Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1874341 times)

Offline LasJayhawk

Random thoughts:

A microwave oven Maggie, operating at 200C in a vacuum may out gas from its radiator. This could cause the appearance of something that looks like working mass, but isn't.

Once again, the Edison Effect predates the discovery of the electron by over a decade. Who knows what we could be spitting out the business end... :)

Has anyone considered a fractal antenna, to try and maximize the power dumped into the frustum?
Yes a fractal antenna would be a great device to use but normally the ones I've seen have been small and limited in transmitted power. Do you know of larger that could take 1000 watts?

Shell

I'm thinking about finesse at a lower power. The whole microwave magnetron seems like the "don't force it Newt, get a bigger hammer" approach. Eagle works was getting "thrust" at 16 watts into the frustum. I'm wondering if attempting to get more at lower power with antenna design and placement is a worthwhile approach?

Offline WarpTech

  • Full Member
  • ****
  • Posts: 1304
  • Do it!
  • Vista, CA
  • Liked: 1350
  • Likes Given: 1814
....
Thanks and I took a look at this. Taken at face value it predicts that, in order to maximise the thrust/power ratio, one requires that independently:
- Ds/Db to be minimum
- Db to be minimum
- L to be minimum
even after accounting for the frequency scaling per Appendix I.
The thrust predictions seem roughly in line with the experimental data.
k = F/P seems to be, for the ranges graphed, about 3*10-7 N/W (about 300 uN for 1000 W).

I'm looking for a way to get much higher F/P values. I've indicated how this can be done per this formula.
I would welcome some concrete suggestions.

[A couple of notes on this derivation:
1. In Appendix I the n factor due to L is omitted (but the scaling conclusion is correct anyway)
2. Whenever I read about "accelerated photons" my toes curl up]

I just figured out that apparently, Dr. McCulloch's formula, Dr. @Notsosurofit's formula and my own formula using the cylindrical approximation, all amount to the same basic force. This force is proportional to, the change in energy from the small end to the big end, divided by the length, i.e, delta_E/delta_z.

Where the 3 formula differ, is in how this force is multiplied by the group velocity v/c or (v/c)2, and what formula is used for the group velocity.

Dr. McCulloch skips this concept entirely and simply inputs the energy as Power x time, using the speed of light and the length. No consideration of group velocity at all. He simply uses m*c^2 where m is derived by his theory.

Dr. @Notsosureofit's formula, after completing the square and factoring the difference between two frequencies squared. The basic force above is multiplied by the average cut-off (I know @Rodal) over the input frequency:

(ws + wb)/2*w

This was surprising and interesting. Note, that when the frequency is less than the average cut-off, (i.e, becoming evanescent) this factor is > 1.

My formula, without Zeng and Fan results in a factor that also depends on the frequency, but has a much larger value near the cut-off:

(w + wb)/(w - wb),

ws and wb, are the resonant or cut-off frequencies at each end respectively.

These factors are each multiplied by delta_E/delta_z, where delta_z is the length, and delta_E is the frequency shift from small end to big end. There is one more factor, and that is the impedance plots in Zeng and Fan for a cone. It is somewhere between the "infinite" value of my formula and the subtle value of @Notsosureofit's formula.

It's late, I hope I didn't make any errors, I'll be back. 8)
Todd

Offline TheTraveller

I'm thinking about finesse at a lower power. The whole microwave magnetron seems like the "don't force it Newt, get a bigger hammer" approach. Eagle works was getting "thrust" at 16 watts into the frustum. I'm wondering if attempting to get more at lower power with antenna design and placement is a worthwhile approach?

Way advised that if the antenna design, antenna placement and impedance matching are not correct, the EMDrive will be lucky to generate a Force.

