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#2060 by aero on 12 Oct, 2014 23:05
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Quote
Dimensional analysis (sanity check) :
(1) kg m /s² = kg m² /s^3 s /m OK (Q dimensionless)
(2) kg m /s² != kg m² /s^3 m² s /m² /m² = kg /s² the expression lacks a meter unit somewhere
Yes. By replacing length by area, I introduced an extra "meter." Then I multiplied top and bottom by a*b and factored. That divides out the m^2 so I lost both "meters". I guess that's another reason why a formal 2-D derivation is needed. -
#2061 by Notsosureofit on 13 Oct, 2014 00:59
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From my knowledge, the formula from Prof. McCulloch's and the formula from Shawyer remain the only formulas that come close to predicting the experimental thrusts in the USA, UK and China experiments. Everything else is orders of magnitude off.
http://www.libertariannews.org/wp-content/uploads/2014/07/AnomalousThrustProductionFromanRFTestDevice-BradyEtAl.pdf
The paper says clearly and provides data that the dielectric is key. The question is how.
Now on the flipside, with no dielectric present, you would get uneven heat of the cavity from fore to aft and some movement of the device. How else could it move? Internal stresses would convert to wall strain. Where is the reaction mass?
With @notsosureofit finding that the dielectric was PE, 1 inch thick, the chirality theory is back into consideration due to polyethylene being able to have spherulites melt-crystallised. (I still have reservations about the amount of chirality in commonly available samples)
http://www.esrf.eu/UsersAndScience/Publications/Highlights/2011/scm/scm4
Now if I remember right, them capacitors were bolted into stacks (stack?) for an early accelerator in the Cambridge (MA) area, and when I saw them they showed me holes in the ceiling where the bolts had been blown up thru. I don't remember if it was on charge or discharge but there was significant force involved. (I used oil caps) -
#2062 by Mulletron on 13 Oct, 2014 07:29
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"Regardless of the mechanisms that might be entertained with regard to
"propellantless" or "field" propulsion of a spaceship, there exist certain constraints that
can be easily overlooked but must be taken into consideration. A central one is that,
because of the law of conservation of momentum, the center of mass-energy (CM) of an
initially stationary isolated system cannot change its position if not acted upon by outside
forces. This means that propellantless or field propulsion, whatever form it takes, is
constrained to involve coupling to the external universe in such a way that the
displacement of the CM of the spaceship is matched by a counteracting effect in the
universe to which it is coupled, so as not to violate the global CM constraint. Therefore,
before one launches into a detailed investigation of a proposed propulsion mechanism it
is instructive to apply this principle as an overall constraint to determine whether the
principle is violated." You have to thrust against something.
I really need you guys to take the above statement seriously. We also must not forget about hidden momentum. We need to make sure we are doing real science here.
http://gr.physics.ncsu.edu/files/babson_ajp_77_826_09.pdf
We, collectively as a group, need to make sure we are wearing our scientist, mathematician, and engineer hats equally. Each of us have more or less of these skills. Otherwise the cake is a lie.
Engineers understand that in any closed system, the way energy is conserved is by converting that energy to another form or by doing work. There has to be a path for that work to happen.
The potential energy of a hairspray can doesn't make it shoot across the room, even if you heat it up on one end. You have to expel that potential energy out the nozzle to convert it to kinetic energy.
Otherwise, the potential energy of the system remains isolated within the closed system. There has to be a path for this to happen.
In closing, there are only 3 way for emdrive to thrust with just a flooded rf cavity alone.
1. Leaking heat to the rest of the universe. (Shawyer)
2. Leaking magnetic influence to the rest of the universe.(like a space tether) (Shawyer)
3. In the absence of ALL other forces (like in a sweet spot between galaxies) tiny motion because of modified inertia.
You have to find a way to thrust against something else. That is the holy grail. -
#2063 by IslandPlaya on 13 Oct, 2014 08:13
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No.
We do not know what happens.
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#2064 by Mulletron on 13 Oct, 2014 08:45
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For you guys who like to tinker, here's pointers on how to build your own torsion balance at home:
https://www.fourmilab.ch/gravitation/foobar/
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#2065 by JohnFornaro on 13 Oct, 2014 12:20
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Fine: Go ahead and make me learn something new every day. See if I care. Hope y'all are happy now.
