Elastic Folding of Reflector Antennas

The Hughes Spring Back Reflector Antenna. The Hughes Space and Communications Company (which is now known as Boeing Satellite Systems Inc. part of Boeing ) has revolutionized the field of deployable antenna structures by developing the so-called Spring Back Antenna shown schematically in Figure 1. This new concept consists of a thin walled graphite mesh dish -made from material with a triaxial weave with an integral lattice of ribs and connecting elements, with a stiffening hoop along the rim. The whole structure is elastically folded about a central axis, like a taco shell. This folding concept is both simple and effective; the whole reflector is made as a single piece, without expensive and potentially unreliable joints, and can be stowed in the normally unused space in the nose cone of the rocket launcher. In orbit, the tie cables that hold the reflector folded are released, and the reflector deploys dynamically by releasing its stored elastic strain energy.

Spring back reflectors need to have low stiffness in order to be foldable, but their low stiffness makes it difficult for them to achieve and retain high shape accuracy. Furthermore, shape distortions that occur during the manufacturing of thin graphite structures, of order D/1000 in the present case, make it even more difficult to meet the stringent shape accuracy requirements imposed on communications antennas. This is a significant problem, and potentially a severe limitation on the applicability of spring back reflectors. The surface of the reflector can be adjusted with relatively simple mechanical devices, but this defies the simplicity of the concept and reduces the reliability of the complete system.

We propose a modification of the original spring back reflector concept, based on the idea of adding a thin walled stiffening element around the edge of the dish ( Figure3) . This element significantly increases the overall stiffness of the dish in the deployed configuration. One subtlety which is included in this concept is the fact that the stiffening element is only attached to the edge of the dish at certain lengths hence its configuration is such that the stiffened dish can still be folded elastically. Please follow this link for further details IASS conference paper. The result is a system for which the stiffness can be tuned to suit one's needs.