Abstract: A system for uniformly distributing propellant gas in a Hall-effect thruster (10) (HET) includes an anode (42, 42′) and a porous material gas distributor (60, 89) (PMGD). The porous material (120) may be porous metal or porous ceramic. Propellant gas is directed from a supply to the PMGD for distribution into a gas discharge region (16) of the HET (10). The gas flows through the porous material (120) of the PMGD and out of the PMGD's exit surface (71) into the annular gas discharge region (16). The PMGD has an average pore size, pore density and thickness that are optimized to control the flow of the gas at the desired flow rate and distribution uniformity at a relatively short distance downstream from the PMGD. This feature allows HET to be short, significantly decreasing susceptibility to vibration problems encountered during vehicle launch. The PMGD can include a shield (79, 80) for preventing contaminants from traveling upstream from the gas discharge region from adhering to the porous metal.

Abstract: The invention provides an improved spacecraft thruster, either Hall effect or ion effect, using gaseous propellant converted from solid iodine. A heated tank contains iodine crystals, which tank connects to a thrust chamber by a feed tube. A filter is mounted at the input end of the feed tube, proximate the tank, which filter is warmed by a heat control. A mass flow controller is mounted in the feed tube between the tank and the chamber and is heated by a temperature controller, such controller having a shut-off valve and means to control the flow rate of gaseous propellant to the thruster chamber.

Abstract: A satellite power distribution method for efficiently distributing power to satellite electric propulsion thrusters (24) is provided. The satellite includes spacecraft loads (20), an electric propulsion thruster (24), thruster auxiliary circuits (22), and a first power transformer (30). The first power transformer (30) has a primary winding (32) coupled to a first energy source (12) that supplies satellite power. A first secondary winding (36) of the first power transformer (30) is coupled to the spacecraft loads (20) for supplying primary power. The power distribution method includes the steps of first coupling a second secondary winding (34) to the first power transformer (30) for converting the satellite power to thruster discharge power which is rectified. The rectified discharge power is filtered to obtain power that is supplied to the electric propulsion thruster (24). Finally, satellite power is converted to auxiliary power for powering the thruster auxiliary circuits (22).

Abstract: An air/atmosphere breathing electrically powered Hall effect thruster including a thruster duct having an inlet, an exit, and a discharge zone between the inlet and the exit for receiving air from the inlet into the discharge zone, an electrical circuit having a cathode for emitting electrons and an anode in the discharge zone for attracting the electrons from the cathode through the exit, and a magnetic circuit for establishing a magnetic field in the discharge zone radially across the duct between the anode and exit which creates an impedance to the flow of electrons toward the anode and enables ionization of the air/atmosphere moving through the discharge zone and which creates an axial electric field in the duct for accelerating ionized air/atmosphere through the exit to create thrust.

Abstract: For a plasma accelerator arrangement in particular for use as an ion thruster in a spacecraft, a structure is proposed in connection with which an accelerated electron beam is admitted into an ionization chamber with fuel gas, and is guided through the ionization chamber in the form of a focused beam against an electric deceleration field, said electric deceleration field acting at the same time as an acceleration field for the fuel ions produced by ionization. The arrangement generates a focused beam of a largely neutral plasma with a high degree of efficiency. Configurations for electric and magnetic fields for guiding and focusing the beams are given by way of example.

Abstract: A micro-colloid thruster system may be fabricated using micro electromechanical system (MEMS) fabrication techniques. A beam of charged droplets may be extracted from an emitter tip in an emitter array by an extractor electrode and accelerated by an accelerator electrode to produce thrust. The micro-colloid thruster system may be used as the main propulsion system for microspacecraft and for precision maneuvers in larger spacecraft.

Abstract: A series of long slats, preferably parallel and spaced apart uniformly, extend from a base plate to form a series of cavities between the slats for trapping high energy ions in the exit plume of an ion accelerator. The plume shield is designed to minimize escape of ions and sputtered atoms from the shield. The effectiveness of the shield in trapping and retarding ions and sputtered atoms can be accomplished by biasing the potential of the shield with respect to an adjacent structure and by inducing a magnetic field parallel to a target area of the shield, which can limit electron current to the target area.