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#2066 by JohnFornaro on 13 Oct, 2014 12:34
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This means that propellantless or field propulsion, whatever form it takes, is
constrained to involve coupling to the external universe in such a way that the
displacement of the CM of the spaceship is matched by a counteracting effect in the
universe to which it is coupled, so as not to violate the global CM constraint.
Ipso fatso, any copper clad "new universes" are not all that new. There's some fan clubbing going on in this thread, and so IMO, language should be a bit more carefully considered; "otherwise the cake is a lie".
Put another way, propellantless propulsion is not as easy as falling off a piece of cake. -
#2067 by Mulletron on 13 Oct, 2014 12:50
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This means that propellantless or field propulsion, whatever form it takes, is
constrained to involve coupling to the external universe in such a way that the
displacement of the CM of the spaceship is matched by a counteracting effect in the
universe to which it is coupled, so as not to violate the global CM constraint.
Ipso fatso, any copper clad "new universes" are not all that new. There's some fan clubbing going on in this thread, and so IMO, language should be a bit more carefully considered; "otherwise the cake is a lie".
Put another way, propellantless propulsion is not as easy as falling off a piece of cake.
IF the science gets done, you get a neat thruster (cake), for the people who are still alive after us. IF, otherwise the cake is a lie. -
#2068 by JohnFornaro on 13 Oct, 2014 13:17
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Excellent song! Mucho thankso!
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#2069 by Stormbringer on 13 Oct, 2014 13:53
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you should have used a vocaloid cover of that song. a robot singing a robot's song
portal II End Credit Song:
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#2070 by Rodal on 13 Oct, 2014 15:19
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The "self accelerating box paradox" due to Unruh radiation, has a rich history going back to this original publication by Unruh himself in 1982:
William G. Unruh and Robert M. Wald, Acceleration radiation and the generalized second law of thermodynamics,Phys. Rev. D 25, 942 – Published 15 February 1982
http://journals.aps.org/prd/abstract/10.1103/PhysRevD.25.942
_____________________________
This is a popular account, included here with special regard and affection towards kernosabe and his clamor of "non capisco". It is written by popular science writer Paul Davies, as it appeared in New Scientist Jan 14, 1982 (please notice that I went through the trouble and time to shorten the url, so as not to screw up the formatting in this thread ) :
http://goo.gl/w7N6ir
_____________________________
For objective balance, this is a more recent paper on the "self accelerating box paradox," with a different take than Unruh and Wald's paper regarding the thermodynamics issue:
Donald Marolf, Rafael Sorkin, Perfect mirrors and the self-accelerating box paradox, Phys.Rev. D66 (2002) 104004
http://arxiv.org/abs/hep-th/0201255
__________________________
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#2071 by Mulletron on 13 Oct, 2014 15:26
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Ah yes, the Semmelweis Reflex.
Let me know when you see a tin can move all by itself here on Earth. Or the galaxy.
You're basically saying that I could go up to one of my satellite antennas right now and weld the feedhorn shut on it and have a new form of propulsion.
It is as simple as this. The casimir effect of a copper can is basically zero. It will only accelerate all by itself if there is no other force acting on it. Like between galaxy clusters if you're lucky. Wrap it in new fangled meta materials; you know, the ones that make things appear invisible, then you can have your paradox box. Maybe. Even then you will have to strap a fan on it or do something to provide thrust in order to overcome gravity.
That isn't what was in the test chamber.
I clearly mentioned in the summary how it could move all by itself by virtue of its shape, IN DEEP SPACE.
Perspective is everything.
Put MiHsC in the proper context.
As John so eloquently put it, "Ipso fatso, any copper clad "new universes" are not all that new."
Love you guys
Lastly, Shawyer's latest theory paper, says all throughout that it has dielectric at the small end.
http://emdrive.com/theorypaper9-4.pdf
Page 6. "dielectric-filled section at the smaller end of the taper"
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#2072 by Rodal on 13 Oct, 2014 16:35
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Again (http://forum.nasaspaceflight.com/index.php?topic=29276.msg1269787#msg1269787), acceleration due to a change of inertia follows from the basic principle of conservation of momentum. There is no basic principle that for something to move "thrust must be involved" in Physics. Physics has conservation laws. Conservation of momentum is one of the basic laws of Physics, obeyed in General Relativity as well as in Quantum Mechanics. As we know from Physics and Engineering the relevant consideration is how such an acceleration (and resulting force) may compare with other accelerations (and forces) to produce a net acceleration (or force).
