Submicron Mechanical Stability of a Prototype Deployable Space Telescope Support Structure

The results from an experimental characterization of the deployment precision and postdeployment mechanical stability of a prototype deployable telescope support structure are presented. Using novel high-precision metrology and experimental protocols, the experiments separate mechanical imprecision in the deployed geometry from ordinary thermoelastic deformation with approximately 0.2 micron of experimental error. With this resolution, it is possible to observe mechanical motion due to microslip hysteresis in the joints for loads below the Coulombic gross-sliding limit. It is shown that the intentional application of impulses to the structure, following the initial deployment, apparently stabilizes the microdynamics. A model is presented that correlates well with the data. This result suggests that this effect is due to the dynamically induced relaxation of strain energy stored by friction mechanisms within the structure. Additional test data are presented that show microslip in one particular latch of the structure accounts for the observed microdynamic motion and deployment imprecision. These results underscore the possibility that deployed telescope structures can be developed with submicron levels of mechanical error. (Author)