EM drive apparently works (nasa leak)

[rustigsmed (Russell)]

http://www.sciencealert.com/leaked-n...ally-does-work

The results of NASA's tests on the 'impossible' EM Drive have been leaked, and they reveal that the controversial propulsion system really does work, and is capable of generating impressive thrust in a vacuum, even after error measurements have been accounted for.

The EM Drive has made headlines over the past year, because it offers the incredible possibility of a fuel-free propulsion system that could potentially get us to Mars in just 70 days. But there's one major problem: according to the current laws of physics, it shouldn't work.

[bojan]

Hmm, amazing..
Still, a tiny thrust and very low efficiency compared to what we have when electrical energy is converted into mechanical with electric motor (where efficiencies of up to 80% are normally achieved).

[deanm (Dean)]

Bojan - yours are almost the same words used when the jet engine was first revealed to the world..!

Look at where we are today.

And it's not easy using mechanical means of propulsion in space (how would it work?)

Dean

[bojan]

Originally Posted by deanm

Bojan - yours are almost the same words used when the jet engine was first revealed to the world..!

Look at where we are today.

And it's not easy using mechanical means of propulsion in space (how would it work?)

Dean

Your example about jet engine is not quite right - rockets (for fireworks... around for a very long time now) are jet engines in principle and are pretty efficient (1~10%?) and the trust is quite useful.

However, I am not saying this story with EM drive is a dead-end street.... like the story about cold fusion.
I am not questioning the theoretical explanation from Finland group... it seems to be a bit "stretched", just like dark matter..
The problem I have is, the effect is not obvious at all (tiny), otherwise it would have been noticed much earlier (for example, radar technology is using MW and sometimes GW of power.. and no one reported any sort of non-accountable stresses in such equipment so far.
So... I don't know, time will tell.

EDIT:

My question should have been something like this:
Given that resulting thrust from EM drive is a consequence of paired photons leaking out of the resonator (while the rest are waisted as losses in the walls of the resonator (heat)), could we expect at all (in theory and practice) the thrust any larger than the one obtained with transmitter pumping power into high efficiency narrow band antenna?
Or by using light sail for example (which is almost the same thing as antenna... it is reflecting photons and producing thrust coming from reflected photon's momentum)?

[bojan]

"energy from nothing" ??
What an ignorance... the writer of this article only showed they do not understand what they are writing about
http://www.news.com.au/technology/sc...7fe443af1f47d6

[glend (Glen)]

Apparently passed peer review in latest article.

[xelasnave]

The last time I looked the Pioneer anomoly was explained away due to heat radiating and causing acceleration in the dire tion of the Sun, I think thats the way it was put.

Is this new thing anyway simlilar?
Alex

[bojan]

Originally Posted by xelasnave

The last time I looked the Pioneer anomoly was explained away due to heat radiating and causing acceleration in the dire tion of the Sun, I think thats the way it was put.

Is this new thing anyway simlilar?
Alex

Yes, similar...

It seems in this case the thrust is due to "paired" photons that escape the resonant cavity.

The problem is, this way of propulsion is even less efficient than simple parabolic antenna fed with transmitter, because not all photons escape from resonant cavity (those trapped simply provide heating of the cavity walls due to losses).

If the measurement results are real (they still need to be confirmed by independent party me thinks), this will only be a interesting curiosity IMO, with very dubious application value... very far cry from "revolution in space flight", as some would like it to be.

See more here from paper:
https://www.reddit.com/r/EmDrive/com...he_exhaust_of/
New EM-Drive Paper: On the exhaust of electromagnetic drive
(http://www.helsinki.fi/~aannila/arto/emdrive.pdf)
The paper is written by Arto Annila, a Professor in Physics at the University of Helsinki, Erkki Kolehmainen, a Professor of Chemistry at the University of Jyväskylä and Patrick Grahn, an engineer with a specialization in COSMOL Multiphysics at the University of Helsinki.
The abstract to the paper notes:
" Recent reports about propulsion without reaction mass have been met with disbelief. Closed metal cavities, when fueled with microwaves, have delivered thrust without any apparent exhaust. Thus the Law of Action-Reaction seems to have been violated. We consider the possibility that the exhaust is in a form that has so far escaped both experimental detection and theoretical attention. In the thruster’s cavity microwaves interfere with each other and invariably some photons will also end up co-propagating with opposite phases. At the destructive interference electromagnetic fields cancel. However, the photons themselves do not vanish for nothing but continue in propagation. These photon pairs without net electromagnetic field do not reflect back from the metal walls but escape from the resonator. By this action momentum is lost from the cavity which, according to the conservation of momentum, gives rise to an equal and opposite reaction. We examine theoretical corollaries and practical concerns that follow from the paired –photon conclusion."

[xelasnave]

It is wrong to dismiss things as a general proposition but, and I am not qualified to critisize, this seems much like an anti gravity device I saw years ago.

If this gets up there must be hope for push gravity.

I bet next they will suggest it can be powered by cold fusion.

As someone else said elsewhere to the effect he will wait until they are in space powering craft I to will wait.

