The
Woodward effect, also referred to as a
Mach effect, is part of a hypothesis proposed by
James F. Woodward in 1990.
[1] The hypothesis states that
transient mass fluctuations arise in any object that absorbs
internal energy while undergoing a
proper acceleration. Harnessing this effect could generate a
reactionless thrust, which Woodward and others claim to measure in various experiments.
[2][3] If proven to exist, the Woodward effect could be used in the design of
spacecraft engines of a
field propulsion engine that would not have to expel matter to accelerate. Such an engine, called a Mach effect
thruster (MET) or a Mach Effect Gravitational Assist (MEGA) drive, would be a breakthrough in
space travel.
[4][5] So far, no conclusive proof of the existence of this effect has been presented.
[6] Experiments to confirm and utilize this effect by Woodward and others continue.
[7] The anomalous thrust detected in some
RF resonant cavity thruster (EmDrive/Cannae drive) experiments may be explained by the same type of Mach effect proposed by Woodward.
[8][9][10]
The
Space Studies Institute was selected as part of
NASA's Innovative Advanced Concepts program as a Phase I proposal in April of 2017 for Mach Effect research.
[11][12][13][14]
Mach effects
According
to Woodward, at least three Mach effects are theoretically possible:
vectored impulse thrust, open curvature of spacetime, and closed
curvature of spacetime.
[15]
The first effect, the Woodward effect, is the minimal energy effect
of the hypothesis. The Woodward effect is focused primarily on proving
the hypothesis and providing the basis of a Mach effect impulse
thruster. In the first of three general Mach effects for propulsion or
transport, the Woodward effect is an impulse effect usable for in-orbit
satellite station-keeping, spacecraft reaction control systems, or at
best, thrust within the solar system. The second and third effects are
open and closed spacetime effects. Open curved spacetime effects can be
applied in a field generation system to produce warp fields.
Closed-curve spacetime effects would be part of a field generation
system to generate wormholes.
[citation needed]
The third Mach effect is a closed-curve
spacetime effect or
closed timelike curve called a benign wormhole. Closed-curve space is generally known as a
wormhole or
black hole. Prompted by
Carl Sagan for the scientific basis of wormhole transport in the movie
Contact,
Kip Thorne[16]
developed the theory of benign wormholes. The generation, stability,
and traffic control of transport through a benign wormhole is only
theoretical at present. One difficulty is the requirement for energy
levels approximating a "Jupiter size mass".
Kenneth Nordtvedt showed in 1988 that
gravitomagnetism, which is an effect predicted by
general relativity
but hasn't been observed yet at that time and was even challenged by
the scientific community, is inevitably a real effect because it is a
direct consequence of the gravitational vector potential. He
subsequently shown that the gravitomagnetism interaction (not to be
confused with the
Nordtvedt effect), like inertial
frame dragging and the
Lense–Thirring precession, is typically a Mach effect.
[17]
Hypothesis
Mach's principle
The Woodward effect is based on the relativistic effects theoretically derived from
Mach's principle on
inertia within
general relativity, attributed by
Albert Einstein to
Ernst Mach.
[18]
Mach's Principle is generally defined as "the local inertia frame is
completely determined by the dynamic fields in the Universe."
[19] The conjecture comes from a
thought experiment:
[20]
Ernst Mach (1838–1916) was an Austrian physicist […] contemporary of
Einstein, to whom he suggested a thought experiment: What if there was
only one object in the universe? Mach argued that it could not have a
velocity, because according to the theory of relativity, you need at
least two objects before you can measure their velocity relative to each
other.
Taking this thought experiment a step further, if an object was alone
in the universe, and it had no velocity, it could not have a measurable
mass, because mass varies with velocity.
Mach concluded that inertial mass only exists because the universe
contains multiple objects. When a gyroscope is spinning, it resists
being pushed around because it is interacting with the Earth, the stars,
and distant galaxies. If those objects didn't exist, the gyroscope
would have no inertia.
Einstein was intrigued by this concept, and named it "Mach's principle."
Gravity origin of inertia
A formulation of Mach's principle was first proposed as a vector theory of gravity, modeled on
Maxwell's formalism for
electrodynamics, by
Dennis Sciama in 1953,
[21] who then reformulated it in a
tensor formalism equivalent to general relativity in 1964.
