Small Business/SBIR

Innovative Cryogenic Equipment More Efficient

A MICROGRAVITY EXPERIMENT THAT FLEW ON STS-95 in October 1998 has led to the development of a new cryogenic heat transport system with commercial and space applications in cooling electronics, sensors and fluids. Cullimore and Ring Technologies of Littleton, Colorado, and Swales and Associates of Beltsville, Maryland, developed the Cryo HTS through Small Business Innovation Research (SBIR) contracts from NASA's Goddard Space Flight Center. The Air Force Research Laboratory provided additional funding.

Operating without moving parts, the system uses a two-phase fluid Cryogenic Capillary Pumped Loop (CCPL), similar in concept to that found in a residential heat pump, to more efficiently transport energy at a fraction of the weight of highly conductive solid material such as copper. It isolates vibrations and operates in both ground and microgravity environments. The system removes heat from cryogenic components through evaporation and transports the resulting vapor to a cryocooler, where it is condensed.

Space cryocoolers are miniature refrigerators designed to cool sensitive spacecraft components to cryogenic temperatures below 100 degrees Kelvin (–280 degrees Fahrenheit). Cryogenic temperatures are necessary to operate many modern devices, such as infrared detectors and focal planes, solid-state gamma-ray detectors and a number of emerging superconducting technologies.

Space thermal control problems require a range of thermal control components. In certain types of spacecraft, such as those used in Earth-observing applications, infrared detectors and optics need to be very cold while co-existing with much warmer components. Many NASA near-term, future and advanced space instruments and programs depend on the successful use of long-life, low-vibration space cryocoolers to meet their scientific objectives.

When not operating, the CCPL provides excellent thermal isolation and can be used as an effective and low-cost cryogenic thermal switch. With inherent diode action, a CCPL-based thermal link can be turned on or off. This differs from routinely used flexible conductive links that, by definition, are always turned on.

The STS-95 experiment evaluated cryogenic thermal control components under the effects of a microgravity environment. The small size, low weight, high conductance, inherent flexibility and diode action of the Cryo HTS greatly facilitate the integration of multiple and all types of cryogenic components into a single cooling source for a component, as well as the ability to span joints requiring extreme flexibility.

An expansion of an extensive heritage of room temperature two-phase loops, the Cryo HTS offers performance benefits that are not currently within the reach of traditional cryogenic heat pipes and thermal switches. These efforts have demonstrated and matured the Cryo HTS technology, introducing a new, versatile and exciting integration option for the design of future cryogenic systems. The ultimate goal of any spacecraft thermal designer is to reliably solve complex spacecraft thermal design problems with minimal power, weight and cost output.

Other specific advantages with respect to cryo-cooler integration include fewer restrictions on test orientations than heat pipes, tighter temperature control at the heat source, and easier integration and greater conductance using components that can be integrally bonded. Potential spinoffs from this development include the miniaturization of room temperature devices and the extension to both colder (20 to 30 degrees Kelvin) and intermediate (100 to 200 degrees Kelvin) temperature regimes.

STS-95's testing of Cryo HTS was conducted under NASA's Hitchhiker project and developed and operated by Goddard's Small Payloads project. The Small Payloads project provides quick results and a low-cost way to send small payloads into orbit on the Space Shuttle for business and industry customers whose space activity requires power, data or command services.

For more information, please contact Jentung Ku at Goddard Space Flight Center.
Call: 301/286-3130, E-mail: jentung.ku@gsfc.nasa.gov
Or contact Jane Baumann or Brent Cullimore at Cullimore and Ring Technologies.
Call: 303/971-0292.
Or contact Ed Kroliczek at Swales and Associates.
Call: 301/902-4395.
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