Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1799013 times)

Offline zellerium

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On the topic of magnetrons,

although they aren't a perfect rf source, they are the most feasible option for anyone doing a DIY experiment. Getting a 1 kW source for $20 is a bit unbelievable when you consider renting a 500 W amp for $3,000/month. There are cheaper methods of obtaining a high power amp, but from my experience they seem unreliable.
 
Yes, the power isn't evenly distributed and the BW is ~60 MHz, but this can be sharpened for the relatively cheap price of metal to create intermediate resonant cavity and high power coax. And keeping the core temperature steady should prevent frequency drifting, correct?  So IMO, using low power, narrow BW amps is going to make it more difficult to get a 5 sigma deviation from noise unless you have something equivalent to a low-thrust torsion pendulum.

We have recently been dealing with the issue of replicating a magnetron output using the VNA. So today I cut open magnetron to expose the coupling wire used to transfer energy from the resonant cavity to the antenna. It looks like the antenna used consists of the coupling wire pinched in a copper tube, housed in a stainless steel cylindrical cavity.
 
To replicate the antenna, we're thinking of sacrificing another magnetron the cut out the full length of coupling wire, and soldering a BNC-to-wire connection. Then we can approximately simulate a magnetron output and measure reflected power to determine positions of resonance for our adjustable, partially loaded cavity.   

Also, I noticed many people are opting for a laser measurement system. I think this method is ideal, especially if you can track the laser effectively. We were able to borrow a PSM2-10 Position Sensing Module which apparently has 0.0000 mm resolution. However, we don't know how much noise will be present so our actual resolution is TBD.

Kurt


 

Offline ElizabethGreene

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Just found this: http://www.cpii.com/docs/related/37/VA936-VKC7936%20C-Band.pdf

Question: What is exactly the "instantaneous 40 MHz bandwidth at –1dB points"?

A Klystron is an Electrical, Magnetic, and Mechanical Device.  You mechanically adjust the resonant cavity center frequency by turning a knob.  The optional controller module does this with optical encoders and electric motors.  You feed a signal into the Klystron and it amplifies it.  The peak of the amplification is at the center frequency.  The -1db bandwidth is the difference in frequency from the center frequency where the signal is amplified at -1db from the peak.

i.e. I put in a constant 1 dbm signal from an oscillator.  At the center frequency I get out +40db.  If I shift my oscillator away from the center frequency by the amount of the instantaneous bandwidth I'll get a +39db signal.

I trivialize the device adjustment by calling it a "knob".  I've read the process, and a portion of it appears to be non-trivial parts of magic and luck.

Online Rodal

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Continuing from messages:

http://forum.nasaspaceflight.com/index.php?topic=37642.msg1400994#msg1400994
http://forum.nasaspaceflight.com/index.php?topic=37642.msg1399795#msg1399795

I have calculated,  from aero's csv files,the Poynting vector component in the longitudinal direction (the components in the transverse direction are self-cancelling, since they point in opposite directions away from the axis) at the following location:

*the location of the local maximum on the wave-pattern immediately downstream (towards the big base) from the antenna location: it is column (x location) 149.  Transverse location (either y or z): 132.5

and calculated its time fluctuation for the time steps given by aero: TS03 through TS13 (11 Meep time slices) in the csv files.

 for the above mentioned cycles, with a couple of nonlinear fits (described below, and in detail, in the images below).

ANALYSIS  (Based on these data points available and the input information detailed below):

1) The best frequency fit of the Poynting vector is 2*2.40 GHz, or two times the frequency of the electromagnetic field which is 2.40 GHz, with a very high r squared: R^2 =   0.999964.  A fit for frequency of the Poynting vector of 2*2.45 GHz, or two times the frequency of the electromagnetic field of 2.45 GHz corresponds to a still very high but lower  r squared R^2 = 0.998513.  This is true for both nonlinear fits:  both of them give a better fit for a frequency of 2.40 GHz than for 2.45 GHz.
 
This is in accord with what we expect from Maxwell equations: the frequency of the Poynting vector should be twice the frequency of the electromagnetic field.

2) The linearly increasing  time-average + exponentially increasing sinusoid model gives a better fit than the exponentially increasing sine and cosine model with constant time average.  The r squared values are: R^2 = 0.999964 as compared to  R^2 = 0.997876, respectively.

