polar inclination; the exact inclination angle depends on the altitude selected; Middle Earth Orbit (MEO) circular orbit, utilized for either SunTower or relay power beaming concepts, has low-to-nrid values of inclination (nominally 3 0°) and altitudes in the range 6,000-12,000 km; and. Geostationary Earth Orbit (GEO), with application to either SolarDisc or SunTower-Relay concepts (solar occultation by Earth does occur for MEO and GEO orbits with daily variability through the year, but the effect on power beaming performance is not too significant). 73. Robustness of “Fresh Look** Study Results An extensive effort, documented at length in Section 6, has been made to examine and understand the degree to which the results of the “fresh look” study might change - or will remain unaltered - as a result of changes in key assumptions, projections of the performance of critical technologies, or changes in selected policy- and government- related factors. Overall, the sensitivity analyses that have been conducted suggest that the results of the present study are remarkably robust - with the exception of a few key areas. As mentioned previously, low-cost space transportation (preferably less than $200 per pound to LEO) is absolutely enabling. Also, achieving high efficiency PV arrays (both thin film and/or concentrator-PV array) is important, but less sensitive that ETO: if arrays with a power output of 500 watts or more per kilogram of array can be achieved, then SSP should be viable, (a little better efficiency (e.g., 1000 W/kg) will greatly improve economic performance; lower efficiency (e.g., 100 W/kg) makes SSP non-viable). SSP concepts examined in the present study are reasonably insensitive to changes in logistics-related parameters. For example, above a certain minimum - a “threshold” of about 10-20 years - variations in the lifetime of individual SPS systems, have moderate to little impact on overall economic performance. This appears to be due to the very low infrastructure required for these concepts. Even for these concepts, however, if subsystem lifetimes fell much below 10 years, then economic performance drops drastically. A great opportunity for significantly increasing the economic viability of the SSP systems exammed in the current study lies in the potential for fixture policy decisions to enable the application of “externality” surcharges to space solar power electricity prices. For example, if an “externality” surcharge equivalent to about 100 per kilowatt hour were applied to the price of electricity from a MEO SunTower system (Case 16), the overall discounted net present value (NPV) of the system increases by more than a fector of 2:1 (from about $15 B to more than $35 B). 7.4. Achieving Public Acceptance Study participants believe that no SSP-derived energy services will find markets unless people know about them, want them, trust them, and can pay for them. For a major new technology, establishing technical viability (including technology, systems concepts, and applications architectures) and economical feasibility (including market demand) are both necessary, but not sufficient steps. In addition, functional safety - both relative and absolute - of the new technology must be established. Risk - real and perceived - is a critical determinant of eventual market demand for a new technology or service. Preliminary assessments of micro waves at low energy density levels strongly suggest that there are no statistically significant risks to health and safety for either people, wildlife or plants within limits
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