Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2104188 times)

Offline deltaMass

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No, it's me  :o
The air/water within the chamber will average to a higher temperature.
The ambient will stay ...ambient .

This isn't about buoyancy. It's about a simple change in the mass of air/water vapour within the cavity.
If this model is correct in accounting for the measured weight change, then we should see the same negative weight change when the cavity is flipped upside down.
« Last Edit: 05/18/2015 07:21 PM by deltaMass »

Offline pogsquog

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Since the air is not significantly contained, the pressure will equalise very rapidly, i.e. air will move about rapidly, so no significant thrust from air after power off would be expected. Instead, after power off, one would expect cooling, and a sucking back of air, resulting in a smaller force of the opposite magnitude. I expect that the air being expelled during the powered phase will be proportional to the rate of change of temperature, i.e. it would fall asymtotically as the chamber heats to steady state. This can be modelled. Assuming chamber is mostly sealed except for large vent holes in side. with holes top and bottom one might get constant convection through the device, like a pulse jet.
« Last Edit: 05/18/2015 07:25 PM by pogsquog »

Offline aero

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@Iulian Berca
I am happy to see your success and hope for many more. Congratulations!

But your video seems to show a lack of respect for the dangers of microwave radiation. As a leader in the DYI effort you must take it upon yourself to set an example of safe experimentation for all of those DYI'ers who will follow in your footsteps. Let me relate a story from the early days of Radar.

The story goes that a an airman, a radar tech in training learned of the risk of sterilization from the radiation. Wanting no children he thought that was a good idea. He stood next to the radar device and switched it on momentarily. Unfortunately for the tech, the surgeons had to amputate parts that he would have rather kept.

Lacking a complete Faraday cage, put a metal screen between yourself and the operating device. You can do everything of importance from behind the screen. Protect yourself because no one wants to hear that some DYI'er was injured by his experiment and when questioned, said, "Well, Iulian Berca did it that way so I thought if he could do it, so could I."
Retired, working interesting problems

Offline deltaMass

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Since the air is not significantly contained, the pressure will equalise very rapidly, i.e. air will move about rapidly, so no significant thrust from air after power off would be expected. Instead, after power off, one would expect cooling, and a sucking back of air, resulting in a smaller force of the opposite magnitude. I expect that the air being expelled during the powered phase will be proportional to the rate of change of temperature, i.e. it would fall asymtotically as the chamber heats to steady state. This can be modelled. Assuming chamber is mostly sealed except for large vent holes in side. with holes top and bottom one might get constant convection through the device, like a pulse jet.
I think the details are interesting, but the main takeaway from the "varying air mass" model is that it is of a calculated magnitude that is able to fully account for the measured "thrust".

Offline SeeShells

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The characteristics of the heated air will depend significantly on its humidity too.

Crank up the volume on the video, You can hear when the magnetron start to buzz and thrust appears immediately there after. When buzz stops, thrust stops. No delay.

Both of you could be correct.  Although, I have to side with TheTraveller on this one.  It would have to be a pretty drastic, and immediate change in temperature which would not have likely happened.
Thinking we're seeing real thrust (not a heated air EM balloon). I watched the initial thrust degrading slowly during the test and I'm thinking this simply could be to the Microwave ionization of the air molecules inside of the Chamber causing the air to breakdown by avalanche ionization, in microwave propagation it can play a significant role. Changes in the Q, harmonics, wave patterns, due to these ionization effects could decrease the thrust like we are seeing. It takes a little time to build up an ionized plasma to the point it would start to de-tune the chamber and decay the thrust.
http://iopscience.iop.org/1009-0630/15/10/03


As soon as the power is turned off the EM scales return quickly to zero

Offline Dortex

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No, it's me  :o
The air/water within the chamber will average to a higher temperature.
The ambient will stay ...ambient .

This isn't about buoyancy. It's about a simple change in the mass of air/water vapour within the cavity.
If this model is correct in accounting for the measured weight change, then we should see the same negative weight change when the cavity is flipped upside down.

I'm no physicist, but this all sounds like a non-issue to me. He's drilled holes into the side of his device to let out warmer air and minimize their effects on the results. If, as you say, colder air rushes back in when the device is turned off, then his entire setup almost completely eliminates any issues relating to air temperature and humidity. He runs tests for short periods of time, keeping the inside as close to ambient as possible, and constantly refreshing the entire setup- eliminating whatever tiny artifact it generates in the first place.

