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An electric propulsion device is disclosed having an anode and a cathode. The propulsion device includes a discharge annulus having the anode adjacent an end region thereof. At least one inlet aperture is adjacent the anode, the aperture(s) having propellant gas flow therethrough into the discharge

An electric propulsion device is disclosed having an anode and a cathode. The propulsion device includes a discharge annulus having the anode adjacent an end region thereof. At least one inlet aperture is adjacent the anode, the aperture(s) having propellant gas flow therethrough into the discharge annulus. The propellant gas has an ionization potential. Opposed, dielectric walls define the annulus, with at least one of the opposed dielectric walls having pores therein, the pores having cooling gas flow therethrough into the discharge annulus and substantially adjacent the opposed dielectric wall(s). The cooling gas has an ionization potential higher than the ionization energy of the propellant gas. The cooling gas is adapted to substantially prevent at least one of secondary electron emission and sputtering of the dielectric walls.

대표청구항 ▼

What is claimed is: 1. An electric propulsion device comprising: an anode and a cathode; a discharge annulus having the anode adjacent an end region thereof; at least one inlet aperture adjacent the anode, the at least one inlet aperture having propellant gas flow therethrough into the discharge an

What is claimed is: 1. An electric propulsion device comprising: an anode and a cathode; a discharge annulus having the anode adjacent an end region thereof; at least one inlet aperture adjacent the anode, the at least one inlet aperture having propellant gas flow therethrough into the discharge annulus, the propellant gas having a first ionization potential; and an inner dielectric wall and an outer dielectric wall, wherein the inner and outer walls are concentric, wherein the discharge annulus is between the inner and outer walls, at least one of the first and second dielectric walls having pores therein, the pores having cooling gas flow therethrough into the discharge annulus and substantially adjacent the at least one of the first and second dielectric walls, the cooling gas having a first ionization potential higher than the first ionization potential of the propellant gas, the cooling gas adapted to substantially prevent at least one of secondary electron emission and sputtering of the dielectric walls. 2. The electric propulsion device according to claim 1, wherein the device is an arcjet thruster. 3. The electric propulsion device according to claim 1, further comprising an electromagnet operatively disposed in the device such that a magnetic field generated thereby is substantially normal to a center axis of the discharge annulus, the magnetic field having its peak magnitude substantially adjacent an exit plane of the discharge annulus. 4. The electric propulsion device according to claim 3, wherein the device is a Hall Effect Thruster (HET). 5. The electric propulsion device according to claim 1, wherein the propellant gas has a molecular weight, and wherein the cooling gas has a molecular weight substantially similar to the molecular weight of the propellant gas. 6. The electric propulsion device according to claim 5, wherein each of the molecular weights of the propellant gas and the cooling gas ranges from about 2 kg/kmole to about 210 kg/kmole. 7. The electric propulsion device according to claim 1, wherein each of the propellant gas and the cooling gas have a first ionization potential and a second ionization potential, and wherein the first ionization potential of the cooling gas is higher than the second ionization potential of the propellant gas. 8. The electric propulsion device according to claim 1, wherein each of the propellant gas and the cooling gas has a viscosity, and wherein the viscosity of the cooling gas is greater than or equal to the viscosity of the propellant gas. 9. The electric propulsion device according to claim 8, wherein the viscosity of the cooling gas ranges from about 10-6 N-s/m2 to about 10-4 N-s/m2. 10. The electric propulsion device according to claim 1, wherein the anode mass flow rate ranges from about 1 mg/s to about 1 g/s. 11. The electric propulsion device according to claim 1, wherein the pores are defined in each of the first and second dielectric walls. 12. The electric propulsion device according to claim 1, wherein the pores comprise throughbores defined in the at least one of the first and second dielectric walls, the throughbores being angled substantially toward an exit plane of the discharge annulus in a manner sufficient to direct the cooling gas substantially toward the exit plane. 13. The electric propulsion device according to claim 12, wherein some of the throughbores are disposed in an acceleration region of the discharge annulus near the anode, and some others of the throughbores are disposed from the acceleration region toward the exit plane of the discharge annulus. 14. The electric propulsion device according to claim 1, wherein the cooling gas substantially thermally insulates the at least one of the first and second, dielectric walls. 15. The electric propulsion device according to claim 1, wherein the device has a power requirement ranging from about 1 kW to about 200 kW. 16. The electric propulsion device according to claim 1, wherein the device has a specific impulse ranging from about 2000 seconds to about 10000 seconds. 17. The electric propulsion device according to claim 1, wherein the at least one aperture extends through the anode. 18. The electric propulsion device according to claim 1, wherein there is a plurality of apertures extending through the anode. 19. The electric propulsion device according to claim 1, wherein the propellant gas has a temperature and becomes an ionized propellant gas in the discharge annulus; and wherein the cooling gas is a neutral cooling gas having a temperature lower than the propellant gas temperature at the at least one inlet aperture. 20. The electric propulsion device according to claim 19, wherein the neutral cooling gas substantially isolates the ionized propellant gas from the first and second dielectric walls. 21. The electric propulsion device according to claim 1, wherein the cooling gas has a substantially constant flow rate. 22. The electric propulsion device according to claim 1, further comprising means, in communication with the pores in the at least one of the first and second dielectric walls, for metering cooling gas flow based upon ion current at the first and second dielectric walls. 23. A Hall Effect Thruster (HET) electric propulsion device comprising: an anode and a cathode; a discharge annulus having the anode adjacent an end region thereof; at least one inlet aperture adjacent the anode, the at least one inlet aperture having propellant gas flow therethrough into the discharge annulus, the propellant gas having a first ionization potential; an inner dielectric wall and an outer dielectric wall, wherein the inner and outer walls are concentric, wherein the discharge annulus is between the inner and outer walls, at least one of the first and second dielectric walls having pores therein, the pores having cooling gas flow therethrough into the discharge annulus and substantially adjacent the at least one of the first and second dielectric walls, the cooling gas having a first ionization potential higher than the first ionization potential of the propellant gas, the cooling gas adapted to substantially prevent at least one of secondary electron emission and sputtering of the dielectric walls, wherein the cooling gas substantially thermally insulates the at least one of the first and second dielectric walls; and an electromagnet operatively disposed in the device such that a magnetic field generated thereby is substantially normal to a center axis of the discharge annulus, the magnetic field having its peak magnitude substantially adjacent an exit plane of the discharge annulus. 24. An electric propulsion device comprising: an anode and a cathode; a discharge annulus having the anode adjacent an end region thereof; at least one inlet aperture adjacent the anode, the at least one inlet aperture adapted to have propellant gas flow therethrough into the discharge annulus, the propellant gas having a first ionization potential; and an inner dielectric wall and an outer dielectric wall, wherein the inner and outer walls are concentric, wherein the discharge annulus is between the inner and outer walls, at least one of the first and second dielectric walls having pores therein, the pores adapted to have cooling gas flow therethrough into the discharge annulus and substantially adjacent the at least one of the first and second dielectric walls, the cooling gas having a first ionization potential higher than the first ionization potential of the propellant gas, the cooling gas adapted to substantially prevent at least one of secondary electron emission and sputtering of the at last one of the first and second dielectric walls. 25. The electric propulsion device according to claim 3, wherein the device is a magnetoplasmadynamic (MPD) thruster.