-
#1000 by Monomorphic on 26 Sep, 2016 14:00
-
A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
-
#1001 by Flyby on 26 Sep, 2016 14:41
-
A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
However, I'm worried about the temperatures as most of the 3dprinting plastics loose their structural strength very fast...
I've reading very good reports on Ultem9085 printing as it keeps it strength up to much higher temperatures, but it is rather expensive stuff...
-
#1002 by Rodal on 26 Sep, 2016 14:49
-
A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with any unreinforced thermoplastic polymer, (including polyetherimide "Ultem tradename"), will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
Unreinforced thermoplastic polymers have much less thermal conductivity than metals
Material Thermal conductivity (W/mK) at room temperature (25 C)
ABS 0.14 to 0.21 (depending on formulation)
Ultem 0.12 to 0.22 (depending on formulation)
Copper 401.
Silver 429.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver., as well as their high thermal expansion. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity and low thermal expansion.
Unreinforced thermoplastic polymers are much less stiff than metals
Material Modulus of elasticity (GPa) at room temperature (25 C)
ABS 2.0 to 2.6 (depending on formulation)
Ultem 1000 3.45
Ultem 9085 2.2
Copper 117.
Silver 72
Unreinforced thermoplastic polymers have greater thermal expansion than metals
Material Coefficient of thermal expansion (10^-6 /°C) at room temperature (25 C)
ABS 70 to 150 (depending on ABS formulation)
Ultem 1000 65
Ultem 9085 65
Copper 17
Silver 20 -
#1003 by Monomorphic on 26 Sep, 2016 15:09
-
A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
-
#1004 by Gilbertdrive on 26 Sep, 2016 15:12
-
There are as far as I know 2 rotary EmDrive test rigs that have measured continual acceleration.
Roger's rotary test rig was built in 2006 and used an EmDrive that could deliver +200mN of thrust. Roger has recently released his very detailed enginerring report on both the Experimental & Demonstrator EmDrives, including detailed static thrust data.
He has told me that extensive experimental data was recorded from the rotary test rig using the Demonstrator EmDrive. Further that data showed both CofM and CofE were conserved. As with the static test data report, I expect the rotary test report will also be released.
Both test reports are available on www.emdrive.com
Unlike your assertion that there is no problem with the fact that a ship get a constant thrust superior to photon rocket, for constant imput power, Shawyer has clearly indicated that the thrust was decreasing as the Kinetic Energy increased. The reference is the departure speed. Of course, there is a big problem in the choice of this referential, but I shall focalize now on Shawyer's claims. I shall admit it. The reference for zero speed is so the referential of departure.
I join to my message several pages of a Theory Paper published by Shawyer.
If the engine is mounted in a spacecraft of total mass M and is allowed to accelerate from an initial velocity Vi to a final velocity Vf in time Delta t, then by equating Kinetic Energy we obtain… (see the paper)
The Fig 3.1 clearly shows that Q decrease when the speed increase. IT is approximately inversely proportional as I wrote in many messages. With a nuance around zero speed, that I did not mention in previous analysis because it was about high speeds. The inverse relation between speed and thrust can no be true around zero, else there would be an infinite thrust at zero speed ! But that is not a real problem. It would be the same for an electric car. If it is blocked, the force mesured is not infinite. For an electric car at constant power, the thrust decrease inversely to the speed, but it is also not true avec very very low speed. In fact, at low speeds, most of poser is wasted. As for the emdrive. The worst is at zero speed, all of the power of the emdrive is wasted (no Kinetic energy gained)
The figure 3.1 shows the quotient Q/Qu. So it is not significative at very low speeds, but we can see that for 1km/s we have a ratio of around 3. For 2km/s we have around 1,5. For 4km/s we have around 0,75 etc. That means that this document agrees with the fact that the thrust decrease as the speed increase.
Also, see the Fig 3.2 It shows the thrust in function of Q, for a speed of 3 km/s
As you can see, it tends to a certain value. When Q increase, the thrust is not increasing indefinitely.
