Performance of Liquid Metal Heat Pipes During a Space Shuttle Flight

This study investigated liquid metal heat pipe performance in a microgravity environment. Three stainless-steel/potassium heat pipes were flown on Space Shuttle mission STS-77 in May 1996. The objectives of the experiment were to characterize the frozen startup and restart transients, to compare the flight and ground test data to establish a performance baseline for analytical model validation, and to assess the three different heat pipe designs. Microgravity operation did not adversely impact the startup or restart behavior of the heat pipes. The heat pipes operated within the predicted performance envelopes. The three designs had distinct startup characteristics, yet were similar in steady-state performance. These results will serve as a benchmark for further liquid metal heat pipe studies and space system applications.