Abstract: A linear gridless ion thruster (LGIT) is provided to serve as an ion source for spacecraft propulsion or plasma processing. The LGIT is composed of two stages: (1) an ionization stage composed of a hollow cathode, anode, and cusp magnetic field circuit to ionize the propellant gas; and (2) an acceleration stage composed of a downstream cathode, upstream anode, and a radial magnetic field circuit to accelerate ions created in the ionization stage. The LGIT replaces grids used in conventional ion thrusters (Kaufman guns) to accelerate ions with Hall-current electrons as in the case with conventional Hall thrusters.

Abstract: Thrust is provided to a vehicle using a self-contained device for producing the thrust through a preselected shaping of an electric field. The device includes a core carried by a housing, with both the core and the housing formed from a material having a high dielectric constant. Multiple cells are carried by the housing and formed around the core, with each cell having a high dielectric sandwiched between an electrode and a lower dielectric. A channel is formed between each cell with the channel providing a spacing filled with a material having a dielectric property of the lower dielectric. Electric wires are connected between an electrical power source and each electrode of each cell for providing power thereto. A set of cells extends radially outward from a longitudinal axis of a cylindrical core to form a circular plate with each cell uniformly positioned within the circular plate.

Abstract: A Hall effect electric propulsion system having an electromagnet with an internal acceleration chamber and an internal ionizer is disclosed. An aperture formed in one end of the electromagnet opens into the acceleration chamber. The magnetic poles of the electromagnet are positioned non-parallel in relation to each other on opposite sides of the aperture. The ionizer located within the acceleration chamber ionizes a flow of propellant molecules introduced into the acceleration chamber. An electron generator external to the electromagnet directs an electron beam towards an asymmetric magnetic field generated by the electromagnet about the throat. Electrons are trapped in a flux of the magnetic field to form an electron cloud, which functions as a phantom cathode.

Abstract: A pulsed Hall thruster system includes a Hall thruster having an electron source, a magnetic circuit, and a discharge chamber; a power processing unit for firing the Hall thruster to generate a discharge; a propellant storage and delivery system for providing propellant to the discharge chamber and a control unit for defining a pulse duration &tgr;<0.1d3&rgr;/{dot over (m)}, where d is the characteristic size of the thruster, &rgr; is the propellant density at standard conditions, and {dot over (m)} is the propellant mass flow rate for operating either the power processing unit to provide to the Hall thruster a power pulse of a pre-selected duration, &tgr;, or operating the propellant storage and delivery system to provide a propellant flow pulse of duration, &tgr;, or providing both as pulses, synchronized to arrive coincidentally at the discharge chamber to enable the Hall thruster to produce a discreet output impulse.

Abstract: A system for marine propulsion includes a metal fuel slurry, a water plasma, and a high alternating magnetic field. The magnetic field acts on the metal fuel to generate explosive momentum via a metal-water reaction. The reaction may also generate the water plasma. The magnetic field then acts on the water plasma using induction magnetohydrodynamic (“MHD”) pumping to generate MHD momentum. The explosive and MHD momenta propel the water through a water channel. The water may be used to propel marine vessels or to pump water.

Abstract: The present invention provides an ion engine, more particularly an ion engine using the inconsumable specialty of a super conductor to make the electromagnetic impulse generated thereby produce continuous and ceaseless energy; mainly, two gassed sides of a dynamo are disposed with super conductors; since the said super conductors have inconsumable specialty, the released high voltage therefrom influences the gas inside the dynamo to ionize and further generate continuous and endless electric current.

Abstract: A high-frequency ion source, in particular a high-frequency ion engine, includes a discharge chamber or container (2), a source (9) providing a gas to be ionized, a gas inlet (10) discharging the gas from the source into the discharge container (2) to be ionized therein, a high-frequency coil (3) surrounding the discharge container (2), and a high-frequency generator (4) connected to the high-frequency coil (3), for generating a high-frequency electromagnetic alternating field that ionizes the gas present in the discharge container (2). Furthermore, an acceleration grid (11) connected to an acceleration voltage source (12) is arranged at the open end of the discharge container (2) so as to accelerate the ions generated in the discharge container (2) in the form of an ion beam emanating from the discharge container (2). The shape of the discharge container (2) in longitudinal section is tapered to become smaller toward the closed end (6) opposite the open end (5) of the container.

