More EM Drive Stuff

The Rocketry Forum

Help Support The Rocketry Forum:

BuiltFromTrash

Well-Known Member
Joined
Aug 7, 2014
Messages
305
Reaction score
2
This too: [video=youtube;JGcvxg7jJTs]https://www.youtube.com/watch?v=JGcvxg7jJTs[/video]
 

vcp

Well-Known Member
TRF Supporter
Joined
Jan 28, 2009
Messages
1,202
Reaction score
257
Location
Meridian, ID
Interesting note: This EM drive was described almost exactly in the 1980 juvenile SF novel 'Star Driver' by Lee Correy (G. Harry Stine).
 

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
261
Some people, smarter than me, have pointed out that the EM drive, if it worked as described, would make it very easy to create a perpetual motion machine. Just attach it to the outside of a wheel. Connect it up to a power source and run it until the wheel is turning fast enough to power a generator and produce enough electricity to run the EM drive. Then replace the power source with the generator.

The wheel will continue to accelerate, producing enough energy to overcome losses in the system. Then you can begin drawing energy from it. Free electricity for everyone!

-- Roger
 

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
7,157
Reaction score
1,570
Some people, smarter than me, have pointed out that the EM drive, if it worked as described, would make it very easy to create a perpetual motion machine. Just attach it to the outside of a wheel. Connect it up to a power source and run it until the wheel is turning fast enough to power a generator and produce enough electricity to run the EM drive. Then replace the power source with the generator.

The wheel will continue to accelerate, producing enough energy to overcome losses in the system. Then you can begin drawing energy from it. Free electricity for everyone!
If I'm reading the scale right, they're pumping in megawatts and measuring micronewtons. That's not to say the measured force is what it's hoped to be, but it's certainly not a perpetual motion machine.
 

dixontj93060

Well-Known Member
Joined
Feb 20, 2009
Messages
13,083
Reaction score
24
If I'm reading the scale right, they're pumping in megawatts and measuring micronewtons. That's not to say the measured force is what it's hoped to be, but it's certainly not a perpetual motion machine.
I don't think claims of perpetual motion have been made. The advantage in the EM Drive is that it doesn't require stored fuel.
 

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
261
I don't think claims of perpetual motion have been made. The advantage in the EM Drive is that it doesn't require stored fuel.
The point is, that if the EM Drive really worked, it could be used to create a perpetual motion machine. That's a good reason to believe that it doesn't work.

-- Roger
 

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
261
If I'm reading the scale right, they're pumping in megawatts and measuring micronewtons.
Since the claim is that it wouldn't loose mass, it would still be able to build up momentum to the point where it could eventually power itself regardless of how inefficient it is.

--Roger
 

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
7,157
Reaction score
1,570
Since the claim is that it wouldn't loose mass, it would still be able to build up momentum to the point where it could eventually power itself regardless of how inefficient it is.
Taking power off of it would be drag, and it would slow. Megawatts for micronewtons is not perpetual motion or free energy.

I look forward to their results, whatever they are.
 

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
261
Taking power off of it would be drag, and it would slow. Megawatts for micronewtons is not perpetual motion or free energy.
I didn't say that you would disconnect the power. I said that, at some point, you could hook the EM Drive-powered wheel to a generator to generate the power. If it really produces thrust without giving up mass, then it doesn't matter that a lot of energy is required to produce little motion. As long as it continues to accelerate it would build up momentum. Eventually it would reach a point where it would have enough momentum to generate enough power to continue to accelerate. At that point, just hook the wheel up to a generator to supply its own power and it becomes a perpetual motion machine.
 
Last edited:

dhbarr

Amateur Professional
Joined
Jan 30, 2016
Messages
7,157
Reaction score
1,570
I didn't say that you would disconnect the power. I said that, at some point, you could hook the EM Drive-powered wheel to a generator to generate the power. If it really produces thrust without giving up mass, then it doesn't matter that a lot of energy is required to produce little motion. As long as it continues to accelerate it would build up momentum. Eventually it would reach a point where it would have enough momentum to generate enough power to continue to accelerate. At that point, just hook the wheel up to a generator to supply its own power and it becomes a perpetual motion machine.
There is no amount of momentum in the universe that can generate kW of energy without inducing more micronewtons of drag than have been measured as thrust from these types of drives.
 

Incongruent

Well-Known Member
Joined
Oct 25, 2016
Messages
1,735
Reaction score
5
I didn't say that you would disconnect the power. I said that, at some point, you could hook the EM Drive-powered wheel to a generator to generate the power. If it really produces thrust without giving up mass, then it doesn't matter that a lot of energy is required to produce little motion. As long as it continues to accelerate it would build up momentum. Eventually it would reach a point where it would have enough momentum to generate enough power to continue to accelerate. At that point, just hook the wheel up to a generator to supply its own power and it becomes a perpetual motion machine.
Moving the electrons in a generator uses energy. So the wheel would not continue accelerate because the resisting force from the induction would overcome the push by the EM drive.
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,641
Reaction score
1,262
I'm very skeptical of the EM drive. I think it violates too many theories that are considered fundamental to physics. But I'm open to proof. The real proof will be to remove it from the lab and fly it in space. If it works, it works, and there will be a lot of careers devoted to figuring out why. I think there actually is a plan to put an EM drive in space for testing pretty soon. It'll be interesting to see what happens!
 

