Long-lived Venus landers require power and cooling. Heat from the roughly 64 General Purpose Heat Source (GPHS) modules must be delivered to the convertor with minimal ÄT. The cooling system must be shutoff during the transit to Venus without overheating the GPHS modules. This program will develop an alkali metal Variable Conductance Heat Pipe (VCHP) integrated with a two-phase heat collection/transport package (HTP) between the GPHS stack and the convertor. The VCHP allows the Stirling converter to be shutoff during transit to Venus. The two-phase HTP minimizes the temperature drop between the multi-GPHS stack and the heater head. The HTP is required due to the large number of modules that must be interfaced, and the low allowable ÄT between the heater head temperature of 1200o
C and the maximum allowable iridium cladding temperature in the GPHS (1266o
C). The HTP also improves the convertor efficiency by decreasing the temperature non-uniformities at the high heat flux interface of the hot end of the heater head. It is superior to pumped liquid systems for transferring heat, because it eliminates the low efficiency liquid metal pump that they require. Other advantages of the system include low mass and volume, and a high degree of redundancy.