NASA Breakthrough
Propulsion Physics Project
COMMON
ERRORS
Compiled by: Nicholas Thomas
Summer Student
2002
Aug. 9, 2002
A variety of "breakthrough" propulsion
ideas are regularly submitted to the NASA Breakthrough Propulsion Physics
Project from amateur researchers, far more than can be assessed. Many of
these submissions involve concepts that are already known not to work, even
though detailed assessments have not yet been published. Here now, as a
service to other would-be submitters and other curious researchers, are examples
of commonly submitted ideas that are not propulsion breakthroughs.
These examples include a description of why they appear to be a
breakthrough, and a description of what they really are.
Commonly submitted concepts;
(Others may be added later)
OSCILLATION THRUSTERS
Description
The oscillation thruster, also
known as a "sticktion drive," "internal drive," or "slip-stick drive," is a
commonly suggested form of space drive that uses the motion of internal masses
to create a net thrust. Although there have been many versions proposed,
all oscillation thrusters have the following common components:
Chassis to
support a system of masses,
Conveyor that moves the
masses through an asymmetric cycle,
Power source for the
conveyor.
A crucial feature is that these internal masses go through some
sort of cyclic motion where the motion in one direction is quicker than in the
return direction. One of the most famous oscillation thrusters is the
"Dean Drive" described in Patent 2,886,976. Another, more recent,
example is Patent 5,685,196 from Richard Foster.
![]() |
|
Figure from Foster Patent 5,685,196 |
![]() |
| Example of gyroscopic oscillation thruster |
| Source:
http://www.geocities.com/CapeCanaveral/Hall/1358/ |
Why it Looks Like a
Breakthrough
As the masses go through their cycle, the whole device will scoot
across the floor. One version, placed inside a boat, propelled the
boat. Some versions can even work on low-friction surfaces such as ice, or
on some air tracks. Thus, the oscillation thruster appears to be
creating thrust without using propellers or without expelling rocket
exhaust. If genuine, such a net thrust would have a significant advantage
over conventional rockets, because oscillation thrusters would not require the
incredible amount of propellant needed by rockets.
Reflexive
Objection
Such devices violate "Conservation of Momentum," a basic law of
known physics. It is because of the simplicity and strength of this
objection that deeper analyses are seldom published.
Deeper
Assessment
These drives can easily be explained with friction - specifically
the difference between moving friction and static friction. Recall that
the device's internal masses move fast in one direction and slow in the
other. When the masses move quickly, the device has enough reaction force
to overcome the coefficient of static friction of the floor (or other surface)
and the device slides. When the internal masses return slowly in the
other direction, the reaction forces are never enough to overcome the
coefficient of static friction (sometimes called "sticktion") and it just sticks
to the floor. The net effect is that such slip-stick motion causes the
device to scoot across the floor. A more fitting test would be to place
the device on a level pendulum stand or in free space. During the course
of the cycle, the center of mass of the device will always return to its
starting position and the whole system would just vibrate around its equilibrium
point. No matter how complicated the oscillation thruster, all the forces
will cancel each other out over time.
Conclusion
These types of oscillation
thrusters can never be used to drive a spacecraft - unless the spacecraft is in
contact with a floor. Changing the momentum of an object without exerting
force on an outside mass goes against the fundamental law of Conservation of
Momentum.
But What If
?...
To
keep an open, yet rigorous, mind to the possibility that there has been some
overlooked physical phenomena, it would be necessary that any future proposals
on these types of devices explicitly address all the conventional objections,
and pass a pendulum test. Any test results would have to be rigorous,
impartial, and address all possible causes that might lead to a false-positive
conclusion. To this day, no one has come forth with any viable theory or
experiment that reliably demonstrates that a genuine, external, net thrust can
be obtained with one of these devices. If such tests are ever produced,
and if a genuine new effect is found, then science will have to be revised,
because it would then appear as if such devices were violating Conservation of
Momentum.
In the mid 1960s, a
"jerk" effect (the time rate change of acceleration) was hypothesized as a
new type of force, but no experiments nor physical evidence were ever offered to
demonstrate that such a "jerk" exists, and even if it did, whether it could be
used to create a space drive. [Davis, "The Fourth Law of Motion", in
Analog Science Fiction, Science Fact, pp. 83-105, (May
1962).]
GYROSCOPIC ANTIGRAVITY
Description
A gyroscopic thruster is a
commonly suggested form of space drive that consists of a system of gyroscopes
connected to a central body. Gyroscopic thruster capabilities vary
depending on the claims of the particular inventor. Some inventors clam
that their drives work by producing an antigravity effect when the gyros are at
a high RPM. Other inventors say that their drives are able to transform
the gyro's angular momentum into linear momentum for the entire drive.
