Proceedings PaperThe Development Of An Inflatable Reflector For The External Tank Gamma Ray Imaging Telescope (ET-GRIT)
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NASA's Marshall Space Flight Center is currently investigating a concept for a Gamma Ray Imaging Telescope using the space shuttle external tank. One of the major difficulties with this concept is the construction of the 28 ft. diameter spherical reflector used to concentrate the rays onto a collector. Because the access hatch through which all components of the telescope must enter the tank is 3 ft. in diameter, a rigid glass reflector would have to be segmented into individual panels of less than 3 ft. in diamater. This would result in a reflector of substantial weight and complexity in assembly. To overcome the problems involved with a rigid reflector, a concept has been developed in which an inflatable reflector can be used. A reflector of this type, attached to an inflatable torus could be designed to be transferred into the tank through the access hatch and then inflated. ILC Dover, Inc. has designed, fabricated and tested a 1/4 scale thin film inflatable reflector for use in the External Tank Gamma Ray Imaging Telescope. The prototype reflector is a 7 ft. diameter section of a 14 ft. radius sphere. Reflector configuration and seam studies were conducted to determine the optimum configuration for the reflector. The reflector is constructed from eight gore shaped panels and a 7 inch octagon in the center as determined by the "shadow" of the collector. The gore sections are designed to account for material elongation both circumferentially and radially so that the desired shape of a sphere was achieved.