Author Topic: EM Drive Developments - related to space flight applications - Thread 5  (Read 729441 times)

Offline TheTraveller

...
How much Force do you need a cubesat EMDrive to deliver? Knowing the Force desired then the needed Rf watts can be calculated. Your job to deliver those Rf watts and ensure there is enough primary power available. Can design to many dimensions knowing the Rf drive freq, which will need to real time track lowest VSWR or lowest reflected power to achieve and hold resonance. I assume it needs to fit inside 1 cube being 100mmx100mmx100mm?
To fit in a 12u cubesat, large dia can be up to 20cm with length up to 36cm.  To accelerate a 10Kg cubesat at 10mm/s would take...what... 100mN?  I'm guessing on the math here - too late at night - I'm probably off by some powers of 10...  We can give you a KW for several minutes once per orbit, only limit is how hot the batteries get and how far we discharge them.  More than a 20% depth of discharge will limit their life, but this is probably a limited life test anyway (not a multi-year mission) so we can maybe run them harder and/or pack in more batteries to give us more instantaneous power...

While this amp is a bit big, the data is still interesting:

http://www.cpii.com/docs/related/61/13%20KW%20S%20Band%20GaN%20Power%20Amplifier1.pdf

100us long 1.2kW S band Rf pulses every 1ms should get your cubesat moving very well. Pwr supply load is 400Ws.

With a unloaded frustum Q of 100,000 and 1.3kWs of Rf, Force generation could be around 0.5N or 500mN (at 10kg mass that is 50mm/sec of acceleration) for 100us duration, repeating every 1ms.

100us pulse duration should be fine as the frustum fill time, being TC = (unloaded Q / (2 Pi Freq) sec x 5, is 32us. So plenty of time to fill the frustum, obtain a good resonant standing wave and achieve stable Force generation.

Don't get too hung up on the pulse lengths. In Roger's latest patent application, he excites the frustum for only 20% of 1 TC. Or in this case an excitation pulse of 1.3us.

In the 3rd attachment what is exciting is the Force generation area under the power applied time period versus the Force generation area under the power not applied time period.

Another bread crumb trail to happily follow.
« Last Edit: 10/31/2015 02:48 AM by TheTraveller »
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Offline Mezzenile

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Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

Offline A_M_Swallow

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Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

As the EM Drive does not use fuel it does not have a Delta-V limit. It is limited by sun light and the lifetime of the components. For deep space missions sunlight can be replaced by electricity from a nuclear source.
« Last Edit: 10/31/2015 04:18 AM by A_M_Swallow »

Offline Mezzenile

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As the EM Drive does not use fuel it does not have a Delta-V limit. It is limited by sun light and the lifetime of the components. For deep space missions sunlight can be replaced by electricity from a nuclear source.
You right, but I was more thinking to a comparison in term of thrust performance between the different concepts.
« Last Edit: 10/31/2015 04:40 AM by Mezzenile »

Offline Corlock Striker

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As the EM Drive does not use fuel it does not have a Delta-V limit. It is limited by sun light and the lifetime of the components. For deep space missions sunlight can be replaced by electricity from a nuclear source.

If it actually works, which has yet to be definitively proven at this point.  There is a lot of evidence that makes it seem likely that something is happening.  However, Shawyers is the only one that seems to have generated significant thrust, as he hasn't published any papers detailing the specs of his drive.  EagleWorks perhaps has recently generated a decent amount of thrust, but they have not yet released those numbers.  All other publically released released numbers are rather small.  They suggest that something may be happening, but may also be due to thermal effects or other artifacts.  We simply don't know yet.  And if it is working, we still don't know why it works.

Although, I did just read an article today about a scientist that published a paper to a site were scientists can upload papers to get them peer reviewed by other scientists claiming that he may have found evidence of the existence other dimensions in the cosmic background radiation.  So, the idea that the EmDrive might somehow be tapping into other dimensions might not be all that far fetched, if they do actually exist.  His paper states that that is only one possible explanation for his findings, and for some of the signatures he found existing phenomena were more likely.  Still, kind of cool.

