Development of a flexible advanced loop heat pipe for across-gimbal cryocooling

To provide cryocooling across a gimbaled joint still remains a difficult challenge for spacecraft engineers. Gimbaled cryogenic infrared payloads have very difficult-to-meet requirements for 2-axis motion and low torque. Thus the difficulty of making a cryogenic thermal connection across a gimbaled joint cannot be overstated. Because of the cryogenic nature of the connection, thermal joint flexibility, durability, reliability, material compatibility, differential expansion/contraction, and parasitic heat loss, are all complex technical concerns. Thus two primary issues of the proposed across-gimbal passive cryocooling system similar to management of heat parasitics and flexible/durable thermal connection between heat sources (infrared sensors/detectors) and heat sinks (cryocooler coldfingers) - are the main focus of the current development effort. A cryogenic Advanced Loop Heat Pipe proof-of-concept test loop that was developed in Phase I demonstrated a heat transport capability of 50W-m (20W over a distance of 2.5m) in 3/32"O.D. stainless steel lines. But more importantly, the test loop started up and operated reliably even in a 300K environment. In the follow-on Phase 11, the research focus shifted to the development and demonstration of a low-torque durable flexure mechanism for a 2-axis gimbal.