Power plants – Reaction motor – Ion motor
Patent
1999-01-21
2000-12-12
Thorpe, Timothy S
Power plants
Reaction motor
Ion motor
602031, 3133611, 31511181, H05H 100
Patent
active
061582093
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to electro-ionic plasma thrusters as applied in particular to propulsion in space, and also to industrial processes on the ground, and more particularly to plasma thrusters of the closed electron drift type, also known as stationary plasma thrusters (SPT), as Hall-effect thrusters, or as anode layer thrusters (ALT).
PRIOR ART
Thrusters of the closed electron drift type or thrusters of the stationary plasma type are already known, in particular from an article by L. H. ARTSIMOVITCH et al., published in 1974, and relating to the stationary plasma thruster (SPT) development program and testing on the "METEOR" satellite, which thrusters differ from other categories of ion thrusters by the fact that ionization and acceleration are not separated, and the acceleration zone includes equal numbers of ions and of electrons, thereby making it possible to eliminate any space charge phenomena.
A closed electron drift thruster as proposed in the above-mentioned article by L. H. ARTSIMOVITCH et al. is described below with reference to FIG. 6.
An annular channel 1 defined by a piece 2 of insulating material is placed in an electromagnet comprising an outer annular pole piece 3 and an inner annular pole piece 4 placed respectively outside and inside the piece 2 of insulating material, a magnetic yoke 12 disposed at the upstream end of the thruster, and electromagnet coils 11 which extend over the full length of the channel 1 and are connected in series around magnetic cores 10 connecting the outer pole piece 3 to the yoke 12. A hollow cathode 7, connected to ground, is coupled to a xenon feed device 17 to form a cloud of plasma in front of the downstream outlet from the channel 1. An annular anode 5 connected to the positive terminal of an electrical power supply, e.g. at 300 volts, is disposed in the closed upstream portion of the annular channel 1. A xenon injection tube 6 co-operating with a thermal and electrical insulator 8, opens out into an annular distribution channel 9 disposed in the immediate vicinity of the annular anode 5.
The ionization and neutralization electrons come from the hollow cathode 7. The ionization electrons are attracted into the insulating annular channel 1 by the electric field that obtains between the anode 5 and the plasma cloud coming from the cathode 7.
Under the effect of the electric field E and of the magnetic field B created by the coils 11, the ionization electrons follow an azimuth drift trajectory suitable for maintaining the electric field in the channel.
The ionization electrons then drift along closed trajectories inside the insulating channel, which is why the thruster is called a "closed electron drift" thruster.
The drift motion of the electrons considerably increases the probability of electrons colliding with neutral atoms, which phenomenon produces ions (in this case of xenon).
The magnetic field is defined by the shapes of the pieces 3 and 4. The magnetic field lines 13 are essentially radial in the outlet plane 14 of the thruster.
Closed electron drift thrusters thus make use of ion acceleration within a plasma. The ions do not all have the same energy. To a first approximation, the ion beam has two components: upstream from the acceleration channel 1; and the acceleration channel 1 and expands in the volume situated immediately downstream from the outlet plane 14 of the thruster.
FIGS. 8a and 8b show how ion current is distributed as a function of energy for an ion thruster operating at a discharge voltage Vca of 300 V.
FIG. 8a has six curves corresponding to respective angles of 0.degree., 7.degree.30', 15.degree., 22.degree.30', 30.degree., and 37.degree.30' relative to the axis of the thruster. It can be seen that the ion current has a peak corresponding to 270 eV, and of an amplitude that drops off quickly when the angle relative to the axis of the thruster increases. This main peak is due to the primary ions. Secondary ions produced in the outlet plane of the thruster form a secondary peak corresponding to ene
REFERENCES:
patent: 3363124 (1968-01-01), Bensussan et al.
patent: 4466242 (1984-08-01), Sovey et al.
patent: 5150010 (1992-09-01), Kageyama
patent: 5646479 (1997-07-01), Aston
patent: 5889371 (1999-03-01), Boyarsky et al.
Iakubov Akhmet Mialikovich
Jacoupov Aidar Beksultanovich
Khartov Sergey Anatolievich
Latischev Leonid Aleckseevich
Valentian Dominique
Societe Nationale d'Etude et de Construction de Moteurs
Thorpe Timothy S
Torrente David J.
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