Author Topic: EM Drive Developments Thread 1  (Read 795967 times)

Offline Rodal

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Re: EM Drive Developments
« Reply #1320 on: 10/03/2014 02:44 PM »
EDIT: Let's call the point at which constitutive statements are attached to Woodward's theory, a "W theory," such that "W theory" stands for the whole theory including any attached constitutive statement.

So even if one were to accept Woodward's theory on a theoretical basis, at the point that Woodward's theory becomes a constitutive theory, it does not follow that actual materials would have to behave as prescribed by "W theory" with a Buldrini factor >0.  I think that Buldrini understood this and that's why he allowed his "fudge factors" to range all the way from zero (for a value of zero there is no Woodward effect).

Only experiments would be able to show whether they do or do not.  However, if one were to accept  "W theory"  on a theoretical basis, and materials in nature are found not to obey it, the interesting possibility could still be raised whether such a  "W theory" material could be eventually be man-made (to allow propellant-less drives) as for example now we are able to make isotropic materials with very negative Poisson's ratio that don't exist in nature.  (The experiments that are trying to verify Woodward's effect now are limiting themselves to materials that are presently available for other uses, not materials that have been engineered by man first at the nano level and eventually at the molecular level with the only intent to maximize such a "W theory" effect. )
I think what you're saying is true, but it is not Woodward's theory that all bulk matter stores delta mass when deformed.  That's undergrad physical chemistry.  Woodward chose shape change materials since they have very large changes in internal energy--the largest I know of.  So I don't think it's fair to say this is a constituative part of his theory.  His theory only stipulates that if one changes the internal energy of a mass while accelerating it, you will get this 2w fluctuation, or Mach Effect.
So much semantic discussion about attaching a name to a theory!

All theories are "built on the shoulders of giants".  No recent (during the past few hundreds years) theory attached to a name has been built solely by the person whose name is attached to it.  Einstein's General Relativity uses non-Euclidean geometry and the tools of Levi-Civita, Riemann, and many others.  This line of complaining would be like somebody saying that Einstein's theory involves a particular kind of non-Euclidean geometry, and you saying, no that was part of previous knowledge.

If the total theory to solve a problem contains a constitutive assumption, that's part of the total theory to analyze a problem, even if that part came from existing knowledge.  Concerning the Mach effect, the theory uses Sciama's 1953 derivation as a foundation, so one may even call it Woodward/Sciama/Mach.

Again, since there is so much concern in this thread about what a given total theory should be called, I will strive from now on to use the term "W theory".

__________
EDIT: I much prefer this thread when it contains the tools of engineers and scientists:  numbers, equations, spreadsheets, graphs, images and links.  Instead of words, discussions about history, or discussions about name attribution. 

« Last Edit: 10/03/2014 03:06 PM by Rodal »

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1321 on: 10/03/2014 02:48 PM »
[Woodward] is not questioning  mass that you can measure during low speeds. His theory try to explain mass increase during speed close to light speed and possibility manipulate increase mass/inertia at these moments.

That's my understanding as well.

I believe that he admits to not being able to accelerate an ion to these speeds, and is now attempting to accelerate the lattice at these speeds.

Again, unless I'm confused, this paper claims that "Approximately 30-50 micro-Newtons of thrust were recorded from an electric propulsion test article consisting primarily of a radio frequency (RF) resonant cavity excited at approximately 935 megahertz". 

They offer this tentative explanation for how the device works:  "Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma".

This is a different operating principle than the one thought to be operative by Woddward.

Again, unless I'm confused, bewildered, and a host of other terms, including un-read, the thread topic has included these two theories of operation on a propellantless drive.

Nobody has yet explained how either of these devices actually work, other than the obvious; that the devices covert electrical energy to forward momentum, which is the only thing that the term "electric propulsion" can mean.
John, I don't want to have a conflict with you here.  I do feel though I ought to point out that even your questions are wrong.  Fact is, what Woodward proposes does work at low velocities.  It's not a relativistic mechanism at all.  And your posts about chemical bonds and accelerating the lattice, all based on terrible misunderstandings.  You are correct that Woodward's theory has nothing to do with Shawyer's model, or White's QVF model.  These are just alternative models for explaining this propellantless thrust.  However, you don't seem to be able to identify which comments refer to which model or theory.

