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The Variable Conductance Heat Pipe (VCHP) Assembly of the HST Wide Field Camera 3 was subjected to thermal vacuum (T/V) environmental testing. The test program included both maximum and minimum environments as well as simulated on-orbit cycling. Elements of the VCHP assembly included a VCHP, an optical bench cold plate with an imbedded constant conductance heat pipe, and a VCHP reservoir radiator with a proportionally controlled heater. The purpose of the test was to characterize and demonstrate the assembly's ability to control the temperature of the cold plate, which provides a stable thermal environment for the instrument's optical bench. This paper discusses the VCHP Assembly control performance and control authority during the dynamic hot and cold 90-minute orbit cycling test phases.

An IBM Personal Computer (PC) version of the Groove Analysis Program (GAP) was developed to predict the steady state heat transport capability of axially grooved heat pipes for a specified groove geometry and working fluid. In the model, the heat transport capability of an axially grooved heat pipe, usually governed by the capillary limit, is determined by the numerical solution of the governing equation for momentum conservation with the appropriate boundary conditions. This paper discusses the theory behind the development of the GAP model. It also presents many useful capabilities of the model. Furthermore, correlations of flight test performance data using GAP are presented and discussed.

This paper presents the test results and data correlation for the Heat Pipe Performance Flight Experiment which was a Class D middeck experiment flown aboard the Space Shuttle Columbia (STS-52) in October of 1992. Three categories of heat pipe performance were examined: static mode, operation under applied acceleration, and re-wicking capability. Two aluminum/freon axially grooved heat pipes, ten copper/water axially grooved heat pipes, and four fibrous wick copper/water variable conductance heat pipes were tested. Ground and flight test results for the axially grooved heat pipes are discussed and correlated with analytical models. Correlation of flight test data for cryogenic axially grooved oxygen heat pipes and a description of the Groove Analysis Program (GAP) is also presented.

The Capillary Pumped Loop (CPL) Materials Life Cycle Test Facility at the Goddard Space Flight Center (GSFC) will identify the operational parameters controlling the performance of a CPL over an extended period of time. The primary purpose of the facility is to investigate the long-term chemical compatibility between the anhydrous ammonia working fluid and the CPL materials of construction. Chemical reactions occurring within the system may produce non-condensable gases or particulate debris that can lead to a degradation in system performance. Small liquid samples will be drawn from the system at specific time intervals and analyzed to check for the presence of non-condensable gases. Periodic maximum and minimum heat load tests will be performed on the CPL to monitor trends in the overall system performance.