The Evidence

Today there exists a large body of accumulated evidence that indicate how people all over the world have been working on new ways to produce thrust for a wide range of purposes. From the early twenties through to the fifties and sixties, and right up to the present. Some of them can be described as tinkerers and amateurs, midnight engineers, and spare time scientists. Most however, are cranks, and a few, (let's face it) charlatans. Be warned that I will NOT be presenting in these pages, materials, nor will I provide endorsement, nor subscribe to ideas or views which, in any way, shape or form, can be construed (or misconstrued) as unscientific, pseudo-scientific, or just plain stupid. At the risk of severely limiting my reader audience I suggest that those of you who are interested in UFOs, Star Trek, and the paranormal, aim your browsers at most of the other ( 99.98 % ) available sites on the web, (you know who you are). Alternatively, you may try csicop or the Australian Sceptics Society and perhaps learn something of the scientific method.

Having dispensed with the little disclaimer above, It is time to present the facts.

In the past ninety years or so, there have been, basically, very few, serious, laboratory scale proposals or experiments that have been suggested, or indeed that are amenable to testing. These schemes belong to two broad categories which can loosely be described as Field Dependent Interaction (FDP) and Inertial propulsion (IP) methods. A more recent member of the FDP category, is the claim, originated by Podkletnov, ( formerly of Tampere University of Technology, in Finland ), of the weak gravitational shielding effect produced by a high-critical-temperature superconducting ceramic disk when suspended by electromagnetic fields and caused to spin. ( see the bibliography section for more information ). In the IP category probably the best known example is the Dean Drive. A purely electro-mechanical device which its inventor, Norman L. Dean ( a civil servant ), claimed would lose some fraction of its weight when activated. The device was never thoroughly nor satisfactorily tested to the satisfaction of any civilian scientist at the time, and questions remain to be answered, to this day. Although the 'popularity' of Dean's device peaked in the mid sixties, this type of device seems to go through a periodic rediscovery process, in one form or another.

Most all kinds of 'reactionless' or 'propellantless' devices belong to the IP category. Moving closer to current developments in IP, the most intriguing ( read feasibly testable ) proposal since the sixties, is that put forward by Dr. James F. Woodward, who is currently Adjunct Professor of Physics at California State University at Fullerton. Professor Woodward's idea is rather unusual because although at first glance the hardware he has developed might lead you to conclude that it belongs to the Inertial Propulsion category, if you work through his papers ( including "Transient Mass Fluctuations") and his patent disclosure, he actually claims Machian style non-local interactions with the distant matter in the universe (i.e., the "fixed" stars). This is analogous to the Wheeler-Feynman "absorber" interpretation of radiation reaction effects based on the concept of advanced and retarded waves. Which clearly puts the concept in the Field Dependent Interaction category. Subsequently, he surmises that the transient mass fluctuations produced by his device are in fact due to a kind of radiation reaction. For more on this, see the appropriate section in the references. Below are some comments, taken from Woodward's patent ( No. 5,280,864 ) and other papers;

... It follows from this equation that time-varying energy densities in material media are massive sources of the gravitational field.

...We now ask: How does the launching of electromagnetic waves, radiation that is, produce the reaction force on electrons we know must be present if the conservation of energy and momentum are to be preserved? Well, if electrons are extended spheres of charged dust, then the electrical forces (and those that balance them) that act between the particles of dust must take time to get across the distances separating them according to special relativity theory. So when we push on one part of the electron, only later do the other parts detect the changes our push has produced and adjust for them. Because of these time delays, during accelerations the forces between the dust particles are unbalanced. The net force due to the imbalance turns out to be the force of radiation reaction. The unbalanced force disappears when no accelerating force is present, even if the electron is moving.

Referring to the equation which describes the self reaction force on an electron in one dimension;

...The second term is the one that accounts for radiation reaction forces. It has two noteworthy properties. First, it doesn't depend on the size or shape of the electrical dust, telling us that it is independent of the self-energy business that presumably accounts for the inertial mass of the electron. Second, it depends on the third time derivative of position.

...To investigate energy and momentum conservation in radiative processes we have to let the force act to produce a change in the energy. The rate at which the energy changes, the power that is...