3) Non-exponentially increasing models do not fit the data well (as it is evident from just looking at the data points).

4) Although it would (obviously) be invalid to extrapolate data, particularly with so few data points, I extrapolate the model fits to the initial steps and 100 time slices into the future to dramatically show the difference between the better fitting model with linearly increasing time-average, as compared to the model with constant time average.

5) Obviously we need to plot many more data cycles in the past history of the Meep model to extract any conclusions.  For example, the exponential increase in amplitude observed during these 11 time slice steps could be due to amplitude modulation phenomena rather than due to an exponentially increasing fluctuation from the start.  We need to get many more steps to be able to tell one from the other, or other possible explanations.

6) From the SI unit conversions shown below, the Meep model represents an extremely small value of the Poynting vector at the extremely early time being shown (orders of magnitude smaller time than the time lengths of the EM Drive tests).  Although the exponentially increasing magnitude of the Poynting vector may look dramatic to the eye, it is still orders of magnitude smaller than needed to produce the measured values of force and heat transfer.  The Meep time solution would need to be further advanced and the Poynting vector would need to further increase exponentially several orders of magnitude to meet the reality of measured values of heat and input power.

See the images attached below and the accompanying statistical assessments of the nonlinear fits.
________________________________________________________
NONLINEARLY FITTED MODELS:

a) linearly increasing time-average + exponentially increasing sinusoid

b) exponentially increasing sine and cosine functions

DATA FITTED:

Poynting Vector Component in Longitudinal "x" direction at x=149 (wave just downstream from antenna towards big base) for time steps 03 through 13 discussed in this post:  http://forum.nasaspaceflight.com/index.php?topic=37642.msg1399795#msg1399795

STATISTICAL TABLES:

R^2

Fitted model coefficient statistics:
Standard error
t-statistic
P-Value

________________________________________________________
PLOTS:

HORIZONTAL AXIS: Time, in Meep Time Slice Units

VERTICAL AXIS : Poynting Vector Component in Longitudinal "x" direction at x=149 (wave just downstream from antenna towards big base), in Meep Units

________________________________________________________

SI UNITS

To get SI Units from the graphs and equations in Meep units:

1) TIME:  Multiply Meep Time Slice "t" in the horizontal axis and in the formulae by the following factor:

((Total Meep Time)/(#Time Slices))*((Length Scale Factor)/(Speed of Light in Vacuum)) =
                                                                                                           =((13.054)/(320))*((0.3)/(299792458))
                                                                                                           =4.082199*10^(-11) seconds/timeSlice


2) POYNTING VECTOR:  Multiply Meep Poynting Vector Component in Longitudinal x direction in the vertical axis and in the formulae by the following factor:

1/(((Length Scale Factor)^2)*(Speed of Light in Vacuum)*(Electric Permittivity of Vacuum))
                                                                  =1/((0.3^2)*299792458*8.85418717*10^(-12))
                                                                  =4185.892372090  watts/m^2

ASSUMPTIONS: the validity of the following data:

Number of time slices for the total run = 320
Number of Meep time units for the total run = 13.054
Meep Length Scale factor= 0.3 meters
Meep Current (Io) = 1
« Last Edit: 07/09/2015 02:54 PM by Rodal »

Offline SeeShells

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-I've been unable to find an old varian catalog to decode the part numbers.
Just found this: http://www.cpii.com/docs/related/37/VA936-VKC7936%20C-Band.pdf

Question: What is exactly the "instantaneous 40 MHz bandwidth at –1dB points"?
Believe this refers to 1db bandwidth of signal, meaning signal is broadband, 40 mhz wide unmodulated. What is missing here is spurious and harmonic specs. look for a spurious spec...

Ok. Should this "40 MHz instantaneous bandwidth" be a problem, other CPI klystrons are more compact and have a narrower instantaneous bandwidth, like those from their Communications & Medical Products Division:
- VKS2200 Series (bandwidth 8-9 MHz / power 1000-2500 W / S-band freq. 1.700-2.660 GHz )
- VKS2509 Series (bandwidth 8-9 MHz / power 2000-2500 W / S-band freq. 1.700-2.230 GHz)

Those S-band klystrons seem ideal for EmDrive research: compact form factor, very narrow band, high power (kilowatts) and operating frequency similar to 2.45GHz oven magnetrons, so cavities built for them are about the same size.

CPI also makes higher power (10 to 500 kW) S-band CW klystrons in their Microwave Power Products Division. A bit high for DIYers…
They also make pulsed versions. So far I'm not aware of any EmDrive test using a pulsed MW source instead of CW. I saw that for big high-end klystrons, output power even scales up to megawatts!

I am going with dirty power first. There are many combline bp filters, but at this stage, maybe its the chaos of em that makes it tick...too early to say for sure imho.
Sure. Paul March talked about that possibility. But Shawyer also said the dirty magnetrons are good for flat end plates, but high-Q cavities with spherical end plates require a cleaner source of microwaves.
Note: see pic.
Busy BBL...

Offline watermod

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For rfvp in response to Post #3648
...
The generic DIY-er can easily and cheaply make or have made a frustum projected to resonate at 2.45 GHz.

Who's sanguine now? Not I on that point. I don't do metal fab well. Tried to interest some mechanically-inclined local hackers here around Chicago a month back, none seemed enthused.

Can he/she design and build the circuitry necessary to phase lock it to an external reference or injection lock it to the frustum?  Or mechanically lock the frustum to the magnetron?  When hooked to the frustum, which of the many resonant frequencies does it lock to?  How does the DIY-er know?  If no thrust is detected with the first mode, how does he test the other resonant modes?  If the magnetron is injection locked to the frustum how does the experimenter tune the magnetron out side the bandwidth of the thruster to determine if the thrust is related to resonance or an artifact of the test apparatus?

Like everything, one learns by reading, research, forums, trial and error, or has experience. I guess I take a lot for granted, having worked on mil and commercial radio systems in my career and having read a lot of ham-lit. As well as built a lot of home-brew gadgets.

Specifically, AFAIK particular modes are excited by hitting the right frequency and injecting either an E or H field with the appropriate method at the appropriate point, matching impedance. A mode diagram was posted here a while back. Then trial and error.

Servos can tune screws, insert dielectrics, piezo elements can warp thin metal plate.

To figure out the mode, one could insert steamed CoCl soaked paper, or let thermal paper blacken where the field is highest. Better would be to insert several tiny E or H probes going to mixers to determine the intensity and phase at interesting points.

I understand a magnetron can be tuned by the supply voltage, which needs to be stabilized without the ripple present in cheap oven supplies.

I was thinking pulsing the magnetron and measuring the vibration would be an interesting test, even if not conclusive and keep average power low, and the cavity from heating and detuning.

Put a tuning slug on the frustum.  How does that affect the Q and mode(s) of resonance?  How does the DIY-er know?   When tuning, what is the feedback to the person doing the tuning, so that he knows what is going on?

I suspect a tuning slug will adversely affect performance. They're little screws, not giant bolts though. I gather you know from looking at waveguides, gunplexers, TV tunners, radar detector, radios with cavity filters I've stripped, et. And books and trade journal articles, which I have somewhere that discuss why and how to use 2 screws for waveguide tuning. I forget.

For feedback a small field probe is apparently used by Nasa and Shawyer. I was thinking if a couple points are tapped, an FM discriminator (see Wikipedia) could be made that would servo mechanically tuning the frustrum, provided the loop-bandwidth was low-pass filtered to eliminate the (IMHO good) Sagnac-doppler shifts responsible for forces and motion from the bad thermal detuning.

Of course, the way to find out if that's right or effective to to test it.

I have a vague memory of fixing dozens of HF servo-driven antenna tuners decades ago, after air force techs mangled them. Some of the stuff I worked on I can still remember well enough to roughly draw a schematic of, like a UHF ultrasonic TDR pulser. But not those tuners.

I am just pessimistic as to their chances of success using a free-running magnetron and not as sanguine as you about the triviality of ‘just tune the frustum and allow the magnetron to injection lock to it ‘ solutions to the known problems.

I'm not sanguine at all. If I was, perhaps I'd be working on one and not chatting about it. However, if offered a choice between:

1. Use a cheap low-power ss amp and attempt to measure uN forces
2. Use an expensive and fragile high-power ss amp and measure low mN to high uN forces
3. Use a cheap, robust magnetron and measure mN forces

I would pick 3. YMMV.

The bad news would occur if thrust DIDN’T occur.  Especially if the frustum had a relatively high Q.  Would the principle be falsified?  Operating in the wrong mode?  Spectral output of the magnetron places little or no energy into the bandwidth of the frustum?  What next?

To falsify Shawyer, I suppose you need to replicate closely what he did and how he did it, same with NWPU or Nasa. I think one could tell by network analysis and sniffing spots in the resonator whether the right mode and energy is present.

(I’d use an external circulator just for fun though.). 

Yes, very nice to have. I hear they are non-trivial to design and build.

a TWTA/solid state amp driven by a precision sig gen—where you KNOW what is going on--sound much more attractive to ME.  YMMV.

Uh, yea. I wish I had a million dollars worth of test equipment and plumbing around, as I've had in the past. I got a frequency counter, grid-dip meters, diode detectors & stuff in my junk box. Oh, and perhaps I could use my wifi dongle as a spectrum analyzer, with some software.

As for SeeShells and the other builders:  I don’t know where you are geographically or what access you have to microwave stuff in your ‘day job’, but if you are in the Northern VA/DC/Suburban MD area I MAY be able to get you access to such desirable widgets as a vector network analyzer, precision sig gens (including vector signal generators that in addition to the standard am/fm/cw allow you to generate signals with an arbitrary output spectrum), power meters, spectrum analyzers, and power amplifiers in the 100+ watt range.   I am retired, but there is some possibility, considering the implications of real microwave thrusters, that my old employer would give me access, on a not to interfere basis, to any or all of the above.  I haven’t asked.  Yet.

Ah, must be nice. Too bad I'm around Chicago  :'(

If you are Chicago Suburban - Head to Workshop 88 on a Thursday night: http://www.meetup.com/workshop88/
They have electronics, milling machines, 3D printers and lots of experts - they are a hackerspace for the Chicago burbs.
Lots of old Lucent/Motorola/ATT etc. folks who might find your project interesting enough to help you.

Another web page for them: http://workshop88.com/
location http://blog.workshop88.com/about/

Other cities all over the world have hackerspaces that might be able to help you in locally.
https://wiki.hackerspaces.org/

Offline SeeShells

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Fascinating ...
Shell

Online WarpTech

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...

Show me please where dm/dt figures in there
...

Ein = Pin * t = c2 * integral(dm/dt)*dt
Eout = 0.5 * (m + integral(dm/dt)*dt) * v2

break even occurs when v = c, Ein = Eout

(1/m(t))*integral(dm/dt)*dt = (1/2)(v/c)^2 * 1/(1 - (1/2)(v/c)^2) = 1 at v = c.



Todd
Sorry, but I don't understand the final line of algebra. Please expand.

Offline deltaMass

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Fascinating ...
Shell
Fascinatingly totally unstable. This clearly does not represent reality, but instead we're looking at an artifact of numerical simulation.  I would be hard pressed to call this "useful data"

Offline deltaMass

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@Todd: This makes no sense to me. Yes, I understand the algebra. Surely Integral[dm/dt, t] should = m(t) at all times. If not, why not? What does this mean physically? What is this dm physically?
« Last Edit: 07/08/2015 11:48 PM by deltaMass »

Online WarpTech

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@Todd: This makes no sense to me. Yes, I understand the algebra. Surely Integral[dm/dt, t] should = m(t) at all times. If not, why not? What does this mean physically? What is this dm physically?

Physically? It is the rest mass of the energy being input. Your formula is not a closed system. There is an external energy source, Ein. When you ADD energy you are also adding mass. Okay, my bad.  In Eout, it should be (m(0) + dm(t)/dt), where m(0) is the rest mass of the system at t = 0.

EDIT: Since we didn't use relativistic mass or energy, just rest mass and rest energy, this solution is not relativistic, v can exceed c. However, what it says is that when the integral(dm/dt)dt = m(0), then v = c. I.e., if the rest mass is doubled by dm/dt, making it 200% or 2*m(0), then v = c. That is break even in a Newtonian scenario. Or, if 100% of the starting rest mass is expelled as propellant, then v = c, because there is no rest ass remaining to prevent it. I'm sure if relativistic mass and energy were used, it would also be limited to v < c.

The main point is, I've shown that it will never be over-unity.

Todd
« Last Edit: 07/09/2015 02:07 AM by WarpTech »

Offline mwvp

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For rfvp in response to Post #3648
...
Tried to interest some mechanically-inclined local hackers here around Chicago a month back, none seemed enthused.
If you are Chicago Suburban - Head to Workshop 88 on a Thursday night: http://www.meetup.com/workshop88/
They have electronics, milling machines, 3D printers and lots of experts - they are a hackerspace for the Chicago burbs.
Lots of old Lucent/Motorola/ATT etc. folks who might find your project interesting enough to help you.

Ya don't say?  ;) Lol.

Been there, done that. Small World! Great place, W88, lots of cool people and cool stuff. To bad the ones I contacted on the mailing list weren't into this stuff. I suppose I could try PS1 (Chicago) or some local Ham clubs or meetups. I'm an enabler more than an instigator.

I find the odds of this being a credible phenomena greater now that I've researched it a while. But I'm still reluctant to assure anyone their time and effort will be rewarded. For me, this is more of an aesthetic interest, in electromagnetics, physics and circuitry.

I have some deep-rooted psychic desire to prove mainstream cynics are wrong; their are still technical miracles, opportunities for significant progress in this world. Hardly a good reason to drag others into my strange proclivity.

Offline SeeShells

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Also, I noticed many people are opting for a laser measurement system. I think this method is ideal, especially if you can track the laser effectively. We were able to borrow a PSM2-10 Position Sensing Module which apparently has 0.0000 mm resolution. However, we don't know how much noise will be present so our actual resolution is TBD.

Kurt

I agree that the laser measurement is ideal. However, what I have been seeing, which was expected, is that over a large distance the size of the laser dot increases therefore reducing accuracy. Will have to cross that bridge of fixing that when I get there.

Also, to the other builders using the laser method, how long of a duration are your lasers able to stay on? Although, mine was cheap, I expected more than 30 minutes before switching batteries. Which is not ideal. >:(
I just spent an hour on the phone with a dear friend who is very creative and damn sharp who also had a hand in building a super collider.
He offered me several wonderful ideas (you are reading this I know, so thank you, you lurker ;) )
Instead of recording off the front side of a sheet of graph paper with the laser shining on it
mount the graph paper so the backside is open and then video the backside and set the camera to timeslice every set number of frames/second.
 
And as to the issues with the cheap laser shinning onto the paper 20 foot away, make a pinhole to shine the laser through from a thin sheet of stainless steel, just tried it and wow it does great, it gives me a very tiny pinprick of laser light!

See kiddie paint drawing

Shell


Offline rfmwguy

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-I've been unable to find an old varian catalog to decode the part numbers.
Just found this: http://www.cpii.com/docs/related/37/VA936-VKC7936%20C-Band.pdf

Question: What is exactly the "instantaneous 40 MHz bandwidth at –1dB points"?
Believe this refers to 1db bandwidth of signal, meaning signal is broadband, 40 mhz wide unmodulated. What is missing here is spurious and harmonic specs. look for a spurious spec...

Ok. Should this "40 MHz instantaneous bandwidth" be a problem, other CPI klystrons are more compact and have a narrower instantaneous bandwidth, like those from their Communications & Medical Products Division:
- VKS2200 Series (bandwidth 8-9 MHz / power 1000-2500 W / S-band freq. 1.700-2.660 GHz / classic version)
- VKS2509 Series (bandwidth 8-9 MHz / power 2000-2500 W / S-band freq. 1.700-2.230 GHz / Multi Stage Depressed Collector, more efficient version)

Those S-band klystrons seem ideal for EmDrive research: compact form factor, very narrow band, high power (kilowatts) and operating frequency similar to 2.45GHz oven magnetrons, so cavities built for them are about the same size.

CPI also makes higher power (10 to 500 kW) S-band CW klystrons in their Microwave Power Products Division. A bit high for DIYers…
They also make pulsed versions. So far I'm not aware of any EmDrive test using a pulsed MW source instead of CW. I saw that for big high-end klystrons, output power even scales up to megawatts!

I am going with dirty power first. There are many combline bp filters, but at this stage, maybe its the chaos of em that makes it tick...too early to say for sure imho.
Sure. Paul March talked about that possibility. But Shawyer also said the dirty magnetrons are good for flat end plates, but high-Q cavities with spherical end plates require a cleaner source of microwaves.
Hmmm, I guess it depends on your budget and interest in following another persons experiment. Seems we have a reported force using either methodologies. A wide band signal probably has fm or phase noise built in, a narrowband source will be cleaner. Which is best, could not say at these early stages. Pick one and run with it, just be safe with the hv and radiation.

Online Rodal

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...Fascinatingly totally unstable. This clearly does not represent reality, but instead we're looking at an artifact of numerical simulation.  I would be hard pressed to call this "useful data"
I would be hard pressed to call this comment "useful" as it refers to a post clearly marked "Under Construction"  containing an extrapolation well beyond the known data points.  And where the author of the post has posted a number of warnings to wait until finished for people to post negative comments.  Obviously it is not a question of reality as there are plenty of real unstable processes.  Anybody knows that extrapolations are by their nature subject to question, of course.

If you feel compelled to comment there are plenty of other things you can post on.  Please have the consideration to wait until the post is finished, and no longer with the "under construction" sign, to jump the gun and make your negative comments. 

Thanks for your courtesy.
« Last Edit: 07/09/2015 12:31 AM by Rodal »

Offline SeeShells

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Fascinating ...
Shell
Fascinatingly totally unstable. This clearly does not represent reality, but instead we're looking at an artifact of numerical simulation.  I would be hard pressed to call this "useful data"
All data is relevant, good, bad, or if it's what you want to see, or not. 

Offline demofsky

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Fascinating ...
Shell
Fascinatingly totally unstable. This clearly does not represent reality, but instead we're looking at an artifact of numerical simulation.  I would be hard pressed to call this "useful data"
All data is relevant, good, bad, or if it's what you want to see, or not.

Thanks for this Shell.  It helped me realize that while some folks like Shawyer believe they have this device nailed down most of us are still in the characterization stage.  All of these builds and theories are really diagnostic more than definitive.  This thread is really about brainstorming to identify the search space.  It is really that early in the process.

Offline DrBagelBites

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Also, I noticed many people are opting for a laser measurement system. I think this method is ideal, especially if you can track the laser effectively. We were able to borrow a PSM2-10 Position Sensing Module which apparently has 0.0000 mm resolution. However, we don't know how much noise will be present so our actual resolution is TBD.

Kurt

I agree that the laser measurement is ideal. However, what I have been seeing, which was expected, is that over a large distance the size of the laser dot increases therefore reducing accuracy. Will have to cross that bridge of fixing that when I get there.

Also, to the other builders using the laser method, how long of a duration are your lasers able to stay on? Although, mine was cheap, I expected more than 30 minutes before switching batteries. Which is not ideal. >:(
I just spent an hour on the phone with a dear friend who is very creative and damn sharp who also had a hand in building a super collider.
He offered me several wonderful ideas (you are reading this I know, so thank you, you lurker ;) )
Instead of recording off the front side of a sheet of graph paper with the laser shining on it
mount the graph paper so the backside is open and then video the backside and set the camera to timeslice every set number of frames/second.
 
And as to the issues with the cheap laser shinning onto the paper 20 foot away, make a pinhole to shine the laser through from a thin sheet of stainless steel, just tried it and wow it does great, it gives me a very tiny pinprick of laser light!

See kiddie paint drawing

Shell

After searching through my scraps of electronics, I have solved my power issue by pretty much dismantling the darn thing and strapping it to an arduino. This solves two problems, actually: with a simple script I can control the laser on/off from outside of the room and power is consistent. So, win/win!

As for tracking the laser point on the wall, I was thinking of using OpenCV. I have some experience using it, and I think it will do a fine job of it. Also, with OpenCV, I'd be able to have real time calculations being done to determine any spikes/changes/etc.

The pinhole idea, now that is a clever one. I'll have to implement that as soon as I can! :)

Offline rfmwguy

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On the topic of magnetrons,

although they aren't a perfect rf source, they are the most feasible option for anyone doing a DIY experiment. Getting a 1 kW source for $20 is a bit unbelievable when you consider renting a 500 W amp for $3,000/month. There are cheaper methods of obtaining a high power amp, but from my experience they seem unreliable.
 