Abstract: An ion thruster has a hollow cathode assembly including a heater with an inner ceramic sleeve and an outer ceramic sleeve. The outer ceramic sleeve overlies the inner ceramic sleeve with a filament volume between the two sleeves. A wound filament has windings disposed within the filament volume, and a mass of ceramic powder fills the remaining portion of the filament volume between the windings of the filament. A cathode is disposed within the inner ceramic sleeve of the heater. The heater is assembled by preparing the filament and forming it into a wound cylinder, and then encapsulating it and the powder between the inner and the outer ceramic sleeves. The hollow cathode assembly may serve as a portion of a plasma source or as a portion of a charge neutralizer.

Abstract: An ion thruster includes a source of a plasma of ions and electrons, and an ion-optics system located in sufficient proximity to the source of the plasma to extract ions therefrom. The ion-optics system has at least two domed grids arranged in a facing-but-spaced-apart relationship to each other. Each grid has a local reference vector that is perpendicular to the surface of the grid and a reference plane perpendicular to the reference vector. Each of the grids is formed of anisotropic pyrolytic graphite having an “ab” crystallographic plane that lies substantially in the reference plane. In one form, the “ab” crystallographic plane lies coplanar with the reference plane at all locations on each domed grid made of pyrolytic graphite. In another form, the “ab” crystallographic plane has a constant orientation at all locations on the domed grid.

Abstract: This invention provides a noble gas storage and delivery system for ion propulsion using an adsorption bed coupled with a primary storage vessel containing compressed gas or two-phase fluid to control the flow and pressure to a thruster component. The adsorption bed component is lighter weight than conventional flow and pressure control devices, and the system can provide in situ gas cleanup and stable flow from two-phase storage. The use of the adsorption bed allows for independent and isolated operation of multiple thruster components such as refill from the primary storage vessel, throttling, and multiple setpoint flow rates. The pressure and flow is controlled using a flow restrictor and low wattage heat. Flow rates of about 2-50 sccm can be controlled to within about 1.2% or less, and the flow can be throttled by varying the pressure. This noble gas storage and delivery system can be used for earth orbit satellites, and lunar or planetary space missions.

Abstract: A high pulse repetition frequency (PRF) plasma gun is provided, which gun inlets a selected propellant gas into a column formed between a center electrode and a coaxial outer electrode, utilizes a solid state high repetition rate pulse driver to provide a voltage across the electrodes and provides a plasma initiator at the base of the column, which is normally operative when the driver is fully charged. For preferred embodiments, the initiator includes a sold state simulated RF driver, the outputs from which are applied to electrodes affixed in an insulator and producing a high voltage field at a surface of the insulator which forms part of the base end of the column. The plasma expands from the base end of the column and off the exit end thereof.

Abstract: A thruster system includes a power supply and a pulse forming circuit coupled to the power supply. The pulse forming circuit includes a capacitor and first and second diodes. The positively-charged plate of the capacitor is coupled to the anode of the first diode, the negatively-charged of the capacitor is coupled to the anode of the second diode, and the cathode of the first diode is coupled to the cathode of the second diode. A low-impedance thruster is coupled in parallel to the second diode.

Abstract: A method and system for storing and delivering a noble gas for an ion propulsion system where an adsorbent bearing a noble gas is heated within a storage vessel to desorb the noble gas which is then flowed through a pressure reduction device to a thruster assembly. The pressure and flow is controlled using a flow restrictor and low wattage heater which heats an adsorbent bed containing the noble gas propellant at low pressures. Flow rates of 5-60 sccm can be controlled to within about 0.5% or less and the required input power is generally less than 50 W. This noble gas storage and delivery system and method can be used for earth orbit satellites, and lunar or planetary space missions.

Abstract: The closed electron drift plasma thruster uses a magnetic circuit to create a magnetic field in a main annular channel for ionization and acceleration, said magnetic circuit comprises: an essentially radial first outer pole piece; a conical second outer pole piece; an essentially radial first inner pole piece; a conical second inner pole piece; a plurality of outer magnetic cores surrounded by outer coils to interconnect the first and second outer pole pieces; an axial magnetic core surrounded by a first inner coil and connected to the first inner pole piece; and a second inner coil placed upstream from the outer coils. The thruster also comprises a plurality of radial arms included in the magnetic circuit, and a structural base which is separate from the magnetic circuit and which serves, amongst other things, to cool the coils.