Finally, in Woodward's paper published in Foundations of Physics letters, Vol. 9, No. 1, 1996, entitled "Killing Time", he has this to say;

... If local detection of Machian effects that depend upon the absolute value of the gravitational potential are precluded in [General Relativity Theory], how is it possible that an effect like that considered in this section could exist? The answer to this question lies in noting that the effect goes as the second order time derivative of the proper energy density. Dimensionally, energy is mass times velocity squared, so its second order time derivative will involve the third time derivative of position. This is the signature of a radiation reaction effect. They are normally excluded in dynamical theories -- including GRT -- by the demand that such terms vanish. ... radiation reaction effects, in electrodynamics at least, exist as a matter of fact. Given the parallels between gravity and electromagnetism, it would be quite remarkable if this effect did not exist.

Interestingly, Woodward's paper reminds me of the May 1962 article published in Analog by Dr. William O. Davis, entitled "The Fourth Law of Motion". In the paper Davis puts forward, rather convincingly, some strikingly persuasive arguments for the possible existence of a force proportional to the third time derivative of displacement (or position), usually known in engineering circles as "surge", "jerk", or rate-of-onset. Below are some important extracts.

The class of anomalous behaviour which we wish to study involves in every case the presence of surge as we have just defined it. Under conditions of constant or zero acceleration mechanical bodies or systems of bodies obey Newton's Laws reasonably well. It is under conditions of changing acceleration that difficulties arise. The key word in our analysis of dynamic systems will be "simultaneity". The Laws of Motion presuppose exact simultaneity of action and reaction......to satisfy Newton's image of the universe. Einstein recognised that this condition would not be met in the case of bodies separated by astronomical distances since the change in gravitational field would have to be propagated at some finite velocity, presumably that of light, but he did not carry his investigations into the simpler field of everyday mechanics.

If it is true that two stars cannot act as a Newtonian system in less time than it takes gravity to propagate from one to the other and back, it is equally true that any real body or system of bodies suffers to a greater or lesser extent from the same problem. Newton's Laws, strictly speaking, apply only to mathematically infinitesimal particles or perfectly rigid bodies, neither of which exist in the real world.

Consider, for example, a simple steel rod one meter long which I wish to move by applying a force to one end. The instant I start to apply the force a message leaves the end of the rod as a plastic or elastic compressive wave which travels at a speed of approximately, 5,000 meters/second. The compressive wave travels to the far end of the rod where it is reflected as a rarefaction and returns to the point of application of force at the same speed.

Until the wave returns, 4/10,000 of a second later the rod as a whole cannot move according to the Second Law! No matter how much force is applied, the centre of gravity of the rod cannot obey F = ma in less than this time. It would be oversimplifying to say that the rod acts as though it had infinite mass during this time, since the centre of gravity will be moved somewhat by the compression, but for all practical purposes, the rod acts as though it had a much larger mass than it actually has.

...The particular behaviour of a given system will depend on: (a) how rapidly the force is applied and, (b) the built-in delay time, or "critical action time" of the system. More exactly, we have found that the behaviour depends upon how rapidly one attempts to change the acceleration applied to the body. The ultimate acceleration of the body, the "a" of F = ma, is not what is critical; it is the rate of onset or "surge" of the acceleration which is vital.

He goes on to offer some justification for his line of enquiry which might help to perhaps counter some criticisms which he probably felt could be levelled at him;

Furthermore, in connection with a possible modification to the equations of motion he writes

...Starting transients normally are considered only in connection with the beginning or the end of a motion and hence are accorded no particular attention. However, there are certain types of cyclic motion where the transient behaviour is continuous, or repetitive and we will see later that even certain single transients may have critical importance in understanding natural events...[This] solution demonstrates the most significant characteristic of real bodies, to wit: not only is displacement somewhat less than Newton would predict for a given force, leading to an increased apparent mass, but reaction is no longer exactly opposite to the applied force: there is a phase angle which will be larger the longer the critical action time of the system! Action and reaction are not simultaneous!

Based on a gyroscopic model, he then proceeds to define the "intractance" of a system as the resistance of the system to a change of inertial field, in analogy to the way that self-inductance represents the resistance of a coil to a change in magnetic field.

