Technical Abstract (Limit 2000 characters, approximately 200 words):
Existing space qualified cryocoolers are typically Stirling and pulse-tube type cryocoolers that achieve compactness and reliability by adopting mechanically simple cold head configurations, at the expense of thermodynamic efficiency. Large terrestrial cryogenic refrigerators achieve higher thermodynamic efficiencies but use mechanically complex designs that are not feasible at a small scale. The ideal space cryocooler would have the efficiency of a large terrestrial machines, but with the compactness and reliability of a pulse-tube or Stirling cryocooler.
A cryocooler concept approaching this ideal has been investigated and achieves compactness and reliability by using microelectronics to enable complex valve timing in a mechanically simple and efficient design. It is based upon a modification of the Collins cycle. Key component technologies include floating piston expanders and electromagnetic Smart Valves have been demonstrated in a prototype low-temperature cryocooler stage.
Cryocoolers are an enabling technology for space missions viewing in the infrared, gamma-ray and x-ray spectrums, providing the necessary environment for low temperature detectors and sensors, as well as for telescopes and instrument optics on infrared observatories. Detectors and sensors provide better imaging performance at lower temperature. The Mid Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope includes a 7K cryocooler for detector cooling. The next generation of space telescopes include the LYNX (X-ray surveyor) and Origins Space Telescope (far IR surveyor) that are planned for launch in 2030.
A 4K 4-stage pulse tube cryocooler from Lockheed Martin is the current baseline design for the LYNX mission, with expected electrical power is 10,000 W per Watt of cooling at 4K. The proposed Modified Collins Cycle is expected to reduce the power draw for 4K cooling to about 2,000 W per Watt of cooling