receiver assembly and power conversion unit assembly. Incident solar energy flux is reflected by the concentrator into the receiver's cylindrical cavity. This cavity includes 82 tubes carrying pressurized working fluid that absorbs the solar energy. Upon leaving the receiver, the working fluid expands through the turbine which drives the compressor and the alternator. The fluid from the turbine flows through a recuperator heat exchanger and a gas cooler before it enters the compressor. The compressor outlet fluid re-enters the recuperator where it is heated prior to closing the cycle in the receiver. A simplified block diagram of the receiver and PCU is shown in Fig. 2. This thermodynamic cycle is bounded by a source temperature at the receiver outlet and the temperature of the surrounding space environment. Waste heat is transferred to the solar dynamic radiator through the gas cooler heat exchanger. Solar Dynamic Radiator Description The SDR is part of the heat rejection assembly which collects and transports the SDPM-PCU and electronics waste heat, and rejects it to the station orbital environment to maintain appropriate SDPM components and electrical equipment within required temperature ranges during operation. The heat rejection assembly also includes a fluid management unit and fluid interconnect lines. It has a redundant loop with full heat rejection capability to meet reliability requirements. The SDR consists of eight panels deployed automatically with a motor- and gear-driven scissors mechanism. Each SDR panel is a bonded aluminum structure. Extruded aluminum tubes carrying coolant are bonded between aluminum face sheets which act as radiating fins. Aluminum honeycomb fills the interstices. The coolant tubes are welded into manifolds at the panel ends. In the baseline configuration, the SDR panels are 8.4 m by 2.6 m (27.6 ft by 8.7 ft). The size of the SDR panels is constrained by packaging considerations in the space shuttle cargo bay (maximum) and the required radiative area to reject the thermal load (minimum). In its deployed position the baseline SDR is located in front of the concentrator reflective surface edgewise to the incoming solar rays (see Fig. 1). During the insolated portion of the orbit, the SDR casts a narrow shadow on the concentrator's surface. This shadow accounts for up to 3% of the total concentrator reflective area. Since the shaded portion of the concentrator does not transfer energy from the concentrator to the receiver cavity, it is more difficult to achieve the desired flux distribution within
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