Description: CU Aerospace (CUA) and team partner Lockheed Martin Space Systems Company (LMSSC) propose to develop a low-cost lightweight recuperative heat exchanger for High Power/High Efficiency cryocoolers, in support of Cryogenic Fluid Management for In-Space Transportation. Brayton cryocoolers are well suited for high cooling power space applications, especially those such as cryogenic propellant management that benefit from broad area cooling. However, Brayton recuperators are large, heavy and expensive. CUA and LMSSC have been developing a robust ultra-compact recuperative heat exchanger for Joule-Thomson (JT) cryocoolers using CUA�s sacrificial fiber technology (VascTech). This technology relies on weaving warp sacrificial fibers with weft copper wires to make a 3D structure with excellent counterflow heat exchange, but low parasitic heat conductance. The proposed microcapillary recuperative heat exchanger (MRHX) requires much larger gas flow (for >150 W cooling at 90 K) than the JT recuperator, and the focus of this proposed work will be modifying and scaling up the heat exchanger for Brayton applications. This new recuperator material will reduce the mass and cost of Brayton coolers while offering improved thermal performance.

Benefits: The microcapillary recuperative heat exchanger (MRHX) supports the NASA Roadmap for In-Space Transportation, Cryogenic Fluid Management. A lighter, low cost, more robust Brayton cryocooler has numerous space applications, and may be able to replace Stirling and pulse tube coolers used in many instruments, eliminating the risk of exported vibration from the cryocooler and offering broad area cooling which is difficult to achieve with Stirling coolers. Many highly sensitive instruments and optics require precise thermal stability and uniformity. Most space cryocoolers provide cooling at a point source, and must cool the instrument or optics conductively. This can lead to thermal gradients within large structures, and can also lead to temperature gradients between the cryocooler and instrument which require the cryocooler to operate at a lower temperature (and consequently require more electrical input power). Thermal gradients within cryogenic storage tanks are a concern for long life cryogenic propellant storage. Developing this MRHX allows one to retain the remote cooling functionality of the Brayton cooler but at lower mass and cost.

We regard the MRHX as having high potential for infusion to external customers as the hardware geometry and manufacturing process can be adapted for a wide variety of uses. The recuperative heat exchanger can also be used in Joule-Thomson coolers, such as the sorption coolers used on Herschel, Planck, Astro-E and Astro-H. Furthermore, there are many terrestrial uses for inexpensive counterflow heat exchangers, beyond cryogenic applications such as air liquefaction and separation. This recuperator geometry also offers potentially lower cost and higher performance for commercial cryogenic applications such as air liquefaction and separation using Hampson-Linde coolers.