will be needed to ensure re-entry safety, since current GPHS container designs utilize a fusible link which allows the blocks to be ejected and dispersed. In this concept the FSA releases the GPHS blocks after the multilayer foil has been stripped away. Figure 8 depicts the dual 500 watt, fully redundant FPSE installation attached to the rover vehicle. The radiator basket enclosing the heat source/engine assembly contains two cooling loops. Performance and mass breakdown for this system is summarized in Table VI. Mars Background Sink Temperature The specific power of the Mars Brayton and Stirling cycle conceptual designs are lower than those designed for LEO applications because the thermal background seen on Mars surface is considerably higher than the 220°K equivalent sink temperature of LEO. For example, the range of Mars atmosphere temperatures measured by Viking lander was 190-240°K. IR measurements of surface temperatures observed during the Viking primary mission ranged from 130-290°K. Bearing in mind that radiators would probably have to be mounted on the bottom of the vehicle (the upper surface must remain unobstructed for sensors, communication antennae, etc.) the radiator heats the ground beneath the vehicle which returns an elevated surface temperature. For a stationary vehicle this elevated background could easily exceed the ambient background by 20-30°K. Considering the above factors an equivalent sink temperature of 290°K was selected for design purposes. Effect of Elevated Background Temperature An elevated temperature background has a major impact on the performance of a
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