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#3200 by Gilbertdrive on 16 Jun, 2016 15:37
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In general, I enjoy reading your posts. You are knowledgeable and well informed. However, this one disappoints me. You are entirely correct on almost everything you said, where you went wrong is saying that a solar sail meant to reflect gamma rays or stop them would not be more efficient due to the need for heavy shielding. While this remains true today, we may one day discover exotic new properties or amplifications of known effects regarding the known realm of existing materials, or maybe a new one entirely.
I understand your critic. I did not think that the question implied hypothesis on exotic matter.
But, even with exotic matter, there is no big possible progress.
During the biggest solar flare since the space age, the X28 of 2003, the X plus gamma power was 2,8 mW/m². I will overestimate the amount of gamma by considering that all the 2,8 mW/m² is composed of gamma rays.
So, 1367/(2,8*10^(-3)) gives us a ratio of 488 214. Even during this extreme event, non gamma photons energy represents more than 488 000 times gamma ray energy. Even if the aim was to use it during solar flares, it has still no interest.
Supposing a catastrophic flare year, with the worst intensity of solar flares during a tenth of the year, it would give an average bonus of 1 / 4 880 000.
In a year of solar sailing, it would make a bonus of 365*24*24*3600/4880000=155 seconds.
The equivalent of less than a 3 minutes acceleration gain in the best possible gamma year. It has no interest.
If we have one day an exotic matter that stops the gamma with the thikness of a solar sail, it would be a big revolution. It would allow combinaisons for workers in the nuclear industry, it would allow to shield martian habitations, to shield spaceships, spacestations, it would allow to use standard electronic components in space probes, spaceships, etc. It would be marvellous, but for the solar sails, we would see no difference.
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#3201 by FattyLumpkin on 16 Jun, 2016 16:13
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Gilbertdrive, I'm going from memory on this one, but I think your info. re the astronauts and their exposure to radiation on might be off. If memory serves there is a "shelter" onboard the ISS in case of solar flares, and that most of the radiation occupants of the SS are exposed to comes from cosmic rays. I don't believe anyone individual (space going) has a cumulative life dose of > 2 Sieverts. NASA says a round trip conjunction class journey to Mars including the long stay on the surface would not exceed 1.1 Sieverts (and NASA says that's not acceptable), even though spread out over time. A spacecraft travelling to Mars would also require a shelter from flares of the sun, but there's no stopping GCR, and GCR accounts for most of the exposure on the ISS. Even commercial jet pilots have an increased exposure (life dose) to GCR for the routine high altitudes that they fly at, and it is the reduction in atmosphere which allows for more exposure.
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#3202 by Gilbertdrive on 16 Jun, 2016 16:36
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Gilbertdrive, I'm going from memory on this one, but I think your info. re the astronauts and their exposure to radiation on might be off. If memory serves there is a "shelter" onboard the ISS in case of solar flares, and that most of the radiation occupants of the SS are exposed to comes from cosmic rays. I don't believe anyone individual (space going) has a cumulative life dose of > 2 Sieverts. NASA says a round trip conjunction class journey to Mars including the long stay on the surface would not exceed 1.1 Sieverts (and NASA says that's not acceptable), even though spread out over time. A spacecraft travelling to Mars would also require a shelter from flares of the sun, but there's no stopping GCR.
I have taken this max here :
https://en.wikipedia.org/wiki/Spaceflight_radiation_carcinogenesis
2 mSv in six month, so 4 mSv for a year.
I totally agree with you on the fact that it is far less. But my aim was to overestimate that number, to show that, even like that, the exotic solar sail had no gain. I did not try to make the most accurate estimation, but I wanted to be sure to overestimate it.
You are also right for the shelter onboard the ISS. But I thought it was stopping less than 90% of gamma rays. My estimation of gamma power is very bad, but what is important is that it needs to be an overestimation.