Abstract: The thruster comprises, on a common plate, a plurality of main annular ionization and acceleration channels having axes that are not parallel and that converge in the outlet direction of the channels. A magnetic circuit sets up a magnetic field in the annular channels. The thruster also has a hollow cathode, a device for regulating the ionizable gas feed rate to each annular channel, and a device for controlling the ion discharge acceleration current in the channels. The direction of the thrust vector of the thruster can be controlled without significantly increasing the mass of the thruster.

Abstract: An ion thruster has a source of a plasma, and an ion-optics system located in sufficient proximity to the source of the plasma to extract ions therefrom. The ion-optics system includes at least two grids arranged in a facing-but-spaced-apart relationship to each other, with each grid being axisymmetric about a grid axis. Each grid includes a peripheral region defining a grid plane perpendicular to the grid axis, a first region of curvature adjacent to the peripheral region, and a second region of curvature along the grid axis such that the first region of curvature lies between the second region of curvature and the peripheral region. The first region of curvature is a convexly curved segment of a first sphere relative to the grid plane, and the second region of curvature is a concavely curved segment of a second sphere relative to the grid plane.

Abstract: In one embodiment of the present invention, the ion optics for use with an ion source have first and second electrically conductive grids having mutually aligned respective pluralities of apertures through which ions may be accelerated and wherein each has an integral peripheral portion. There is also a support member. There are first and second series of seats around the respective peripheral portions of the first and second grids. A plurality of first spherical insulators are distributed between seats of the first and second series, thereby establishing a predetermined distance between the grids while still enabling radial movement between their peripheral portions. There are third and fourth series of seats around the support member and the peripheral portion of the second grid, respectively, with seats of the fourth series displaced from those of the second series in the same grid.

Abstract: A pulse plasma thruster (50) utilizes a vapor producing solid (54) and a micro-sized heater (52) to produce a high pressure vapor that is directed into an ignition chamber (58) and to a thrust discharge chamber (70). The thrust discharge chamber (70) comprises two oppositely disposed electrode plates (72, 74) and oppositely disposed fuel propellants sources (60, 62). The passageway (56) leading from vapor producing solid (54) to the thrust discharge chamber (70) is configured to permit uniform feeding of the vapors to the thrust discharge chamber (70). A pair of electrode terminals (82, 84) extend from the electrode plates (72, 74) and through a housing (88). A power source (100) is coupled to the terminals (82, 84) and provides the ignition signals necessary to cause a spark and a breakdown to a useful plasma arc by controlling the voltage-current shape of the ignition signal.

Abstract: A specially designed magnetic shunt is provided encircling the anode region and/or annular gas distribution area of an ion accelerator with closed electron drift. The magnetic shunt is constructed to concentrate the magnetic field at the ion exit end, such that the location of maximum magnetic field strength is located downstream from the inner and outer magnetic poles of the accelerator. The specially designed shunt also results in desired curvatures of magnetic field lines upstream of the line of maximum magnetic field strength, to achieve a focusing effect for increasing the life and efficiency of accelerator. The anode of the accelerator can diffuse ionizable gas through a porous plate for an even distribution of the gas in the distribution area.

Abstract: A specially designed magnetic shunt is provided encircling the anode region and/or annular gas distribution area of an ion accelerator with closed electron drift. The magnetic shunt is constructed to concentrate the magnetic field at the ion exit end, such that the location of maximum magnetic field strength is located downstream from the inner and outer magnetic poles of the accelerator. The specially designed shunt also results in desired curvatures of magnetic field lines upstream of the line of maximum magnetic field strength, to achieve a focusing effect for increasing the life and efficiency of accelerator.

Abstract: An electrostatic ion propulsion engine for satellites and spacecraft is equipped with an electron source for neutralizing the propellant gas ion beam or jet emitted by the engine. The electron source includes an anode housing, a hollow cathode tube with gas flowing therethrough, a cathode element at the outlet end of the cathode tube within the interior space of the anode housing, and a pin- or rod-shaped auxiliary electrode arranged along the lengthwise axis in the hollow cathode tube. An ignition pulse is applied to the auxiliary electrode relative to the cathode tube, which causes a pulse discharge in the cathode tube, and in turn ignites the gas discharge between the anode and the cathode which generates the electron current.