[22]
In this paper, Sciama stated that instantaneous inertial forces in
all accelerating objects are produced by a primordial gravity-based
inertial
radiative field created by distant cosmic matter and propagating both forwards
and backwards in time at light speed:
Inertial forces are exerted by matter, not by absolute space. In this form the principle contains two ideas:
- Inertial forces have a dynamical rather than a kinematical origin,
and so must be derived from a field theory [or possibly an
action-at-a-distance theory in the sense of J.A. Wheeler and R.P.
Feynman…
- The whole of the inertial field must be due to sources, so that in
solving the inertial field equations the boundary conditions must be
chosen appropriately.
— Dennis W. Sciama, in "The Physical Structure of General Relativity", Reviews of Modern Physics (1964).
Sciama's inertial-induction idea has been shown to be correct in Einstein's general relativity for any
Friedmann–Robertson–Walker cosmology.
[23][24]
According to Woodward, the derivation of Mach effects is
relativistically invariant, so the conservation laws are satisfied, and
no "new physics" is involved besides general relativity.
[25]
Gravitational absorber theory
As previously formulated by Sciama, Woodward suggests that the
Wheeler–Feynman absorber theory would be the correct way to understand the action of instantaneous inertial forces in Machian terms.
[26][27][28]
A first image to understand would be filming a sequence where a rock
is thrown in the middle of a pond, making concentric ripples on the
water propagating towards the shore.
Running the sequence backwards (thinking it as seeing events running
backward in time) we then observe concentric waves propagating from the
shore towards the center of the pond, where a rock emerges.
The thing to understand is that advanced waves coming back from the
future never propagate farther into the past than the rock hitting the
water that initiated all of the waves.
— James F. Woodward, in Making Starships and Stargates, Springer 2013, page 49.[15]
The Wheeler-Feynman absorber theory is an interpretation of
electrodynamics that starts from the idea that a solution to the electromagnetic field equations has to be symmetric with respect to
time-inversion, as are the field equations themselves.
[21][29] Wheeler and Feynman showed that the propagating solutions to classical wave equations can either be
retarded (i.e. propagate forward in time) or
advanced (propagate backward in time). The absorber theory has been used to explain
quantum entanglement and led to the
transactional interpretation of quantum mechanics,
[30][31][32] as well as the
Hoyle-Narlikar theory of gravity, a Machian version of Einstein's
general relativity.
[33] Fred Hoyle and
Jayant Narlikar originally developed their cosmological model as a
quasi steady state model
of the universe, adding a "Creation field" generating matter out of
empty space, an hypothesis contradicted by recent observations.
[34]
When the C-field is not used, ignoring the parts regarding mass
creation, the theory is no longer steady state and becomes a Machian
extension of general relativity. This modern development is known as the
Gravitational Absorber Theory.
[35]
As the gravitational absorber theory reduces to general relativity in the limit of a
smooth fluid model of particle distribution,
[36]
both theories make the same predictions. Except in the Machian
approach, a mass changing effect emerges from the general equation of
motion, from which Woodward's transient mass equation can be derived.
[37] A resulting force suitable for Mach effect thrusters can then be calculated.
[38]
While the Hoyle-Narlikar derivation of the Mach effect transient terms is done from a fully
nonlinear,
covariant formulation, it has been shown Woordward's transient mass equation can also be retrieved from
linearized general relativity.
[39][40]
Transient mass fluctuation
The following has been detailed by Woodward in various peer-reviewed papers throughout the last twenty years.
[41][42][43]
According to Woodward, a transient mass fluctuation arises in an
object when it absorbs "internal" energy as it is accelerated. Several
devices could be built to
store internal energy during accelerations. A measurable effect needs to be driven at a high
frequency, so
macroscopic mechanical systems
are out of question since the rate at which their internal energy could
be modified is too limited. The only systems that could run at a high
frequency are
electromagnetic energy storage devices. For fast transient effects,
batteries are ruled out. A magnetic energy storage device like an
inductor using a high-
permeability core material to transfer the
magnetic energy could be especially built. But
capacitors are preferable to inductors because compact devices storing energy at a very high
energy density without
electrical breakdown are readily available. Shielding
electrical interferences are easier than
shielding magnetic ones.
Ferroelectric materials can be used to make high-frequency
electro-mechanical actuators,
and they are themselves capacitors so they can be used for both energy
storage and acceleration. Finally, capacitors are cheap and available in
various configurations. So Mach effect experiments have always relied
on capacitors so far.
