Author Topic: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive  (Read 192309 times)

Offline JasonAW3

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #200 on: 05/01/2015 01:40 PM »
Ok,

     Let me see if I can break this down to its simplest elements that laymen can understand.

     One, in order for it to the drive to work, energy has to be expended to create a propulsive force. (ie. Thrust)

     Two, "for every action, there has to be an equal and opposite reaction".  Basic Newtonian Physics, not a hundred percent accurate, but close enough.

     Three, electricity is being used to create radio Frequencies within "The Device".

     Four, somehow, these "Radio Waves" are imparting their energy to "The Device" in such a way as to produce kinetic force.  (ie. Thrust)

     Five, the "Radio Waves" seem to be being expended in a direction opposite of the direction of thrust, if I understand the diagrams I have seen so far.

     Six, since energy is matter in a more coherent form than lasers or plasma, mass is being expended in a direction opposite the direction of motion.

     Seven, again, unless I am misunderstanding these diagrams, heat is being generated as part of this conversion of energy to thrust.

     Eight, in order to continue to generate thrust, more energy must be expended in order to generate RF, which is converted by "The Device" into heat and thrust.

     Nine, so, in order to generate thrust; mass, in the form of energy, is being expended and expelled in a direction of motion opposite of the direction of thrust, energy is being used to impart this motion. heat is being generated as a byproduct of this process, and an amount of energy, similar to or larger than the normal amount of energy needed to break free of inertia and produce thrust, is being used, and if no additional energy is applied to the device, it stops generating thrust.  I think that pretty much sums up what we know so far.

     So, Ten, it appears as though this device is a more efficient form of thrust convertion device than are chemical, plasma or nuclear rockets, which require mass be expended in the form of propellent, in order to produce thrust.  It appears that mass, in the form of electrons, in this case, are being expended in order to impart thrust, but doing so in a much more energy efficent manner.

     Finally, if "The Device" is indeed producing thrust in this manner, and we don't quite have a grasp on HOW it's doing what it does, (I'm pretty sure there is some very simple explaination that everybody is overlooking, as these things usually wind up being) I'm not really quite sure WHAT particular law of physics that it is violating. non-of the lawsof motion or thermodynamicsa appear to be violated on the face of it. So, if it is indeed producing thrust as all the tests so far seem to indicate, now all we need to do is figure out HOW it's doing it!
Heat is created by eddy currents in the walls of the cavity. They draw energy from the cavity energy, reducing stored cavity energy and cavity Q which is energy input per cycle to energy loss per cycle. This loss energy reduces cavity stored energy and thrust. The heat loss is not involved in thrust generation. It actually reduces thrust.

No mass is being expelled.

Please read: http://www.emdrive.com/theorypaper9-4.pdf

Simple question; Do electrons have mass?  If not, you are correct, if so, mass is being expended.  Perhaps minute quantities, but it IS being expended.

From Jefferson Labs in Virginia: Electron = 9.1093897*10-31 kg.
« Last Edit: 05/01/2015 01:42 PM by JasonAW3 »
My God!  It's full of universes!

Offline TheTraveller

That is what I was asking when I asked if it accelerated constantly. I mean constantly with constant power input. If power input is constant then total energy input increases linearly with time producing constant acceleration so velocity increases linearly with time. But kinetic energy increases with the square of velocity and so increases with the square of time.

Power input (electrical energy) is constant while energy output (kinetic energy) is growing much faster and at an ever increasing rate. That violates COE. That is because kinetic energy is proportional to the square of velocity.

If you had an electric car, 100% efficient and no friction losses, and gave it constant power input it would not accelerate constantly. It would start off with good acceleration but that would quickly fall to near zero as its velocity increased. You would need ever higher power inputs in order to just maintain constant acceleration. If your EMdrive works any different then it violates COE.
Deep space Ion / Hall thrusters have constant energy input, resultant constant thrust as long as fuel lasts. They accelerate the craft to faster and faster velocities.

EMDrive is no different, has constant energy input, resultant constant thrust, except it doesn't expel mass at a high velocity nor require fuel other than to supply the electricity generators.
« Last Edit: 05/01/2015 01:55 PM by TheTraveller »
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Offline TheTraveller

Simple question; Do electrons have mass?  If not, you are correct, if so, mass is being expended.  Perhaps minute quantities, but it IS being expended.

