Description: Under this Phase II SBIR project we will build and test a stirling-cycle cryocooler and coolant circulating subsystem for use with broad area cooling (BAC) systems to deliver reduced or zero boil-off propellant storage. We will also refine the design of an innovative linear-reciprocating cold-circulator that resides at the same temperature as the BAC coolant, although we will not have the resources to build this component in Phase II. Compared to conventional reverse turbo-brayton cycle cooling technology our stirling-cycle technology offers higher cooling efficiency and requires no bulky recuperator component. Our double-acting stirling cycle configuration combines a linear motor with a moving piston/regenerator assembly into a self-contained module. A number of such modules can be connected together into several possible cryocooler layouts to scale heat lift capacity, achieve system redundancy and provide flexible integration with the BAC coolant loop. This modular approach provides the system designer with packaging options not available with conventional stirling cryocoolers.

Benefits: Space-based Cryocooling - The cryocooler we will build can be used to produce cooling in the temperature range of 75 - 120 K. Lower operating temperatures are possible via staging. Potential applications include direct cooling of space sensors, vapor re-liquefaction for zero boil-off fluid storage or cooling superconducting magnetic bearings in support of flywheel energy storage systems. Space-based Refrigeration and Compression - The core cryocooler and linear motor technology could be applied to build higher-temperature Stirling coolers for in-space scientific experimentation or biological material preservation. The same enabling technology could be used to build linear compressors for refrigerant-based cooling or other working gas compression or fluid pumping.

Cryocooling - The cryocooler could be used to cool high-temperature superconducting magnetic bearings in industrial spindles and motors. The ability to cool a central load and reject heat at the periphery is ideal for zero boil-off re-condensation of liquid nitrogen, volatile fuels and other substances. Refrigeration and Gas Compression - The core hydrodynamic bearing technology could be applied to linear free-piston compressors for domestic refrigeration. The Department of Energy Office recently issued a new report which prioritized accelerating the commercialization of high-efficiency appliance technologies. This Roadmap ranked the development of advanced compressor technologies for refrigerators and freezers as having the highest overall importance and potential impact.