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#2400 by zen-in on 06 Nov, 2016 03:31
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No alas, we can't discuss in details the fact Eagleworks managed to dramatically reduce and quantize any spurious mundane cause of thrust, yet still measured a consistent force in a hard vacuum two orders of magnitude higher than a perfectly collimated photon rocket.
Admittedly, I haven't been following events very closely as of late, but... Wait!? What!?
EW was able to measure a force 2 orders of magnitude larger than a perfectly collimated photon rocket? When did this leak?
...
Irrespective of the credibility of these rumors comparing an anomalous force to the force of a photon rocket does not convince me of anything. Measurement errors never disappear. The best that can be done is to compare a measurement to the expected measurement error. If the experimenter doesn't know what the measurement error is then all their data is due to measurement error. -
#2401 by RotoSequence on 06 Nov, 2016 03:38
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No alas, we can't discuss in details the fact Eagleworks managed to dramatically reduce and quantize any spurious mundane cause of thrust, yet still measured a consistent force in a hard vacuum two orders of magnitude higher than a perfectly collimated photon rocket.
Admittedly, I haven't been following events very closely as of late, but... Wait!? What!?
EW was able to measure a force 2 orders of magnitude larger than a perfectly collimated photon rocket? When did this leak?
...
Irrespective of the credibility of these rumors comparing an anomalous force to the force of a photon rocket does not convince me of anything. Measurement errors never disappear. The best that can be done is to compare a measurement to the expected measurement error. If the experimenter doesn't know what the measurement error is then all their data is due to measurement error.
I can definitely understand this critique. 96 Micronewtons is basically nothing. -
#2402 by tchernik on 06 Nov, 2016 03:49
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I can definitely understand this critique. 96 Micronewtons is basically nothing.
Agree. But a nothing that could measurably change a satellite's trajectory in space in a potentially useful way.
This is why this potential phenomenon has such an eppur si muove feeling to it, and why it needs to be tested in space. -
#2403 by zen-in on 06 Nov, 2016 03:50
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Next Big Future picked up one of the papers posted here...
There is nothing new in the Next Big Future article. The thrust waveform (fig c) is from the first vacuum tests two years ago. The photo below is from those tests. If you compare the two graphs you will see they are the same data. Also the photos are from the first vacuum tests at Eagle Labs. We will have to wait for the publication of the peer reviewed paper.
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#2404 by DnA915 on 06 Nov, 2016 05:26
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So with the news of very good numbers in EW's upcoming paper, my mind goes more towards the application side of things. Although I realize the early applications if this works out in space will likely be orbital controls, I was curious about how well and how fast this would apply to human rated ships flying in the late 2020's and 2030's. SpaceX's Elon Musk has been on the record being very skeptical of the EM/Q-Thrust drive, and I think rightfully so. However, with greater scientific proof, I am very curious if there could be an early variant of the ITS system that is more efficient and takes advantage of the technology. Obviously, with the human carrying interplanetary spaceship, you would still require raptors, because no one is going to be doing EM drive propulsive landings anytime soon. However, my questions is, could you make a configuration with an orbital "Tow ship". This would basically just be a ship with a cluster of EM Drives on the back, and one or more nuclear reactors. These would wait in orbit, attach to a ship when its launched, tow it to mars (or other destinations), release the ship, and then stay in orbit until the return flight. It seems like this could lower the refuel count and greatly reduce travel time / radiation exposure assuming a significant N/kW drive. Obviously this is all hugely speculative, but I have my kicks somehow, right?
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#2405 by Bob Woods on 06 Nov, 2016 06:26
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#2406 by Gilbertdrive on 06 Nov, 2016 08:22
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No alas, we can't discuss in details the fact Eagleworks managed to dramatically reduce and quantize any spurious mundane cause of thrust, yet still measured a consistent force in a hard vacuum two orders of magnitude higher than a perfectly collimated photon rocket.
Admittedly, I haven't been following events very closely as of late, but... Wait!? What!?
EW was able to measure a force 2 orders of magnitude larger than a perfectly collimated photon rocket? When did this leak?
...