When the
dielectric of a capacitor is submitted to a varying
electric power (charge or discharge), Woodward's hypothesis predicts
[43] a transient mass fluctuation arises according to the transient mass equation (TME):
where:
- is the proper mass of the dielectric,
- is the gravitational constant,
- is the speed of light in vacuum,
- is the proper density of the dielectric,
- is the volume of the dielectric,
- is the instantaneous power delivered to the system.
This equation is not the full Woodward equation as seen in the book. There is a third term,
, which Woodward discounts because his
gauge sets
; the derivatives of this quantity must therefore be negligible.
[43]
Propellantless propulsion
The previous equation shows that when the
dielectric material of a
capacitor is cyclically charged then discharged while being accelerated, its
mass density fluctuates, by around plus or minus its
rest mass value. Therefore, a device can be made to
oscillate
either in a linear or orbital path, such that its mass density is
higher while the mass is moving forward, and lower while moving
backward, thus creating an
acceleration of the device in the forward direction, i.e. a thrust. This effect, used repeatedly, does not expel any
particle and thus would represent a type of apparent
propellantless propulsion, which seems to be in contradiction with
Newton's third law of motion. However, Woodward states there is no violation of momentum conservation in Mach effects:
[41]
If we produce a fluctuating mass in an object, we can, at least in
principle, use it to produce a stationary force on the object, thereby
producing a propulsive force thereon without having to expel propellant
from the object. We simply push on the object when it is more massive,
and pull back when it is less massive. The reaction forces during the
two parts of the cycle will not be the same due to the mass fluctuation,
so a time-averaged net force will be produced. This may seem to be a violation of momentum conservation. But the Lorentz invariance of the theory guarantees that no conservation law is broken. Local momentum conservation is preserved by the flux of momentum in the gravity field that is chiefly exchanged with the distant matter in the universe. [emphasis added]
Two terms are important for propulsion on the right-hand side of the previous equation:
- The first, linear term is called the impulse engine
term because it expresses mass fluctuation depending on the derivative
of the power, and scales linearly with the frequency. Past and current
experiments about Mach effect thrusters are designed to demonstrate thrust and the control of one type of Mach effect.
- The second, quadratic term is what Woodward calls the wormhole term, because it is always negative. Although this term appears to be many orders of magnitude
weaker than the first term, which makes it usually negligible,
theoretically, the second term's effect could become huge in some
circumstances. The second term, the wormhole term, is indeed driven by
the first impulse engine term, which fluctuates mass by around plus or
minus the rest mass value. When fluctuations reach a very high amplitude
and mass density is driven very close to zero, the equation shows that
mass should achieve very large negative values very quickly, with a
strong non-linear behavior. In this regard, the Woodward effect could
generate exotic matter, although this still remains very speculative due to the lack of any available experiment that would highlight such an effect.
Applications of propellantless propulsion include straight-line
thruster or impulse engine, open curved fields for starship
warp drives, and even the possibility of closed curved fields such as traversable benign
wormholes.
[44]
Negative bare mass of the electron
The mass of the electron is positive according to the
mass–energy equivalence E =
mc2 but this
invariant mass is made from the
bare mass of the electron "clothed" by a
virtual photon cloud. According to
quantum field theory, as those virtual particles have an energy more than twice the bare mass of the electron, mandatory for
pair production in
renormalization, the nonelectromagnetic bare mass of the "unclothed" electron has to be
negative.
[45]
Using the
ADM formalism,
Woodward proposes that the physical interpretation of the "wormhole
term" in his transient mass equation could be a way to expose the
negative bare mass of the electron, in order to produce large quantities
of exotic matter that could be used in a warp drive to propel a
spacecraft or generate traversable wormholes.
[46]
Space travel
Current
spacecraft achieve a change in velocity by the expulsion of
propellant, the extraction of momentum from stellar
radiation pressure or the
stellar wind or the utilisation of a
gravity assist ("slingshot") from a planet or moon. These methods are limiting in that
rocket propellants
have to be accelerated as well and are eventually depleted, and the
stellar wind or the gravitational fields of planets can only be utilized
locally in the
Solar System. In
interstellar space
and bereft of the above resources, different forms of propulsion are
needed to propel a spacecraft, and they are referred to as advanced or
exotic.
