Another thought for you Shell. Haven't you talked about how cold your shop is now? Why not allow the test equipment get as cold as possible in the shop before testing so that the thermal gradient between the room and the heating frustum under load is as large as possible?
Quote from: aero on 10/26/2015 03:41 pmIt is appropriate to be concerned about the force effects of heating ....3) Balance the heat effect with an equal and opposite source, removing residual effects post processing....Of the above, 3) has been proposed but gained no traction. Why is that? A Google search on "common mode error rejection in physical systems" will return more information than can be absorbed, but a lot of good guidance, too. The common mode error compensation technique proposed previously is:Make two, not just one, frustum, near identical. Mount two frustums on opposite sides of the balance beam pivot.Run the system normally and remove residual effects by post processing....a) How expensive is it to make a second, near identical frustum? Several hundred $$ plus time.b) How hard is it to make and mount the second frustum safely on the test stand? Not hard at allc) How difficult will it be to take meaningful data with two 2 EM Drive effect sources? Are you suggesting 2 separate, powered magnetrons? If so, add some more $$ for a power supply, plus a controller to make them fire at the exact same time. Even with that, an imbalance will occur as air masses several feet apart are not identical, meaning there will still be residual thermals with one end versus the other. While its a good idea in theory, practical experience tell me that one could not guaranteed each side would heat and lift identically.My take is ambient air perturbations are best left to only one source, the primary frustum. Delta displacement versus mag on/off times is extractable as has been demonstrated with earlier flight tests. As long as we're not in a vacuum, rotary or fulcrum is what we have to deal with in home lab testing.
It is appropriate to be concerned about the force effects of heating ....3) Balance the heat effect with an equal and opposite source, removing residual effects post processing....Of the above, 3) has been proposed but gained no traction. Why is that? A Google search on "common mode error rejection in physical systems" will return more information than can be absorbed, but a lot of good guidance, too. The common mode error compensation technique proposed previously is:Make two, not just one, frustum, near identical. Mount two frustums on opposite sides of the balance beam pivot.Run the system normally and remove residual effects by post processing....
...Dumb question that may save you some time.Keeping in mind that there are at least three sources of thermal "lift"1. convective air flow, hot air rising on the walls2. buoyancy, hot air inside weighs less than colder air outside3. evacuating air, expanding air evacuates through any openingsWould it not be easier to set up a control run and a test run?In the control run you totally whack your antenna (dielectric?) position internally so that your resonance is as close to zero as practicable, and measure in detail.In the test run, you position your antenna (dielectric?) internally so that your resonance is as high as you can make it, and measure in detail.Then subtract control data from test data and hope that you can carefully replicate everything else between the two runs. Your only variable being (if you're really good), antenna position and resonance.This assumes that the resonance discussions I've been seeing are related to whatever it is to be measured.
A couple of points.Thermal is the 800 pound gorilla sitting in my test lab (hope he gets cold). It's not going to go away even in vacuum where it becomes a 1800 pound gorilla.I've come to the conclusion selecting and controlling the thermal profile where I can negate several aspects of it for short periods by profiling just one. Getting a clean linear thermal inclined line is going to be easier to map out any thrust effects by using a what is essentially a hot air thermal insulated balloon. I'll eliminate the chaotic bubbling off a Maggie thermal chimney like rfmwguy had to work with. Simply by taking all the heat and putting it into one effect not several.This is simply going to take some testing, note a candle outputs about 40 watts of heat.
Quote from: Bob Woods on 10/26/2015 06:01 pmAnother thought for you Shell. Haven't you talked about how cold your shop is now? Why not allow the test equipment get as cold as possible in the shop before testing so that the thermal gradient between the room and the heating frustum under load is as large as possible?Not a great idea for these old bones. Isn't cold air denser?
Sure, profiling is the key to picking the best way to gain data but now I get to pick which way will give me cleaner data with some chicken wire and a piece of insulation. I think it's a good investment,. What do you think?Shell
Perhaps it makes more sense to create a bad vacuum (e.g. one tenth of atmospheric pressure) with a simple and cheap pump in an enclosure with the test article in it? We just want to increase SNR considerably, right? I don't think that a hard vacuum is needed. We just want to get rid of most of the buoyancy for now. My 2 cents .Edit: Actually, it should easily be possible to create a pretty hard vacuum the cheap way:1) 3D-print a metallic enclosure with cooling channels for liquid nitrogen in the walls, perhaps even just the bottom/floor of the enclosure.2) Put an automated, complete test article in it (sorta like a space probe)3) Shut the enclosure and fill it with pure CO2, so that all other gases are pushed out of the enclosure4) Seal the enclosure and start pumping liquid nitrogen through the wall channels. The CO2 freezes out, until there's only solid dry ice left (maybe best only on bottom/floor of enclosure)5) You got vacuum What do you guys think about this method?
