Author Topic: EM Drive Developments - related to space flight applications - Thread 2  (Read 2102887 times)

Offline Oberon_Command

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If the warp drive "focuses" the dirt and particles in the front of the ship, releasing them upon the field's deactivation, then that's maybe a solution to the problem of high energy impacts. And probably of dust up to certain grain size.

Maybe that's the solution to the drag problems associated with the Bussard ramjet, too, assuming you could somehow pull usable material from the "focus" in front of the starship.

Offline Mulletron

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So other than what is described in the links below, is there any proof that plane waves can travel slower or faster than c in vacuum?

http://www.sciencemag.org/content/347/6224/857
http://arxiv.org/abs/1411.3987
« Last Edit: 04/24/2015 12:02 AM by Mulletron »
Challenge your preconceptions, or they will challenge you. - Velik

Online Rodal

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So other than what is described in the links below, is there any proof that plane waves can travel slower or faster than c in vacuum?

http://www.sciencemag.org/content/347/6224/857
http://arxiv.org/abs/1411.3987

A true plane wave is a theoretical construct, it is unbounded and hence it requires an infinite amount of energy.
Ditto for true Bessel beams (amplitude is described by a Bessel function of the first kind) .   Bessel beams can be approximated by focusing a Gaussian beam.  The article states that only plane waves are invariant traveling exactly at c.   Since plane waves are a theoretical construct, this effectively states that real waves are affected.  But it may not have any appreciable effect on Astronomy (see bottom of my post), but it may affect the EM Drive)

Quote
Our work highlights that, even in free space, the invariance of the speed of light only applies to plane waves

the delay in free space is very small though:

Quote
we show a reduction in the group velocity of photons in both a Bessel beam and photons in a focused Gaussian beam. In both cases, the delay is several micrometers over a propagation distance of ~1 meter




The following is known to be true:

Quote
....The speed of light in free space propagation is a fundamental quantity. It holds a pivotal role in the foundations of relativity and field theory, as well as in technological applications such as time-of-flight measurements, and radio and satellite communication. It has previously been experimentally established that single photons travel at the group velocity

That's correct.

This is what is new:
Quote
We have now shown that transverse structuring of the photon results in a decrease in the group velocity along the axis of propagation. The effect can be derived from a simple geometric argument, which is also supported by a rigorous calculation of the harmonic average of the group velocity. Beyond light, the effect observed will have applications to any wave theory, including sound waves and, potentially, gravitational waves

Hence pertinent to the EM Drive.  But again the relative difference is only ~ 10^(-6)

EDIT: on the other hand, the effect is biggest,when the diameter of the optics used is large and the distances are short, so it is unlikely to have any impact in astronomy, but it may have an impact on the EM Drive
« Last Edit: 04/24/2015 12:31 AM by Rodal »

Offline FutureStormtrooper

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[snip]

Look at my answer above, on what I wrote after "EDIT".

I would worry much more about particles in space being “swept up” into the warp bubble and focused into regions before and behind the ship. When your warp-driven spaceship decelerates, these particles will be released in  outbursts. The forward-facing particles can be very energetic — enough to destroy anyone at the destination directly in front of you.  So, if you are planning to go on a warp-drive beware that gamma ray and high energy particles may destroy any beings on the location you are trying to reach  :)

Wormholes are more benign (if you can traverse them  :)

Easy solution: Divide your travel way into hops with very short warp deactivation phases to get rid of unwanted particle collection.

Or perhaps devise a way to siphon the particles off from within the bubble.

Speaking of which, something I've been wondering: what exactly would happen to any matter that were pushed from within the bubble out into the area of altered density space-time, say, a rod of some kind. What sort of forces/effects would the matter in the rod undergo?

Offline Stormbringer

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comments:

The alcubierre metric requires a highly contorted space time topology. The versions that require less exotic energy were initially justified by having apertures smaller than the craft. In fact alcubierre's immediate successors had their apertures at microscopic dimensions.

The region inside the bubble is flat or nearly flat. Nothing inside the interior region is moving any faster than the speed it had before entering the entire warp region. The warp acceleration is in the skin region of the bubble. Things exterior to the bubble and it's skin are traveling at their normal space speed as well. Stuff that passes into the skin are given a the warp speed multiplier only while in the skin.