Irrespective of the credibility of these rumors comparing an anomalous force to the force of a photon rocket does not convince me of anything. Measurement errors never disappear. The best that can be done is to compare a measurement to the expected measurement error. If the experimenter doesn't know what the measurement error is then all their data is due to measurement error.
You are right. But the EW paper list and evaluate mesurement errors. The max possible errors are substracted to the results.
I hope I did not already told too much.
Also, The Traveller, I am sorry for your Cancer. My prayers are for you. -
#2407 by Gilbertdrive on 06 Nov, 2016 09:00
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So with the news of very good numbers in EW's upcoming paper, my mind goes more towards the application side of things. Although I realize the early applications if this works out in space will likely be orbital controls, I was curious about how well and how fast this would apply to human rated ships flying in the late 2020's and 2030's. SpaceX's Elon Musk has been on the record being very skeptical of the EM/Q-Thrust drive, and I think rightfully so. However, with greater scientific proof, I am very curious if there could be an early variant of the ITS system that is more efficient and takes advantage of the technology. Obviously, with the human carrying interplanetary spaceship, you would still require raptors, because no one is going to be doing EM drive propulsive landings anytime soon. However, my questions is, could you make a configuration with an orbital "Tow ship". This would basically just be a ship with a cluster of EM Drives on the back, and one or more nuclear reactors. These would wait in orbit, attach to a ship when its launched, tow it to mars (or other destinations), release the ship, and then stay in orbit until the return flight. It seems like this could lower the refuel count and greatly reduce travel time / radiation exposure assuming a significant N/kW drive. Obviously this is all hugely speculative, but I have my kicks somehow, right?
With the performance of the EW Emdrive, we can do a few calculus.
I shall suppose a huge solar array of 1 MW (instead of 200KW)
The thrust is 1.2mN/Kw. So, 1.2N/Mw
I shall suppose a mass of 100T.
I makes a Delta V per day of 1.2*86000/100000=1.032
So, it makes 1.032m/s of Delta V each day. It is not yet enough to get in a reasonable time to mars. A few km/s of total Delta V are needed. It would needs around 2 orders of magnitude higher thrust.
The actual 1.2mN/Kw would be OK only for orbital position keeping or modifying. With the possibility of saving satellites that were sent in the wrong orbits, or of directly launching more satellites in the same launch, some one in the wrong orbit, and sending them to the right orbit after a few mothes or years of continual acceleration. It could also be used to make small ships able to desorbit a big satellite in some years. So, there are already several possible utilities, but not yet for Mars mission. Or only as a secondary thruster for trajectory corrections. -
#2408 by meems on 06 Nov, 2016 09:35
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Quote from: rodal
>Cannot self-accelerate as a closed system with a force/powerInput orders of magnitude greater than a perfectly collimated photon rocket.
Shawyer asserts that due to relativistic effects, the system becomes open. Where is the argument against this? I didn't find it in all that stuff you linked to
Also, are you implying an absolutely closed system ( non relativistic and relativistic ) can propel itself with the force of a photon rocket? How?
Asymmetries are known to come from relativistic conditions, e.g. the twin effect. Is there a simple reason why time asymmetry is allowed, but force asymmetry isn't? -
#2409 by Gilbertdrive on 06 Nov, 2016 10:44
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Quote from: rodal
>Cannot self-accelerate as a closed system with a force/powerInput orders of magnitude greater than a perfectly collimated photon rocket.
Shawyer asserts that due to relativistic effects, the system becomes open. Where is the argument against this? I didn't find it in all that stuff you linked to
Also, are you implying an absolutely closed system ( non relativistic and relativistic ) can propel itself with the force of a photon rocket? How?
Asymmetries are known to come from relativistic conditions, e.g. the twin effect. Is there a simple reason why time asymmetry is allowed, but force asymmetry isn't?
Of course, a closed system can propel itself with the force of a photon rocket. Photons do have momentum, and CoM make than, with expelling a photon, you get momentum in the opposite direction.