From Jefferson Labs in Virginia: Electron = 9.1093897*10-31 kg.
Forget me. I'm just the messenger.

Shawyer has been building and testing EMDrives since 2003. In 2009 he had a demo EMDrive available for anyone to test. See attached photo. Did anyone / NASA test? I assume the Chinese did and built their own EMDrive with Shawyer's help.

Please refer to his equations: http://www.emdrive.com/theorypaper9-4.pdf

Nothing is leaving the cavity but eddy current skin heat losses, which REDUCE the thrust. Note Shawyer has gone to superconducting cavity walls to REDUCE heat losses, that reduce cavity Q, which reduce cavity thrust generation.

Think of this as coil DC resistance losses, which reduce AC coil Q and the level of mag field "B" generation.
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
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Offline Nilof

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #203 on: 05/01/2015 01:57 PM »
So how exactly does that apply to the case where it is traveling at a constant velocity and fighting friction? By the principle of relativity, there is no difference between the case of static thrust and the case of static velocity. So you can still use this to create more work than you put into it.
If the ship is travelling at constant velocity, there is no acceleration occurring, no thrust being produced by the EMDrive, so the EMDrive is switched OFF.

When the EMDrive generates thrust, unless restrained from moving, it will cause the mass of what ever it is attached to move / accelerate, dropping resonate cavity Q, causing the EMDrive microwave load impedance to drop, causing the microwave generator to transfer more energy into the resonate cavity to restore the loss of cavity energy converted to kinetic, causing the microwave generator to draw more power from the primary electrical energy source.

COE is conserved.

All EMDrive does is to convert electrical energy into, if the EMDrive moves, kinetic energy. No OU. No free energy.

Ok a new / strange energy conversion technique but so was the 1st coil generating a magnetic field, so was the 1st motor, converting electrical energy into a magnetic field, into torque.

For the coil, the motor and the EMDrive, COE was conserved.

Interesting history of the development of electrical energy being converted into torque:
http://en.wikipedia.org/wiki/Timeline_of_the_electric_motor

Soon to be added: History of the development of electrical energy being converted into kinetic energy:

Sigh. The thrust reported from the EM drive tests is from a static test article. It is not moving. Does that mean the drive is turned off? Of course not.

Now consider the exact same test stand, but on a train moving at a constant speed. The difference here is that since the train is moving in the direction the force is applied, you will get work out of it. If the train's speed is higher than the power to thrust ratio of the drive, the work applied to the train is higher than the power fed into the drive. So you can connect a dynamo to the train's wheels to take out energy that you can feed back into the drive.

For rockets, this is just the Oberth effect. The kinetic energy of the propellant is fed into what remains of the rocket. But in the case where there is no propellant used up, you violate conservation of energy.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #204 on: 05/01/2015 01:58 PM »
A FAQ will not change the fact that you are on the horns of a dilemma. Either the thing accelerates constantly and you violate energy and momentum or it does not and you create a preferred frame of reference. Which is it?
Force is not Work.

Shawyer clearly states when the cavity moves, it's Q drops, which means it's load impedance as seen by the microwave generator on board the ship drops. This causes the microwave generator to deliver more energy into the resonate cavity to restore the lost cavity energy (due to lower cavity Q due to cavity energy converted into Kinetic energy by the EMDrive) from the electrical source

No where does Shawyer claim the EMDrive will constantly accelerate, as you assume, without needing more microwave energy to be inputted into the resonate cavity.

If you would like to review what Shawyer has said, please read all the papers and links here: www.emdrive.com

See his theory paper and equations for power needed to support EMDrive acceleration:
http://www.emdrive.com/theorypaper9-4.pdf

I never said force is work. Force times distance is work but I have no idea why that is relevant here.

I do not assume that the thing accelerates constantly. I asked you if it accelerates constantly. You see if it accelerates constantly you have one problem and if it does not you have a different problem.

Ok you are going with it does not accelerate constantly although getting that out of you was like pulling teeth. Do you understand how this violates relativity and just about all of modern physics? It would almost be simpler to violate COE.

