214 lines
11 KiB
Plaintext
214 lines
11 KiB
Plaintext
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| File Name : MHDAERO.ASC | Online Date : 09/09/95 |
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| Contributed by : InterNet | Dir Category : GRAVITY |
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| From : KeelyNet BBS | DataLine : (214) 324-3501 |
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| KeelyNet * PO BOX 870716 * Mesquite, Texas * USA * 75187 |
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| A FREE Alternative Sciences BBS sponsored by Vanguard Sciences |
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| InterNet email keelynet@ix.netcom.com (Jerry Decker) |
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| 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
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read ALTSCI1.ASC, see anything intriguing?..........................>>> Jerry
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From: pstowe@ix.netcom.com (Paul Stowe)
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Newsgroups: alt.paranet.ufo,alt.alien.visitors
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Subject: Magnetohydrodynamic (MHD) Operations
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Date: 7 Sep 1995 01:59:51 GMT
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MAGNETO-HYDRODYNAMIC (MHD) AERODYNES
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Based on an article written by
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Jean-Pierre Petit
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Claude Poher
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Maurice Viton
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Magneto-Hydrodynamics
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Magneto-Hydrodynamic (MHD) devices have been studied extensively during the
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last 15 years (as of 1974). Such devices can function either as a generator
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or as an accelerator. The MHD generators are known to deliver high power
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densities. With MHD generators one can obtain high specific impulses. But
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there are very diffieult basic problems connected with MHD processes.
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First, the low electrical conductivity of gases requires either seeding or the
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use of quite a large electronic temperature. Secondly, strong interactions
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require a high magnetic field. These two faetors create severe technological
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difficulties. At present, magnets of several Teslas strength can be built,
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using the techniques of superconductivity. Another problem is the production
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of electrodes which can carry large current densities. In the following
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discourse we will assume that such technological problems can be solved.
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Suppose now that very powerful electrical generators are available; could MHD
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flight be possible?
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General MHD Propulsion
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Faraday-type MHD accelerators are well-known. In such devices a linear
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channel is conbined with a magnet and a series of electrodes, segmented in
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order to obtain a more homogeneous electric discharge in the channel. In such
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accelerators, air is moved through the channel by Lorentz forces. Thus it
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would be possible to substitute MHD accelerators for the four engines of the
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supersonic "Concorde". This would require a total electric power of 200
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megawatts. If one can design light but powerful electrical generators, then
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MHD flight becomes possible. Let us suppose that an electrical generator
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weighing 10 tons and generating 490 to 4000 megawatts is available.
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The Cylindrical MHD Aerodyne
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If a large amount of energy is available, Lorentz forces can be used to
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produce both thrust and lift. Consider a cylinder, made of an insulating
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material, in which a solenoid produces a dipolar magnetic field. Pairs of
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electrodes are located on each side of the cylinder and connected to the
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electrical generator, creating a glow discharge in the surrounding air.
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The current intensity vector J is perpendicular to the magnetic field B.
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Hence, in the vicinity of the electrodes, where the current density is
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greatest, the Lorentz force is tangential. This in turn induces a flow in the
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surrounding medium. We have obtained experimental verification of these
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effects using a model of 35 mm. diameter in an electrolytic solution of water
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and HCl, with a 200 Gauss magnetic field and a 0.8 ampere electric current.
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The Lorentz forces tend to produce a realignment of the flow behind the
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cylinder. As a matter of fact, there is no wake and the flow appears to be
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laminar everywhere. Since there is no disturbance behind the cylinder, we see
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that the trihedra (J, E, and J X B ) rotates so as to maintain the
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tangential force in the desired direction.
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Spherical MHD Aerodyne
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Now it seems logical to shift to a spherical areodyne. We shall use a pair of
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electrodes and again, a dipolar magnetic field. Here again the Lorentz forces
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produce a lift. If we use a more symetrical system, we can place the
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electrodes in a circular belt around the sphere, each half of a pair being
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placed diametrically opposite the other half. The electric generator is
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connected to only one pair of electrodes at a time, in sequence. To complete
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this sequential operation, an internal series of solenoids provides a rotating
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magnetic <20>field.
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It is highly probable that the flow of the surrounding medium will be similar
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to the flow associated with the cyllndrical version. The air flow pattern
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modifies the distribution of the static pressure on the surface of the sphere
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resulting in lift. We know that the Lorentz forces can act very powerfully in
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a fluid.
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Experiments have been carried out in which these forces have produced very
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strong shock waves. With sufficient magnetic field and electric current, one
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can expect a very large amount of lift. Lorentz forces depend upon both J
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(the current density) and B (the magnetic field) and the following equations
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show that creation of a glow discharge in air requires high voltages and high
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current densities, resulting in high losses from the Joule effect and
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radiation. If we try to increase the magnetic field we approach a critical
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value at which the hall effect becomes important.
