constraints such as solar wind, space debris, and the Earth's radiation belts and magnetic field, but also user demands, be they on Earth or in space. Therefore, technical countermeasures to these physical constraints will have to be installed on each satellite. Another question involves the SSP receiving stations. Once the best type of receiver is demonstrated in Phase B (e.g. microwave rectenna or laser receiver), the problems for Phase C include: Where should ground receivers be located? What will the architecture of the ground or receiving system be? And what is the optimum size of the receiver? This last question is especially important to the SSP satellite, because if a microwave system is used then the size of the rectennae will also determine the size of the transmitter. With regard to the transmitter, it is also important to decide whether the satellite should be required to change its beaming angle, so that it will be able to transmit power to various locations on Earth and in space. Apart from the technical issues for the solar power satellite itself, there are also items that adress a complete network design as could be envisaged for large scale use of space solar power. We have mainly considered the problem of delivering solar power to the electrical power grid on earth. Relating to the overall architecture and concept of large scale solar power satellites we have identified the following points. What should the structure of SSP look like? Should it be a monolithic system (one or a few large satellites) or a more distributed system (constellations of satellites)? Should a single SSP system be capable of delivering energy to both Earth and to space-based receivers or are multiple SSP networks necessary? Also, should substantially different technologies and frequencies be used in these cases (microwave beaming for transmission to Earth and laser beaming for space-to-space)? How do we decide between the requirements of continuous power or energy storage? If continuous power is needed, does this require SSP satellites in GEO or in LEO with relay satellites? For the LEO case, what orbit should be selected. Also, if relay satellites are used, how will efficiency of energy transmission be affected? If storage is required, how will SSP be more competitive than terrestrial solar energy?The issue of compatibility with existing network systems should be adressed (frequency, voltage, stability). Related to this, how do we select and enforce an industrial standard for SSP satellites and rectennae? Will these standards reduce production costs? Finally, who and where are the end users for SSP (earth, satellites, moon)? This could impact the network concept. For instance, should a SSP satellite be positioned around the moon, both for demonstration and to provide energy for a lunar base that can then provide resources for the largescale SSP system? Resources & Manufacturing is another group of aspects which has been addressed.How does the use of Earth resources compare to mostly using Lunar resources? Using extra-terrestrial materials will require new materials transformation processes. Materials test on earth is limited by the amount of lunar material we have. How are we going to determine the efficiency of those machines and processes? What about the problems associated with lunar resources extraction? Is the use of lunar materials for construction really more cost effective ? In order to reduce the Delta-V, and consequently reducing the price of putting objects in space, it has been proposed to use extraterrestrial resources and to build a SSPP in space rather than on earth. This possibility imposes technical and technological challenges. In fact, the use of lunar materials, for example, implies the settlement of a lunar base, and requires vehicles that land on and depart from the moon. Definition of studies, crew selection, life sciences research, etc. have to be done. Are lunar mass drivers really more efficient than simple lunar launchers? Is L2 really the best Lagrangian point for resource collection? What space transportation systems and methodology would be required for use of Earth resources only and what systems would be required for use of Lunar and other non-terrestrial resources? Such large structures as SSP with current launch volume restrictions give rise to the question of what the construction and maintenance method should be, and what level of automation is most effective for this (robots versus manned systems)? Related to the station crew, will a permanent crew per station be required or can “roving” crews be used? What will be the effects of long missions on the crew (maintenance, construction, control, etc of SSPP). Can resources from near-Earth asteroids economically be used for SSP? How about Shuttle and Energia main tanks? If these tanks are going to be used by SSP, then perhaps some essential construction materials can be added to them prior to launch?
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