2. No scattering of reflected light by mirror surface irregularities. 3. Perfect mirror pointing. Assignment of probable values to these three factors indicates that actual target areas would be approximately 20% larger than the ideal image size indicated. Potential target area were sought with a goal of minimum population in the image area. Two "best" sites were identified; one is in the southwest desert near the Mexican border; the other is near the Canadian border. Approximately 70,000 and 50,000 persons live in, respectively, the low and high latitude sites. Figure 5-34 shows the low latitude target area for the power relay system. Image sizes were calculated for three United States latitudes (X). The images are elliptical, with the long axis running parallel to lines of longitude. Image sizes are given in Table 5-8; dimensions a and b are, respectively, the semi-major and semiminor axes: Unless moved out of the target area, the occupants would be exposed to the full environments effects produced by having a one sun average illumination continuously (unless blocked by clouds). The average surface temperature would tend to rise to approximately 150°F. The mirror itself must have a curved surface in order to maintain the required image. If composed of individual facets on a flat base, each facet must be oriented so that all images are superimposed. The edge facets are tilted the most, by 0.13 relative to the mirror plane. Some form of active tilt control would probably be required. To provide a reflected solar image of one sun intensity, a mirror having at least the same area as the ground target is required; it would have a system mass of 4 x 10^ KG (45,000,000 tons). Over 106 kW of on board power generation capacity would be required to drive the electric thrusters necessary to overcome the "solar sail" thrust forces. Fig. 5-34. Shows the Low Latitude Target Area for the Power Relay System Table 5-8. Tangent Plane Image Size for Various Latitudes
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