Author Topic: EM Drive Developments - related to space flight applications - Thread 10  (Read 1635320 times)

Offline TheTraveller


Hi PN,

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


I do not understand this document. The meaning is that I can not make it resonate in my brain with physics I have learned. Either it is not consistent with reality, or the physics I have learned does not describe reality, or my brain does not have the ability to relate them.

It doesn't make sense to me.  If it could accelerate then a force from a device that restricts it from accelerating should measure a force.  Even if some gravitational field was acting on the EM drive and acted on the measuring device the measuring device still restricts the Frustum from accelerating so should measure a force.

Even in the case of 2 mirrors and both being restricted from accelerating via light bouncing between them with massive Q, one should still be able to measure a force on the mirror. 

The only exception I could possibly think of might be a gravitational field that accelerates both the Frustum and a scale sitting with it.  In this case the frustum and scale would both become lighter, in the case of lift off maybe they could both could ascend vertically.  This is a big if and regardless the case with the force measurement device attached to a non-moving room will definitely not allow the EM drive to vertically lift off with out resistance. 

I would suggest for those who have done the experiment, with the EM drive cavity on the free to rotate accelerating arm, to calculate the force necessary to accelerate their cavity at the rate it appears to.   Next, make an apparatus that restricts this free acceleration of the rotating arm, can measure force, and it should measure a force.

For an EmDrive to generate thrust, it must be accelerating, small end forward.

On a torsion test rig, when the back or resistive force created by the forward motion of the EmDrive's acceleration equals the EmDrive's generated force, forward motion stops, acceleration stops, the EmDrive drops out of Motor mode and force generation stops.

This occurs as without acceleration, there are no differential Doppler shifts occurring inside the EmDrive as Roger explains in his 2013 IAC paper, section 2:

http://www.emdrive.com/IAC13paper17254.v2.pdf

3 modes of operation:

1) Idle mode:
Quote
If the cavity acceleration A is zero, then the relative velocity between the large and small plates, at the time of wavefront reflection, is also zero.

This will result in an overall zero Doppler shift.

2) Motor mode:
Quote
However with a positive acceleration, the overall Doppler shift will be negative.

This will lead to a reduction in stored energy in the cavity, and thus a reduction in Q, and a reduction in thrust.

The kinetic energy gained by the cavity will be balanced by the stored energy lost by the cavity.

This is EmDrive in “motor” mode

3) Generator mode:
Quote
With a negative acceleration, the overall Doppler shift will be positive.

This will lead to an increase in stored energy, which is balanced by the loss of kinetic energy from the cavity.

This is EmDrive in “generator” mode.
« Last Edit: 11/09/2017 03:45 am by TheTraveller »
It Is Time For The EmDrive To Come Out Of The Shadows

Offline TheTraveller

That quote changes nothing about my previous statements, and it is a waste of time to respond to directly when you haven't considered those previous statements. Maybe you should look at wicoe's post above for further detail on how incredibly wrong that paper is.
It Is Time For The EmDrive To Come Out Of The Shadows

Offline meberbs

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On a torsion test rig, when the back or resistive force created by the forward motion of the EmDrive's acceleration equals the EmDrive's generated force, forward motion stops, acceleration stops, the EmDrive drops out of Motor mode and force generation stops.
You just conflated "forward motion stops" and "acceleration stops." When the forces on an object are balanced, the motion does not stop, it continues at a constant speed. In this case, that causes the torsional pendulum to apply increased force which results in acceleration in the other direction, gradually slowing the rotational speed, and eventually reversing the direction of the rotation.

The rest of what you just posted can be addressed once you understand these basic facts.

Offline dustinthewind

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Hi PN,

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


I do not understand this document. The meaning is that I can not make it resonate in my brain with physics I have learned. Either it is not consistent with reality, or the physics I have learned does not describe reality, or my brain does not have the ability to relate them.

It doesn't make sense to me.  If it could accelerate then a force from a device that restricts it from accelerating should measure a force.  Even if some gravitational field was acting on the EM drive and acted on the measuring device the measuring device still restricts the Frustum from accelerating so should measure a force.

Even in the case of 2 mirrors and both being restricted from accelerating via light bouncing between them with massive Q, one should still be able to measure a force on the mirror. 

The only exception I could possibly think of might be a gravitational field that accelerates both the Frustum and a scale sitting with it.  In this case the frustum and scale would both become lighter, in the case of lift off maybe they could both could ascend vertically.  This is a big if and regardless the case with the force measurement device attached to a non-moving room will definitely not allow the EM drive to vertically lift off with out resistance. 

