In this experiment we investigate the somehow weird axial motion sluggishness that we have noticed in some of our bigger EHD thrusters. We had noticed that when powered on, an EHD thruster would 'feel' heavier if one tries to push it sideways. In this experiment I will show that the moment of inertia of the volume of air rotating within the EHD thruster is drastically increasing when the high voltage is applied, and then this extra 'mass effect' which is co-rotating with each element is immediately released to the environment when the electric field is switched off. Note that I am not claiming any energy to mass conversion, but rather a mass re distribution of air molecules, with the densest parts being the air sections in between the electrodes. The mass increase effect can be electrically controlled with a switching speed which can never be obtained by any mechanical means, and further, with no moving parts at all. It is analogous to a rotating turntable on which masses are moved outwards towards its rim, slowing down its motion. The effect is mainly generated by the electrodes forming the rim of the rotating EHD device. Thus an electrically controlled inertia device results, which offers resistance to change in motion depending on the internal electric field gradient. This device weighs 11g.
This is exactly the same as the above experiment, but sealed from the sides, top and bottom to eliminate interaction with external environment, eliminate any thrust effect or wind shielding effect. The sides are sealed using wrap around plastic, whilst top and bottom have a hexagonal shaped wax paper. Total weight is now 40g. The enclosure co-rotates with the device. When power is switched on, this device slows down from 1rev/5seconds to 1rev/14 seconds. The final velocity is reached much slower than the un-enclosed version, due to the added extra weight of the enclosure. Eventually the device comes to a rest, showing that the braking force is not interacting with the external air.
Measuring increase in inertia electronically (10/06/02)
The above experiments showed that there is an increase in inertia within a high voltage electric field. However, since the setup is of a mechanical nature, there have been several arguments mainly involving ion flow interactions with external air which cannot be ruled out by any mechanical setup. In view of these arguments, a completely electronic setup, with no moving parts or sensors, has been developed in order to measure the actual increase in inertia.
Since the ST dimensions of inertia (T3 S-1) are highly related to permeability (T3 S-4), one can electronically measure inertia by measuring the permeability in the volume of space under study.
The above design detects changes in permeability down to at least a fraction of 0.001% of ambient air permeability. To measure changes in permeability, the coil Ls, is inserted within the electric field under study, and by comparing the readings obtained with hv power on and hv power off, the modified permeability can be worked out. To measure changes in permittivity, the capacitor Cs is inserted in the air gap. The circuit is based on a frequency reading and thus is totally immune to voltage induction at the coil.
Results of this experiment show that when an asymmetric field of 20 kV is supplied across 40 mm, a change in permeability of -0.03% relative to that of air is generated within the electric field lines, and is maintained as long as the electric field is present. Permittivity measurements gave similar results. This backs up the above two 'mechanical' experiments, which show that an electric field gradient can modify inertia within a volume of dielectric.
Since speed of light depends only on permittivity & permeability of the medium, a change in both these parameters signifies a change in the speed of light across the medium, hence a change in refractive index.
The above circuit consists of two oscillators driven by Q1 and Q3. Q1 frequency is set fixed by the 5.5Mhz ceramic filter. Q3 frequency is set by both LSense & CSense. Q2 is used as a mixer, whose output frequency is the sum and difference of both oscillators. The output is then followed by a low pass filter and rectification, to pass the difference signal only. It is then fed to an oscilloscope, or may be heared by a crystal earpiece, or even fed to an audio amplifier. The circuit has first to have LSense, or CSense, manually set in order to get a resonance at 5.5Mhz, at which the output beat frequency is zero. Any change in permittivity is detected by CSense, whilst any change in permeability is sensed by LSense. The output is in the form of low frequency sinewaves, with their frequency depending on the change of the LC resonant circuit. This is then rectified by D1 & D2 and low pass filtered to give a dc voltage that can be read directly by a voltmeter.
This circuit can be used to detect a lot of other interesting parameters, including time shift, gravity effect on tuned circuits and lots more. Note that due to the fact that the LC circuit is inherently temperature dependent, this circuit should not be used for long term logging. However it gives very good results when testing fast changing conditions...such as conditions before and after switching on a lifter.