This is why I suggest you read the book, because there is no value added by posting time and again from ignorance.  You're just posting to be posting.  Almost everything you're writing is wrong.  Even your high school chemistry is wrong.  So why are you posting?  Read the book.

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1322 on: 10/03/2014 02:53 PM »
Nobody has yet explained how either of these devices actually work, other than the obvious; that the devices covert electrical energy to forward momentum, which is the only thing that the term "electric propulsion" can mean.

in simple terms, Woodwards device works by using these mass fluctuations... pull when it´s light, push when it´s heavier. That is how I understand it.
This is correct.  I would note too, that it is not really accurate to say the device converts electrical into mechanical energy, as a transducer.  Rather, it controls the flow of the gravinertial flux into and out of the active mass, and this can be used to produce mechanical force.  So really the device is a gravinertial transistor.   It is not converting one energy form into another but rather, controlling the flow of what gives matter its mass and inertia.

Offline Mulletron

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Re: EM Drive Developments
« Reply #1323 on: 10/03/2014 03:39 PM »
Ok, likely an oversimplification on my part, but;

If a solar sail can work via reflected photons, could not another drive, using a pure electron stream, (which has mass) also work?

Pointing a basic idea out here, mass is being expended as a propellent whether that mass be of a chemical, nuclear, ionic or even an electron stream. You have to have SOMETHING to generate the power. be it a generator or solar panels.  In the case of Solar panels, the electrons are being generated via the energy produced via capturing and converting photons into electrical power.  (Not very effecient, granted, but mass is being exchanged, even is on an almost quantum level).

Like I said, likely a vast oversimplification, but according to basic physics, it should work.

In the case as presented, it sort of appears that the electron stream, may be being concentrated and accelerated to increse their effective mass.

Assuming that you could either focus, or effectively "Laser" focus the electron stream, there should be some sort of thrust in the opposing direction, even if it were in the millinewtons of force. Basic Newtonian Physics, "Every Action has an equal and opposite reaction."

Yeah it does work but it is several orders of magnitude less of an effect than the already very small effect from the emdrive test campaign. I remember seeing this before.
Challenge your preconceptions, or they will challenge you. - Velik

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1324 on: 10/03/2014 03:41 PM »
All theories are "built on the shoulders of giants".  No recent (during the past few hundreds years) theory attached to a name has been built solely by the person whose name is attached to it.  Einstein's General Relativity uses non-Euclidean geometry and the tools of Levi-Civita, Riemann, and many others.  This line of complaining would be like somebody saying that Einstein's theory involves a particular kind of non-Euclidean geometry, and you saying, no that was part of previous knowledge.

If the total theory to solve a problem contains a constitutive assumption, that's part of the total theory to analyze a problem, even if that part came from existing knowledge.  Concerning the Mach effect, the theory uses Sciama's 1953 derivation as a foundation, so one may even call it Woodward/Sciama/Mach.

Again, since there is so much concern in this thread about what a given total theory should be called, I will strive from now on to use the term "W theory".
Woodward has always gone to great lengths to point out his work comes directly from Sciama.  I think he sees himself as following Sciama's lead and he points out others as well.  This is why you need to read the book.  If you're like me, you get plenty enough time sitting in front of the screen here, and a bit of paper in one's hand, a soft couch and something to snack on is a welcome break.  And Woodward really is an excellent writer.  It's a pleasure to read him, unlike so many others in the field.

IMHO, Woodward's work is best referred to as "M-E theory" or "Mach Effect physics" since at its core, it is this ability to generate what Woodward has termed "Mach Effects" that is key.  He has always chafed at attempts to connect his name with his theory, as one finds on wikipedia.

Offline JohnFornaro

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Re: EM Drive Developments
« Reply #1325 on: 10/03/2014 03:41 PM »
No recent ... theory attached to a name has been built solely by the person whose name is attached to it.

Obviously, you are not familiar with my theory, now generally accepted, that everybody's an idiot except for me.
Sometimes I just flat out don't get it.

Offline D_Dom

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Re: EM Drive Developments
« Reply #1326 on: 10/03/2014 05:08 PM »
when did you get promoted to general?

Space is not merely a matter of life or death, it is considerably more important than that!