Yes, the power isn't evenly distributed and the BW is ~60 MHz, but this can be sharpened for the relatively cheap price of metal to create intermediate resonant cavity and high power coax. And keeping the core temperature steady should prevent frequency drifting, correct?  So IMO, using low power, narrow BW amps is going to make it more difficult to get a 5 sigma deviation from noise unless you have something equivalent to a low-thrust torsion pendulum.

We have recently been dealing with the issue of replicating a magnetron output using the VNA. So today I cut open magnetron to expose the coupling wire used to transfer energy from the resonant cavity to the antenna. It looks like the antenna used consists of the coupling wire pinched in a copper tube, housed in a stainless steel cylindrical cavity.
 
To replicate the antenna, we're thinking of sacrificing another magnetron the cut out the full length of coupling wire, and soldering a BNC-to-wire connection. Then we can approximately simulate a magnetron output and measure reflected power to determine positions of resonance for our adjustable, partially loaded cavity.   

Also, I noticed many people are opting for a laser measurement system. I think this method is ideal, especially if you can track the laser effectively. We were able to borrow a PSM2-10 Position Sensing Module which apparently has 0.0000 mm resolution. However, we don't know how much noise will be present so our actual resolution is TBD.

Kurt
Hey kurt...might humbly suggest an N or mini DIN at these freqs and power levels...had some bad experience at 1kw and bncs...not pretty.

Scope out this chart: http://www.hamradio.me/graphs/connectors/UHFConnectorGraphs/Insertion-Loss_S21_1000.png
« Last Edit: 07/09/2015 01:48 AM by rfmwguy »

Offline deltaMass

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@Todd: This makes no sense to me. Yes, I understand the algebra. Surely Integral[dm/dt, t] should = m(t) at all times. If not, why not? What does this mean physically? What is this dm physically?

Physically? It is the rest mass of the energy being input. Your formula is not a closed system. There is an external energy source, Ein. When you ADD energy you are also adding mass. Okay, my bad.  In Eout, it should be (m(0) + dm(t)/dt), where m(0) is the rest mass of the system at t = 0.

EDIT: Since we didn't use relativistic mass or energy, just rest mass and rest energy, this solution is not relativistic, v can exceed c. However, what it says is that when the integral(dm/dt)dt = m(0), then v = c. I.e., if the rest mass is doubled by dm/dt, making it 200% or 2*m(0), then v = c. That is break even in a Newtonian scenario. Or, if 100% of the starting rest mass is expelled as propellant, then v = c, because there is no rest mass remaining to prevent it. I'm sure if relativistic mass and energy were used, it would also be limited to v < c.

The main point is, I've shown that it will never be over-unity.

EDIT 2: Hmmm.. it is insightful that in a Newtonian approximation, the limiting velocity is c not because of relativistic mass, but because to exceed c would produce an over-unity machine. This gives a whole new perspective to the speed limit, doesn't it?

Todd
I'm experiencing a complete disconnect from what you're doing here. Looking at the input side, which is a battery carried along for the ride - not external, please note - you state
Pin  = dm/dt c2

This says that the battery loses rest mass. That is true, but it is absolutely a tiny mass even over long periods of time, compared with the total rest mass of the device. How is this expected to "save overunity"?

Tell you what - prove it to yourself. Use the numbers I used before (1000 gee, 1 m radius, 100 m/s to my energy breakeven) and recalculate using your dm stuff. I guess you will not see any substantive difference.

My derivation of energy breakeven has been posted here several times. Tossing in some minuscule dm will not make any substantive difference. But you are welcome to go through it line by line and post your version.


« Last Edit: 07/09/2015 02:35 AM by deltaMass »

Offline rfmwguy

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Random thought alert...we've been promised life-changing inventions before like the segway and taco bell home delivery. Yes, they are real; theories have been formulated  agreed upon, yet they are never really life-changing in reality.

What we are struggling with here is a real life-changing proposal...interstellar access and down to earth applications. Before we get too critical or demotivational, consider the what-ifs and temper negativity in lieu of the grand potential. We only have a few of these opportunities in a lifetime.

Just a friendly suggestion.
« Last Edit: 07/09/2015 02:38 AM by rfmwguy »

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