Fig. Cl. Model of space industrial transportation network. steps: mining, refining, manufacturing, and assembly. This model results in a system as shown in Figure Cl. The four steps are each associated with a “site”, numbered in the order in which material passes through. Thus, mined material (site 1) is refined into raw feedstocks (site 2), manufactured into parts (site 3), and assembled into a completed SPS (site 4), after which it is placed on station in geosynchronous orbit. Each site is specified by a set of parameters which identify its operating characteristics. It was found that each manufacturing site could be adequately modeled with nine such variables: Productivity of the crew (kg/man hr) Productivity of the machinery (kg/hr/kg of machine) Fraction of thruput (kg out/kg in) Fraction from earth (kg from earth/kg out) Crew rotation to earth (times/yr) AV from site to earth (m/sec) AV from site to next site (m/sec) Specific impulse of propulsion system to next site Inert mass fraction of transport to next site. ------------- ---------- —-------I---- - — ——------ Thirty-six variables are therefore needed to specify the site production parameters. However, this still does not specify the entire system; there is a need for a set of system-wide variables which relate quantities independent of site: Number of SPS produced per year Setup time of production system (yrs) Period of SPS production (yrs) Exponent of learning curve (—) Crew wages ($/man yr) Multiplying factor for support overhead (—) Specific impulse of crew transport vehicles (sec) Inert mass fraction of crew transport vehicles (—) Specific impulse of bulk cargo transport vehicles (sec) Inert mass fraction of bulk cargo transport vehicles (—) Crew training costs ($/person) Mass of modular housing unit (kg) Mass of individual crewman (kg) Crew per housing module Discount rate (—) Earth consumable usage rate (kg/man day) Cost of launch to low earth orbit ($/kg) Research and development costs ($) Transport mission case number (used in computer program) These 19 system variables, along with the previous site-specific variables, comprise a set of 55 parameters which totally specify an industrial scenario for the SPS within the limitations of the model. Transportation assumptions may be seen by again referring to Fig. Cl. These assumptions are: All cargo between sites travels one way only (this is violated only in the case of shipping oxygen from
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