Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2098300 times)

Offline StrongGR

As far as I can tell, I am not the only one to have thought to a general relativity effect here. This paper uses a modified version of Einstein equations to explain what is going on in a conical resonant cavity without violating momentum conservation. The point is that the author uses a weak perturbation approximation and I do not know if this is fully justified.

I had read that paper. Unfortunately, as the author of the paper states:

Quote
The weakest part of the theory seems to be that there is no clear way of preventing large gravitational effects due to the magnetic field of the Earth, as predicted by Eq. (17)

Therefore the author himself admits that his model is contradicted by predicting large gravitational effects due to the Earth's magnetic field that are contrary to all experimental evidence.

Yes, this is a drawback of that paper. What I am trying to understand is the reason why, beaming a laser through a EM Drive, there appears such an odd behavior with respect to the transit time, if confirmed. The only explanation that comes to mind is that some kind of warping is happening inside the device. This is not so strange as just an e.m. plane wave warps space-time even if by a very tiny (unmeasurable?) quantity. Now, it would be interesting to evaluate the full behavior of the frustum with respect to such laser beam propagation inside the cavity taking into account the Q factor, the frequency and the input power yielding the field intensity. This could be large enough to produce a meaningful and accessible number to the experimental setup conceived by Eagleworks.

Offline Spaniard

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Multiple reflections of a photon help nothing.
Yeah. Because most of us are completely sure that newtons law are correct, the only way that EMDrive and similar devices could work is transferring momentum. What, where and how are the questions.

It must be something different to photons and it must exists before, because push photons will mean less pushing for this energy.
White talk about virtual particles. I thing that the form could be more exotic. Something like a partially stable perturbation of quantum vacuum. Something like a vortex in a fluid but in quantum form, like a field not locally binded to a particle.

Whatever it was, it must carry energy by itself so push it carries more momentum that pure photons.
If a photon is like a fish in water, these unknown "momentum carriers" must be like walls in water. It must push vacuum energy, so it carries more momentum in the same way as you push more mass for the same energy.

Offline sanman

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Just looking at this EMdrive paper on force measurement:

http://www.emdrive.com/EmDriveForceMeasurement.pdf

Quote
The most important point to be made, is that to measure force, the cavity must
experience acceleration. In a fully restrained cavity, thrust and reaction force
cancel out.

Why is that?

Quote
This situation is unique to a propellantless thruster such as EmDrive and analogies
with conventional devices are pointless.

Why is that?

Quote
It therefore appears that a force measurement can only be made in a dynamic
environment, ideally by allowing the thruster to accelerate, measuring that
acceleration, and then calculating the thrust from T = -Ma

Why can force only be measured when it accelerates?
Is he saying that if there's no motion, there's no thrust?

Offline CW

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Multiple reflections of a photon help nothing.
Yeah. Because most of us are completely sure that newtons law are correct, the only way that EMDrive and similar devices could work is transferring momentum. What, where and how are the questions.

It must be something different to photons and it must exists before, because push photons will mean less pushing for this energy.
White talk about virtual particles. I thing that the form could be more exotic. Something like a partially stable perturbation of quantum vacuum. Something like a vortex in a fluid but in quantum form, like a field not locally binded to a particle.

Whatever it was, it must carry energy by itself so push it carries more momentum that pure photons.
If a photon is like a fish in water, these unknown "momentum carriers" must be like walls in water. It must push vacuum energy, so it carries more momentum in the same way as you push more mass for the same energy.

I previously raised the question whether or not the standing EM wave within the cavity could be interpreted - as per quantum mechanics - as a confined (and possibly exotic) particle, due to the dualism of wave and particle. Perhaps some of our more prominent physicists could say something about this possibility? Is it correct to assume that this standing wave can be interpreted as a confined particle? Could we perhaps view a resonating EM wave cavity as a means to dynamically 'synthesize' or evoke 'exotic matter' ?
Reality is weirder than fiction

Offline Spaniard

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Could we perhaps view a resonating EM wave cavity as a means to dynamically 'synthesize' or evoke 'exotic matter' ?
I think that the term "momentum carrier" is a good name for something that we really don't know.
Particles? Fields? Something more exotic?
A photon is easy to detect because interact with electrons. How could detect something with unknown properties that I suppose interact weakly to be undetected until now?
« Last Edit: 05/06/2015 09:09 AM by Spaniard »

Offline sanman

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Multiple reflections of a photon help nothing.
Yeah. Because most of us are completely sure that newtons law are correct, the only way that EMDrive and similar devices could work is transferring momentum. What, where and how are the questions.