In fact, when Q increase enough, near all the energy is transferred into Kinetic Energy. That is why there is an asymptote.
I made the calculus. I note F the force of the emdrive (the thrust) and V the speed in meters per second. I note W(1s) the work of the force F during one second
We have W(1s)=F*V
It makes F=W(1s)/V
The speed is 3km/s, and I shall take a work W of 1 KJ (1000 Joules)
So, it gives us F=1000/3000=0,333 N/Kw. It makes, 333 mN/Kw
333 mN/kw correspond perfectly to the asymptote on Fig 3.2 !
So, it is perfectly consistent. In this Shawyer paper, after a certain point, the thrust is inversely proportional to the speed that has been gained since the departure. The faster the ship is, the lower Q. If Q at zero speed is enormous, than almost all the energy is converted into Kinetic Energy. But there is no overunity.
So, Shawyer took into account the problem of Kinetic Energy.
If the ship had a power cord attached to the earth, all would be perfectly justified
and CoE verified.
But, in his IAC14 paper he forget that Thrust has to decrease with speed relatively with the departure point.
http://www.emdrive.com/IAC14publishedpaper.pdf
He made the calculus of efficiency, he found an efficiency of 0,31%. In fact Shawyer assumes that the final Kinetic Energy of the system is 1,87*10^20 joules. because he uses the non relativist formula E=1/2*mV² I found around 3.1191599*10^20 because I took 10 tons for the mass of the ship, and because at 0,67C, relativistic formula is really needed to be accurate.
But, as Shawyer calculates the imput power of the emdrive, he founds an enormous 6,04*10^20 Joules, he is happy and he considers that CoE is verified.
That is where the important point here. Shawyer admit that the Kinetic Energy in the Earth referential can not be superior to the energy spent by the ship. He just forgot to take into account his own theory in his thrust formula, and than, he made a mistake in calculating the imput power. (I calculated 6.311*10^13 Joules for 10 years of operation of the 200KwE generator, not taking into account the fact that the time goes more slowly for the ship.
Since the 2 errors compensate, and he find that no energy was gained, he his happy
Now, I shall try to read more his paper, and understand what mistake make him found that his 200 KwE power plant gives him so much Energy... That is more than the energy used by humanity in a year....
-
#1005 by VAXHeadroom on 26 Sep, 2016 16:08
-
A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
Another option using 3D printed plastic is to use the plastic as a 'lost wax' master and cast copper into a near-net-shape which can then be cut down and polished by a CNC milling process. Would save $$$ on machining time and up-front material cost.
-
#1006 by Bob012345 on 26 Sep, 2016 16:11
-
Gilbertdrive writes;Quote
But, as Shawyer calculates the imput power of the emdrive, he founds an enormous 6,04*10^20 Joules, he is happy and he considers that CoE is verified.
That is where the important point here. Shawyer admit that the Kinetic Energy in the Earth referential can not be superior to the energy spent by the ship. He just forgot to take into account his own theory in his thrust formula, and than, he made a mistake in calculating the imput power. (I calculated 6.311*10^13 Joules for 10 years of operation of the 200KwE generator, not taking into account the fact that the time goes more slowly for the ship.
No, I don't think he forgot anything. If he did then the reviewers did too which is unlikely. Shawyer's reduction in thrust as I understand it, is due to the cavity not supporting the acceleration, not actual speeds but regardless, his energy calculation for his probe allows continuous acceleration reduced by relativistic effects.
-
#1007 by Flyby on 26 Sep, 2016 16:17
-
ha, I see dr Rodal already quantified my concerns..
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
With my 9 years of 3dprinting experience I can advise only 3 types of 3dprinting I'd consider reasonably safe :
a) Lost wax 3dprinting
As the name indicates, it involves a secondary process of metal melting and needs a metal foundry set up.
Such a casted piece would need additional machining to obtain a high reflective surface.
b) metal powder laser sintering
As far I know, only titanium and stainless steel powder sintering are commercially available.
There some experimental one_of_a_kind copper printers out there, but they work with binders and need high temperature curing, which cause disproportional dimensional shrinking.
