Ground Support Facilities - All launches, both the HLLV and PLV were assumed to take place from Cape Kennedy. Since the PLV is a Shuttle- derived vehicle, a large portion of the facilities and equipment built for shuttle can be used. The launch facilities required for the HLLV are more extensive. Several launch pads will be required to support an SPS implementation rate of 10 GW per year. A preliminary cost estimate of $3.4 billion for the construction of the required facilities and the fabrication of specialized ground support equipment has been made. Consideration of 28.5 Degree Versus 55 Degree Inclination - A comparison was made by the Marshall Space Flight Center which considered the potential cost impacts of launching SPS construction materials into a 55 degree inclination as opposed to the baseline inclination of 28.5 degrees for low Earth orbit (LEO) assembly. Potential benefits of the higher inclination were elimination of chemical propulsion subsystem requirements by earth shadowing. Such chemical augmentation of the already on-board SPS ion propulsion subsystem would not be necessary at 55 degrees. Eliminating the chemical system was estimated to save about 100 million dollars in development cost and about 500 million per satellite in launch costs associated with the propulsion hardware. These savings were reduced however, by the lower launch vehicle performance into 55 degrees. A number of other factors would have to be considered in more detail before a conclusive decision could be reached regarding the most desirable inclination for a low earth orbit assembly of the SPS. This has not been pursued due to the subsequent selection of geosynchronous orbit construction; however, the trade data does tend to suggest that further analysis is warranted should the LEO assembly option be reconsidered.
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