We come to a consideration of what must be the Fourth Law of Motion. There will obviously be several alternative expressions. Mathematically, what seems to be critical in systems with intractance is the rate of change of energy, so that the Law is perhaps best expressed in these terms:

The energy of a given system can only be changed in some finite length of time depending on the system, and never in zero time.

... At this point, it is proper to ask the question: Is there any real evidence for this theory, and if true, why haven't these phenomena been obvious for some time?

First of all, rate of onset effects per se are well-known and their existence is hardly controversial. The entire field of shock and vibration gives signs of supporting our conclusions. In general, mechanical systems do not posses the simple resonance characteristics that Newtonian theory would predict. The existence of intractance permits many more modes of resonance since there are now four terms in interaction in the equation of motion for a system including viscous damping and linear restoring force instead of three. This permits a much greater number and variety of resonances to occur.

The article continues with Davis exploring some of the logical consequences based on the main argument of the possible existence of an extra third derivative term in the equation of motion.

Now I'm not suggesting that Woodward's ideas are based on Davis' work. They are not. I'm merely pointing out the fact of the important role played by cyclic motion and the rate of change of energy in both Woodward's and Davis' hypotheses. Indeed if anything, these similarities tend to indicate that further work along these lines may eventually prove to be successful in isolating a real physical effect.

Drawing your attention, now, to some obscure but nevertheless interesting work which pre-dates both Woodward and Davis which, I think is pertinent, and merits a further look. I'm referring to an abstract published in the American Journal of the Rocket Society by Harry W. Bull (a Syracuse, N.Y. inventor), No. 29, Sep. 1934. Under the heading " 5. Entirely New Reaction Methods " pages 7 to 8. Since the article is so brief I will quote it in its entirety;

An entirely new means of securing a reaction was next tested. The rocket was made up of a series of chambers the ends of which consisted of steel disks fastened together by a 1/4 inch diameter steel rod. The chambers were arranged to explode in series, blowing the steel disks downward with great velocity. Knowing the weight of the disk and its velocity and also the weight of the complete rocket it is a simple matter to find the energy of the recoil. Although this type of rocket works, it leaves much to be desired in the line of safety.

A series of tests now followed which I believe are original in the field of reaction. They dealt with a form of impact-impulse reactions which are created mechanically. The apparatus if placed in a box in space would move without the use of a jet of any sort, it being propelled by a reciprocating motion of two weights. The truth of the theory may be easily proven by a very simple apparatus.

The theory is that a large weight with a low velocity ( if stopped by springs ) will yield more foot pounds of energy than a small weight with a high velocity being stopped by impact, even though both were given the same initial force. A simple illustration: Let us assume you are in the centre of a room in space. One wall is elastic and the opposite one solid. In your hands are two balls one heavy and the other light and you throw them with the same force at the same time. The heavier one hits the elastic wall with an impulse and a large amount of energy is given to the room in that direction. The lighter one having the same energy hits the solid wall but its energy is dissipated in heat and distortion. If there could be found a method whereby the kinetic energy of the lighter ball could be effectively utilised the room would move in the other direction.

The following year (January 1935), an article appeared in the monthly magazine 'Popular Science', showing some drawings depicting the basic unit and a photo of the author flipping the switch on a pendulum mounted set-up of the unit. These are some extracts from the Popular Science article;

This elementary form of reaction motor operates on a principle that has long been neglected by engineers, but which Bull believes can be applied in aircraft and other vehicles. It depends upon the difference in effectiveness of two ways of transmitting energy, which can be termed impact and impulse. If a weight is thrown against a solid wall, it is stopped by impact, and much of its energy is wasted in distorting the weight and the wall and in producing heat. However, if the weight is thrown against a spring fastened to the wall, it is stopped by impulse, the spring conserving the energy of the moving weight and transmitting the resulting force, with little loss, to the wall. Tests have shown a weight will yield three times more force by impulse than by impact.

...Achieving a practical reaction motor, Bull points out, depends to a large extent, paradoxically, upon how inefficient it can be made. The more force that can be wasted in impact, the greater force will be left to push ahead, a new problem for engineers, who have spent years trying to conserve energy rather than dissipate it. Likewise, much experimentation remains to be done upon the impulse side of the apparatus, which is still far from efficient.