I would suggest for those who have done the experiment, with the EM drive cavity on the free to rotate accelerating arm, to calculate the force necessary to accelerate their cavity at the rate it appears to.   Next, make an apparatus that restricts this free acceleration of the rotating arm, can measure force, and it should measure a force.

For an EmDrive to generate thrust, it must be accelerating, small end forward.

On a torsion test rig, when the back or resistive force created by the forward motion of the EmDrive's acceleration equals the EmDrive's generated force, forward motion stops, acceleration stops, the EmDrive drops out of Motor mode and force generation stops.

...

The underlined appears to me your acknowledging a constant force being applied to the torsion pendulum's constant restive force giving the pendulum a measured deflection.  Yet you state that when it stops accelerating/deflecting it stops generating force.  The problem is the EM drive must continue to generate the force in opposition to the pendulums counter force for the pendulum to stay deflected.  This implies the EM drive does generate a constant force even when it is not accelerating. 
« Last Edit: 11/09/2017 04:07 am by dustinthewind »
Follow the science? What is science with out the truth.  If there is no truth in it it is not science.  Truth is found by open discussion and rehashing facts not those that moderate it to fit their agenda.  In the end the truth speaks for itself.  Beware the strong delusion and lies mentioned in 2ndThesalonians2:11.  The last stage of Babylon is transhumanism.  Clay mingled with iron (flesh mingled with machine).  MK ultra out of control.  Consider bill gates patent 202060606 (666), that hacks the humans to make their brains crunch C R Y P T O. Are humans hackable animals or are they protected like when Jesus cast out the legion?

Offline ThatOtherGuy

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The Chinese EM Drive that reportedly is being tested in space

Jose, forgive me, but... is the "Chinese EMDrive space test" a real thing ? Not willing to "troll" or whatever, but as far as I can say, sounds like those about such a test were just unconfirmed voices (at best); do you have some surefire information about the fact that such tests are really being carried on ?

Offline Rodal

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The Chinese EM Drive that reportedly is being tested in space

Jose, forgive me, but... is the "Chinese EMDrive space test" a real thing ? Not willing to "troll" or whatever, but as far as I can say, sounds like those about such a test were just unconfirmed voices (at best); do you have some surefire information about the fact that such tests are really being carried on ?
I don't have any further information than has been discussed in this forum.  That's why I was careful to write

Quote
The Chinese EM Drive that reportedly is being tested in space

with emphasis on reportedly as being information that has been reported in the media.  Of course those reports may be false.   If I thought that it was a fact, I would not have used the qualifier "reportedly" which considerably weakens the statement.

Here is the CCTV report translated to English:



Furthermore, if my recollection is correct, I seem to recall Potomac Neuron writing that the test in space was not an unqualified success.
« Last Edit: 11/09/2017 01:28 pm by Rodal »

Offline PotomacNeuron

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Furthermore, if my recollection is correct, I seem to recall Potomac Neuron writing that the test in space was not an unqualified success.

There were anecdotes that this device would be tested on Shijian-17 experimental satellite. After a few weeks, when other devices tested successfully had news about their successes (for example, an ion thruster and a chemical thruster using non-toxic ADN), this device did not have any news. That was a sign of failure from experience about the way things were reported in China. Furthermore, there were anecdotes that it failed on some Chinese forums. Oyzw, a member of this forum, said in a Chinese forum that his messenger in the same institute with Chen Yue (the leader of the project) told him Chen blamed electrical or mechanical ("机电") problems  for the failure. Oyzw is still active. His last post is the first one on page 127.
« Last Edit: 11/10/2017 01:58 am by PotomacNeuron »
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Offline Rodal

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Posted yesterday.  It discusses Dr. White's (NASA) theory of the Quantum Vacuum and the EM Drive at about 1:47 ...
Says "Sorry Internet."  At 6:00 says that the notion of using the Quantum Vacuum for the EM Drive "is particularly silly"
« Last Edit: 11/09/2017 04:22 pm by Rodal »

Online JonathanD

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Posted yesterday.  It discusses Dr. White's (NASA) theory of the Quantum Vacuum and the EM Drive at about 1:47 ...
Says "Sorry Internet"

The host was not entirely helpful, we already know it *shouldn't* work.

Offline Bob012345

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It made sense to me just fine.  Maybe the difference is physics as a physicist describes it vs. experiment as an engineer does it. Both are true but sometimes are expressed in different language.  :)

I don't think this depends on the background... if you believe this document makes sense, do you also believe that my comments below (in red) make NO sense?  If yes, can you please elaborate?