In fact, the system constituted by the photon rocket and it's contained energy, if it is isolated, does not gain momentum, but since you do not count any more the photons expelled as being a part of your ship, the ship itself gain momentum. It is the sampe principle that this of any chemical rocket. If the system rocket+propellant is a closed system, it will never get momentum. But, as you don't count any more the propellant that you throw away (you don't need the propellant going on destination) the rocket gain momentum in the other side. If you have a 100kg ship and that you send, in forms of collimated photons, the massic energy of 1kg of matter, your ship get around a speed of C/100 (there is a relativistic correction needed to get the exact speed, but it is close)
The photons does not have much momentum. That is why a photon rocket is not much efficient. But, in fact, if you count the massic energy of the propellant, the photon rocket is the most efficient propulsion for a closed system.
If instead of sending 1 kg of propellant to 4000m/s with a classical rocket motor, you could get the massic energy of this 1kg, and send it as photons, you get far much Delta V.
Shawyer asserts that due to relativistic effects, the system becomes open.
That is this assert that has no proof. In Special Relativity (used by Shawyer) or in GR, there is no such possibility. Photons bouncing in a closed cavity, far enough from anything else so gravity becomes negligible, doesn't become an open system. There are theories where it becomes an open system, interacting with the rest of the universe, for example MiHsC. But not in Special Relativity or General Relativity. That is why we are creating mad theories here If GR was enough to explain a working Emdrive, we would stay on GR.
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#2410 by flux_capacitor on 06 Nov, 2016 11:28
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Next Big Future picked up one of the papers posted here...
There is nothing new in the Next Big Future article.
I am sorry but NBF has the paper (first link in their article). -
#2411 by Monomorphic on 06 Nov, 2016 11:45
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First, that so-called "PLA conductive graphene based filament" has an electrical resistivity of 8 mΩ·m at ambient temperature. In comparison, copper has an electrical resistivity of less than 17 nΩ·m. This makes that graphene-based PLA look over 470,000 times more insulating.
The reason I would use graphene based PLA is because it can be electroplated without the need to apply a conductive coat.Then, isn't polylactic acid very soft and prone to deformation even under relatively low mechanical and thermal stresses?
Perhaps not as prone to deformation if it has a 0.5mm layer of copper or silver electroplated over it.Doesn't additive manufacturing process, i.e. 3D-printing, especially melted plastic based, produce stacked thin layers of different levels, giving a very rugged surface in the end?
Doesn't smoothing that rugged surface, by sanding or melting it with solvent vapor bath treatment, change the reflection angle of the surfaces and the distance in-between?
3d-printing would produce stacked thin layers that will be rugged (depending on the quality of the printer). If you look closely at the hackaday baby emdrive cavity, you will see these layers clearly on the interior surface.
As for sanding changing the reflection angle of the cavity, I think some of that can be compensated for in the 3d model. It may also work out that 0.5mm of sanding is replaced by 0.5mm of electroplate.
I would need to experiment, but a highly polished finish is possible: http://www.repliforminc.com/finishes.html
Even if it doesn't work out the way I have described above, a great way to machine a cavity from solid metal would be the lost wax method. And since wax filament is available for 3d printers I could easily pivot that direction. -
#2412 by rfmwguy on 06 Nov, 2016 12:51
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If I translate my best test result of 18.4 mN @ ~750W ERP (after losses/reflection), I would have ~13.8 mN/kW.
Coincidence is (IIRC) EW is at 1/10 my power and 1/10 my mN/kW.
I am not sure this means anything, as both were at different freqs using different construction materials etc., just a number that jumped out at me.
Regardless, I am not 100% convinced the leaked paper will be the one published. It was my guess that there were delays due to re-write requests. How can we be sure this was the Final Draft? Best we wait for December before diving too deeply into things. -
#2413 by Star One on 06 Nov, 2016 13:58
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Well, the click-bait sites are already starting to pick up the paper this morning. I'm waiting for the "NASA Accidentally Invents Warp Drive" headlines to start rolling again.
Just one more reason to be careful what we say here folks, it's not just the active participants following this thread.
Still, this may be a "Great Filter" moment that humanity is successfully passing through...
