• sanman
In summary, the Woodward Effect is an idea for using relativistic motion to impart more momentum to a system.
sanman
Mach Thruster: The Woodward Effect?

Okay, here's a different idea for "propellant-less" propulsion:

It's based on some idea by a University of California physicist named James Woodward, who himself preferred to use the term "Mach Effect"

http://en.wikipedia.org/wiki/Woodward_effect

Basically, his idea was that if you have mass moving at relativistic velocity inside another mass, then the internal moving mass can make itself heavier or lighter depending on how fast it's moving.

So then if you make the overall system oscillate (surrounding mass), and you time the movements of the inner mass with the oscillations, then you can selectively impart more momentum in one part of the oscillation than in another, for the overall system. This would create a net change in momentum for the system.

Did anybody catch what I said there?

Hmm, this one has me scratching my head.So where did the extra mass/momentum on demand come from? Well, it came from the relativistic motion of the inner mass. You can switch that motion on or off, depending on which way your overall mass-system is oscillating. If momentum is to be conserved, then where did the difference in momentum go? It went to, umm, space? It went to whatever it is that retards the motion of a relativistically-moving mass. The universe?

Hmm, tell me, if I lift up a cyclotron that's whirling particles around at extremely high speed, will it feel heavier to me than if I lifted it up while it was turned off?
Does anybody see what I'm saying here?

In that sense, is a relativistically-moving mass really a closed system? Or is it somehow interacting with space itself, where space itself can't really be described as closed?

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Edit: I overlooked something really simple when I wrote this. See #5 for more information.

I'm pretty sure the total momentum of the inner mass must be 0, at least when you average it over time. Imagine a propeller rotating in a box with a vacuum in it. (In this case you don't need to average over time, but if you instead imagine a ball bouncing between the side walls of the spaceship, perpendicular to the direction of the ship's motion, then you have to).

You obviously need an energy source to change the speed of the propeller. This energy source is what contributes additional (relativistic) mass to it. The energy source should be located towards the front of the ship, because that will give the ship another push forward every time that energy is transferred to the propeller to speed it up. (Even if the energy source absorbs energy from the propeller when it slows it down, it will always be a smaller amount because of energy loss in the form of heat).

Now push the box with the propeller in it towards the back of the ship when the speed/mass is high, and push it back when the speed/mass is low. The ship will be pushed forward, and then backward, but the forward push is bigger.

It sounds like it should work in principle, but it also sounds like it would be the slowest spaceship ever, kind of like a spaceship with a battery-powered flashlight instead of a rocket engine.

And yes, your cyclotron will feel heavier when the particles inside it are moving around fast. Even if you just heat something up, it will make it heavier.

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So are inertial mass and gravitational mass always the same?

If you have 2 bodies both moving together at some relativistic velocity, will their gravitational pull on each other be greater than if they were both at rest?

There are several threads that deal specifically with that question, and there are people here who have spent a lot of time thinking of good answers for those threads, so I'll leave this one to them. (I would have to do some thinking to give you a good answer, and I don't have time for that right now. I think the short answer to the second question is no).

Fredrik said:
It sounds like it should work
I have changed my mind. Either I have misunderstood what this "effect" is supposed to do, or it can't possibly work. It's pretty obvious really. Nothing ever leaves the ship, so if the ship moves forward, momentum isn't conserved.

OK, I read a few lines in one of his articles, and he claims that Mach's principle implies that the rest mass of an accelerating object will change. So this is not about relativistic mass at all.

I haven't tried to understand the argument, but there are references in here (a pdf file) to other articles that present the argument.

After reading the patent and some of the other material, in particular the paper "MACH’S PRINCIPLE, MASS FLUCTUATIONS, AND RAPID SPACETIME TRANSPORT" linked from Woodward's web site, I'm extremely sceptical.

In Special Relativity, all four components of four-momentum (that is, energy and linear momentum) are locally conserved at the microscopic level, with an equation of continuity. This also applies locally within GR, and is thought to apply on a larger scale too although there is some difficulty in describing this in GR because gravitational energy cannot be localized in a unique way.

