Loop Heat Pipe Technology With Flexible Lines Design And Development. DESTINY⁺ LHP Development Case Study

Loop Heat Pipes (LHP) are one of the most extended components used for thermal control subsystems in space technology, among other passive solutions (e.g., Heat Pipes, thermal straps) or active solutions (e.g., Mechanically Pumped Fluid Loop). One of the drivers in the design of an LHP is the transport lines definition and dimensioning. Transport lines are flexible or rigid elements that join the different components of the loop. Flexibility in the transport lines might be required for several purposes, such as system integration, deployable systems or mechanical decoupling of fixed interfaces and movable parts. The introduction of flexible lines can be addressed by metallic flexible hose designs or by rigid pipes in a certain configuration to allow flexibility. This paper presents the evolution of the development strategy for the LHPs for Destiny+ Thermal Control System due to the challenges encountered when introducing flexible hoses in the design at performance and validation level. A trade-off related to the advantages and limitations of the different potential solutions is reviewed, focusing on the mechanical and thermal implications of the design parameters for the flexible line sections. Furthermore, the development approach under severe fatigue conditions for a design considering rigid lines in flexible configuration is presented, including the validation at mechanical level and the results of the thermal test campaign.