Lighting the space station can be accomplished very easily because this requires almost no mechanical equipment can be achieved directly from the sun, which after all shines incessantly, disregarding possible, yet in every case only short, passes by the space station through the Earth's shadow.
For this purpose, the walls have round openings similar to ship's bull's eyes (Figures 60 and 61, L) with strong, lens-type glass windows (Figure 78). A milkwhite coloring or frosting of the windows, and also an appropriate selection of the type of glass, ensure that sun light is freed of all damaging radiation components, filtered in the same way as through the atmosphere, and then enters into the space station in a diffuse state. Therefore, the station is illuminated by normal daylight. Several of the bull's eyes are equipped with special mirrors through which the sun's rays can be directed on the bull's eyes when needed (Figure 79). In addition, artificial (electrical) lighting is provided by extracting current from the solar power plant.
Figure 78. Lighting bull's eye.
Key: 1. Interior of the station; 2. Diffuse light; 3. Sealing material; 4. Bracing; 5. Solar radiation; 6. Empty space; 7. Glass lens.
Figure 79. The mirror reflects the rays of the sun directly on the window.
Key: 1. Mirror; 2. Solar radiation; 3. Window and interior of the space station.