Assuming, (and I'm not an expert on reaction forces in this static test rig), the reaction force exists and acts on the scale.....

The statement about scales seems correct because if an EMDrive actually produces a thrust less than the weight of the device, the total forces on it are the weight, the thrust and the Normal force between the device and the scale. The Normal force adds to the thrust to equal the weight. If on the scale there is a reaction force equal to the thrust, it adds to the Normal force which also total to the weight. The normal force is variable and disappears when the thrust is equal to the weight at which point there is no more contact with the scale. This is different than the situation where a string was partially supporting the device but attached to an outside structure. In that case the scale would read a reduced weight because the reaction force does not act on the scale.

Your statement seems to presume the EMDrive can't produce a net force and the reaction and thrust always cancel on the device itself. The original statement and my response assume, just for the discussion, that the device does produce a net thrust and if it did the scales would just register the weight until the device thrust equals gravity.

An equivalent situation might be a small rocket motor or a propeller between a device and a scale that pushes a device up and the reaction gasses impinging on the scale pushing it down.
« Last Edit: 11/09/2017 04:38 pm by Bob012345 »

Offline Kenjee

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Motor mode... generator mode.. groundhog day!

Offline Rodal

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For an EmDrive to generate thrust, it must be accelerating, small end forward.

On a torsion test rig, when the back or resistive force created by the forward motion of the EmDrive's acceleration equals the EmDrive's generated force, forward motion stops, acceleration stops, the EmDrive drops out of Motor mode and force generation stops.

This occurs as without acceleration, there are no differential Doppler shifts occurring inside the EmDrive as Roger explains in his 2013 IAC paper, section 2:

http://www.emdrive.com/IAC13paper17254.v2.pdf

3 modes of operation:  ...


It made sense to me just fine.  Maybe the difference is physics as a physicist describes it vs. experiment as an engineer does it. Both are true but sometimes are expressed in different language.  :)

I don't think this depends on the background... if you believe this document makes sense, do you also believe that my comments below (in red) make NO sense?  If yes, can you please elaborate?

Assuming, (and I'm not an expert on reaction forces in this static test rig), the reaction force exists and acts on the scale.....

The statement about scales seems correct because if an EMDrive actually produces a thrust less than the weight of the device, the total forces on it are the weight, the thrust and the Normal force between the device and the scale. The Normal force adds to the thrust to equal the weight. If on the scale there is a reaction force equal to the thrust, it adds to the Normal force which also total to the weight. The normal force is variable and disappears when the thrust is equal to the weight at which point there is no more contact with the scale. This is different than the situation where a string was partially supporting the device but attached to an outside structure. In that case the scale would read a reduced weight because the reaction force does not act on the scale.

Your statement seems to presume the EMDrive can't produce a net force and the reaction and thrust always cancel on the device itself. The original statement and my response assume, just for the discussion, that the device does produce a net thrust and if it did the scales would just register the weight until the device thrust equals gravity.

An equivalent situation might be a small rocket motor or a propeller between a device and a scale that pushes a device up and the reaction gasses impinging on the scale pushing it down.
The discussion about Shawyer's explanation would be easier to follow if it could be done with people posting:

1) the free body diagram that they are proposing https://en.wikipedia.org/wiki/Free_body_diagram

2) dynamics can also be incorporated in a free-body-diagram using D'Alembert's principle  https://en.wikipedia.org/wiki/D%27Alembert%27s_principle







« Last Edit: 11/09/2017 07:37 pm by Rodal »

Offline wicoe

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I would just like to note that special care must be taken to avoid confusion between the reaction force (which is a "real" force exerted *by* an object to counteract the force exerted upon the object) and the inertial force, which is a fictitious force imagined to be acting *upon* the object.
« Last Edit: 11/09/2017 08:10 pm by wicoe »

Offline Rodal

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...
I would just like to note that special care must be taken to avoid confusion between the reaction force (which is a "real" force exerted *by* an object to counteract the force exerted upon the object) and the inertial force, which is a fictitious force imagined to be acting *upon* the object.
A funny quote on so-called "fictitious forces" (which indeed the D'Alembert inertial forces are)



Quote from: Engelbert Schücking
Mach’s principles – whatever they may be –
will always find their defenders and believers.
When one of its promoters, Dennis Sciama,
slammed on the brakes of his car, propelling
his girlfriend, seated next to him, toward the
windshield, she was heard to be moaning,
‘All those distant galaxies!’”

