In-orbit cryogenic propellant transfer is a key enabling technology for future long duration space exploration missions. Tank chilldown will be one of the primary challenges to be overcome to achieve refueling in space. It is envisioned that tank cooling will be facilitated by the use of spray injection nozzles, achieving high heat removal rates through phase change. Tank filling protocols such as charge-vent-hold and vented-chill-non-vented-fill are being investigated to improve the probability of successful refueling while minimizing propellant boil-off. In this collaborative effort between the Univ of Connecticut and CRAFT Tech, experimental visualization and diagnostic measurements of a sub-scale tank are being used to understand the complex heat-transfer interaction modes between the spray and the ullage as well as the spray and the tank walls. Validation datasets are being collected and used in the development of a specialized spray cooling models within a comprehensive high-fidelity Multiphysics simulation framework. The simulation framework can be used for design support, analyzing tank filling protocols and prediction of chilldown times and propellant loss as part of the refueling process in a microgravity environment.
Cryogenic propellant storage and transfer is critical to nearly all NASA’s future human exploration missions such as the Moon Gateway Mission and the more distant Mars Exploration Campaign. Successful propellant transfer in space is the cornerstone of NASA’s Reduced Gravity Cryogenic Transfer program and the technology in this program will impact it by improving our understanding of the physical processes, proving validation datasets and high-fidelity predictive tools.
The technology will be valuable in decarbonization efforts and the transition to a hydrogen economy since storage and transfer of hydrogen remains a significant challenge. The technology can also be used for design of cryogenic spray nozzles for advanced propulsion concepts, improving life support systems in space as well as cryogenic preservation techniques in medical applications.