This later group - where a conversion from angular motion into linear thrust are
claimed, are really just "oscillation
thrusters," discussed previously (and shown above). These drives will
just vibrate by changing their internal center of mass, but can't actually
create a net force in any direction.
One of the better
known "antigravity" claims for gyroscopes, came from Eric Laithwaite.
Laithwaite was convinced that gyroscopes had lifting capabilities, and in 1973,
he demonstrated his gyro effect to the Royal Institute in London. His
demonstration consisted of a singe 50-lb gyro at the end of a rod. He
first demonstrated to the Institute that he was unable to lift the device when
it was not spinning. But when the gyro was brought up to speed, he was
able to lift the gyro above his head. Laithwaite believed that he had
discovered a new aspect of physics that would allow a space drive to be made
with gyros. The Institute, however, knew that Laithwaite was wrong.
The Institute never published his presentation.
Note that this
"gyroscopic antigravity" section is not related to the 1992 claims, where
it was published that objects appeared to weigh less over superconductors that
were spinning and being subjected to RF radiation. This unconfirmed
phenomenon deals with entirely different issues than the simplistic gyro
inventions discussed here. Also, this section is not related to
published observations that gyros have different weights depending on rotation
direction, claims that have also not been independently verified.
Both these other topics have appeared in the normal scientific literature.
For reliable assessments of these claims, please keep abreast of the scientific
literature and avoid drawing conclusions from Press articles on these
provocative topics.
Note too, that these
"gyroscopic antigravity" claims are not related to a very real spacecraft
device called a "reaction wheel" or "momentum wheel." These devices, used
widely in satellites, control the pointing direction ("attitude") of the
satellite.
Why it Looks Like a
Breakthrough
There are several different ways to get the appearance that gyros
can defy gravity. The most common is gyroscopic precession. During
gyroscopic precession the gyro tilts over and appears as if it might fall down
but is stopped by some "unseen" force that holds it up and causes it to rotate
around its pivot point.
Reflexive
Objection
Such devices violate "Conservation of Momentum," a basic law of
known physics. It is because of the simplicity and strength of this
objection that deeper analyses are seldom published.
Deeper
Assessment
These drives can be explained in terms of "precession." A
common school demonstration of gyroscopic precession involves placing a tilted,
spinning gyro on a table. Rather than tipping over the rest of the
way, the whole gyro assembly, instead, begins to rotate. This is a result
of "Conservation of Angular Momentum" as gravity is pulling down on the
gyro. What Laithwaite showed to the Institute was not a way of making
antigravity, but was a form of forced precession. Examine the figure
below. Laithwaite would force his gyro to rotate (arrow at base of "main
spindle"), and as a result, the whole gyro and rod assembly would turn upward
(arms pivoting up at "pivots"). An important detail is that the force is
not "lifting" the gyro, but is a "torque" that is twisting the gyro/rod assembly
upward about the pivot point of the gyro's arm.
![]() |
|
Example of a Laithwaite device |
| Source: Childress, The Anti-Gravity Handbook,
Adventures Unlimited Press, Stelle, IL,
1988. |
Although there are
other claims that spinning gyros can affect gravity, including legitimate
treatments from General Relativity, these are not space drive effects.
Consider for example, if it were possible to produce a gyro that spun at
relativistic speeds. The Special Theory of Relativity states that the mass
of the gyro will increase instead of decreasing. This is not an
antigravity effect.
Conclusion
Gyroscopes can never be used to
push a spacecraft, but gyroscopes, in the form of reaction wheels, can be used
to change the angular orientation of a spacecraft. Changing the
linear momentum of an object without exerting force on an outside mass, goes
against the fundamental law of Conservation of Momentum.
But What If
?...
To
keep an open, yet rigorous, mind to the possibility that there has been some
overlooked physical phenomena, it would be necessary that any future proposals
on these types of devices explicitly address all the conventional objections,
and pass a pendulum test. Any test results would have to be rigorous,
impartial, and address all possible causes that might lead to a false-positive
conclusion. To this day, no one has come forth with any viable theory or
experiment that reliably demonstrates a genuine, external, net thrust can be
obtained with one of these devices. If such tests are ever produced, and
if a genuine new effect is found, then science will have to be revised, because
it would then appear as if such devices were violating Conservation of
Momentum.
ELECTROSTATIC ANTIGRAVITY
Description
Electrostatic antigravity,
which originated at least as early as the version called the "Biefeld-Brown"
effect, is a force-producing effect resulting from placing high voltage
across unusually shaped capacitors. There are several variations of
this half-century-old idea, devices with such names as "Lifters," "Asymmetrical
Capacitors," "Electrogravitics," or "Electrokinetics." The shapes and
sizes of the capacitors vary, but they are typically large enough to be easily
observed (on the order of centimeters in size). Sometimes the
capacitors are shaped to look like flying saucers. Other times they are
arranged as rings and disks. One of the most recent versions, the
"Lifter," is usually a triangular arrangement of three capacitors, where the two
electrodes of the capacitors are placed one above the other. The upper
electrode is a simple wire. The lower electrode is a plate of aluminum
foil, oriented in an upright position. The whole assembly is constructed
out of balsa wood poles, aluminum foil, and copper wire.