Abstract: A traveling-field, magnetic propulsion system and operating method is provided for achieving economical space travel. The system is based upon designing the vehicle in the form of a single-stage streamlined circular toroidal airfoil containing a thin-walled superconducting solenoid. It is initially launched vertically off the earth's surface into a vacuum environment at 125 km using conventional rocket propulsion. It is then accelerated along a high-inclination trajectory by a traveling repulsive magnetic field generated by ejecting an easily ionizable low-density gas cloud in the vehicle's magnetic field and transmitting a high-power, plane-polarized, microwave beam at the cloud tuned to the electron cyclotron resonant frequency. The transmitter is constructed horizontally on the earth's surface as an electronically-steered, phased array several hundred meters in diameter energized by a large superconducting energy storage system.

Abstract: In drive circuitry for powering an arc jet or ion engine aboard a spacecraft carrying solar panels, a start-up circuit interconnects an array of series-parallel connected solar panels to establish and maintain an arc and plasma in the engine. In the start-up circuit, an electric switch is placed in parallel with an electrode assembly of the engine. One terminal of the engine connects directly with the solar panel array, and another terminal of the engine connects via an inductor to the solar panel array. A capacitor connects across terminals of the solar panel array. A series connection of solar panels increases the voltage from that which is available from a single panel. Conduction of current from the solar panel via the inductor is initiated by the switch to store magnetic energy within the conductor. Thereupon, upon an opening of the switch, the inductor produces a relatively high voltage which strikes an arc in the engine.

Abstract: The ion beam concentration apparatus for a plasma thruster having closed electron drift comprises:a) an essentially frustoconical flared magnetic pole piece (63) open at both ends and designed to be situated downstream from the outlet plane of a plasma thruster having an annular ionization and acceleration channel (1) and peripheral and central pole pieces (3, 4) disposed on either side of the annular channel (1) to produce an essentially radial magnetic field in an outlet plane (14) perpendicularly to the axis of the annular channel (1); andb) an additional peripheral magnetic circuit (60; 80) connecting the downstream end of the flared magnetic pole piece (63) to said peripheral pole piece (3), the flared magnetic pole piece (63) co-operating with the additional peripheral magnetic circuit (60; 80) and with the peripheral and central pole pieces (3, 4) to define the shape of the magnetic field downstream from the annular channel (1) in such a manner as to constrain the ion beam emitted by the annular channe

Abstract: A tandem Hall field plasma accelerator with closed electron drift includes a magnetic circuit having an inner pole and an outer pole and a magnetic field source and a discharge cavity disposed axially in tandem; the discharge cavity including an axially extending accelerator section defining an exit aperture between the inner and outer poles and a plenum section extending radially outwardly and upstream of the accelerator section and including an anode and a propellant injector. Also disclosed is the use of an electromagnetic coil which provides a magnetic field in a magnetic circuit and includes a multiple turn winding wound on an electrically conductive bobbin. The plasma discharge is connected electrically in series with the electromagnetic coil and a power source with a bobbin defining a single turn secondary coil winding on the magnetic circuit which reduces magnetic field fluctuations in the plasma discharge and reduces eddy currents and consequent heating of the magnetic circuit.

Abstract: An environmentally compatible propulsion system for low maintenance and long term durations at high altitudes is provided which is capable of utilizing high altitude ambient gas as fuel and producing ozone as a by-product of propulsion. The ion engine propulsion system ionizes a portion of an ambient atmospheric fuel to create a negative ionic plasma for bombarding and accelerating the remaining portion of the ambient atmospheric gas in a focused and directed path to an ion thruster anode. The novel ion engines provided create a negative ionic plasma between a cathode ion thruster and a ring-shaped anode in a housing composed of an electrical insulative material in which the cathode ion thruster is charged to -18 to -110 kilovolts (kv) to utilize ambient atmospheric gas as the propellant.

Abstract: An electrostatic ion jet source design, based on inertial electrostatic confinement technology. According to the invention, the inertial electrostatic confinement jet source employs a configuration that is compatible with the generation and acceleration of ions within a vacuum chamber. The device uses a unique spherical configuration, enlarged hole grid, channel guide grid and electron production/confinement method. The prior art designs have to produce a small diameter jet. Virtual cathode formation in a high-density region, combined with a locally distorted cathode grid potential field, extracts accelerated ions in an intense quasi-neutral ion jet. The device ejects matter with a jet form for use as an industrial plasma spray, industrial material processing, waste treatment, welding or cutting materials, or for plasma vapor deposition.