Same problem for the surface : it would need additional machining as a sintered surface is very coarse and granular.
c) ceramic powder printing
These prints also need high temperature curing, resulting in dimensional shrinking. and they'll need glasing and then additional copper plating.
This would be my personal choice, as I own a powder printer (Zcorp510) that can be easily converted to 3Dprinting ceramics. the dimensional problem could be solved by making tests and see how much it shrinks, and then design to compensate for the shrinking
There is no easy, straightforward, cheap 3dprint solution at this moment that can handle the possible high temperatures and , let's be honest, harmful radiation.
I would NOT use any thermo-plastics for this.. really not safe...
added:
A relative new process is under development and it uses light curable ceramics (SLA 3dprinting). It too suffers a bit from dimensional shrinking. However, most of the SLA printers have a limited buildplatform...
Your frustum might not fit...
-
#1008 by OnlyMe on 26 Sep, 2016 16:19
-
A two piece construction is also possible. This also saves a little off the 3d printing cost if the seam is in the middle.
Mono,
Middle seam: ASA: $620, ABS: $500
Big End seam: ASA: $825, ABS: $660
there are some issues with ABS 3dprinting as ABS tends to warp a lot. (I own a small 3dprinting shop).
Personally, I have not used ASA yet, but from reports I'm reading it has a superior warping resistance and seems to handle extreme conditions better.
Just make sure it doesn't cool off to rapidly or you'll get "splitting"...
https://3dprintingindustry.com/news/testing-asa-3d-printing-filament-weather-resistant-alternative-abs-62785/
Acrylonitrile butadiene styrene (ABS) is a common thermoplastic polymer with very low glass transition temperature (approximately 105 °C (221 °F)).
In general, making the EM Drive walls with a thermoplastic polymer will present other problems, besides warping.
We all know about the thermal effects in the EM Drive by now. The thermal conductivity and the thermal diffusivity of these polymers is several orders of magnitude lower than that of copper. So even if you have an internal thin layer of copper or silver, the thermoplastic polymer will act as an insulator. It is better to have a solid wall of a material (like copper or silver) with high thermal conductivity and high thermal diffusivity.
The warping is a consequence of the low modulus of Elasticity of unreinforced thermoplastic polymers as compared to metals like copper and silver. NASA Eagleworks used FRP wich is a composite where glass-fibers reinforces a thermoset epoxy to provide a higher modulus of elasticity.
I'm also getting a quote for CNC milling. We will see what that comes to as it seems like the parts would need to be milled from large solid blocks of copper - which is extremely expensive - thousands of dollars each.
If I use ASA and print 1cm thick walls and then electroplate a thick copper coat of 3mm after etching, then polish down to 2mm, it should be rigid enough. Though I think the process of etching the ASA, and electroplating 3mm of copper would be a difficult undertaking as a DIY.
Another option using 3D printed plastic is to use the plastic as a 'lost wax' master and cast copper into a near-net-shape which can then be cut down and polished by a CNC milling process. Would save $$$ on machining time and up-front material cost.
If I understand you correctly, you would not need to start with a printed master. A lost wax master near enough the final dimensions needed could be fabricated from clay or ceramics at far less expense, then milled to the desired finished net-shape. Casting the copper to a close approximation before milling would save $$, compared to starting with a solid block. And if the end product were to be plated with a greater than skin depth silver, the purity of the cast copper may not even be as much of an issue. -
#1009 by tchernik on 26 Sep, 2016 16:21
-
Delineating competitive theories and hardware is critical for the readership imho especially for science media whom are following emdrive closely. "Closed" RF frustum cavities are the emdrive. Cannae is not and neither is Woodward's Mach effect nor nassikas. Trying to blur the lines seems disingenuous as these 8 threads have been emdrive from day 1.
Coe/com can apply anywhere and is a well discussed subtopic here. My vote has always been towards staying on topic rather than attempting to broaden an otherwise large topic. Emdrive is already a massive thread series, no need to boost it with Mach effect, nassikasn or cannae.
