### Author Topic: EM Drive Developments Thread 1  (Read 765855 times)

#### Rodal

• Senior Member
• Posts: 5845
• USA
• Liked: 5927
• Likes Given: 5270
##### Re: EM Drive Developments
« Reply #2460 on: 10/22/2014 08:34 PM »
And I just verified that Paul March wrote that the supported mass was a maximum of 25 lbm.  That is 11.3398 kgm

The way NASA set-up the experiment "with all that stuff hanging out there" from those 1.5"x1.5" Faztek beams figuring out the rotational mass moment of inertia is also non-trivial.   It is also non-isotropic as it is very different in different orientations of swinging of the inverted pendulum.

Mass moment of inertia not given and very difficult to figure out.  Wonder whether they calculated the inverted torsional pendulum frequencies.  Wonder whether they have a measured  inverted torsional pendulum frequency spectrum for their inverted pendulum with everything set-up (if they do, it was not shown in their report).
« Last Edit: 10/22/2014 08:55 PM by Rodal »

#### Rodal

• Senior Member
• Posts: 5845
• USA
• Liked: 5927
• Likes Given: 5270
##### Re: EM Drive Developments
« Reply #2461 on: 10/22/2014 09:00 PM »
What you are saying is that these EM thruster devices need to be checked with a smoke trails, like air flow in a wind tunnel is highlighted. Hold a lighted punk stick next to it and turn the device on.

Wouldn't their be some time delay between power on/off and thrust on and off?
Have to think about what would a time constant involved in delay depend on.  The electric effect is practically instantaneous.  Momentum transfer has to do with hydrodynamics.  There is no heat capacity and thermal difussivity involved like in a thermal effect.  Time constant could depend on Reynolds number, hence viscosity, but viscosity of air is low. Also, speed of sound in air is 343 metres per second, which is pretty fast for these considerations.

What is the time delay for the craft shown in this video?  Seems to take off in an impulsive manner:

Prof. Barrett and Masuyama (MIT) wrote:  <<An ionic wind results from the net momentum gain in a mostly neutral fluid through momentum-transfer collisions with ions in an electric field. When a voltage in excess of the corona inception voltage (V o) is applied across two electrodes with different radii of curvature (re≪rc), a non-uniform electric field with the largest magnitude in the vicinity of the smaller emitter electrode ignites a corona discharge that emits an ion stream. The ions are transported across the interelectrode gap at an average drift velocity vD=μE, where μ is the ion mobility and E is the electric field magnitude, the result of a balance between the electrostatic force owing to the field and the drag force owing to the collisions. The ions are collected at the collector electrode and do not contribute to thrust, but the neutrals that gained energy in the collisions escape the system with net momentum along x, the direction from the emitter towards the collector.>>

So, we know that the average drift velocity is vD=μE  where μ is the ion mobility and E is the electric field magnitude.

The time constant can be figured out from here:  http://en.wikipedia.org/wiki/Electrical_mobility

μ=(q/kT) D

where D is the diffusion coefficient, which is given by the momentum transfer mean free path and the momentum transfer collision frequency.  These are difficult to estimate.

This paper http://iopscience.iop.org/0370-1328/85/6/327 gives

<<The mobility of positive ions in dry air, which is constant in the range E/p = 45-70 v cm-1 torr-1 and is equal to 2.2 × 10^3 cm2 v-1 sec-1 (at 1 torr and at 20 °c), gradually decreases at higher E/p values. In water vapour the mobility of positive ions was constant over the measured range E/p = 50-90 v cm-1 torr-1 and is equal to 0.61 × 10^3 cm2 v-1 sec-1 (at 20 °c and at 1 torr). In humid air the value of mobility is lower than the value calculated from Blanc's law. This suggests a clustering of ions.>>

EDIT: I have checked vs other references and this reference's abstract is in error, it should read 2.2  cm^2 v-1 sec-1 instead

This book (Ion Mobility Spectrometry, Second Edition, By G.A. Eiceman, Z. Karpas) has it right:  http://goo.gl/0MkCMC
« Last Edit: 10/23/2014 02:13 AM by Rodal »

#### Rodal

• Senior Member
• Posts: 5845
• USA
• Liked: 5927
• Likes Given: 5270
##### Re: EM Drive Developments
« Reply #2462 on: 10/22/2014 09:32 PM »
So, assuming the Electric Field in the microwave EM Drive to be 2000 Volts/m  I get:

The average drift velocity for which ions are transported across the inter-electrode gap:

average drift velocity = ((2.2)/(100 cm/m)^2)(cm^2/(Volt*s))*2000 Volts/m
= 0.44 m/sec = 17.3 inches / sec = 86.6 ft/min = 0.98 miles/hr

And for 20,000 Volts/m  I get:

average drift velocity = ((2.2)/(100 cm/m)^2)(cm^2/(Volt*s))*20,000 Volts/m
= 4.4 m/sec = 173 inches / sec = 866 ft/min = 9.8 miles/hr

using the maximum, electric field calculated by COMSOL at the Teflon dielectric for the Cannae drive, 47,000 Volts/m,  I get:

average drift velocity = ((2.2)/(100 cm/m)^2)(cm^2/(Volt*s))*47,000 Volts/m
= 10.3 m/sec = 407 inches / sec = 2035 ft/min = 23 miles/hr

So, the average drift velocity, ranges from a slow breeze like natural convection to a strong wind as from a fan forced convection.

Ionic wind being due to the Electric Field, also explains why the measured thrust was (according to both NASA and China) due to the (TE) transverse electric modes of cavity oscillation (rather than the magnetic modes), where the electric field circulates around the circumferential periphery of the gap between the flat base of the cone and the round surface of the cone.  It is in the circumferential gap around the base (between the base and the cone) that the corona discharge may be taking place.  Also where the protruding bolts holding the base are located.

Magnetic field (B) in blue  Electric Field in red
« Last Edit: 10/23/2014 01:47 AM by Rodal »

#### Rodal

• Senior Member
• Posts: 5845
• USA
• Liked: 5927
• Likes Given: 5270
##### Re: EM Drive Developments
« Reply #2463 on: 10/22/2014 09:57 PM »
It is interesting that there have been confusions about non-classical physics [coupling between electromagnetism and gravity] to explain the ionic wind:

Prof. Barrett (MIT) writes:

<<Brown initially attributed the observed thrust force to a coupling between electromagnetism
and gravity. Despite the faulty understanding of the physics, Brown had conceived of the ‘lifter’
design by the 1950s, consisting of a thin wire emitter separated from an aluminium foil collector
with a lightweight non-conducting frame [8]. The concept of ionic wind was associated with EHD
thrust as early as 1961, when Cheng’s [9] one-dimensional model predicted a thrust that varied as
the square of pressure. Christenson & Moller [4] developed an analytical model starting from the
Navier–Stokes equations, whose predictions were confirmed by experiments using pointed pin
emitters. The current density was seen to vary as j ∝ V(V − Vo), in agreement with the current
output for corona discharges.>>
« Last Edit: 10/22/2014 09:58 PM by Rodal »

#### zen-in

• Full Member
• Posts: 531
• California
• Liked: 468
• Likes Given: 365
##### Re: EM Drive Developments
« Reply #2464 on: 10/22/2014 10:05 PM »
The time delay is not noticeable. I don't know if the time delay difference between this device and the EM thrusters could be detected. I don't think it can be with the data we have available to us.

Actually the time delay is visible in these two plots of thrust data vs time.   The first one is from Shawyer's 2008 paper.   His 2013 and 2014 IAC papers don't have this kind of raw data.   Both the up and down thrust roughly follow an exponential rise after power is applied and there is continued acceleration after the power is turned off.

The second plot is from the JSC paper - Brady, White, et al.  This also has a roughly exponential rise and continued thrust after RF power is turned off until the Cal pulse wipes it out.

Both experiments have a thermal effect signature.

Yes, some kind of a delay but not thermal for NASA Eagleworks. Around page 30 to 40 of this thread I calculated the thermal time delay based on the thermal diffusivity (thermal capacity and thermal conductivity) for the NASA Eagleworks experiments and ruled out the time delay and time decay as due to thermal effects because the Fourier time due to thermal effects is much longer than the ~2 second delay in the NASA Eagleworks experiments in the pulse rise from the baseline.

The exponentially decaying rise after the initial 2 sec pulse may indeed be a thermal effect.  Maybe related to their "baseline problem due to the magnetic damper interaction with the power cable..."

Ionic wind time delay ?

Paul March had also though about thermal effects and wrote about it.  It is interesting that while these researchers can rule out thermal effects (based on standard heat transfer texts) the theory of ionic wind has not been written until recently.  Perhaps nobody has computed or ruled out ionic wind, really...

It is next to impossible to predict thermal effects if you don't have the device in hand.   There are too many variables and wrong assumptions to be made.   I'm not criticizing your abilities but I think there is just not enough information if you don't have the device and have not done some experiments and data collection to start with.   The thrust waveform does look like a thermal effect.   I would be interested to see what happens if they attached a 25 Watt heating pad to the inside surface of the cone section and applied a 30 Sec power pulse.  The entire cone could just be heating the air around it.  The cone angle appears to be about 30 degrees so about half the momentum of any heated air would generated thrust in the same direction as is claimed for em effects.

I also doubt the conical waveguide theory, which is also based on simulations.   I find it surprising the simulation agrees so closely with their measured result, given the rough construction techniques used.  This science of conical cavity appears to be only known by em-drive researchers, despite the wide application of microwave technology with thousands of companies worldwide actively researching new technologies.   A Google search for "conical cavity" only finds Egan's page which while interesting also disputes the notion that thrust can be generated.   If a search for "cold fusion" were done there would be thousands of hits.

#### birchoff

• Full Member
• Posts: 267
• United States
• Liked: 122
• Likes Given: 95
##### Re: EM Drive Developments
« Reply #2465 on: 10/23/2014 12:02 AM »
Here is the PDF mentioned above.

http://www.emdrive.com/iac2014presentation.pdf

Is there a paper with more details to be published ?
"4 independent organisations, in 3 different countries" : what organisations ? with what kind of balance ? Someone present at the conference to take notes and give some context ?

It was an oral presentation. In addition I am not aware of any video from the conference. that said just looking at the publicly available information the 4 independent organizations could be. SPR (Shawyer's company), The chinese, NASA, Cannae. IF that is correct then the three different countries would be UK, China, and US.

#### birchoff

• Full Member
• Posts: 267
• United States
• Liked: 122
• Likes Given: 95
##### Re: EM Drive Developments
« Reply #2466 on: 10/23/2014 12:52 AM »
...
I wish we would get a Cavendish-type measurement (as performed by Brito Marini and Galian to nullify the MET-type drive) at John Hopkins as soon as possible.
...

This is not correct. What they tested was an MLT type drive not a MET type drive.

#### Rodal

• Senior Member
• Posts: 5845
• USA
• Liked: 5927
• Likes Given: 5270
##### Re: EM Drive Developments
« Reply #2467 on: 10/23/2014 01:32 AM »
.....

This is not correct. What they tested was an MLT type drive not a MET type drive.

Thank you for catching that mistake.  I went back and I corrected it.
« Last Edit: 10/23/2014 01:40 AM by Rodal »

#### ThinkerX

• Full Member
• Posts: 303
• Alaska
• Liked: 113
• Likes Given: 59
##### Re: EM Drive Developments
« Reply #2468 on: 10/23/2014 02:44 AM »
Am I to understand this 'Ionic Wind' explanation means this device would not produce thrust in a vacuum - or in space?

#### Rodal

• Senior Member
• Posts: 5845
• USA
• Liked: 5927
• Likes Given: 5270
##### Re: EM Drive Developments
« Reply #2469 on: 10/23/2014 03:00 AM »
Am I to understand this 'Ionic Wind' explanation means this device would not produce thrust in a vacuum - or in space?

Good question.  There are several explanations that have been proposed for how these (ionic wind) "lifters" work.
From the theoretical explanation and experiments conducted by Prof.Barrett at MIT the answer is no, they wouldn't work in a vacuum.

Also this 2004 NASA contract report http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171929.pdf

They conducted several tests in a vacuum and concluded:

"After several days of tests, we found that no device showed signs of rotation at a pressure
less than 300 Torr, with one exception. When Device 2 wired according to Circuit A was placed
in the chamber and immediately pumped down to a pressure of 5.5 × 10–5 Torr, something
interesting happened. The voltage on it was increased to 44 kV, and through the viewing port a
large arc was observed. At that same moment, the device was seen to move about an eighth of a
rotation and stop."

also:

"Robert Talley of Veritay Technology5 performed tests of ACTs in a vacuum in the late
1980’s under Air Force contract. The tests did not let the ACTs spin, but instead suspended it
from a torsion wire. This gave him the sensitivity to be able to measure small forces. His report
is the only written report we have found from the last half-century that describes a measurement
of a force while in a vacuum chamber. Talley ultimately attributed the force that he observed to
the electrostatic interaction between the chamber and the device. Talley wrote, “Direct
experimental results show that under high vacuum conditions… no detectable propulsive force
was electrostatically induced by applying a static potential difference… between test device
electrodes…”
« Last Edit: 10/23/2014 03:02 AM by Rodal »

#### ThinkerX

• Full Member
• Posts: 303
• Alaska
• Liked: 113
• Likes Given: 59
##### Re: EM Drive Developments
« Reply #2470 on: 10/23/2014 03:21 AM »
Quote
Good question.  There are several explanations that have been proposed for how these (ionic wind) "lifters" work.
From the theoretical explanation and experiments conducted by Prof.Barrett at MIT the answer is no, they wouldn't work in a vacuum.

what I expected.  Still, I wonder if a 'cheat' would work...have the device - or at least the electrodes surrounded by a 'atmosphere' emitted from the spacecraft itself.  Of course, you'd have to continuously replenish this
'atmosphere.'

But at this point, we are almost in normal ion drive territory anyhow.

Be real interesting to see how any of these EM drives do in a vacuum.

#### Star One

• Senior Member
• Posts: 8020
• UK
• Liked: 1281
• Likes Given: 168
##### Re: EM Drive Developments
« Reply #2471 on: 10/23/2014 06:26 AM »

Am I to understand this 'Ionic Wind' explanation means this device would not produce thrust in a vacuum - or in space?

Still useful then as a general principle if they will operate in an atmosphere, question is to me in relation to space how much of an atmosphere do they need to operate.

#### ThinkerX

• Full Member
• Posts: 303
• Alaska
• Liked: 113
• Likes Given: 59
##### Re: EM Drive Developments
« Reply #2472 on: 10/23/2014 06:34 AM »
Quote
Still useful then as a general principle if they will operate in an atmosphere, question is to me in relation to space how much of an atmosphere do they need to operate.

Hence the 'cheat' - have the area around the electrodes partly enclosed, and inject just enough gas into the area for the device to function.  You'd have to replenish the gas fairly often, though.

But if the 'EM Drive' is a variant of these 'ionic wind lifters' that can function in a vacuum, then things get interesting.

Vacuum testing needed.

#### Mulletron

• Full Member
• Posts: 1113
• Liked: 776
• Likes Given: 1013
##### Re: EM Drive Developments
« Reply #2473 on: 10/23/2014 07:58 AM »
How can it be postulated that Evanescent Waves by themselves can solve the closed-system, momentum-conservation problem?

They can't by themselves using classical physics.  One spaceship may transmit an evanescent field to move external small nanosatellites next to it (would not be an interesting form of propulsion, and the center of mass composed by the nanosatellites and the spacecraft system would not accelerate either).  But it cannot move itself just by using Evanescent waves without any external field.

A spaceship cannot propel itself by using Evanescent Waves any better than it can propel itself using Electromagnetic Fields.  It is a closed system.

A swimmer can swim in the ocean because the ocean water has its own inertia and resists acceleration.  An astronaut cannot propel itself by waving her arms and legs in space.

To enable propulsion one must have an open system: external dark matter, external fields: like the Earth's magnetic field, an external aether, even consideration of the external quantum vacuum, etc.  But certainly not just Evanescent Fields by themselves that are self generated and only interacting in a closed system.

To avoid this confusion one must rely on conservation principles: conservation of momentum, conservation of energy, and variational principles.

I'm glad to see you are finally starting to acknowledge what I have been trying to drive home all this time about closed systems, and appear to have taken to heart what I introduced previously about hidden momentum.

As I have always said, you can't get thrust from what is happening inside of a closed system, except by artifacts, like leaking heat and magnetic influence. The experimentalist tell me they measured thrust. It is my job to find out why without breaking physics, or making up new physics.

Unfortunately, where I'm going with evanescent fields (which would appear on the outside of a waveguide/cavity/whatever) it is making it appear that EMdrive isn't viable. Normally an evanescent field doesn't have any effect whatsoever, unless it is able to couple to a nearby structure, weakly or strongly. I'm still working on it. Hope I'm wrong.

I am working on the geometry (slope) of the truncated cone and how it could give rise to a rash of leaky evanescent modes. It is not easy. Need help really.
http://forum.nasaspaceflight.com/index.php?topic=29276.msg1273995#msg1273995
Using Aero's info from Shawyer, thanks.

"The small end diameters are set just above the cut-off diameter corresponding to the mode and frequency of the design."

"The small end diameters are set just above the cut-off diameter corresponding to the mode and frequency of the design."
Evanescent modes are modes below the cutoff frequency.

The 6.25 inch small end dimension I educatedly guessed. The 6.25 inch cutoff freq is 1889mhz.
1880mhz is 6.28 inches. 1932-1936mhz is 6.1 inches. Seems like this thing is operating above and below cutoff, where cutoff is measured across the small end of the device. So basically right on the edge of cutoff, modified by the accuracy of their signal generating equipment. I didn't see them using an Anritsu or anything accurate. I have to measure the slope of the device more carefully.
Working this angle...........I haven't completely pulled the trigger on this yet. More work is needed....

If this device is say ~6inch at the small end and ~12 inch at the large end, the bandwidth is between 1968mhz and 984mhz. But it is being operated at a single frequency somewhere in between arbitrarily, but close to cutoff.

I don't have the thickness of the cavity walls, but in evanescent fields, it isn't important, as the rule of thumb for the near field zone is 1/3 of wavelength~2 inches for the Nasa test article.

Near field effects could possibly put a nail in EMdrive's coffin. I hope not, but science isn't a process of trying to prove things work or are right. It is the other way around.

A backgrounder on strongly coupled evanescent fields...it is the conceptual basis for inductive non radiative wireless charging we use for our cell phones and tablets.

Evanescent fields appear on the outside of waveguides and fall off exponentially (quickly). They don't interact with hardly anything unless they can couple to another transmission line or structure which can accept the leaky mode, either strongly or weakly. The structures around the test articles could be that structure. It is worthy of exploration. Near field effects aren't fringe science. They are real and we use them every day.

Marin Soljacic from MIT, has a lot of work published that I'm reading related to this.

Edited for clarity/grammar.
« Last Edit: 10/31/2014 04:06 PM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

#### Mulletron

• Full Member
• Posts: 1113
• Liked: 776
• Likes Given: 1013
##### Re: EM Drive Developments
« Reply #2474 on: 10/23/2014 09:39 AM »
Quote
Still useful then as a general principle if they will operate in an atmosphere, question is to me in relation to space how much of an atmosphere do they need to operate.

Hence the 'cheat' - have the area around the electrodes partly enclosed, and inject just enough gas into the area for the device to function.  You'd have to replenish the gas fairly often, though.

But if the 'EM Drive' is a variant of these 'ionic wind lifters' that can function in a vacuum, then things get interesting.

Vacuum testing needed.

I can safely rule out ionic wind effects because the device walls aren't charged with thousands of volts DC required for an ionization wind to form. See the Biefeld–Brown effect effect. This was thoroughly debunked, as not antigravity, just ionized air flowing.

But I CAN safely say there are thermal effects: See the attached pic. You can see the instant 70uN impulse at rf on followed by a gradual heat buildup providing a gradual thrust increase, followed by an instant impulse drop at rf off, followed by cooling. For some reason, TE behaved this way. Slow heating and cooling are they only ways I can see a gradual build and decline over 30 seconds.
Challenge your preconceptions, or they will challenge you. - Velik

#### frobnicat

• Full Member
• Posts: 518
• Liked: 500
• Likes Given: 151
##### Re: EM Drive Developments
« Reply #2475 on: 10/23/2014 10:36 AM »
Quote
So the complete total of all the photons in the cavity are giving their momentum up, and more, to thrust every second. How can that possible make sense. And even don't look at the energy.

Unruh waves can't come close to making a big enough change in mass to cause lost mass to exceed the existing mass. (mi=m(1-L/4T)) For this to work, T would need to be equal to or less than L/4.

There is one way of course but if I say "Tachyons," I'll likely be banned.

Then don't say 'Tachyons.'

I've has idle thoughts about a long shot possible resolution to this problem these past couple of days.

Muletron posted a video a couple days ago giving sort of a capsule history of research into subatomic particles.  The part that intrigued me was where the narrator put forth a chart showing a dozen plus subatomic particles discovered in the search for the Higgs boson.  His attitude - which I'd seen before in print - was one of embarrassed dismissal.  The attitude being these particles are a sort of unprofitable sideline, not worth detailed investigation.    Yet I wonder...might not one or more varieties of these particles hold part of the solution to this drive?  They are elementary 'building block' type critters - maybe certain rules don't fully apply to them?  Maybe they're attracted to photons?

Seems to be three very different hypothesis for EMdrive effect to be real (usable in deep space)

1/ Unknown particles constitute a "bath" and EMdrives are interacting with them. We did a few calculations with dak matter (axions...) as candidate and it could just very barely account to relevant thrust magnitudes given the proven upper bounds of dark something in solar system (as "something", whatever it is, surely has gravitational effects) and taking all but the most optimistic assumptions, in particular a perfect coupling, that is using a coupling constant of 1 when the experiments seems to put the bar below 10^-15. Going faster and faster, at some point one will have to overcome more medium incoming momentum than can get from throwing it backward even faster (i.e. air breathing at Mach 10...) and therefore we should expect a decreasing efficiency at speeds approaching 1/(thrust/power) relative to the medium. That is lower usable speed when higher thrust/power. The superconducting Shawyer thingy of latest presentation (was it really built and tested ??) at 1N/kW is around 1km/s. This means that strong sidereal times correlation should be expected in the experiments results, unless the medium "wind" is synchronised with earth orbit and earth rotation at its surface. Unlikely for a weakly interacting medium. Any case, not only interstellar but also interplanetary transits couldn't count on 1N/kW.
I see one last chance if the medium is composed of particles with widely varying velocities around the average local flow (that is, we have a hot gas of particles) and the device somehow succeeds at interacting only with the ones going the right way (roughly comoving, or coming from behind and pushing like for a sail) . At least two hurdles to overcome then : the amount of "dark something" which we know is bounded (from gravitational studies) and barely making it if all of it were used, and there we are talking of using just a part of it. And the fact that this "coupling with only the velocities that serve my purpose" seriously looks like a Maxwell's demon : need to properly address the thermodynamic of it.

2/ Quantum vacuum would also fit in this category of "bath" but exhibits a very specific behaviour : contrary to any sea of real particles it doesn't define a natural local rest frame (an average group velocity vector in the vicinity) if Lorentz invariance is to hold. So if it is a plasma, it is a plasma that is always harvested at rest speed. This is very convenient when compared to the previous situation. Also, this is breaking apparent energy conservation... Whatever we are harvesting at 0 speed relative to us were not 0 speed relative to others, and hence we are subtracting energy from vacuum. Which is, by definition, supposed to be a zero point... I don't see that is making any sense. Much more serious brains than mine on the subject ( John Baez, Sean Carroll ) have the same view about this quantum vacuum plasma. Authority is not a scientific argument by itself but at some time one has to say when an idea (even to explain a supposedly real effect) is just so deeply flawed as being nonsense. We may also have a Maxwell's demon hiding its hideous face behind the curtain of "quantum vacuum plasma".

3/ We are not using a bath or aether, the EMdrive just comes by on its own in nothingness and emits something that is forever lost (can't be closed, closed solutions can't see their centre of energy depart from an inertial trajectory). So if I consider a device in its own rest frame, it is spending a infinitesimal energy E, with this Energy it "creates" and gives velocity to a "thing" of mass m that is leaving and never to come back again. With Gamma the Lorentz factor 1/sqrt(1-v²/c²), v in the rest frame where the device is not (yet) moving.
E = gamma m c²  Energy spent by device to give thing of mass m a velocity of v
p = gamma m v  Momentum of the thing of mass m and velocity leaving the device forever
We agree that conservation of energy and conservation of momentum are the two most fundamental rules to apply. So for the later, the device gets a reaction kick of p momentum, at the price of spent energy E.
Thrust is momentum kicks per second, Power is spent Energy  per second. Hence :
thrust/power = p/E = v/c²

The consequences are
thrust/power < 1/c => v/c² < 1/c => v<c    classical rocket, reaction on usual mass
thrust/power = 1/c => v/c² = 1/c => v=c    photon rocket, reaction on particles of 0 rest mass
thrust/power > 1/c => v/c² > 1/c => v>c    tachyon rocket, reaction on particles of imaginary rest mass

So in effect : we say tachyons !
That explains all, why claiming thrust/power>1/c for EMdrive automatically seems to contradict energy conservation. We are getting more total kinetic energy at the end of a mission than was put in by the generator, because we are emitting debt, each tachyon carries away at FTL velocity a borrowing never to be paid back.

Except that apparently to prevent problems of causal paradoxes, a system that emits tachyons also receive tachyons, and can't tell the difference between emitting and receiving tachyons. That or otherwise superluminal particles either don't exist or never interact (not even gravitationally). Anyway, would make a pure tachyon emitter an impossibility.

Got to speak to my government about this interesting prospect of sending debt away at FTL speed to be sure never to hear about it again.

#### frobnicat

• Full Member
• Posts: 518
• Liked: 500
• Likes Given: 151
##### Re: EM Drive Developments
« Reply #2476 on: 10/23/2014 12:03 PM »
I should add that
thrust/power < 1/c => v/c² < 1/c => v<c    classical rocket, reaction on usual mass
is not in contradiction that obviously a classical chemical rocket or ion thruster has thrust/power_ej>1/c where power_ej is the power used to give ejected mass its velocity. To fairly compare classical action/reaction schemes with "propellantless" schemes, the ejected mass has to count as for its equivalent energy content. Ie a classical rocket sending backward m kg at subrelativistic v m/s is forever losing an energy of 1/2mv² + mc² and this mc² term is huge compared to 1/2mv² (the only energy accounted for in power_ej). This mass would have been better spent by being converted to energy and sent backward as 0 rest mass particles (photon rocket).

« Last Edit: 10/23/2014 12:11 PM by frobnicat »

#### JohnFornaro

• Not an expert
• Senior Member
• Posts: 9162
• Delta-t is the salient metric.
• Planet Eaarth
• Liked: 610
• Likes Given: 314
##### Re: EM Drive Developments
« Reply #2477 on: 10/23/2014 12:30 PM »
I made a ... estimate of the Flight thruster dimensions operating at 385 GHz.

w-small =    7.062943185   cm
w-big =   11.02062266   cm
height =    7.114289902   cm

This is not even wrong.  Clearly, the dimensions are:

w-small =    7.1142899020001   cm
w-big =   11.0629431850002   cm
height =    7.020622660003   cm

couldn't resist.
Sometimes I just flat out don't get it.

#### JohnFornaro

• Not an expert
• Senior Member
• Posts: 9162
• Delta-t is the salient metric.
• Planet Eaarth
• Liked: 610
• Likes Given: 314
##### Re: EM Drive Developments
« Reply #2478 on: 10/23/2014 12:57 PM »
I ... estimate ... the Flight thruster dimensions ...

w-small = 1"
w-big =   2"
height = 3"

...

I am dizzy with all the tests that Shawyer has conducted and with the different names he gives the tested device.  ...

This is circumstantial and corroborating evidence supporting the conjecture regarding the intentional reluctance of the experimentors to freely share their data.

The reluctance is certainly understandable, for at least three reasons, none of which can be discussed except on an informal basis among disinterested professional friends:

1. A surfeit of professional pride in understanding the obscure physics, combined with the typical disregard paid by professionals to amateur website contributors.

B. A pragmatic need to share without sharing, knowing full well the economic benefits of a vastly superior propulsive method.

iii. A stubborn refusal to realize that nothing is being seen.

Vee. Other reasons, such as keeping the rabble occupied with measuring Faztek thingies, so as to keep them off the streets protesting the forty year lack of accomplishment at NASA at doing what was promised back then; a peaceful future realizing mankind's destiny in the universe at large.

As I mentioned at:

http://forum.nasaspaceflight.com/index.php?topic=29276.msg1274449#msg1274449

I note that we are spending a lotta time arguing about these dimensions.  The good Doctor asked, rather politely, a hundred or more pages ago, but got only partial dimensional answers.  Since then Paul March decided to go mum.

Easily answered questions go without answer, which reflects on those who experiment, not on those who try to understand.

I'd like to thank the EagleWorks team for their help and cooperation.  (They should probably set up shop in Awizona; 'twould help their worldview.)

On the plus side, thanks to decent forum moderation, we no longer have to hear from those who disparage everybody's credentials.
Sometimes I just flat out don't get it.

#### JohnFornaro

• Not an expert
• Senior Member
• Posts: 9162
• Delta-t is the salient metric.
• Planet Eaarth
• Liked: 610
• Likes Given: 314
##### Re: EM Drive Developments
« Reply #2479 on: 10/23/2014 12:59 PM »
A much higher frequency might indicate flex in the arm itself.

Prima facie evidence that not all that much is happening.
Sometimes I just flat out don't get it.

Tags: