2.2.4.2 Structural Assembly Analysis concentrated on the most frequently used operation in the antenna structure assembly, namely, the time and motion assessment of joining beams. Assembly costs are generally a strong function of the quantity and complexity of the assembly operation. In the estimate, for example, of aircraft structural assembly, the major cost driver is the number of parts and the type fastener used. In the antenna structure and waveguide interface design, simple mechanical locking mechanisms similar in concept to a docking probe/ drogue was utilized when possible. Since most of the assembly will involve this type of operation, detail evaluations were performed on this beam assembly procedure. Figure 2-23 outlines the antenna structure assembly flow. Assembly starts with installation of the rotary joint using the solar array central mast as the point of departure. The rotary joint to antenna interface follows, using the elevation rotary joint structure as an assembly base. Assembly of the primary and secondary structure is performed working radially from the center of the antenna. Installation of waveguides and electronics follow. The alternate approaches evaluated include use of: • Manned manipulator modules • Remote controlled manipulator modules • EVA with assist from remote controlled logistics modules. The operations analysis approach is summarized in Fig. 2-24. The functional steps in the operation for the three options were identified and a time line analysis performed to determine the range of potential assembly rates. Estimates of consumables consumption of the free-flying modules were also made. Past Grumman simulation data, which relates complexity of manipulator operations in a static environment to operations in a dynamic environment, was used in estimating both manned and remote controlled manipulator performance. Skylab 3 data on the human performance in assembling the twin pole sunshade was used to estimate EVA assembly rates. Figure 2-25 summarizes results of the operations studies. The following conclusions were drawn from this data: • Remote controlled manipulator assembly offers the most cost effective approach • EVA assembly with remote controlled logistics vehicles could be cost competitive if assembly times in excess of two years is acceptable and Space Station costs for a 50-man crew can be shown to be reasonable
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