Offline Mulletron

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Re: EM Drive Developments
« Reply #1327 on: 10/03/2014 05:12 PM »

I wanted to throw it out there that as I understand it, the casimir effect between the plates equates to a small negative mass energy by virtue of all other modes being excluded. This is the difference of potential, similar to volts. The sign of casimir energy doesn't denote positive/negative energy. It is negative with respect to the universe nomatter the sign. Another way to think of it is possible hole flow in electronics. Am I right?

Well, count me with Jaffe at MIT:   http://cua.mit.edu/8.422/Reading%20Material/Jaffe2005_Casimir.pdf

<<In discussions of the cosmological constant, the Casimir effect is often invoked as decisive evidence
that the zero-point energies of quantum fields are ‘‘real.’’ On the contrary, Casimir effects can be
formulated and Casimir forces can be computed without reference to zero-point energies.
They are
relativistic, quantum forces between charges and currents. The Casimir force (per unit area) between
parallel plates vanishes as , the fine structure constant, goes to zero>>

I do not think that the Casimir force is related to negative mass.  The "all other modes being excluded" explanation is Casimir's.  It works for flat plates but it doesn't work for several other geometries.

Yeah I'm hearing you and I'm enjoying the discussion but I have to add that if the fine structure constant were to approach 0, electromagnetism itself would collapse. The fine structure constant is dependent of the permeability and permittivity of free space and C. C depends on vacuum permittivity and vacuum permeability. Thus free space has its own impedance. The QED vacuum is diamagnetic. This:

http://www.mpl.mpg.de/en/institute/news/news/article/a-link-between-particle-physics-and-maxwells-equations.html

Whether speaking classically or quantumly, they are EXACTLY the same thing described in different ways. QM just adds probability and locality to the mix. And yes, quoting the paper "Casimir effects can be
formulated and Casimir forces can be computed without reference to zero-point energies. They are
relativistic, quantum forces between charges and currents," is exactly right. The vacuum fields/particles are exactly the same as the "real" ones, they interact the same, no difference whatsoever. The only difference is their probability and ubiquity because of that. The are near the ground state of the universe and consequently have a very low probability of being detected except by some of the modes like the ones near the compton wavelength of electrons which slightly influence their energy levels. Other effects too. A fleeting particle with a low probability is the same as saying a nano degree of a wave. The fine structure constant would never be 0 and the paper shows a dependence between Casimir and the fine structure constant. The fine structure constant is quantum anyway, so basically they are further marrying classical and quantum. Who is to say the casimir effect can't be the result of BOTH classical and quantum boundary conditions. It seems unwise to limit it in such a way described.

I want to clarify that negative mass doesn't necessarily mean <0 mass, which would be <0 energy, which would be <absolute zero temperature. Just negative with respect to the established vacuum energy of the universe.

Edit:
Observation: Since free space is a diamagnetic dielectric, would a frequency dependent complex permittivity arise? I can't find any evidence it does. The spectral distribution of the CMB which peaks around 160ghz sure looks like that of plot.
« Last Edit: 10/03/2014 05:43 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1328 on: 10/03/2014 05:32 PM »
The vacuum fields/particles are exactly the same as the "real" ones, they interact the same, no difference whatsoever.
I'm sorry, but this is not true.  Virtual particles do not gravitate.  If the proposed virtual particles did gravitate, their mass added to our universe would have prevented its expansion from the start, and would currently cause it to collapse.  This is why most physicists don't buy the ZPF and QVF conjectures, because they're based upon zero mass virtual particles but then expect those particles to transfer momentum, which is a violation of EEP as stated above.

Virtual particles are just an accounting mechanism.  There' no reason to suppose they exist at all and Casimir effect can be explained without them.  Indeed it has been for decades.

However, if you want the primary text for ZPF physics written by true believers, you want this:

http://www.amazon.com/Frontiers-Propulsion-Progress-Astronautics-Aeronautics/dp/1563479567/ref=sr_1_1?ie=UTF8&qid=1412356998&sr=8-1&keywords=AIAA+Davis+Millis






Offline Rodal

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Re: EM Drive Developments
« Reply #1329 on: 10/03/2014 05:35 PM »

I wanted to throw it out there that as I understand it, the casimir effect between the plates equates to a small negative mass energy by virtue of all other modes being excluded. This is the difference of potential, similar to volts. The sign of casimir energy doesn't denote positive/negative energy. It is negative with respect to the universe nomatter the sign. Another way to think of it is possible hole flow in electronics. Am I right?

