Multistage, High Capacity 35 Kelvin Cryogenic Cooling

"The cryogenic refrigeration requirements for many space-based infrared (IR) sensor systems are best met with a multistage cryocooler to simultaneously provide cooling at two distinct temperature levels. The requirement to cool a focal plane array to somevery low operating temperature while simultaneously cooling the optical bench to some higher, though still cryogenic temperature is a typical example of a system need optimally met by a multistage cryocooler. Stirling-cycle mechanical cryocoolers havedemonstrated the broadest applicability to date for space IR sensors in terms of performance, reliability, and packaging. The complexity of the multistage thermodynamic cycles and the challenge of comparing differently-sized cryocoolers with differentoperating temperatures has to date precluded a consensus agreement various approaches. Therefore, a program is proposed to systematically compare the competing configurations. Phase I will focus on developing mathematical models to determinethermodynamic losses through calculation of the cyclic entropy generation rate at both the component and system level comparing various cryocooler configurations. The results of Phase I will be used to guide the experimental phase of the program, PhaseII, in which the models will be correlated and the hypotheses tested. The correlated models will guide the commercialization of the optimum multistage cryocooler. The models and optimization techniques