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#1320 by Moe Grills on 05 Jan, 2016 18:25
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You guys and gals who are experimenting with this are speaking gibberish. And I received an A+ in college physics.
Speak to us in common English please and let us know what PRACTICAL applications are possible if you scale up the power-levels, time durations with much improved, more expensive hardware. -
#1321 by RotoSequence on 05 Jan, 2016 18:32
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You guys and gals who are experimenting with this are speaking gibberish. And I received an A+ in college physics.
Speak to us in common English please and let us know what PRACTICAL applications are possible if you scale up the power-levels, time durations with much improved, more expensive hardware.
Career RF engineers with decades of practical experience and persons with PhDs in the relevant physics would be doing everyone a disservice by altering the language for people without a background in electromagnetics. It's best to let the experts speak as experts, because there's a lot of very cool stuff to learn about from the backgrounds of these guys and gals.
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#1322 by OnlyMe on 05 Jan, 2016 18:34
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You guys and gals who are experimenting with this are speaking gibberish. And I received an A+ in college physics.
Speak to us in common English please and let us know what PRACTICAL applications are possible if you scale up the power-levels, time durations with much improved, more expensive hardware.
Just mN (fractions of an ounce) thrusts would make satellite station keeping and even repositioning practical and extend a satellite's useful life time considerably.
Make probes to Mars and outer planets run on time frames of months instead of years to decades....
Even make low earth orbit to the moon and back a practical round trip for astronauts and moon bases.
Given a power source an EMDrive array could put a great deal more of the solar system within reach, possibly before other long term deep space issues are solved. -
#1323 by OnlyMe on 05 Jan, 2016 18:41
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You guys and gals who are experimenting with this are speaking gibberish. And I received an A+ in college physics.
Speak to us in common English please and let us know what PRACTICAL applications are possible if you scale up the power-levels, time durations with much improved, more expensive hardware.
Career RF engineers with decades of practical experience and persons with PhDs in the relevant physics would be doing everyone a disservice by altering the language for people without a background in electromagnetics. It's best to let the experts speak as experts, because there's a lot of very cool stuff to learn about from the backgrounds of these guys and gals.
The kind of funding that will be needed to put anything discovered here into practical use, will require public support.., even if it is done through institutions like NASA. So a little plain talk, or plain language explanation wouldn't hurt.
Once thrust is convincingly demonstrated, a large part of the discussion will probably be moved to L2 status and a significant reduction in the lay audience. The experts will then be talking to experts, without a peanut gallery on the sidelines. -
#1324 by aero on 05 Jan, 2016 18:48
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Lots of details involved in analysing the sling, it would make a suitable senior project IMO. Need:
coefficient of thermal expansion of sling material
temperature of the heat radiating source
temperature of the sling material (cooling by radiation)
absorption coefficient?
length and diameter of sling leads
relative location of heat radiating source
And likely more
Its a project for a young person with energy and motivation (or someone paid to be motivated). Either way, that rules me out. -
#1325 by Moe Grills on 05 Jan, 2016 18:54
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You guys and gals who are experimenting with this are speaking gibberish. And I received an A+ in college physics.
Speak to us in common English please and let us know what PRACTICAL applications are possible if you scale up the power-levels, time durations with much improved, more expensive hardware.
Career RF engineers with decades of practical experience and persons with PhDs in the relevant physics would be doing everyone a disservice by altering the language for people without a background in electromagnetics. It's best to let the experts speak as experts, because there's a lot of very cool stuff to learn about from the backgrounds of these guys and gals.