Well, count me with Jaffe at MIT:   http://cua.mit.edu/8.422/Reading%20Material/Jaffe2005_Casimir.pdf

<<In discussions of the cosmological constant, the Casimir effect is often invoked as decisive evidence
that the zero-point energies of quantum fields are ‘‘real.’’ On the contrary, Casimir effects can be
formulated and Casimir forces can be computed without reference to zero-point energies.
They are
relativistic, quantum forces between charges and currents. The Casimir force (per unit area) between
parallel plates vanishes as , the fine structure constant, goes to zero>>

I do not think that the Casimir force is related to negative mass.  The "all other modes being excluded" explanation is Casimir's.  It works for flat plates but it doesn't work for several other geometries.

Yeah I'm hearing you and I'm enjoying the discussion but I have to add that if the fine structure constant were to approach 0, electromagnetism itself would collapse. The fine structure constant is dependent of the permeability and permittivity of free space and C. C depends on vacuum permittivity and vacuum permeability. Thus free space has its own impedance. The QED vacuum is diamagnetic. This:

http://www.mpl.mpg.de/en/institute/news/news/article/a-link-between-particle-physics-and-maxwells-equations.html

Whether speaking classically or quantumly, they are EXACTLY the same thing described in different ways. QM just adds probability and locality to the mix. And yes, quoting the paper "Casimir effects can be
formulated and Casimir forces can be computed without reference to zero-point energies. They are
relativistic, quantum forces between charges and currents," is exactly right. The vacuum fields/particles are exactly the same as the "real" ones, they interact the same, no difference whatsoever. The only difference is their probability and ubiquity because of that. The are near the ground state of the universe and consequently have a very low probability of being detected except by some of the modes like the ones near the compton wavelength of electrons which slightly influence their energy levels. Other effects too. A fleeting particle with a low probability is the same as saying a nano degree of a wave. The fine structure constant would never be 0 and the paper shows a dependence between Casimir and the fine structure constant. The fine structure constant is quantum anyway, so basically they are further marrying classical and quantum. Who is to say the casimir effect can't be the result of BOTH classical and quantum boundary conditions. It seems unwise to limit it in such a way described.

I want to clarify that negative mass doesn't necessarily mean <0 mass, which would be <0 energy, which would be <absolute zero temperature. Just negative with respect to the established vacuum energy of the universe.

Bondi's arguments (see http://forum.nasaspaceflight.com/index.php?topic=29276.msg1265704#msg1265704 ) persuade me that it is extremely unlikely for us to find (or contain if artificially produced) negative mass for the reasons given by Bondi (negative mass would quickly escape off into the universe). 

I have the view that the Casimir force is mostly an engineering annoyance in constructing nanodevices but not something that will be useful for space propulsion.

But as Keynes said, my opinions are subject to change as new data becomes available  :)

Offline Mulletron

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Re: EM Drive Developments
« Reply #1330 on: 10/03/2014 05:44 PM »
The vacuum fields/particles are exactly the same as the "real" ones, they interact the same, no difference whatsoever.
I'm sorry, but this is not true.  Virtual particles do not gravitate.  If the proposed virtual particles did gravitate, their mass added to our universe would have prevented its expansion from the start, and would currently cause it to collapse.  This is why most physicists don't buy the ZPF and QVF conjectures, because they're based upon zero mass virtual particles but then expect those particles to transfer momentum, which is a violation of EEP as stated above.

Virtual particles are just an accounting mechanism.  There' no reason to suppose they exist at all and Casimir effect can be explained without them.  Indeed it has been for decades.

However, if you want the primary text for ZPF physics written by true believers, you want this:

http://www.amazon.com/Frontiers-Propulsion-Progress-Astronautics-Aeronautics/dp/1563479567/ref=sr_1_1?ie=UTF8&qid=1412356998&sr=8-1&keywords=AIAA+Davis+Millis


Yes you are right about gravitation and thanks. I forgot that. It is a good thing they don't gravitate or space time would be curved instead of flat. When you look at a universe full of quickly appearing and annihilating particle pairs/also viewed as waves out of phase across all phases, the net effect is 0 energy/0 mass for any given instant. But if you take a weighted average of all this happening, you arise a a very small mass energy contribution, not 10^120 too much warping space time. It is like white noise with values above and below 0db but the QV, specifically the electromagnetic QV, deals in charge and energy.

