LoadPath (United States)

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

This paper presents concept designs of a diffraction-based optical telescope compatible with the CubeSat program volume specifications. Simple geometric ray-tracing equations are presented showing the allowable out-of-plane deformation of a transmissive diffractive optic are two orders of magnitude greater than that of a reflective based system. However, the relaxed requirement comes at the expense of relatively large focal lengths, and no advantage is gained for allowable in-plane deformations. The structural requirements of the primary optic are flowed down into the prototype designs of the membrane optic and deployable structural system. The optic was designed to be fabricated from a monolithic membrane with removed regions such that the optical area is subjected to a uniform biaxial stress field. The deployable structural system utilized self-deploying bistable tape spring members that can package into 1U CubeSat volume.

CASPAR, the Composite Adapter for Shared Payload Rides, is a Multi-Payload Adapter (MPA) that was developed for the Minotaur IV Launch Vehicle. The CASPAR MPA can accommodate two 1500-lb satellites or four 400-lb satellites on a Minotaur IV. The structure was tested to failure, after surviving qualification testing, at the Air Force Research Laboratory as part of a larger program intended to determine the ultimate capacity of three large composite structures and to evaluate failure analysis methods. This paper compares the results of the qualification and failure tests in an effort to accurately assess the flight environment equivalence of the applied failure test conditions.

The large strain flexure of 0.135 mm, 0.259 mm and 0.383 mm thick unidirectional carbon fiber reinforced epoxy plates was investigated. Coupons were folded in a U-shape and compressed between parallel platens while platen separation and load were measured up to failure. The test was modeling numerically using a geometrically nonlinear elastica solution method in combination with a two parameter nonlinear elastic material constitutive model based on graphite crystallite reorientation. Using a curve fitting method, the test data was used to estimate model parameters. Test results show a nonlinear material response resulting in bending stiffness softening as curvature increases. Bending failure strains were larger than expected and increased as coupon thickness decreased, ranging from 2.15% to 2.75%. Also unexpected, the failure occurred in a tensile mode on the outside coupon surface, not in a compressive mode. The results indicate thin flexures can be used at strains and curvatures larger than previously thought.