Offline TheTraveller

Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

BIT-3 thrust is rated at 1.2mN thrust. To match that a properly designed EMDrive and resonance freq tracking system, operating around 2.45GHz, would need say 3Ws of Rf. At 20% Pwr to Rf efficiency that is a power supply load of 15Ws.

By using higher freq Rf, the size and mass of the EMDrive could be reduced quite a lot, without impacting mN Force generation. In fact the Force generation could improve around 50% because the smaller size would allow a more optimal big to small end diam ratio, generating a higher Df and higher mN generation per the same amount of Rf watts.
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Offline TheTraveller

However, Shawyers is the only one that seems to have generated significant thrust, as he hasn't published any papers detailing the specs of his drive.

This is the current EMDrive score board, which doesn't include Iulian's, Dave's nor Paul's positive results.

So far the published record Force generation is held by the Chinese researchers at 720mN.

Roger has released more than ample data to allow replication of his early 2002 - 2009 work. His bread crumbs are there. Just waiting for eager minds to follow them and learn how to bake the "Shawyer Effect" cake.
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Offline Mezzenile

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How to get rid of buoyancy ?

1- In fact we don't need a vacuum chamber around the EMDrive cavity to avoid buoyency effect. It is sufficient to establish the vaccuum inside the cavity and to use a radio transparent quartz waveguide window at the interface with the magnetron.
Of course this would require strong enought cavity design to resist to external atmospheric pression !

2- An other possibility to study could be to fill the whole RF cavity with a dielectric similar o the PTFE used in the GORE RF coaxial cables.

Offline TheTraveller

Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

Any idea what the BIT-3 thruster, complete and ready to fly package costs to buy retail?
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Online meberbs

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No they don't bounce. They get absorbed by the end plate and reemitted.

If you are EM trained then please explain to me how a 8.8mm diameter waveguide can propagate a 4.12GHz EM wave? In fact neither can the big end at 3.52mm diameter propagate that EM wave. So both ends of the proposed Egan cavity are well below cutoff and can NOT propagate a 4.12GHz EM wave, yet he claims resonance.

...

BTW please show me where Egan is EM trained or experienced? All I can find is he holds a BS in Maths and is a sifi writer and programmer. What amazes me is despite Egan having apparently no microwave training nor experience, so many EMDrive deniers jumped on this paper and totally ignored his apparent lack of credibility in the black arts of microwave waveguide physics.

Absorbed and reemitted is exactly what happens when you do something like shine UV light on a fluorescent material. This is noticeably different from what happens when you shine light on a metallic surface (mirror). A more technically accurate answer for RF waves in a metallic cavity discusses induced currents and charge distributions on the surface of the conductor.

Since you continue to insist on using equations derived to solve a different problem than a truncated spherical cone, rather than exact results such as those given be Egan, I'll do an approximate calculation to help demonstrate that Egan's results are reasonable. I will calculate the cutoff of a cylindrical waveguide with a radius that matches the large end of the cavity Egan did his calculations for. I do not know where you got 0.00352 m as the diameter of the large end since that is smaller than the diameter you stated for his small end. Just using the straight cross section, the radius is 0.1 m * sin(20 degrees) = 0.0342 m. Using the TE11 mode for a cylindrical waveguide, you have a cutoff of 3e8 / (2*pi*0.0342 / 1.841) = 2.57 GHz. This is mostly meaningless, but does indicate that 4.12 GHz isn't an unreasonable frequency for this cavity size.

Knowledge of Maxwell's equations, the boundary conditions for EM fields in the presence of a conductor and a degree in Math is plenty of background for calculating the resonance modes. I have taken advanced courses in Electrodynamics and can find nothing wrong with the methods he used. I will ask you again to state where his math is wrong if you wish to disagree with his results.


According to your logic, no resonances could exist at all in a cone shaped cavity. That is an incorrect claim, easily testable by experiment. ...