Offline deltaMass

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When he makes a weight measurement, he is weighing the device plus whatever air/water vapour is inside it. Therefore when there is less air inside the device, the device will weigh less. It's as simple as that. Why should a higher temperature result in less air inside the device? - that's because the density of air depends on its temperature; it decreases with higher temperature. Since the device volume is constant and the density of air has dropped, there must be less air mass inside the device at higher temperature.
mass = density * volume.

And this is no "tiny artifact" - it's an effect on order negative half a gram, which turns out to be exactly what was measured.
« Last Edit: 05/18/2015 07:57 PM by deltaMass »

Offline TheTraveller

Here is the scale weight data, run by run, frame by frame as the numbers changed. Also find excel SS if you wish to play.

Sure looks like the thrust went up and down (weight went down and then up) VERY quickly as the maggie started to hum and stopped.

Can't see heated air reacting that quickly, especially at power off.

Thrust sags could be the maggie altering frequency as it got hit by the load or even dropping power. It is only a low cost microwave maggie after all.

Baseline seems to have increased but that may be hysterious in the measuring system.

I also noted a definite but small weight increase in the 1st 1/2 sec of the maggie starting to hum, then it shot straight up (weight dropping) very fast. You can see that effect in 4 of the 5 test sequences. Almost like an initial small but clearly seen, reverse thrust (downward) until the cavity settled down.
« Last Edit: 05/18/2015 08:24 PM by TheTraveller »
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Offline SeeShells

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When he makes a weight measurement, he is weighing the device plus whatever air/water vapour is inside it. Therefore when there is less air inside the device, the device will weigh less. It's as simple as that. Why should a higher temperature result in less air inside the device? - that's because the density of air depends on its temperature; it decreases with higher temperature. Since the device volume is constant and the density of air has dropped, there must be less air mass inside the device at higher temperature.
mass = density * volume.

And this is no "tiny artifact" - it's an effect on order negative half a gram, which turns out to be exactly what was measured.
If that was the case I would like you to consider that the air takes time to evacuate the chamber and internally heat the air.  The scales would slowly increase instead the decrease like we see. This seem right?

Offline txdrive

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While buoyancy is probably not good for the experiment (keep in mind that you should want to actually measure something with some degree of accuracy here), the cables may be even worse. It's half a gram, all it takes is the cable bending a little due to  temperature difference across the materials and magnetics, so that half a gram more or less of the cable weight is supported by the scale. The bad thing about cables is that there's essentially no way to estimate anything, or at least it is far harder than to weight a self contained system, anyway.

Other issue is how the scale handles vibrations - it may or may not correctly average vibrations out.

It's not so much an issue of one force that is messing up the readings as an issue of a sum of many classical forces. One could get some very rough idea regarding the magnitude of that sum by turning the cavity 90 and 180 degrees, as some of the classical forces won't flip around.
« Last Edit: 05/18/2015 08:26 PM by txdrive »

Offline deltaMass

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When he makes a weight measurement, he is weighing the device plus whatever air/water vapour is inside it. Therefore when there is less air inside the device, the device will weigh less. It's as simple as that. Why should a higher temperature result in less air inside the device? - that's because the density of air depends on its temperature; it decreases with higher temperature. Since the device volume is constant and the density of air has dropped, there must be less air mass inside the device at higher temperature.
mass = density * volume.

And this is no "tiny artifact" - it's an effect on order negative half a gram, which turns out to be exactly what was measured.
If that was the case I would like you to consider that the air takes time to evacuate the chamber and internally heat the air.  The scales would slowly increase instead the decrease like we see. This seem right?
No, it doesn't seem right because I can't understand most of what you're saying.

Offline deltaMass

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@TheTraveller:
What are the units and semantics of your vertical scale?

Offline TheTraveller

@TheTraveller:
What are the units and semantics of your vertical scale?

Units are what the scale displayed at every change of value. Time between measurement sort of constant (due to scale update frequency) but not time logged.

You can easily put the video in 1/4 time and freeze frame it after each number change of the scale to verify the data.
« Last Edit: 05/18/2015 08:27 PM by TheTraveller »
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Offline txdrive

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So your thrust is in the opposite direction from EagleWorks, right?
« Last Edit: 05/18/2015 08:28 PM by txdrive »

Offline TheTraveller

So your thrust is in opposite direction from EagleWorks, right?