For example it creates the problem that the power needed by the drive would change massively depending on the time of year. Do you understand why?

Ok,

     Let me see if I can break this down to its simplest elements that laymen can understand.

     One, in order for it to the drive to work, energy has to be expended to create a propulsive force. (ie. Thrust)

     Two, "for every action, there has to be an equal and opposite reaction".  Basic Newtonian Physics, not a hundred percent accurate, but close enough.

     Three, electricity is being used to create Radio Frequencies within "The Device".

     Four, somehow, these "Radio Waves" are imparting their energy to "The Device" in such a way as to produce kinetic force in one particular direction.  (ie. Thrust)

     Five, the "Radio Waves" seem to be being expended in a direction opposite of the direction of thrust, if I understand the diagrams I have seen so far.

     Six, since energy is matter in a more coherent form than lasers or plasma, mass is being expended in a direction opposite the direction of motion.

     Seven, again, unless I am misunderstanding these diagrams, heat is being generated as part of this conversion of energy to thrust.

     Eight, in order to continue to generate thrust, more energy must be expended in order to generate RF, which is converted by "The Device" into heat and thrust.

     Nine, so, in order to generate thrust; mass, in the form of energy, is being expended and expelled in a direction of motion opposite of the direction of thrust, energy is being used to impart this motion. Heat is being generated as a byproduct of this process, and an amount of energy, similar to or larger than the normal amount of energy needed to break free of inertia and produce thrust, is being used, and if no additional energy is applied to the device, it stops generating thrust.  I think that pretty much sums up what we know so far.

     So, Ten, it appears as though this device is a more efficient form of thrust convertion device than are chemical, plasma or nuclear rockets, which require mass be expended in the form of propellent, in order to produce thrust.  It appears that mass, in the form of electrons, in this case, are being expended in order to impart thrust, but doing so in a much more energy efficent manner.

     Finally, if "The Device" is indeed producing thrust in this manner, and we don't quite have a grasp on HOW it's doing what it does, (I'm pretty sure there is some very simple explaination that everybody is overlooking, as these things usually wind up being) I'm not really quite sure WHAT particular law of physics that it is violating. none of the laws of motion or thermodynamics appear to be violated on the face of it. So, if it is indeed producing thrust, as all the tests so far seem to indicate, now all we need to do is figure out HOW it's doing it!

Oh! I also forgot to mention that the amount of theurst varies according to both the input of energy and the frequency of the RF generated.  (From what I think I understand, the higher the frequency, the more thrust is directly cvreated by "The Device")  Again, no violation of thermodynamics or Newtonian physics.

If the thing is getting thrust by ejecting mass then it is just a rocket. But it cannot be getting thrust by ejecting electrons or photons as that would be easily noticed and would need a great deal of energy to do. It also has the problem of any rocket in that it quickly runs out of whatever it is using as reaction mass. The best it can do is eject photons and to get the thrust reported you would need a huge power input and you would probably burn down the lab.

But that is a change of subject. If the thing gets constant acceleration with constant power input then it violates COE because Ke goes with the square of velocity. And if the thing does not accelerate constantly with constant power input it violates relativity.

Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #205 on: 05/01/2015 02:02 PM »
Ok,

     Let me see if I can break this down to its simplest elements that laymen can understand.

     One, in order for it to the drive to work, energy has to be expended to create a propulsive force. (ie. Thrust)

     Two, "for every action, there has to be an equal and opposite reaction".  Basic Newtonian Physics, not a hundred percent accurate, but close enough.

     Three, electricity is being used to create radio Frequencies within "The Device".

     Four, somehow, these "Radio Waves" are imparting their energy to "The Device" in such a way as to produce kinetic force.  (ie. Thrust)

     Five, the "Radio Waves" seem to be being expended in a direction opposite of the direction of thrust, if I understand the diagrams I have seen so far.

     Six, since energy is matter in a more coherent form than lasers or plasma, mass is being expended in a direction opposite the direction of motion.

     Seven, again, unless I am misunderstanding these diagrams, heat is being generated as part of this conversion of energy to thrust.

     Eight, in order to continue to generate thrust, more energy must be expended in order to generate RF, which is converted by "The Device" into heat and thrust.