It must be something different to photons and it must exists before, because push photons will mean less pushing for this energy.


The waveguide seems to be able to extract momentum from the photon in a way that can't be done with regular fermionic exhaust particles. The photon's energy and momentum are tied to its wavelength and are entirely accessible/exploitable through this, whereas that's not really true for fermionic exhaust particles, whose energy and momentum are tied to both velocity and intrinsic mass.

Since the conical waveguide is axisymmetric about the axis of thrust/acceleration/motion, it is able to bleed/suck energy (momentum) off the photon, in a way that can't occur when colliding with the other side of the cavity where there is no waveguide. Is this creating an inelastic collision for the photon on the waveguide side of the cavity only?
« Last Edit: 05/06/2015 09:26 AM by sanman »

Offline TheTraveller

After rereading all the Shawyer papers and the web site pages several times I discovered Shawyer had defined the TC of his drive as TC = Q / (Fr 2 Pi).

http://www.emdrive.com/Toulouse2010paper01.doc

Example was Fr = 4GHz, Q = 50,000, TC = 2us.
So the time to effectively fully charge = TC x 5 = 10us.

For Shawyer's 1st system he had Fr = 2.45GHz, Q = 5,900, TC = 0.38us or 1.9us to fully charge.

I see this as saying a really high Q EM Drive could take a really long time to charge the cavity.

For his 1st superconducting cavity with Fr = 3.85GHz, Q = 6,800,000 = TC 280us = 1.4ms to fully charge.

Is probably why his space plane uses 8 cavities that are pulse cycled and phased apart as their Q could be 1,000 times higher with cavity charge times of over a second. If not smoothed out, could be a bumpy ride.

Pulse phasing discussed here:
http://s000.tinyupload.com/index.php?file_id=05426775513544255924
« Last Edit: 05/06/2015 12:22 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Hmm, so let me maybe replace the photon rocket idea with a solar sail.

So you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.

But suppose your sail could experience multiple collisions with each photon that came out of the emitter? So that's the waveguide that's allowing this to happen. And each of those collisions is transferring some momentum. So the sum total of all momentum that a photon can transfer to the waveguide can't exceed the original momentum of the photon when you first produced/emitted it. So net thrust is zero because of the anti-thrust from producing the original photon.

Hmm, so now it doesn't work again...

I better go ask GoatGuy.  :P

As far as I know, and I'm no expert, a solar sail can have the light source on board, simply because the photons that hit the sail impart their energey/momentum, and the ones that do not hit the sail, don't.  I once thought up a glowworm powered spacecraft working on the same principal.  A colony of glowworms lives in a conical structure that is highly reflective on the inner surface, except for the large end at the back which is transparent.  All the photons that hit the surface are reflected (so produce momentum), the ones that shoot out the back window are not so there is a gain in momentum forwards.  If only the suckers were immortal and didn't need feeding...

Offline Spaniard

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Pulse phasing discussed here:
A interesting idea. That the EMDrive could be something like a "momentum capacitator", in form of photons inside the cavity. That must be accounted accurately, because is a good source of errors.
Momentum could be "transfered" in time. A lot of photons are accumulated inside and when the walls of EMDrive change the temperature, the light reflect more than before, making do absorbed at different rates on different walls of the EMDrive making the net momentum accumulated in the photons.
But if the photons are accumulated on some time and released on less time and measured in this smaller time window, the force could be accounted greater than really are.

This hypotesis would require a "charging time" on the EMDrive before the measurement.

Offline TheTraveller

Pulse phasing discussed here:
http://s000.tinyupload.com/index.php?file_id=05426775513544255924
A interesting idea. That the EMDrive could be something like a "momentum capacitator", in form of photons inside the cavity. That must be accounted accurately, because is a good source of errors.
Momentum could be "transfered" in time. A lot of photons are accumulated inside and when the walls of EMDrive change the temperature, the light reflect more than before, making do absorbed at different rates on different walls of the EMDrive making the net momentum accumulated in the photons.
But if the photons are accumulated on some time and released on less time and measured in this smaller time window, the force could be accounted greater than really are.

This hypotesis would require a "charging time" on the EMDrive before the measurement.

Charging time is per the cavity TC x 5 (see attached), which is frequency and Q dependent as per:

Charge time = 5 x TC.
TC = Q / (Fr 2 Pi)

BTW this is not an EM Drive specific resonate circuit TC calc.

