1. EXECUTIVE SUMMARY High cost has been a major obstacle to development of a Solar Power Satellite (SPS) system. A major part of this cost is the expense of transporting material from Earth to geosynchronous orbit (GEO). The energy required to transport lunar material to GEO is less than 8% of that for Earth material. In addition, launch from the Moon should be more efficient than launch from Earth due to low lunar gravity and the effective lack of a lunar atmosphere. Thus, the cost of delivering materials from the Moon to GEO might be about one-fiftieth of the cost to deliver equivalent materials from Earth.(4) This suggests that the use of lunar materials could significantly reduce the cost of building an SPS system. General Dynamics Convair has studied the use of lunar resources for SPS construction.(1) The rules of that study allowed only minor changes to an earlier Boeing design(2) which had assumed that all materials came from Earth. Thus, the resulting design was not optimized for the use of lunar materials. Even so, it required only 10Z as much Earth mass as the Boeing design.(1) This document is the final report of Space Research Associates’ SPS design study emphasizing minimal use of Earth-supplied mass to achieve low cost. The ground rules of the study are listed in Table 1-1. The study objective was to provide a basis for comparison of alternative SPS concepts and subsystems in the context of lunar material utilization. TABLE 1-1 STUDY GROUND RULES o Any reasonably abundant chemical element present in lunar material could be mined, refined, and transported to the SPS construction site. All other materials must be transported from Earth. o The primary design requirement is minimal non-lunar mass. Low total mass is only a minor concern. o Scope of the study does not include design of transportation systems, materials processing, or assembly systems. o To enhance commercial feasibility, undemonstrated technology is to be avoided in the design wherever possible. o Only microwave transmission of power is to be considered. The peak intensity at the ground is not to exceed 300 W/m*2. Elements abundant on the Moon are aluminum, calcium, iron, magnesium, oxygen, silicon, and titanium. Less abundant (< 1Z) but potentially available are chromium, potassium, manganese, and sodium; though using them
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