It is certainly true that local conservation rules do NOT apply to rest mass, but Newton's law applies to total energy rather than rest mass, so this isn't relevant.

What may not be immediately clear is that this means that if energy is supplied to something by any means, regardless of whether it is via wires, pipes, axles, fields or whatever, then any change in energy or momentum must flow through that route.

For example, if you look up "dipole gravity" you'll find that many years ago Eue Jin Jeong had an idea that if you spin up a hemispherical object around its axis of symmetry, you will shift the center of mass slightly along the axis because of relativistic considerations. (This can be better illustrated by considering an axle with two wheels on it of the same mass but different radii, so one gets more rotational kinetic energy than the other as the rotation rate increases). It is true that the center of mass of the system shifts, but if you use Special Relativity to analyze the details of how the torque is applied through the axis, you will find that if the assembly were free to slide along its axis, it would shift to keep the center of mass in the same place, and a force has to be applied to prevent that from happening, so there is no overall shift of the center of mass. (However, Eue Jin Jeong has ignored this analysis and is now apparently trying to profit from this idea).

Similarly, I think Woodward must be ignoring some part of the energy or momentum flow to achieve his result. For example, it appears that he thinks that there is a loophole related to dm/dt terms in Newton's law. However, this isn't relevant, because the microscopic conservation of four-momentum is exact, and even if the calculations in difficult cases involve extra terms, these cancel out when you consider the flow of energy from one described system to another.

Similar ideas relating to unbalanced forces in sufficiently complex systems such as gyroscopes have been presented many times before (such as in the "Dean Drive" and ideas from Eric Laithwaite). In each case, a complex calculation appears to show unbalanced terms. However, as four-momentum is locally conserved, any such effect must be due to an incomplete or incorrect calculation, even if it is very difficult to find a specific error.

This means that if there is any possibility of some propellantless drive, it cannot arise from combining existing physical effects in a new complicated way, as all of those physical effects are known to be subject to the local conservation rules. It can only arise from new physics.

sanman said:
It's based on some idea by a University of California physicist named James Woodward, who himself preferred to use the term "Mach Effect"

Actually, he's a historian.

Fredrik said:
It's pretty obvious really. Nothing ever leaves the ship, so if the ship moves forward, momentum isn't conserved.

Woodward would argue that momentum is conserved because the entire rest of the universe is being kicked backwards.

Woodward would argue that momentum is conserved because the entire rest of the universe is being kicked backwards.

That's not the way in which momentum and energy are conserved. Momentum components and energy are like a fluid which cannot be created or destroyed but can flow from place to place. There can't be any gaps in between. We sometimes use "action at a distance" models, for example when describing electromagnetic interactions, but these are just a simplification; a more accurate model would show that the energy flows through the field, and that flowing energy has momentum.

It would be more acceptable to talk about the rest of the universe being kicked backwards if some form of energy and momentum transfer were clearly taking place. A propellant doesn't need to be a material solid; it is possible to propel something by emitting a beam of electromagnetic radiation, and it might even be theoretically possible to do so by emitting a beam of gravitational radiation (I don't know about that one). However, some form of energy has to flow to create a reaction.

Jonathan Scott said:
That's not the way in which momentum and energy are conserved.

Of course not. Like I said, that's his argument.

The problem, apart from the fact that Woodward's calculation is Just Plain Wrong (it takes the same momentum to stop a the mass that it did to get it going in the first place) is that momentum is conserved locally as well as globally. I can't move the momentum to the "rest of the universe" without applying a force.

I suggest reading this long thread at NSF Forums, in special for the many posts by GI-Thruster and Star-Drive (Paul March), both involved at ME-Effect experiments and with Woodward.
http://forum.nasaspaceflight.com/index.php?topic=13020.75

Its worth reading, and they explain it all very carefully.I suggest starting at page 6, with the first post by GI-Thruster. When Star Drive starts posting however, is when things get interesting.

He actually spammed the physics department student emails awhile back. So I can comment on some of this.

