There is a need for a large deployable reflector of 2-meter diameter or greater so smaller launch vehicles can be used. Common issues with going from a large solid reflector into deployable structures are the structural stiffness and deployable structure complexity.
The hybrid reflector design in this report stems from the desire to have a 2- meter-class reflector that compactly stows in small launch vehicles, but also has the capability to accommodate a large range in RF frequencies. This reflector needs to work with frequencies from 6.8 to 183 GHz. To be effective at the high frequencies, the design utilizes a solid precision center on the order of 70 cm in diameter. This solid precision center will be for the specific frequencies of 23.8 to 183 GHz. In order to accommodate the longer wavelength channels, the reflector has a deployable collar that surrounds the hard center. This deployable collar, when combined with the hard center, makes up the full 2-meter diameter for the specific frequencies of 6, 10, and 18 GHz.
Because of the hybrid style of the reflector, with a large central hub area, an obvious initial design concept for deployment of the 2-meter diameter was a wrapped rib configuration. Several initial analyses were performed on the reflector design. The first was a strain analysis of the stowed reflector configuration. In this reflector concept, inherent strain energy from the wrapped ribs allows them to deploy. Therefore, the ribs need to be sufficiently thick to provide enough energy for a robust deployment of the reflector. However, the ribs can't be too thick, because then their stowed strain and resulting stress would be too large. A simple geometric strain calculation was used to size the thickness of the ribs. Using this formula and calculating several resulting strain rates yields a range of potential rib thicknesses.
The reflector does not use complicated deployment mechanisms. It contains a precision solid center for high-frequency RF channels and a deployable mesh collar for lower-frequency RF channels. This hybrid design allows the reflector to be capable of a wide range of RF frequencies. As designed, it would cover 6 to 183 GHz. Support of the mesh is provided by a simple network of cable stays and support ribs, which provide the strain energy from stowage to deploy the reflector.