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| File Name : MHDAERO.ASC | Online Date : 09/09/95 |
| Contributed by : InterNet | Dir Category : GRAVITY |
| From : KeelyNet BBS | DataLine : (214) 324-3501 |
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| InterNet email keelynet@ix.netcom.com (Jerry Decker) |
| Files also available at Bill Beaty's http://www.eskimo.com/~billb |
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Another exceedingly good file from the InterNet....read this carefully, then
read ALTSCI1.ASC, see anything intriguing?..........................>>> Jerry
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From: pstowe@ix.netcom.com (Paul Stowe)
Newsgroups: alt.paranet.ufo,alt.alien.visitors
Subject: Magnetohydrodynamic (MHD) Operations
Date: 7 Sep 1995 01:59:51 GMT
MAGNETO-HYDRODYNAMIC (MHD) AERODYNES
Based on an article written by
Jean-Pierre Petit
Claude Poher
Maurice Viton
Magneto-Hydrodynamics
Magneto-Hydrodynamic (MHD) devices have been studied extensively during the
last 15 years (as of 1974). Such devices can function either as a generator
or as an accelerator. The MHD generators are known to deliver high power
densities. With MHD generators one can obtain high specific impulses. But
there are very diffieult basic problems connected with MHD processes.
First, the low electrical conductivity of gases requires either seeding or the
use of quite a large electronic temperature. Secondly, strong interactions
require a high magnetic field. These two faetors create severe technological
difficulties. At present, magnets of several Teslas strength can be built,
using the techniques of superconductivity. Another problem is the production
of electrodes which can carry large current densities. In the following
discourse we will assume that such technological problems can be solved.
Suppose now that very powerful electrical generators are available; could MHD
flight be possible?
General MHD Propulsion
Faraday-type MHD accelerators are well-known. In such devices a linear
channel is conbined with a magnet and a series of electrodes, segmented in
order to obtain a more homogeneous electric discharge in the channel. In such
accelerators, air is moved through the channel by Lorentz forces. Thus it
would be possible to substitute MHD accelerators for the four engines of the
supersonic "Concorde". This would require a total electric power of 200
megawatts. If one can design light but powerful electrical generators, then
MHD flight becomes possible. Let us suppose that an electrical generator
weighing 10 tons and generating 490 to 4000 megawatts is available.
The Cylindrical MHD Aerodyne
If a large amount of energy is available, Lorentz forces can be used to
produce both thrust and lift. Consider a cylinder, made of an insulating
material, in which a solenoid produces a dipolar magnetic field. Pairs of
electrodes are located on each side of the cylinder and connected to the
electrical generator, creating a glow discharge in the surrounding air.
The current intensity vector J is perpendicular to the magnetic field B.
Hence, in the vicinity of the electrodes, where the current density is
greatest, the Lorentz force is tangential. This in turn induces a flow in the
surrounding medium. We have obtained experimental verification of these
effects using a model of 35 mm. diameter in an electrolytic solution of water
and HCl, with a 200 Gauss magnetic field and a 0.8 ampere electric current.
The Lorentz forces tend to produce a realignment of the flow behind the
cylinder. As a matter of fact, there is no wake and the flow appears to be
laminar everywhere. Since there is no disturbance behind the cylinder, we see
that the trihedra (J, E, and J X B ) rotates so as to maintain the
tangential force in the desired direction.
Spherical MHD Aerodyne
Now it seems logical to shift to a spherical areodyne. We shall use a pair of
electrodes and again, a dipolar magnetic field. Here again the Lorentz forces
produce a lift. If we use a more symetrical system, we can place the
electrodes in a circular belt around the sphere, each half of a pair being
placed diametrically opposite the other half. The electric generator is
connected to only one pair of electrodes at a time, in sequence. To complete
this sequential operation, an internal series of solenoids provides a rotating
magnetic ˇfield.
It is highly probable that the flow of the surrounding medium will be similar
to the flow associated with the cyllndrical version. The air flow pattern
modifies the distribution of the static pressure on the surface of the sphere
resulting in lift. We know that the Lorentz forces can act very powerfully in
a fluid.
Experiments have been carried out in which these forces have produced very
strong shock waves. With sufficient magnetic field and electric current, one
can expect a very large amount of lift. Lorentz forces depend upon both J
(the current density) and B (the magnetic field) and the following equations
show that creation of a glow discharge in air requires high voltages and high
current densities, resulting in high losses from the Joule effect and
radiation. If we try to increase the magnetic field we approach a critical
value at which the hall effect becomes important.
