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;




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 three 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).
Tajmar, M., "The Biefeld-Brown Effect: Missinterpretation of Corona Wind Phenomena," AIAA Journal, Vol 42, pp 315-318 (2004)

All 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.


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Author:  Nicholas Thomas, Summer Student 2002
Responsible Official for Content:  Marc G. Millis
Curator:  -- Not presently available --
Last update: May 13, 2004