Incongruent

Well-Known Member
Joined
Oct 25, 2016
Messages
1,735
Reaction score
5
Using the EM drive for angular momentum would be wasteful. The EM drive uses the energy of the photons expelled as mass and uses that to push itself forward. (Basically a rocket that makes it's own fuely) This, as Einstein would have us know, create a minuscule amount mass for the energy needed, but in space, where energy (solar radiation) is plentiful, it works. To create angular momentum, it would be much more efficient to have a typical electric motor.

At least, that's my understanding of it. I could (very likely) be wrong.
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,641
Reaction score
1,262
I remember reading that one of the paradoxes of a reactionless thruster IS the possibility of perpetual motion type machines. I don't remember the explanation well enough to explain it here.
 

Incongruent

Well-Known Member
Joined
Oct 25, 2016
Messages
1,735
Reaction score
5
The self acclaimed "rocket scientists" are getting confused...
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,641
Reaction score
1,262
Using the EM drive for angular momentum would be wasteful. The EM drive uses the energy of the photons expelled as mass and uses that to push itself forward. (Basically a rocket that makes it's own fuely) This, as Einstein would have us know, create a minuscule amount mass for the energy needed, but in space, where energy (solar radiation) is plentiful, it works. To create angular momentum, it would be much more efficient to have a typical electric motor.

At least, that's my understanding of it. I could (very likely) be wrong.
Actually, the EM drive does not expel photons to create the thrust. That's why it is considered impossible by mainstream physics. The microwaves are supposed to reflect around inside the chamber and NOT be expelled, and yet the drive is still supposed to create thrust. If photons are being expelled by the EM drive, then that's a photon drive, and that's a well-understood phenomenon and is consistent with mainstream physics. Nothing revolutionary about that. The revolutionary thing about the EM drive is that it's supposed to create action WITHOUT an equal and opposite reaction, and that is very irritating to Newron.
 
Last edited:

jadebox

Roger Smith
TRF Sponsor
Joined
Jan 18, 2009
Messages
5,753
Reaction score
261
Moving the electrons in a generator uses energy. So the wheel would not continue accelerate because the resisting force from the induction would overcome the push by the EM drive.
No. You're forgetting that the EM Drive is reactionless. The rotating wheel can eventually reach a point where its momentum is great enough to allow the generator to generate enough power to overcome all of the losses in the system and still continue to accelerate the wheel. That's one of the problems that you run into when you start violating the laws of physics. :)

Another way to think about it ... if you set a wheel spinning in space, Newton's First Law says that it will continue to spin at the same speed. If the generator hooked up to the wheel provides enough energy to allow the EM Drive to produce any thrust at all, the wheel will continue to speed up. So, the wheel will always speed up regardless of losses in the generator.

Granted, there is no way to hook a generator up to the wheel in space and have it generate electricity. But, even a real-world example would work if you just waited until the wheel was spinning fast enough to generate enough power to overcome the losses in the system. At that time you could hook up the generator and make Newton cry.

-- Roger
 
Last edited:

Incongruent

Well-Known Member
Joined
Oct 25, 2016
Messages
1,735
Reaction score
5
Actually, the EM drive does not expel photons to create the thrust. That's why it is considered impossible by mainstream physics. The microwaves are supposed to reflect around inside the chamber and NOT be expelled, and yet the drive is still supposed to create thrust. If photons are being expelled by the EM drive, then that's a photon drive, and that's a well-understood phenomenon and is consistent with mainstream physics. Nothing revolutionary about that. The revolutionary thing about the EM drive is that it's supposed to create action WITHOUT an equal and opposite reaction, and that is very irritating to Newron.
Whoops. Thinking of the wrong thing.
 

Incongruent

Well-Known Member
Joined
Oct 25, 2016
Messages
1,735
Reaction score
5
The thrust is attributed to an imbalance of radiation pressure from the bouncing photons and/or experimental error.

While I won't pretend to fathom how that happens, I don't think it can become a perpetual motion machine because no material is a perfect mirror- reflecting photons always impart some of their energy into the reflective surface, which heats up. Since photons move so quickly, they lose all their energy nearly instantaneously and so can't accumulate.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
5,064
Reaction score
2,325
Location
Melbourne Australia
If the generator hooked up to the wheel provides enough energy to allow the EM Drive to produce any thrust at all, then the wheel will continue to speed up. So, the wheel will always speed up regardless of losses in the generator.
A wheel spinning due to inertia will keep spinning. As soon as you draw energy from it (from the generator you attached) it will slow down. If the system is efficient it will take a long time to stop. If it is inefficient it will stop quite quickly. The EM drive is not particularly efficient, but either way the wheel will stop.

