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hrmmm..... is this real?

Posted by: Sigma - Sun Aug 25, 2013 1:56 am
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hrmmm..... is this real? 
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Post Re: hrmmm..... is this real?   Posted on: Wed Aug 06, 2014 1:19 pm
If were are going for humour about it

https://xkcd.com/1404/

:wink: :twisted:

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Post Re: hrmmm..... is this real?   Posted on: Thu Aug 07, 2014 3:21 pm
I have to admit I get excited about such kind of news very easily. :oops: :roll:

However, my enthusiasm died down quite a bit when I read the abstract of the paper cited in the news:
a) they measured thrust on the "Null device" which was supposed to produce no thrust at all. That should get everyone's "measurement-error alarm bells" ringing!
Unfortunately the abstract didn't mention if the measured thrust was the same or significantly different (but since the level was so low they might not have been able to determine this).
b) they tested the device in a steel vacuum chamber (which should rule out interactions with Earth's magnetic field if I remember electromagnetism correctly), BUT at ambient atmospheric pressure? wtf?
They are testing a device which uses several kilowatts of power to shoot microwaves at the atmosphere and then wonder about a tiny, tiny, tiny amount of "thrust"? :wink:

Before they do some proper testing, I won't be expecting practical thrusters in my lifetime. :P


@ SBSP
That will be used more and more in the near future, just like it is used already: for orbital infrastructure. I don't expect it to be used for terrestrial power demand (even though the magnifying glass vs. ants situation is easily avoided), simply because of economic reasons.

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Post Re: hrmmm..... is this real?   Posted on: Fri Aug 08, 2014 2:18 am
It has the potential to become another scientific mirage like hot/cold fusion. Always just out of reach...


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Post Re: hrmmm..... is this real?   Posted on: Fri Aug 08, 2014 8:09 am
http://www.libertariannews.org/wp-conte ... dyEtAl.pdf

Acccording to this they did test it in an evacuated vacuum chamber not at atmospheric pressure. Unless I misread their paper.

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Post Re: hrmmm..... is this real?   Posted on: Fri Aug 08, 2014 1:28 pm
box wrote:
http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf

Acccording to this they did test it in an evacuated vacuum chamber not at atmospheric pressure. Unless I misread their paper.


It could be that the vacuum was not that hard and what has been seen is something like the effect of a Radiometer https://en.wikipedia.org/wiki/Radiometer much as I would like something like this to be true(especially the superconducting version from the extrapolated numbers) and it has some interesting theories associated with it. Extraordinary claims do need extraordinary proof its very easy to believe in a perpetual motion machine that is producing macro amounts of electricity 24/7 for a year but if you are only getting anomalous results in the micro and nano amounts it takes a bit longer for the belief in the results to set in.

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Post Re: hrmmm..... is this real?   Posted on: Tue Aug 12, 2014 9:28 am
@ box
I haven't had time to read the full paper yet, but the abstract here says explicitly that the test was conducted at ambient pressure:
http://ntrs.nasa.gov/search.jsp?R=20140006052
Quote:
Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric pressure.


Funny that this "libertariannews" page that you linked to made the full pdf available, because at aiaa you have to pay to get access
http://arc.aiaa.org/doi/abs/10.2514/6.2014-4029

Edit: The abstract of the full pdf contains some interesting information:
Quote:
During the first (Cannae) portion of the campaign, approximately 40 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 935 megahertz and 28 watts. During the subsequent (tapered cavity) portion of the campaign, approximately 91 micronewtons of thrust were observed in an RF resonant cavity test article excited at approximately 1933 megahertz and 17 watts.

a) The powerlevels were a lot lower than what I was expecting.
b) The "null" test article produced twice the amount of thrust of the the "proper" thruster?

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Post Re: hrmmm..... is this real?   Posted on: Tue Aug 12, 2014 1:12 pm
Ok so I could not resist and read the paper (despite having other work to do :p )

So a number of clarifications:
*) They did not test any device in vacuum! While they spent a lot of time describing how the vacuum chamber works with all the different vacuum pumps, they only mention this important fact in one sentence at the end in "summary and forward work":
Quote:
Vacuum compatible RF amplifiers with power ranges of up to 125 watts will allow testing at vacuum conditions which was not possible using our current RF amplifiers due to the presence of electrolytic capacitors.
(emphasis mine)
So this is planned for the next set of tests.

*) They did not test two devices (one "proper" test article and a null test article), but actually 3 devices plus a "dummy" (they write about a "50 ohm RF resistive load", so I assume basically a resistor?) to rule out any electromagnetic effects that are a result of all the required wiring to power the test article.