IE the antenna and impedance matching are as important as achieving resonance at a high Q.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline demofsky

  • Full Member
  • *
  • Posts: 166
  • Liked: 96
  • Likes Given: 1671
2 comments I'd like to make:

First: Solar power.  The ISS arrays are about as big as you would want to build. With 80's solar cells they are good for about 30KW at 1 AU and beginning of life. The latest cells are about 3 times more efficient. If you used the same size arrays with the latest high efficiency cells you could eek out maybe 90-100KW per array or roughly 3/4 of a MW for something ISS sized. If you are in orbit, battery charging for night passes reduces usable power by over half. The arrays tend to be rather fragile as well.

I think I'd rather hook an EM drive up to a nuclear reactor.
....

This is exactly what I would have expected.  Remember though that EM (and other electric) Drives are very gentle so it does not matter if a tug uses massive (monstrous?) arrays that are fragile.  This thing will change course slowly and things will not fly off.  They use chemical rockets on the ISS and so the stress is much higher.

Edits:  Clarification.

Well for attitude control a tug may have more powerful attitude control thrusters. So rates have to be kept down. You also have to be concerned about environments. Atomic oxygen and RCS thruster exhaust can damage or pit cell coverings reducing power generation over time.

Finally you have to be concerned about thermal loading. The mast structure has to be flexible to deploy which can leave it susceptible to buckling when thermal stresses are coupled with mechanical stresses from maneuvers.

It's not that it can't be done, it has already on the ISS, its just more of a pain in the butt than you might think.

Attitude can be controlled - gently and contaminant free - with EM Drives.  Admittedly a super tanker would look like a sports car. 

In addition to thermal and physical stresses you would have to worry about electrostatic and electromagnetic stresses, particularly with solar winds over such large surfaces.

However, because there is no exhaust contamination, you can use a distributed architecture where the drives are spread over the array.  This could be seen as a modular concept where you stich together as many modules as you might need for the anticipated payloads and transit times.  Each module would have its own power, thrusters, thermal radiators, IMUs etc. 

Shared interfaces would be structural and guidance, all with appropriate redundancy.  In theory, you would avoid the massive masts like in the ISS but you still need structural support for the presumably concentrated payload so I am not sure how this would come together most effectively for that.

I call this design pattern the "magic carpet".  This approach may be most appropriate for interplanetary tugs with a smaller, more traditional approach used for intraplanetary tugs with smaller payloads.

Offline TheTraveller

I stopped looking at the Design Factor as a serious formula as soon as I learnt from TheTraveller that it uses the "cut-off" frequency for an open waveguide of constant cross-section, as it is known that tapered waveguides and cavities do NOT have rigid cut-off.  Only constant cross-section waveguides have a rigid cut-off condition.

Yet my spreadsheet, based on using Shawyer's Df and circular waveguide cutoff correctly predicted the same TE111 resonance at 2.45GHz for the Tajmar frustum (posted before your results) as did you method.

Which would suggest your theory about rigid cut-off not being valid in a tapered waveguide is not correct.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline TheTraveller

....
Thanks and I took a look at this. Taken at face value it predicts that, in order to maximise the thrust/power ratio, one requires that independently:
- Ds/Db to be minimum
- Db to be minimum
- L to be minimum
even after accounting for the frequency scaling per Appendix I.
The thrust predictions seem roughly in line with the experimental data.
k = F/P seems to be, for the ranges graphed, about 3*10-7 N/W (about 300 uN for 1000 W).

I'm looking for a way to get much higher F/P values. I've indicated how this can be done per this formula.
I would welcome some concrete suggestions.

[A couple of notes on this derivation:
1. In Appendix I the n factor due to L is omitted (but the scaling conclusion is correct anyway)
2. Whenever I read about "accelerated photons" my toes curl up]

I just figured out that apparently, Dr. McCulloch's formula, Dr. @Notsosurofit's formula and my own formula using the cylindrical approximation, all amount to the same basic force. This force is proportional to, the change in energy from the small end to the big end, divided by the length, i.e, delta_E/delta_z.