Like you, I'm just a part time poster here with my own point of view. Nsf staff can decide if renaming or broadening emdrive is the best thing to do.
Personal opinion: I would also like that the discussion remains focused and on topic. A big part of the success of this forum (because it is the most fruitful public Internet discussion I have ever seen) comes from the strong focus on experiments and proof of theories explaining the Emdrive.
I understand Mach effect/GR extension theories look like very likely candidates now for explaining this phenomenon, if further experiments confirm it exists, but the Emdrive is objectively a wholly different device in its form and outwardly visible mechanics in comparison with Prof. Woodward's own device; they were found/conceived in very different circumstances and both deserve independent analysis and experimentation.
Mostly because we don't really know if they really are manifestations of a same physical principle yet (this requires a lot more experimentation!) or how any or both of them will behave under new test conditions, including if they can scale from theoretically interesting to practically usable forces. Which let's remember, it's the reason this topic has found a place in this highly esteemed and reputable forum focused on space exploration, including propulsion topics. -
#1010 by Rodal on 26 Sep, 2016 16:30
-
....
Personal opinion: I would also like that the discussion remains focused and on topic. A big part of the success of this forum (because it is the most fruitful public Internet discussion I have ever seen) comes from the strong focus on experiments and proof of theories explaining the Emdrive.
I understand Mach effect/GR extension theories look like very likely candidates now for explaining this phenomenon, if further experiments confirm it exists, but the Emdrive is objectively a wholly different device in its form and outwardly visible mechanics in comparison with Prof. Woodward's own device; they were found/conceived in very different circumstances and both deserve independent analysis and experimentation.
Mostly because we don't really know if they really are manifestations of a same physical principle yet (this requires a lot more experimentation!) or how any or both of them will behave under new test conditions, including if they can scale from theoretically interesting to practically usable forces. Which let's remember, it's the reason this topic has found a place in this highly esteemed and reputable forum focused on space exploration, including propulsion topics.
1) Discussion of piezoelectric/electrostrictive stack experiments belong in the Woodward effect thread
2) All discussions of the EM Drive best belong in this thread, regardless of the theory being discussed. Therefore if there is a discussion of the EM Drive based on the Mach effect. it belong in this thread. This is the way it has been since thread #1. People that have been here since thread #1 may recall Paul March often repeated quote that according to him, "the Quantum Vacuum explanation and the Mach Effect explanations for the EM Drive are two sides of the same coin." Similarly, a discussion of the EM Drive as being due to the Quantum Vacuum, belongs in this thread, and not in a Quantum Vacuum thread. Similarly, a discussion of the EM Drive as being due to general relativity, belongs in this thread, and not in a general relativity thread. Ditto for any discussion of any other theoretical explanation for the EM Drive.
3) One possible question remaining would be whether a discussion about an experimenter's use of a piezoelectric stack inside an EM Drive belongs in this thread or the other. That is up for discussion, but I propose that it belongs in this thread, because the piezoelectric stack inside the EM Drive would be a small modification of the EM Drive, just like using a polymer insert inside an EM Drive.
The overarching principle governing this thread since thread #1 is that it is about the proposed device: an asymmetric electromagnetic resonant cavity that can accelerate in Deep Space solely due to electric power input . This thread has never favored a particular theory to explain its effect, nor it has ever excluded a particular theory to explain its effect. One of the main experimenters (Paul March) always considered the Mach effect one of the main explanations. Hopefully this thread can remain the way it has been since thread #1. No need to start now excluding any particular theories from discussion to explain the EM Drive effect in this thread.
-
#1011 by Bob012345 on 26 Sep, 2016 16:31
-
What I am trying to say is that the folks that say there is an energy violation are comparing energy in different frames. You can use the Work-Energy Theorem in any observer frame and you'll see energy balances. I believe nature doesn't care how you generate your constant force.
No, we are not comparing between different frames. Go see this post. Gilbertdrive did those calculations in a single frame the observer at rest in the frame that is the initial rest frame of the drive. The starting stored energy, and the final kinetic energy show a huge problem.
...
