Passive cryogenic devices and thermal management

The state of the art in the design and fabrication of cryogenic heat pipes is reviewed. Cryogenic heat pipe technology is as advanced as it is for ambient-temperature heat pipes. Those fluids available and showing promise as heat pipe working fluids have been successfully tried. While testing cryogenic heat pipes requires more sophistication than testing an ambient-temperature heat pipe, no serious difficulties have been experienced or reported by other workers in the field. It is noted that, as longer missions and increased cryogenic loads become a reality, thermal management with heat pipes are the only viable option. Potential thermal management with cryogenic heat pipes has been demonstrated experimentally for a variety of potential applications: transport from heat source (IR sensor) to passive radiator, passive two-stage radiator with heat pipes used to isothermalize the radiator surface, and heat pipe switches used to thermally switch between the IR sensor and two redundant cryogenic coolers