Thrusters specific impulse

Main uses. Caesium metal is used in the production of vacuum tubes as a scavenger to reduce residual gaseous impurities after the tubes have been sealed. Cs may be generated in situ by heating a pellet of caesium chromate mixed with a metal powder (Zr, Ca, Ba). Cs metal is used as the propellant in ion thrusters (employed in satellites for orientation control) it is ionized in a vacuum chamber, the Cs+ are then accelerated through a nozzle (high specific impulse because of high atomic mass). 

Optimal Specific Impulse of Electric Propulsion Systems (Ion and Plasma Thrusters). Based on relation (11-43) between the initial mass Mq of a spacecraft at low (near-Earth) orbit and its specific impulse /sp, derive formula (11-44) for the optimal value of the specific impulse, /sp Explain why the optimal value of the specific impulse of the ion and plasma thrusters, /sp does not depend on the value of their thrust and is mostly determined by the duration of space flight. 

Polzin, K.A., Markusic, T.E., Stanojev, B.J., 2007. Liquid bismuth propellant management system for the very high specific impulse thruster with anode layer. NASA-TM-2007-214958. 

The specific impulses for several propulsion options are shown in Table 1. The specific impulse for nuclear fuels can be many times that of chemical fuels, while the thrust is correspondingly lower and the run time longer. Electrostatic thrusters have relatively low thrust but can run virtually continuously and, therefore, can provide short trip times and low launch weights for a given payload. In... 

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