3.9 CREW SIZES AND ASSEMBLY SEQUENCE The estimate of crew sizes and the derivation of an assembly sequence was significantly impacted by consideration of facility designs, machine operating rates, material demand requirements, and transportation system capabilities. Major assumptions had to be made in each of the areas. Early conceptual analyses and trades pointed to the process flexibility of providing three facilities (e.g., structures, blanket/reflector, and microwave antenna). Since each facility had its own receiving/docking area, this (with proper sequencing) minimized inter-facility logistics requirements. Also, reasonable shutdown times at one facility would not delay operations at the others. The dominant assembly time driver is the rate at which the dispensing machines operate. Operating rates were assumed at 2 meters per minute, or approximately l/20th man's walking speed. Using structures assembly as an example, at a longitudinal production rate of 2 meters per minute, a 600-meter bay length can be produced every 5 hours. Assuming half a shift (4 hours) is required for joining frames at the end of each bay and performing adjustments, then nearly 2 hours can be allocated for machine downtime per bay. Although there are 150 beam fabrication machines, they are relatively simple, low power, roll-forming devices, and a 40-percent downtime (versus operating time) for the complex should be a reasonable assumption. In a like manner—using the same limits on production rates of 2 meters per minute—the solar blanket and reflector facility and microwave assembly facility times and sequences were developed. By time-sequencing the construction phases of each facility (Figure 3.6-5), a 90-day assembly cycle was achieved. Crew size requirements was based on an 8-hour work day, 7 days a week and a 3-shift operation. At the structures facility, it was determined that each of the 11 machine complexes would require an on-site monitor/operator with a roving two-man crew to aid at any complex. At the central facility, another three-man crew would monitor all activities. Central logistics would be handled on three shifts by five-man crews with one foreman for all shifts. The support crew (captain and crew, medical personnel, cooks, etc.) were estimated at 16 persons. Thus a total crew size of 80 is the postulated requirement for the structures facility. Similar estimates were developed for the blanket/reflector and microwave antenna facilities, resulting in crew sizes of 96 and 48, respectively. These estimates are "soft" primarily because of study time constraints (as opposed to "technology" constraints). However, when evaluated in the context of technical feasibility and economic viability, the crew sizes—per se—are less an issue than construction time, and emphasis was placed on developing realistic construction equipment and achievable assembly processes. It is felt that further detailed study could, in fact, reveal areas of greater productivity and result in minimizing these demands.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==