     Nine, so, in order to generate thrust; mass, in the form of energy, is being expended and expelled in a direction of motion opposite of the direction of thrust, energy is being used to impart this motion. heat is being generated as a byproduct of this process, and an amount of energy, similar to or larger than the normal amount of energy needed to break free of inertia and produce thrust, is being used, and if no additional energy is applied to the device, it stops generating thrust.  I think that pretty much sums up what we know so far.

     So, Ten, it appears as though this device is a more efficient form of thrust convertion device than are chemical, plasma or nuclear rockets, which require mass be expended in the form of propellent, in order to produce thrust.  It appears that mass, in the form of electrons, in this case, are being expended in order to impart thrust, but doing so in a much more energy efficent manner.

     Finally, if "The Device" is indeed producing thrust in this manner, and we don't quite have a grasp on HOW it's doing what it does, (I'm pretty sure there is some very simple explaination that everybody is overlooking, as these things usually wind up being) I'm not really quite sure WHAT particular law of physics that it is violating. non-of the lawsof motion or thermodynamicsa appear to be violated on the face of it. So, if it is indeed producing thrust as all the tests so far seem to indicate, now all we need to do is figure out HOW it's doing it!
Heat is created by eddy currents in the walls of the cavity. They draw energy from the cavity energy, reducing stored cavity energy and cavity Q which is energy input per cycle to energy loss per cycle. This loss energy reduces cavity stored energy and thrust. The heat loss is not involved in thrust generation. It actually reduces thrust.

No mass is being expelled.

Please read: http://www.emdrive.com/theorypaper9-4.pdf

Simple question; Do electrons have mass?  If not, you are correct, if so, mass is being expended.  Perhaps minute quantities, but it IS being expended.

From Jefferson Labs in Virginia: Electron = 9.1093897*10-31 kg.

Yes electrons have very tiny mass and to get thrust you would need huge amounts of them traveling at near light speed. The energy demand would be huge and the radiation would cook you.

Offline TheTraveller

Yes electrons have very tiny mass and to get thrust you would need huge amounts of them traveling at near light speed. The energy demand would be huge and the radiation would cook you.
Please read Shawyer. www.emdrive.com

The higher the Q, the higher the effect of bouncing cavity stored energy mass on thrust. Shawyer has been doing this since 2003. Building real world devices that produce 1,000x the thrust of EW's mosquito thrust devices.

BTW nothing but waste eddy current heat leaves the cavity. Causes NO thrust. In fact reduces cavity Q, stored energy and thrust. This is why Shawyer / Cannae went to superconducting walls. to reduce wall eddy current losses that reduce cavity Q and reduce thrust force generation.

This is a real world almost self contained 2009 EMDrive device demo device that produces 25g thrust from 1.2 kW magnetron input energy: http://emdrive.com/demonstratorengine.html

Why was it NEVER publicly tested by NASA?
Hard to miss 214mN/kW thrust when pwr input is 1.2 kW. Should get 25g thrust. Can feel that with your hand.

Either is bends the EW thrust test system from over the top thrust generation or it is nothing. Simple to test. Ends all discussion about if it works or not.

Paul / Sonny why was this Shawyer demo 2009 EMDrive NEVER tested?
End the does it work or not speculation.
Test it.
Draw a line in the sand.
It works as claimed or it is nothing and time to move on.

Or is there an issue that Shawyer helped the Chinese to build their EMDrive, after the West rejected / called him a fraud and he is not welcome at the EW/NASA door?
« Last Edit: 05/01/2015 02:41 PM by TheTraveller »
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Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #207 on: 05/01/2015 02:37 PM »
That is what I was asking when I asked if it accelerated constantly. I mean constantly with constant power input. If power input is constant then total energy input increases linearly with time producing constant acceleration so velocity increases linearly with time. But kinetic energy increases with the square of velocity and so increases with the square of time.

Power input (electrical energy) is constant while energy output (kinetic energy) is growing much faster and at an ever increasing rate. That violates COE. That is because kinetic energy is proportional to the square of velocity.

