3.4.2.1. 3 Assembly Using Manipulator Modules - Figure 3.4-13 is a representative plan for assembling beams for the primary/secondary structure of the antenna. This operation is selected for detailed analysis because it represents the most frequently used operation in the buildup of structure. Manhour requirements to perform this operation represents 40 to 50% of the assembly cost of the antenna. Statistical data on aircraft assembly indicates that structural assembly accounts for 20% of the total cost to produce. The assembly sequence presented in Fig. 3.4-13 assumes the use of a free flying manipulator module which could be manned or remotely controlled from the ground. Astromast beams are assumed stored in a logistics area in the retracted condition. The astromast storage area is also representative of the location of an auto beam manufacturing unit. The assembly joint is assumed to be a mechanical locking device similar to a docking drogue. The objectives of the operations analysis are as follows: • Establish a rough order of magnitude range of time required to assemble the structure • Establish a level of complexity between performing assembly from the ground and manually in orbit • Establish typical consumables requirements for ancillary equipments used in assembly. Figure 3.4-14 summarizes the maximum and minimum time required to acquire a beam from storage, transport to the assembly area, join the beam to the structure and return to the storage area. A minimum time of 23. 5 minutes and a maximum time of 46 minutes has been established assuming a manipulator design similar to the Shuttle RMS. The minimum time represents the potential of a manipulator to perform the required tasks assuming perfect accuracy and totally static conditions. The maximum time was established utilizing the parametric data in Ref 24 which relates the ratio of performing a basic task in a static environment to the time required to perform the task in a dynamic environment. The parameters considered in establishing complexity factors include: • Control system frequency of the manipulator and target • Attitude limit cycle amplitude of the target • The distance between the target attachment point and the target eg • The position and velocity accuracy during stationkeeping • Manipulator time delay.
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