(Mod removed post) -
#1326 by Rodal on 05 Jan, 2016 18:57
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Lots of details involved in analysing the sling, it would make a suitable senior project IMO. Need:
Just for comparison, we have the example of how much effort (and controversy to this date by people claiming that the effect was due to anomalous reasons) went into modeling the Pioneer anomaly, and that was simpler (in a narrow sense), than the thermal issues discussed here, as that analysis of thermal effects by a whole NASA JPL team did not involve thermal convection (as it took place in a relative vacuum). Accounting for all the (usually small but not when compared to tiny forces) thermal effects of a structure, etc. , etc. is not trivial when such thermal effects are small, of the same order as other small forces.
coefficient of thermal expansion of sling material
temperature of the heat radiating source
temperature of the sling material (cooling by radiation)
absorption coefficient?
length and diameter of sling leads
relative location of heat radiating source
And likely more
Its a project for a young person with energy and motivation (or someone paid to be motivated). Either way, that rules me out. -
#1327 by RotoSequence on 05 Jan, 2016 19:07
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(mod removed post)
The focus of the discussions in these threads has been experimentation, engineering, and data analysis, not fund raising. Using the correct terminology for these efforts is befitting of experimentation, engineering, and data analysis.
What are you really looking for with respect to "practical use?" Do you mean to ask what an EM drive would be useful for, should it be proven to be a new physics effect rather than spurious thermal, mechanical, and/or electrical interactions? If it works at all, most satellites will not run out of fuel for station keeping until the electrical systems break down. If the effects are moderately strong, missions like Dawn could perform observations of any number of celestial bodies (ranging from asteroids, to comets, to moons, to planets) as long as the electrical systems keep working. If extraordinary thrust levels of several newtons per kilowatt could be realized, the rocket engine would be irrelevant. These potential practical applications of such technology were offered in the NSF article. -
#1328 by Johnny_Tsunami on 05 Jan, 2016 19:07
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Schlieren photography, caught by surprise.
https://www.youtube.com/watch?v=z0xgQn7NTL8&feature=youtu.be
Sunlight through a draped sliding glass door catching heat rolling off the gas fireplace and showing against the opposite wall. I have seen the diagrams to make this happen on purpose, didn't know you could see it just by happenstance. It would probably be easier for SeeShells or rfmwguy to design a setup to use in their build for data as I know people would like to see if and how the frustum might radiate heat away.
But I though it might be fun to show you what I saw as a completely random event and in fact I know I have seen this before at different times and paid no attention to it. This was at Seaside on the Oregon Coast a few days ago.
John -
#1329 by Fugudaddy on 05 Jan, 2016 19:17
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(Mod removed post)
Whoa, take a breath there, Moe.
The DIYers on this particular site are attempting to help isolate what, if anything, is causing this anomalous effect that appears to act like 'thrust' in a setup that should otherwise not have any movement. They're not doing it to win Nobel prizes or bring home big bank but rather motivated by the thrill of discovery, as they have for their whole lives.
The problem with the 'money people' is that nobody yet understands how thing works or even IF this thing works as advertised. I'm sure @TheTraveller can point you to a raft of documentation where Mr. Shawyer attempted to get investment (to arguably different levels of success depending on who you talk to) for his EM Drive, so your frothing is out of place in regards to that since he's apparently been doing this work for a decade+ now.
The practical benefits to the EM drive have been detailed and discussed in detail inb earlier threads. The largest and easiest to understand is 'effective space travel' due to more efficient drives, but there's also cheaper satellites, interplanetary travel on a month rather than year timescale, flying cars, etc.
In the interests of simplicity:
Microwaves are put into an oddly shaped copper can and they make it move. Nobody knows how. If the 'how this happens' can be figured out, many people in the rocket business may need to find new work. PM me for my address to send me my check :|
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#1330 by rfmwguy on 05 Jan, 2016 20:06
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Just a housekeeping note...a dear friend just reminded me that not all our posts have to be elegant or even correct, people here will quickly note errors made...ok, so I've learned the hard way
However, civility, on topic and respectfulness should always be strived for. This is a place of record, however modest, and tone carries a lot of weight up the chain of command at nsf. It is not, to the best of my understanding, a wide open, no holds barred public forum. There are many other outlets for that.