Where the 3 formula differ, is in how this force is multiplied by the group velocity v/c or (v/c)2, and what formula is used for the group velocity.

Dr. McCulloch skips this concept entirely and simply inputs the energy as Power x time, using the speed of light and the length. No consideration of group velocity at all. He simply uses m*c^2 where m is derived by his theory.

Dr. @Notsosureofit's formula, after completing the square and factoring the difference between two frequencies squared. The basic force above is multiplied by the average cut-off (I know @Rodal) over the input frequency:

(ws + wb)/2*w

This was surprising and interesting. Note, that when the frequency is less than the average cut-off, (i.e, becoming evanescent) this factor is > 1.

My formula, without Zeng and Fan results in a factor that also depends on the frequency, but has a much larger value near the cut-off:

(w + wb)/(w - wb),

ws and wb, are the resonant or cut-off frequencies at each end respectively.

These factors are each multiplied by delta_E/delta_z, where delta_z is the length, and delta_E is the frequency shift from small end to big end. There is one more factor, and that is the impedance plots in Zeng and Fan for a cone. It is somewhere between the "infinite" value of my formula and the subtle value of @Notsosureofit's formula.

It's late, I hope I didn't make any errors, I'll be back. 8)
Todd

Todd you also need to consider Shawyers equation, that Tajam says correctly predicted his Force, which is based on Shawyer's Df that factors in the cutoff at each end of the tapered cavity to produce the guide wavelengths at each end. The delta of the end plate guide wavelengths represents the delta of the end plates forces.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline SeeShells

  • Senior Member
  • *****
  • Posts: 2335
  • Every action there's a reaction we try to grasp.
  • United States
  • Liked: 2982
  • Likes Given: 2601
....
Thanks and I took a look at this. Taken at face value it predicts that, in order to maximise the thrust/power ratio, one requires that independently:
- Ds/Db to be minimum
- Db to be minimum
- L to be minimum
even after accounting for the frequency scaling per Appendix I.
The thrust predictions seem roughly in line with the experimental data.
k = F/P seems to be, for the ranges graphed, about 3*10-7 N/W (about 300 uN for 1000 W).

I'm looking for a way to get much higher F/P values. I've indicated how this can be done per this formula.
I would welcome some concrete suggestions.

[A couple of notes on this derivation:
1. In Appendix I the n factor due to L is omitted (but the scaling conclusion is correct anyway)
2. Whenever I read about "accelerated photons" my toes curl up]

I just figured out that apparently, Dr. McCulloch's formula, Dr. @Notsosurofit's formula and my own formula using the cylindrical approximation, all amount to the same basic force. This force is proportional to, the change in energy from the small end to the big end, divided by the length, i.e, delta_E/delta_z.

Where the 3 formula differ, is in how this force is multiplied by the group velocity v/c or (v/c)2, and what formula is used for the group velocity.

Dr. McCulloch skips this concept entirely and simply inputs the energy as Power x time, using the speed of light and the length. No consideration of group velocity at all. He simply uses m*c^2 where m is derived by his theory.

Dr. @Notsosureofit's formula, after completing the square and factoring the difference between two frequencies squared. The basic force above is multiplied by the average cut-off (I know @Rodal) over the input frequency:

(ws + wb)/2*w

This was surprising and interesting. Note, that when the frequency is less than the average cut-off, (i.e, becoming evanescent) this factor is > 1.

My formula, without Zeng and Fan results in a factor that also depends on the frequency, but has a much larger value near the cut-off:

(w + wb)/(w - wb),

ws and wb, are the resonant or cut-off frequencies at each end respectively.

These factors are each multiplied by delta_E/delta_z, where delta_z is the length, and delta_E is the frequency shift from small end to big end. There is one more factor, and that is the impedance plots in Zeng and Fan for a cone. It is somewhere between the "infinite" value of my formula and the subtle value of @Notsosureofit's formula.

