Design, Testing, and Analysis of a Deployable Composite Telescope

To develop a deployable optical telescope, composite tape springs were designed to replace the traditional metal support truss of a Newtonian telescope. Tape springs are thin-walled beams composed of layers of carbon-fiber-reinforced plastic and are noted for their high specific strength and deployability; both properties are advantageous in aerospace applications where weight savings outrank material costs. Testing and finite-element modeling of the composite telescope demonstrate that the horizontal displacement is small enough to allow the telescope to function adequately for ground-based observations after stowage and subsequent deployment. The composite parts were fabricated in the Air Force Research Laboratory at Kirtland Air Force Base. Testing of the structure was performed with the telescope at both a horizontal and vertical position. To enable both tests, the tape springs were attached to aluminum rings. Vertical-orientation testing allowed for the deployment accuracy of the structure to be examined by recording positions on the telescope before and after deployment using dial gauges. For the horizontal testing, dial gauges and weights were used to measure the displacement due to the measured self weight (optics and housing) of the secondary mirror housing. The paper will discuss the design challenges posed by the conflicting demands for deployability and stiffness and findings from testing and FEM analysis.