If you had an electric car, 100% efficient and no friction losses, and gave it constant power input it would not accelerate constantly. It would start off with good acceleration but that would quickly fall to near zero as its velocity increased. You would need ever higher power inputs in order to just maintain constant acceleration. If your EMdrive works any different then it violates COE.
Deep space Ion / Hall thrusters have constant energy input, resultant constant thrust as long as fuel lasts. They accelerate the craft to faster and faster velocities.

EMDrive is no different, has constant energy input, resultant constant thrust, except it doesn't expel mass at a high velocity nor require fuel other than to supply the electricity generators.

A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.




Offline TheTraveller

A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.
Ion drive / Hall thruster / Vasimr uses fuel & electrical power. As long as it has fuel and electrical power, it can continuously accelerate or decelerate. Initially increasing craft velocity & kinetic energy, until it must turn 180 deg and decelerate to obtain orbit.

EMDrive does the same. Just no mass/ fuel is expelled, However some form of primary energy is used to generate electrical energy (as occurs in Ion / Hall thruster), which is then converted into kinetic energy and accelerates / decelerates the craft.

Different dog. same leg action.

Some form of primary energy is converted into kinetic energy.
COE is conserved.
« Last Edit: 05/01/2015 02:56 PM by TheTraveller »
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Offline gospacex

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #209 on: 05/01/2015 03:16 PM »
A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.
Ion drive / Hall thruster / Vasimr uses fuel & electrical power. As long as it has fuel and electrical power, it can continuously accelerate or decelerate. Initially increasing craft velocity & kinetic energy, until it must turn 180 deg and decelerate to obtain orbit.

EMDrive does the same.

Gosh.

IT IS NOT THE SAME!!!!!!

Having reaction mass expelled *changes everything*! For one, now you need to include reaction mass' kinetic energy into energy balance.

Constant acceleration reactionless drive of any type violates COE.

Offline Nilof

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #210 on: 05/01/2015 03:23 PM »
A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.
Ion drive / Hall thruster / Vasimr uses fuel & electrical power. As long as it has fuel and electrical power, it can continuously accelerate or decelerate. Initially increasing craft velocity & kinetic energy, until it must turn 180 deg and decelerate to obtain orbit.

EMDrive does the same. Just no mass/ fuel is expelled, However some form of primary energy is used to generate electrical energy (as occurs in Ion / Hall thruster), which is then converted into kinetic energy and accelerates / decelerates the craft.

Different dog. same leg action.

Some form of primary energy is converted into kinetic energy.
COE is conserved.

I'll ask you to read this wikipedia article before you make any further comment on rockets and conservation of energy. The fact that rockets have to bring their propellant with them is central to conservation of energy.
« Last Edit: 05/01/2015 03:23 PM by Nilof »
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Robotbeat

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #211 on: 05/01/2015 03:27 PM »
Of course, your kinetic energy would be ridiculously high, thousands of times greater than the energy you put into the drive.

For .4N/kW and 40kg/kW specific power for a 1kW craft (weighing 40kg) just to make things easy:

(Kinetic Energy)/(Energy input)=
(.5*40kg*(92years*.4N/kW/(40kg/kW))^2)/(1kW*92years)
=
5806.5

Make no mistake, this is also a method to gain free energy.
Another useful meme is to beware of people who have simple answers to complex questions.

If Dr White's team is right this thruster is more akin to a propeller or the air breathing nuclear ramjet of project PLUTO, and the "reaction mass" are the virtual particles being preferentially accelerated by the system.

An interesting (but off topic) question would be does a virtual particle cease to exist entirely IE it's whole life is the single existence it's there for, or does it pop up "elsewhere," and is that "elsewhere" this universe, or another universe?

But let me ask you a simpler question.

Do you believe there is something there or IYHO it's all a set of experimental artifacts that have simply not been analyzed out thoroughly enough?

I was talking about the article, which suggests it is useful for interstellar travel and the article gave some example calculations. If you look at the kinetic energy from those equations and compare it to the energy input, you see they are orders of magnitude apart. No doubt it would be fantastic for interstellar travel. But by the same logic, you can get a huge amount of energy out of it, far more than you put in. Call that what you will, but those are the results.

