This STTR Phase I project will develop 3D printed liquid hydrogen fuel tanks for unmanned aerial vehicles (UAVs). UAVs are currently powered by long endurance low reliability gasoline engines, or short endurance highly reliable electric propulsion. Hydrogen fuel cells offer the potential for long endurance highly reliable propulsion if the proper hydrogen storage method is used. Through the innovative hydrogen storage system developed by this project, fuel cell electric vehicles can advance national health and welfare through reduction of emissions, and promotion of energy independence both on the ground and in the air. This project will develop a new class of liquid hydrogen storage tanks for electric UAVs that will increase the reliability and performance of surveillance platforms in the armed forces, reducing risk to American service personnel while they secure the defense of our nation. The same electric platforms will promote the national welfare by enabling the inspection of key energy and transportation infrastructure and serving as intelligence and communications platforms for first responders during natural disasters. In addition, the key technology developed in this project will expand the utility of additive manufacturing by demonstrating the capabilities and performance of engineered plastics in cryogenic (< -238°F) environments. Such cryogenic rated 3D printed polymer parts have wide ranging impacts, including cost reduction, across cryogenic dependent technology areas from medical devices and spacecraft to drug and food processing.
Additively manufactured polymers have never been used in cryogenic applications until now. The correct selection of polymer blend, testing and selection of a lightweight impermeable membrane, and thermal characterization of novel insulation materials are critical to project success. Since most cryogenic research, such as -423°F permeation of hydrogen through polymers, has not been studied since the 1960s, extensive cryogenic engineering and testing experience is required to apply modern materials and manufacturing methods to the project. The objectives of this project will fill knowledge gaps by testing metallized polymer films for hydrogen permeability, as well as manufacturing methods to cost effectively apply it to insulation panels or tank walls. While prior research has identified a polymer blend that is robust to cryogenic thermal cycling, the possibility of microcracking has not yet been thoroughly addressed and will be evaluated in this project. Novel insulation materials never before used in commercial cryogenic applications will be thermally characterized and integrated into the prototype tank. This project will conclude by completing a liquid hydrogen fuel fill and measuring the mass boil-off rate to test computational fluid dynamic modeled performance.
