4.2.3 Business Market. The concept of power from space has been around for over twenty years and various potential markets have been identified, for example orbiting platforms and large-scale power for Earth. However, because solar power satellites are only at the conceptual stage, paying customers will not emerge until these satellites move from concept to reality. Therefore, the market requires seeding through a series of hardware demonstrations. (This terraced approach to the development of a space solar power program is discussed in the next section). The “markets” in the terrace of program development will most likely progress from government/international subsidizing supporters to commercial, paying customers. The evolution of the market drives the evolution of the spacecraft, infrastructure, etc. required to meet market needs. In the next section, the market will be shown to be the most critical driving factor for projects within the overall program. Finance. Financing is essential for the development of a new product, such as power from space. If financing cannot be secured at every step in the terrace of overall program development, then space solar power will continue to be a dream forever locked in the prison of paper studies. Cost competitiveness. If all of the technologies for a space solar power program were available, if government and public support were strong, and even if several steps in the terrace of program development were successfully completed, the program would still fail if the power provided was not cost competitive with other energy alternatives. However, when comparing space solar power with these alternatives, the real cost of energy, as discussed in Chapter 2, must be taken into consideration, including the cost to the environment. Also, the fact that most of the currently used energy resources are limited must be acknowledged when planning for the future. All models say that energy demand is increasing and continued use of limited energy resources implies that supply is decreasing. Therefore, a long-term view for supply and demand is required when assessing the current and future cost competitiveness of energy from space. 4.2.4 Technical The identification of technical driving requirements in a terraced space solar power program requires the consideration of non-technical driving requirements and program constraints, such as cost. At the hardware level, i.e. the lowest technical level of a program, it is essential to understand the relationship between all of the program's elements, the program's sensitivity to changes in these elements and the effects of changes on technical aspects of the program. This type of approach is required since the magnitude of projects within the space solar power program is expected to increase with time and this increase will have significant effects on hardware design. Therefore, to get to the hardware level of the program the main drivers for the design of a solar power satellite are identified. The result is shown in Figure 4.2. The key system driver shown in Figure 4.2 is the market, which has previously been categorized as near-term, mid-term and long-term. The market requirements will vary according to category and can be found by answering the questions of: • How much power is to be delivered? • Where is it to be delivered? • What is the purpose! (demonstration; large-scale orbital power supply, etc.) From the market requirements one can derive the physical requirements of the system, such as orbit and frequency selection. Note that the physical requirements are also influenced by legal and regulatory constraints as well as available technology. From the physical and market requirements (frequency, amount of delivered power, and orbit) one can derive the power collection, conversion and distribution (PCCD) requirements. These requirements will drive the selection of the power generation method (solar photovoltaic, solar dynamic, etc.) and the selection of the power conversion devices. PCCD requirements will also fix the aperture product of the system, which is a function of wavelength and distance of transmission. Selection of PCCD elements, along with orbit selection, will drive the spacecraft design requirements. And finally, spacecraft design and orbit selection will drive the requirements for space transportation and on-orbit operations. Note that the process of flowing down system requirements is constrained by cost and that it is an iterative process due to uncertainty and the changing nature of the projects within the terraced program.
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