VI-D CARGO ORBIT TRANSFER VEHICLE (John C. Hooper, Primary Propulsion Branch, EP2) 1.0 LOW THRUST CARGO OTV 1.1 GROUND RULES AND ASSUMPTIONS The low-thrust cargo OTV (COTV) is used to transport either the entire SPS as a unit or major subassemblies of the SPS from the construction site in low earth orbit (LEO) to geosynchronous orbit (GSO). In either case, the satellite is assumed to be capable of providing power to the COTV during the transfer. Any satellite penalties resulting from this mode of operation were not assessed (a summary of these ground rules is included as figure VI-D-1-1). A payload mass of 42 million pounds was selected as representative of half of a 5 GW (ground power) station; it was assumed that the payload would be capable of supplying a maximum of 4 GW to the COTV during transit. Structural considerations were assumed to limit the maximum vehicle acceleration to 10"3 g; the minimum acceleration was assumed to be limited by economic considerations relating to trip time and an arbitrary value of 5 x 10-3 g (corresponding to 180 day transit time) was selected. The attitude control system of the satellite is assumed to be capable of performing satellite orientation that cannot be accomplished by gimballing of the COTV main engines.
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