It's late, I hope I didn't make any errors, I'll be back. 8)
Todd
It would seem that there is a commonality in all three of those theories and even in TT interpretation spreadsheet of RS's.
The first thing a theory should do is forecast the results from testing or be able to calculate a future test. This in itself doesn't make it the right formula or theory.

I was looking at notosureofit's paper today and even asked Dr. Rodal to explain a chart I was trying to interpret.

I received my first model test sheet copper today and it's poo (no TT I'm not going to go with a solid yet) I'm going to try to salvage the piece with holes that look like they were punched out with a nail but to get what I want I just might have to setup a jig in my drill press and do them right with a solid piece.

Anyway getting off point here. Since I have a little more time (just a couple days setback) I thought I'd start a cleaner layout for the split housing taking in the considerations of the creation of evanescent mode and cavity lengths I might test. The numbers are not quite right as I've not applied any formulas yet just back of the envelope calculations.

Interesting in how this is all pulling together.

Shell

Offline Prunesquallor

  • Full Member
  • *
  • Posts: 174
  • Currently, TeV Brane Resident
  • Liked: 157
  • Likes Given: 73
Spaceflight. I've avoided useage of the term without enough ground test results, but it might be time to plant a seed of discussion for the future considering Tajmar's paper. We will need to think about electric power for a smallsat. That will not be easy.

A magnetron is not 100% efficient, meaning that this type of device would require north of 1kW of electric power. This is not easily attainable on a satellite. RTGs are usually much below this.:

https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator

Solar panels appear to be the best choice at levels above 1kW:

https://en.wikipedia.org/wiki/Solar_panels_on_spacecraft

So dreams of deep space travel might look like this: Solar Panels to ? AU, jetison, then RTG takeover when out of solar influence. IOW, a hybrid power design.

Moral of story, optimize for max performance to weight ratio/effeciency. Partner with solar panel and/or RTG provider.

Agreed on solar power for inside the asteroid belt. However, What do you think abuot fuel cells?
A little unclear on those babies. You might have to upskill me a bit. ;)

What are guys proposing? A robotic EMDrive probe that leaves the solar system?  Why?

If you are proposing a test flight to validate the propulsion system, don't take it out somewhere where there is no power, motor it around the inner solar system where you have decent solar insolation values. Fuel cells are no help, they die when they run out of reactants, just like batteries.
Retired, yet... not

Offline Prunesquallor

  • Full Member
  • *
  • Posts: 174
  • Currently, TeV Brane Resident
  • Liked: 157
  • Likes Given: 73

Agreed on solar power for inside the asteroid belt. However, What do you think abuot fuel cells?

Fuel cells may have a use for powering aircraft on oxygen free places like Venus.
http://www.lockheedmartin.com/us/products/compact-fusion.html

Lockheed Martin: Compact Fusion Research & Development at the Skunk Works is working on this and since we're talking about future tech I think this would scale quite well to space.

There are other promising fusion projects that might fit the bill as well.  The question here is how well will a particular approach scale down to 5-10 MW?  The Lougheed approach does not have direct energy conversion so you need the standard turbines, etc. 

That said, the main thing is once you get something into orbit that is reliable you get a lot of amortization...

It will be interesting to do the trades on the different approaches.  Solar cells are a surprisingly strong alternative - especially to someone who strongly assumed you would need something nuclear for these power levels.

There is no need to dream of fusion for power levels of 5-10 MW. NASA has had space fission reactor design concepts for decades that do that.

1/r^2 is pretty brutal for solar out beyond Mars.

Edit: added solar
« Last Edit: 07/28/2015 12:24 PM by Prunesquallor »
Retired, yet... not

Offline DrBagelBites

  • Member
  • Posts: 71
  • Orlando
  • Liked: 59
  • Likes Given: 68
@Rodal

Let me know if your mind has changed on which question should be asked. I'll be checking in on the NSF throughout the day up to the talk.

