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16.522, Space Propulsion Lecture 6 Prof. Manuel Martinez-Sanchez Page 1 of 6 16.522, Space Propulsion Prof. Manuel Martinez-Sanchez Lecture 6: Hydrazine Decomposition: Performance Estimates (3) Electrothermal Augmentation Concept Geostationary satellites are most of the time exposed to the sun, but they still are subject to eclipse periods around the two vernal points (March 21, September 21); when the intersection of the orbital plane (Equator) and the ecliptic plane points to the sun. The maximum eclipse length is -1 E ecl. GEO R 24 t = 2 sin =1.16 hr 2 R π (once per day in the “eclipse season”) If the satellite is to remain active during these occultations, enough battery capacity must be incorporated. But obviously, these batteries have ample time to recharge even in eclipse season, and are idle most of the time. Starting from the payload requirements, the solar array capacity at End of Life (EOL) is typically dimensioned with a 15% margin to allow for battery charging losses. A further 15% is then added (depending on mission duration and altitude) to allow for array degradation from Beginning of Life (BOL) to EOL. An example is the military satellite DSCS III: Array output (BOL/EOL) 977 watt/837 watt ( 28V ±1% ) Batteries 750 watt 1968 watt-hr (100% DoD) [depth of discharge] 1180 watt-hr (60% DoD) Payload requirements 723 watt Thus, there is the possibility of using occasionally both the batteries and the arrays to provide power for overheating the gas generated by a 2 4 N H decomposition
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16.522, Space Propulsion Lecture 6 Prof. Manuel Martinez-Sanchez Page 2 of 6 chamber and increase the performance. In the case of the DSCS III, the power
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