The devices were:
1) Two "Cannae drives" (they look like an oblate spheroid with a tube sticking out at the center of each "flat" side, one shorter, one longer) One article with "slots" on the inside of the spheroid, one without. According to the "inventor", those slots are required to produce thrust, but the device without slots produced the same amount of thrust (within 2% difference).
The authors speculate that the thrust may actually be the result of a dielectric "slug" in the longer tube that was common to both designs:
Quote:
The longer beam pipe is the RF drive antenna that in practice ends up being a ¼ wave resonance system in its own right and has a dielectric PTFE slug in the throat in both the slotted and null test article. It is this characteristic that became an item of further consideration after completion of the test campaign.

In other (my) words, this part basically resembles the "EmDrive", so the Cannae drive "accidentally" includes an EmDrive. ;)

2) A "RF resonant tapered cavity" aka "EmDrive".
This looks like a truncated cone and if I read the paper right, one side also contains a dielectric resonator. This device produced more than twice the amount of thrust of the "Cannae drive"

*) In the setup for the "Cannae drive", but with the "dummy" resistive load instead of the "Cannae drive", no significant thrust could be measured.

*) In the (different) setup for the "EmDrive" the test using the dummy instead of the "EmDrive" produced a small amount of thrust resulting from electromagnetic interference with the dampening system of the isolation table. This thrust (about 1/10th the amount of the test device) was subtracted from the "raw" measured thrust of the device to obtain the actual thrust.

*) Follow up tests at other centers are already planned:
Quote:
The current plan is to support an IV&V [independent verification and validation, note by M.Z.] test campaign at the Glenn Research Center (GRC) using their low thrust torsion pendulum followed by a repeat campaign at the Jet Propulsion Laboratory (JPL) using their low thrust torsion pendulum. The Johns Hopkins University Applied Physics Laboratory has also expressed an interest in performing a Cavendish Balance style test with the IV&V shipset.


So basically the test setup wasn't as "fishy" as some reports implied. However, I will wait until someone can reproduce the results in vacuum before I get excited again ;)

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Post Re: hrmmm..... is this real?   Posted on: Tue Aug 12, 2014 2:09 pm
I'm less worried about the vacuum than the fact that they had high voltage electric fields and were flinging EM with abandon in close proximity to a steel vacuum chamber. Even if it were a non-magnetic alloy, the iron in it will influence the field.

The is lots of fun speculation on arocket about this thing.


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Post Re: hrmmm..... is this real?   Posted on: Sun Aug 17, 2014 4:53 am
I knew I missed something when I was reading it. :D

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Post Re: hrmmm..... is this real?   Posted on: Sun Aug 17, 2014 4:58 am
Assuming it works, how small could one make these? Could there be a cubesat version done to do some cheap testing in orbit?

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Post Re: hrmmm..... is this real?   Posted on: Sun Aug 17, 2014 12:59 pm
box wrote:
Assuming it works, how small could one make these? Could there be a cubesat version done to do some cheap testing in orbit?


Well "Normal" microwaves quite often have wavelengths in the several centimetres range so depending on how many internal antenna they have in their microwave resonance box might limit it's minimum size and if the virtual particle thing is true then I suspect they will be tuned to 21cm for basic hydrogen to absorb and emit. So I suspect 21cm will be the minimum size but more likely a multiple of it if the bits of hand wavy theory I have seen have anything to do with reality. :wink: :twisted:

PS I know you can make half wave and quarter wave antennas but I suspect for accurate resonance manipulation you would probably need a full length one if not a bit more for full control IMHO.

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Post Re: hrmmm..... is this real?   Posted on: Sun Aug 17, 2014 6:28 pm
It will really depend on what this actually responsible for this phenomenon. If its just some quantum Brownian effect or even a more elaborate behavior of an excited resonance, there is no reason why it should be limited to this material and frequency. So you could go to something much more dense and high energy like X-rays, and with then you could take it down to the nano scale.


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Post Re: hrmmm..... is this real?   Posted on: Tue Sep 09, 2014 8:51 pm
A bit more of an update on NASA cannae drive and emdrive

http://nextbigfuture.com/2014/09/nasa-c ... drive.html

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Post Re: hrmmm..... is this real?   Posted on: Sat Nov 01, 2014 3:03 pm
The emdrive is still being discussed like the could fusion e-cat it would be nice if it was real but it sure is taking a long time for a practical safe version that can be sold to members of the public with money back guarantees that are honoured for non functional ones. My cynicism is beginning to overtake my optimism I liked the idea of bouncing microwaves of virtual partials it had the sound of a practical Maxwell's Demon. I also liked the idea of slow neutrons. Together if true we may soon be entering a future with an interesting range of toys. But if they are both scams they are wasting the time of a lot of honestly intrigued minds. Time will tell I suppose.


http://nextbigfuture.com/2014/10/roger- ... drive.html

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