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The CPL technology has been under development for the last 15 years. Many technical and manufacturing issues have been worked out. However the deprimes of capillary pumps have remained the most difficult problem to solve. The Advanced CPL (A-CPL) design concept was proposed in an effort to make the capillary pumps more tolerant to both vapor and noncondensible gases. A test loop was constructed to demonstrate the operational principles of the A-CPL at room temperature. Freon 134a was chosen as the working fluid so that Teflon tubing could be used as the loop transport lines for flow visualization purposes.

The thermal control subsystem design, analysis, and test-verification that made possible the successful Clementine moon-mapping mission was indeed formidable in many respects, with very high ratios of requirements-to-available resources and performance-to-cost/mass, exacerbated by an unyielding tight schedule. Environments, requirements, program restrictions, design highlights, and lessons learned are presented. Emphasis is given to the sensor-bench payload and its unusual thermal components: three types of heat pipes (variable conductance, fixed conductance, and diode), a thermal-energy-storage beryllium block, and a multitude of flexible conducting straps. A description of the thermal design verification test emphasizes its unconventionally and lessons learned. Despite adverse schedule and cost-cutting effects on test hardware, planning, and execution, test data made possible thermal model refinements and important hardware design changes.