So maybe a small delay between saying "Engage" and the ship starting to accelerate, even with a 2 x 4 straight cavity EM Drive engine? Maybe the new V8 like space engine?
« Last Edit: 05/06/2015 12:24 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline rrb6699

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hello all.  I have made a couple reply posts thus far and just found this site.  I'm very excited and fascinated about EM.  I hope to make some small contribution as I come "up to speed" on this subject.

if interested, please check my other posts for replies so I don't have to duplicate them here.  nice work on the discovery.  I have several questions forthcoming that will influence my posts that I reserve for now so as to not speak before I understand better.

regards!

Ray

Offline KelvinZero

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So you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.
If the sail is reflective then it delivers twice the momentum of when the photon was initially released. Think of it like a baseball. When someone throws it and another catches it, the actions cancel. This is like absorbing the photon. If the catcher throws it back again as well (reflection) this is like a whole new throw. Luckily due to conservation of momentum we need not worry about the details, we can just look at before and after.

(edit: some might have misread this to say the reflection doubles effectiveness over just emitting a photon. I was trying to explain why emitting a photon and then reflecting it does not cancel to zero, but is instead just like emitting a photon in the other direction)
« Last Edit: 05/06/2015 01:45 PM by KelvinZero »

Offline TheTraveller

So you've got a solar sail that is moving because photons are hitting it. But what if your photon source isn't some external sun/star, but is actually sitting onboard the ship attached to the solar sail? Then it sounds like you can't generate any net thrust, since whatever momentum your photons transfer to the sail is offset by the momentum that was lost when the photons popped out of your onboard emitter.
If the sail is reflective then it delivers twice the momentum of when the photon was initially released. Think of it like a baseball. When someone throws it and another catches it, the actions cancel. This is like absorbing the photon. If the catcher throws it back again as well (reflection) this is like a whole new throw. Luckily due to conservation of momentum we need not worry about the details, we can just look at before and after.
The ball is not caught and thrown back. Instead it bounces off the catcher's glove, transferring to it the momentum gained from the 1st thrower. So no overall momentum gain.
« Last Edit: 05/06/2015 12:05 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline deltaMass

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I find these descriptions all rather imprecise. Let's do this with a laser first.
We begin with zero momentum. The laser emits a photon bunch of momentum +p forwards towards the sail, and the laser recoils with -p. Momentum conserved because +p + (-p) = 0, which is was originally. Now the photon bunch hits the sail with +p and rebounds (100% reflectivity) with -p. So the bunch experiences a momentum change of -2p = -p - (+p) and so the sail experiences an equal and opposite change of +2p forwards. But shortly before the attached laser had received -p, so the sail+laser combination gets a net +p of forward momentum. The bunch is travelling backwards with -p. Total momentum is conserved.

So yes, Victoria, you can blow into your own sail.

But notice we could have obtained the same result with the laser simply pointing backwards, acting like a photon rocket. +p for laser, -p for photons, as before. But we could have ditched the sail in this case, thus reducing the all-up mass and getting more acceleration. So a sail is a dumb idea when you have a laser.

Now repeat with an isotropic radiator like a glowing ball of light. This time a reflector is definitely needed, otherwise nothing moves, there being no preferred direction. The best reflector arrangement is to place the globe at the focus of a paraboloid mirror. Once again we get forward momentum for globe+reflector, as we still have an exhaust. But a little thought will show that it's not as efficient as the laser, because some energy is lost to the sides.

Offline Fugudaddy

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Okay, so this is a totally utterly, fascinating, and amazing place to be right now. Thank you all for the amazing science that's being done right here in front of our eyes. If this thing does actually pan out into something 'real', then being here, now, at the edge of this discovery is a heady place to be.

IANAS (I am not a scientist), the advanced maths are too hard for my brain. But I do have a good head for the theory of all of this. I've followed along with this whole thread but hadn't seen any discussion on a particular aspect (the Quantum Vacuum) that was in the NSF article.

So as I understand the EM drive:
EM radiation is pumped into a particularly shaped container which causes reflections and resonance as the waves bounce around. Something in the way those waves bounce causes particles to become more energized in one direction over another direction, resulting in, basically, thrust.

Yeah, utterly simplified.

So there seems to be some debate about a few things that seemed obvious to me, but hey, let's see how good my understanding really is.

There is no way that this could be a 'free energy' system, simply because the container is not absolute. The waves lose energy either through the vessel or through momentum exchange with the walls/interior particles, so more energy is always required to be 'pumped' in from the outside. Correct?

There is also no way that this could violate FTL, so far as I understand it, since as the container itself approaches C, it is no longer quite the same 'closed system' as it was before. I would guess as the whole system approaches C, the way the EM radiation bounces changes enough that the effects that are being generated would end up changing enough to stop doing whatever it is they're doing now.