1) His theory requires non-local interactions (is not compatible with SR and causality)
2) The "mach" comes from his theory claiming mass is due to the interactions with the rest of the universe (including interactions propagating back in time)

So, in my opinion, if you want to use this for propulsion, you can pretty safely ignore it.
If you are interested in it more for theoretical reasons, you can safely ignore it, unless you are okay with accepting all of the above. Since I doubt that is the case, I'm not going to bother commenting further.

sanman said:
If you have 2 bodies both moving together at some relativistic velocity, will their gravitational pull on each other be greater than if they were both at rest?

The short answer is no. The mutual gravitational pull will be less, if the two bodies are moving relative to the observer. To an observer co-moving with the two bodies, the mutual gravitational pull will be the same. This is simple application of SR. If the two bodies moved towards each other faster as you suggest, this would provide a method to detect absolute motion and this would violate SR.

have you read the above thread from Nasa Spaceflight and the explanations provided by Paul March?

CuriousKid said:
He actually spammed the physics department student emails awhile back. So I can comment on some of this.

1) His theory requires non-local interactions (is not compatible with SR and causality)
2) The "mach" comes from his theory claiming mass is due to the interactions with the rest of the universe (including interactions propagating back in time)

So, in my opinion, if you want to use this for propulsion, you can pretty safely ignore it.
If you are interested in it more for theoretical reasons, you can safely ignore it, unless you are okay with accepting all of the above. Since I doubt that is the case, I'm not going to bother commenting further.

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The idea is that a the mass of the piezoelectric material changes with the square of the rate of change of the energy in the material. You can even make the mass go negative.

Note: This is a violation of conservation of energy. You can lift an arbitrarily large mass upwards in a gravitational field with an arbitrarily small amount of energy, as only the square of the change in energy wrt time causes the mass change. One can then remove the changing energy that is applied to the capacitor and "drop" the mass (say, with a string on a generator) and obtain a net positive energy output.

To test this effect of mass change, in 2009 I put a piezoelectric capacitor on a tuning fork and applied a voltage at the resonate frequency of the tuning fork + capacitor device. This would amplify the expected magnitude of the Woodward effect so it could be measured. The experimental design was such that I expected to see the fork vibrate if a changing mass was affected by gravity on the fork. I measured the amplitude of the tuning fork with an inductive sensor and I had worked out the parameters of the fork so I could tell with 2 digit precision what the driving force (the mass change under the force of gravity) was. A "naive" application of the Woodward equation would have been detected, tho' it was argued that the Woodward equation was a difference equation and I was doing it wrong.

After accounting for the piezoelectric effect itself and for effects of the Earth's magnetic field by nulling them out, I could measure no change in mass of the capacitor.

I found no mass change. Zippo. Nada. Zilch.

This experiment was done for my master's project under the Guidance of Dr. John G. Cramer at the University of Washington. We did not publish because I more tests were required for verification of the null result. As Dr. Cramer was retiring and I was graduating, I didn't do more testing.

I would note that there is a math error in the derivation of the Woodward effect's theory. If one uses Sciama's result of (Phi+phi)/c^2 = -1/G, one cannot treat the speed of light as a constant and phi as a variable.

This experimental result could be disputed by noting that I was checking for a gravitational mass change and not an inertial mass change. The original experimental design (aka "Mach Guitar") checked for an inertial mass change. However, the original experiment couldn't be done as the mass of the capacitor significantly changed the resonate frequency of the Mach Guitar. I mathematically studied the experiment, and found that I needed a guitar "string" as thick as a tuning fork tine.

This experiment was difficult to construct. I had planned on repeating the experiment to do a statistical study of the results, and to try driving the fork to see if I could detect a change in INERTIAL mass, but personal issues and a lack of a High voltage amplifier prevented me from proceeding. I also was fairly confident in my initial result, and felt it was a bit like beating a dead horse.

Redbelly98 said:
(7/22/11) Moderator's note: this thread is now opened, after having been locked.

It has been brought to our attention that the subject has been published in a peer-reviewed journal:

The following paper contains the derivation of the Mach effect

Why does peer review make a difference between locked or unlocked?

Steve Lajoie said:
Why does peer review make a difference between locked or unlocked?

Click the "Rules" link at the top of any page here and read the section Overly Speculative Posts.