I feared this would happen as soon as I saw Chris's message about having to remove certain postings. Luckily I missed the actual posts as I would rather wait for the official release. It's also been purged from the Reddit on EM drive. -
#2414 by flux_capacitor on 06 Nov, 2016 13:59
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Yes there are forces on the side walls.
Yes the acceleration direction is opposite to that of the Thrust force generated on a scale.
Roger reported on this and measured it in his Demonstrator Static tests as attached which had a measured vector Small to Big. He also commented in his various papers that when the Demonstrator EmDrive was placed on the rotary test rig, it accelerated Big to Small.
TheTraveller, can you please tell if you consider Eagleworks' torsion pendulum as a "static" (like a frustum fixed on a spring balance on a digital scale) or "dynamic" (like a frustum free to accelerate on a rotary test rig) experimental test setup (I'm employing Shawyer's terminology)? -
#2415 by Star One on 06 Nov, 2016 14:09
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Yes there are forces on the side walls.
Yes the acceleration direction is opposite to that of the Thrust force generated on a scale.
Roger reported on this and measured it in his Demonstrator Static tests as attached which had a measured vector Small to Big. He also commented in his various papers that when the Demonstrator EmDrive was placed on the rotary test rig, it accelerated Big to Small.
TheTraveller, can you please tell if you consider Eagleworks' torsion pendulum as a "static" (like a frustum fixed on a spring balance on a digital scale) or "dynamic" (like a frustum free to accelerate on a rotary test rig) experimental test setup (I'm employing Shawyer's terminology)?
I don't think you'll get a reply from them for obvious reasons. -
#2416 by WarpTech on 06 Nov, 2016 15:06
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That is this assert that has no proof. In Special Relativity (used by Shawyer) or in GR, there is no such possibility. Photons bouncing in a closed cavity, far enough from anything else so gravity becomes negligible, doesn't become an open system. There are theories where it becomes an open system, interacting with the rest of the universe, for example MiHsC. But not in Special Relativity or General Relativity. That is why we are creating mad theories here If GR was enough to explain a working Emdrive, we would stay on GR.
I did stay with GR. I just interpret it differently than anyone else. Everybody want's to know what the EmDrive is pushing against, "interacting with the rest of the universe", etc... In my model, the "empty" metal frustum cavity is pushing against the EM energy stored inside it. The weight of the stored EM energy is the Counter Mass against the weight of the metal frustum. The "weights" are wrt the internal acceleration vector, generated by the asymmetrical power dissipation. (The gradient.)
Now, if the walls were perfect conductors, the Q were infinite and the energy inside the frustum had no way out, then this could never work. But... if the MW source is turned off, the energy does NOT stay bottled up in there forever. It dissipates. It gets out through dissipation as heat, the ultimate "red shift" and other dissipative processes. It is a very slow process, but a slow exhaust velocity is what we want, in order to get thrust greater than a photon rocket.
The size of the counter mass is directly proportional to P*Q, and inversely proportional to frequency, f for a given input power. In other words, P*Q/f = Energy and we want more energy stored. The EmDrive only needs a small gradient in the dissipation factor, but it needs to store an enormous counter mass as EM energy to get higher thrust.
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#2417 by Bob012345 on 06 Nov, 2016 15:16
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Here's a simple idea, can anyone refute it?
A standing wave in a tapered waveguide cavity might press on the waveguide asymmetrically, hence net force.
Right?
This is very thoroughly trodden ground in these threads. Shawyer says yes, while most everyone else says no.
Actually it is even worse than that, since Shawyer claims:
1- there is no sidewall force,
2- the force exerted by radiation pressure onto big end is greater than onto small end; and this resulting backward force, vector direction pointing small to big (that he calls the "thrust" force) is measurable with "static" (i.e. non free to move frustum) measurement apparatus like torsion pendulums and digital scales,
3- but the force moving the EmDrive forward (that he calls the "reaction" force") accelerates the frustum small end leading, when it is on a "dynamic" (i.e. free to move) measurement apparatus, like low-friction linear or rotary test rigs (or driving an hypothetical flying or space vehicle).