This is perhaps the simplest proof of concept device imaginable. In fact I've built and tested it ( using an air track ), and am able to say that indeed the device works as claimed. Better yet, Bull made no theoretically contorted hypothesis as to its modus operandi. The only important question that remains is, if the cycle can be closed and made continuous (i.e. repeatable) without affecting its generality. As it stands the device acts as a 'one-shot'. That is, it requires resetting before each demonstration.

Surprisingly, Einstein first used a thought experiment to simplify the proof of the proportionality of energy and inertial mass (E=mc²), in his time often called the law of inertia of energy. He did this by considering what superficially looks like the Bull device, but with two absorbing bodies, fixed one at either end of a tube, which are able to, in turn, emit and absorb a photon. The whole argument is based on the fact that radiation exerts a pressure. Einstein's first mathematical derivation (1905) supposed the tube to be rigid. Later (1907), he himself criticised the concept of a rigid body in the theory of relativity. The complete discussion can be found in the book " Einstein's Theory of Relativity ", (pages 278 to 286), by Max Born, first published by Methuen Company in 1924. The revised edition is currently available through Dover Publications. Some exerpts follow;

...Here the essential difference between classical and relativistic mechanics comes to light. In classical mechanics we have to distinguish between processes which conserve mechanical energy and those which do not but where it is changed into heat or other energy forms. Returning, for instance, to our inelastic collision we see that one-half of the kinetic energy (as observed in the system ) is changed into heat. Therefore mechanical energy is not conserved.

[regarding the translation of the tube] ...This is the amount of inertial mass [m=E/c²] that must be ascribed to the energy E in order that the principle of mechanics which states that no changes of position [of the tube] can occur without the action of external forces remain valid.

Since every form of energy is finally transformable into radiation by some process or other, this law must be universally valid. Thus we have a great unification in our knowledge of the material world: Matter in the widest meaning of the word (including light and other forms of pure energy, in the language of classical physics) has two fundamental qualities: inertia, measured by its mass, and the capability of performing work, measured by its energy. These two are strictly proportional to one another. Where ever electric and magnetic fields or other effects lead to intense accumulations of energy, they are accompanied by inertia. Electrons and atoms are examples of enormous concentrations of energy.

That is, Einstein concluded that this kind of propulsion cannot be possible simply because the absorbed photon has a mass-equivalent energy which renders the act of returning the masses to their original places a kind of inverse operation to that which provided the original displacement. Subsequently, this leads to an average total displacement of zero over a complete cycle.

However, it should be clear that Bull's device differs from Einstein's 'gedanken experiment' insofaras the former was constructed a priori with the purpose of investigating any possible anomalous effects (due to some of the considerations given in the analysis section), which may have gone unnoticed. And the later was thought up a posteriori solely for the purpose of allowing justification for the principles of conservation of energy and momentum. Sometimes it is necessary to read between the lines.

So far, we have only covered what I consider to be among the best available evidence (accessible to both scholars and non-scholars alike), that exist in the archives, and on the net. Additionally, there is a vast body of knowledge, mostly written by researchers, for researchers, and as a consequence does not make for particularly easy reading. It is therefore rare, and refreshing, to once in a while find a technical paper which is both reasonably rigorous and transparent. I personally believe that the above examples fill this description nicely and are therefore instructive for anyone wishing to learn about this unusual but potentially important and exciting subject.

Until now these ideas were frowned upon and shunned by all serious investigators, ( understandably, given the ridicule engendered by the hocus-pocus factor strewn liberally about in the rampant disinformation out-there ), this is still true today, although to a much lesser extent. Indeed, today, we are much more likely to test, or at least study, all reasonable proposals for which funding is available. Not even NASA will turn a blind eye if it can smell some potential. Such are the interesting times we live in.

It is important to stress at this point, that presently, there is no one to my knowledge, on or off the planet, who can truly claim to know how any of these devices operate, (if indeed they do at all) with any degree of certainty or conviction whatsoever.

You will find more of this kind of evidence in the biblio. index, and analysis section of this site. While I have tried to do my best to weed out references and papers that I consider to be time wasting, pseudo-science, new (and sometimes old) age mumbo-jumbo from the list, please drop me a line if you spot any of this kind of material on this site. I'll be only too happy to indulge in a little gardening. Remember, keep in mind this caveat. As you begin to search the web for yourself be prepared to run into a lot of less-than-questionable stuff.