The Electrorheological/Winslow Effect - explaining the change in air 'viscosity'
The electrorheological (ER) effect is usually used to describe an effect in a class of liquids which stiffen into a semi-solid when subjected to an electric field. A simple ER setup consists of a mixture of cornflour and oil. Cornflour and oil do not conduct electricity - they are non-polar molecules with an even +ve / -ve charge distributed throughout them. But when cornflour is placed within an electric field, the molecules of the substance become polarised - the charges shift so that one part of the molecule is +ve, and another part is -ve. For the cornflour / oil mixture to flow, the oil must flow and the cornflour molecules must flow with the oil and over each other. However by introducing the mixture to an electric field, the cornflour molecules became polarised and started to stick together in long strands (the opposite charges on the molecules becoming attracted to each other). These long strands then constricted the movement of the oil. The whole thing then became more viscous and unable to flow!
More practical ER fluids (ERF's) consist of colloidal suspensions, and their stiffening under an electric field is instantly reversible. Under the electric field, ER fluids form fibrous structures, in a similar fashion to the cornflour chains, which are parallel to the applied electric field and can increase in viscosity by a factor of up to 105. The stiffening of an electrorheological fluid is sometimes called the Winslow effect after its first investigator, Willis Winslow in 1949. ERF's can be characterized by their Mason number. Even though air and other common fluids are not usually listed as ER fluids, due to their small increase in viscosity, it does not mean that the effect is not present. The effect also depends on the applied electric field which is very high in our experiment. Such strong electric field is thus making the effect big enough to be mechanically detected. The air between the outer electrodes of the thruster is thus forming invisible fibrous ionic structures, increasing the viscosity of the air itself, and thus slowing down the rotational motion. These invisible fibrous structures can in fact be visualised using Schlieren photography, which detects changes in refractive index dn/dx. The refractive index in air is also a function of air density, the higher the index the denser is the air. And higher density means a larger mass per unit volume, which supports our mass redistribution effect shown in our experiment. The photo below is the evidence of these dense air structures present between the thrusters electrodes which are slowing down the rotational motion.
The Dielectrophoresis Effect - explaining the change in permittivity & space-time distortion
Dielectrophoresis is the term used to describe the polarisation and associated motion induced in particles by a non-uniform electric field. The phenomenon arises from the difference in the magnitude of the force experienced by the electrical charges within an unbalanced dipole, induced when a non-uniform electric field is applied. In a non-uniform field, the convergence of the field lines encourages uneven charge alignment and formation of an induced dipole moment. The result is an imbalance in force upon the particle, enabling it to migrate toward the region of greatest field intensity, such as an electrode, determined by dielectric properties of the particles and suspending medium. The dielectrophoretic force, F, is given by the following general expression:
where is the effective polarisability of the particle, E is the electric field, is the del vector operator and v is the particle volume. This equation shows that the force is zero except in areas where the field is non-uniform.
For a homogeneous sphere (having no net charge) of radius r, the dielectrophoretic force is given by the following equation:
where is the medium permittivity, and and are the complex permittivities of the medium and particle. If our particles are air molecules, the medium is vacuum. So air has to be considered as being made up of gas molecules, suspended in vacuum. The complex permittivity is defined by:
where and are the permittivity and conductivity, and is the angular frequency of the electric field .
The term Re[ ] denotes the real component of the function of complex permittivities within the parentheses. This term may vary between -0.5 and +1, determined by the properties of the medium and the moving particle. If this is positive, the force exerted upon the particle will be positive and the particle will move towards areas of high electric field gradient - positive dielectrophoresis. If this is negative, the force exerted upon the particle will also be negative, and the particle will move towards areas of lowest electric field gradient - negative dielectrophoresis.
In the case of air within this non linear gradient, each type of minority gas molecules (refered to a particles) has to be considered moving in a sea of majority gas molecules (refered to as the medium). The situation is analogous (and perhaps the same!) to an object in water. If it's density is less than that of water it floats up, but if higher, it sinks down under the force of the non-linear gravity field gradient. If there is no gravity field gradient, the object neither floats nor sinks.