Edit more thoughts.

Curious why it is repulsive vice attractive. Could it be a consequence of the shape of the universe? More casimir effects? Given the observed dipole moment of the CMB, maybe? I read other reasons too.
« Last Edit: 10/03/2014 05:51 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1331 on: 10/03/2014 06:00 PM »
Bondi's arguments (see http://forum.nasaspaceflight.com/index.php?topic=29276.msg1265704#msg1265704 ) persuade me that it is extremely unlikely for us to find (or contain if artificially produced) negative mass for the reasons given by Bondi (negative mass would quickly escape off into the universe).
So far as I understand it, this is an error that was corrected by Robert Forward.  To state again, any permanently negative mass would experience a reverse gravity force away from all normal mass bodies, but it would respond backward to that force because of its reverse inertia.

This is surprisingly complex, but the best analysis came not from Herman Bondi but Robert Forward.  You'll find a good treatment of it here, and note the link to Forward's "Diametric Drive":

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

"Although no particles are known to have negative mass, physicists (primarily Hermann Bondi and Robert L. Forward) have been able to describe some of the anticipated properties such particles may have. Assuming that all three concepts of mass are equivalent the gravitational interactions between masses of arbitrary sign can be explored.

For two positive masses, nothing changes and there is a pull on each other causing an attraction. Two negative masses would produce a pull on one another, but would repel because of their negative inertial masses. For different signs there is a push that repels the positive mass but attracts the negative mass.

Bondi pointed out that two objects of equal and opposite mass would produce a constant acceleration of the system towards the positive-mass object.[citation needed] However, the total mass, momentum and energy of the system would remain 0.

This behavior is completely inconsistent with a common-sense approach and the expected behaviour of 'normal' matter; but is completely mathematically consistent and introduces no violation of conservation of momentum or energy. If the masses are equal in magnitude but opposite in sign, then the momentum of the system remains zero if they both travel together and accelerate together, no matter what their speed:


And equivalently for the kinetic energy :


Forward extended Bondi's analysis to additional cases, and showed that even if the two masses m(-) and m(+) are not the same, the conservation laws remain unbroken. This is true even when relativistic effects are considered, so long as inertial mass, not rest mass, is equal to gravitational mass.

This behaviour can produce bizarre results: for instance, a gas containing a mixture of positive and negative matter particles will have the positive matter portion increase in temperature without bound. However, the negative matter portion gains negative temperature at the same rate, again balancing out. Geoffrey A. Landis pointed out other implications of Forward's analysis,[2] including noting that although negative mass particles would repel each other gravitationally, the electrostatic force would be attractive for like-charges and repulsive for opposite charges.

Forward used the properties of negative-mass matter to create the diametric drive, a design for spacecraft propulsion using negative mass that requires no energy input and no reaction mass to achieve arbitrarily high acceleration.

Forward also coined a term, "nullification" to describe what happens when ordinary matter and negative matter meet: they are expected to be able to "cancel-out" or "nullify" each other's existence. An interaction between equal quantities of positive and negative mass matter would release no energy, but because the only configuration of such particles that has zero momentum (both particles moving with the same velocity in the same direction) does not produce a collision, all such interactions would leave a surplus of momentum, which is classically forbidden."

Also note that although Woodward is saying electrons have this negative mass, they are "dressed" such that they have positive mass.  To understand what dressing and undressing is and the history behind the need to dress elementary particles, read Woodward chapter 7.
« Last Edit: 10/03/2014 06:05 PM by Ron Stahl »

Offline Rodal

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Re: EM Drive Developments
« Reply #1332 on: 10/03/2014 06:14 PM »

This is surprisingly complex, but the best analysis came not from Herman Bondi but Robert Forward.  You'll find a good treatment of it here, and note the link to Forward's "Diametric Drive":

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

Bondi's analysis is correct. 
« Last Edit: 10/03/2014 06:43 PM by Rodal »

Offline birchoff

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Re: EM Drive Developments
« Reply #1333 on: 10/03/2014 06:32 PM »

This is surprisingly complex, but the best analysis came not from Herman Bondi but Robert Forward.  You'll find a good treatment of it here, and note the link to Forward's "Diametric Drive":

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

Bondi's analysis is actually the correct one. 