Engelbert Schücking

https://en.wikipedia.org/wiki/Engelbert_Sch%C3%BCcking


Quote from: Wikipedia
Figure 1: Top panel: accelerating car of mass M with passenger of mass m. The force from the axle is (m + M)a. In the inertial frame, this is the only force on the car and passenger.
Center panel: an exploded view in the inertial frame. The passenger is subject to the accelerating force ma. The seat (assumed of negligible mass) is compressed between the reaction force –ma and the applied force from the car ma. The car is subject to the net acceleration force Ma that is the difference between the applied force (m + M)a from the axle and the reaction from the seat −ma.
Bottom panel: an exploded view in the non-inertial frame. In the non-inertial frame where the car is not accelerating, the force from the axle is balanced by a fictitious backward force −(m + M)a, a portion −Ma applied to the car, and −ma to the passenger. The car is subject to the fictitious force −Ma and the force (m + M)a from the axle. The difference between these forces ma is applied to the seat, which exerts a reaction −ma upon the car, so zero net force is applied to the car. The seat (assumed massless) transmits the force ma to the passenger, who is subject also to the fictitious force −ma, resulting in zero net force on the passenger. The passenger exerts a reaction force −ma upon the seat, which is therefore compressed. In all frames the compression of the seat is the same, and the force delivered by the axle is the same.
« Last Edit: 11/09/2017 11:20 pm by Rodal »

Offline spupeng7


Furthermore, if my recollection is correct, I seem to recall Potomac Neuron writing that the test in space was not an unqualified success.

There were news that two new electrical thrusters ("电推")would be tested on Shijian-17 experimental satellite. People on several Chinese forums decoded that one is this device and the other is an ion thruster. After a few weeks, when other devices tested successfully had news about their successes (including the ion thruster), this device did not have any news. That was a sign of failure from experience about the way things were reported in China. Furthermore, there were anecdotes that it failed on some Chinese forums. Oyzw, a member of this forum, said in a Chinese forum that his messenger in the same institute with Chen Yue (the leader of the project) told him Chen blamed electrical or mechanical ("机电") problems  for the failure. Oyzw is still active. His last post is the first one on page 127.
PotomacNeuron,
do you have details of the source of this news? I found it difficult to get reliable translations. It seems to me that this information is crucial to funding applications in the US and in Europe.
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Offline PotomacNeuron

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Furthermore, if my recollection is correct, I seem to recall Potomac Neuron writing that the test in space was not an unqualified success.

There were news that two new electrical thrusters ("电推")would be tested on Shijian-17 experimental satellite. People on several Chinese forums decoded that one is this device and the other is an ion thruster. After a few weeks, when other devices tested successfully had news about their successes (including the ion thruster), this device did not have any news. That was a sign of failure from experience about the way things were reported in China. Furthermore, there were anecdotes that it failed on some Chinese forums. Oyzw, a member of this forum, said in a Chinese forum that his messenger in the same institute with Chen Yue (the leader of the project) told him Chen blamed electrical or mechanical ("机电") problems  for the failure. Oyzw is still active. His last post is the first one on page 127.
PotomacNeuron,
do you have details of the source of this news? I found it difficult to get reliable translations. It seems to me that this information is crucial to funding applications in the US and in Europe.

I can't find the source. I will modify my post accordingly. Some anecdotes were found to be from oyzw. The best official news is still this one, as have been discussed multiple times here, http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357004.htm. The best translation is by Baidu (usually better than google translation), as: http://fanyi.baidu.com/transpage?query=http%3A%2F%2Fdigitalpaper.stdaily.com%2Fhttp_www.kjrb.com%2Fkjrb%2Fhtml%2F2016-12%2F11%2Fcontent_357004.htm&source=url&ie=utf8&from=auto&to=zh&render=1 and the relevant quote is: "Chen Yue introduced, they have completed the development of test equipment for flight test, is being carried out in orbit validation."
You may ask him about the news. Thanks.

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Offline PotomacNeuron

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I can't find the source. I will modify my post accordingly. Some anecdotes were found to be from oyzw. The best official news is still this one, as have been discussed multiple times here, http://digitalpaper.stdaily.com/http_www.kjrb.com/kjrb/html/2016-12/11/content_357004.htm. The best translation is by Baidu (usually better than google translation), as: http://fanyi.baidu.com/transpage?query=http%3A%2F%2Fdigitalpaper.stdaily.com%2Fhttp_www.kjrb.com%2Fkjrb%2Fhtml%2F2016-12%2F11%2Fcontent_357004.htm&source=url&ie=utf8&from=auto&to=zh&render=1 and the relevant quote is: "Chen Yue introduced, they have completed the development of test equipment for flight test, is being carried out in orbit validation."
You may ask him about the news. Thanks.

