephen....

Offline Star One

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This may be of interest to posters on here.

£720m Large Hadron Collider upgrade 'could upend particle physics'

Quote
Collider will be far more sensitive to anomalies that could lead to entirely new theories of the universe

https://www.theguardian.com/science/2018/jun/15/720m-large-hadron-collider-upgrade-could-upend-particle-physics

Not likely. The LHC luminosity upgrade will let them get a lot more collision data a lot more quickly, but particle physics at terrestrially attainable energy levels is looking like a dead end for reconciling General Relativity and the Standard Model.

Thatís a curiously pessimistic viewpoint. You almost make it sound like they are wasting their money?

Offline RotoSequence

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Thatís a curiously pessimistic viewpoint. You almost make it sound like they are wasting their money?

The LHC managed to confirm the worst fears of particle physicists when it discovered the Higgs Boson, discovered that the Higgs Boson is exactly what the standard model predicted was, and wholly ruled out the simplest model of Supersymmetry, while casting doubt on some of its more complex cousins. It's not a waste of money to improve the LHC's ability to collect data, but based on what we've seen so far, I'd be pleasantly surprised by any radical new discoveries that upend modern physics. The Standard Model is proving to be frustratingly accurate in all viable particle accelerator experiments.

Offline Star One

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Thatís a curiously pessimistic viewpoint. You almost make it sound like they are wasting their money?

The LHC managed to confirm the worst fears of particle physicists when it discovered the Higgs Boson, discovered that the Higgs Boson is exactly what the standard model predicted was, and wholly ruled out the simplest model of Supersymmetry, while casting doubt on some of its more complex cousins. It's not a waste of money to improve the LHC's ability to collect data, but based on what we've seen so far, I'd be pleasantly surprised by any radical new discoveries that upend modern physics. The Standard Model is proving to be frustratingly accurate in all viable particle accelerator experiments.

Is that because you believe we cannot generate high enough energies on the Earth for the foreseeable future? That the more interesting physics exists in the extremely high energy realms?

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