Alex

[bojan]

Alex,
Someone made the calculation of thrust produced by parabolic antenna, fed with the same power (I forgot where I saw this, sorry)
The measured efficiency of this thing (Thrust/kW) is about 1/10 of much simpler and common antenna-transmitter system.

I mentioned elsewhere in this forum, if this effect is really real, it must have been noticed when operating MW (and this is quite moderate output for military radars, not to mention radars used in studies of planets and asteroids) radar equipment.. and it wasn't, never as far as I am aware.

[xelasnave]

Thanks Bojan.
If nothing else it will keep some families fed.
And I guess we do need toknow what cant be done.

However if you think about it there must be an ocean of nutrinos out there, as well as push itrons now if you could interact 100% or close to that a torch beam should do the job.
Is that an idea worthy of funding or what?

Alex

[bojan]

O yes, with push_itrons and Em drive combined with neutrinos, we could be on Mars tomorrow

[xelasnave]

Originally Posted by bojan

O yes, with push_itrons and Em drive combined with neutrinos, we could be on Mars tomorrow

Alex

[glend (Glen)]

Close minds make little progress. Looking back at technology development and accepted doctrine, every generation has had their beliefs challenged by new ideas and developments. If we have to modify the "Third Law" slightly, as suggested in the article today, so be it. I like the idea of simply putting it in space and watching what happens to it.

[xelasnave]

Originally Posted by glend

Close minds make little progress. Looking back at technology development and accepted doctrine, every generation has had their beliefs challenged by new ideas and developments. If we have to modify the "Third Law" slightly, as suggested in the article today, so be it. I like the idea of simply putting it in space and watching what happens to it.

Ere
The things we treat as everyday today mostly were beyond imagination even when I was a boy and that was not that long ago.
I remember playing tic tac toe with the computer in the Museum in Ultimo I, Harris Street?, and no one thought it was more than wa novelty.
Flight... I worked for a man who grew up in an age where there was no flight... Who can imagine that.... When he was a kid if anyone would have suggested man would fly would not be taken seriously.
Sunday trading now so normal but once not one shop was open on Sunday.
So things change new things happen... So we must keep our minds open...
Alex

[bojan]

Yes, open mind is OK... but to a good measure.
The saying "they didn't know it's impossible so they just did it" simply doesn't work.

I remember a discussion here couple of years ago about "programmable" filters...
There was a guy on the forum with idea to use colour LCD as monochromatic narrow band filter.., No argument was acceptable to him because from the start he didn't understand the difference between colours as perceived and colours in spectrum of light.
I gave up explaining and he said he will come back to report success.. which never eventuated.

[The_bluester (Paul)]

Originally Posted by bojan

Alex,
Someone made the calculation of thrust produced by parabolic antenna, fed with the same power (I forgot where I saw this, sorry)
The measured efficiency of this thing (Thrust/kW) is about 1/10 of much simpler and common antenna-transmitter system.

I mentioned elsewhere in this forum, if this effect is really real, it must have been noticed when operating MW (and this is quite moderate output for military radars, not to mention radars used in studies of planets and asteroids) radar equipment.. and it wasn't, never as far as I am aware.

I would note a major difference there (As an ex RADAR tech) Unless we are talking about something space based where effects might stack up, RADAR antennas are generally quite robust and are often quite large and have to withstand large wind loads. Similarly, waveguides are generally quite rigid and are bolted to support structures so I would not expect to see effects that would be measured probably in millinewtons at most being noticed in a RADAR system.

[bojan]

Originally Posted by The_bluester

I would note a major difference there (As an ex RADAR tech) Unless we are talking about something space based where effects might stack up, RADAR antennas are generally quite robust and are often quite large and have to withstand large wind loads. Similarly, waveguides are generally quite rigid and are bolted to support structures so I would not expect to see effects that would be measured probably in millinewtons at most being noticed in a RADAR system.

Quite valid point... and I am confirming that as another ex-radar technician (I worked with 500kW meteorological radars back in '80's).
Most mechanical vibrations present were coming from cooling fans and pulse transformer windings.
It is also true that since the effect was negligible (if there at all) in amplitude, no one would go into it to find out what was happening.

[The_bluester (Paul)]

Yeah, not saying that there would be no effect there, but I think it would get lost in the forces already apparent on antenna systems and everything else is pretty rigid.

I worked on air traffic control RADAR systems so on the primary RADAR side the two I woked on ran from about 1.2MW to about 1.4MW. there is some conjecture on the 1.4MW one, it was never really measured as such but 1.4mw out was the original rater power (Per transmitter that is, and there were two primary transmitters at each site apart from the maintenance test bed, operating at slightly different frequencies through a diplexer) but it was getting to end of life when I worked on it and we kept the HV wound down a bit to reduce output and preserve the harder to get bits like magnetrons and thyratron tubes for a 30 year old system.

[bugeater (Marty)]

I'd be cool if it works as advertised, but as the saying goes "extraordinary claims require extraordinary evidence".

I used to work in venture capital and one of my tasks was dealing with unsolicited emails to the firm asking for investment. There are a lot of crazies out there with perpetual motion machines. I'd always have a look and give a polite reply, but it was always tempting to say to them "our investment mandate does not cover violations of the laws of physics" or something to that effect.