Advanced Manufacturing of Net-Shape Leading Edge Geometries for Hypersonic Flight
James Cahill | 19-DR-002
The speed and range of hypersonic craft are limited by current material systems. Since flying at high Mach numbers generates heat flux an order of magnitude greater than the limit of radiative cooling for even the most advanced materials, an additional cooling modality is required for sustained high-speed flight. One way to semi-passively cool a system is by using the latent energy consumed by endothermic phase changes, much like the human body cools itself by perspiring. In a hypersonic vehicle, this transpirational cooling can be achieved through the use of a sacrificial phase - the transpirant - designed to remove heat from the system by vaporizing at the vehicle's operating temperature. Although transpiration systems most commonly use water or an inert gas as the transpirant, the cooling potential for this process can be significantly increased by utilizing an initially solid metal transpirant to take advantage of the latent heat of both melting and vaporization.
A hierarchical, architected vasculature fabricated with advanced manufacturing allows the system's "metal sweat" to flow towards the external surfaces of the leading edge, powered only by capillary force and the pressure induced by volumetric changes due to melting and thermal expansion. The vasculature is contained inside of an ultrahigh-temperature ceramic shell, which is fabricated using advanced manufacturing and then sintered before being infiltrated with the molten metal transpirant. High-temperature testing using either combustion or microwave torch systems demonstrates that the melting and vaporization of the metal transpirant results in a substantially reduced bulk temperature compared to a monolithic ceramic structure. These coupon-scale results validate the metal transpiration cooling concept and open up the possibility of incorporating this concept into full-scale leading edge designs.
The breadth of expertise in materials science, advanced manufacturing and high-performance computing provide strong support for LLNL's emerging hypersonics thrust area. This research has demonstrated novel manufacturing techniques, developed new testing and characterization techniques, and fostered new external relationships in support of this mission. Engagement with DOE sites such as Sandia National Laboratory and DoD sites such as the Air Force Research Laboratory have helped promote LLNL's capabilities and ability to have substantial impact in the field of hypersonics. The technical results and new staff hired as a result of this project have led to two new internal and one externally-funded project.
Publications, Presentations, and Patents
James Cahill, "High-Temperature Transpiration Cooling." Presentation, Hypersonic Technology & Systems Conference, North Logan, UT. October 24-27, 2022.
Cahill, James T. and Qi Rong (Bruce) Yang. "Shape-Stable Structures with Ablative Cooling" U.S. Patent Application 17/878,808, filed August 1, 2022.
Swetha Chandrasekaran, "Direct Ink Writing of Ultra-High Temperature Ceramics." Presentation, Ultra-High Temperature Ceramics: Materials For Extreme Environment Applications V Conference, Snowbird, UT. June 5-8 2022.
Cahill, James T., Swetha Chandrasekaran, Wyatt L. Du Frane, Joshua D. Kuntz, Richard L. Landingham, Ryan Lu, Christopher M. Spadaccini, Amy Wat, Seth E. Watts, and Marcus A. Worsley. "Semi-Passive Cooling using Hierarchical Vasculature." U.S. Patent Application 17/014,756, filed March 2022.
Chandrasekaran, Swetha, James T. Cahill, Wyatt L. Du Frane, Joshua D. Kuntz, Richard L. Landingham, Ryan Lu, and Marcus A. Worsley. "Three-Dimensional Printing of Ceramic Materials." U.S. Patent Application 17/015,403, filed March 2022.
Wat, Amy, C. Gabriella, S. King, James T. Cahill, Joshua D. Kuntz, Wyatt L. Du Frane, Marcus A. Worsley, Logan Bekker, Xiaojie Xu, Yici Sun, Joshua R. DeOtte. "Compliant Suture-Based Joinery" U.S. Patent Application 17/392,686, filed August 2021.
Cahill, James. "AM of UHTCs at LLNL." Presentation, Materials Science and Technology Conference, Columbus, OH. October 17-20, 2021.
Wat, Amy. "Low Toxicity Gelcasting of Zirconium Diboride." Presentation, Hypersonic Technology & Systems Conference, Virtual. October 25-28, 2021.