Hi Steve,

Thanks for your great response. Regarding your experiment using a tuning fork resonator, just today I was reading about a novel experiment recently done with a nanomechanical resonator:

http://www.nature.com/nature/journal/v480/n7377/full/nature10628.html

Is it conceivable that an experiment like yours could be re-done at a finer level of precision using a nanomechanical resonator similar to this one?

Just wondering.

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regarding Steve´s post, here is GiThruster´s (who is part of Woodward´s mail list and performs a few experiments himself), posted at Talk Polywell forum:

*******************************************

GIThruster said:
The idea is that a the mass of the piezoelectric material changes with the square of the rate of change of the energy in the material. You can even make the mass go negative.

Note: This is a violation of conservation of energy. You can lift an arbitrarily large mass upwards in a gravitational field with an arbitrarily small amount of energy, as only the square of the change in energy wrt time causes the mass change. One can then remove the changing energy that is applied to the capacitor and "drop" the mass (say, with a string on a generator) and obtain a net positive energy output.

To test this effect of mass change, in 2009 I put a piezoelectric capacitor on a tuning fork and applied a voltage at the resonate frequency of the tuning fork + capacitor device. This would amplify the expected magnitude of the Woodward effect so it could be measured. The experimental design was such that I expected to see the fork vibrate if a changing mass was affected by gravity on the fork. I measured the amplitude of the tuning fork with an inductive sensor and I had worked out the parameters of the fork so I could tell with 2 digit precision what the driving force (the mass change under the force of gravity) was. A "naive" application of the Woodward equation would have been detected, tho' it was argued that the Woodward equation was a difference equation and I was doing it wrong.

After accounting for the piezoelectric effect itself and for effects of the Earth's magnetic field by nulling them out, I could measure no change in mass of the capacitor.

I found no mass change. Zippo. Nada. Zilch.

This experiment was done for my master's project under the Guidance of Dr. John G. Cramer at the University of Washington. We did not publish because I more tests were required for verification of the null result. As Dr. Cramer was retiring and I was graduating, I didn't do more testing.

I would note that there is a math error in the derivation of the Woodward effect's theory. If one uses Sciama's result of (Phi+phi)/c^2 = -1/G, one cannot treat the speed of light as a constant and phi as a variable.

This experimental result could be disputed by noting that I was checking for a gravitational mass change and not an inertial mass change. The original experimental design (aka "Mach Guitar") checked for an inertial mass change. However, the original experiment couldn't be done as the mass of the capacitor significantly changed the resonate frequency of the Mach Guitar. I mathematically studied the experiment, and found that I needed a guitar "string" as thick as a tuning fork tine.

This experiment was difficult to construct. I had planned on repeating the experiment to do a statistical study of the results, and to try driving the fork to see if I could detect a change in INERTIAL mass, but personal issues and a lack of a High voltage amplifier prevented me from proceeding. I also was fairly confident in my initial result, and felt it was a bit like beating a dead horse.

With criticisms like this, one wants to be fair, so let's start by recognizing that whomever wrote this, was certainly NOT current on M-E theory as of 2009. At least, this is how I would understand the handful of factual and conceptual errors involved that I'd like to correct.

The idea is that a the mass of the piezoelectric material changes with the square of the rate of change of the energy in the material. You can even make the mass go negative
This is part of the idea. The change in energy must be accompanied by a simultaneous acceleration relative to the distant stars to yield a Mach-Effect (ME) or transient mass fluctuation. It appears the writer does not currently appreciate this though, the piezo action in the ceramic could have been used to generate this acceleration, but we can't tell from the description of the experiment.

Note: This is a violation of conservation of energy. You can lift an arbitrarily large mass upwards in a gravitational field with an arbitrarily small amount of energy, as only the square of the change in energy wrt time causes the mass change.
This is a factual/conceptual error caused by the writer's neglect to account for the gravinertial contribution into the M-E device. Electricity is not the only form of energy in, and he has here failed to account for the fact the M-E device is a gravinertial transistor, not a transducer.