The Hall Effect
The gyrofrequency is defined as:
W_e = eB/m_e Where e = elemental charge
B = intensity of the
magnetic field
m_e = mass of the electron
The collision frequency for the electron species can be defined as:
V_e = SUM(s <> e) n_s Q_es T Where N-e = density number of a heavy
species, ions or neutral
Q_es = collision cross section e X s
T = sqrt(8kT_e/pi m_e)
k = Boltzmann's constant
T_e = electronic temperature
The electric field E acts on electrons. If the gyrofrequency is small
compared to the collision frequency, the average movement of the electron will
be linear and parallel to E. In e X s collisions we can consider that all the
drift velocity of the electron is anihilated. In effect, in such collisions
the velocity of the electrons is randomly distributed over all directions of
space.
If the gyrofrequency reaches the order of magnitude of the collision
frequency, there is a transveres drift motion of the electrons. The preceding
is very well described in Sutton and Sherman, ENGINEERING MHD, 1967.
Proceding, we can now define a critical non-dimensional parameter, called the
"Hall Parameter", as follows:
b = W_e/V_e = TAN (theta) Where theta is the angle between J and E
The relationship between J and the field E is no longer scalar:
J = sigma dot E
The electrical conductivity becomes tensorial, tensorial, as shown in the
matrix below;
| A -C 0 | A = eta/(eta + b^2)
| |
sigma = | C A 0 | C = b/(eta + b^2)
| |
| 0 0 eta |
sigma is the "scalar" electrical conductivity (i.e. with zero magnetic field)
Let us return to the cylindrical and spherical aerodynes. These are no longer
practical. As a matter of fact, a component of the Lorentz force, normal to
the surface, appears in the vicinity of the electrodes. We must seek other
configurations for our model, NAMELY, A DISC.
=========== Updated Data (NOT VERBATIM ORIGINAL TEXT) ==========
In a disc shaped aerodyne, made of insulating material, with two belts of
electrodes, one around the top, the other around the bottom. An electric
discharge is produced in the surrounding air and upper and lower equatorial
solenoid magnets produces an axial magnetic field.
As a starting simplification, consider a disc shaped like two Fedora hats one
inverted and placed below (centered) the other. The electrodes consist of
rectangular sections ringed around the center of the main rising section (Not
the brim) of both sections.
The flow of electricity (Plasma) goes from the bottom electrodes to the top
electrode radially around the disc brim. During night time operations the
resulting plasma exhibits a glow out to about two radii of the disc.
The luminosity is strongest at the electrodes, where the current density is
greatest, and the electrodse can take on the appearance of windows. The
colour of the glow is directly related to temperature of the plasma generated.
When the magnetic field is introduced, we get a spiral current pattern. The
electric current lines are twisted as actual experiments have confirmed.
A check of the Lorentz forces demonstrate that if the Hall Effect is strong,
the resulting Lorentz will tend to straighten "make radial" the twists
mentioned above. The twist is reversed on the bottom section of the disc.
The induced flow of air/plasma is very similar to that around a helicopter.
Such MHD craft operations are very similar to those of a helicopter.
In atmospheric air, the value of the main solinoidal magnetic field required
to produce the Hall effect is is quite high (Greater that 500,000 Gauss)
necessitating a superconducting coil.
To obtain proper operation in a air (dielectric) medium requires a high
electron density in the plasma. Saha's law can be used to compute the
required thermodynamic conditions. This law can produce very good results for
electron temperatures greater than 4000 degrees K, when total particle density
exceeds 10^14/cc, and plasma dimensions are greater than 1 centimeter.
Utilizing it, it is possible to compute electron density.
Due to these high electron density values, these type of craft are operated in
a pulse mode. This pulse mode generates electrical pulses of .between 10^11
and 10^13 watts. Typical operating parameters are listed below:
Volts: 450,000 to 800,000
Amps: 10^7 to 10^9 Peak and 10^4 to 10^6 Averaged
Magnetic Flux (B): 500,000 to 600,000 sustained in main ring
Magnetic Flux (B): 600,000 to 800,000 Pulsed in steering assemblies
(3 equilateral straddled centerline)
The pulses are of one microsecond duration with an operational frequency of 5
to 1 milliseconds. with sustained power requirement of 75 MW. To obtain the
proper current carrying capacity in air, the air in the local vicinity of the
craft's surface must be ionized. To accomplish this, a toroidal "cyclotron"
soft X-Ray emitter is provided on both the upper and lower surfaces at the
interface (brim and hat) surface.
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