The only people who are jumping frames here are Woodward and TheTraveller. They seem to think they can treat a non-inertial frame as if it was inertial. You have the right criticism, directed at the wrong group.
As for the rest of your postQuoteFor light k= 1/c. For beamed power k= 2/c. For photon recycling k= n/c. For EmDrive k= figure of merit.
This would be for a recycling photon rocket, that uses a retroreflector on the moon (for example). Then, the energy of the photon beam (decreasing due to redshift), and the momentum/energy exchange with the moon make everything balance. Classical mechanics (with special relativity applied because of the photons) works perfectly fine here. Claims otherwise are wrong.
The emDrive is completely different because according to Shawyer it works as a closed system.
The statement "Since the 10 years of operation of the 200Kwe generator gives only 6.311*10^13 Joules" is in the ships frame or really, frames. If you claim it's also in the observer frame you are ignoring the multiplicative factor that converts between frames.
I disagree regarding your statement regarding photon recycling. In the limit as the ship approaches c, the total energy of the beam is converted to ship kinetic energy at 100% for the whole trip. Of course, the integrated beam energy approaches the limit from above, meaning more energy used that kinetic energy generated over the whole trip. So, if even one photon is used more than once during the entire trip, in the limit the beam energy will be just slightly less than the kinetic energy even accounting for redshifts.
If you think the ship will just stop accelerating at some point, please provide a physical mechanism rather than just asserting energy conservation. -
#1012 by Flyby on 26 Sep, 2016 16:39
-
If I understand you correctly, you would not need to start with a printed master. A lost wax master near enough the final dimensions needed could be fabricated from clay or ceramics at far less expense, then milled to the desired finished net-shape. Casting the copper to a close approximation before milling would save $$, compared to starting with a solid block. And if the end product were to be plated with a greater than skin depth silver, the purity of the cast copper may not even be as much of an issue.
If I had an educated guess, the cheapest option would be to 3dprint directly in ceramic powder using a binder. Its surface needs then to be smooth using a filler, cured, then glazed and cured again.
I have not tried it myself, but glazed ceramics can be copper plated...You'll then have a smooth surface without the need of machining.
And please, to all DIY's out there...Don't use the popular ceramic-PLA filaments as they contain way too much PLA and could melt at low temperatures. Same applies for those copper/bronze, etc filaments.. -
#1013 by Gilbertdrive on 26 Sep, 2016 16:49
-
The statement "Since the 10 years of operation of the 200Kwe generator gives only 6.311*10^13 Joules" is in the ships frame or really, frames. If you claim it's also in the observer frame you are ignoring the multiplicative factor that converts between frames.
It is in the ship frame. I did not made the calculus of how much time was elapsed in the Earth frame. Anyway it will not change the magnitude of the problem : around 10^7. More than 10 years will have occured on earth, but not 100 million years. -
#1014 by rfmwguy on 26 Sep, 2016 16:55
-
Thanks for agreeing. EmDrive, as titled originally, was focused on a specific device; what Roger Shawyer developed and others picked up on which was an RF resonant cavity in the shape of a frustum. Its just that simple and uncomplicated.Delineating competitive theories and hardware is critical for the readership imho especially for science media whom are following emdrive closely. "Closed" RF frustum cavities are the emdrive. Cannae is not and neither is Woodward's Mach effect nor nassikas. Trying to blur the lines seems disingenuous as these 8 threads have been emdrive from day 1.
Coe/com can apply anywhere and is a well discussed subtopic here. My vote has always been towards staying on topic rather than attempting to broaden an otherwise large topic. Emdrive is already a massive thread series, no need to boost it with Mach effect, nassikasn or cannae.
Like you, I'm just a part time poster here with my own point of view. Nsf staff can decide if renaming or broadening emdrive is the best thing to do.
Personal opinion: I would also like that the discussion remains focused and on topic. A big part of the success of this forum (because it is the most fruitful public Internet discussion I have ever seen) comes from the strong focus on experiments and proof of theories explaining the Emdrive.
