On-orbit cryogenic fluid transfer research at NASA Lewis Research Center

Abstract

Cryogenic fluid transfer operations in the low-gravity environment of Earth orbit are necessary for many NASA mission concepts. Fluid transfer brings several benefits to the performance of space missions. Spacecraft already on orbit can be resupplied with cryogenic propellants, coolant fluids and other liquids. Lighter weight spacecraft can be built, since as they are launched dry and supplied on orbit they are not required to support the weight of cryogens during the 3–6 g launch environment. The filling of cryogenic tanks in low gravity poses an operational challenge. Among the difficulties encountered are vapour generation due to the energy stored in the tank walls and the uncertainty of liquid and vapour distributions in a tank in a low-gravity environment. Increased support for technological research in recent years has enabled NASA Lewis Research Center (LeRC) personnel to make significant advances in the state of the art of cryogenic fluid transfer operations via the no-vent fill method. This paper presents a summary of the results obtained to date in the ongoing programme at LeRC. The LeRC programme has two purposes, emphasizing an extensive ground test programme which is augmented by the development of analytical models for the no-vent fill transfer operation processes. Additionally, planning for the future development of this technology is continuing. This ongoing research effort should, in the near future, permit the design of space systems and spacecraft that benefit from the reusability and weight savings accrued through the use of cryogenic fluid transfer operations in a low-gravity environment.