-I

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
@Rodal

Let me know if your mind has changed on which question should be asked. I'll be checking in on the NSF throughout the day up to the talk.

-I
Yes, I will re-write the questions and re-submit this morning, taking into account the discussions in the thread and what we have learnt during the last few days

Offline RotoSequence

  • Full Member
  • ****
  • Posts: 777
  • Liked: 572
  • Likes Given: 780
As expected for the last couple of months, based on knowledgeable sources that Tajmar measurements in vacuum were even lower than NASA's, Tajmar's presentation instead of confirming the EM Drive is being used to make fun of it (in the same publication that previously had the headline about reaching Pluto in 18 months):

http://www.wired.com/2015/07/really-propellantless-space-drives-still-not-thing/

That's nothing unexpected for Katie Palmer. There are a lot of tech bloggers who are wholly unwilling to change their opinions, and will stick to their guns until further developments and evidence are incontrovertible, and the general public reaches the point where they would mock them for their previous opinions.
« Last Edit: 07/28/2015 01:16 PM by RotoSequence »

Offline TheTraveller

As expected for the last couple of months, based on knowledgeable sources that Tajmar measurements in vacuum were even lower than NASA's, Tajmar's presentation instead of confirming the EM Drive is being used to make fun of it (in the same publication that previously had the headline about reaching Pluto in 18 months):

http://www.wired.com/2015/07/really-propellantless-space-drives-still-not-thing/

Quote
. A new publication purports to test the drive’s magical thrust-making abilities. This time, the news is coming from a team at the Dresden University of Technology. They presented their results (thrust signatures of +/-20 microNewtons, if you must know) at a conference today, the Propulsion and Energy Forum and Exposition held by the American Institute for Aeronautics and Astronautics.

To be fair, these researchers constructed their version of the device so they could try to eliminate potential sources of error or interference, and they don’t say that they’ve validated the drive—just that they can’t explain where their teeny tiny thrust signatures are coming from. Despite what the Internet is saying, nobody has confirmed anything, and those silly physical laws still say propellantless space drives are impossible. If you want a physics primer and a refresher on the history of this crazy hype-machine of a device, here you go. Sorry to crush your dreams, space cadets.

I fail to see how constructing and testing an EM Drive with a Q below 50 (gross overcoupling ?) , with a huge waveguide entering its side asymmetrically (hence not surprising to get a huge side-force) and reporting its dimensions incorrectly by a factor of 2 (error-checking and proof-reading ??, what other errors are present in their unreported procedures ? ) qualifies as "constructing their version of the device so they could try to eliminate potential sources of error."

There has been more attention to detail in constructing a device to eliminate potential sources of error by DIY experimenters, frankly speaking...

As I have stated before. The Tajmar design is about as bad a design as could be done.

Looking closely at the photos it would seem epoxy was also used to secure the what looks like a hand made final waveguide section to the side wall of the cavity. Then epoxying the variable small end adjustable plate in place and sticking it in vacuum is just asking for problems.

With the lack of attention to detail in misquoting the frustum dimensions, one wonders what other detail are incorrect.

As for the coupling between the magnetron power wires and the damping PMs, simple to tightly twist the power feed wires together to eliminate any coupling and keep the PMs there for their superior damping.

Other than the Force signals obtained with the oil damping, the rest of the experimental data in the paper is a train wreck.

Score a big negative for all the issues surrounding the use of a magnetron for Rf power and waveguides with associated big holes in the side wall to route the power into an EMDrive, then dropping the Q to 50 to have the input bandwidth wide enough to swallow the magnetron frequency spread. Sorry but yuck.

Question for the magnetron DIYers. How will you get your Q to 50 so your frustum will accept all the magnetron energy. If it is higher than 50, the bandwidth may not be wide enough for your magnetron.

Give me a narrow band Rf signal that will allow the frustum to be tuned to a Q exceeding 100K and a VSWR feedback signal to track and adjust to cavity resonance changes.

