Description: Future astrophysics missions require efficient, low temperature cryocoolers to cool advanced instruments or to serve as the upper-stage cooler for sub-Kelvin refrigerators. Potential astrophysics missions include Lynx, Origins Space Telescope, and the Superconducting Gravity Gradiometer. Cooling loads for these missions are 50 to 300 mW at temperatures of 4 to 10 K, with additional loads at higher temperatures for cooling shields and other subsystems. Due to low jitter requirements, a cryocooler with very low vibration is needed for many missions. Turbo-Brayton cryocoolers have space heritage and are ideal for these missions due to negligible vibration emittance and high efficiency at low temperatures. Technologies have been demonstrated or are under development for refrigeration loads in the range of 200 mW to 500 mW at 4 to 10 K, respectively. Many future missions have lower refrigeration requirements and require commensurably lower input power. Further miniaturization is needed for the cold turbine to provide high cryocooler efficiency and low input power when loads are reduced to 50 to 150 mW. On the proposed program, Creare plans to advance recent developments in gas bearings and miniature permanent magnet alternators to a smaller turbine capacity than attempted to date. On the Phase I project, we will perform analyses and fabrication trials to demonstrate feasibility of a turbine optimized for 50 to 150 mW at 4 to 10 K. On the Phase II project, we will build and demonstrate the turbine in a cryocooler.

Benefits: The successful completion of this program will result in an extremely efficient, low temperature, low capacity cryocooler with negligible vibration. This type of cryocooler is ideal as the upper-stage cryocooler or primary cooler for cooling advanced, low-temperature space instruments. Potential NASA missions include the Lynx, Origins Space Telescope, and the Superconducting Gravity Gradiometer.

The military market is for cooling multi-spectral and hyperspectral imaging systems on space‑based observation, surveillance, and missile defense systems and low temperature superconducting electronics. Commercial applications include cooling for communication satellites; superconducting instruments, digital filters, and magnets; low temperature gas‑separation systems; hypercomputers; and SQUIDs.