If you think that I may have underestimate the gamma radiation, I am ready to reconsider
And of course it should be far better to get somewhere an average gamma power of the sun. -
#3203 by FattyLumpkin on 16 Jun, 2016 16:59
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OK, now I'm going to have to research it again. Thank you! Never can be too sure here. + think we're headed off topic, so will comm. with you by PM Ciao! K
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#3204 by Gilbertdrive on 16 Jun, 2016 19:31
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OK, now I'm going to have to research it again. Thank you! Never can be too sure here. + think we're headed off topic, so will comm. with you by PM Ciao! K
You are right, but I have a last thing to correct. A mistake that i did.
I have forgotten in my formula the mass of the astronauts. The sievert are an unit per kg. In fact my calculus would work if the astronauts were weighting only one kg. And if I multiply the result by 75, I found more than during an usual solar flare. So it means that my overestimation was too overestimate, it is useless. I apologize.
We can just keep for the demonstration the ratio during the worst solar flare. 1/488 000. that includes also X rays. (so in fact gamma rays are less than that. Probably far less)
Our exotic solar sail can not do more than 0.002% better than classic solar sail, and only a few time each year.
I have edited my preceding post, to remove my approximations. Now it is shorter. -
#3205 by rfmwguy on 16 Jun, 2016 19:52
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Sorry you didn't get a reply from other users here. My emdrive design, build and current test data is: rfdriven.com/forum/ (registration required). Running commentary at reddit.com/r/qthruster/ and sometimes Twitter @rfmwguy Significant observations taking place in the past few days. Site here seems to be more focused/comfortable with Theory. Here is a teaser:This past June 2, 2016, Rfmwguy removed his previously claimed results for the EM Drive wiki:
Can someone explain (or give a link) what happened with Rfmwguy and his experiments?!
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#3206 by dustinthewind on 16 Jun, 2016 20:14
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Please forgive me if something like this has been posted before...
I've always liked the idea that the momentum of the EM waves in the EM drive is somehow being directly converted into momentum of the frustum. Awhile back, I came across this use of acoustic waves to levitate and rotate small objects by manipulating standing waves.
http://www.wired.co.uk/article/sonic-tractor-beam-moves-beads-with-sound
Correct me if I'm wrong, but I would conclude that some portion of the the momentum of the sound wave is transferred to the object being manipulated. Enough to counter the pull of gravity. And isn't a sound wave uncoupled from a speaker the moment it leaves? So, the object is truly levitating, right? It's not exerting any force on the speaker array, right?
So, could the same principal be reversed (modified?) to create carefully controlled standing acoustic waves inside a specially shaped enclosed cavity? I guess it would be an Acoustic Wave Drive (AW Drive) instead of an EM Drive... If standing acoustic waves are able to transfer some of their momentum into the cavity to produce thrust, could this be an analogue of what might be happening in an EM Drive?
We've talked a lot on this forum about TE modes and TM modes and Dielectric inserts, but I don't know that we've ever talked about EM holograms
I would say that the ball is exerting a force downward on the speaker array. That is there is compression of air between the ball and speaker array due to gravitational force on the ball which transfers to the speakers. This greatly reminds me of the recycled photon thrusters.
There is the question if the mass of light changes when it slows down. I think it is believed light does slow down when it enters a narrow region such that it cannot propagate effectively in that region if I remember correctly. I was noticing in some simulations of the cavity that the wavelength was increasing at the narrow end. One paper I read reciently suggested for instance a possible method for light to change mass....
I have attached below from momentum conservation and energy conservation a derivation of how the change in velocity of two systems that collide both experience a change in velocity that is the same. After identifying they are the same I again substitute this into the energy conservation statement of two objects colliding and divide both sides by the total energy to get a % of energy distribution between the two colliding objects. This ratio of energy distribution only seems to depend on relative mass of the two colliding objects. So if light is heavier it can more effectively give up its energy.
In a closed cavity light normally would give up some of its energy to the cavity, but upon hitting the other wall it would re-gain its energy it lost (assuming a perfect reflection no energy lost to heat). However if the mass of light changes at one end of the cavity this is no longer true and instead the cavity begins to draw energy from the light with each two reflections, times the number of photons in the cavity. If light can have mass then the mass of light is so small that a small change in its mass (say double its mass) could have large implications.
What should limit this idea from gaining infinite energy is that if the cavity reaches a % of the speed of light, then the light striking the narrow end would be Doppler shifted by relativity, causing the light to appear to lose mass. At some point the cavity can no longer accelerate when the mass of the light striking the back = the mass of the light striking the front. This is important to those questioning energy conservation.
I had to fix the "energy distributed by bounce.png" as there was a small error in it (software glitch between different versions of wxMaxima). Fixed now.
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#3207 by teitur on 16 Jun, 2016 20:25
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Sorry you didn't get a reply from other users here. My emdrive design, build and current test data is: rfdriven.com/forum/ (registration required). Running commentary at reddit.com/r/qthruster/ and sometimes Twitter @rfmwguy Significant observations taking place in the past few days. Site here seems to be more focused/comfortable with Theory. Here is a teaser:
Straight from the horse's mouth. Good to see you back and I must say a most intrigueing plot !
Keep up the good work.
Teitur
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#3208 by RotoSequence on 16 Jun, 2016 20:36
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Site here seems to be more focused/comfortable with Theory.
The theory is welcome, especially since there are several participants who have degrees in the relevant physics and/or are skilled in the relevant mathematics, but experimental data is the meat that I've been coming to this thread for and waiting for more of, for heaven's sake! Please, folks, don't segregate experimental data and theory by social media platform...
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#3209 by Slyver on 16 Jun, 2016 21:51
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Site here seems to be more focused/comfortable with Theory.
The theory is welcome, especially since there are several participants who have degrees in the relevant physics and/or are skilled in the relevant mathematics, but experimental data is the meat that I've been coming to this thread for and waiting for more of, for heaven's sake! Please, folks, don't segregate experimental data and theory by social media platform...
I was going to just "like" this, but it's import deserves a follow up.
I am not sure why people may be posting experimental data elsewhere and not here, and frankly, I don't care. It is a crime (or should be) to not present any experimental data you have in this thread for the following reasons:
1) This is the most comprehensive place for all things EMDrive.
2) Posters here are generally more knowledgeable, open minded and level-tempered than any other resource on the topic.
3) Many people (like myself) come ONLY to this thread for information, because it has the highest signal to noise ratio, and we can only devote so much of our busy lives to this exciting topic.
4) It is not a perfect place. Occasionally people have emotional responses, or belabor issues; not all posts are equally contributing to the topic, some (few) are truly off-topic, some people may get under your skin at times, BUT none of that negates the veracity of points 1-3.
Please post ALL experimental data here.
Thank you from the bottom of my heart for all of your efforts,
Slyver -
#3210 by mwvp on 17 Jun, 2016 01:24
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Hi all, me again with my two cents...
...My emdrive design, build and current test data is:ore focused/comfortable with Theory. Here is a teaser:
Welcome back! I (we?) missed you, and your results
And now, for the spare change...
Regarding acoustic levitation, see http://www.ece.uvic.ca/~bctill/papers/numacoust/Beyer_1978.pdf
Google may befriend, even if Wikipedia disappoints. Try "acoustic radiation pressure, Raleigh radiation pressure. The "vacuum", although possessing the properties of permittivity and permiability, lacks viscosity, mass, and in a mechanical sense, heat capacity. Moreover, the efficacy of reasoning degrades as one attempts inferences about antecedent phenomena from their remotely related consequences. Vacuum dynamics lead to particles and light, particles and light to vibrations and mechanical dynamics. Making inferences about electrodynamics from mechanics is a stretch, but sometimes all we got and our experience derived intuitions.
Unless we've been mathematically-afflicted. Which I, alas, haven't much. And so...
