Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the...
Reexamination Certificate
2000-07-14
2002-05-28
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
C315S111810, C313S231310
Reexamination Certificate
active
06396211
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rocket propulsion device referred to as electric propulsion for use in the orbital attitude control of an artificial satellite or as the main propulsion of a planetary exploration mission, and more particularly to an electrostatic accelerator propulsion device of a type that can obtain propulsion as the reaction of accelerating ions in an electrostatic field.
2. Description of the Related Art
FIG. 1
shows an example of the above-described electrostatic accelerator propulsion device of the prior art. The electrostatic accelerator propulsion device comprises gas tank
101
, main discharge chamber
107
, acceleration electrodes
108
, and neutralizer
110
. Propellant supplied from gas tank passes through gas feeder
103
and isolators
104
by way of feedlines
102
, and is supplied to main discharge chamber
107
and neutralizer
110
. In main discharge chamber
107
, propellant in a gaseous state undergoes electrolytic dissociation by direct-current discharge, high-frequency discharge, or microwave discharge, thereby generating plasma
106
. In the case of microwave discharge, for example, plasma is generated by supplying microwaves that are generated at microwave power supply
114
to main discharge chamber
107
via impedance matching circuit
105
, which is constituted by a waveguide or antenna, and then carrying out discharge. Isolators
104
are provided to prevent dielectric breakdown both between main discharge chamber
107
and gas feeder
103
and between neutralizer
110
and gas feeder
103
. Neutralizer
110
emits electrons
112
from an orifice to electrically neutralize positive ions
113
that are emitted from acceleration electrode
108
.
Direct-current voltage is applied to acceleration electrode
108
by acceleration power supply
109
, positive ions
113
within the plasma are accelerated to a high speed by the electrostatic field that is generated between the electrodes, and propulsion is generated as a reaction to this acceleration.
Plasma
111
in neutralizer
110
is generated by direct-current discharge, high-frequency discharge, or microwave discharge, and electron current
112
is emitted from the orifice provided downstream to electrically neutralize the ion beam.
The electrostatic accelerator propulsion device of the type is described on page 937 of “Aeronautics & Space”, Second Edition (Sep. 30, 1992, Maruzen Publishing).
Typically, electrostatic accelerator propulsion devices of the prior art have been complicated systems requiring a plurality of power supplies, such as a power supply for plasma generation and a power supply for positive ion acceleration, and fabrication costs were excessive. In addition, the electrodes had to be installed with extremely small gaps, and the accuracy of this installation had a large effect on the performance of the propulsion device.
Regarding large-scale electric propulsion devices of the prior art having a diameter of 20 centimeters or more, the direct-current discharge type exhibits the best propulsion performance of current electric propulsion devices, but if size and power are reduced, the proportion of ion loss is relatively great and the addition of plasma
106
and maintaining discharge are therefore problematic. The presence of an antenna as impedance matching circuit
105
inside main discharge chamber
107
has the advantage of enabling generation of a high-density plasma, but suppressing wear and tear on the antenna due to ion sputtering has been problematic. Furthermore, the drop in performance due to the propellant that is supplied to neutralizer
110
, which makes no direct contribution to propulsion, cannot be ignored. Use of electromagnetic valves of the prior art in the valves in gas feeder
102
and isolator
104
results in power consumption that, when compared with the electric power for generating propulsion, cannot be ignored.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device having a simplified system configuration, higher reliability, lower fabrication cost, and furthermore, that eases the need for accuracy when installing electrodes.
It is another object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device that reduces damage to an antenna due to wear and tear on electrodes.
It is another object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device in which a neutral plasma need not be generated and in which excessive propellant need not be supplied.
It is another object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device in which the power supply is made more compact.
It is another object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device in which acceleration electrodes have a simple construction.
It is another object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device in which stable plasma generation is possible even at low power.
It is another object of the present invention to provide a microwave discharge-type electrostatic accelerator propulsion device in which the propellant supply system is more compact.
In the microwave discharge-type electrostatic accelerator propulsion device according to the present invention, the inner walls of the discharge chamber are made of an insulating material, and the acceleration electrode that accelerates positive ions within the plasma consists of an upstream acceleration electrode and a downstream acceleration electrode that form an electrostatic field between the electrodes, provided upstream and downstream of the discharge chamber, respectively.
Since electric potential is applied between the two electrodes that are provided upstream and downstream of the discharge chamber using a single power supply, fewer power supplies are required for ion acceleration than in electrostatic accelerator propulsion devices of the prior art. Moreover, since the accuracy demanded in installing the electrodes is greatly eased, not only is the system configuration simplified and reliability increased, but fabrication costs are also reduced. In addition, since the electrodes are provided upstream and downstream of the discharge chamber, the inner walls of the discharge chamber must be an insulating material.
According to an embodiment of the present invention, the antenna for emitting microwaves inside the discharge chamber is a plate antenna that is formed by a pattern on a printed substrate. Since the antenna is a plate antenna formed by a pattern on a printed substrate and not a cylindrical dipole antenna, damage to the antenna caused by wear of the electrodes is greatly reduced and the durability of the propulsion device can be greatly improved.
According to an embodiment of the present invention, a cold cathode is used as a neutralizer. Accordingly, there is no need to generate a neutral plasma or to supply extra propellant, and the drop in performance attendant to a smaller rocket propulsion device can be remedied.
According to an embodiment of the present invention, the antenna is of a circuit construction in which it is arranged on the same substrate as a microwave matching circuit, a microwave amplification circuit, and a microwave oscillator constituted by microstrip lines. In other words, since a portion of the power supply is attached to the engine side (because it is mounted on the engine substrate), miniaturization of the power supply is facilitated, the entire rocket propulsion device can be produced as a unit, and it becomes possible to apply the invention to a clustered configuration with a plurality of microwave discharge-type electrostatic accelerator propulsion devices.
According to an embodiment of the present invention, the antenna is also used as the upstream electrode for ion acceleratio
Advanced Technology Institute, Ltd.
Knobbe Martens Olson & Bear LLP
Tran Thuy Vinh
Wong Don
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