The Development of High-Performance Working Fluids for Spacecraft Thermal Management Systems

"Future spacecraft military electronics will require two-phase thermal management systems to maintain appropriate operating temperatures. Thermal control systems such as heat pipes, pumped loops, heat pumps, etc. are systems being considered for thisapplication. In order for these thermal control systems to be compact and low-mass, new high performance working fluids are desired with suitable thermophysical, environmental, materials compatibility, and hazard properties. Water is a high-performance,safe fluid that is not suitable for spacecraft applications because of its high freezing point. Ammonia is another high-performance fluid that has concerns over its toxicity and handling. Conventional halocarbon refrigerants are safe and compatible withmany materials of construction, but suffer from performance and environmental concerns. Hydrocarbon working fluids are flammable and also have performance penalties. What is needed is a fluid with the performance of water or ammonia, the safety ofhalocarbon refrigerants and water, a low freezing point, and no environmental drawbacks. The fluid must also be cost effective. The payoffs of developing the desired fluid include enhancing the lifetime of spacecraft electronics, minimizing spacecraftsize and mass, and allowing for the thermal control of high-power spacecraft through the use of two-phase thermal management systems. In addition to the spacecraft applications, other military ap