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A Different Kind of EM-Drive - With Real Theory and Precise Calculations by nidalpres on 11 Jul, 2016 04:44
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I came up with this some 20+ years ago and, seeing all the talk around the EmDrive, thought it might be interesting to share.
It is a device that is pretty similar to what is called the EmDrive: it converts electric power into thrust force without using reaction mass (i.e. direct conversion) and it needs quite a bit of electric power to produce minuscule amounts of thrust force.
Differences are:
* the theory behind it is completely clear and based on current science
* there are precise formulae and calculations which can be used to give exact forces produced (or do an estimate using pen and paper)
* it has nothing to do with magnetrons and microwave radiation or any exotic science or "science" or "null fields" or "warp drives" or unicorns
So, to avoid confusion, I'll call this thing I'm presenting an Electro-Magnetic Converter, or EMC for short. I actually called it, long time ago, a "Magnetic Converter of Electric Power into Thrust Force" (my bad, had to be specific), but that is kind of quite a mouthful to say. And EMC sounds cooler, don't you think?
Anyhow, EMC is based on a current and well known science, and essentially on these two premises:
1. magnetic force on electric current is produced as a result of interaction of that current with local magnetic field
2. any change in magnetic field propagates at the speed of light in vacuum (when the change happens in vacuum)
Based on these two premises, after I worked out through all the intermediate versions and setups, it turns out there's a super simple way to convert electric power into thrust force directly. Again, there is no exotic science here (or, again, "science"), this is all based on good old Maxwell theory of electromagnetism coupled with the basic premise of the theory of special relativity. It's all fundamental, well known stuff.
There is just one major practical issue that is visible from outer space, once calculations are done: put in 1kW of electric power into EMC and you get something on the order of microNewton forces as the output.
There is also a second issue, actually a question, that's been bugging me: could this really be true? Did I miss anything?
I had a handful of people (University professors and few engineers) review EMC theory long time ago and they all said theory is sound and the next step would be to build the proof of concept device.
For all of those interested, you can check the story and the theory and diagrams and math behind EMC by going to http://emengine.space, there's just quite a bit of it, so I decided to put it there. Actually, what I've wrote on that website is maybe 1/20th of the material I had at the time. Once the basics have been laid out, there are so many technical and theoretical questions to answer (and ask), that I ended up with pages and pages of scribbling and diagrams as I went through them.
The gist of it is at http://emengine.space
For those of you who have desire, time and drive (yes, pun intended), the challenges are these:
* can you find an error in the theory?
* can you build a simple proof-of-concept which demonstrates that the force exists?
And at the end, everything is released under Creative Commons Attribution-ShareAlike 4.0 International License. I know, another quite a mouthful, eh? But it is for the better of the mankind. Or something like that.
Enjoy.
P.S.
I also posted this on reddit/r/EmDrive. -
#1 by meberbs on 11 Jul, 2016 05:13
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I didn't go though your theory in detail, but everything that is really needed is here:
There is just one major practical issue that is visible from outer space, once calculations are done: put in 1kW of electric power into EMC and you get something on the order of microNewton forces as the output.
If 1 kW of input power produces less than 3.33 microNewtons of thrust, then you have created some form of photon drive. This is in accordance with physics, does not break conservation of momentum (photons carry the momentum away) but as you noted is not actually very useful in most situations. Also, a laser would probably be more efficient than the device you created since directionality of emitted energy is the important factor.
Someone else on this site had proposed a similar device, but didn't do the detailed calculations to realize how energy inefficient it would be. -
#2 by nidalpres on 11 Jul, 2016 16:27
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Thank you for your comment meberbs! Without me going through the details of the photon or laser devices, I really can't comment if those are similar to or same as or totally different from EMC.
Depending on what you have in mind when you say "photon", EMC may or may not have anything to do with it.
Would lasers be more efficient than EMC? I really can't tell without going into details about how those laser devices are supposed to work to produce thrust force and what do we consider when we measure efficiency.
I would just like to point out that drawing far fetched conclusions from one or two sentences taken out of the context can lead to many roads. Some of those roads may have very rewarding results, nevertheless.
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#3 by nidalpres on 11 Jul, 2016 17:22
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As for the numbers here is a quick calculation for a simple case:
There would be an active power loss of 2W @ 50Amp in a pair of copper wire rings of 6cm in diameter fixed at 3cm distance, which would produce cca 1uN of thrust force @ 1MHz. So that is a 1-to-million power/force ratio. However, losses in mosfets (or similar devices) driving those copper rings would be much higher than those 2W, and because of that you would have a much higher power/force ratio which depends on circuitry.
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#4 by meberbs on 12 Jul, 2016 01:24
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Since you said you aren't already familiar with the details of photon thrusters, I'll explain from the basics. Forgive me if you already know some of this.
Photons are massless particles (0 rest mass), but they have both energy and momentum. The momentum transferred by radiated photons on an object is known as radiation pressure, and this pressure is theoretically well understood and has been confirmed by experiments for over 100 years. The energy and momentum are both directly proportional to the frequency. As a result, they have a constant relationship with each other of E = p*c where E is energy, p is momentum, and c is the speed of light. It turns out that special relativity requires that all massless particles have this relationship.
Since photons can carry momentum, they can be used for propulsion by sending a beam of photons out the back of a spaceship. Because it is extremely energy intensive, there are no practical applications with today's technology (in the distant future, storing antimatter as fuel could change this.) You could use a flashlight for something like this, but you waste efficiency for photons that do not travel exactly in the opposite direction of the impulse you desire. As a result, most concepts assume you use a laser beam to have nearly perfectly directed photons. Since force is momentum per time and power is energy per time, the ratio of beam power to thrust is exactly c.
Your concept is equivalent to a photon thuster. Accelerating electric charges results in the emission of EM radiation. You are applying alternating currents to a wire loop, which crates an antenna that will broadcast radiation. Just one loop on its own would radiate symmetrically, so there would be no net force. Putting two antennas near each other driven with the same frequency, but a different phase (time delay) creates a phased array antenna. Modern radars use these to create directional beams of RF radiation by modulating the phase shift of different elements. With just 2 elements, there is likely a significant amount of extra loss that your design has from radiated energy in undesired directions, so it will fall short of the the best efficiency of power per thrust which is c. -
#5 by nidalpres on 12 Jul, 2016 03:08
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That is a nice reply
That is an interesting comparison with a phased array antenna and EMC might quite be one. However, EMC setup is different from phased array in two regards: element positioning and element dimensions compared to wavelength.
To keep it short, you can think of the EMC element as electromagnetically short antenna (length < than half wavelength) and operating in the near-field region.
Thank you meberbs, your comments got me thinking (again) in more detail about how EMC operates and that's what I like about conversations: they get you to think in different ways and find new solutions
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#6 by dustinthewind on 13 Jul, 2016 09:47
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I didn't go though your theory in detail, but everything that is really needed is here:
There is just one major practical issue that is visible from outer space, once calculations are done: put in 1kW of electric power into EMC and you get something on the order of microNewton forces as the output.
If 1 kW of input power produces less than 3.33 microNewtons of thrust, then you have created some form of photon drive. This is in accordance with physics, does not break conservation of momentum (photons carry the momentum away) but as you noted is not actually very useful in most situations. Also, a laser would probably be more efficient than the device you created since directionality of emitted energy is the important factor.
Someone else on this site had proposed a similar device, but didn't do the detailed calculations to realize how energy inefficient it would be.
I am fairly sure he is talking about me. I thought I had an original idea and started trying to patent it when I found this patent "patent 8,459,002.pdf" online at uspto.gov . The link to my thread is here: https://forum.nasaspaceflight.com/index.php?topic=36911.0 . I am not convinced that it is impossible for variations on this to provide more thrust than a photon rocket and would like to test it some day.
After finding that patent and discussing it here on the forum my idea has evolved quite a bit. At first I was just thinking like you are about how the magnetic field takes time to travel in space. I was able to figure out that the currents are 90degrees out of phase and their spacing so I made a diagram. See below, "Normal phased array.png" I never went as far in the math as you and worked mostly using diagrams.
Through the diagram I discovered that the propulsion from the magnetic field is in opposition to the electric field. When charge separation happens in the wires with osculating currents there is an electric field from charge capacitance which propels the current loops in the opposite direction as the magnetic forces. This is fascinating that the magnetic field is in opposition of the static electric field in a phased array. I was able to make an arrangement in which the phased array allows the magnetic field to work with the static electric field. I called it the reverse magnetic phased array, see: "reversed mag phased array.png". I thought this was fairly original but now looking back on it I realize this Friend of WarpTech by the name of David here: https://forum.nasaspaceflight.com/index.php?topic=36911.msg1455270#msg1455270 probably beat me to the punch. All I did was design a circuit that seems capable of what is in his video here: https://forum.nasaspaceflight.com/index.php?topic=36911.msg1454767#msg1454767 I think I realized later after designing the circuit that this is what was in his video. I remember watching it multiple times. The fellow here that goes by the name WarpTech also suggested he was considering this in his early years. I think he gave up on it but is still searching for other ways. You will see his comments in my thread and some in the EM drive thread.
I think this static electric field dies off at low frequencies but I need to confirm this some time. I think it may be beneficial to operate at frequencies lower than microwaves. Possibly RF.
The last key I think is in this patent I found I provide in the link above, "patent 8,459,002.pdf". They suggest using a dielectric between the wires/coils. Actually this is mentioned in some research papers in my thread I just found out here: https://forum.nasaspaceflight.com/index.php?topic=36911.msg1350570#msg1350570. I think it was suggested barrium titanate or maybe "titanate barium strontium" which is "supposed" to have a high index for RF meaning it slows down RF to a crawl. This allows us to get the coils of wire much closer together. The coils are still a quarter wavelength apart and 90 degrees out of phase but because the speed of light for that wavelength in the dielectric is massively slowed down this shortens the length of a wavelength in the material. As a result of the wires being much closer together the field strengths are larger.
I was also considering putting a disk of iron inside the flat coil to further amplify the magnetic field but this iron would change the rate at which the coils can osculate.
Supposedly the light created is supposed to drag on the dielectric and reduce the thrust but it would be up the the calculations/experiment to see if it cancels out the benefit from the wires being closer together.
I am glad to meet some one else that found this concept interesting.
Edit: inserted the word "concept", also my teacher is the one that suggested I might use iron in the phased array concept a long time ago. It took me a while to figure out how I might insert it so the signal still has time delay.
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#7 by nidalpres on 14 Jul, 2016 02:18
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Thank you Dustin, I'm impressed, that is pretty much it!
The patent you are referring to (http://www.google.com/patents/US8459002) basically describes the EMC. I have documents that show that what I call EMC theory (and what is described on http://emengine.space and released under Creative Commons license) existed in 1995, but I never thought of patenting it, I always thought it would be much better to have it released under some other conditions for everyone to use it and to contribute freely.
Anyhow, that's, in essence, the same thing. However, there are some points that apparently are not quite obvious at the first glance, and which would not work (I won't go into details):
- use of dielectric to "amplify" force wouldn't work
- use of iron or ferro-electric or any other magnetic core to amplify force wouldn't work, especially iron at RF frequencies
- having loops at quarter or half wavelength is very inefficient, loops need to be at very specific, unique distance apart which depends on frequency and loop geometry and at that distance the thrust force will have it's maximum value
- having more than 2 loops stacked one after another (like in the patent) wouldn't make any difference that would be worth the effort. loops should be paired and then a lot of pairs set in the same plane (like thin disc or phased array radar elements) and then couple of those planes could be stacked one on top of the other but at the distance that is greater than 4-5 loop diameters (or something like that, can't remember the exact number)
- the best results are obtained with the loops of the same size
etc.
I've spent quite some time going through the details and used math and various data and measurements (dielectrics, ferrous cores, heat dissipation in aluminium, copper etc.) to support my thinking, but I did all that because I had, relatively, a lot of free time available then and I needed something to distract me from time to time, and not because I thought it would amount to a useful propulsion device for everyday use.
It may propel deep space probes sometime in the future but I don't see me doing any work for NASA or any space agency any time soon, or having enough time and resources to start my own space agency or another SpaceX, so I just dropped it and went on to do something more interesting to me.
In any case, it seems that there are enough interested people to maybe make something out of this and I hope you can use the explanation and math I presented on http://emengine.space. It's free and there are no patents on it.
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#8 by dustinthewind on 15 Jul, 2016 01:34
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...
In any case, it seems that there are enough interested people to maybe make something out of this and I hope you can use the explanation and math I presented on http://emengine.space. It's free and there are no patents on it.
Yeah, I always wanted to be in the research and development field. I thought the patent, inventor route might be it but after a while of trying to patent on my own and getting rejected (an idea for the wife) and the costs of patent lawyers and the loops to jump through I have seemingly given up on it. Maybe temporarily. After I found some one beat me to the idea, all I really wanted to do was point it out to those interested. As long as it didn't get swept under the carpet so to speak. I know how badly we need some new form of propulsion. I don't really have a garage or the money to test what I want at the moment, so I was hoping the same as you.
That is an interesting comparison with a phased array antenna and EMC might quite be one. However, EMC setup is different from phased array in two regards: element positioning and element dimensions compared to wavelength.