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avoidance of the overturning moment deficiency of the initial prototype design, and would also provide an added advantage of the upper transparent cover providing wind and precipitation protection for the reflective surface. The new configuration also has the advantage of providing a good aerodynamic shape. It has a relatively low drag coefficient, does not generate unwanted lift forces, and has the same aerodynamic properties from all directions. In addition, all aerodynamic and inertia forces act directly through the support system.

It was recognized that an added potential issue with this design refinement would be the effect of the transparent upper cover on distorting or diminishing the reflected light beam, and the principal investigators decided that this potential issue should be examined with suitable component and subassembly evaluation, prior to construction and test of a full prototype incorporating the design refinement.

A subassembly was built with a focusable stretched membrane reflector, and a removable transparent acrylic dome to serve as the transparent upper cover (Figures 5a, b). A subassembly evaluation was conducted, and indicated that the reflected light beam distortion was modest, when the reflector was in a focusing configuration. In view of these encouraging results, the principal investigators decided to go ahead with the detail design, fabrication and test of a refined prototype incorporating the preferred design refinement concept.

Figures 5a, b – Acrylic Dome Test

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November 24, 2002

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