Abstract: A Hall field plasma accelerator with closed electron drift includes a composite anode including a housing with inner and outer walls which form an outer anode and an inner anode forming inner and outer distribution zones; the housing is electrically conductive and has an upstream end and an exit port electrically insulated from the housing; the composite anode includes an input distribution system for introducing plasma gas into the distribution zones; poles establish a magnetic field across the exit port and a cathode establishes an electron flow through the magnetic field toward the composite anode and creates an electric field through the exit port; the electrons ionize the plasma gas that is accelerated by the electric field through the exit port.

Abstract: The design and manufacturing processes for Hollow Cathode Assemblies (HCA that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere.

Abstract: In drive circuitry for powering an arc jet or ion engine aboard a spacecraft carrying solar panels, a start-up circuit interconnects an array of series-parallel connected solar panels to establish and maintain an arc and plasma in the engine. In the start-up circuit, an electric switch is placed in parallel with an electrode assembly of the engine. One terminal of the engine connects directly with the solar panel array, and another terminal of the engine connects via an inductor to the solar panel array. A capacitor connects across terminals of the solar panel array. A series connection of solar panels increases the voltage from that which is available from a single panel. Conduction of current from the solar panel via the inductor is initiated by the switch to store magnetic energy within the conductor. Thereupon, upon an opening of the switch, the inductor produces a relatively high voltage which strikes an arc in the engine.

Abstract: A single power control circuit selectively distributes power from a power supply to cathode heater, cathode keeper and thruster magnets of a thruster. The power control circuit utilizes a plurality of switching devices to direct power to one or more of the heater, keeper, and magnet components.

Abstract: Electrostatic propulsion systems for spacecraft include a plurality of electrostatic thrusters that are continuously coupled to power forms of a power supply system. Ionizable gas is fed to a selected one of the thrusters to selectively initiate the thrust of that electrostatic thruster. In other embodiments, heater power forms are coupled only to the selected thruster to reduce power consumption and increase cathode lifetime. The propulsion system has a reduced complexity and is especially suited for spacecraft in which only one thruster is ever fired at a given time.

Abstract: A closed electron drift ion source comprising a main annular channel for ionization and acceleration that is open at its downstream end, and that has at least an inside wall constituted by a material that is electrically conductive. Terminal parts taken to a potential that is lower than that of an anode extend the downstream end of the annular channel. The ion source also includes a hollow cathode, ionizable gas feed means associated with the cathode, and with the anode, anode bias means, and means for creating a magnetic field in the main annular channel. The invention is particularly applicable to industrial treatment methods.

Abstract: Ion erosion of grids is reduced in an ion thruster with a multiple-grid ion-optics system. The thruster has an array of aperture sets in which aperture areas change in a perimeter region of the array. In one ion-optics system embodiment, a screen aperture area is reduced and a decelerator aperture area is increased in aperture sets that are proximate to the perimeter of the array. Prototype tests of this embodiment have illustrated significant reduction of ion erosion.

Abstract: A plasma accelerator with closed electron drift comprising a dielectric discharge chamber (6) with internal and external annular walls (13) forming an annular accelerating channel, and a magnetic system with sources (3) of a magnetic field, a magnetic path (2), external (4) and internal (5) magnetic poles forming an operating gap in the region of the discharge chamber exit edges. An anode unit (7) with a gas distributor is located in the accelerating channel interior, and the distance from the anode-gas distributor (7) to the accelerating channel exit plane exceeds said channel width. A cathode-compensator (1) is located beyond the exit plane of the discharge chamber (6). Exit parts of the discharge chamber walls (13) facing the accelerating channel are made of conducting material. At least one dividing annular groove (12) is made on each chamber wall between its conducting and main parts.

Abstract: In a Hall effect thruster, especially for use in maneuvering satellites, a stream or plume of ions, used to produce the thrust is deflected, by appropriate adjustment of a magnetic field, so as to steer the satellite or other vehicle. The channel, along which the ions are accelerated, is preferably flared outwardly at its open end so as to avoid erosion which would otherwise be caused by the deflection. The adjustment of the magnetic field is preferably achieved by dividing an outer magnetic pole, surrounding the channel, into separate sectors and winding individual electric coils around the sectors. Control of the current through these individual coils is used to make the appropriate adjustments of magnetic field.

