Environmental issues cannot be isolated from technical problems in this system. The problem is how to identify a real problem among interacting parts of the system with the environment, since any part of the system can be a potential environmental issue. The legal issue peculiar to the location of the SPS is international property of outer space and solar energy rights. This problem may have no solution with which everyone can agree, but will be gradually solved through practice by implementing a small scale project. Such a small project is necessary in order to define this problem. The economic aspect of SPS is difficult and complicated, because technical efforts to improve economical performance of the SPS system are not developed enough for identifiying major project elements including space transportation system (STS). Dr. Glaser pointed out the uniqueness of the DOE/NASA SPS conceptual study because these issues were studied prior to its existence (2). 3. NECESSITY OF MULTIDISCIPLINARY ACTIVITIES IN EARLY R&D PHASE The scientific principle of the SPS to convert solar energy to electrical power and transmit it to Earth is exhibited by many satellites. In this sense, SPS avoids the difficulties of nuclear fusion. This does not mean individual technologies are ready to give information required for SPS systems engineering. For such a large system, systems engineers in charge of integration of the systems and a system planner developing the total program will have many questions about interacting elements of the system. Most of such questions can be answered by specialists, since what the systems engineers and planners want to know is specific information. Actually the specialist can provide general knowledge on his speciality obtained from other experience, not knowing circumstances of the addressed question. Questions will be returned to the first questions. For example, if a specialist of structure design is questioned about the large structure to deploy solar cells, which is an important system element to determine the concept of other elements, he will request the following information. What are the constraints and requirements? What is the maximum acceptable mass? What are the conditions to determine the rigidity of the structure? What is the allowable deformation? How long is the life and how is the structure to be disposed of? Even if the area of concern is limited to just SPS, several typical problem areas can be listed besides this example. Technical problems are such as the life of a material to be used for structure elements of SPS, evaluation of disturbance of SPS motion to determine the attitude control system, electrical problem interaction between the SPS electrical system and environmental plasmas. Concerned environmental problems are rocket exhaust products, ionosphere heating and the local environment of a power receiving site. Research is required on both the microscopic mechanism of molecular and plasma behavior and the macroscopic dynamics of Earth’s atmosphere to decide the method to measure the change of climate allegedly to be caused by the long-term effect of radiation from the SPS. 4. PRACTICAL APPROACH TO COOPERATION OF MULTIDISCIPLINARY RESEARCH ACTIVITIES Many discussions on concepts of SPS can be made by specialists of many disciplines, and it is found that experimental research is essential to answer questions
RkJQdWJsaXNoZXIy MTU5NjU0Mg==