Assembly work and operation Considering that the complete assembly of SPS 2000 is much larger than the present launch systems, and the mass would be more than the payload of even the Energia launch vehicle, the SPS has to be divided into several flight units and disassembled to be packed in a payload envelope of a launch system. In the preliminary study, Ariane 5 launch vehicle has been assumed for the transportation, mainly because of its ease of access to an equatorial orbit. A launch capability of the vehicle into 1000 km high altitude orbit has been predicted to be approximately 12 tons, based on available standard data [6], According to the same data, the payload envelope is of cylindrical shape of 4.57 m diameter and 12 m length with a conical space on the top. An example of mass breakdown of a payload is shown in Table 1, which is a design target with a margin of 2 tons for one flight unit of SPS 2000. Each unit will consist of a modular portion of every subsystem of the completely assembled system, and can be operated as a small SPS even if the width of microwave beams are not sharp enough due to smaller antenna size. An integrated payload configuration is shown by Figure 3. Each unit is assembled in orbit and test operated and added to the unit(s) preceding in operation if it is a follow-on flight unit. Figure 4 shows a model of the flight unit assembled in orbit with the nose fairing on the same scale. There is a berthing space in the center of the first unit, where later flight units are unloaded. The construction work for additional modules will be made on both ends of the prism to maintain the position of the center of gravity.
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