And yes, never underestimate the ability to fool yourself. "The first principle is that you must not fool yourself, and you are the easiest person to fool." I think most people who have not had at least an undergraduate education in physics have a hard time appreciating this fact. And it's even worse in graduate school, where the training wheels start to come off, and you realize just how hard it is to puzzle out what's real and what isn't in experiments that are not set up for you by someone holding your hand through the whole thing. When this has been appreciated, then we can start talking about virtual particles and the like.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #212 on: 05/01/2015 03:39 PM »
A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.
Ion drive / Hall thruster / Vasimr uses fuel & electrical power. As long as it has fuel and electrical power, it can continuously accelerate or decelerate. Initially increasing craft velocity & kinetic energy, until it must turn 180 deg and decelerate to obtain orbit.

EMDrive does the same. Just no mass/ fuel is expelled, However some form of primary energy is used to generate electrical energy (as occurs in Ion / Hall thruster), which is then converted into kinetic energy and accelerates / decelerates the craft.

Different dog. same leg action.

Some form of primary energy is converted into kinetic energy.
COE is conserved.

No, the constant power input of any rocket is an illusion created by not taking into account the energy used to accelerate your fuel. By pumping Kinetic energy into the fuel you are giving it more energy and so the power input of a rocket is far from constant.

Say I'm on roller skates and throw a brick converting one unit of my chemical energy to one unit of kinetic energy and gaining one unit of velocity. Now say I throw another brick using the same amount of chemical energy and gaining another unit of velocity. But since Ke goes with the square of velocity this time I have gained three units of Ke. Why did the first unit of chemical energy convert to one unit of Ke while the second unit of chemical energy convert to three units of Ke? And the next brick would convert one unit of chemical energy to five units of Ke. It seems like constant power input produces an ever increasing output. How do we resolve this paradox?

Well first I'm neglecting the weight of the bricks but the more important answer is that I'm neglecting the higher Kinetic energy of each successive brick. The first brick imparts some Ke into the second brick which must be taken into account when I throw the second brick. The input from the second brick is the chemical energy plus the Ke of the second brick. Thus the power input of my roller skate rock isn't really constant.

You cannot say the same about the EMdrive. It does not throw bricks and it does not carry reaction mass. Therefore the input power really is constant and the output really is ever increassing until it violates COE.


Offline AdrianW

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #213 on: 05/01/2015 03:59 PM »
@TheTraveller: You seem to be misunderstanding very, very basic physical concepts (kinetic energy, closed/open systems, and conservation of energy), which is reflected by your inability to properly respond to ppnl's questions. I suggest you read up on these concepts if you want to participate in any reasonable discussion about advanced physics problems.

Hats off to ppnl for his/her patience in explaining the dilemma! :)

Note: I'm not saying that the reported effects are real or not. I'm also not saying that the EM drive works/doesn't work as advertised. Heck, I'd gladly throw relativity or the law of CoE in the trash if there's overwhelming evidence to the contrary. Right now, there really isn't.
Let's wait for further experimental evidence, whether it's supporting or refuting the claims.

Offline notsorandom

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #214 on: 05/01/2015 04:34 PM »
This all pretty much boils down to two questions.
1. Is this device creating thrust? - Has not been ruled out that this is an artifact of the experiment but possible causes are being retired.
2. Can this device generate thrust in the stated application in space? - Dunno yet

This seems almost too good to be true. It is a small device and uses a manageable amount of power. This isn't like the warp drive theories which require negative density matter and all other sorts of unattainable or horrendously expensive things. When it comes to a lot of these other breakthrough propulsion concepts they are not realistically testable at this point. Debating the theory behind them is the most that can practically be done. This EM drive is different because it can be tested. This should be one particularly easy dragon to slay without even needing to worry about theory. So other labs should build and measure these things to build up rigor and drive down the chance there is something in the experiment causing this effect. If it still seems to work then fly a test in space. If it does what its supporters claim it will then I for one won't really care how it works. Not like I could understand it if I did care.

Offline TheTraveller

A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.
Ion drive / Hall thruster / Vasimr uses fuel & electrical power. As long as it has fuel and electrical power, it can continuously accelerate or decelerate. Initially increasing craft velocity & kinetic energy, until it must turn 180 deg and decelerate to obtain orbit.

EMDrive does the same.