Scientific criticism may address thermodynamic considerations, information theory, and the arrow of time, for example, but never "thrust must be involved for something to move", there is no such principle in physics.
The language of physics is conservation laws, virtual work principles and mathematical equations and not words/and/or/music like "the cake is a lie" or "you." -
#2073 by aero on 13 Oct, 2014 16:52
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Someone once famously said. "For every action their is an equal and opposite reaction."
We know what the reaction was, (the measured thrust force), we're trying to figure out what the action was. We are going about it by eliminating everything that the action was not. Once all other candidate actions are eliminated, the remaining candidate must be true no matter how improbable. -
#2074 by Mulletron on 13 Oct, 2014 16:53
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Again (http://forum.nasaspaceflight.com/index.php?topic=29276.msg1269787#msg1269787), acceleration due to a change of inertia follows from the basic principle of conservation of momentum. There is no basic principle that for something to move "thrust must be involved" in Physics. Physics has conservation laws. Conservation of momentum is one of the basic laws of Physics, obeyed in General Relativity as well as in Quantum Mechanics. As we know from Physics and Engineering the relevant consideration is how such an acceleration (and resulting force) may compare with other accelerations (and forces) to produce a net acceleration (or force).
Scientific criticism may address thermodynamic considerations, information theory, and the arrow of time, for example, but never "thrust must be involved for something to move", there is no such principle in physics.
The language of physics is conservation laws, virtual work principles and mathematical equations and not words/and/or/music like "the cake is a lie."Quote"There is no basic principle that for something to move "thrust must be involved" in Physics."
Except Newton's laws of motion........
Without a means to thrust. It is moving due to entropy. Because it is not a perfectly isolated system. It is radiating heat.
The way you describe it, violates mechanics.
Translation, not new science.
Regardless of the internal stresses an object is experiencing, it must still experience a force in order to change acceleration.
The Hubble scale Casimir effect on the inertial bias of a copper can here on Earth is essentially zero.
One can choose to ignore the laws of motion and the laws of thermodynamics if they wish. The laws are only suggestions...........
If one does, I can offer them no hope.
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#2075 by Rodal on 13 Oct, 2014 16:59
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Wish us would address science and engineering without using words like "you" and "I".
The personalization of what should be scientific and engineering arguments is the reason why academics stay away from internet forums. Such personalization degrades the search for truth. There is no "you" and "I" in mathematical formulas or in Physics. -
#2076 by ThinkerX on 13 Oct, 2014 23:39
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We have covered quite a few concepts in this thread. One or two looked almost promising for a time, yet...
Doctor White and the other researchers involved have been looking into propellentless drives of one sort or another for decades. Towards the end of the paper that tripped off this thread, the Eagleworks team stated they were working on a dramatically improved version of this propellentless drive, one capable of a thrust of 0.1 Newton's in a vacuum.
Everything we have looked at here falls at least somewhat short of even the far more modest results from the current Eagleworks mechanism.
So, assume this next Eagleworks mechanism performs as advertised, or close enough to it - 0.1 Newton's of thrust, in a vacuum, with the error sources accounted for. Does this mean the 'unworkable' theory the Eagleworks team is using is correct? Or is there some way the idea's considered here could be scaled up and/or combined to account for this? -
#2077 by RotoSequence on 13 Oct, 2014 23:59
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At this stage of the game, I think we're all hungering for that "Eureka!" moment that will turn the (dime a dozen) ideas of non-propellant propulsion into a practical matter of engineering. Until such a demonstrably functional device can be built, EM drives will remain a pipe-dream. There's good effort being spent here on mathematics and juggling theories, but for now, it's all sizzle. I don't know about you, but I could really go for some steak.
