• Refine structure/control interaction analyses to better understand the dynamic behavior of very large structures; and. • Identify the minimum weight vehicle system having acceptable structural stiffness and pointing capabilities. Before proceeding to a more refined analysis of the SSPS configuration's dynamic behavior, better definition of the vehicle structure is required. In order to do this, analyses of the implications of assembling the SSPS in orbit are needed. Specific considerations are: (a) attitude control during assembly, (b) docking closure rates and the resulting induced structural loads, (c) joining techniques for electrically conductive and non-conductive structures, and (d) structural element packaging and deployment. In addition, refined analyses of the dynamic behavior of the spacecraft should consider: (a) the effects of rapid thermal transients, (b) local excitation of the structure by the attitude control system thrusters, (c) structural non-linearities, (d) centrifugal and centripetal effects, and (e) torsional modes and modal cross-couplings. These efforts should ultimately be focussed on the identification of the minimum-weight spacecraft system and structure having acceptable structural stiffness and pointing capabilities. RFI Avoidance Techniques Conclusions. — It is possible to select a near optimum range for the fundamental frequency for the SSPS to minimize interference with other users. At the selected frequency, the design of microwave generating devices, such as the amplitron and associated filtering, can be pursued with confidence. The RFI avoidance techniques were investigated on the basis of a model and a set of assumptions for the microwave transmission systems. The model included orbital and ground locations, ground power transmission, device characteristics, phase front control, efficiencies, induced RF environment, ionospheric and atmospheric attenuation, major frequency segments, specific frequency, typical users, and selected equipment. The noise associated with the generator, a transmitting antenna, and a filtering system placed between the antenna and the generator was found to be acceptable with other users such as troposervice, radio astronomy, and fixed microwave installations for up to 100 SSPS's. Slight RFI can be expected for shipboard radar, while amateur sharing, state police radar, and radio location from high-power defense radar will suffer substantial interference. Recommendations. — The following tasks will require further study: • Detail design of devices, including filters and estimates of associated costs to assure that the design goal for noise and harmonic filtering can be met within the constraints of weight and cost.
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