Floating Piston Expander Development for a Small-Scale Collins Type 10 K Cryocooler for Space Applications

Future spacecraft cooling and sensing systems will require advanced multi-stage cryocoolers capable of providing continuous cooling at multiple temperature levels ranging from 10 K to 95 K. Stirling and pulse-tube cryocoolers have achieved compactness and reliability by adopting mechanically simple cold head configurations at the expense of thermodynamic efficiency. Large-scale terrestrial cryogenic refrigerators achieve much higher efficiencies by employing complex designs, but their high efficiency is not retained at the small scale required for spacecraft cryogenic cooling. AMTI, in collaboration with MIT, is developing a multi-stage 10 K cryocooler that applies modern microelectronic sophistication to achieve high efficiency in a reliable, compact design. The cryocooler is based upon a novel modification of the Collins cycle, a cycle commonly used in many high-efficiency terrestrial cryogenic machines. Innovations of the design include floating piston expanders and electro-magnetic smart valves, which eliminate the need for mechanical linkages and reduce the input power, size, and weight of the cryocooler in an affordable modular design. This paper will present the design of the first generation prototype, the results of development testing, and the direction of future development efforts.