[47][48]
Impulse engine
If
the Woodward effect is confirmed and if an engine can be designed to
use applied Mach effects, then a spacecraft may be possible that could
maintain a steady acceleration into and through interstellar space
without the need to carry along propellants. Woodward presented a paper
about the concept at the
NASA Breakthrough Propulsion Physics Program Workshop conference in 1997,
[49][50] and continued to publish on this subject thereafter.
[51][52][53][54]
Even ignoring for the moment the impact on
interstellar travel, future spacecraft driven by impulse engines based on Mach effects would represent an astounding breakthrough in terms of
interplanetary spaceflight alone, enabling the rapid
colonization
of the entire solar system. Travel times being limited only by the
specific power of the available power supplies and the acceleration
human physiology can endure, they would allow crews to reach any moon or
planet in our solar system in less than three weeks. For example, a
typical one-way trip at an acceleration of
1 g from the Earth to the
Moon would last only about 4 hours; to
Mars, 2 to 5 days; to the
asteroid belt, 5 to 6 days; and to
Jupiter, 6 to 7 days.
[55]
Warp drives and wormholes
As
shown by the transient mass fluctuation equation above, exotic matter
could be theoretically created. A large quantity of negative
energy density would be the key element needed to create warp drives
[56] as well as traversable
wormholes.
[57]
As such, if proven to be scientifically valid, practically feasible and
scaling as predicted by the hypothesis, the Woodward effect could not
only be used for interplanetary travel, but also for apparent
faster-than-light interstellar travel:
Patents and practical devices
Two
patents have been issued to Woodward and associates based on how the
Woodward effect might be used in practical devices for producing thrust:
- In 1994, the first patent was granted, titled: "Method for
transiently altering the mass of objects to facilitate their transport
or change their stationary apparent weights".[59]
- In 2002, a second patent was granted, titled: "Method And Apparatus
For Generating Propulsive Forces Without The Ejection Of Propellant".[60]
- In 2016, a third patent was granted and assigned to the Space Studies Institute, covering the realistic realizations of Mach effects.[61]
Woodward and his associates have claimed since the 1990s to have
successfully measured forces at levels great enough for practical use
and also claim to be working on the development of a practical prototype
thruster. No practical working devices have yet been publicly demonstrated.
[2][3][6][41]
The NIAC contract awarded in 2017 by
NASA for the development of Mach effect thrusters is a primary three-task effort, two experimental and one analytical:
[12]
- Improvement of the current laboratory-scale devices, in order to
provide long duration thrust at levels required for practical propulsion
applications.
- Design and development of a power supply and electrical systems to
provide feedback and control of the input AC voltage, and resonant
frequency, that determine the efficiency of the MET.
- Improve theoretical thrust predictions and build a reliable model of
the device to assist in perfecting the design. Predict maximum thrust
achievable by one device and how large an array of thrusters would be
required to send a probe, of size 1.5 m diameter by 3 m, of total mass
1245 kg including a modest 400 kg of payload, a distance of 8
light-years away.
Experiments
Test devices
Mach-Lorentz Thruster
Photograph of the 2006 Woodward effect MLT test article.
A former type of Mach effect
thruster was the Mach-Lorentz
thruster (MLT). It used a charging
capacitor
embedded in a magnetic field created by a magnetic coil. A Lorentz
force, the cross product between the electric field and the magnetic
field, appears and acts upon the ions inside the capacitor dielectric.
In such electromagnetic experiments, the power can be applied at
frequencies of several megahertz, unlike PZT stack actuators where
frequency is limited to tens of kilohertz. The photograph shows the
components of a Woodward effect test article used in a 2006 experiment.
[62]
However, a problem with some of these devices was discovered in 2007 by physicist Nembo Buldrini, who called it the
Bulk Acceleration Conjecture:
What [Nembo Buldrini] pointed out was that given the way the
transient terms of the Mach effect equation are written – in terms of
the time-derivatives of the proper energy density – it is easy to lose
sight of the requirement in the derivation that the object in which the
mass fluctuations occur must be accelerating at the same time. In some
of the experimental cases, no provision for such "bulk" acceleration was
made.15 As an example, the capacitors affixed to the tines
of the tuning fork in the Cramer and the students' experiments made no
provision for such an acceleration. Had the tuning fork been separately
exited and an electric field applied to the capacitor(s) been properly
phased, an effect might have been seen. But to simply apply a voltage to
the capacitors and then look for a response in the tuning fork should
not have been expected to produce a compelling result.