I think you missed the key work efficiently in TT's post. Yes of course you can get any shape to resonate, but to resonate with high quality and low losses we want to minimize the evanescent decay. When wave bounces off an opening because its wavelength is too large to fit, some energy will still propagate into the opening and decay exponentially.
I believe what he and Shawyer are getting at is we should have each side of the resonator be above the cutoff, not that we have to.

Correct.

The only way to achieve a high Q is to ensure the small end operates above cutoff. If your end plates are spherical this also encourages the EM waves to form matching spherical wave fronts, which reduces significantly bounce phase distortion and also reduces side wall radiation pressure to almost nothing.

Q values for the modes on Egan's page are calculated near the bottom of his page. It only makes sense to talk about Q values for real conductors with finite conductivity. His calculations assume a perfectly shaped cavity driven by the perfect frequency, but show the maximum value you could expect to obtain using a copper cavity for each mode. Still, all of these modes have reasonably large theoretical Q values.

When discussing the resonance for a perfect conductor, it does not make sense to claim that energy is lost to evanescent decay. You may see an decay effect with little field strength near the small end, but all energy is reflected perfectly.

Your description of how you picture the waves propagating in the cavity is irrelevant, since it has no solid basis. Egan calculated the exact equations that describe the fields inside the cavity based on Maxwell's equations, and these show that your description is inaccurate. They also show that there is significant force on the side walls. This is how electromagnetism works. If you think these results are wrong, you need to find a mistake in Greg Egan's math, or you need to do your own full derivation starting with Maxwell's equations, and then compare to find why his result differs from yours. (Greg Egan actually starts with the wave equation, which is easily derived from Maxwell's equations, so it doesn't make a difference)

Offline Mezzenile

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Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

Any idea what the BIT-3 thruster, complete and ready to fly package costs to buy retail?
The iodine thruster should very price competitive versus state of the art argon thruster as it does not require to accomodate on board the satellite a high pression tank to store the propelant. The accomodation of such a tank on a small satellite can be a burden (mass, security aspects, testing ...).
Argon has still the advantage over iodine, having a very low chemical activity, to produce minimal erosion where the plume is in contact with the thruster or satellite structure.

Offline TheTraveller

...

My big end diameter was 35.2mm and the small end diameter was 8.8mm with end plate spacing of 75mm. See attached.

TE11 cutoff for the big end is 4.99GHz and for the small end is 19.96GHz.

Your TE11 cutoff equation is incorrect as you used the diameter and not the radius. For TE11 mode cutoff it is (1.841183781341 * c) / (2 * Pi * radius). http://www.rfwireless-world.com/calculators/circular-waveguide-cutoff-frequency-calculator.html and as attached.
« Last Edit: 10/31/2015 05:45 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 TheTraveller

Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

Any idea what the BIT-3 thruster, complete and ready to fly package costs to buy retail?
The iodine thruster should very price competitive versus state of the art argon thruster as it does not require to accomodate on board the satellite a high pression tank to store the propelant. The accomodation of such a tank on a small satellite can be a burden (mass, security aspects, testing ...).
Argon has still the advantage over iodine, having a very low chemical activity, to produce minimal erosion where the plume is in contact with the thruster or satellite structure.

My interest in the BIT-3 thruster price point was serious as I'm setting up to move into commercial EMDrive production. If there is sufficient commercial interest, it would be possible to produce a 2mN EMDrive that would fit in a 1U cubesat form factor and draw around 15Ws of power.

So any feedback on the price point of 2mN thrust equivalent ion drives would be of genuine interest.

Design spreadsheet confirms it should be possible to build a X band EMDrive frustum that would fit inside a 10x10x10cm 1U cubesat module and generate 2mN of continual thrust using 15Ws or less of power. Might even be able to electronically vector the thrust angle and provide 2 axis directional control.
« Last Edit: 10/31/2015 06:50 AM by TheTraveller »
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Offline SeeShells

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Pesentation of a Iodine Ion Thruster for CubeSat with its main performances. Comparison with EMDrive or Woodward thruster would be instructive.

