struction of the SPS will rely to an unusually high degree on modeling and dynamic analysis. The panel feels that substantial further work is required in the areas of modeling the system components and environment. These models are required to study the uncontrolled behavior of the spacecraft and to provide a basis for the control system design, development, and evaluation. It may be necessary to predict reliably hundreds or thousands of structural frequencies, mode shapes and damping ratios. Currently modeling procedures for structural dynamics are not so clearly established as to be able to estimate the reliability of a particular eigenvalue and eigenvector. Environmental disturbances and control hardware must also be modeled to assess system behavior and for suitable control system design. Current SPS structural designs utilize forms which basically derive from 19th century bridge-building technology (not necessarily bad). As the overall concept evolves, as communication is developed between structures, materials and control specialists, and as an understanding of construction in space is developed, it is anticipated that more advanced concepts which exploit the potential of the nearly benign environment will emerge. To approach this evolution, however, the panel felt that the controls problem had received disproportionately little attention. This included: recognition of modeling limitations as a key issue, tradeoffs among active surface control, tradeoffs between the bounds of structure and control, tradeoffs between electronic phasing and active figure control, analyses which penetrate to adequate depth for specific controls hardware considerations, and means to accomplish verification of the controlled system design. The controls problem for construction is compounded by the additional parameters of transient geometry and performance requirements. A feature of the SPS which sets it apart from all spacecraft launched to date is the fact that it must be constructed automatically in space. Our lack of experience with systems of this type merits careful consideration of this feature. The construction phase may in fact be critical in terms of establishing structural and control system design requirements. The panel felt that much additional work was required to provide a confidence level necessary for the selection of graphite composite as the SPS structural material. There are a number of design/structure/material tradeoff studies which should be performed. The basic question of the long term stability of materials and coatings in the space environment is crucial. As outlined in Figure 8, the nature of the SPS is such that the design and proof of feasibility will rest primarily on a foundation of analysis. However, experiments are needed to verify the results of analysis insofar as possible. These experiments should be directed toward verification of modeling techniques, validation of control policies, and determination of material properties.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==