9. 2 TRANSPORTATION OPERATIONS 9. 2.1 ASSUMPTIONS AND ANALYSIS The following assumptions were made as guidelines in the transportation analysis and LEO versus GEO assembly trades: • One 10 GW SPS goes on line per year for 30 years. • An SPS assembled in LEO is 24 percent heavier than one assembled in GEO because of the orbit transfer engines and propellant. • A photovoltaic SPS assembled in LEO has 11 percent more solar cells than one assembled in GEO because of solar cell degradation during the LEO to GEO transfer. • A photovoltaic SPS assembled in GEO requires less attitude control propellant per year due to its smaller size. • An SPS assembled in GEO requires 88 persons for 330 days and then goes on line. Work on the next SPS begins 35 days later, after the assembly facility and equipment are refurbished. • An SPS assembled in LEO requires 120 persons for 330 days and then 60 days for self-propelled orbit transfer. During the ascent phase, the assembly facility and equipment are refurbished for 35 days and then work begins on the next SPS. • The SPS is assembled with the aid of a local space transportation system. This system was not included in the transportation analysis but is described in subsection 12. 2. 6. • In the LEO assembled SPS scenario, the POTV delivers an initial crew to the SPS to prepare for operation after the SPS has passed through the radiation zone. A COTV later returns all construction equipment from GEO to LEO. • The GEO operations crew size is 12 persons per SPS. • Each person stays in orbit for 1 year, and one-half of each crew is rotated every 6 months. • Each SPS in GEO has a space station and logistics depot connected to it.
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