8.38 in construction. Because the cabs of the hoist and cranes are mechanically connected to the rest of the construction site structure, any impulse imparted to the site by an acceleration of the cabs is equally and oppositely balanced by the deceleration of the cab. Linear and angular momenta of the system are conserved. The mechanical manipulators should be able to position sections more accurately than a minivehicle could, and the cranes and hoist are driven by motors using electric power and need not be supplied with fuel. Construction operations undoubtedly create some need for space pods and personal maneuvering packs, but detailed work on this problem was beyond the scope of this study. It is, however, strongly suggested that any system of this type gives the operator control over position and/or velocity and not over acceleration as has been the case on most space maneuvering systems to date. VIII.7.2.3: Power Distribution Network: The space truss booms, frame, and mast provide a natural path to distribute the power from the photovoltaic array to the construction shacks, living quarters, hoist and cranes. The actual power is carried in busbars or large cables incorporated into the space truss structures. The voltage and frequency of the power generated and used at the colony depends on several factors. Solar cells favor the use of DC power while any closed thermodynamic cycle plant driving a rotating generator would favor AC power distribution. Direct DC has higher related transmission losses but, since the greatest distance that must be crossed in only 650m, this does not appear to be a major problem. Direct current voltage is impossible to amplify at room temperature. On the other hand, most of the electrical equipment uses DC, including the motors of the rolling mills, the electron beam welding guns, and the electrolysis cells in the refinery. If an AC distribution system is used, the likely frequency candidates are 60 Hz, now used in the USA, and 400 Hz and 100 Hz, which are used on aircraft. Motor weight decreases with increasing frequency, but impedance losses increase.
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