7. 64 structural design. The first of these figures shows the now familiar hull layout: a squat cylindrical section with diameter of 200m and a length of 100m, capped by two hemispheres of radius 100m. At the poles of the hull are an 8m diameter cylindrical docking port and airlock and a 40m diameter window. Also shown schematically are the transverse bulkheads connecting the inner and outer hulls which circle the hull in planes perpendicular to the spin axis. These bulkheads divide the hull into five 20m long rings in the cylindrical section and six spherical annuli in each of the endcaps. Not shown are the longitudinal bulkheads which run about the circumference of the hull in planes containing the spin axis. These bulkheads further divide the hull into 30 sections, each subtending a 12° arc about the spin axis. Thus, the inter-hull space is divided into 510 compartments each bounded by sections of the inner hull, the outer hull and the transverse and longitudinal bulkheads. Figures 7.23 and 7.24 present more detailed drawings of a cylindrical section compartment and one of the first tier of endcap compartments respectively. As shown in these figures, the hull is composed of sections approximately 20m x 20m. These sections are, in turn, subdivided into lm x lm panels which are assembled in a grid separated by minor stiffeners and welded together. The large 20m x 20m hull sections and the 20m x Sm bulkhead sections are attached to the major "T" stiffeners with fasteners. These joint cross sections are presented in detail in Figure 7.25. In addition to the compartment detail, Figure 7.24 illustrates several important features of the colony's interior structures. Since these interior structures are to be built before the hull is spun and pressurized, their supports must be provided with two degrees of freedom to accommodate the biaxial elongation of the hull due to the applied loads. The supports must also be restrained from wandering across the cylinder/endcap joint. The lower drawing of Figure 7.24 illustrates how these requirements can be met. The dimensions of the buildings shown are only tentative suggestions that meet the structural requirements developed in Appendix VII.G.
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