FC P F ac MM 2nc 2nc 0.5 watt/Kg-2 Kg/watt= 2000 Kg/KW 50waKg→2×102→20 100 (m/sec2)10 So, with reasonable mass/power tios for electric power one gets very low accelerations 01 0.001 ELECTRICAL If one pushes Isp in an electric thruster, Mp is reduced for given av, but Ms increases due to the high P, unless a is very low(which may be impossible because of mission duration constraints). Thus, an optimum Isp is found to exist(w 2000 sec, depending on conditions) Reference ez-Sanchez, M. and J E. Pollard. Spacecraft Overview. "Journal of Propulsion and Power 14, no. 5(September-October 1998): 688-699 [A publication of the American Institute of Aeronautics and Astronautics, Inc.] Pro f a spa martine ssn Lecture 1b16.522, Space Propulsion Lecture 1b Prof. Manuel Martinez-Sanchez Page 6 of 6 c c 1 1 Fc P mc 2 2 = = η η i c c P F c ac M M2 2 = = η η 0.5 watt/Kg 2 Kg/watt = 2000 Kg/KW → -2 50 watt/Kg 2 10 20 →× → So, with reasonable mass/power ratios for electric power one gets very low accelerations If one pushes Isp in an electric thruster, MP is reduced for given ∆V, but Ms increases due to the high P, unless a is very low (which may be impossible because of mission duration constraints). Thus, an optimum Isp is found to exist (~2000 sec, depending on conditions). Reference Martinez-Sanchez, M., and J. E. Pollard. “Spacecraft Electric Propulsion – An Overview.” Journal of Propulsion and Power 14, no. 5 (September–October 1998): 688-699. [A publication of the American Institute of Aeronautics and Astronautics, Inc.]