Regarding photon rockets,
Gear ratios, and the maximum power transfer theorem come to mind. One can use gears, levers and resonant circuits/cavities to increase transfer efficiency, as that Wikipedia article on photon rockets discusses about the utility of BAE's photon recycling.
I can spell it out with examples. But I'd rather leave it to my more formal, and less impaired betters. Momentum may divide linearly, but energy depends on velocity or voltage squared. When you jump up from the ground or fire a gun, momentum divides evenly but the energy doesn't between yourself and the earth, or yourself+gun and the bullet. Or between a battery and a load, matched not for "maximum power transfer" (based on source impedance; see the Wikipedia article on the "maximum power transfer theorem"), but for maximum efficiency.
The frustrum may be a matching network, a gearbox, as it were, for photon recycling and boosting transfer efficiency, as BAE's cavity is. That is, if you consider the EM Drive as a thermodynamically open system.
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#3211 by Rodal on 17 Jun, 2016 01:36
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....I can spell it out with examples. But I'd rather leave it to my more formal, and less impaired betters. Momentum may divide linearly, but energy depends on velocity or voltage squared. ...
Sorry, but the situation is worse than that for momentum for spacecraft propulsion . To enable spacecraft propulsion, momentum is a nonlinear function, because of variable mass in kinetic momentum.
Also, the electromagnetic momentum in vacuum:
does not "divide evenly" either, in the sense that it is also a nonlinear function:
and
With the E and B out of phase sinusoidal functions of time with frequency f, the electromagnetic momentum is a square harmonic function of time: the momentum will have frequency 2 f.
Also, kinetic momentum only "divides evenly" in the sense of being a linear function of velocity only for small velocities, for constant mass. Even considering Special Relativity, the momentum is a very nonlinear function of velocity, due to the change in mass (*):
One must use Lorentz transformations.
So, there are multiple ways that one can divide the momentum and stresses in general for electromagnetic problems and this has created a lot of confusion as people in EM Drive papers have incorrectly defined the forces and have arrived at conclusions that violate conservation of momentum and conservation of energy that are intrinsically satisfied by Maxwell's equations and Special Relativity (see: http://forum.nasaspaceflight.com/index.php?topic=39214.msg1546438#msg1546438). However one divides them, the important thing is to get the correct force and satisfy conservation of momentum and conservation of energy.
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(*) In general one has to consider variable mass for space propulsion even at low velocities, as all known working rockets (chemical, nuclear, ion and photon rockets) eject propellant resulting in variable mass of the spacecraft, for a conventional rocket expelling propellant, the Tsiolkovsky equation:
Also non-conventional propellant-less drives like Woodward's relies on variable mass as well for propulsion:. Even for the EM Drive, McCulloch introduces the very unconventional notion of variable inertial mass of photons in his explanation, to justify propulsion:
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#3212 by Bob Woods on 17 Jun, 2016 02:35
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Re: Reports of my demise have been greatly exaggerated...
Actually, we were concerned of reports of your surmise...
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#3213 by timbatman1960 on 17 Jun, 2016 03:28
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Just found this paper entitled "On the Exhaust of Electromagnetic Drive" submitted by Grahn, Annila, and Kolehmainen in the journal AIP Advance:
http://dx.doi.org/10.1063/1.4953807
The authors postulate a potential theoretical underpinning for the EM drive effect which appears to be at least a partial departure from current theories and which also addresses problems wrt momentum conservation. I'm not qualified to comment on its veracity, but several here are. I'm curious to see what those well versed the relevant subject matter have to say...
Sent from my iPad using Tapatalk -
#3214 by R.W. Keyes on 17 Jun, 2016 04:23
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I don't know how well equipped you all are for RF signal generation. I've ordered a LimeSDR (Software Defined Radio), it's crowdsource-funded. It's got really great specs compared to the other units out there, and is pretty cheap at $249. The drawback is it won't ship until November, and if it doesn't get enough orders in the for days before the fundraising drive is over, it won't happen at all. If you find that a magnetron just doesn't have the precision you need, this might be a good solution. It's also a versatile device to have around the house/shack/lab. I don't have any connection with this project other than having ordered one and want to the funding succeed.
https://www.crowdsupply.com/lime-micro/limesdr
RF Transceiver: Lime Microsystems LMS7002M MIMO FPRF
FPGA: Altera Cyclone IV EP4CE40F23 - also compatible with EP4CE30F23
Memory: 256 MBytes DDR2 SDRAM
USB 3.0 controller: Cypress USB 3.0 CYUSB3014-BZXC
Oscillator: Rakon RPT7050A @30.72MHz (Datasheet)
Continuous frequency range: 100 kHz – 3.8 GHz
Bandwidth: 61.44 MHz
RF connection: 10 U.FL connectors (6 RX, 4 TX)
Power Output (CW): up to 10 dBm
Multiplexing: 2x2 MIMO
Power: micro USB connector or optional external power supply
Status indicators: programmable LEDs
Dimensions: 100 mm x 60 mm -
#3215 by Gilbertdrive on 17 Jun, 2016 08:45
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There is a peer reviewed paper about the EmdriveQuote from: Mary-Ann Russon on ibtimes.co.uk
http://www.ibtimes.co.uk/emdrive-finnish-physicist-says-controversial-space-propulsion-device-does-have-exhaust-1565673
A new peer-reviewed paper on the EmDrive from Finland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting into photons that leak out of the closed cavity, producing an exhaust.
The research, entitled "On the exhaust of electromagnetic drive", is published in the journal AIP Advances 6 and is the brainchild of Dr Arto Annila, a physics professor at the University of Helsinki; Dr Erkki Kolehmainen, an organic chemistry professor at the University of Jyväskylä; and Patrick Grahn, a multiphysicist at engineering software firm Comsol.
But I do not understand how it would explain that it makes more thrust than of a perfectly collimated photon rocket. -
#3216 by Rodal on 17 Jun, 2016 15:21
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Just found this paper entitled "On the Exhaust of Electromagnetic Drive" submitted by Grahn, Annila, and Kolehmainen in the journal AIP Advance:
http://dx.doi.org/10.1063/1.4953807
The authors postulate a potential theoretical underpinning for the EM drive effect which appears to be at least a partial departure from current theories and which also addresses problems wrt momentum conservation. I'm not qualified to comment on its veracity, but several here are. I'm curious to see what those well versed the relevant subject matter have to say...
Sent from my iPad using TapatalkThere is a peer reviewed paper about the Emdrive
1) Substandard peer-review: it is not unusual for peer-review editors to not have enough time and expertise in the particular subject of articles to dig in and challenge articles being published nowadays in these journals ("publish or perish").Quote from: Mary-Ann Russon on ibtimes.co.uk
http://www.ibtimes.co.uk/emdrive-finnish-physicist-says-controversial-space-propulsion-device-does-have-exhaust-1565673
A new peer-reviewed paper on the EmDrive from Finland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting into photons that leak out of the closed cavity, producing an exhaust.
The research, entitled "On the exhaust of electromagnetic drive", is published in the journal AIP Advances 6 and is the brainchild of Dr Arto Annila, a physics professor at the University of Helsinki; Dr Erkki Kolehmainen, an organic chemistry professor at the University of Jyväskylä; and Patrick Grahn, a multiphysicist at engineering software firm Comsol.
But I do not understand how it would explain that it makes more thrust than of a perfectly collimated photon rocket.
2) It would require an electron-positron virtual pair production, and then you have Dr. White's model.
Dr. White, given his background in Space vehicles at Johnson Space Center, recognized the issue that pair photon production would not address the claims of anomalous force/PowerInput exceeding by orders of magnitude the one of a perfectly collimated photon rocket. However, as Dr. White admits, this involves a degradable and mutable vacuum, in conflict with the zero-point model of the Quantum Vacuum commonly accepted since Einstein proposed the concept of zero point energy. Zero-point energy is, by definition, a minimum energy below which a thermodynamic system can never go. According to the standard view of the vacuum as immutable and not degradable, none of this energy-momentum can be withdrawn without altering the system to a different form in which the system has a lower zero-point energy. So according to this standard view, one should not be able to get momentum or energy from the zero-point energy vacuum.
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#3217 by zen-in on 17 Jun, 2016 15:48
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Sorry you didn't get a reply from other users here. My emdrive design, build and current test data is: rfdriven.com/forum/ (registration required). Running commentary at reddit.com/r/qthruster/ and sometimes Twitter @rfmwguy Significant observations taking place in the past few days. Site here seems to be more focused/comfortable with Theory. Here is a teaser:This past June 2, 2016, Rfmwguy removed his previously claimed results for the EM Drive wiki:
Can someone explain (or give a link) what happened with Rfmwguy and his experiments?!
More data is needed to interpret your results accurately. Looking at this one graph, the best I can make of it is that it does appear to be a thermal effect. If an em-drive force was being produced the waveform would have an upward slope at each time after the RF has been switch off. Instead the average slope appears to be zero. This indicates the (long duration) thermal time constant predominates. However I may be wrong. More data is needed and more information on the test protocol is needed. You should write a paper.
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#3218 by X_RaY on 17 Jun, 2016 17:59
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Regarding Dr. White's theory, for me a question remains since thread 3: How may it possible that charged particles (e+;e-) escape from a metallic cavity?
Has anyone suggestions for a closed explanation about it?QuoteIs there someone who explain me the following?
https://forum.nasaspaceflight.com/index.php?topic=37642.msg1404617#msg1404617
I don't understand in Dr White's theory of virtual electrons and positrons:
This particles are real after creation (for a really short time, not an infinite) and are able to interact with the copper at the large diameter. If a created positron for example interacts with a electron inside the copper it'll annihilate and erased, at the same time a photon will radiate from the annihilation point(with a other wavelength, feynman diagramm)... how can it be that there are "real-virtual" particle from inside deliver to outside the cavity. I think i've got read about the energy to create those particles is spent by the quantum vacuum energy for a short while to get real particles, real particles can interact with other real particles and the copper is a great barrier for the positrons and electrons. Don't know how this particle can escape. Please help me to understand. Got i am wrong or not?
If i am wrong Hawking radiation may also. -
#3219 by Rodal on 17 Jun, 2016 18:26
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Regarding Dr. White's theory, for me a question remains since thread 3: How may it possible that charged particles (e+;e-) escape from a metallic cavity?
Yes, good question, if one is prepared to accept the notion of a degradable vacuum...
Has anyone suggestions for a closed explanation about it?QuoteIs there someone who explain me the following?
https://forum.nasaspaceflight.com/index.php?topic=37642.msg1404617#msg1404617
I don't understand in Dr White's theory of virtual electrons and positrons:
This particles are real after creation (for a really short time, not an infinite) and are able to interact with the copper at the large diameter. If a created positron for example interacts with a electron inside the copper it'll annihilate and erased, at the same time a photon will radiate from the annihilation point(with a other wavelength, feynman diagramm)... how can it be that there are "real-virtual" particle from inside deliver to outside the cavity. I think i've got read about the energy to create those particles is spent by the quantum vacuum energy for a short while to get real particles, real particles can interact with other real particles and the copper is a great barrier for the positrons and electrons. Don't know how this particle can escape. Please help me to understand. Got i am wrong or not? If i am wrong Hawking radiation may also.
Perhaps he is saying that the interaction between the electromagnetic fields and the degradable vacuum virtual pairs occurs inside the EM Drive cavity, and that these virtual particles are ephimeral, extremely short-lived, so that they disappear back into the vacuum before the metallic wall has any chance to interact with them after that happened. Essentially saying that the "propulsion" occurs inside the EM Drive.
If i am wrong Hawking radiation may also.