Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03H—PRODUCING A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
  • F03H1/00—Using plasma to produce a reactive propulsive thrust
  • F03H1/0037—Electrostatic ion thrusters
  • F03H1/0062—Electrostatic ion thrusters grid-less with an applied magnetic field
  • F03H1/0075—Electrostatic ion thrusters grid-less with an applied magnetic field with an annular channel; Hall-effect thrusters with closed electron drift

Definitions

• the invention relates to the field of plasma thrusters, in particular Hall effect.
• Such motors can for example be used in space for example to maintain a satellite in geostationary orbit, or to operate a transfer of a satellite between two orbits, or to compensate for drag forces on satellites in low orbit, or again for missions requiring low thrust over very long times such as during an interplanetary mission.
• FIG. 1 represents an axial section of an example of such a thruster
• FIG. 2 represents a perspective view seen from the rear of said example of thruster.
• the propellant has substantially a form of revolution around an axis 00 '.
• the cutting plane of Figure 1 has this axis 00 '.
• a rear front or downstream direction upstream in the axial direction is materialized by arrows E substantially representing the direction of an electric field created by the association of an annular anode 1 placed at the rear of an annular channel 3 and d 'A cathode 2 placed substantially in front of the annular channel 3, outside of it and adjacent to it.
• the arrangement of the cathode 2 thus makes it possible to create, with the anode 1, an electric field oriented substantially in the axial direction 00 ', while being outside the propulsion jet.
• this cathode is generally, as shown in FIG. 2, doubled by a second redundant cathode.
• the annular anode 1 has an annular bottom placed concentrically with the annular channel 3. This bottom has passages, for example in the form of through holes allowing the passage of a gas which can be ionized, for example xenon.
• the propellant comprises a magnetic circuit 40 made of ferro-magnetic materials constituted by a plate 4 perpendicular to the axis 00 'of the propellant, a central arm 41 having as axis the axis 00', two circular cylindrical poles 63 and 64 having as axis l 'axis 00' and external peripheral arms 42, arranged in a symmetry of revolution around the axis 00 ', outside the annular channel 3.
• the peripheral arms 42 may be 2, 3, 4 or more, or even be constituted by a single annular arm.
• the central arm 41 is finished at its upstream end by a central magnetic pole 49, and each of the outer peripheral arms 42, is terminated at its upstream end by a magnetic pole 48
• the magnetic poles 48 are constituted by plates substantially perpendicular to the axial direction 00 '. They can, as described in column 5 lines 51-62 of US Pat. No. 6,281,622 already cited, be inclined for example between - 15 and +15 degrees relative to a plane perpendicular to the axis OO '.
• a central coil 51 centered on the central arm 41, and peripheral coils 52 wound around the outer magnetic arms 42 make it possible to create magnetic field lines joining the central pole 49 to the peripheral poles 48 and the pole 63 to the pole 64.
• the field magnetic in the annular channel is thus substantially perpendicular to the axis 00 '.
• This direction of the magnetic field in the annular channel 3 is materialized, Figure 1, by arrows M.
• the magnetic field lines are not all parallel to each other.
• the annular channel 3 is materially delimited by internal and external annular walls 61, 62 respectively, both centered on the axis 00 '. These walls are made of a refractory material as resistant as possible to ablation.
• Electrons emitted by cathode 2 go to anode 1 from upstream to downstream of annular channel 3. Part of these electrons are trapped in the annular channel 3 by the inter-polar magnetic field. The shocks between electrons and gaseous molecules contribute to ionizing the gas introduced into the channel 3 through the anode 1. The mixture of ions and electrons then constitutes a self-sustaining ionized plasma. The ions are ejected downstream under the effect of the electric field, thus creating an engine thrust directed upstream. The jet is electrically neutralized by electrons coming from cathode 2.
• the ion ejection speed is around 5 times higher than the ejection speed that can be obtained with chemical propellants. It follows that with a much smaller ejected mass one can obtain an improved thrust efficiency.
• the supply of the coils for creating the magnetic field requires an electrical supply generally made from solar panels.
• the invention relates to a plasma thruster having for the same thrust, a reduced consumption of electric current and therefore a reduced mass of electric generators, a reduced mass and size of the magnetic circuit, increased reliability and finally a reduced production cost.
