Next-generation heat-pipe radiator technologies are being developed at the NASA Glenn Research Center to provide advancements in heat-rejection systems for space power and propulsion systems. All spacecraft power and propulsion systems require their waste heat to be rejected to space in order to function at their desired design conditions. The thermal efficiency of these heat-rejection systems, balanced with structural requirements, directly affect the total mass of the system.
In testing space radiators for nuclear power systems, it was found that current technology had significant thermal losses due to the long chains of thermal resistance, stemming from multiple materials, their respective bonds, and physical geometries. Tubular heat pipes connected to flat fins, typically made of different materials, have traditionally been thought of as the best way to drive down radiator system mass. Dissimilar materials inherently had coefficient of thermal expansion mismatches, which created complex designs and additional mass.
Combining structural and thermal components of a heat-pipe radiator into a unique design may produce advantages to both heat transfer characteristics and structural integrity. The Sandwich Core Heat Pipe (SCHP) technology being developed at the Glenn Research Center addresses this by using thin titanium sheets in a unique structural configuration to make a highly efficient rectangular heat-pipe array that can be used as a thermal-control radiator. The concept is the first of its kind to combine heat pipes, radiator, and structural components into one system using a single material of construction. Although numerous concepts are under development, the basic design allows the internal sandwich core structure to double as the heat pipe vapor space, allowing the radiator facesheet to reach near-vapor temperatures without the losses associated with a conduction fin, common to current state-of-the-art technology. This “no fin” feature reduces the overall temperature drop associated with current heat-pipe radiator designs and ultimately reduces unwanted mass through improved thermal efficiency. Additionally, the configuration of the internal core using thin metal construction provides rigidity as well as a reduction in mass over current technologies. The combination of the reduced mass and increased thermal efficiency are appealing to power and propulsion designers needing improved performance.
This work was done by Marc Gibson, James Sanzi, and Ivan Locci of Glenn Research Center.
Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-18900-1.