To test this effect of mass change, in 2009 I put a piezoelectric capacitor on a tuning fork and applied a voltage at the resonate frequency of the tuning fork + capacitor device. This would amplify the expected magnitude of the Woodward effect so it could be measured. The experimental design was such that I expected to see the fork vibrate if a changing mass was affected by gravity on the fork.
I trust rather than "amplify", what the writer here means is "transduce" the change in mass into a change in position that is then measured. If this accurately describes the experimental design this is a very poor design. First of all, the mass fluctuation is not equal in the positive and negative fluctuation--the negative fluctuation will always be larger, so one cannot hope to get sinusoidal motion in this way. The experiment is trying to cause the tuning fork to resonate, but it cannot resonate because it has different masses at different times. Poor conceptual design is probably the reason this experiment yielded a null result.

The experimental design was such that I expected to see the fork vibrate if a changing mass was affected by gravity on the fork. I measured the amplitude of the tuning fork with an inductive sensor and I had worked out the parameters of the fork so I could tell with 2 digit precision what the driving force (the mass change under the force of gravity) was.
Can't tell what "two digit precision" is but presuming this is percent of the unfluctuated mass, and that the experimenter was correct concerning what portion of the cap should be considered "active mass", given sufficient mass fluctuation one would hope you'd see it, were the motion sinusoidal.

A "naive" application of the Woodward equation would have been detected, tho' it was argued that the Woodward equation was a difference equation and I was doing it wrong.
Em, "it can be argued"? Is this serious? Is the experimenter claiming he doesn't know whether the experiment ought to work or not?

I would note that there is a math error in the derivation of the Woodward effect's theory. If one uses Sciama's result of (Phi+phi)/c^2 = -1/G, one cannot treat the speed of light as a constant and phi as a variable.
No. There is no error in the equation. If there were, the experimenter ought to have brought this to the attention of Woodward and this should have been dealt with through peer review, since the equation has passed peer review. Stating the equation is wrong AFTER an experiment hasn't worked and without handling the issue properly is not what ought to be acceptable in order to earn a degree. I will note that the writer apparently does not understand the difference between a "constant" and an "invariable" because he has not been trained in advanced field theory, and should not be indulging in critiquing physics he does not understand. the proper course was certainly to go to Woodward through Cramer and get this sorted out by those who can do the physics.

This experimental result could be disputed by noting that I was checking for a gravitational mass change and not an inertial mass change.
No really, it cannot. Woodward's theory relies upon EEP or Einstein's Equivalence Principle in its strong form, and asserts that there can be no way to ever tell the difference between gravitational and inertial mass. Anyone handling the theory ought to know this.

IMHO, since the experimenter did not complete the experiment, and claims he did not verify his own results, I am at odds to see not only how he is making any judgements about a "dead horse" but likewise, how he was awarded his masters. Sounds like he deserved an "incomplete".

If indeed the experiment was not performed sufficient to validate its own test results, there is no reason to presume it was performed correctly. I have dozens of questions in this regard. For instance, since the experimenter betrays no understanding of the need for bulk acceleration relative to the distant stars, I would first want to look at how the ceramic's piezo-action was set up on the tuning fork. Does the ceramic form a quarter wave or half wave resonator? If it is not set up to maximize displacement of the ceramic, the ceramic is not going to produce the required acceleration necessary to generate M-E. This, accompanied by several dozen other issues is reason enough to understand a null result.

In short, I see three reasons this setup as I understand it would not work. First is that the ceramic is not attached to a reaction mass that will force the ceramic to accelerate in one direction. Rather the opposite. Since the fork is intended to displace, the accelerations will likely be minimal and sum to zero. Second, if there were a mass fluctuation, because it is not sinusoidal and not equal in its positive and negative extensions, it would not be in phase with the natural resonance of any connected resonator. Third, since the experimenter doesn't demonstrate an understanding for the need for bulk acceleration, one wants to ask what sort of ceramic he used. Was it sintered to repress or enhance the piezo-action of the material? Woodward's own work from just 5 years ago neglected this issue, and the caps he chose were sintered to repress rather than enhance. Now we all know better, so just how old was this experiment and what sort of materials were used?

Given the need for bulk acceleration relative to the distant stars was extremely well understood by 2007, and this experimenter did his experiment in 2009, it reflects very poorly on the experimenter that he did not do a sufficient literature review before designing the experiment.

