Of course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.
Quote from: A_M_Swallow on 10/29/2015 05:26 amTo detect rotation just add cameras to the top and side of the cubesat. We can watch the stars move and use that to calculate the speed of rotation. Small accelerometers are also available.Would need a standard cubesat 3 axis mag torquer to obtain stability before firing up the EMDrives. My youngest son was involved in a multi uni project to design a 2U cubesat. He worked on the command and control system which was in 1 cube that supported additional experiments in the other cube. I got a really good idea how to put a cubesat together and how to control it's orientation.
To detect rotation just add cameras to the top and side of the cubesat. We can watch the stars move and use that to calculate the speed of rotation. Small accelerometers are also available.
Quote from: meberbs on 10/25/2015 01:35 pmThe most respected labs that have performed this experiment have yielded almost no thrust.Who are these "Most Respected Labs"? Where is there data, frustum dimensions, excitation modes, VNA resonance freq scans. Force measurement rig designs? I know of no failed EMDrive tests. Such data needs to be analysed as building and testing an EMDrive is not like baking a simple cake recipe. Get one step wrong and there will be no thrust.So PLEASE SHARE the null data. We might just be able to work out where they went wrong and prevent other builders from making the same mistake.
The most respected labs that have performed this experiment have yielded almost no thrust.
Quote from: rfcavity on 10/29/2015 10:07 amOf course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.If the EM wave can't reach the end plate, as the diameter is well below cutoff, how will the EM wave be able of efficiently propogate to bounce off an end plate it can't reach?Or do you ignore Roger's advise to ALWAYS operate the small end ABOVE cutoff?The small end of the cavity is 8.8mm in dia, the big end is 35.2mm in dia and the end plate separation is 75mm. You really believe that cavity will resonate at 4.1GHz despite the small end cutoff being 40GHz and the big end cutoff being 10GHz.Even disallowing that both ends are claimed to be happily operating WELL below cutoff, to achieve resonance some whole number of 1/2 waves at the effective overall guide wavelength need to fit between the end plates.There is no way what can happen.His resonance model is rubbish.
It would appear Egan used c in decameters/sec rather than cm/sec in his frequency calculation.Very quick check so please verify.
Quote from: zellerium on 10/29/2015 04:35 amMy next questions would be: How long would it take to create an obvious rotation with 5 W injected into dual opposing frustums? (and what rotation could be deemed proof of concept?)Can a 5 W Ka band transmitter and two smaller frustums fit on a 6u Cubesat with all other necessary components? Will the transmitter have the frequency range necessary to power the frustum at the temperature extremes?Assuming an unloaded Q of 50,000, Df of 0.9 and spherical end plates, 5Ws should generate around 1.5mNs per frustum. Can't share the Rf gen as each frustum will need independent freq tracking. For 2 frustums this project will need 2 duplicate Rf gens and freq tracking.
My next questions would be: How long would it take to create an obvious rotation with 5 W injected into dual opposing frustums? (and what rotation could be deemed proof of concept?)Can a 5 W Ka band transmitter and two smaller frustums fit on a 6u Cubesat with all other necessary components? Will the transmitter have the frequency range necessary to power the frustum at the temperature extremes?
Months ago, maybe in topic-thread 3, the idea of Cubesat was discussed and someone explained that instabilities/unknown environment on these small orbits are too big - quick calculations returned perturbations nearly on scale of N/Kw. Adding the inability to control directly environment or make any changes once the satelite is launched.
According to your logic, no resonances could exist at all in a cone shaped cavity. That is an incorrect claim, easily testable by experiment. ...
The small size of the cubesats is why I'm creating a frustrum that is made from a series of nesting rings — think collapsible camping cup. However, I wasn't able to find a microwave source that, based on TT's spreadsheet, would give me the resonance I wanted at a scale that fit a "cheap" cubesat, so I'm building with the usual magnetron and at a size similar to most DIY runs. I'm just considering this a x2 scale of the final design.Mostly, I'm just concentrating on not boiling my eyeballs. I'm a writer and geologist. My usual engineering limits involve slicing up plywood to make small boats. I think the last time I soldered something, it was a kit from, Tandy.
Quote from: meberbs on 10/29/2015 12:23 pmAccording 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.
Quote from: Devilstower on 10/29/2015 02:55 pmThe small size of the cubesats is why I'm creating a frustrum that is made from a series of nesting rings — think collapsible camping cup. However, I wasn't able to find a microwave source that, based on TT's spreadsheet, would give me the resonance I wanted at a scale that fit a "cheap" cubesat, so I'm building with the usual magnetron and at a size similar to most DIY runs. I'm just considering this a x2 scale of the final design.Mostly, I'm just concentrating on not boiling my eyeballs. I'm a writer and geologist. My usual engineering limits involve slicing up plywood to make small boats. I think the last time I soldered something, it was a kit from, Tandy.ah heck, granted the fractional megabuck required for the cubesat stuff, plus the free launch, why not leave out the microwave source and just transmit from an earth location. See if you can talk someone in NORAD into doing a radar lock while the cubesat is over the horizon. Better still, see if NORAD will tell you their transmitter frequency in advance so you can design your frustum.
Quote from: TheTraveller on 10/29/2015 10:55 amQuote from: rfcavity on 10/29/2015 10:07 amOf course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.If the EM wave can't reach the end plate, as the diameter is well below cutoff, how will the EM wave be able of efficiently propogate to bounce off an end plate it can't reach?Or do you ignore Roger's advise to ALWAYS operate the small end ABOVE cutoff?The small end of the cavity is 8.8mm in dia, the big end is 35.2mm in dia and the end plate separation is 75mm. You really believe that cavity will resonate at 4.1GHz despite the small end cutoff being 40GHz and the big end cutoff being 10GHz.Even disallowing that both ends are claimed to be happily operating WELL below cutoff, to achieve resonance some whole number of 1/2 waves at the effective overall guide wavelength need to fit between the end plates.There is no way what can happen.His resonance model is rubbish.Waves don't bounce in a cavity. It's a resonance that has math different from physical bouncing. Bouncing is a way to explain to people without math, but the analogy does not hold 100% and is not perfect.By the way, the method you use to calculate cut off uses cut offs derived from cylinder cavities. In textbooks, these cutoff equations are derived exactly the same way as Greg derives for the tapered cavity. So if he is wrong, by rule, you are also wrong.However, checking his work, he is right. I trained in EM. Rodal also says he is right. Please, show what part of his work is wrong, instead of writing paragraphs.
Quote from: rfcavity on 10/29/2015 05:14 pmQuote from: TheTraveller on 10/29/2015 10:55 amQuote from: rfcavity on 10/29/2015 10:07 amOf course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.If the EM wave can't reach the end plate, as the diameter is well below cutoff, how will the EM wave be able of efficiently propogate to bounce off an end plate it can't reach?Or do you ignore Roger's advise to ALWAYS operate the small end ABOVE cutoff?The small end of the cavity is 8.8mm in dia, the big end is 35.2mm in dia and the end plate separation is 75mm. You really believe that cavity will resonate at 4.1GHz despite the small end cutoff being 40GHz and the big end cutoff being 10GHz.Even disallowing that both ends are claimed to be happily operating WELL below cutoff, to achieve resonance some whole number of 1/2 waves at the effective overall guide wavelength need to fit between the end plates.There is no way what can happen.His resonance model is rubbish.Waves don't bounce in a cavity. It's a resonance that has math different from physical bouncing. Bouncing is a way to explain to people without math, but the analogy does not hold 100% and is not perfect.By the way, the method you use to calculate cut off uses cut offs derived from cylinder cavities. In textbooks, these cutoff equations are derived exactly the same way as Greg derives for the tapered cavity. So if he is wrong, by rule, you are also wrong.However, checking his work, he is right. I trained in EM. Rodal also says he is right. Please, show what part of his work is wrong, instead of writing paragraphs.Please, show what part of his work is wrong - He never went beyond theory in his scientific method and gave up after the math exercise.
Quote from: rfmwguy on 10/29/2015 06:18 pmQuote from: rfcavity on 10/29/2015 05:14 pmQuote from: TheTraveller on 10/29/2015 10:55 amQuote from: rfcavity on 10/29/2015 10:07 amOf course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.If the EM wave can't reach the end plate, as the diameter is well below cutoff, how will the EM wave be able of efficiently propogate to bounce off an end plate it can't reach?Or do you ignore Roger's advise to ALWAYS operate the small end ABOVE cutoff?The small end of the cavity is 8.8mm in dia, the big end is 35.2mm in dia and the end plate separation is 75mm. You really believe that cavity will resonate at 4.1GHz despite the small end cutoff being 40GHz and the big end cutoff being 10GHz.Even disallowing that both ends are claimed to be happily operating WELL below cutoff, to achieve resonance some whole number of 1/2 waves at the effective overall guide wavelength need to fit between the end plates.There is no way what can happen.His resonance model is rubbish.Waves don't bounce in a cavity. It's a resonance that has math different from physical bouncing. Bouncing is a way to explain to people without math, but the analogy does not hold 100% and is not perfect.By the way, the method you use to calculate cut off uses cut offs derived from cylinder cavities. In textbooks, these cutoff equations are derived exactly the same way as Greg derives for the tapered cavity. So if he is wrong, by rule, you are also wrong.However, checking his work, he is right. I trained in EM. Rodal also says he is right. Please, show what part of his work is wrong, instead of writing paragraphs.Please, show what part of his work is wrong - He never went beyond theory in his scientific method and gave up after the math exercise.Who, traveller? He,s trying to integrate by parts over different sized cylindrical cavities but that doesn't work as it totally ignores the boundary that exists in the decreasing direction which doesn't exist in a cylinder. That's one problem, but there are probably more. I'm on a phone in Cambridge and I'm catching a flight in the morning to Asia so I can't show the math right now but I can try later.
Quote from: rfmwguy on 10/29/2015 06:18 pmQuote from: rfcavity on 10/29/2015 05:14 pmQuote from: TheTraveller on 10/29/2015 10:55 amQuote from: rfcavity on 10/29/2015 10:07 amOf course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.If the EM wave can't reach the end plate, as the diameter is well below cutoff, how will the EM wave be able of efficiently propogate to bounce off an end plate it can't reach?Or do you ignore Roger's advise to ALWAYS operate the small end ABOVE cutoff?The small end of the cavity is 8.8mm in dia, the big end is 35.2mm in dia and the end plate separation is 75mm. You really believe that cavity will resonate at 4.1GHz despite the small end cutoff being 40GHz and the big end cutoff being 10GHz.Even disallowing that both ends are claimed to be happily operating WELL below cutoff, to achieve resonance some whole number of 1/2 waves at the effective overall guide wavelength need to fit between the end plates.There is no way what can happen.His resonance model is rubbish.Waves don't bounce in a cavity. It's a resonance that has math different from physical bouncing. Bouncing is a way to explain to people without math, but the analogy does not hold 100% and is not perfect.By the way, the method you use to calculate cut off uses cut offs derived from cylinder cavities. In textbooks, these cutoff equations are derived exactly the same way as Greg derives for the tapered cavity. So if he is wrong, by rule, you are also wrong.However, checking his work, he is right. I trained in EM. Rodal also says he is right. Please, show what part of his work is wrong, instead of writing paragraphs.Please, show what part of his work is wrong - He never went beyond theory in his scientific method and gave up after the math exercise.The problem is most time this kind of math/formulas is right(leads to useful results). If the EM-Drive effect is real, the formulas have to be expanded to explain the known standard physics/results as well as the EM-Drive effect. Thats the basic problem we have since thread 1.
Quote from: X_RaY on 10/29/2015 08:15 pmQuote from: rfmwguy on 10/29/2015 06:18 pmQuote from: rfcavity on 10/29/2015 05:14 pmQuote from: TheTraveller on 10/29/2015 10:55 amQuote from: rfcavity on 10/29/2015 10:07 amOf course resonances can exist in a tapered cavity that have lower frequencies than the size of the smallest end. The energy would just exist within the largest part effectively shortening the cavity. Greg even shows this in a plot.This is similar to how partially loaded cavities work, which is a common way to back out permitivitty of materials.If the EM wave can't reach the end plate, as the diameter is well below cutoff, how will the EM wave be able of efficiently propogate to bounce off an end plate it can't reach?Or do you ignore Roger's advise to ALWAYS operate the small end ABOVE cutoff?The small end of the cavity is 8.8mm in dia, the big end is 35.2mm in dia and the end plate separation is 75mm. You really believe that cavity will resonate at 4.1GHz despite the small end cutoff being 40GHz and the big end cutoff being 10GHz.Even disallowing that both ends are claimed to be happily operating WELL below cutoff, to achieve resonance some whole number of 1/2 waves at the effective overall guide wavelength need to fit between the end plates.There is no way what can happen.His resonance model is rubbish.Waves don't bounce in a cavity. It's a resonance that has math different from physical bouncing. Bouncing is a way to explain to people without math, but the analogy does not hold 100% and is not perfect.By the way, the method you use to calculate cut off uses cut offs derived from cylinder cavities. In textbooks, these cutoff equations are derived exactly the same way as Greg derives for the tapered cavity. So if he is wrong, by rule, you are also wrong.However, checking his work, he is right. I trained in EM. Rodal also says he is right. Please, show what part of his work is wrong, instead of writing paragraphs.Please, show what part of his work is wrong - He never went beyond theory in his scientific method and gave up after the math exercise.The problem is most time this kind of math/formulas is right(leads to useful results). If the EM-Drive effect is real, the formulas have to be expanded to explain the known standard physics/results as well as the EM-Drive effect. Thats the basic problem we have since thread 1. Think thats why I temporarily gave up on the theory end of things as nothing I read or already knew made any sense when trying to apply it to emdrive. So to avoid brain tilt, thought I would build one and see. Now thats done and I might get more dramatic results in Phase II (if that happens) I might stick my toe back into the theory world. I'll then try again to look for anything that references kinetic energy and electromagnetic radiation. Seem to recall I drew a big fat zero as no one, including me, would have ever thought to look for it. One avenue I wanted to explore someday is geosyncronous sats. The ones that transmit downlinks at fairly high power. What is their station-keepin needs, etc.