The cesium microthruster system i s described.The ion engine subsystem consists of a singlebutton porous tungsten ionizer, electrodes. neutralizer filaments, and a cesium storage and feed system. trol logic and power conditioning. logic provides the necessary electronics for sequencing the microthruster startup and shutdown cycles, standby operating powers. telemetry signal conditioning, command interface circuits, and digital-to-analog controls. The rated thrust level of the thruster i s 20 plb at a specific impulse of 6700 sec. The beam deflection, which provides two-axis deflection for thrust vectoring, i s discussed. and such characteristics as critical temperature and perveance of the thruster a r e presented.Power input to the control logic/power conditioner at the 20 g b thrust level i s approximately 34 W.
A 20-cm LM cathode thruster system has been developed for operation at beam currents IB = 0.5-1.0 amp and a beam voltage VB < 2 kv. At the maximum beam level, the total source energy per ion is Vs = 315 ev/ion at a mass utilization efficiency rj m = 89%. Discharge chamber performance is essentially unchanged for operation at a reduced beam voltage VB = 1 kv. The thruster employs a conventional thin-screen, high-transparency (70%) ion-extraction system and an LM cathode which is thermally integrated with the thruster body. A mercury feed subassembly provides electrical isolation from the propellant supply while regulating liquid mercury flow to the thruster. At full-rated power, the LM cathode operates at an equilibrium temperature TK -200°C. With an over-all mass of 6 kg (exclusive of propellant and reservoir), the system operates with an over-all efficiency of T]T = 72% at a specific impulse Jsp, eff = 4040 sec or alternatively with rjT = 60% at / sp , e ff = 2710 sec.
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