Other examples could be cited and discussed. Suffice it to say,
though, that after Nembo focused attention in the issue of bulk
accelerations in the production of Mach effects, the design and
execution of experiments changed. The transition to that work, and
recent results of experiments presently in progress, are addressed in
the next chapter.
15 By "bulk" acceleration we are referring to the fact
that the conditions of the derivation include that the object be both
accelerated and experience internal energy changes. The acceleration of
ions in the material of a capacitor, for example, does not meet this
condition. The capacitor as a whole must be accelerated in bulk while it
is being polarized.
— James F. Woodward, in Making Starship and Stargates, Springer 2013, page 132.[15]
Mach Effect Thruster or MEGA drive
To
address this issue, Woodward started to design and build a new kind of
device known as a MET (Mach Effect Thruster) and later a MEGA drive
(Mach Effect Gravitational Assist drive), using capacitors and a series
of thick
PZT disks. This ceramic is
piezoelectric, so it can be used as an electromechanical actuator to accelerate an object placed against it: its
crystalline structure expands when a certain
electrical polarity is applied, then contracts when the opposite field is applied, and the stack of discs vibrates.
In the first tests, Woodward simply used a
capacitor
between two stacks of PZT disks. The capacitor, while being
electrically charged to change its internal energy density, is shuttled
back and forth between the PZT actuators.
Piezoelectric
materials can also generate a measurable voltage potential across their
two faces when pressed, so Woodward first used some small portions of
PZT material as little
accelerometers
put on the surface of the stack, to precisely tune the device with the
power supply. Then Woodward realized that PZT material and the
dielectric
of a capacitor were very similar, so he built devices that are made
exclusively of PZT disks, without any conventional capacitor, applying
different signals to different portions of the cylindrical stack. The
available picture taken by his graduate student Tom Mahood in 1999 shows
a typical all-PZT stack with different disks:
[63]
- The outer, thicker disks on the left and right are the "shuttlers".
- The inner stack of thin disks in the center are the shuttled
capacitors storing energy during acceleration, where any mass shift
would occur.
- The even thinner disks placed between the shuttlers and on both side
of the inner disk capacitors are the "squeezometers' acting as
accelerometers.
During forward acceleration and before the transient mass change in the capacitor decays, the resultant increased
momentum is transferred forward to a bulk "reaction mass" through an
elastic collision (the
brass
end cap on the left in the picture). Conversely, the following decrease
in the mass density takes place during its backward movement. While
operating, the PZT stack is isolated in a Faraday cage and put on a
sensitive
torsion
arm for thrust measurements, inside a vacuum chamber. Throughout the
years, a wide variety of different types of devices and experimental
setups have been tested. The force measuring setups have ranged from
various load cell devices to
ballistic pendulums to multiple
torsion
arm pendulums, in which movement is actually observed. Those setups
have been improved against spurious effects by isolating and canceling
thermal transfers, vibration and electromagnetic interference, while
getting better current feeds and bearings. Null tests were also
conducted.
[64]
In the future, Woodward plans to scale thrust levels, switching from the current
piezoelectric dielectric ceramics (
PZT stacks) to new
high-κ dielectric nanocomposite polymers, like
PMN,
PMN-PT or
CCTO. Nevertheless, such materials are new, quite difficult to find, and are
electrostrictive, not piezoelectric.
[65][66]
In 2013, the
Space Studies Institute
announced the Exotic Propulsion Initiative, a new project privately
funded that aims to replicate Woodward's experiments and then, if proven
successful, fully develop exotic propulsion.
[67] Gary Hudson, president and CEO of SSI, presented the program at the 2014
NASA Institute for Advanced Concepts Symposium.
[68]
EmDrive
Another type of claimed propellantless thruster, called the
EmDrive by its inventor British engineer Roger Shawyer, has been proposed to work due to a Mach effect:
[8][9]
The asymmetric resonant
microwave cavity would act as a capacitor where:
- surface currents propagate inside the cavity on the conic wall between the two end plates,
- electromagnetic resonant modes create electric charges on each end plate,
- a Mach effect is triggered by Lorentz forces from surface currents on the conic wall,
- a thrust force arises in the RF cavity, due to the variation of the electromagnetic density from evanescent waves inside the skin layer.
When a
polymer
insert is placed asymmetrically in the cavity, its dielectric
properties result in greater asymmetry, while decreasing the cavity
Q factor.
The cavity's acceleration is a function of all the above factors, and
the model can explain the acceleration of the cavity with and without a
dielectric.