Movement is as per Shawyer. From the big end toward the small end.
Watch the video to see which way it moves.
http://emdrive.com/dynamictests.html

Shawyer also pointed it out in the attachment that Reaction (physical movement of the EM Drive) is opposite to Thrust direction.
« Last Edit: 05/18/2015 08:41 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 txdrive

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So your thrust is in opposite direction from EagleWorks, right?

Movement is as per Shawyer. From the big end toward the small end.
Watch the video to see which way it moves.
http://emdrive.com/dynamictests.html
As per Shawyer's theory papers, it should be moving wide end forward.

Offline TheTraveller

So your thrust is in opposite direction from EagleWorks, right?

Movement is as per Shawyer. From the big end toward the small end.
Watch the video to see which way it moves.
http://emdrive.com/dynamictests.html
As per Shawyer's theory papers, it should be moving wide end forward.

Reaction / EM Drive physical movement is in the opposite direction to Thrust direction. Should move toward small end. He has stated this many times.
« Last Edit: 05/18/2015 08:43 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 txdrive

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So your thrust is in opposite direction from EagleWorks, right?

Movement is as per Shawyer. From the big end toward the small end.
Watch the video to see which way it moves.
http://emdrive.com/dynamictests.html
As per Shawyer's theory papers, it should be moving wide end forward.

Reaction / EM Drive physical movement is in the opposite direction to Thrust direction. He has stated this many times.

http://www.emdrive.com/theorypaper9-4.pdf
Quote
The group velocity of the electromagnetic wave at the end plate of the larger
section is higher than the group velocity at the end plate of the smaller section. Thus
the radiation pressure at the larger end plate is higher that that at the smaller end plate.
The resulting force difference (F g1 -F g2 ) is multiplied by the Q of the resonant
assembly.

So, it would have to be mounted the larger plate forward if you want your ship to go forward. According to his "theory" anyway. No idea where his experiments are going, my guess is which ever ways vibration and shifts in the centre of mass take them.
« Last Edit: 05/18/2015 08:49 PM by txdrive »

Offline TheTraveller

So your thrust is in opposite direction from EagleWorks, right?

Movement is as per Shawyer. From the big end toward the small end.
Watch the video to see which way it moves.
http://emdrive.com/dynamictests.html
As per Shawyer's theory papers, it should be moving wide end forward.

Reaction / EM Drive physical movement is in the opposite direction to Thrust direction. He has stated this many times.

http://www.emdrive.com/theorypaper9-4.pdf
Quote
The group velocity of the electromagnetic wave at the end plate of the larger
section is higher than the group velocity at the end plate of the smaller section. Thus
the radiation pressure at the larger end plate is higher that that at the smaller end plate.
The resulting force difference (F g1 -F g2 ) is multiplied by the Q of the resonant
assembly.

So, it would have to be mounted the larger plate forward if you want your ship to go forward.

Spacecraft move in the opposite direction to the thrust of the engine. EM Drive is no different.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline TheTraveller

So your thrust is in opposite direction from EagleWorks, right?

Movement is as per Shawyer. From the big end toward the small end.
Watch the video to see which way it moves.
http://emdrive.com/dynamictests.html
As per Shawyer's theory papers, it should be moving wide end forward.

Reaction / EM Drive physical movement is in the opposite direction to Thrust direction. He has stated this many times.

http://www.emdrive.com/theorypaper9-4.pdf
Quote
The group velocity of the electromagnetic wave at the end plate of the larger
section is higher than the group velocity at the end plate of the smaller section. Thus
the radiation pressure at the larger end plate is higher that that at the smaller end plate.
The resulting force difference (F g1 -F g2 ) is multiplied by the Q of the resonant
assembly.

So, it would have to be mounted the larger plate forward if you want your ship to go forward. According to his "theory" anyway. No idea where his experiments are going, my guess is which ever ways vibration and shifts in the centre of mass take them.

Every rocket engine produces thrust in one direction and the craft moves in the opposite direction as a reaction to the thrust from the engine. What is different in the EM Drive is there is no need to expel hot gasses at high velocity to produce thrust.

With an EM Drive you point the small end of the frustum at where you want to go and apply power to the microwave generators. Thrust is generated toward the big end of the frustum and the craft accelerates in the opposite direction from the generated thrust.
"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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