My 100W amp is on the water. I'm so thankful that my mate found it.
« Last Edit: 07/28/2015 01:25 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
Herman Melville, Moby Dick

Offline martinc

  • Member
  • Posts: 19
  • UK
  • Liked: 3
  • Likes Given: 0
<attached: a promise not to pollute this incredible thread>

regarding the eagleworks laser interferometer results.. should this be a standard feature of all EM drive experiments going forward? i noted they seem to have created an EM drive just for this test with design differences. i wonder also if some fine particulate could be introduced into the fustrum and a camera to view the thrust effects internally.

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
It's a shame that Tajmar, being Director of an institute with access to fine equipment and trained staff, did such a shoddy job.
 
1. Not self-contained
2. Not correctly impedance matched
3. Thermal effects not analysed
4. Bloody great hole in the side of the frustum.

He's a good theoretician, but struggles as an experimenter. We all have our strengths and weaknesses.

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
<attached: a promise not to pollute this incredible thread>

regarding the eagleworks laser interferometer results.. should this be a standard feature of all EM drive experiments going forward? i noted they seem to have created an EM drive just for this test with design differences. i wonder also if some fine particulate could be introduced into the fustrum and a camera to view the thrust effects internally.

Welcome to the thread and thanks for your post :)

NASA's interferometer test involved a cylindrical EM Drive without a dielectric and having small transparent holes for the laser to go through.  There have been no further reports from NASA Eagleworks since NASA management asked that no further information be released (due to a lot of misinformation regarding NASA discovering a warp drive by accident).  SeeShells plans to film her experiments with a perforated EM Drive with a camera to see the action inside it.

Offline deltaMass

  • Full Member
  • ****
  • Posts: 955
  • A Brit in California
  • Liked: 671
  • Likes Given: 275
@Rodal or anyone for that matter know how to calculate shawyer's design factor?
Shawyer's Df equation is attached. Have verified with Shawyer that it is correct.
Writing x0,x1,x2 for the 3 lambdas, this can be expressed as
D = [(1-a)/sqrt(a)] * [sqrt(b)/(1-b)], where a = x1/x2, b = x02/(x1*x2)
Notice that D is a separable function of a,b and so can be readily optimised by inspection.
Dmax -> infinity when a->0 and/or b->1.
Do other relations between x0,1,2 exist to prevent D becoming infinite?
Obviously if a > 0 and b < 1 then Dmax when a is min, b is max
I would like to know the maximum theoretical value of Df.
Based on the expression I derived above, it corresponds to
- a min, i.e. (x1/x2) min
- b max, i.e. x02/(x1*x2) max.

What are the values of aMin and bMax, and why?
I stopped looking at the Design Factor as a serious formula as soon as I learnt from TheTraveller that it uses the "cut-off" frequency for an open waveguide of constant cross-section, as it is known that tapered waveguides and cavities do NOT have rigid cut-off.  Only constant cross-section waveguides have a rigid cut-off condition.
Fair enough. So what formula (if any) can you recommend for calculation of the thrust-to-power ratio?
The one of Dr. Notsosureofit, a formula by a Ph.D. in Physics, knowledgeable of General Relativity and Radar, and a formula that is explicitly dependent on the mode shape:

http://emdrive.wiki/@notsosureofit_Hypothesis
Thanks and I took a look at this. Taken at face value it predicts that, in order to maximise the thrust/power ratio, one requires that independently:
- Ds/Db to be minimum
- Db to be minimum
- L to be minimum
even after accounting for the frequency scaling per Appendix I.
The thrust predictions seem roughly in line with the experimental data.
k = F/P seems to be, for the ranges graphed, about 3*10-7 N/W (about 300 uN for 1000 W).

I'm looking for a way to get much higher F/P values. I've indicated how this can be done per this formula.
I would welcome some concrete suggestions.