[10]
Results
From his initial paper onward Woodward has claimed that this effect is detectable with modern technology.
[1]
He and others have performed and continue to perform experiments to
detect the small forces that are predicted to be produced by this
effect. So far some groups claim to have detected forces at the levels
predicted and other groups have detected forces at much greater than
predicted levels or nothing at all. To date there has been no
announcement conclusively confirming proof for the existence of this
effect or ruling it out.
[6]
- In 2004, Paul March of Lockheed Martin Space Operations,
who started working in this research field in 1998, presented a
successful replication of Woodward's previous experiments at STAIF.[75]
- In 2004, John G. Cramer and coworkers of the University of Washington reported for NASA
that they had made an experiment to test Woodward's hypothesis, but
that results were inconclusive because their setup was undergoing strong
electrical interference which would have masked the effects of the test
if it had been conducted.[76]
- In 2006, Paul March and Andrew Palfreyman reported experimental
results exceeding Woodward's predictions by one to two orders of
magnitude. Items used for this experiment are shown in the photograph
above.[62]
- In 2006, Martin Tajmar, Nembo Buldrini, Klaus Marhold and Bernhard Seifert, researchers of the then Austrian Research Centers
(now the Austrian Institute of Technology) reported results of a study
of the effect using a very sensitive thrust balance. The researchers
recommended further tests.[77]
- In 2010, Ricardo Marini and Eugenio Galian of the IUA (same
Argentine institute as Hector Brito's) replicated previous experiments,
but their results were negative and the measured effects declared as
originating from spurious electromagnetic interferences only.[78]
- In 2011, Harold "Sonny" White of the NASA Eagleworks laboratory and his team announced that they were rerunning devices from Paul March's 2006 experiment[62] using force sensors with improved sensitivity.[79]
- In 2014, Nembo Buldrini tested a Woodward device on a thrust balance in a high vacuum at the FOTEC research center in Austria,
confirming qualitatively the presence of the effect and reducing the
number of possible false positives; although recommending more
investigation due to the relative small magnitude of the effect.[82]
Debate
Inertial frames
All
inertial frames are in a state of constant, rectilinear motion with
respect to one another; they are not accelerating in the sense that an
accelerometer at rest in one would detect zero acceleration. Despite
their ubiquitous nature, inertial frames are still not fully understood.
That they exist is certain, but what causes them to exist – and whether
these sources could constitute reaction-media – are still unknown. Marc
Millis, of the NASA
Breakthrough Propulsion Physics Program, stated "
For
example, the notion of thrusting without propellant evokes objections
of violating conservation of momentum. This, in turn, suggests that
space drive research must address conservation of momentum. From there
it is found that many relevant unknowns still linger regarding the
source of the inertial frames against which conservation is referenced.
Therefore, research should revisit the unfinished physics of inertial
frames, but in the context of propulsive interactions. "
[83] Mach's principle is generally defined within
general relativity
as "the local inertia frame is completely determined by the dynamic
fields in the universe." Rovelli evaluated a number of versions of
"Mach's principle" that exist in the literature. Some are partially
correct and some have been dismissed as incorrect.
[19]
Conservation of momentum
Momentum
is defined as mass times velocity. Conservation of momentum applies to
velocity terms, usually described in a two dimensional plane with a
vector
diagram. A vector representing velocity has both direction and
magnitude. A requirement for determining conservation of momentum is
that an
inertial frame or
frame of reference for the observer be fixed.
Inertial frames
are well defined for constant velocity and conservation of momentum
holds for all such frames. During acceleration or a change in
acceleration, conservation of momentum applies to the local inertial
frame (LIF) of instantaneous velocity, not to the
proper acceleration a.k.a. coordinate acceleration), as measured by the accelerated observer.
[citation needed]
A challenge to the mathematical foundations of Woodward's hypothesis were raised in a paper published by the
Oak Ridge National Laboratory
in 2001. In the paper, John Whealton noted that the experimental
results of Oak Ridge scientists can be explained in terms of force
contributions due to time-varying
thermal expansion,
and stated that a laboratory demonstration produced 100 times the
Woodward effect without resorting to non-Newtonian explanations.
[84]
In response, Woodward published a criticism of Whealton's math and
understanding of the physics involved, and built an experiment
attempting to demonstrate the flaw.
