Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1877636 times)

Offline rfmwguy

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15 years? I had no idea that Shawyer had been fiddling about for so long with this.

I have been suspect of several research projects that seem to be extended for dubious reasons. Trouble with emdrive, its simplicity puts it into a broad realm of experimentors...no exotic componentry.

Question I have is why it took so long for experimentors to focus on it. I know electronics is now plug and play, but 15 years to get general intention? Curious...

Offline Rodal

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..
Thanks for your input, it means a lot.

I plan to keep to keep one end of the frustum exposed about 10 mill above the water and I'll be happy to get a max of 1 mill of Z deviation.

I calculated  (http://forum.nasaspaceflight.com/index.php?topic=37642.msg1387567#msg1387567) (where z is the deviation from the level of the water)

for 50 microNewtons , z = 0.08 micrometers

for 600 microNewtons z = 1 micrometers

for 300 milliNewtons z= 500 micrometers
« Last Edit: 06/10/2015 10:14 PM by Rodal »

Offline Prunesquallor

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https://hackaday.io/project/5596-em-drive

So how are we going to pull N/W out of that data? Or mN/mW?

Without a non-thrusting baseline or knowing when the thrusters were turned on, I don't know how one would pull any data out of this.
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Offline deltaMass

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https://hackaday.io/project/5596-em-drive

So how are we going to pull N/W out of that data? Or mN/mW?

Without a non-thrusting baseline or knowing when the thrusters were turned on, I don't know how one would pull any data out of this.
The legend tells you when the thrusters turn on. Vertical red line

Offline aero

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https://hackaday.io/project/5596-em-drive

So how are we going to pull N/W out of that data? Or mN/mW?

Without a non-thrusting baseline or knowing when the thrusters were turned on, I don't know how one would pull any data out of this.
The legend tells you when the thrusters turn on. Vertical red line

It also says that it was initially spun countercloskwise - so which end was leading, big or small?
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Offline SeeShells

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https://hackaday.io/project/5596-em-drive

So how are we going to pull N/W out of that data? Or mN/mW?

Without a non-thrusting baseline or knowing when the thrusters were turned on, I don't know how one would pull any data out of this.
The data? It was the big data they were after and it seemed to work. Looks like they are doing things to eliminate errors and seem to be doing it to gain solid data upon further testing.
My hat's off to them and they just stirred the big ant pile. ;)
« Last Edit: 06/10/2015 10:21 PM by SeeShells »

Offline wallofwolfstreet

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Here is a google doc that reddit user /u/TortugaTerritory put together that overlaps the figures and draws some trendlines (posted with his/her permission).  Helps to make some of differences clearer. 

https://docs.google.com/presentation/d/11TVN9vE_ZB7NjdB05UzJDJjjoQsGCNWWyQl5L70jAF4/edit?pli=1#slide=id.gb342f84ab_0_61

I assume small end was leading as thrust comes out the back(large end)

Offline fasmax

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Hopefully they rotate the drive 180 deg and run the experiment again.

Offline TMEubanks

Everyone check out Hackaday.io! Results are up and data is looking good.

Maybe I am missing something, but what is exciting about having the device spin slower in both prograde and retrograde configuration? Are we sure that's not just friction? Have they tried to spin it up?

Offline rfmwguy

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Everyone check out Hackaday.io! Results are up and data is looking good.

Maybe I am missing something, but what is exciting about having the device spin slower in both prograde and retrograde configuration? Are we sure that's not just friction? Have they tried to spin it up?

Hard to tell, if they simply reversed frustum, perhaps the relative angle of it could have been slightly different creating more air drag as it spun down. No idea at this point.

Offline fasmax

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It would have been nice to see a more pronounced effect at activation.
I think I see a slight change at activation. Prograde seem to aid the rotation and retrograde seems to reduce it.
I would not draw any conclusion until a lot more tests were run.
If the drive was rotated 180 deg and the experiment ran again it would be nice to see what happens.

Offline frobnicat

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Everyone check out Hackaday.io! Results are up and data is looking good.

Maybe I am missing something, but what is exciting about having the device spin slower in both prograde and retrograde configuration? Are we sure that's not just friction? Have they tried to spin it up?

There clearly isn't enough "thrust" (if there is thrust) to compensate friction, at least at those speeds. Actually there isn't even prograde thrust at all that would limit the decay, or if there is it appears very unconclusive to my eye, as the decay seems to continue at same rate, within margins of noise. Only in retrograde mounting there is maybe slightly more speed loss rate at activation (maybe adepts of Shawyer's theories will be delighted to see here an illustration of the distinction between motor mode and generator mode ?).

Which begs the question of what kind of friction there is ? Aerodynamic drag would tend to fall with speed, while the curves show a near linear decay in speed, constant deceleration, constant drag force... it looks more like a (very low) dry friction, until it falls below 150 and drag gets even higher. That looks contradictory to aerodynamic drag being the main contributor to the dissipative factor. This is to be characterised properly, especially if thrust effects are to be evaluated against this drag.

I wonder, they do use one of those magnetic globe levitators system, don't they ? Those toys use an active electromagnet feedback system to stabilize altitude and vertical oscillations, on top of the stronger permanent magnet that does the heavy lifting. Couldn't the periods of this feedback enter in resonance or just happen to synchronise with the rotation period, leading to net torque being communicated from the electromagnet to the levitated rig (taking into account small deviations of magnetic materials wrt perfectly axisymmetric geometry) ?