Anybody can write stuff in Wikipedia. 

As an example, I wrote a whole article, including the mathematical analyses plots here  :)   :  http://en.wikipedia.org/wiki/Beta_distribution

really after that lengthy counter argument we get this short response???

A side from the questionable reference, what makes Forwards analysis incorrect but Bondi's correct?
« Last Edit: 10/03/2014 06:33 PM by birchoff »

Offline Rodal

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Re: EM Drive Developments
« Reply #1334 on: 10/03/2014 06:42 PM »
really after that lengthy counter argument we get this short response???
I edited as follows "Bondi's analysis is correct."

« Last Edit: 10/03/2014 06:53 PM by Rodal »

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1335 on: 10/03/2014 06:53 PM »
Well if we get someone to generate enough negative mass for a diametric drive, your opinion here will matter.  ;)  But I did explain to you the error most people make.  They forget that the mass responds backward to the force on it.  Negative mass gravitates away from or experiences a gravitational force away from normal mass, but moves toward it because of its negative inertia.

Offline Rodal

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Re: EM Drive Developments
« Reply #1336 on: 10/03/2014 07:03 PM »
Would like to be able to use equations rather than words.  :)

HELP: Is it possible to write equations in this forum? Is there a palette with mathematical symbols one can use?  All I see are the symbols for bold, italics, underline, subscripts, superscripts, etc.
« Last Edit: 10/03/2014 07:21 PM by Rodal »

Offline Notsosureofit

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Re: EM Drive Developments
« Reply #1337 on: 10/03/2014 07:39 PM »
"Images can be embedded into posts. "

SMF has the ability to recognize and parse HTML or XHTML code in board's description. Just add something like this to your description:
Code: [Select]

<img src="mypic.gif" width="70" height="17" alt="" />

Where:

    img="mypic.gif" - is the name of the image. If it is not located in the forum's base directory, it will be necessary to include the path to it (i.e. img="./Themes/default/images/mypic.gif");
    width="70" - is the width in pixels of the image.
    height="17" - is the height in pixels of the image.
    alt="" - is an alternative text to display if, for any reason, the image does not load correctly in visitors' browser. If the image has no real utility except aesthetics, it can be left empty. Otherwise it would be appropriate to explain in one word or two what the image represents.
« Last Edit: 10/03/2014 07:43 PM by Notsosureofit »

Offline Ron Stahl

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Re: EM Drive Developments
« Reply #1338 on: 10/03/2014 08:21 PM »
Lower right hand corner of the first page here, you can see the primary source material for this dating back 1/4 century:

http://arc.aiaa.org/doi/abs/10.2514/3.23219?journalCode=jpp

Obviously the negative mass is chasing the positive mass.  BTW, in case it escaped anyone's notice, for this to work, you need to connect the two masses rigidly, and the force exerted will be gravitic, so you need VERY large masses for this to be practical.  Woodward's impulse engine seems to me much more viable in the practical sense and because it too takes advantage of the self-acceleration of negative mass, it can be fantastically efficient.

MET's driven past dm=m tap into this negative mass contribution.

Offline Rodal

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Re: EM Drive Developments
« Reply #1339 on: 10/03/2014 08:27 PM »
Lower right hand corner of the first page here, you can see the primary source material for this dating back 1/4 century:

http://arc.aiaa.org/doi/abs/10.2514/3.23219?journalCode=jpp

Obviously the negative mass is chasing the positive mass.  BTW, in case it escaped anyone's notice, for this to work, you need to connect the two masses rigidly, and the force exerted will be gravitic, so you need VERY large masses for this to be practical.  Woodward's impulse engine seems to me much more viable in the practical sense and because it too takes advantage of the self-acceleration of negative mass, it can be fantastically efficient.

MET's driven past dm=m tap into this negative mass contribution.

Where does Forward contradict Bondi?  As I started reading this Forward is actually quoting Bondi.

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