I have been following the EM drive for years. It is interesting they call it a reactionless drive. It must be getting traction on something. My physics is not quite at that level to get a good handle on it. Physics keeps evolving as we discover new things. Yay!
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,641
Reaction score
1,262
The thrust is attributed to an imbalance of radiation pressure from the bouncing photons and/or experimental error.

While I won't pretend to fathom how that happens, I don't think it can become a perpetual motion machine because no material is a perfect mirror- reflecting photons always impart some of their energy into the reflective surface, which heats up. Since photons move so quickly, they lose all their energy nearly instantaneously and so can't accumulate.
The thing that contradicts normal physics is the idea that there is an imbalance in radiation pressure INSIDE the sealed vessel, and that imparts thrust on the system. There can't really be an imbalance inside the closed system. That would be like making a car go by sitting in the driver's seat and pushing really hard on the steering wheel. The pressure on the steering wheel is balanced by the pressure on the seat back, so the car won't move, no matter how hard you push. One claim for the EM drive is that the shape of the vessel creates an imbalance, and that is the claim that contradicts Newtons laws.

Another possible explanation is that somehow the EM drive is pushing on the vacuum or some kind of medium of space. That idea has its own set of problems.

The most likely explanation is that the EM drive actually does NOT work, and none of the paradoxes and contradictions actually are happening. The thrust measured is probably an error, or is explained by a flaw in the experiment.
 

OverTheTop

Well-Known Member
TRF Supporter
Joined
Jul 10, 2007
Messages
5,064
Reaction score
2,325
Location
Melbourne Australia
It is really high-end physics that drive it, and my knowledge there is limited so I won't start to defend it. Many people are skeptical of it, and to question it is good. I think it has substance and will be shown to be correct. People keep building them (including NASA I believe) and getting measurable, consistent results. Evidence is building in its favour.

It is likely to involve quantum physics which messes with many peoples' minds, including mine. Discounting the theory based on Newtonian physics alone is misguided, and a little 18th century.

Albert Einstein and Niels Bohr had an argument that ran for about 23 years IIRC. Niels Bohr was pro quantum mechanics, Einstein was anti. Bohr won. Clever people can still be behind the times.
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,641
Reaction score
1,262
It is really high-end physics that drive it, and my knowledge there is limited so I won't start to defend it. Many people are skeptical of it, and to question it is good. I think it has substance and will be shown to be correct. People keep building them (including NASA I believe) and getting measurable, consistent results. Evidence is building in its favour.

It is likely to involve quantum physics which messes with many peoples' minds, including mine. Discounting the theory based on Newtonian physics alone is misguided, and a little 18th century.

Albert Einstein and Niels Bohr had an argument that ran for about 23 years IIRC. Niels Bohr was pro quantum mechanics, Einstein was anti. Bohr won. Clever people can still be behind the times.
I'm keeping an open mind and looking forward to more experiments. One thing I really do not think is correct is the idea of differential radiation pressure. But I am open to the idea that the drive is actually getting traction on something in the quantum realm. I think it's unlikely, but not impossible. If it is pushing on space itself or some kind of quantum medium that permeates space, then that would be an amazing discovery, and who knows what kind of engineering and technology it could lead to.
 

Incongruent

Well-Known Member
Joined
Oct 25, 2016
Messages
1,735
Reaction score
5
I'm keeping an open mind and looking forward to more experiments. One thing I really do not think is correct is the idea of differential radiation pressure. But I am open to the idea that the drive is actually getting traction on something in the quantum realm. I think it's unlikely, but not impossible. If it is pushing on space itself or some kind of quantum medium that permeates space, then that would be an amazing discovery, and who knows what kind of engineering and technology it could lead to.
Or it could prove our understanding of physics wrong- remember the times when people believed that
"storms were caused
by petty gods
fighting on top of a mountain"?
But then new evidence emerged and a new understanding of the world and universe was created.

Maybe we're still putting the puzzle pieces together wrong.

Whatever the result, I'm excited too.
 

ThirstyBarbarian

Well-Known Member
TRF Supporter
Joined
Feb 11, 2013
Messages
8,641
Reaction score
1,262
Or it could prove our understanding of physics wrong- remember the times when people believed that
"storms were caused
by petty gods
fighting on top of a mountain"?
But then new evidence emerged and a new understanding of the world and universe was created.

Maybe we're still putting the puzzle pieces together wrong.

Whatever the result, I'm excited too.
If it eventually leads to jet packs, then I'm all for it!
 

dixontj93060

Well-Known Member
Joined
Feb 20, 2009
Messages
13,083
Reaction score
24
Or it could prove our understanding of physics wrong- remember the times when people believed that
"storms were caused
by petty gods
fighting on top of a mountain"?
But then new evidence emerged and a new understanding of the world and universe was created.

Maybe we're still putting the puzzle pieces together wrong.

Whatever the result, I'm excited too.
+1. We are puny and know so little (Jas. 4:14)
 

Zebedee

Well-Known Member
Joined
Oct 22, 2013
Messages
709
Reaction score
1
I really want the EM drive to be true and to be a doorway into understanding the universe a bit better, but I'm also skeptical, and probably will remain so until someone builds a test vehicle using it and sends that vehicle out towards the stars.
 
Top