Gosh.

IT IS NOT THE SAME!!!!!!

Having reaction mass expelled *changes everything*! For one, now you need to include reaction mass' kinetic energy into energy balance.

Constant acceleration reactionless drive of any type violates COE.
EMDrive violates the Rocket Equation as no ISP from expelled high velocity fuel mass but not overall COE.

The kinetic energy gain of the accelerated mass is matched by that drawn from the primary energy source, minus losses.

See Shawyer's equations for dynamic operation:
http://www.emdrive.com/theorypaper9-4.pdf

Apologies if my explanations fails to convey how EMDrive works different to expelled mass rocket engine. Suggest need to stop comparing to conventional rocket engine and focus on overall primary energy input to final accelerating mass kinetic energy gain.
« Last Edit: 05/01/2015 05:14 PM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.
Herman Melville, Moby Dick

Offline AdrianW

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #216 on: 05/01/2015 05:48 PM »
The kinetic energy gain of the accelerated mass is matched by that drawn from the primary energy source, minus losses.
This implies that there's a preferred frame of reference, which in turn implies that the thrust and the efficiency of the EM drive depends on it's orientation (because the Earth is moving through space) and on the time of day (because the Earth is rotating and thereby changing the experiment's velocity relative to the preferred frame of reference).

Offline Raj2014

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #217 on: 05/01/2015 05:59 PM »
A lot of news websites have been posting about this. The news about the EM drive has grown a lot in the last two days. When they have done more testing and the results as promising. Soon it will be on the news channels. They should get a lot of funding. How many years will it be when we see this technology be used?

Offline ppnl

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Re: FEATURE ARTICLE: Evaluating NASA's Futuristic EM Drive
« Reply #218 on: 05/01/2015 06:01 PM »
A Hall thruster is just a rocket and like any rocket it takes its reaction mass with it so it can have constant acceleration with (apparent) constant power. That would suggest that it does better than a electric car which can't accelerate constantly with constant power. But that is an illusion. The Hall thruster is using massive amounts of energy to accelerate its reaction mass and as a result it will always do much worse than the car. A rocket will always run out of fuel long before its kinetic energy exceeds the energy content of its fuel.
Ion drive / Hall thruster / Vasimr uses fuel & electrical power. As long as it has fuel and electrical power, it can continuously accelerate or decelerate. Initially increasing craft velocity & kinetic energy, until it must turn 180 deg and decelerate to obtain orbit.

EMDrive does the same.

Gosh.

IT IS NOT THE SAME!!!!!!

Having reaction mass expelled *changes everything*! For one, now you need to include reaction mass' kinetic energy into energy balance.

Constant acceleration reactionless drive of any type violates COE.
EMDrive violates the Rocket Equation as no ISP from expelled high velocity fuel mass but not overall COE.

The kinetic energy gain of the accelerated mass is matched by that drawn from the primary energy source, minus losses.

See Shawyer's equations for dynamic operation:
http://www.emdrive.com/theorypaper9-4.pdf

Apologies if my explanations fails to convey how EMDrive works different to expelled mass rocket engine. Suggest need to stop comparing to conventional rocket engine and focus on overall primary energy input to final accelerating mass kinetic energy gain.

Actually he seems to be claiming that there is no constant acceleration with constant power input. If so then there may be no COE violation but we are back to the problem of a preferred frame of reference. And your ship will preform very differently in December than in June because of the orbit of the earth putting it in a different inertial reference frame.

Offline Ghozer

Has anyone thought simply on this?

It could be that the microwaves are causing miniature quantum explosions and what we're seeing with the interference of the lasers is a bubble created by the explosion (like a shockwave)

it's this quantum bubble that is causing the space around the bubble to alter - (displacement) and thus causing a quantum ripple of some sort..

What if it's like water - but an un-compressible quantum liquid?

I have always thought of space like a quantum liquid! :)

Forgive me but i'm no scientist or student have no qualifications or training in thermal dynamics, particle physics, or anything - i'm just a really interested person who has lots of thoughts and ideas - I could be way off the mark - but at least I have (now) found a place I can talk and discuss them :D
« Last Edit: 05/01/2015 06:17 PM by Ghozer »

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