From a scientific point of view, point (1) is simply wrong, and the relation between points (2) and (3) is incomprehensible word salad as it seems like "pushing on an object to the right moves it to the left" since the pressure is purely internal and the EmDrive doesn't expel anything out of its back as a conventional rocket would do.
EDIT: A recent (yesterday) video of Roger Shawyer explaining those different directions and the different behaviour of those "two forces":
http://www.ibtimes.co.uk/videos/embed/21436
By the way it is the first time Shawyer brings up the idea that the EmDrive could also solve the energy crisis and global warming, as a new way to produce clean electrical energy. Coincidentally(?) the possibility that the EmDrive could act as an electric generator is a question that has been raised by Fan Boi and briefly discussed here on NSF a few weeks ago.
When he speaks of solving the energy crisis I believe he is not discussing the EmDrive as a new source of energy, he is discussing using the EmDrive to economically build large solar power satellites in GEO and harvesting the sun. -
#2418 by Rodal on 06 Nov, 2016 15:26
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Look deeper into all the messages from memerbs I linked to (also look into the posts by wicoe, Gilbertdrive and Frobnicat), and consider conservation principles.Quote from: rodal>Cannot self-accelerate as a closed system with a force/powerInput orders of magnitude greater than a perfectly collimated photon rocket.
Shawyer asserts that due to relativistic effects, the system becomes open. Where is the argument against this? I didn't find it in all that stuff you linked to
......Also, are you implying an absolutely closed system ( non relativistic and relativistic ) can propel itself with the force of a photon rocket? How?..
No, on the contrary, I never implied that. In this forum, when quoting, please always link to the original member's post. Quote as follows, using the quote button on the upper right (notice that this allows a reader to directly link to the quoted post by clicking on the quote, giving the time of the post]...Cannot self-accelerate as a closed system with a force/powerInput orders of magnitude greater than a perfectly collimated photon rocket. Need an external field so that it is not a closed system. Cannot be explained solely on the basis of Special Relativity and Maxwell's equations as a closed system.
the bolded statements are important qualifier statements that you did not include in your fragmented quote.
On the contrary, I implied that an electromagnetic resonant cavity, even if open, would have an upper limit self-acceleration at most equal to a perfectly collimated photon rocket, under Special Relativity and without coupling external fields. Furthermore, a closed cavity would have a self-acceleration much smaller than a perfectly collimated photon rocket (due to asymmetric thermal radiation in Space), under the same constraints.
In order to have a force/inputPower greater than a perfectly collimated photon rocket one must exhaust (or couple to) massive particles rather than photons.
==> There is a paper by a Professor from Finland ( http://www.ibtimes.co.uk/emdrive-finnish-physicist-says-controversial-space-propulsion-device-does-have-exhaust-1565673
http://scitation.aip.org/content/aip/journal/adva/6/6/10.1063/1.4953807
) that claims that a perfectly closed electromagnetic cavity can still materialize photons outside it, and I also wanted to make it clear that his theory (even if true, which I question) still would not explain the EM Drive...Asymmetries are known to come from relativistic conditions, e.g. the twin effect. Is there a simple reason why time asymmetry is allowed, but force asymmetry isn't?
Yes, the simple reason is that a force asymmetry is constrained by two conservation principles under Special Relativity:
Conservation of Momentum
Conservation of Energy
the twin paradox under Special Relativity does not violate conservation of energy or conservation of momentum
Things are allowed unless they violate conservation principles, they violate the equations of motion, they violate boundary conditions, they violate initial conditions, etc. etc.
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#2419 by wicoe on 06 Nov, 2016 15:40
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Quote from: rodal
>Cannot self-accelerate as a closed system with a force/powerInput orders of magnitude greater than a perfectly collimated photon rocket.
Shawyer asserts that due to relativistic effects, the system becomes open. Where is the argument against this? I didn't find it in all that stuff you linked to
Also, are you implying an absolutely closed system ( non relativistic and relativistic ) can propel itself with the force of a photon rocket? How?
If the system is open, it has to interact with some external (i.e. existing outside the frustum) fields or objects. One cannot just state it's open without specifying what it's interacting with.