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The Hall Effect
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The gyrofrequency is defined as:
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W_e = eB/m_e Where e = elemental charge
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B = intensity of the
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magnetic field
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m_e = mass of the electron
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The collision frequency for the electron species can be defined as:
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V_e = SUM(s <> e) n_s Q_es T Where N-e = density number of a heavy
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species, ions or neutral
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Q_es = collision cross section e X s
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T = sqrt(8kT_e/pi m_e)
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k = Boltzmann's constant
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T_e = electronic temperature
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The electric field E acts on electrons. If the gyrofrequency is small
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compared to the collision frequency, the average movement of the electron will
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be linear and parallel to E. In e X s collisions we can consider that all the
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drift velocity of the electron is anihilated. In effect, in such collisions
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the velocity of the electrons is randomly distributed over all directions of
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space.
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If the gyrofrequency reaches the order of magnitude of the collision
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frequency, there is a transveres drift motion of the electrons. The preceding
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is very well described in Sutton and Sherman, ENGINEERING MHD, 1967.
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Proceding, we can now define a critical non-dimensional parameter, called the
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"Hall Parameter", as follows:
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b = W_e/V_e = TAN (theta) Where theta is the angle between J and E
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The relationship between J and the field E is no longer scalar:
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J = sigma dot E
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The electrical conductivity becomes tensorial, tensorial, as shown in the
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matrix below;
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| A -C 0 | A = eta/(eta + b^2)
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sigma = | C A 0 | C = b/(eta + b^2)
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| 0 0 eta |
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sigma is the "scalar" electrical conductivity (i.e. with zero magnetic field)
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Let us return to the cylindrical and spherical aerodynes. These are no longer
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practical. As a matter of fact, a component of the Lorentz force, normal to
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the surface, appears in the vicinity of the electrodes. We must seek other
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configurations for our model, NAMELY, A DISC.
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=========== Updated Data (NOT VERBATIM ORIGINAL TEXT) ==========
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In a disc shaped aerodyne, made of insulating material, with two belts of
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electrodes, one around the top, the other around the bottom. An electric
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discharge is produced in the surrounding air and upper and lower equatorial
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solenoid magnets produces an axial magnetic field.
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As a starting simplification, consider a disc shaped like two Fedora hats one
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inverted and placed below (centered) the other. The electrodes consist of
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rectangular sections ringed around the center of the main rising section (Not
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the brim) of both sections.
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The flow of electricity (Plasma) goes from the bottom electrodes to the top
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electrode radially around the disc brim. During night time operations the
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resulting plasma exhibits a glow out to about two radii of the disc.
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The luminosity is strongest at the electrodes, where the current density is
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greatest, and the electrodse can take on the appearance of windows. The
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colour of the glow is directly related to temperature of the plasma generated.
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When the magnetic field is introduced, we get a spiral current pattern. The
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electric current lines are twisted as actual experiments have confirmed.
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A check of the Lorentz forces demonstrate that if the Hall Effect is strong,
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the resulting Lorentz will tend to straighten "make radial" the twists
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mentioned above. The twist is reversed on the bottom section of the disc.
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The induced flow of air/plasma is very similar to that around a helicopter.
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Such MHD craft operations are very similar to those of a helicopter.
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In atmospheric air, the value of the main solinoidal magnetic field required
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to produce the Hall effect is is quite high (Greater that 500,000 Gauss)
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necessitating a superconducting coil.
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To obtain proper operation in a air (dielectric) medium requires a high
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electron density in the plasma. Saha's law can be used to compute the
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required thermodynamic conditions. This law can produce very good results for
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electron temperatures greater than 4000 degrees K, when total particle density
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exceeds 10^14/cc, and plasma dimensions are greater than 1 centimeter.
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Utilizing it, it is possible to compute electron density.
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Due to these high electron density values, these type of craft are operated in
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a pulse mode. This pulse mode generates electrical pulses of .between 10^11
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and 10^13 watts. Typical operating parameters are listed below:
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Volts: 450,000 to 800,000
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Amps: 10^7 to 10^9 Peak and 10^4 to 10^6 Averaged
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Magnetic Flux (B): 500,000 to 600,000 sustained in main ring
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Magnetic Flux (B): 600,000 to 800,000 Pulsed in steering assemblies
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(3 equilateral straddled centerline)
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The pulses are of one microsecond duration with an operational frequency of 5
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to 1 milliseconds. with sustained power requirement of 75 MW. To obtain the
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proper current carrying capacity in air, the air in the local vicinity of the
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craft's surface must be ionized. To accomplish this, a toroidal "cyclotron"
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soft X-Ray emitter is provided on both the upper and lower surfaces at the
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interface (brim and hat) surface.
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------------------------------------------------------------------------------
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