• the magnetic field creation coils have a reduced number of turns wound with special high temperature wire.
• This reduced number of coiled turns results in the following advantages. Joule losses are reduced, which results in a reduction of the heating of the propellant, the reliability of the propellant is increased because the special high temperature wire is fragile.
• the total mass of the magnetic field producing elements is reduced, due to the reduction in the number of turns and the corresponding size of the magnetic circuit.
• the production cost is reduced because the special high temperature wire is expensive, and because the coils whose role is then limited to a simple adjustment of the value of the magnetic field are simplified.
• the propellant is also lightened by the reduction in the mass of the electrical power supplies made possible by the reduction in current consumption.
• the invention relates to a Hall effect plasma propellant having a longitudinal axis substantially parallel to a direction of propulsion defining an upstream part and a downstream part, and comprising - a main annular ionization and acceleration channel made of refractory material, the annular channel being open at its upstream end,
• annular gas distributing anode receiving gas from distribution conduits and provided with passages for letting this gas enter the annular channel, said annular anode being placed inside the channel in a downstream part of this channel,
• a magnetic circuit comprising upstream polar ends to create a field magnetic radial in an upstream part of the annular channel between these pole parts, this circuit being constituted by a downstream plate, from which spring upstream parallel to the axis, a central arm, located in the center of the annular channel, two cylindrical poles circular on either side of the annular channel and of the peripheral arms situated outside and adjacent to the annular channel, plasma propellant characterized in that at least one of the arms of the magnetic circuit comprises a permanent magnet.
• part of the arms of the magnetic circuit has a permanent magnet and another part of the arms of the magnetic circuit does not have permanent magnets.
• all of the arms of the magnetic circuit include a permanent magnet.
• the magnetic circuit comprises an inductor coil this is wound around an arm having no permanent magnet.
• No field coil is housed around the arms of the magnetic circuit (40) having a permanent magnet.
• FIG. 3A shows an axial section of a first example of a magnetic circuit of a plasma thruster according to the invention, section taken along the line CD of Figure 3B.
• FIG. 3B shows a cross section of the first example of a magnetic circuit of a plasma thruster according to the invention, section taken along the line AB of Figure 3A.
• FIG. 4A shows an axial section of a second example of a magnetic circuit of a plasma thruster according to the invention, section taken along the line CD of Figure 4B.
• - Figure 4B shows a cross section of the second example of a magnetic circuit of a plasma thruster according to the invention, section taken along the line AB of Figure 4A.
• FIG. 5A shows an axial section of a third example of a magnetic circuit of a plasma thruster according to the invention, section taken along the line CD of Figure 5B.
• FIG. 5B shows a cross section of the third example of a magnetic circuit of a plasma thruster according to the invention, section taken along the line AB of Figure 5A.
• one or more arms of the circuit include permanent magnets, for example in rare earths.
• This characteristic makes it possible to reduce the number of turns of the induction coils, possibly to the point of eliminating these coils or part of these coils.
• the reduction in the size of the coils which results from this modification makes it possible to reduce the transverse dimension of the magnetic circuit since the thickness of the coils to be housed can be reduced. It also makes it possible to reduce the axial dimension which is often determined as a function of the number of turns to be housed around the central arm. It thus becomes possible to limit the axial length of the propellant to the minimum length of the ionization chamber.
• Each of the embodiments of magnetic circuit 40 described - in connection with Figures 3, 4 and 5 A and B includes as in the prior art described in connection with Figures 1 and 2, an upstream plate 4, made of soft magnetic material , placed perpendicular to an axis 00 'of the circuit 40.
• This plate is completed by a central arm 41 of cylindrical shape having for axis the axis 00', by circular cylindrical poles 63 and 64 having for axis the axis 00 ', arranged on either side of an annular channel 3 and by peripheral arms 42, 42 'arranged in a symmetry of revolution about the axis 00' outside the annular channel 3.
• peripheral arms 42 there are four peripheral arms 42. Naturally the number of arms can be different.
• each of the arms 41, 42 is terminated in its upstream part by a magnetic pole referenced 49 for the pole of the central arm 41 and 48 for each of the poles of the peripheral arms 42.
