Performance, Reliability, and Life of Hydride Compressor Components for 10 to 30 K Sorption Cryocoolers

Abstract

Compressor reliability physics investigations are an important element of an ongoing research effort to understand and confirm the performance and reliability of hydride sorption cryocoolers for low-vibration, long-life 10 to 30 K spacecraft applications. The detailed understanding of important failure mechanisms governing hydride refrigerator life is enabling identification of operating constraints, design enhancements, and other means of eliminating failure mechanisms, as well as aiding detailed definition of effective techniques for fabrication, assembly, and handling. Investigations underway with candidate hydride materials (e.g. LaNi_5-ySn_y and ZrNi) include: (1) characterization of hydride chemical and metallurgical composition, isotherms, kinetics, phase purity, lattice parameters, disproportionation mechanisms, and thermal conductivity; (2) study and definition of hydride manufacturing, annealing and handling procedures; (3) characterization of long-term hydride stability, degradation, compaction and containment using specially fabricated compressors used to precisely measure the transient pressure response to programmed temperature cycling; (4) demonstration of the fast sorption capability needed for quick-cooldown using a engineering model compressor with an integral phase-change material heat sink and (5) demonstration of 2 stage compression between 1 torr and 11 MPa and; (6) validation of current transient analysis models. In addition, characterization of enhanced performance refrigerator components is currently underway. The test results described are entirely consistent with achieving > 10 year cryocooler life.