Quote from: glennfish on 10/26/2015 05:23 pm...Dumb question that may save you some time.Keeping in mind that there are at least three sources of thermal "lift"1. convective air flow, hot air rising on the walls2. buoyancy, hot air inside weighs less than colder air outside3. evacuating air, expanding air evacuates through any openingsWould it not be easier to set up a control run and a test run?In the control run you totally whack your antenna (dielectric?) position internally so that your resonance is as close to zero as practicable, and measure in detail.In the test run, you position your antenna (dielectric?) internally so that your resonance is as high as you can make it, and measure in detail.Then subtract control data from test data and hope that you can carefully replicate everything else between the two runs. Your only variable being (if you're really good), antenna position and resonance.This assumes that the resonance discussions I've been seeing are related to whatever it is to be measured.I don't believe there is any fool-proof way of nulling out thermal effects. You can drill holes so the hot air escapes horizontally but you still have hot air accumulating in the fustrum and providing lift. In over a year of being a spectator to this em-drive pursuit I have only seen small forces that are almost indistuinguishable from thermal effects. So my position has always been that experimenters should characterize thermal effects at some point in their data collection so that a comparison can be made. So far I haven't seen anyone do this. Maybe it seems too pessimistic to do a null experiment where only heat is applied to the fustrum, but that is what we call Science. If you don't do any counter experiments you will never know if the effect you are observing is from something more mundane.You can follow breadcrumbs but look at where that got Hansel and Gretel.
Quote from: SeeShells on 10/26/2015 07:12 pmA couple of points.Thermal is the 800 pound gorilla sitting in my test lab (hope he gets cold). It's not going to go away even in vacuum where it becomes a 1800 pound gorilla.I've come to the conclusion selecting and controlling the thermal profile where I can negate several aspects of it for short periods by profiling just one. Getting a clean linear thermal inclined line is going to be easier to map out any thrust effects by using a what is essentially a hot air thermal insulated balloon. I'll eliminate the chaotic bubbling off a Maggie thermal chimney like rfmwguy had to work with. Simply by taking all the heat and putting it into one effect not several.This is simply going to take some testing, note a candle outputs about 40 watts of heat.I thought you had planned to use an antenna in your frustum with coax to the magnetron at the pivot point? That alone will remove most of the thermal effects that rfmwguy saw. So do I understand that you intend to bag the frustum and the end of the balance beam with insulation so that heat won't conduct through the sides of the bag? I guess it would then be logical to run a pressure release tube back to the pivot and let the expanding air jet out to the side. That should reduce ballooning leaving only temperature change inside the constant volume balloon to deal with. And of course air currents in your lab which now have the bag to blow around.I guess your bag will be about what, 0.3 m3. Thermal capacity of air, and the ideal gas law are well understood. Does someone want to calculate the bag air temperature and density profile as a function of Watts of drive power delivered to the frustum? That will tell us how long it will be before the bag melts.Then you can watch your lift due to buoyancy to know when your bag will melt.
Quote from: SeeShells on 10/26/2015 06:32 pmSure, profiling is the key to picking the best way to gain data but now I get to pick which way will give me cleaner data with some chicken wire and a piece of insulation. I think it's a good investment,. What do you think?ShellChicken wire is a nice faraday cage on a good day. When my brother was doing his thesis, a faraday cage saved his life. I like chicken wire since that day.The insulation I think only deals with convection. I ran a hot-air balloon simulation a while back (I'll try to find and post the spreadsheet), and I would roughly characterize the effects as1. Hot air balloon - 60%2. Convection - 30%3. Air leaks - 10% (could go either direction)Lots depends on the geometry, that strange epoxy you've fallen for, and how uniform the heating is throughout the frustum, and things I'm horribly unqualified to imagine.I guess my concern is, when you turn it on at normal atmospheric pressure, it will absolutely positively rise like a banshee on Halloween for many reasons having nothing to do with what you're looking for whether pointed up or down. The banshee index (new technical term Bi) will vary depending on how you point the gizmo, and someone who knows how to calculate surface areas of truncated cones could probably calculate that.I am a very lazy person. IMHO, being lazy keeps you from working harder than you should.I can't imagine all the ways heat can mess things up, but I know how to subtract two data sets, especially in the case where you can repeat either a 100 times if you need to. I could imagine a good engineer spending months compensating for all the thermal thingees and still miss one or two or thirty.If, on the other hand, you say "Let There Be HEAT", and you get that clearly characterized, then when you say, "Let There Be HEAT AND Lift", well, IMHO, you could generate a mind blowing data set if there was something after the "AND".Surely there's a few turns of the knob that could totally destroy your ideal resonance? That would be a simple control/test experiment and would answer the question, "Does Resonance Impact the Observed Thrust in an non-vacuum environment?" If there's no difference, you toss me over the bridge for wasting your time. If there is, then you have to replicate both conditions many many times, and then be beaten repeatedly at Reddit for sins against Jackson, Chapter 8.Anyway, my free advice.
I agree. If there is a way to fire up all the heat-generating components, but guarantee that thrust is not generated (short antenna??, detune frustum??), measure the pure thermal effects and then subtract this signal from a (presumably) thrust-producing configuration, it should prove informative.