So in summary, it appears to me the experimenter did not understand his own experiment very well, did not complete his experiment, and did not publish his experiment because of these things. So why is he now writing about it in a public forum?

Final note is to wonder why this masters student was completely ignorant of the rotator work done in 2008, on precisely the same topic, that demonstrated conclusively the existence of M-E. Had the student done a literature review of the field, he would no doubt have designed around the need for bulk acceleration and he did not. In fact, had he been aware of the work at that time, he would no doubt have designed a replication of the rotator, which clearly demonstrated unrectified M-E in just the same way as he was after. Instead, he designed an experiment that cannot work because it does not provide for bulk acceleration.

I'd just like to point one last thing out as regards this uninformed experiment done at University of Washington for a Masters degree. It has always been understood that acceleration relative to the distant stars is a necessary requirement in order to generate M-E. Back during the MLT days, the need for this to be "bulk", meaning to include the entire ceramic and not just the mobile ion in the perovskite materials used, was not fully appreciated. since 2008 it has been understood conclusively especially as expressed by the "bulk acceleration conjecture" that the entire ceramic needs to undergo this acceleration. In the experiment mentioned, there is apparently no understanding whatsoever of the need for any sort of acceleration. I cannot understand how any experimenter could not understand the necessary requirements to produce the effect he was after.
---------------------------------------------------------------------------------

Paul March answered to that last remark by GiThruster with the following:

GIThruster & Aceshigh:

A clarification: Woodward's SPESIF-2011 Stargate paper not only requires bulk acceleration relative to the distant stars of the energy storing dielectric to express the M-E, but also requires bulk acceleration in the vector direction of the applied E-field in the dP/dt energy storing dielectric. In other words, the M-E's predicted transient mass fluctuations can only be expressed under a very specific set of circumstances, (dv/dt & dv/dt direction, dP/dt and wave-front phasing), and if one does not supply ALL of these elements concurrently and in concert with each other, the expected M-E mass transient signal will NOT be expressed. And that assumes you are using a rotary experiment such as Woodward used in the 2008/2009 time period as GIThruster already noted. If you are trying to detect a unidirectional force from an M-E based thruster system as your M-E proof of principle test, the requirements list needed for success just got a lot longer than just using the rotary based experiments.

BTW, running any of these types of M-E experiments at hundreds or even thousands of Hz frequencies is just plain asking for failure due to the very small predicted mass fluctuations/forces generated at these low operating frequencies, dependent on the applied bulk acceleration & direction. Only Woodward’s attention to detail in his 2008/2009 rotary experiment and the application of up to 800 gees of bulk acceleration allowed him to demonstrate the M-E at his chosen operating frequency of 40.0 kHz. And that was only after he found out that the mundane voltage squared (V^2) electrostrictive signal also generated by the Y5U ceramic used in the experiment actually drives the generation of the M-E signal. The devil IS in the details…

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## 1. What is the Woodward Effect?

The Woodward Effect is a controversial theory proposed by physicist James F. Woodward that suggests the possibility of creating a propellantless propulsion system using a combination of electrical and gravitational forces.

## 2. How does the Woodward Effect work?

The theory proposes that by applying a strong electric field to a mass, the mass will experience a reduction in gravitational mass and an increase in inertial mass. This difference in mass would result in a force that could potentially propel the mass in a specific direction.

## 3. Has the Woodward Effect been tested?

There have been several attempts to test the Woodward Effect, but the results have been inconclusive and have not been replicated by other scientists. Many in the scientific community remain skeptical of its feasibility.

## 4. What are the potential applications of the Woodward Effect?

If the Woodward Effect were to be proven and harnessed, it could potentially revolutionize space travel by allowing spacecraft to travel at faster speeds without the need for traditional propellant systems. It could also have applications in other industries, such as transportation and energy production.

## 5. What are the challenges and criticisms of the Woodward Effect?

Some of the main challenges and criticisms of the Woodward Effect include the lack of reproducible results, the lack of a comprehensive theoretical framework, and the violation of established laws of physics. Additionally, the proposed mechanism for the effect has not been fully understood and tested, making it difficult to verify its validity.

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