Flight test performance of a loop heat pipe—Focus on a long steady state with no apparent subcooling

The loop heat pipe is one of the prime enabling technologies in the ongoing development of high powered satellites. The ability to understand and model the LHP accurately has therefore become critical to the design of these spacecraft. This paper presents the modeling methodologies employed and the correlation of the model predictions with flight test results obtained on space shuttle flight STS-87. An interesting result of the flight experiment is that during one long phase of the flight experiment the LHP, for the parameters studied, successfully operated with no apparent subcooling, once thought to be a requirement for LHP function. An energy balance on the compensation chamber is presented as a means for explaining the absence of subcooling during the 49-hour steady state. The flight test data was obtained from a Hitchhiker experiment flown aboard STS-87 in November, 1997. The accuracy of the steady state LHP modeling has been verified by correlation of ground (Parker, et al., 1998) and flight data, the results of which are documented here.