One such anecdotes: https://www.zhihu.com/question/53602370 in comments: The 73 agreed with the answer
In 2016, a small space experiment that was not very interesting could have an impact on the course of human history.
Several kinds of non working microwave thruster principle verification machine, by China Aerospace 5 Institute on the practice of 17 satellite on orbit test, the test results may be open next week.
This is the first time that the device has been tested in the near earth orbit after NASA announced that the Emdrive system measured the thrust in the laboratory vacuum.
Posted on 2016-12-15

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Offline Bob012345

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I would just like to note that special care must be taken to avoid confusion between the reaction force (which is a "real" force exerted *by* an object to counteract the force exerted upon the object) and the inertial force, which is a fictitious force imagined to be acting *upon* the object.

This must be Zeno's Law of Motion! If the total force acting on the body were zero, the body wouldn't accelerate. This concept is a subtle one to explain what it looks like if you are that body and your relative velocity to yourself is of course zero but in reality, it's confusing and unnecessary. Mass is a measure of inertia. If inertia were zero acceleration would be infinite for any force applied. Newton is enough.  :)

Offline WarpTech

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I would just like to note that special care must be taken to avoid confusion between the reaction force (which is a "real" force exerted *by* an object to counteract the force exerted upon the object) and the inertial force, which is a fictitious force imagined to be acting *upon* the object.

This must be Zeno's Law of Motion! If the total force acting on the body were zero, the body wouldn't accelerate. This concept is a subtle one to explain what it looks like if you are that body and your relative velocity to yourself is of course zero but in reality, it's confusing and unnecessary. Mass is a measure of inertia. If inertia were zero acceleration would be infinite for any force applied. Newton is enough.  :)

I have to agree with you. This image is confusing to the extreme. I was taught, if I push on a wall, there is an equal and opposite force acting on my hand, and the wall does not move. The amount of "work" done is zero. Work is NET Force x Distance and in this case, the NET force is zero.

Alternatively, if I am exerting a force on an object that is free to accelerate, the NET force cannot be zero because work is being done to accelerate it. Work will still be the NET Force x Distance, so therefore the NET force is equal to the Applied force, and it is not zero.

Offline Rodal

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...If the total force acting on the body were zero, the body wouldn't accelerate. This concept is a subtle one to explain what it looks like if you are that body and your relative velocity to yourself is of course zero but in reality, it's confusing and unnecessary. Mass is a measure of inertia. If inertia were zero acceleration would be infinite for any force applied. Newton is enough.  :)
D'Alembert's principle is routinely used in Aerospace Engineering for dynamic design of aerospace vehicles.  It was used in the Apollo program and continues to be used to this date in most Finite Element Analysis programs, including NASTRAN, ANSYS etc. to calculate dynamics of multi-degree of freedom deformable bodies.  ;)

That's how NASTRAN analyzed dynamics problems.

I get the impression that not everybody is well exposed to D'Alembert's principle and why it is used.  (Your comparison with Zeno is not pertinent.)  People that have been involved with dynamic analysis of actual (multi-degree of freedom, deformable) aerospace vehicles may appreciate the usefulness of D'Alembert's principle, it is not a competitor to Newton's analysis, it just facilitates the analysis in a similar fashion as Lagrange's formulation helps to analyze general problems. 

If one is not going to be involved in the actual analysis of dynamics of aerospace vehicles, and just discusses simple lumped mass, single degree of freedom problems, then Newton's formulation suffices, and D'Alembert's principle may appear as unnecessary.   Yes, for Physics 1.00, one starts with Newton's formulation, but for further dynamics classes one progresses to the use of D'Alembert's principle, and variational principles for very good reasons  ;).

See https://www.colorado.edu/engineering/CAS/KCPark.d/KCParkHome.d/lectures.d/usnccm2007.pdf  whether that helps (I did not go to Colorado, this is just the first thing that came in google  :) )

Same reason why Lagrange's formulation is useful.
To appreciate the usefulness of Lagrange's formulation one has to analyze multi-degree of freedom general problems.  Otherwise Lagrange's formulation may look like overkill.

I agree that to understand that Shawyer's analysis is flawed, D'Alembert's principle may be overkill.  Just Newton's law is enough.
« Last Edit: 11/10/2017 05:42 pm by Rodal »

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