According to Dr white things that encounter the warp bubble shell are only accelerated for the duration of the transit through the skin region, not inside the bubble, not outside of the bubble. The description of the status of the ship  is no different to what happens to stuff entering the bubble while it is in route.

Since apparently stuff can pass into the bubble from outside there should be no accumulation of massive particles or photons. Also there should be no real space carry over of extra velocity. So even if there were an accumulation of matter or energy it would not be ammo for a relativistic rail gun effect.

Stuff in space can only go as straight as the local curvature allows. all stuff in space follows a curved path (geodetic.) Space around the warp bubble including the skin especially is really curved.  It seems to me that at stuff could not find the front end of the bubble let alone collect there; let alone fry stuff at the departure point or destination.

Apart from Dr Whites answer to the people that proposed the gamma ray bath hazard critique my own thoughts are most stuff would be diverted around the bubble either by the geodetic phenomenon or by plain old optical rules. the interfaces between regions would act as a lens for several reasons.

On another topic you can title lab safety: the energy Dr white is liable to have available to curve space is less than the energy in a big fire cracker. So lets say milligrams to a gram of TNT equivalents. In short any destructive effects from warping space at the level he is capable of in the near to medium term is comparable to an office prank.  :)  In other words; the minor curvature distortions he can provoke are not world threatening. They aren't even building threatening. They are on the level of slightly annoying the internal OSHA and fire safety additional duty guys.



« Last Edit: 04/24/2015 01:49 AM by Stormbringer »
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Online Rodal

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On another topic you can title lab safety: the energy Dr white is liable to have available to curve space is less than the energy in a big fire cracker. So lets say milligrams to a gram of TNT equivalents. In short any destructive effects from warping space at the level he is capable of in the near to medium term is comparable to an office prank.  :)  In other words; the minor curvature distortions he can provoke are not world threatening. They aren't even building threatening. They are on the level of slightly annoying the internal OSHA and fire safety additional duty guys.

I would be surprised if anybody would disagree with that statement.  I think we all agree on that.





...
there should be no accumulation of massive particles or photons. also there should be no real space carry over of extra velocity. So even if there were an accumulation of matter or energy it would not be ammo for a relativistic rail gun effect. ... It seems to me that at stuff could not find the front end of the bubble let alone collect there; let alone fry stuff at the departure point or destination.

If you are referring to accumulation on the spacecraft itself.  The University of Sidney authors stated:

Quote
These results suggest that any ship using an Alcubierre warp drive carrying people would need shielding
to protect them from potential dangerously blueshifted particles during the journey

Shielding can be provided for blueshifted particles, so OK.




However, if you are referring to accumulation in the region of contracting space ahead of the spacecraft, those statements are in direct contradiction with the research conclusions at University of Sidney:

Quote
and any people at the destination would be gamma ray and high energy particle blasted into oblivion due to the extreme blueshifts for P+ region particles.

http://sydney.edu.au/news/science/397.html?newsstoryid=8790

http://arxiv.org/pdf/1202.5708

 if you are referring to accumulation in the region of contracting space ahead of the spacecraft, can you point out what assumptions made, or methods used, in the University of Sidney study are incorrect, in your view, that you arrive at a completely opposite conclusion?
« Last Edit: 04/24/2015 02:11 AM by Rodal »

Offline Stormbringer

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The assumptions I posted are not mine but those of Dr White when he answered critics that brought forward the particle acceleration and accumulation objections to his theory. So I am not qualified to defend them. But Mr March certainly is. I just brought them up because it appeared the thread participants were unaware of them. :)

I am sure he will address this and this should be very interesting for all involved. :)
« Last Edit: 04/24/2015 01:55 AM by Stormbringer »
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Online Rodal

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The assumptions I posted are not mine but those of Dr White when he answered critics that brought forward the particle acceleration and accumulation objections to his theory. So I am Not qualified to defend them. But Mr March certainly is. I just brought them up because it appeared the thread participants were unaware of them. :)

I am sure he will address this and this should be very interesting for all involved. :)

Is there a paper where Dr. White made those statements, or are they in a video you can link to?

I would like to see what he actually wrote or said on that matter.

EDIT: What I recall is Dr. White answering the objection to particles hitting the spacecraft at great speed, in which case his answer was correct, because high energy particles accumulate in the region of space that contracts in front of the spacecraft, and they never reach the spacecraft itself. 