Abstract: An impregnating machine (1, 28) for surface impregnating hides (2) or similar products wherein an endless conveyor belt (3), with a transportation branch (5) traveling in a given direction (6), and a conveyor (16), presenting a number of endless belts (17), define a feed channel (19) for the hides (2); the feed channel (19) extending substantially up to a narrow passage (13) for the conveyor belt (3) and the hides (2); and the passage (13) being defined between an impregnating roller (11) and a deflecting member (7) facing the impregnating roller (11) and such as to impart to the transportation branch (5) of the conveyor belt (3) a radius of curvature (R1) equal to a relatively small fraction of the radius (R2) of the impregnating roller (11).

Abstract: A method for providing thrust to a space borne vehicle uses an ion beam current to deliver a continuous stream of mass to the vehicle. The mass stream is decelerated thereby transferring its momentum to the vehicle as thrust. The vehicle reaccelerates the mass stream projecting it back to it origin, and thus receives further thrust in reaction to the departing mass stream. The mass stream may be set up between two particle beam accelerators so that thrust is realized by both accelerators, or the beam may be merely received continuously by one accelerator. In both cases the thrust may be used for deep space acceleration to high velocities by a vehicle not carrying fuel or propellant and not near any natural energy source.

Abstract: A closed cycle gas turbine engine has sealed therein a working medium, within a working chamber, a closed exhaust manifold, a gas recirculating path, and a plasma gas generator, with a turbine rotor rotating within the working chamber. High voltage pulses of very brief duration are periodically applied to the plasma gas generator, causing electrical discharges to form a plasma in said working medium, thereby producing high pressure motive gas. Resultant flows of high-pressure motive gas drive the turbine rotor, providing a high level of output power from the engine with no consumption of a fuel. The pressure of the motive gas is reduced in the closed exhaust manifold and recirculated to the motive gas generator through the gas recirculating path for next electrical discharge. The engine is suitable for driving a mechanism such as a vehicle, machine etc.

Abstract: An ion thruster comprises a chamber in which propellant is ionized and an accelerator grid, whereby a flow of ions out of the chamber provides reactive thrust. Charge exchange between neutral atoms of propellant and fast moving ions produces slow ions which impact on the accelerator grid and erode it by sputtering, thus limiting the lifetime of the thruster. The invention includes an accelerator grid comprising a layer which includes graphite providing resistance to erosion and a support layer which overcomes the restrictions on engineering and strength of graphite. The accelerator grid can be constructed by machining a block of graphite 12 to produce an upper surface 13, to which the molybdenum grid 14 can be fixed. The block 12 can then be cut away to permit the graphite to be machined to the same contour as the surface 13. Apertures are drilled through the graphite using the existing apertures of the grid 14 as guides.

Abstract: A gas ionizable to produce a plasma is introduced into a channel within an ion source and into a hollow cathode embedded within the same ion source. A combined anode and manifold is located at a closed end of the channel and gas is introduced into the channel through the combined anode and manifold and into the hollow cathode. A heater and keeper electrode power supply is used to establish a hollow cathode and keeper electrode plasma. A discharge power supply is used to flow electrons from the hollow cathode in a predominately 180.degree. direction to bombard the channel gas distribution and create a channel discharge plasma. A magnetic field generated by a permanent magnet circuit is concentrated by pole pieces at the open end of the channel in an orientation predominately transverse to the channel axis. Energetic electrons from the hollow cathode interact with the concentrated field to simultaneously ionize the channel gas and accelerates these ions through the open channel to form an ion beam.

Abstract: The plasma accelerator comprises: a main annular channel (24) for ionization and for acceleration defined by parts (22) made of insulating material and open at its downstream end (225); at least one hollow cathode (40) associated with ionizable gas feed means (41); and an annular anode (25) concentric with the main annular channel (24) and disposed at a distance from the open downstream end (225). An annular buffer chamber (23) having a dimension in the radial direction which is greater than that of the main annular channel (24) extends upstream therefrom beyond the zone in which the annular anode (25) is placed. Ionizable gas feed means (26) open out upstream from the anode (25) via an annular manifold (27) into a zone distinct from the zone carrying the anode (25).

Abstract: Carbon-carbon grids for ion optics sets are thermomechanically stable under the extreme temperature changes that are experienced in ion thrusters. Screen, accelerator and decelerator grids are thermomechanically stable, lightweight, and resistant to erosion from ion sputtering and have extended lifetimes over conventional molybdenum grids.