A 10W @ 20K Cooler for Spaceport of Cryogenic Fluids

For the spaceport of cryogenic fluids (e.g., liquid hydrogen) NASA requires cryocoolers that can provide more than 10W of cooling at 20K. We propose to develop a two-stage 20K pulse tube cooler (PTC) to fulfill this need. PTCs embody the high efficiency, high reliability, and low vibration required in space missions. The absence of cold moving parts increases their reliability, thus making PTCs the ultimate cryocooler for space applications. Using a long-life linear compressor to drive the PTC bolsters its reliability. Single-stage PTCs, driven by linear compressors and having porous stainless steel regenerators, have achieved no-load temperatures below 50K. To provide cooling at still lower temperatures, PTCs will require additional stages with regenerators made from novel materials having high heat capacity at the lower temperatures. The proposed innovation involves development of a two-stage PTC, driven by a linear compressor, that achieves temperatures below 20K. The first stage (300K to 60K) will have a traditional stainless steel regenerator matrix. The matrix for the second stage regenerator (60K to 20K) will be made from a newly-patented material having a heat capacity in excess of all other known materials, including lead (Pb), over a wide range of low temperatures (85K down to 20K).