5. Development of automated construction techniques is complex and requires a great deal of further effort. A preliminary task evaluation based on a conceptual construction technique suggests that as many as 600 personnel may be required in space to construct an SPS in 1 year, with minor variations expected in personnel required due to configuration and construction location. Placing and supporting these personnel in orbit is a relatively small factor in the overall transportation requirement. 6. Past studies have indicated an apparent performance advantage of constructing, assembling, or deploying all or a portion of the solar arrays in low-Earth orbit and then utilizing solar energy with electric thrusters to propel the system or major elements thereof to geosynchronous orbit. The conclusion of the present study is that this area needs further study with full consideration given to the following factors: a. Degradation of the exposed solar arrays during transit b. Protection of unused arrays during transit c. Earth shadowing during portions of transit possibly requiring nonsolar propulsion d. Docking and assembly of large SPS sections at geosynchronous orbit and resulting impact on structural design e. Relative simplicity of chemical stages for transfer of "containerized" packages to geosynchronous orbit f. Radiation conditions at geosynchronous orbit 7. The SPS in equatorial orbit will be eclipsed both by the Earth and by other satellites. These eclipses result in as many as three brief (up to 75 min) power outages per day for two 6-week periods per year, although less than 1 percent of the available energy is lost. The SPS/grid system must be designed to accommodate these outages. 8. Conceptual designs and characteristics were developed for two- stage winged and ballistic heavy lift launch vehicles of varying payload capability. Although the ballistic systems are much smaller and lighter, recovery and reusability will be key issues in establishing the desired configuration. 9. Heavy lift launch vehicle design considerations established hydrocarbon fuel rather than hydrogen as the choice for first-stage propellant because of its greater energy density. 10. Considerations of I and confidence in technical development of candidate electric engines indicate that the MPD arcjet engine appears to be the best choice for self-powered orbital tranfer. These engines are also suitable for subsequent use as thrusters for the SPS attitude control system. 11. The high launch rates required indicate that launch window and related operational considerations may become significant factors. Launch latitudes near the Equator greatly expand the launch window and offer performance advantages.
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