In summary, if you don't agree with this, you're all a bunch of doodyfaces
Carry on... -
#1331 by rfmwguy on 05 Jan, 2016 21:27
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Math time if anyone is interested...earlier topic today was thermal expansion of moment arm of balance beam. So here's an emdrive math problem based on a real test stand:
A balanced mass of 3.35 kg hangs 53.5 inches away from its central balance point on a wood beam whose width is 1 inch and height is 0.75 inches. The wood beam has a linear expansion coefficient of 3. What is the linear expansion amount of the entire moment arm and the heat required (over an ambient of 26°C) to shift the balance by 50 micronewtons of force, or 5.1 milligrams?
Real world test senario...Go!
p.s. don't make me post a cricket picture
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#1332 by Rodal on 05 Jan, 2016 21:48
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Math time if anyone is interested...earlier topic today was thermal expansion of moment arm of balance beam. So here's an emdrive math problem based on a real test stand:
A balanced mass of 3.35 kg hangs 53.5 inches away from its central balance point on a wood beam whose width is 1 inch and height is 0.75 inches. The wood beam has a linear expansion coefficient of 3. What is the linear expansion amount of the entire moment arm and the heat required (over an ambient of 26°C) to shift the balance by 50 micronewtons of force, or 5.1 milligrams?
Real world test senario...Go!
p.s. don't make me post a cricket picture
A coefficient of thermal expansion of 3 (1/degK) for spruce wood is not a real world example.
Although the thermal expansion coefficient of ovendry wood parallel to the grain has values that range from about 3.1 to 4.5 × 10-6 1/degK (1.7 to 2.5 × 10-6 °F^(–1)), I don't recall you stating that you oven dried your beam (you would need a long oven for that). Even if you would oven dry the spruce wood, it would have absorbed very readily the moisture in the air during the time at which you did your experiments in your garage.
You see, wood that contains moisture reacts differently to varying temperature than does nearly ovendry wood.
When moist wood is heated, it tends to expand because of normal thermal expansion and to shrink because of loss in moisture content. Unless the wood is very dry initially (perhaps 3% or 4% moisture content or less), shrinkage caused by moisture loss on heating will be greater than thermal expansion, so the net dimensional change on heating will be negative.
I know that from measuring thermal expansion of polymer materials at our R&D Center with TMA and different instruments. The expansion under temperature changes depends on the water content. Notice that I am not talking here about the water absorption or diffusion (usually governed by Fick's law), but I am talking about the fact that wood products have different amounts of expansion upon rapid temperature changes, depending on the water content. It has a complicated rheological behavior !
Wood at intermediate moisture levels (about 8% to 20%) will expand when first heated, and then gradually shrink to a volume smaller than the initial volume as the wood gradually loses water while in the heated condition.
Even in the longitudinal (grain) direction, where dimensional change caused by moisture change is very small, such changes will still predominate over corresponding dimensional changes as a result of thermal expansion unless the wood is very dry initially. For wood at usual moisture levels, net dimensional changes will generally be negative after prolonged heating.
As you may be unfamiliar with this fact, this is known to people working with composite materials: even with carbon epoxy, kevlar epoxy and glass epoxy composites. (Because the polymer matrix itself absorbs moisture and this affects its expansion properties). So for such materials, one has to take into account hygrothermoelastic properties.
So, no that is NOT a real world scenario.
A real world scenario (when dealing with wood and composites exposed to normal ambient conditions) is to take into account moisture content.
At our production facilities we even had to have Kevlar and different composites stored in special rooms with sophisticated humidity control, as well as processing such polymers under humidity control.
We had products where (due to residual stresses) these effects were large enough to fracture the composite ! if these effects were not taken into account. -
#1333 by rfmwguy on 05 Jan, 2016 21:56
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Good comments, the wood was lightly sprayed with enamel paint to minimize changes in moisture content. For the purpose of this question, assume stable moisture content of a dried hardwood.
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#1334 by RotoSequence on 05 Jan, 2016 21:59
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A real world scenario (when dealing with wood and composites exposed to normal ambient conditions) is to take into account moisture content.
