ELECTRIC THRUSTER WITH PROTECTIVE COATING ON THERMIONIC EMITTER
A system includes an electric thruster that is configured to generate thrust. The electric thruster includes an electron emitter that has a thermionic emission material with a protective surface layer.
1 . A system comprising:
an electric thruster configured to generate thrust, the electric thruster including an electron emitter comprising a thermionic emission material having a protective surface layer.
2 . The system as recited in claim 1 , wherein the protective surface layer is boron nitride.
3 . The system as recited in claim 2 , wherein the protective surface layer has a thickness of about 1 nanometer to about 100 nanometers.
4 . The system as recited in claim 2 , wherein the protective surface layer is a monolayer.
5 . The system as recited in claim 1 , further comprising a hollow cylindrical cathode tube, and the electron emitter is disposed in the hollow cylindrical cathode tube.
6 . The system as recited in claim 5 , wherein the electron emitter is cylindrical and is made of a metal hexaboride.
7 . The system as recited in claim 6 , wherein the metal of the metal hexaboride is selected from the group consisting of Rare Earth elements and combinations thereof.
8 . The system as recited in claim 6 , wherein the metal of the metal hexaboride is selected from the group consisting of Alkaline Earth elements and combinations thereof.
9 . The system as recited in claim 6 , wherein the metal of the metal hexaboride is selected from the group consisting of transition metal elements and combinations thereof.
10 . The system as recited in claim 6 , further comprising an oxygen-containing propellant gas source fluidly connected with the hollow cylindrical cathode tube.
11 . A spacecraft including the system as recited in claim 1 .