Any idea what the BIT-3 thruster, complete and ready to fly package costs to buy retail?
The iodine thruster should very price competitive versus state of the art argon thruster as it does not require to accomodate on board the satellite a high pression tank to store the propelant. The accomodation of such a tank on a small satellite can be a burden (mass, security aspects, testing ...).
Argon has still the advantage over iodine, having a very low chemical activity, to produce minimal erosion where the plume is in contact with the thruster or satellite structure.

My interest in the BIT-3 thruster price point was serious as I'm setting up to move into commercial EMDrive production. If there is sufficient commercial interest, it would be possible to produce a 2mN EMDrive that would fit in a 1U cubesat form factor and draw around 15Ws of power.

So any feedback on the price point of 2mN thrust equivalent ion drives would be of genuine interest.

Design spreadsheet confirms it should be possible to build a X band EMDrive frustum that would fit inside a 10x10x10cm 1U cubesat module and generate 2mN of continual thrust using 15Ws or less of power. Might even be able to electronically vector the thrust angle and provide 2 axis directional control.
Sure, a phased array would do it.

Online meberbs

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Your TE11 cutoff equation is incorrect as you used the diameter and not the radius.

Greg Egan is giving the angle of the cone in spherical coordinates. Note that both walls in this diagram are labelled with the angle, which is measured from the z axis. The full angle between opposite walls would be 40 degrees. Your numbers for the diameters are off by roughly a factor of 2. Again, approximation methods such as this don't matter anyway if you can calculate the exact solution as Greg Egan did. It just confirms his answers are reasonable order of magnitude.

Offline VAXHeadroom

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Quote
Biggest issue I see is sourcing a low mass and highly efficient min 200W solid state Rf amp AND dealing with the 800Ws of waste heat. Maybe better to go for a lower output power Rf amp that can run 24/7, instead of doing short bursts of acceleration.

Suggestion from the peanut gallery:

use the waste heat to generate electricity.  (thermocouples?)   Won't get anywhere near unity, but might offset the power bill some.

It works, but the efficiency is so low it's not worth the mass penalty.
Emory Stagmer
  Executive Producer, Public Speaker UnTied Music - www.untiedmusic.com

Offline Prunesquallor

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...
How much Force do you need a cubesat EMDrive to deliver? Knowing the Force desired then the needed Rf watts can be calculated. Your job to deliver those Rf watts and ensure there is enough primary power available. Can design to many dimensions knowing the Rf drive freq, which will need to real time track lowest VSWR or lowest reflected power to achieve and hold resonance. I assume it needs to fit inside 1 cube being 100mmx100mmx100mm?
To fit in a 12u cubesat, large dia can be up to 20cm with length up to 36cm.  To accelerate a 10Kg cubesat at 10mm/s would take...what... 100mN?  I'm guessing on the math here - too late at night - I'm probably off by some powers of 10...  We can give you a KW for several minutes once per orbit, only limit is how hot the batteries get and how far we discharge them.  More than a 20% depth of discharge will limit their life, but this is probably a limited life test anyway (not a multi-year mission) so we can maybe run them harder and/or pack in more batteries to give us more instantaneous power...

I'm not sure where you are going here, mm/s is a velocity, not an acceleration.

I have made my concerns about an amateur space test known previously.  In my opinion, the disturbing orbital forces, thermal and EM effects on a satellite this small may not be appreciably smaller than the effects folks are trying to eliminate in the lab.

