10.8 X.2.5: Structures: *l) Properties of Space Alloys: What are the properties of space-made alloys, particularly steel? What are their fracture toughness and fatigue characteristics? How are these properties altered by long-term exposure to the space environment? 2) Cable Structures: What are the mechanical, dynamical, fatigue and fracture properties of proposed matrices for cablewound structures? What repair methods are needed for such structures? How stable are structures supported by cables under tension, such as spinning mirrors and solar-cell arrays? Can oscillations cause failure? How can these oscillations be damped out? 3) Vapor Deposition: Can the vapor deposition process be applied to hardenable alloys, such as steel and high-stress aluminum alloys? What are the mechanical, dynamical, fatigue and fracture properties of vapor deposited components? x.·2.6: Systems: 1) Enerqy Management: What thermal and humidity control systems can efficiently maintain comfortable environments in colonies? What alternatives to direct sunlight can grow plants? Are these desirable? What safety criteria must energy management systems meet? 2) Rotating Bearings: Can fail-safe, cost-effective rotation bearings capable of joining multi-ton sections of colonies be designed? How can they be lubricated? How can they be inspected and repaired? What active controls do they require? What experiments are needed to demonstrate the feasibility and cost-effectiveness of these designs? 3) Nutation and Uncontrolled Precession: How do nutation and unwanted precession of rotating structures affect the pointing accuracy of the spin axis? What loads do they apply to the structure, particularly on structures (booms, cables, rotation bearings) connecting sections of colonies? X.2.7: Construction and Maintenance: *l) Human Productivity: What is the productivity of a human worker in zero-g vacuum, zero-g shirtsleeves environment, one-sixth-g
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