I understand Mach effect/GR extension theories look like very likely candidates now for explaining this phenomenon, if further experiments confirm it exists, but the Emdrive is objectively a wholly different device in its form and outwardly visible mechanics in comparison with Prof. Woodward's own device; they were found/conceived in very different circumstances and both deserve independent analysis and experimentation.
Mostly because we don't really know if they really are manifestations of a same physical principle yet (this requires a lot more experimentation!) or how any or both of them will behave under new test conditions, including if they can scale from theoretically interesting to practically usable forces. Which let's remember, it's the reason this topic has found a place in this highly esteemed and reputable forum focused on space exploration, including propulsion topics.
Variations will occur, with differing sizes/RF frequencies, but there is a reason Cannae is not an EmDrive, it is not a frustum. There is a reason mach effect is not an EmDrive, which are blatantly obvious. Nassikas thruster, vasimir, etc., etc are not emdrive.
Regardless of the unifying theories that may exist, it should pertain to EmDrive here or be posted on a more relevant topic thread chosen from this section that NSF has generously provided: http://forum.nasaspaceflight.com/index.php?board=73.0 -
#1015 by tchernik on 26 Sep, 2016 17:11
-
I'm not sure Cannae's pillbox cavity should be considered as different from the Emdrive. Even if the shape is different, the mechanics seem to be very similar: asymmetric resonant microwave cavities. It would add some unnecessary overhead to have to track the Cannae drive updates in some other topic IMO.
I agree with you and with Dr. Rodal that discussion around/pertaining to piezoelectric/electrostictive stack devices belongs to Woodward effect's own topic.
But any theoretical discussion trying to explain the Emdrive as described above (asymmetric resonant microwave cavities) I do think it belongs here. -
#1016 by Star One on 26 Sep, 2016 17:43
-
I don't know why there isn't a separate thread for theoretical explanations leaving this one for experiments and data alone. It doesn't aid attempting to follow the theoretical discussion to have it suddenly deviating into the latest techniques on 3D printing.
-
#1017 by OnlyMe on 26 Sep, 2016 17:45
-
What I am trying to say is that the folks that say there is an energy violation are comparing energy in different frames.
I still fail to see what is wrong with comparing energy in different inertial frames, as long as you're being careful. Of course kinetic energy is different in different frames, but the total energy must be conserved no matter what intertial frame you choose. It's easy to show that while the kinetic energy of a "constantly accelerating device" grows faster and faster in a "rest" frame as the device speeds up, this gets offset by other factors (kinetic energy of the propellant in the case of a conventional rocket, etc), so that the total energy spent over a unit of time is exactly the same, regardless of the reference frame.
There are many problems with the underlying issues, not just attempting to evaluate the acceleration including kinetic energy.
First, the claim of constant uniform acceleration has not been shown to occur, in any real sense. That is in a vacuum and sufficiently distant from a gravity well that the test has any real value.
Second, if an EmDrive that already had reached an escape velocity with respect to any associated gravity well were turned on and began to accelerate, the only frame of reference of any significance would be the frame of reference of the drive itself and kinetic energy would not be an issue, it would remain zero. Here the only question would be whether constant acceleration actually occurs. Something that no one will know with any certainty until it is attempted, or has been other wise proven false by other means.
The over unity issue I believe is a bad argument because it requires in essence, that the energy (including kinetic), of an accelerating drive be evaluated from a (essentially preferred) inertial frame of reference. While the acceleration is always from the drive's already accelerating frame.