That goes some lengths to explain why they're moving away from composite deckhouses on the remaining Zumwalt class ships. </tangent>
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#1335 by lmbfan on 05 Jan, 2016 22:07
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Math time if anyone is interested...earlier topic today was thermal expansion of moment arm of balance beam. So here's an emdrive math problem based on a real test stand:
A balanced mass of 3.35 kg hangs 53.5 inches away from its central balance point on a wood beam whose width is 1 inch and height is 0.75 inches. The wood beam has a linear expansion coefficient of 3. What is the linear expansion amount of the entire moment arm and the heat required (over an ambient of 26°C) to shift the balance by 50 micronewtons of force, or 5.1 milligrams?
Real world test senario...Go!
p.s. don't make me post a cricket picture
Notwithstanding Dr. Rodal's post above, with a coefficient of 3e-6 m/mK, you are looking at on the order of 4e-6 m per degree K, over a length of 1.3589 m. A change in 5.1 mg of 3.35 kg over the same length is ~ 2e-6 m. Evenly heating the wooden beam by .5 degree would cause this force. The equations are linear, so this force is seen if 1/10th of the beam is heated by 5 degrees.
maths:
L = 53.5 * .0254 = 1.3589 m
Beam is centered, L = L1 and L2
Masses are balanced, M = 3.35 kg = M1 and M2
dM = 5.1 mg = 5.1e-6 kg
L1 = L2*M2/M1 = 1.35889793 m
dL = L1-L2 = 2.07e-6 m
C=3e-6m/mK
dT = 1 degree K
dL = L*C*dT = 4.077e-6m -
#1336 by Rodal on 05 Jan, 2016 22:07
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Good comments, the wood was lightly sprayed with enamel paint to minimize changes in moisture content. For the purpose of this question, assume stable moisture content of a dried hardwood.
But lightly spray painting wood siding on homes did not prevent water absorption (and hence hygrothermal changes in length) and wood decay. It may slow it down and decrease it. It did not prevent wood companies that were marketing wood composite siding products for houses to incur large liabilities due to malfunctioning of their products (now HardiPlank and such are used for siding instead which are a cement product instead).
I guess you are asking us to idealize the problem, and assume that the light spray painting will practically eliminate hygrothermal changes in length.
The point here is that the thermal expansion and the stiffness of wood is different at different water content, so even if you completely encapsulate wood with an impermeable material, I think that the change in length will be different for wood that was exposed for a long time to 80% humidity than oven dry wood, because it has a greater water content and water affects the properties of wood. So, here I am from Missouri: show me.
The coefficient of thermal expansion of your beam would need to be measured by experiment, rather than assumed from a table for oven dry wood
===>In this respect you may be better off using SeeShell's pultruded carbon epoxy beam, because the carbon fiber is much stiffer than wood, and the carbon is unaffected by water, and pultrusion gives you a high percentage of fibers in the longitudinal direction <===
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#1337 by rfmwguy on 05 Jan, 2016 22:27
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Ding ding ding! No cricket pic needed. I had only gotten to a moment arm length increase of about 2 micrometers and had not mathed it back via a temperature coefficient.Math time if anyone is interested...earlier topic today was thermal expansion of moment arm of balance beam. So here's an emdrive math problem based on a real test stand:
A balanced mass of 3.35 kg hangs 53.5 inches away from its central balance point on a wood beam whose width is 1 inch and height is 0.75 inches. The wood beam has a linear expansion coefficient of 3. What is the linear expansion amount of the entire moment arm and the heat required (over an ambient of 26°C) to shift the balance by 50 micronewtons of force, or 5.1 milligrams?
