Fabrication and testing of heat pipes for a heat-pipe-cooled leading edge

Abstract

Refractory-composite/heat-pipe-cooled wing and tail leading edges are being considered for use on hypersonic vehicles to limit maximum temperatures to values below material reuse limits and to eliminate the need to actively cool the leading edges. The development of a refractorycomposite/heat-pipe-cooled leading edge has evolved from the design stage to the fabrication of full-size, leading-edge-shaped heat pipes. A three-foot-long, D-shaped, molybdenum-rhenium heat pipe with a lithium working fluid was fabricated and tested at an operating temperature of 2460°F (~1350°C) to verify the individual heat-pipe design. Following the fabrication of this heat pipe, three additional straight heat pipes were fabricated and embedded in carbon/carbon with a 0.005-in-thick layer of Grafoil® placed between the curved portion of the heat pipe and the carbon/carbon. Finally, a single leading-edge-shaped (J-tube) heat pipe was fabricated. The wick for the J-tube heat pipe, made of 400x400 Mo-Re screen, was fabricated with wedges cut out on the inside surface to conform to the 0.5-inleading-edge radius. Due to lack of funding, testing on the heat pipes embedded in carbon/carbon and the J-tube heat pipe has not been completed.