Foster-Miller is developing a 5 x 50 x 100 mm micropump working with approximately 4 gm of cryogen for cooling satellite-based infrared detectors.  The two-phase heat transport loop system provides remote cryogenic cooling, since direct coupling to the cryocooler would produce unacceptable vibrations. The micro-pumped loop provides an alternative to cryogenic heat pipes and capillary pumped loops that are difficult to start and operate. The micro-pumped loop is also capable of operating across a space-based two-axis gimbal, an application that cannot be accomplished with capillary-driven devices.

A millimeter sized pump assembly is employed to transport cryogenic fluid (initially liquid nitrogen) between an evaporator (attached to the infrared detector array) and a condenser (in contact with a cryocooler). The micro-pump contains a small cavity and valves micro-machined out of silicon, with an actuator that compresses the cavity to make it pump.  This approach yields a system with minimal hardware/mass, and small charge of working fluid. The arrangement makes for easy routing of tubing and includes flexible coils for applications such as a two-axis gimbal. The piping arrangement reduces surface area making parasitic heat gain as small as possible.

No liquid accumulator or capillary wicking is needed for operation, significantly lowering the cold plate mass. The small cryogen charge (~4 gm), results in low system pressure during launch and prior to deployment and start-up. A cryogen storage container of 1/2 in. ID and 4 in. long is adequate to store the charge at ambient temperature and 325 psia.

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