[A couple of notes on this derivation:
1. In Appendix I the n factor due to L is omitted (but the scaling conclusion is correct anyway)
2. Whenever I read about "accelerated photons" my toes curl up]
Here again is the Yang geometry. A reminder that it is top of the class in thrust-to-power ratio. And lo and behold, they've followed the guidelines I've highlighted above:

- Ds/Db to be minimum
- Db to be minimum
- L to be minimum

with the exception of the final 'L' constraint.
Coincidence?

In any case, it looks like you get the best bang for the buck when the small and large diameters are made as different as possible, and the large diameter is made as small as possible.


Offline birchoff

  • Full Member
  • **
  • Posts: 272
  • United States
  • Liked: 125
  • Likes Given: 95
It's a shame that Tajmar, being Director of an institute with access to fine equipment and trained staff, did such a shoddy job.
 
1. Not self-contained
2. Not correctly impedance matched
3. Thermal effects not analysed
4. Bloody great hole in the side of the frustum.

He's a good theoretician, but struggles as an experimenter. We all have our strengths and weaknesses.

I would beg you to be more precise about (3). Tajmar did account for thermal effects and did alot to remove them from their measurements. In the Ambient air balance beam measurements they wrapped the entire thing in glass wool placed it in a sealed aluminium box which was stuffed with more glass wool to prevent thermal air currents.

In the torsion balance test the whole chamber was evacuated. And since there was an adjustable hole on the narrow end I doubt it was air tight which means the entire frustum would also have been evacuated.

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
We continue the program started with posts
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1403629#msg1403629
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404000#msg1404000
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404004#msg1404004
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404005#msg1404005
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404006#msg1404006
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404754#msg1404754
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1404783#msg1404783
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1406306#msg1406306
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409278#msg1409278

showing the stress (force/unitArea) on the small and the big Base for what is believed to be Yang's EM Drive geometry:  (Db=0.201m,Ds=0.1492m,L=0.24m), with the dipole antenna previously used by aero for the RFMWGUY and the Yang/Shell geometry, but this time located near the small end in the transverse direction: dipole 0.058 m long perpendicular to the axis of axi-symmetry x of the truncated cone.

The stress tensor σxx (*) component is obtained using Wolfram Mathematica ( http://www.wolfram.com/mathematica/ ) , post-processed from the transient Finite Difference (using Meep) solution for RF feed ON.

The stress component σxx  has a very low amplitude at the Big Base. 
In order to compare the stresses to the previous cases of Yang/Shell, I have shown all plots to the same numerical scale. 
The Finite Difference mesh identical to the one used for the previous Yang/Shell models.


______________________________






(*)  (we denote by σxx= T11 the contravariant component of the tensor acting along the longitudinal direction "x" of the EM Drive, normal to the the plane yz having normal x, where direction "1" is "x")

(**) For the copper diamagnetism is assumed such that the magnetization M is assumed proportional to the applied magnetic field such that for free space it is assumed that M is zero in free space in the relationship 

(***) The Stress calculations are for an Input Power of 43 Watts (similar to the value used by NASA in some of their runs).  The Stress values are proportional to the Input Power, so for example, if the Input Power were 860 Watts, that means that the calculated values for Stress are 860 Watts/ 43 Watts = 20 times greater than shown in the plots.    In other words, for 860 Watts InputPower, the values for Stress in the plots need to be multiplied by a factor of 20.
« Last Edit: 07/28/2015 02:32 PM by Rodal »

Offline Rodal

  • Senior Member
  • *****
  • Posts: 5895
  • USA
  • Liked: 6045
  • Likes Given: 5325
The stress at the small base.  It shows a transverse magnetic TM11 m=1, n=1 mode shape, same mode shape as previously shown.  Compare with this:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1406307#msg1406307
and

http://forum.nasaspaceflight.com/index.php?topic=37642.msg1409281#msg1409281
« Last Edit: 07/28/2015 03:02 PM by Rodal »

Tags: