Issues with LHP Testing in 1-g Environment

摘要

Verification testing of Loop Heat Pipes on the ground was performed almost exclusively with the capillary pump/compensation chamber being flat or horizontal. In this configuration, the test did not validate the "secondary wick" capability for space operation due to favorable gravitational effects. A "successful" ground test program might, in fact, conceal potential flight risks involving the secondary wick. On the other hand, certain 0-g liquid-management features of the internal wick structure were simply impossible to demonstrate in 1-g. So, like everything else in the space business, some level of risk had to be accepted providing that (i) the risk was understood and (ii) action was taken to mitigate it. This paper is an attempt to bring out the importance of the wick functions for 0-g operation and difficulties to verify them in 1-g testing. Finally, although it is not meant to provide remedies for the subject issues, the paper also offers lessons learned from the authors' previous experience and recommendations to carry out the verification process to the fullest extent possible.