ELECTRIC PROPULSION (EP) THRUSTERS HAVE THE POTENTIAL TO ENHANCE OR ENABLE DISCOVERY-CLASS MISSIONS. HOWEVE…

Public award description

ELECTRIC PROPULSION (EP) THRUSTERS HAVE THE POTENTIAL TO ENHANCE OR ENABLE DISCOVERY-CLASS MISSIONS. HOWEVER, A SIGNIFICANT CHALLENGE IN SCALING MICRO (<100 W) EP DEVICES UP AS WELL AS SCALING MACRO (>1 KW) EP DEVICES DOWN IS THE LACK OF A COMPATIBLE NEUTRALIZER TECHNOLOGY IN THE MESO SCALE (<1 KW). TRADITIONALLY, THE TECHNOLOGY USED FOR SPACECRAFT NEUTRALIZATION HAS BEEN THE HOLLOW CATHODE, THOUGH HOLLOW CATHODES REQUIRE AN UNSATISFACTORY FRACTION OF A PROPULSION SYSTEM'S PROPELLANT AND POWER IN THE MESO-SCALE REGIME. IN FACT, THEY REQUIRE SUCH A LARGE AMOUNT OF PROPELLANT AND POWER THAT SYSTEM EFFICIENCY IS REDUCED BY 50-100%. IN ADDITION, USING A HOLLOW CATHODE CAUSES UNDESIRABLE SPECIFIC IMPULSE REDUCTION. THE MOST PROMISING TECHNOLOGY FOR MESO-SCALE NEUTRALIZERS IS FIELD EMISSION (FE), WHICH REQUIRES THE USE OF NANO-SCALE SHARP EMITTERS AND HIGH ELECTRIC FIELDS TO ESTABLISH A BEAM OF ELECTRONS. THE DRAWBACK OF FE DEVICES IS THAT THE NANO-SCALE EMITTERS BECOME DAMAGED WHEN OPERATED IN ELEVATED PRESSURE ENVIRONMENTS (10-5 TORR), CAUSING CATASTROPHIC FAILURE. THE RESEARCH PROPOSED HERE IS TO DEVELOP FIELD-EMISSION CATHODES FOR USE IN MESO-SCALE EP THAT ELIMINATE TIP DEGRADATION NOT THROUGH ATTEMPTS TO MINIMIZE TIP WEAR, BUT INSTEAD BY INCORPORATING SELF-ASSEMBLING NANOSTRUCTURES THAT CAN REPEATEDLY RE-GENERATE DAMAGED EMITTER TIPS IN SPACE AND FULLY RESTORE THE FUNCTIONALITY OF A DAMAGED OR DEGRADED CATHODE. THE PROCEDURE IS THE EQUIVALENT OF HAVING A MEMS FABRICATION AND REPAIR LAB ON-BOARD THE SPACECRAFT. THE RE-GENERABLE EMITTERS PROPOSED HERE HAVE BEEN SUCCESSFULLY DEMONSTRATED IN THE LABORATORY IN WORK BY MAKELA, ET. AL. DATING BACK TO 2007. THE RE-GENERABLE NEUTRALIZERS COULD ENABLE HIGHLY EFFICIENT, HIGH-ISP, LOW-MASS PROPULSION SYSTEMS OPERATING BETWEEN A FEW WATTS AND 1 KW BY EITHER SCALING EXISTING MICRO TECHNOLOGIES UP OR SCALING EXISTING MACRO TECHNOLOGIES DOWN.