to a water landing in a prepared landing basin. The landing site is a 5 km lake adjacent to the launch site. A dredged basin is used in preference to open sea to reduce the effect of sea state. In one concept the 900 000 kg empty SSTO is towed out of the landing basin through a canal to the launch area. At the pad area it is positioned over the launcher and anchored. A lock gate is closed, and the water is pumped out. The SSTO is then ready for on-pad servicing and launch. In a second concept, the launch pads are located around the periphery of the basin. Cost estimates were made for development, production, facilities, and operations of both the two-stage and SSTO vehicles. For a launch rate of 500 per year, the development and facilities costs total approximately $11 billion for each concept. Production costs to support a 15 year program are greater for the SSTO. Figure 12-7 gives cost per flight for each of the configurations over a range of activity levels. For activity requiring 500 launches per year, operations cost is broken into three elements. The shaded areas, which represent expendable hardware, are a significant portion of the operations costs. The shroud costs can vary over the range given by the angled line as payload density varies over a possible range required to support SPS. The significant cost effect of expending even relatively inexpensive hardware suggests continuing work to find ways to recover shrouds and the kick stage, or develop other uses in space for them. Figure 12-7. HLLV cost per flight comparison.
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