Offline Prunesquallor

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https://hackaday.io/project/5596-em-drive

So how are we going to pull N/W out of that data? Or mN/mW?

Without a non-thrusting baseline or knowing when the thrusters were turned on, I don't know how one would pull any data out of this.
The data? It was the big data they were after and it seemed to work. Looks like they are doing things to eliminate errors and seem to be doing it to gain solid data upon further testing.
My hat's off to them and they just stirred the big ant pile. ;)

Hmmm.. you're extracting more information that I can see.

What do "retrograde" and "prograde" actually mean?  Does that mean they spun the rig in the same direction and reversed thruster orientation?  Or did they leave the thruster orientation the same and reverse spin?

Why did they start the thruster at different times relative to 500 spin units?

What does a "no thrust" case look like in both directions?  How does the rig naturally despin?  That is the FIRST thing I would want to understand.

I think this just raises more confusion.

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Offline Prunesquallor

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Here is a google doc that reddit user /u/TortugaTerritory put together that overlaps the figures and draws some trendlines (posted with his/her permission).  Helps to make some of differences clearer. 

https://docs.google.com/presentation/d/11TVN9vE_ZB7NjdB05UzJDJjjoQsGCNWWyQl5L70jAF4/edit?pli=1#slide=id.gb342f84ab_0_61

See, take the last chart.  If there was a "no thrust" curve that was right between the two, I might get excited.  But for some reason, they didn't look at that?
« Last Edit: 06/11/2015 12:23 AM by Prunesquallor »
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Offline cej

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Here's a slightly clearer picture of the Hackaday.io graph.

Warning: This is not the original data; I overlaid an Excel graph over the original graph and added data points by hand. I also don't know what the units are.
« Last Edit: 06/11/2015 02:25 AM by cej »

Offline DIYFAN

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15 years? I had no idea that Shawyer had been fiddling about for so long with this.

I have been suspect of several research projects that seem to be extended for dubious reasons. Trouble with emdrive, its simplicity puts it into a broad realm of experimentors...no exotic componentry.

Question I have is why it took so long for experimentors to focus on it. I know electronics is now plug and play, but 15 years to get general intention? Curious...

There might be a confluence of factors.  However, my primary theory on this is that we live in an age of extreme skepticism.  Extreme skepticism dismisses out of hand.  Healthy skepticism considers the possibility, looks closely at the evidence, and follows the data.

Offline Prunesquallor

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Here's a slightly clearer picture of the Hackaday.io graph.

OK, so in each case I see a change in slope during thrusting that is about an order of magnitude bigger than the difference in non-thrusting slope between the two runs.  Interesting.

<edit> and in opposite directions.  Even more interesting
« Last Edit: 06/11/2015 01:05 AM by Prunesquallor »
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Offline Rodal

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Everyone check out Hackaday.io! Results are up and data is looking good.

Maybe I am missing something, but what is exciting about having the device spin slower in both prograde and retrograde configuration? Are we sure that's not just friction? Have they tried to spin it up?
Excited that, instead of copying the same dimensions used by Shawyer, Yang and NASA, Aachen fellows miniaturized it, and instead of running at 2.45 GHz they went 10 times higher to 24 GHz in unexplored territory, and that after taking these big risks they are reporting seeing a thrust signal.   :)

Having said that, the signal-to-noise ratio is, shall we say, Ahem, unexciting ?   :)

Disturbing to se the EM Drive's strange preference of one direction vs. another (reminds me of the issue with NASA turning it around by 180 degrees). 

Hope that they continue, that they check whether they are in resonance (? never heard anything about Q, what mode shape they have, etc.) that they show null curves and they do lots more testing, and perhaps they can also try filling it with Ammonia gas (it emits at 24 GHz) ? and looking forward to vacuum testing as well...
« Last Edit: 06/11/2015 01:34 AM by Rodal »

Offline dustinthewind

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Disturbing to se the EM Drive's strange preference of one direction vs. another (reminds me of the issue with NASA turning it around by 180 degrees). 


I have been wondering if a preferred frame means that there is a specific velocity at which it appears one should be at rest.  I would suspect that this might be so.  Far away from a gravity well, maybe we can assume space is stationary, and light speed is about the same in any direction from a 3rd observer displaced from all gravity.  Inside a gravity well however, lets assume space time is moving into the gravity well.  With a black hole, at the event horizon lets say, space is moving in at the speed of light.  At that point light cant escape because space is moving in at the same speed it propagates.  Maybe we are not at rest in our own frame inside earths gravity well with respect to space. 

I once during an experiment encountered some non-symmetry that also baffled me.  We had a high resistance volt meter connected to a capacitor that was outside and concentric around a large solenoid.  It had, I think around 180 picofarads and was aluminum.  I could apply DC current through the solenoid in one direction and the voltage would rise on the capacitor and stay that way but decay as charge flowed off slowly.  If I discharged it then reversed the voltage wires so current flowed the other way through the Edit:(solenoid) then give it current the magnitude of increase in the voltage on the capacitor was about an order less. 
« Last Edit: 06/11/2015 02:03 AM by dustinthewind »

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