10.2 accidental damage and to guarantee a lifetime of 30 years, the study group concludes that the desirable approach is the Fail Safe concept. This requires that the structure be damage tolerant, in that failure of one section cannot endanger the structural integrity of the whole colony. The possibility of multiple section failures endangering the colony's structural integrity led the study group to adopt the Leak Before Break criterion, so that air escaping through a hull section could be detected before failure of that hull sectio~. The study group also concludes that any colony design requires detailed dynamic stress analyses to investigate the fatigue effects of cyclic loadings on the structure. These should include the effects of perturbation forces and irregular mass distributions in a rotating hull. Fracture mechanics studies can then evaluate the longevity of the structure as dictated by fatigue. In the specific design proposed, such dynamic analyses, the wish to avoid disruptive emergencies in the colony routine, and the desire to make hull repair a simple process led the study grou~ to a d~uble-hull configuration. For the general case of space colonies, the study group concludes that the structural design criteria shoul1 .b~ static load, fatigue, damage tolerance, longevity, and ease of repair, leading to the mor~ specific Fail Safe and Leak Before Break requirements. For each colony design, one structural criterion will suggest the largest hull thickness; this value should be adopted. The study group also concludes that the double-hull construction is highly desirable. In the MIT Prototype Space Colony, applying the Fail Safe criterion leads to a hull thickness slightly larger than that needed to satisfy Leak Before Break, and considerably larger (roughly 8 times) than that needed to satisfy static loading requirements. So thick is this double-hull that incorporating the radiation shielding (with area density 5000 kg/m 2 ) within the spinning hull does not cause a significant structural mass penalty. Safety and energy management benefit greatly from this inclusion of the shielding, since it eliminates the possibility of accidental contact between spinning
RkJQdWJsaXNoZXIy MTU5NjU0Mg==