West Coast Solutions (WCS) and the Georgia Institute of Technology (GT) propose development of a Miniature 2-Stage Hybrid (M2H) Cryocooler in response to Topic S16.07, Cryogenic Systems for Sensors and Detectors. Extending from our prior NASA and ongoing Missile Defense Agency (MDA) SmallSat Stirling cryocooler developments, we propose to add a second stage to address the topic requirements for a highly-miniaturized, two-stage cryocooler. In Phase I we will mature the concept design of a Stirling/pulse tube hybrid expander that achieves extreme miniaturization by leveraging low impedance regenerator designs in combination with efficient linear motors operating at high frequency relative to other 20K systems. Based on initial modeling results, the WCS M2H Cryocooler will weigh less than 1.75 kg while simultaneously providing a minimum of 100 milliwatts of net refrigeration at 20K and 2 Watts of refrigeration at 100K. The projected input power is ~40 WAC while operating in a 300K heat rejection environment, which translates to 13.8% of Carnot efficiency. Operation with this level of efficiency at a temperature as low as 20K is unique in the realm of linear cryocoolers, and to our knowledge there are no comparable coolers available or even in development.

The proposed effort is in response to NASA's stated need for a compact, high efficiency, low vibration cryocooler capable of providing two stages of cooling at 20 K (detector) and 80 to 120 K (local oscillator / optics) for high resolution spectrometers. With the cold tip achieving temperatures as low as 20K, benefitting detector technology also well enveloped the most commonly used HgCdTe LWIR detectors as well as other longwave detector technology, such as the quantum well infrared photodetector (QWIP).

The most probably near term non-NASA applications would be for the Department of Defense (DoD) using similar detector technology for their specific missions, such as Intelligence, Surveillance, and Reconnaissance (ISR) from space, as well as potentially Ballistic Missile Defense (BMD).