L. Jenkins Spacecraft Design Div. V. SPS CONSTRUCTION AND MAINTENANCE SYSTEM A. System Requirements and Analysis 1. Summary Study of SPS construction concentrated exclusively on the photovoltaic configurations, however, construction of thermal conversion configurations appears to be analogous. The large size and low density of an SPS and the advantages of designing for operational loads rather than launch loads dictate an orbital fabrication and assembly approach to construction of the SPS. The complex elements or components such as antenna rotary joints and control system modules can be manufactured on the ground for assembly into the overall system. Other components such as the microwave generators, solar cell blankets, concentrator sheets and power distribution harnesses are amenable to dense packaging for launch and deployment in orbit. SPS structure is a low density in its final configuration when designed for orbital loading conditions. The packing density of fold-deploy systems is much too low for efficient operation of the transportation system. In addition, structural joint design and launch loading conditions have an adverse effect on structural weight. An alternative is to manufacture the structure in orbit. Automatic machines generate structural elements from preprocessed stock. Combinations of the machines are utilized to build trusses for the primary structure. Another candidate for orbital manufacture is the antenna subarray. The waveguides of the phased array must be built to very precise geometry, yet the finished product has very low density. By fabricating the subarrays in orbit, problems with launch loading and low density packaging can be avoided. The large size of the SPS requires a high degree of automation to achieve the necessary construction rates. The construction crew can be best utilized in servicing and maintaining automated equipment, evaluating the operation and output, and performing contingency operations. The construction and support crew operate a construction base consisting of construction and manufacturing facilities, orbital construction and support equipment, logistic facilities, integration management facilities, and crew habitation facilities. The configuration and sequence of construction will generally define the requirements for the construction base. The structural concept may be modified from an optimum design in order to simplify construction. Requirements for orientation of the concentrator arrays in the perpendicular to orbit plane (POP) configuration is an example of configuration influence on construction procedures. From the construction
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