Why it Looks Like a
Breakthrough
These devices are relatively easy to construct
and operate. They have no moving parts. When charged up to high voltage
(normally around 40 kV, and less then 1 mA of current), the light-weight
versions of these devices can lift off the ground and levitate. The power
supply, however, remains on the ground and the power is delivered with extension
wires. Since such levitation is seldom seen with everyday devices, many
people assume that some antigravity effect is at work.
Reflexive Objection
& Counter Arguments
For those who are familiar with
high voltage effects, such devices are assumed to be simply operating from ion
wind. Ion wind is an air flow that is created by the ions that move from
one capacitor electrode to the other. The devices are pushed up by the
reaction forces from this downward motion of the surrounding air. Even in
a vacuum, there can still be enough ion motion or corona discharge to cause
counter forces. If the devices were operating by something other
than ion wind, then such devices would appear to violate "Conservation of
Momentum," a basic law of known physics.
Most advocates for
these electrostatic antigravity devices admit that ion wind is present, but
claim that the observed forces are too large to be accounted for by just ion
wind.
Deeper
Assessments
Unlike the gyro
and oscillation
devices described earlier, these electrostatic antigravity devices are much more
difficult to rigorously analyze. It is very difficult to isolate all
spurious causes that might lead to a false positive, even when these devices are
operated in a vacuum. Fortunately, reports have been published that
describe more rigorous experimental techniques. Here are two
examples:
| Talley, R .L., (Veritay Technology, Inc. East Amherst NY), Twenty
First Century Propulsion Concept, PLTR-91-3009, Final Report for the
period Feb 89 to July 90, on Contract FO4611-89-C-0023, Phillips
Laboratory, Air Force Systems Command, Edwards AFB, CA 93523-5000,
(1991). |
| Tajmar, M., "Experimental Investigation of 5-D Divergent Currents
as a Gravity-Electromagnetism Coupling Concept", in Proceedings of
the Space Technology and Applications International Forum
(STAIF-2000), El-Genk editor, AIP Conference Proceedings 504, American
Institute of Physics, New York, pp. 998-1003,
(2000). |
Both these studies,
examining different versions and using different techniques, found that there
were no extra forces produced. These devices are not antigravity
devices.
Conclusion
Their is no new force at work
here. All evidence to date suggests that all the thrust created with
these devices comes from an easily produced phenomena, ion wind.
There is no evidence to suggest that any type of antigravity effect is
responsible for the thrust. None of the proponents of these devices have
reported any experimental evidence in any peer-reviewed publications to support
their claims that a new force is being demonstrated.
Regardless of the
cause of the effect, there is the question of utility. So far, such
devices cannot lift much mass (typically, they produce about a
few-thousandths of a Newton, while consuming around 20 to over 100 Watts).
None have been able to levitate their power supply, let alone an additional
payload. This limits their utility when compared to alternative forms of
aircraft propulsion. Regarding their application for spacecraft, their
in-vacuum performance has not yet been reliably measured. If and when such
tests are conducted, their performance can then be compared to other existing
forms of electric propulsion, such as Ion
Propulsion.
Because it is easy to build and operate one of these devices, however, its
most fitting utility may be as an instructional tool for demonstrating the
dramatic phenomenon of ion wind.
But What If
?...
There are, however, still some unresolved issues.
Specifically, during the Talley tests (referenced above), anomalous forces were
observed during the on/off transients -- anomalies that were never
resolved. To keep an open, yet rigorous, mind to the possibility that
there has been some overlooked physical phenomena, it would be necessary that
any future proposals on these types of devices explicitly address all the
conventional objections, and pass rigorous experimental tests. Any test
results would have to be impartial and address all possible causes that might
lead to a false-positive conclusion. To this day, no one has come forth
with any reliable experimental evidence that demonstrates that a genuine,
external, net thrust can be obtained with one of these devices. If such
tests are ever produced, and if a genuine new effect is found, then science will
have to be revised, because it would then appear as if such devices were
violating Conservation of Momentum.
[Return to the Breakthrough Propulsion
Physics Page]
---------------------------------------------
Author: Nicholas Thomas, Summer Student 2002
Responsible Official for Content: Marc G.
Millis
Curator: Jean
Schuerger, QSS Group, Inc.
Last
update: 08/09/02