What would you conclude from a cubesat test that doesn't give detectable results?
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Offline VAXHeadroom

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...
How much Force do you need a cubesat EMDrive to deliver? Knowing the Force desired then the needed Rf watts can be calculated. Your job to deliver those Rf watts and ensure there is enough primary power available. Can design to many dimensions knowing the Rf drive freq, which will need to real time track lowest VSWR or lowest reflected power to achieve and hold resonance. I assume it needs to fit inside 1 cube being 100mmx100mmx100mm?
To fit in a 12u cubesat, large dia can be up to 20cm with length up to 36cm.  To accelerate a 10Kg cubesat at 10mm/s would take...what... 100mN?  I'm guessing on the math here - too late at night - I'm probably off by some powers of 10...  We can give you a KW for several minutes once per orbit, only limit is how hot the batteries get and how far we discharge them.  More than a 20% depth of discharge will limit their life, but this is probably a limited life test anyway (not a multi-year mission) so we can maybe run them harder and/or pack in more batteries to give us more instantaneous power...

I'm not sure where you are going here, mm/s is a velocity, not an acceleration.

I have made my concerns about an amateur space test known previously.  In my opinion, the disturbing orbital forces, thermal and EM effects on a satellite this small may not be appreciably smaller than the effects folks are trying to eliminate in the lab.

What would you conclude from a cubesat test that doesn't give detectable results?
I have made my credentials known, I'm not an amateur, and this would not be an amateur test.  The change of velocity resulting from thrust causes the ground to see a Doppler shift in the rf carrier, detectable down to a deltaV of single digit mm/s.  This change needs to occur in a pretty short period of time (minutes) to insure a significant signal to noise ratio in the rf shift (if it happens too slowly it can look like thermal drift of the S-Band amplifier).  This means all the hard part (large, expensive) of the test and measurement equipment is on the ground.  A second means of measurement is using NASA Goddard's laser measurement system - all we really have to do for that is provide a retro-reflector on the spacecraft.  They can do both position and velocity measurements out to the moon (they do this for LRO all the time), but I'll have to find out what their measurement and resolution limits are...
Emory Stagmer
  Executive Producer, Public Speaker UnTied Music - www.untiedmusic.com

Offline TheTraveller

Vax,

A X band 1U EMDrive thruster delivering 2mN of thrust for 12W draw is doable. Depending on the power available the Rf Watts can go up as would the thrust.

Do you need constant or short term thrust?
What is the desired mN thrust?
What is the mass budget for the thruster?
How much power can you supply to meet the thrust requirements?
Potentially the thrust may be able to be vectored +-10 deg in 2 axis. Is this helpful?
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Offline Prunesquallor

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How much Force do you need a cubesat EMDrive to deliver? Knowing the Force desired then the needed Rf watts can be calculated. Your job to deliver those Rf watts and ensure there is enough primary power available. Can design to many dimensions knowing the Rf drive freq, which will need to real time track lowest VSWR or lowest reflected power to achieve and hold resonance. I assume it needs to fit inside 1 cube being 100mmx100mmx100mm?
To fit in a 12u cubesat, large dia can be up to 20cm with length up to 36cm.  To accelerate a 10Kg cubesat at 10mm/s would take...what... 100mN?  I'm guessing on the math here - too late at night - I'm probably off by some powers of 10...  We can give you a KW for several minutes once per orbit, only limit is how hot the batteries get and how far we discharge them.  More than a 20% depth of discharge will limit their life, but this is probably a limited life test anyway (not a multi-year mission) so we can maybe run them harder and/or pack in more batteries to give us more instantaneous power...

Quick analysis suggest the 20cm big end limitation reduces the Df ( F = (2 Df unloadedQ P) / c ) quite a bit. But working on that limitation I get a highly optimised small end of 14.95cm and length of 15.07cm (mode TE011 @ 2.45GHz), with spherical end plates, using a 20% solid state amp conversion efficiency to Rf and 1kW power input could deliver, at a conservative unloaded Q of 50,000 (25,000 as measured loaded Q) around 40mN, generating say 4mm/sec acceleration with a 10kg mass.


Let's get our physics right. 40 mN acting on a 10 kg object would generate an acceleration of 4 mm per second per second. So assuming 1) you could hold spacecraft attitude, and 2) other forces on the satellite are much less than 40 mN your velocity would change (for example) 4 mm per second if you could hold 1 kW for one second. Is that detectable?
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