Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1881365 times)

Offline Rodal

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I need some data:

1) Dimensions of your model:  (all in meters)  I think it is the RFMWGUY model at 2.45 GHz excitation frequency

Dbig=
Dsmall=
Length =

(set! bigdia 11.01)                             ; ID - inches
(set! smalldia 6.25)                           ; ID - inches
(set! high 10.2)                                   ; length - inches

Source: https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=37642.0;attach=1042821

So, using your notation and SI units:

Dbig= 0.279654 meters
Dsmall= 0.15875 meters
Length = 0.25908 meters

----------------------------------------------------------------

Note to aero: maybe it would be a good idea to define the .ctl model entirely in SI units, from the very start, instead of converting it all later. What do you think?

Thanks.  I used Wolfram Mathematica to figure out where the circle nodes are located on the y and z axes.

Number of Rows: 1 to 245
Number of Columns: 1 to 261

- Big base        x = Row 15,  y & z = columns 15 and 248
- Small base    x = Row 232, y & z =columns 65 and 198

Notice that the center of the circles is not at node 131 ((261-1)/2+1=131), but it is equidistant from nodes 131 and 132 (at x=131.5)

I am told that the fact that the center node is not at node 131 may be due to "meep's eps averaging" ( http://ab-initio.mit.edu/wiki/index.php/Meep_FAQ#Why_doesn.27t_turning_off_subpixel_averaging_work.3F ) even though there is no dielectric insert in this model, and/or the fact that the antenna is given a thickness of two nodes and it is centered between them.  The antenna is located at nodes 131 and 132 (centered at x=131.5).

Also notice that this does not quite scale exactly as

Big Diameter = 11.01 in = 279.65 mm

279.65 mm/ (248 - 15) = 1.200 mm distance between nodes in the circular cross-section

____________________

Small Diameter = 6.25 in = 158.75 mm

158.75 mm/(198 - 65) = 1.194 mm distance between nodes in the circular cross-section
« Last Edit: 07/17/2015 03:27 AM by Rodal »

Offline rfmwguy

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NSF-1701 update...good news for meepers, I have not yet placed the magnetron into the frustum. I will this weekend, so here's ur chance to suggest placement. Suggest wavelength placement and locale...near big, near small or centered. I was planning on 1/2 wavelength from small end...doesn't matter to me. Julian moved from large end to center...meepers can respond.

Offline ThinkerX

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Quote
NSF-1701 update...good news for meepers, I have not yet placed the magnetron into the frustum. I will this weekend, so here's ur chance to suggest placement. Suggest wavelength placement and locale...near big, near small or centered. I was planning on 1/2 wavelength from small end...doesn't matter to me. Julian moved from large end to center...meepers can respond.

Vote from the peanut gallery: start at the small end and work your way towards the base in measured increments?

Offline DrBagelBites

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NSF-1701 update...good news for meepers, I have not yet placed the magnetron into the frustum. I will this weekend, so here's ur chance to suggest placement. Suggest wavelength placement and locale...near big, near small or centered. I was planning on 1/2 wavelength from small end...doesn't matter to me. Julian moved from large end to center...meepers can respond.

Based on the Wolfram Mathematica analysis of the Meep model, the antenna RF feed should be close to the small end, in the location that aero modeled (aero to respond as to exact location).

According to this model, the antenna at the big end is a no-no.  Bad, because it equalizes the pressure distribution at both ends.

What about directly on top of the small end?

Offline SeeShells

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NSF-1701 update...good news for meepers, I have not yet placed the magnetron into the frustum. I will this weekend, so here's ur chance to suggest placement. Suggest wavelength placement and locale...near big, near small or centered. I was planning on 1/2 wavelength from small end...doesn't matter to me. Julian moved from large end to center...meepers can respond.

Based on the Wolfram Mathematica analysis of the Meep model, the antenna RF feed should be close to the small end, in the location that aero modeled (aero to respond as to exact location).

According to this model, the antenna at the big end is a no-no.  Bad, because it equalizes the pressure distribution at both ends.

We have meep data on this Doc? For the big end?

Shell

Offline SeeShells

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NSF-1701 update...good news for meepers, I have not yet placed the magnetron into the frustum. I will this weekend, so here's ur chance to suggest placement. Suggest wavelength placement and locale...near big, near small or centered. I was planning on 1/2 wavelength from small end...doesn't matter to me. Julian moved from large end to center...meepers can respond.
http://electronicdesign.com/wireless/what-s-difference-between-dipole-and-ground-plane-antenna
Figures 3 and 4 treat the small endplate as the ground plane horizontal to the plate,
<4. This is the vertical radiation pattern showing elevation of signal from a horizontal dipole one half wavelength above the ground.>
Based on the Wolfram Mathematica analysis of the Meep model, the antenna RF feed should be close to the small end, in the location that aero modeled (aero to respond as to exact location).

According to this model, the antenna at the big end is a no-no.  Bad, because it equalizes the pressure distribution at both ends.

Offline rfmwguy

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The easiest install will be a centered insert on the small diameter. Antenna is monopole. Small end would be ground plane. Can also locate on frustum side near small end. Question would be does center insertion on small plate disrupt anticipated vectors...hmmm

Offline WarpTech

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The easiest install will be a centered insert on the small diameter. Antenna is monopole. Small end would be ground plane. Can also locate on frustum side near small end. Question would be does center insertion on small plate disrupt anticipated vectors...hmmm

What would you do for an antenna if you wanted to setup an circular Bessel function standing wave with near zero group velocity, at the smallest diameter of the frustum? Would you use a monopole or a loop? I think for the TM modes, it needs to use a monopole and for TE modes, it would need to be a loop. Is that correct? And I think it would need to be centered at the small end, just as you said.

Maybe we should also model the best way to setup a standing wave for the small diameter dimension, rather than in the length dimension, by modeling a straight cylinder waveguide and find the antenna configuration & location, that has the lowest group velocity and least distortion. Then taper the cavity from there.

Just a thought.
Todd
   

Offline DaCunha

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According to present data, testing the EMDrive with input powers at or above 1 MW is necessary to reach a thrust that can actually be experienced without doubt of measurement errors.

Achieving a thrust level high enough to lift an object would (as done by Goddard with chemical rockets) finally convince people to adequately fund R&D in this area.

Let us gather enough supporters to send an E-Mail to Mythbusters.

They definitely have the money and means to use a Gyrotron, Klystron or a similar powerful microwave source and build a simple truncated cone microwave resonator to see whether they can achieve a level of thrust high enough to convince people to fund adequate R&D in this area.

Offline Damon Hill

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A megawatt is very serious power.

Where is the excess energy going?  Something's got to be getting very, very hot.

Offline TheTraveller

The easiest install will be a centered insert on the small diameter. Antenna is monopole. Small end would be ground plane. Can also locate on frustum side near small end. Question would be does center insertion on small plate disrupt anticipated vectors...hmmm

What would you do for an antenna if you wanted to setup an circular Bessel function standing wave with near zero group velocity, at the smallest diameter of the frustum? Would you use a monopole or a loop? I think for the TM modes, it needs to use a monopole and for TE modes, it would need to be a loop. Is that correct? And I think it would need to be centered at the small end, just as you said.

Maybe we should also model the best way to setup a standing wave for the small diameter dimension, rather than in the length dimension, by modeling a straight cylinder waveguide and find the antenna configuration & location, that has the lowest group velocity and least distortion. Then taper the cavity from there.

Just a thought.
Todd
 

Attached is now you would drive a TE01 constant diameter circular horn antenna (such as a WiFi can antenna). Lambda is of course the Guide Wavelength and not the free space wavelength.

Would be interesting to see the Meep analysis based on a known excitation antenna setup.

Gets more interesting when the EM wave that needs to be excited / reinforced has spherical and not planar wave fronts.

Just remember the antenna, in the case of a resonant cavity, is there to excite and reinforce an existing EM wave front. It is no longer an antenna as in the classical case of emitting unrestricted EM waves into free space. It needs to couple to and reinforce the existing spherical EM waves trapped inside the cavity, while causing minimal disturbance (phase distortion) to the resonant spherical EM waves.
« Last Edit: 07/17/2015 08:57 AM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline Jeff131

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I like the idea because I actually think THAT the EMDrive IS a myth. And nothing else.

And it definitely should be the matter of Mythbusters and not of serious scientists.

Offline DaCunha

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I agree with you, partially. Maybe, we will see nothing else than discharges, light arcs, and a hot cone shaped metal cavity resonator. If so, the whole EMDrive discussion is over. Only if not, adequate research should start.
We can't decide at the moment. If you want to support the idea send an E-Mail to the makers of Mythbusters. They accept suggestions of myths via E-Mail.
« Last Edit: 07/17/2015 09:25 AM by DaCunha »

Offline Jeff131

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So? Where should I send this E-Mail? What should be written inside?

Offline DaCunha

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So? Where should I send this E-Mail? What should be written inside?

Sorry, the original thread was deleted and the replies were inserted here. I hope you will find my answer here.

You can send the E-Mail to mythfans@beyond.com.au.

As a subject choose something like "Space ship drive with 1 Megawatt microwaves and a truncated metal cone"

And just write the question " Can you build a spaceship drive if you let a power of 1 MW enter a truncated metal cone".

It has to sound simple and not too scientific. Keep in mind they are interested in show not in science.
« Last Edit: 07/17/2015 09:31 AM by DaCunha »

Offline Flyby

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According to present data, testing the EMDrive with input powers at or above 1 MW is necessary to reach a thrust that can actually be experienced without doubt of measurement errors.

Achieving a thrust level high enough to lift an object would (as done by Goddard with chemical rockets) finally convince people to adequately fund R&D in this area.

Let us gather enough supporters to send an E-Mail to Mythbusters.

They definitely have the money and means to use a Gyrotron, Klystron or a similar powerful microwave source and build a simple truncated cone microwave resonator to see whether they can achieve a level of thrust high enough to convince people to fund adequate R&D in this area.

You do not need that kind of power to have convincing application for the EMdrive.
All depends on the type of application you're projecting.

A weak but working EMdrive would have a tremendous impact already on the space industry as orbital position thrusters. A huge fuel saver !
If , fe, one of the DIY devices would be able to replicate prof Yang's results, in the order of 72gf, that on itself would be a real, usable result..

If however you want to achieve the rather inflated claims of EMdrives lifting tons and traveling to the nearest star system in 11years, then yes you'll need a lot more of power. But , let's be honest, those are claims made on paper and are not based upon a real world EMdrive.

What scales nicely on paper almost never scales like that in the real world...

BUT...Let's just concentrate first on getting clear and unambiguous results so that the EMdrive can gain credibility. If it cant, well.... then it has been an interesting reading on the forum here and a  fun hoax to spend our time on...
« Last Edit: 07/17/2015 09:42 AM by Flyby »

Offline deltaMass

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According to present data, testing the EMDrive with input powers at or above 1 MW is necessary to reach a thrust that can actually be experienced without doubt of measurement errors.

Achieving a thrust level high enough to lift an object would (as done by Goddard with chemical rockets) finally convince people to adequately fund R&D in this area.

Let us gather enough supporters to send an E-Mail to Mythbusters.

They definitely have the money and means to use a Gyrotron, Klystron or a similar powerful microwave source and build a simple truncated cone microwave resonator to see whether they can achieve a level of thrust high enough to convince people to fund adequate R&D in this area.

You do not need that kind of power to have convincing application for the EMdrive.
All depends on the type of application you're projecting.

A weak but working EMdrive would have a tremendous impact already on the space industry as orbital position thrusters. A huge fuel saver !
If , fe, one of the DIY devices would be able to replicate prof Yang's results, in the order of 72gf, that on itself would be a real, usable result..

If however you want to achieve the rather inflated claims of EMdrives lifting tons and traveling to the nearest star system in 11years, then yes you'll need a lot more of power. But , let's be honest, those are claims made on paper and are not based upon a real world EMdrive.

What scales nicely on paper almost never scales like that in the real world...

BUT...Let's just concentrate first on getting clear and unambiguous results so that the EMdrive can gain credibility. If it cant, well.... then it has been an interesting reading on the forum here and a  fun hoax to spend our time on...
If EmDrive works, and if it performs at around 1 N/KW, then it can be used in a rotary configuration whereby its tangential speed exceeds 1 Km/s. Then you get as much power as you like. Some would say that the very fact that a statement like that can be made means that EmDrive will never work.

Offline deltaMass

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http://www.nanowerk.com/nanotechnology-news/newsid=40797.php

Here's a high Q cavity for light that's a bit weird. Nobody has noticed it moving about  8)

Offline Chrochne

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I like the idea because I actually think THAT the EMDrive IS a myth. And nothing else.

And it definitely should be the matter of Mythbusters and not of serious scientists.

I disagree. From the independent scientific level Dr. Rodal and the others here are actually very sceptic about the EmDrive. Still their research based on rigorous work is starting to show that there may be something into it. You have to understand that even after the years of claims that EmDrive works (claimed by Mr. Shawyer) the true research begun only just now ( from the time NASA EW and chinese folks showed their first results).

I learned here that too much shouting why it can and why it can not work leads to dead end only and proves nothing.


Offline TheUberOverLord

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I like the idea because I actually think THAT the EMDrive IS a myth. And nothing else.

And it definitely should be the matter of Mythbusters and not of serious scientists.

I disagree. From the independent scientific level Dr. Rodal and the others here are actually very sceptic about the EmDrive. Still their research based on rigorous work is starting to show that there may be something into it. You have to understand that even after the years of claims that EmDrive works (claimed by Mr. Shawyer) the true research begun only just now ( from the time NASA EW and chinese folks showed their first results).

I learned here that too much shouting why it can and why it can not work leads to dead end only and proves nothing.

If the EM Drive turns out to be a valid form of propellant-less propulsion? Is it not also fair to also give credit where credit is due?

After all. Do you think that the first human that discovered the wheel could explain why it worked? Does that mean that there was ("as you say") no ("true research") by the original builder of the wheel, until the reasons why the wheel worked could be explained in full detail, by others?

After all. Even Newton was not 100 percent correct with all his known statements, Yet we still respect him on what he was correct about vs. trash talking him about what he was incorrect about.

Note: We as humans have been manipulating atoms in many ways, for many reasons and for many purposes, for some time now. However, only recently have we been able to determine why atoms have mass.

Don
« Last Edit: 07/17/2015 12:42 PM by TheUberOverLord »
EM Drive builders can use these free Interfaces to show their tests live using any IP Cameras in websites Click for live demo examples

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