Real world test senario...Go!
p.s. don't make me post a cricket picture
Notwithstanding Dr. Rodal's post above, with a coefficient of 3e-6 m/mK, you are looking at on the order of 4e-6 m per degree K, over a length of 1.3589 m. A change in 5.1 mg of 3.35 kg over the same length is ~ 2e-6 m. Evenly heating the wooden beam by .5 degree would cause this force. The equations are linear, so this force is seen if 1/10th of the beam is heated by 5 degrees.
maths:
L = 53.5 * .0254 = 1.3589 m
Beam is centered, L = L1 and L2
Masses are balanced, M = 3.35 kg = M1 and M2
dM = 5.1 mg = 5.1e-6 kg
L1 = L2*M2/M1 = 1.35889793 m
dL = L1-L2 = 2.07e-6 m
C=3e-6m/mK
dT = 1 degree K
dL = L*C*dT = 4.077e-6m
The linear equation is good, because exposure to heating of the beam would only be in the 10% or so category, making it 5 degree heating equaling a 50 micronewton force level.
Although I seriously doubt the beam heated this much since I did laser spot stuff around it, my experiment and maybe others will benefit from thermal shielding part of the moment arm....just in case.
See...math can be fun, but dont tell anyone I said so.
Thank you
http://stream1.gifsoup.com/view2/4681357/applause-o.gif -
#1338 by glennfish on 05 Jan, 2016 22:37
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Good comments, the wood was lightly sprayed with enamel paint to minimize changes in moisture content. For the purpose of this question, assume stable moisture content of a dried hardwood.
But lightly spray painting wood siding on homes did not prevent water absorption (and hence hygrothermal changes in length) and wood decay. It may decrease it. It did not prevent wood companies that were marketing wood composite siding products for houses to incur large liabilities due to malfunctioning of their products (now HardiPlank and such are used for siding instead which are a cement product instead).
I guess you are asking us to idealize the problem, and assume that the light spray painting will practically eliminate hygrothermal changes in length.
Groan!
This discussion of thermal expansion due to thermals only reinforces the observation that the "expected" thrust is in the weeds.
IMHO, the only way out of the weeds is with sufficient replications with a given device to drive the signal out of the weeds if it's there. At the same time, weed stomping through analysis of how to grow the weeds is absolutely a good idea, but... if a 1kw magnetron is producing on a good day 100 micro-newtons of real thrust, and the weeds are wandering around 50-150 micronewtons per weed, it's going to take a lot of trials to get any statistical confidence that there's a weed-hopper in them thar weeds.
My take-away is, he/she who thrusts next has got to get themselves psyched up for 100 + trials with data taken every few milliseconds if practicable with the ability to rotate frustrums on demand for another 100 + trials.
I can't see this issue locking down soon if the expansion coefficent of wood plus lacquer has to be accounted for with each run. I can just picture Imbfan demanding thermal shots of each portion of the beam at 1 second intervals and developing a balance beam forecast for each set of measurements.
In the K.I.S.S. principle that I love and have profited from, I strongly advocate taking all the weeds and lumping them together as a coefficient w and trying to find a signal s where the model says thrust = f ( w, s), then altering the test conditions for w where whatever w is, the trial count permits s to emerge, if it's there, statistically. Absent a definition of f I can't think of any other way to hunt for s. -
#1339 by OnlyMe on 05 Jan, 2016 22:39
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I have seen a lot of hardwood flooring that buckled from weather and water damage. Even one gym floor that buckled so bad you could walk up and drop a basket ball through the hoop. The buckling I have seen has always been width not length.
Most siding on building is not sealed all sides and moisture does get in at the joints, or due to poor upkeep of the finish.
The only realistic way to try and control for any expansion of a white oak balance arm would be to set up the balance with a dummy load. Set up the magnetron without hanging it from the beam. Turn on the magnetron, and measure any changes in the balance. Repeat for time durations expected for experimental runs and record the results.
You may have more issues with the tension wire heating... That might be managed by adjusting tension on each leg of the balance independently, such that a change on the side with the magnetron would not alter the tension on the scales side of the balance. But even that would need to be tested under similar conditions, as just mentioned.