• Each pole 49, 48 ending an arm 41, 42 respectively, is arranged perpendicular to the axis of said arm.
• the poles of the tilt angle may be different as described in connection with the description of the prior art.
• the increase in the number of separate peripheral arms provides an improvement in the circular symmetry of the magnetic field, between the central pole 49 and the peripheral poles 48.
• At least one of the arms comprises a permanent magnet constituting a part of the axial length of the arm.
• the arms comprising a permanent magnet bear the reference 41 'when it is the central arm and 42' when it is a peripheral arm.
• the permanent magnet is referenced 54 when it is incorporated into a peripheral arm 42 'and 55 when it is incorporated into the central arm 41'.
• all the peripheral arms 42 ′ are thus constituted from downstream to upstream of a downstream part 43 made of soft magnetic material in contact with the downstream plate 4, of a magnet in rare earth 54, of an upstream part 45 made of soft magnetic material, this upstream part 45 bearing the magnetic pole 48. It can be seen that a central part of the arm adjacent to the downstream part 43 and to the upstream part 45 is formed by said permanent magnet 54.
• the central arm 41 is made entirely of soft magnetic material.
• the peripheral arms 42 ′ each comprise a permanent magnet 54, and the central arm 41 is made only of magnetic material, an induction coil 51 being housed around said central arm 41.
• the peripheral arms 42 are made entirely of soft magnetic material.
• An induction coil 52 is arranged around each of the arms 42.
• the central arm 41 ′ has a downstream part 44 made of soft magnetic material, a permanent rare earth magnet 55, and an upstream part 46 made of soft magnetic material, this upstream part 46 carrying the magnetic pole 49.
• the central arm 41 ' has a permanent magnet 55
• the peripheral arms 42 are made only of material magnetic and an induction coil 52 is housed around each of said peripheral arms 42.
• Each of the arms 41 ′ or 42 ′ comprising a permanent magnet 55, 54 respectively, comprises a peripheral jacket 47, external to the said arm, made of non-magnetic metal.
• This jacket 47 makes it possible to hold mechanically assembled, for example by clamping, the downstream parts 43, 44, upstream 45, 46 as well as the magnet 54, 55 together constituting an arm 42 '41' respectively.
• the magnet 54, 55 is kept in contact with the downstream parts 43, 44 and upstream 45, 46 respectively.
• peripheral arms 42 ′ which comprise, as in the embodiment described in connection with FIGS. 3 A and B, permanent magnets 54.
• the central arm 41 ′ comprises a downstream part 44 made of soft magnetic material, a permanent rare earth magnet 55, and an upstream part 46 made of soft magnetic material, this upstream part 46 carrying the magnetic pole 49.
• a jacket 47 ensures the mechanical cohesion of the parts constituting together a arm 42 'or 41' and ensures that the parts of magnetic core 43, 45 and the permanent magnet 54 are kept coaxial.
• the central arm 41 ' has a permanent magnet 55
• all the peripheral arms 42' have a permanent magnet 54.
• the power of the magnets is adjusted so that the magnetic field has its optimum value in the envisaged range of operating temperature of the propellant.
• the power of the magnets is further adjusted so that the number of turns is minimal.

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• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Chemical & Material Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Plasma Technology (AREA)
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• 2002
  • 2002-07-09 FR FR0208612A patent/FR2842261A1/fr active Pending
• 2003
  • 2003-07-07 AT AT03763933T patent/ATE394596T1/de not_active IP Right Cessation
  • 2003-07-07 ES ES03763933T patent/ES2306893T3/es not_active Expired - Lifetime
  • 2003-07-07 WO PCT/FR2003/002100 patent/WO2004007957A2/fr active IP Right Grant
  • 2003-07-07 DE DE60320795T patent/DE60320795D1/de not_active Expired - Lifetime
  • 2003-07-07 RU RU2005103228/06A patent/RU2319040C2/ru not_active IP Right Cessation
  • 2003-07-07 EP EP03763933A patent/EP1520104B1/de not_active Expired - Lifetime
  • 2003-07-07 US US10/519,679 patent/US7543441B2/en not_active Expired - Fee Related
  • 2003-07-07 AU AU2003263268A patent/AU2003263268A1/en not_active Abandoned

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