[85]
A rate of change in
momentum represents a force, whereby
F =
ma. Whealton et al. use the technical definition,
F=d(
mv)/d
t, which can be expanded to
F=
m d
v/d
t + d
m/d
t v. This second term has both delta mass and
v,
which is measured instantaneously; this term will, in general, cancel
out the force from the inertial response terms predicted by Woodward.
Woodward argued that the d
m/d
t v term does not
represent a physical force on the device, because it vanishes in a frame
where the device is momentarily stationary.
[43]
In an appendix to his thesis, Mahood argues that the unexpectedly
small magnitude of the results in his experiments are a confirmation of
the cancellation predicted by Whealton; the results are instead due to
higher-order mass transients which are not exactly cancelled.
[70] Mahood would later describe this argument as "one of the very few things I've done in my life that I actually regret".
[86]
Although the momentum and energy exchange with distant matter guarantees global conservation of energy and momentum, this
field exchange is supplied at no material cost, unlike the case with conventional fuels. For this reason, when the
field
exchange is ignored, a propellantless thruster behaves locally like a
free energy device. This is immediately apparent from basic Newtonian
analysis: if constant power produces constant thrust, then input energy
is linear with time and output (kinetic) energy is quadratic with time.
Thus there exists a break-even time (or distance or velocity) of
operation, above which more energy is output than is input. The longer
it is allowed to accelerate, the more pronounced will this effect
become, as simple Newtonian physics predicts.
Considering those conservation issues, a Mach effect thruster relies
on Mach's principle, hence it is not an electrical to kinetic
transducer, i.e. it does not convert
electric energy to
kinetic energy. Rather, a Mach Effect Thruster is a gravinertial
transistor that controls the flow of gravinertial
flux, in and out of the active mass of the thruster. The primary power into the thruster is contained in the flux of the
gravitational field, not the electricity that powers the device. Failing to account for this flux, is much the same as failing to account for the
wind on a
sail.
[87]
Mach effects are relativistic by nature, and considering a spaceship
accelerating with a Mach effect thruster, the propellant is not
accelerating with the ship, so the situation should be treated as an
accelerating and therefore
non-inertial reference frame, where
F does not equal
ma.
Keith H. Wanser, professor of physics at California State University,
Fullerton, published a paper in 2013 concerning the conservation issues
of Mach effect thrusters.
[88]
Quantum mechanics
In 2009,
Harold "Sonny" White of
NASA
proposed the Quantum Vacuum Fluctuation (QVF) conjecture, a
non-relativistic hypothesis based on quantum mechanics to produce
momentum fluxes even in empty
outer space.
[89] Where Sciama's gravinertial field of
Wheeler–Feynman absorber theory is used in the Woodward effect, the White conjecture replaces the Sciama gravinertial field with the
quantum electrodynamic vacuum
field. The local reactive forces are generated and conveyed by momentum
fluxes created in the QED vacuum field by the same process used to
create momentum fluxes in the gravinertial field. White uses
MHD plasma rules to quantify this local momentum interaction where in comparison Woodward applies
condensed matter physics.
[79]
Based on the White conjecture, the proposed theoretical device is called a
quantum vacuum plasma thruster
(QVPT) or Q-thruster. No experiments have been performed to date.
Unlike a Mach effect thruster instantaneously exchanging momentum with
the distant cosmic matter through the advanced/retarded waves (
Wheeler–Feynman absorber theory)
of the radiative gravinertial field, Sonny's "Q-thruster" would appear
to violate momentum conservation, for the thrust would be produced by
pushing off virtual "Q" particle/antiparticle pairs that would
annihilate after they have been pushed on. However, it would not
necessarily violate the law of conservation of energy, as it requires an
electric current to function, much like any "standard" MHD thruster,
and cannot produce more kinetic energy than its equivalent net energy
input.
[citation needed]
Woodward and Fearn showed why the amount of
electron-
positron virtual pairs
of the quantum vacuum, used by White as a virtual plasma propellant,
cannot account for thrusts in any isolated, closed electromagnetic
system such as the QVPT or the
EmDrive.
[90]
Media reaction
Woodward's
claims in his papers and in space technology conference press releases
of a potential breakthrough technology for spaceflight have generated
interest in the popular press
[5][20] and university news
[91][92] as well as the space news media.
[6][93][94][95] Woodward also gave a video interview
[96] for the TV show
Ancient Aliens, season 6, episode 12.
[97] However doubters do exist.
[6]