That becomes an old and tired special relative problem (paradox, non-paradox), because it also requires that at some point the drive return to the preferred inertial frame. Remember the EmDrive's frame is accelerating. If it does not return, calculations of kinetic energy from the preferred inertial frame have no meaning or significance. The customary way that a return occurs, is if the drive makes a turn around maneuver, to head back... Which adds to the debate, an issue of whether the turn around point is really inertially consistent with the preferred frame.., and.., that one would have to assume that no attempt to match velocities on return is made. If any attempt to match velocities is part of the problem (and one remembers gravity set aside), that the starting and finishing line, is from an outbound escape velocity to an inbound escape velocity, from the drive's frame of reference it will have taken the same energy for acceleration and deceleration on each leg of the trip. Kinetic energy is not an issue in the drive's frame of reference... (setting escape velocity as the start/finish removes any gravity associated with the preferred inertial frame from the problem)
Before any of these issues become even remotely important, we need an EmDrive that works in an always on condition, and even then they will not be tested until someone puts one into space and points it, at least toward another planet and perhaps toward another star. If that ever happens, I suspect there will be a great deal of rethinking how we interpret much of what we think we know today. -
#1018 by Rodal on 26 Sep, 2016 17:46
-
I don't know why there isn't a separate thread for theoretical explanations leaving this one for experiments and data alone. It doesn't aid attempting to follow the theoretical discussion to have it suddenly deviating into the latest techniques on 3D printing.
Yes, that would be a more clear and logical split of the thread . It was first proposed on thread 2 or 3, but the consensus at that time was to keep experimental and theoretical discussions in the same thread. If I recall correctly the consensus was that keeping both experimental and theoretical discussions together would foster synergy, and lead to better experiments.
And conversely, better experiments, as, for example the experiments from SeeShells and Monomorphic, would lead to better examination of theoretical explanations.
SeeShells and Monomorphic, who, instead of following a single theoretical course, are pursuing different explanations in parallel: with and without polymer inserts. SeeShells also exploring interferometry changes (with her central quartz rod). Monomorphic pursuing different shapes (conical and flat sides). SeeShells pursuing numerical calculations with Meep, with Aero. Monomorphic using FEKO for calculations. SeeShells pursuing all avenues "the kitchen sink"
Looking back, we must admit that there has been great synergy in the past threads ! -
#1019 by Bob012345 on 26 Sep, 2016 17:56
-
What I am trying to say is that the folks that say there is an energy violation are comparing energy in different frames.
I still fail to see what is wrong with comparing energy in different inertial frames, as long as you're being careful. Of course kinetic energy is different in different frames, but the total energy must be conserved no matter what intertial frame you choose. It's easy to show that while the kinetic energy of a "constantly accelerating device" grows faster and faster in a "rest" frame as the device speeds up, this gets offset by other factors (kinetic energy of the propellant in the case of a conventional rocket, etc), so that the total energy spent over a unit of time is exactly the same, regardless of the reference frame.
It's not wrong to compare but to equate. Some are saying power expended x time in the ships frame must equal or exceed the total kinetic energy in the earth observer frame where the ship starts from rest. And if the velocity exceeds a critical number, the acceleration just falls off to conserve energy. I used to think that but now I don't. What magic mechanism alerts the ship that it's crossed that number wrt earth frame and decreases the acceleration?
Consider a hypothetical rocket that can do 10000 burns at a delta v of 1000 m/s. Each burn requires a total energy of E, maybe only 1% goes to the ship. After the first burn, the kinetic energy of the ship wrt earth is 5E5/kg so assume the burn released 5E7 J/kg in its frame. What's the total energy released in the ships frame after 10000 burns? It should be 5E10J/kg. What's the kinetic energy wrt earth? It should be 5E13J/kg. No doubt some will claim nature conspires to prevent this by making the mass requirements great enough so it's never practical to make such a rocket. That's saying an EMDrive like device should never work at all. But if it works at all, there is no feasible mechanism I am aware of to decrease acceleration for a fixed force at a fixed power.
Consider that rocket doing the first burn seen from two frames, earth and another frame moving at 0.5c in the opposite direction. From earth, the first burn gives the ship a kinetic energy of 5E5J/kg. From the other frame the kinetic energy gain of the ship is huge from that burn 1.5E11J/kg. But counting the exhaust, it's the same energy released by the ship. There are frames where the energy balance is negative and energy burn is more than kinetic energy in that frame and there are frames where energy burn is less than the ships kinetic energy in that frame. All frames agree how much energy the ship burned as actual fuel. In all frames one can use the work energy theorem and get a prefect balance between force, distance and energy. According to some, the acceleration from the burns deceases to preserve CoE in some frames, but not others. This is chaos.
and CoE verified.