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#2078 by Rodal on 14 Oct, 2014 00:30
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MiHsC prediction (http://physicsfromtheedge.blogspot.it/2014/10/mihsc-vs-emdrive-data-1.html )
-no fudge factors
-no free parameters
-a bare minimum of input data
-minimum idealization of actual geometry (actual EMDrive is not exactly a truncated cone)
Predicted Force =(P*Q/f)*((1/Dsmall)-(1/Dbig))
where:
P=power input
f=frequency
Q = quality factor (http://en.wikipedia.org/wiki/Q_factor)
Dbig = Diameter of larger flat surface of truncated cone EM Drive (the base of the truncated cone)
Dsmall = Diameter of smaller flat surface of truncated cone EM Drive (the smaller plane parallel to the base)
Experiment Dbig Dsmall Q Power in Freq' Prediction Observed
cm cm Watts GHz milliNewton milliNewton
-------------------------------------------------------------------------------------------------------------
Shawyer (2008) a 16 8 5900 850 2.45 12.8 16
Shawyer (2008) b 28 4 45000 1000 2.45 394 80-214
Juan (2012) TE011 16/28 8/4 32000 1000 2.5 80-274 214
Juan (2012) TE012 16/28 8/4 50000 1000 2.45 128-437 315
Brady et al. (2014) a 24.75 16.5 7320 16.9 1.933 0.129 0.0912
Brady et al. (2014) c " " 22000 2.6 1.88 0.061 0.0554
The following experiment is very anomalous:
Brady et al. (2014) b " " 18100 16.7 1.937 0.315 0.0501
because:
1) An increase in Q from Brady et al. (2014) a, from Q=7320 to Q=18100 (a factor 2.5 times) results in a smaller experimentally measured force (practically 50% of the force with the much lower Q)
2) An increase in Power Input from Brady et al. (2014) c, from 2.6 Watts to 16.7 Watts (a factor 6 times) results in a smaller experimentally measured force (10% smaller)
3) It was conducted at a frequency only 0.3% different than Brady et al. (2014) a
The prediction vs. observed experimental values is over a range of power of ~400 times and a range of force of ~6000 times (from 0.0000554 Newtons to 0.315 Newtons)
Links:
Shawyer, R., 2008. Microwave propulsion - progress in the emdrive programme
Yang Juan,Yang Le,Zhu Yu,Ma Nan, Journal of Northwestern Polytechnical University Vol 28 No 6 Dec 2010
Brady, D., et al., 2014. Anomalous thrust production from an RF test device measured on a low-thrust torsion pendulum. Conference proceedings, see Table page 18.
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#2079 by JohnFornaro on 14 Oct, 2014 01:26
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As John so eloquently put it, "Ipso fatso... "
Love you guys!
Hey! We should all get together over marshmallows and a campfire and sing a couple of rounds of "Kumbayaaaa".
But seriously, this has been one of the most enjoyable and learning intensive threads I've been in over the last four or five years.
Still, I don't think that there's a there there, in the sense of a pragmatically adaptable propulsion effect. The forces mentioned all seem so small, and rely on the most obscure of references to known physics.
Which is not all that many words, but still, is only a buncha words:The language of physics is conservation laws, virtual work principles and mathematical equations and not words/and/or/music like "the cake is a lie" or "you."
While it is true that "you" and "I" have little known effect on the pre-existing and yet to be discovered laws of physics, it is also true that only you and I can discuss these things. Fo zample:
I don't think this "skin effect" at the wall of the copper frustrum amounts to much of anything of any utility.
Assume an asymmetric resonant cavity, with microwave photons bouncing around inside it. They carry a force F=2P/c, where P is power and c is the speed of light, due to the inertial mass of light (light does have an inertial mass, or Solar sails wouldn't work). Including the Q factor (number of photon 'bounces') gives F=2PQ/c.
So F=2P/c and F=2PQ/c. with Q being the number of photon bounces. OK. There's a linear relationship between the force you get and the number of photon bounces, presumably related to the power you feed the device. But remember that the Mass (m) of those photons is pretty darn small.
Solar sails do work, but not at the scale and mass of the copper frustrum. Solar sails are football fields in size and don't weigh hardly anything. Like, 13,000 square feet and 70 pounds
So I'm struggling with the pragmatic utility of the setup. If an anomalous thrust is developed based on these masses, it ain't gonna be all that much. I haven't gotten to considering the Unruh waves yet, but, speaking of words, I'm choking on this:
"What if the resonant cavity walls acted like a Hubble horizon, especially for Unruh waves of a similar length..." Why izzat different from asking, what if pigs had wings?
If one does, I can offer them no hope.