Actually (hat tip to tchernik for the great insight), the research at University of Sidney supports Dr. White's answer, because  gamma ray and high energy particles don't hit the spacecraft.   The problem is just providing shielding against blueshifted particles.

I don't recall Dr. White addressing the different question of particles accumulating in front (not on the spacecraft itself) and  gamma ray and high energy particles released away from the spacecraft when the spacecraft decelerates, and "blasting beings into oblivion" ahead at their destination, as described by the University of Sidney research.


Thanks
« Last Edit: 04/24/2015 02:23 AM by Rodal »

Offline Stormbringer

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The assumptions I posted are not mine but those of Dr White when he answered critics that brought forward the particle acceleration and accumulation objections to his theory. So I am Not qualified to defend them. But Mr March certainly is. I just brought them up because it appeared the thread participants were unaware of them. :)

I am sure he will address this and this should be very interesting for all involved. :)

Is there a paper where Dr. White made those statements, or are they in a video you can link to?

I would like to see what he actually wrote or said on that matter.

Thanks
Yes. I saw it in a video of one of his presentations, -I think it was a couple of years ago. If I can find it I will certainly provide a link :)

EDIT:  Going through the videos now. I'm half way through the first video.
« Last Edit: 04/24/2015 02:31 AM by Stormbringer »
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Offline aceshigh

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The assumptions I posted are not mine but those of Dr White when he answered critics that brought forward the particle acceleration and accumulation objections to his theory. So I am Not qualified to defend them. But Mr March certainly is. I just brought them up because it appeared the thread participants were unaware of them. :)

I am sure he will address this and this should be very interesting for all involved. :)

Is there a paper where Dr. White made those statements, or are they in a video you can link to?

I would like to see what he actually wrote or said on that matter.

Thanks
Yes. I saw it in a video of one of his presentations, -I think it was a couple of years ago. If I can find it I will certainly provide a link :)

EDIT:  Going through the videos now. I'm half way through the first video.

what videos? The one I posted or other ones?


@Dr Rodal: is the release of particles concentrated and focused or would they spread? If so, would it be a matter of turning off the warp field at a safe enough distance from an inhabited planet?

obviously, you might want to turn off the warp field the closest possible to a "target".

Offline zen-in

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I would like to see more credible evidence this magnetic capacitive device generates a warp field; if that is what has been claimed.    The White-Juday Warp Field Interferometer pictures I have seen is simply some Edmund Scientific mirrors and beamsplitter mounted on flimsy stands on an open optical table.    The fringes imaged by the camera will move up or down one fringe when the path difference changes by +/- 632.8/2 nM.  There are all kinds of things that will make that happen with this imprecise setup.   Radiative heating of a mirrors surface from an object that is just a few degrees hotter, vibrations, and electrical noise are a few of the possible causes.   This is like the em-drive experiments:  No attempts have been made to rule out alternative explanations.   For example what happens when the DUT is placed outside the laser beam?    Does the "warp field" displacement still occur.  How sensitive is the interferometer to nearby objects that are being heated?    Most optical measurements are done with a dual beam setup, to cancel out drift and other common mode effects.   The measurement accuracy of White-Juday Warp Field Interferometer is questionable because there is no absolute positional reference like the white light interferogram used in FTIR instruments.    So when fringes move was it just one fringe or was it several hundred?   How is the aliasing effect of the camera factored into this?

Offline Stormbringer

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what videos? The one I posted or ot
her ones?




I started with the Icarus  sponsored International Starship Congress symposium of 2013. it is not in that one. i am proceeding through the videos as fast as i can with my feeble attention span. The next one is over an hour long. I am ten minutes through that one and taking a break from it at the moment.

« Last Edit: 04/24/2015 04:11 AM by Stormbringer »
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Offline aceshigh

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it seems some people are getting excited by the new Star Wars trailers  ;)

remember however that Star Wars uses "hyperspace", not warp drives (in the movies however, they only use the term "lightspeed")

I will be really glad if the EM Drive proves to work, no warp drive yet for a few centuries.

Plenty of stuff to do in the Solar System before we have the need to venture forth.
« Last Edit: 04/24/2015 06:00 AM by aceshigh »

Offline ThinkerX

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Quote
Plenty of stuff to do in the Solar System before we have the need to venture forth.