So here's a theory, such as it is. The EM waves are 'cut' and 'squeezed' by the shape of the vessel. This (appears) to have some effect on gravity/space time (hence the confusion regarding 'warp' drives), as the concentration/focus of the EM waves is increased with each subsequent 'bounce' in the chamber.

The image I had in mind was of a jet, flying low over water. The disturbance of the airflow causes a specific shape (a 'rooster tail') to form behind the jet as the water particles are 'lifted' from the surface by the energy of the air.

Could there be some quantum mechanism that's doing something similar- the compressed waves somehow 'perturbing' the Quantum Vacuum and pushing (real or virtual) particles into a higher energy state, (preserving the momentum law), which then transfers upwards eventually resulting in particles that are in the slightly more excited state in the direction of the 'pull' of the compressed wave travelling by.

Either way, this is a fascinating place to be. Thank you for all the science :D
 

Offline KelvinZero

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So here's a theory, such as it is. The EM waves are 'cut' and 'squeezed' by the shape of the vessel.
It does look a bit like a juicer ;)

Offline Rodal

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Regarding the main controller parameter for the EM Drive

It is my understanding, from what Paul March wrote, that the main controlling parameter in determining the thrust generation performance of the EM-Drive is the rate of phase modulation of the RF signal that is injected into the resonant cavity. 

This requires an FM modulated signal of around 100 kHz deviation that dithers back and forth around the resonant cavity's resonant frequency as fast as possible. 

One has to feed the cavity through a 2 foot long RG-8 cable with Type-N connectors with the other end of this coax connected to a 3-Stub tuner that is used to set the 50 ohm Smith Chart Z-matching circle to an impedance solution that matches the 50 ohm load AND generates the narrowest +/-90 degree capacitive to inductive reactive phase change bandwidth in the cavity.  This phase change bandwidth needs to be 10 kHz or less and preferable less than 4 kHz. 

This information is useful to correctly and consistently tune an EM-drive prototype for maximum thrust.

If anybody has a different understanding of what he wrote, it would be useful to know.
« Last Edit: 05/06/2015 03:13 PM by Rodal »

Offline TheTraveller

Regarding the main controller parameter for the EM Drive

It is my understanding, from what Paul March wrote, that the main controlling parameter in determining the thrust generation performance of the EM-Drive is the rate of phase modulation of the RF signal that is injected into the resonant cavity. 

This requires an FM modulated signal of around 100 kHz deviation that dithers back and forth around the resonant cavity's resonant frequency as fast as possible. 

One has to feed the cavity through a 2 foot long RG-8 cable with Type-N connectors with the other end of this coax connected to a 3-Stub tuner that is used to set the 50 ohm Smith Chart Z-matching circle to an impedance solution that matches the 50 ohm load AND generates the narrowest +/-90 degree capacitive to inductive reactive phase change bandwidth in the cavity.  This phase change bandwidth needs to be 10 kHz or less and preferable less than 4 kHz. 

This information is useful to correctly and consistently tune an EM-drive prototype for maximum thrust.

If anybody has a different understanding of what he wrote, it would be useful to know.
Thought Paul's latest pathway was to duplicate the 1st Shawyer teeter-totter test rig and blast away with a wide band magnetron and waveguide to feed the cavity. Hope they add the ability to manually adjust / tune the cavity length as Shawyer did before he went to an active feedback loop to lock the narrow band RF to the cavity resonance in the curved end plates Flight Thruster.
« Last Edit: 05/06/2015 02:55 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline Notsosureofit

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My understanding was that he could set the match to obtain the maximum phase change across the resonance line.   This would give him the maximum effective Q.  The FM dither would be a means of following the resonance.  Back when, I used a double balanced modulator to find the 2 half-power points as the most accurate way to identify the center frequency. (but I didn't need a carrier there, I was measuring linewidth) AM or FM can be used the same way and in these cases you have power at the center of the resonance.

Offline TheTraveller

My understanding was that he could set the match to obtain the maximum phase change across the resonance line.   This would give him the maximum effective Q.  The FM dither would be a means of following the resonance.  Back when, I used a double balanced modulator to find the 2 half-power points as the most accurate way to identify the center frequency. (but I didn't need a carrier there, I was measuring linewidth) AM or FM can be used the same way and in these cases you have power at the center of the resonance.
Was this with or without a dielectric inside the cavity?

If EW do as they have said and replicate Shawyer & the Chinese, then they will not be using dielectrics.
http://forum.nasaspaceflight.com/index.php?topic=36313.msg1355764#msg1355764
« Last Edit: 05/06/2015 03:36 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

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