Positive dielectrophoresis leads to an attractive force, actively holding the particles in the areas where field gradient is at a maximum, at the sharpest electrode. Negative dielectrophoresis, however, is a repulsive force, and once the particles have been repelled to areas of zero or lowest field gradient, there will no longer be any dielectrophoretic force exerted upon them. At that point, Brownian effects and Stokes drag caused by fluid flow will determine any motion of the particle. In other words, the particles are released to the ambient once they reach the lowest field gradient. The resulting population of air molecules will thus be configured with gas components having high dielectric constant near the sharp electrode, and those with low K near the smoother electrode.
Although this effect may explain the change in inertia, permittivity and density gradient in the air gap, it does not contribute to the actual thrusting force of these EHD devices.
Dry air is mainly composed as follows (Permittivity ordered):
|Element trace||Percentage in air||Density at 273K 1atm||Permittivity @ 293K 1atm|
|Carbon Dioxide||0.03%||1.977 g/L||1.00098|
Thus if one considers the electric field gradient in a lifter, with its high electric field gradient near the top wire, one would measure an increase in K in the region very near the wire, but an overall lower K in the rest of the lower electric field gradient. The resulting permittivity must also reflect this mechanism, and so, permittivity across the air gap will decrease from the highest dielectric constant gas present in dry air (Carbon Dioxide 1.00098) near the sharp electrode to the nominal dielectric constant of the lowest K gases in air, with K closer to that of vacuum (1.0000).
So a change of -0.05% in permittivity would mean that all high K gases are distrubuted around the wire, leaving the air gap filled with low K gases only. As you see in my permittivity electronic measurement experiment, the reading was of 0.03% decrease in permittivity, confirming that a volume of low K or low density air is being created within the lower part of the airgap in lifters. This mechanism, resulting from the dielectrophoresis phenomena, describes how a structure of electrodes, maintaining a non-uniform asymmetric electric field gradient, can generate a non-linear permittivity gradient of air particles by the creation of a K-stratified air.
The resulting effect is an accelerating force on neutral gas molecules which leaves the same molecules in their original uncharged, non-ionic state (unless they get in direct contact with the electrodes) in all respects similar to gravity! This force only acts momentarily during charge build up and does not contribute to the observed thrust. It is interesting to note that the denser gases are normally those with higher K, and in the case of having the sharpest electrode fixed vertically above the smoother one, the resulting gas distribution will be opposite to that taken under normal gravity effect, that is the lightest gases will settle below the heavy ones. This means that within the air gap, the gas components will be under the effect of an artificial gravity, with the heaviest components 'falling' towards the sharp electrode and the lightest floating up to the smoother one. We know that gravity is equivalent to space-time bending, which makes such a configuration of electrodes exhibit space-time modification, and thus a potential candidate for anti-gravity mechanisms. This artificial gravity effect has been proved by NASA GFFC artificial gravity cell in a much similar way, although they do not put a clear explanation of its function, other than a weird electrostatic effect resembling gravity.
As you might have recognised, this dielectrophoresis effect is just obeying the underlying space-time distortion due to the non-linear electric field.
Air conductivity gradient
It has been shown that the asymmetric electric field gradient generates the dielectrophoresis effect, a direct consequence of gradients of permeability and permittivity over the path between the electrodes. As you know, the impedance of any dielectric is also dependent on its permeability and permittivity, and one would therefore expect a gradient of air conductivity over the same path. I have already described how particular gas molecules would vary in their proportion to the total number of molecules in air, depending on the position within the air gap. Carbon dioxide would tend to concentrate around the sharp electrode since it has the highest permittivity. Below is a table showing how conductivity of air changes with different parts per million of Carbon dioxide molecules in air. This agrees with the fact that the most conductive air is present around the sharpest electrode, where a high percentage of carbon dioxide molecules are present. So, apart from a permittivity and permeability gradient, we also have a conductivity gradient.