Quote from: Prunesquallor on 10/26/2015 11:13 pmI agree. If there is a way to fire up all the heat-generating components, but guarantee that thrust is not generated (short antenna??, detune frustum??), measure the pure thermal effects and then subtract this signal from a (presumably) thrust-producing configuration, it should prove informative.Problem is as the freq moves from that of frustum resonance, the VSWR climbs and Rf starts being reflected back to the Rf gen and not absorbed by the frustum. Can't see a way to get the Rf inside the frustum without the Rf freq being at frustum resonance.Still believe the best way to deal with the thermal effects of buoyancy is to mount the frustum horizontal as EW did and I plan to do plus working to increase the Force generated for a fixed amount of heat.From this data it looks like Roger's Experimental EMDrive generated about 200uN of buoyancy for 14mN of Force at 850Ws Rf. You can also see his sealed enclosure and the simple scale setup he used way back in 2002.To me this suggest the approx amounts of buoyancy that may need to be dealt with and more importantly a guide to the Force generation that may be possible with a flat end plate design with no electronic freq tracking but with mechanical tuning at each end plus waveguide impedance matching to get a really good VSWR. Or close to what Shell is building.It might also be helpful to look at the schematic of the setup he build and how he dealt with the heat buildup.Roger passed this info on to us TO USE as I believe he feels it is the most appropriate info at our stage of DIY build. His only reason to do so was to again lay a trail of beard crumbs that if followed will eventually lead to most of us being able to make DIY EMDrives with 10mN level Force generation (lower Q flat end plate 750W maggie units or higher Q spherical end plate 100W solid state Rf amp units) or about where he was from 2002 to around 2009.
pQuote from: aero on 10/26/2015 08:59 pmQuote from: SeeShells on 10/26/2015 07:12 pmA couple of points.Thermal is the 800 pound gorilla sitting in my test lab (hope he gets cold). It's not going to go away even in vacuum where it becomes a 1800 pound gorilla.I've come to the conclusion selecting and controlling the thermal profile where I can negate several aspects of it for short periods by profiling just one. Getting a clean linear thermal inclined line is going to be easier to map out any thrust effects by using a what is essentially a hot air thermal insulated balloon. I'll eliminate the chaotic bubbling off a Maggie thermal chimney like rfmwguy had to work with. Simply by taking all the heat and putting it into one effect not several.This is simply going to take some testing, note a candle outputs about 40 watts of heat.I thought you had planned to use an antenna in your frustum with coax to the magnetron at the pivot point? That alone will remove most of the thermal effects that rfmwguy saw. So do I understand that you intend to bag the frustum and the end of the balance beam with insulation so that heat won't conduct through the sides of the bag? I guess it would then be logical to run a pressure release tube back to the pivot and let the expanding air jet out to the side. That should reduce ballooning leaving only temperature change inside the constant volume balloon to deal with. And of course air currents in your lab which now have the bag to blow around.I guess your bag will be about what, 0.3 m3. Thermal capacity of air, and the ideal gas law are well understood. Does someone want to calculate the bag air temperature and density profile as a function of Watts of drive power delivered to the frustum? That will tell us how long it will be before the bag melts.Then you can watch your lift due to buoyancy to know when your bag will melt. What a day, TV took a big you know what and just got that fixed. Went out to pick up a few things and my truck died (some digital sensor) and is now in the mechanics and because of that the day was shot. Finally got a ride home, thank goodness I like cars (have a few) so I'm not with out wheels.So sorry ppl no new pics from the Crazy Eddie Lab. Tomorrow is another day and I'll start early.Still reading all the fine comments by everyone on the thermal problem and I've decided to profile the dickens out of it with active heat (light bulb ~100 watts) and active without thermal shielding and with shielding. And of course flip the frustum 180.Aero, yes the magnetron is away from the frustum and I'm just running the microwaves down a Coax to the frustum, the only heat will be from the microwaves actions heating the frustum which will be about 100 watts. I'll need to do real world testing to make sure the math works out as to the 100 watts. Interesting idea on the cooling tubes aero, I kind of like it.
" http://forum.nasaspaceflight.com/index.php?topic=38577.msg1439633#msg1439633This whole approach requires some thought but one way or another I really think areo has a breakthrough idea here! "Yep he does, aero is one sharp man. It's called a controlled micro environment. Add a a flex cooling line and a fan... bingo!The cooling hose only connects to the fulcrum beam and the fan isn't attached to the beam but sits on the base of the testing stand. Done correctly this would have little or no impact on the movement of the beam and remove most of the thermal balloon effects. http://masterduct.com.tempdomain.com/SearchProducts/SearchResults/tabid/116/CategoryID/22/List/1/Level/a/ProductID/73/language/en-US/Default.aspxI think it is something that just might work... what do you think? ShellAdded: Sorry this is such a crude drawing and I'm sure there are mods that need to be considered, air insertion points and attachments to the beam and materials. I was simply excited.One more thing... http://www.homedepot.com/p/Tripp-Lite-Portable-Cooling-Unit-or-Air-Conditioner-3-4-kW-120-Volt-60-Hz-12K-BTU-SRCOOL12K/203796126