The analysis techniques for complex structures has reached an advanced stage of development using methods such as NASTRAN. The dynamic characteristics are of great importance in structures of this size as they have a profound influence on the flatness of the transmitting antenna and its pointing accuracy. Although the natural frequency is very low, of the order of 4 cycles/h, the corresponding accelerations at the extreme edges of an array 10 km long are high and could cause considerable embarrassment and difficulties to maintenance workers. The thermal analysis of the structure is of similar importance particularly on the transmitter antenna where a close tolerance on flatness is essential. In the case of the SPS, a new factor must be considered, and that is the analysis of a structure that is growing at a surprisingly rapid rate, a form of stochastic dynamics. Some of the critical structural technology tasks that will need attention are • A fuller understanding of the dynamic and thermal loading environment • Identification of cost-effective construction systems including assembly • Automatic construction methods including robotics • Alignment procedures and equipment • Identification of materials regimes • Structural dynamic interactions with control systems including thermal effects • Optimum structural configurations • Flight demonstrations of the chosen technologies • Testing, inspection and repair. The last point dealing with testing has far reaching implications. As the structure must function in a zero# environment, this implies that it will be very light although stiff. It is virtually impossible to expect that such a large, very light, structure can be built in the normal one-# laboratory environment and then subjected to representative environmental tests, therefore recourse is expected to be made to scale modelling and to combine this with a comprehensive analytical programme. Final verification will have to be carried out in orbit, but this should be preceded by extensive and progressive flight testing in Shuttles and the early developments of small space construction bases. In fact, this was anticipated by Grumman in their concept of an Orbital Construction Demonstration Article (OCDA) which proposes to use the large Shuttle external tank as a “strong back” for a small space construction base (SCB). The experience obtained so far on extra vehicular activity (EVA) by astronauts has shown that man’s (or woman’s) ability to perform relatively complex construction tasks is limited. The SPS, as presently conceived, will require a comparatively large number of space workers to support the mainly automated large-scale construction tasks. It is felt that a considerable effort should be applied to improving these skills with the provision of more automation and robotic equipment at the lower level of hand tools. Referring again to the comparison with large civil engineering construction projects, the support equipment such as large cranes, manipulators, manned remote working stations, including their life support systems all have their own detailed technology development requirements. While it now seems feasible to produce very long beams automatically, there will be a requirement to develop docking, alignment, and measuring equipment capable of working over comparatively long distances. This equipment will include methods of controlling the beam’s movements during the final connecting task, bearing in mind the normal natural dynamic behaviour of very long beams. POWER TRANSMISSION As far as European power reception from an SPS is concerned the really critical
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