Well, even the sub-light version of the EM drive opens up the solar systems within a few dozen light-years to exploration and colonization, if there's anyplace worth visiting.

Offline Stormbringer

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the 4 newton version of the QVPT according to calculations using the copernicus software can send a probe to alpha proxima in 29 years of flight time; including acceleration and deacceleration time.

EDIT finished a second video. nothing yet. going on to a third video.
« Last Edit: 04/24/2015 07:08 AM by Stormbringer »
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Offline ThinkerX

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Quote
the 4 newton version of the QVPT according to calculations using the copernicus software can send a probe to alpha proxima in 29 years of flight time; including acceleration and deacceleration time.

I remember reading that.

But, going from some of the near exponential charts and graphs 'Star Drive' posted here some pages back, I suspect that projection is overly conservative.  I suspect two or three decades travel time would get the star ship out to twenty or thirty light years if those new numbers are anywhere near right. 

And even if I'm off on that...well, with missions past Alpha Centauri, the starship would keep accelerating to the journey's midpoint, which means that a trip to Tau Ceti would take roughly the same amount of time as the Alpha Centauri voyage - at least for the crew.  Relativistic effects starting to kick in with longer acceleration.

Offline dustinthewind

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In regards to the death blast released when the ship stops due to collapse of the gravity well in front of the ship.  It was suggested a good idea it to make a pre-top before arriving.  So if anyone was using this then would we see what would appear to be a gamma ray burst?  I wonder if we could recognize it from other types of gamma ray bursts. 

I am guessing the gravity well in front of the ship pulls it along while the negative gravity well behind the ship pushes it.  I could imagine light trying to escape a gravity well getting red shifted and a light falling into a gravity well being blue shifted I suppose.  Making the gravity well disappear suddenly I suppose the particles or light no longer need to escape the gravity well and remain up-shifted (seems odd)?  I'm not sure why the ship itself wouldn't be blasted as the particles that had their potential energy converted to kinetic suddenly go every direction as the gravity well disappears but I suppose if so as previously stated there is shielding. 

So what kind of warp do they think they might be observing in the chamber?  Is it a positive gravity signature or a negative signature?  How would they replicate a negative gravity well?  Does it osculate between negative and positive?  Or is it just positive to null and positive space time waves? 

Maybe I would be correct in guessing there appears to be a shortening of distance for the laser which is similar to the heating lowering the density of air which is why they would worry about the air heating in the cavity.  I know as previously stated the cavity retains the heat so testing on, off, on, may eliminate the problem as the cavity remains hot.  Shortening of distance makes it look as though it is negative energy density I would guess.  But inside just a regular cylindrical cavity is what really baffles me.  If the field permeates and even effects the cavity could they detect the change in its atomic bonds?  Would they become more energetic and change the cavity characteristics?  Would it speed up a very accurate clock and could that be a test method?  Would the mass of the object change?

Offline Stormbringer

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Assuming gamma ray bursts can be associated with exit from warp then the magnitude should be considerably smaller than known cosmic sources but still pretty bright. They should appear at semi-regular intervals near stars (probably just outside any planetary system) and close to each other but not quite at the same locations. This variability should make ruling out natural sources fairly easy.

I suppose if one is given that the blue shifted accumulated photon thing is real then you could calculate the amount of energy involved in a given warp traverse between star system A and star system B for a given mass of space ship. you could then determine if a gamma ray event would be detectable with current instruments and at what range. then you could watch likely stars within that range with the appropriate instrument.
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Offline CW

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Another question regarding a possible 'quantum wake', caused by the drive's operation:

In water for instance, we can observe longer lasting turbulences which are caused by propeller engines. I'm aware that the hypothesized MHD-like behavior of the QV is only roughly comparable to a fluid, but I'm still curious whether there would theoretically remain some sort of detectable QV 'space turbulences' when a QV-driven spaceship passes a location.
« Last Edit: 04/24/2015 07:33 AM by CW »
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Offline Stormbringer

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Partial success. I found a unfortunately trimmed edit of a presentation where he started to explain it. But the answer was truncated by the end of the clip.



starts at 53:46 seconds and ends before Dr White has finished his answer.  However it is probable that better clips of this presentation exist. I'll look for one tomorrow.



« Last Edit: 04/24/2015 08:34 AM by Stormbringer »
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