Assembled engineering model concentrator panel frames are shown in Fig. 7. This hardware was developed as part of the advanced development phase of the Space Station Freedom program. Self-locking ball-and-socket latches located at the panel corners connect the panels together to form the complete reflector. The reflector thus assembled is about 18 m (55 ft.) in diameter. The facets will be installed in the panels and aligned on earth before launch into orbit. A nine-strut structure supports the assembled panels. Three of the struts form a delta frame and provide stiffness to the panel assembly. The remaining six attach it to the two-axis gimbal rings. These gimbal rings together with linear actuators and a closed-loop control constitute a fine pointing system which will keep the concentrator pointed to within + or —0.1 degree of the true sunline. The total mass of the concentrator complete with all structure and controls is expected to be about 1500 kg (3300 lb). A more complete description of the concentrator can be found in Ref. [1]. Receiver. The receiver, located near the focal point of the concentrator, is the second link in the SD power process. As shown in Fig. 8, which is a photo of a model, and Fig. 9, the SD heat receiver is cylindrical in shape. It consists of a cavity lined axially with tubes through which the gaseous working fluid of the Brayton cycle flows. Each individual tube is surrounded by thermal energy storage means. Solar energy enters the receiver through an aperture in one end. This aperture is sized to optimize the collection of focussed energy from the concentrator while limiting the amount of that energy which is reradiated out of the aperture. The gaseous working fluid enters the cavity region via a toroidal header at the aperture end of the receiver. It makes a single pass through the tubes and is then collected in an outlet header at the closed end. From the outlet header it flows to the Brayton power conversion unit which is mounted on the outside of the closed end. The canisters surrounding each receiver tube contain a eutectic salt mixture of 80.5% Lif—19.5% CaF2 (by mole). The heat of fusion of this mixture is the thermal energy storage means. The total amount of salt in the receiver is sufficient to store the
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