the startup phase. SVs will probably be used extensively for assembly work and for cargo handling. The onboard systems will be support structures; information systems; materials handling equipment; an attitude control system; and a thermal control system. As before, power will be treated separately. Propellant Depot. Principal variables are types of propellants, storage time, acceptable losses, and peak quantitites to be stored. The basic systems required are essentially fixed, however, and include storage tanks, onloading and offloading docks, pressurization systems, pumping systems, information systems, attitude control, and thermal control. Power is treated in the following section. Power Systems. All of the above subsystems of the LEO Base require electrical energy to operate their individual systems. Whether distributed or central, the required power systems have several features in common. The fundamental energy source may be either solar, nuclear, or chemical. Past studies have shown solar and nuclear to be superior under such circumstances, and only these two will be considered further here. About forty of every ninety minutes will be spent in the Earth’s shadow. For a system with high power consumption, this results in very demanding storage constraints, roughly doubling the size of solar array required, in turn affecting radiator size requirements. Studies in the late 1960s and early 1970s of conceptual designs for LEO bases of various sizes showed a strong preference for nuclear power sources when the population size exceeded about twenty people. 2.3 Geosynchronous Earth Orbit Base The GEO base for SPS will, in many respects, have great commonality with the LEO base in the living/working quarters, materials stockpile, and propellant depot. A notable exception is the radiation protection of crew quarters which may in turn affect other systems. The radiation environment of GEO will require more structural full-time shielding and a solar flare shelter. The living quarters provide for 480 (silicon option) to 680 people (gallium option), who are rotated in groups of 160 passengers after a three-month tour of duty.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==